In the past century, remarkable advancements in healthcare and clinical practices have led to a significant doubling of life expectancy across the globe. However, this increased longevity has brought with it a new set of challenges, primarily centered around the prevalence of age-related diseases and physical deterioration. Aging, being the primary risk factor for various medical ailments including neurodegeneration, cardiovascular diseases, and cancer, has emerged as a critical target for preventive measures aimed at enhancing overall health and well-being [1].

Aging, characterized by its universal, intrinsic, and progressive nature, poses a multifaceted threat to individual health. The processes underlying aging involve a complex interplay of environmental damage, declining endogenous protective mechanisms, and the gradual breakdown of physiological functions due to wear and tear [2]. This intricate web of biological events contributes to the development of age-related pathologies, such as neurodegenerative disorders, which significantly impact societal well-being and healthcare systems worldwide [3].

Recognizing the urgent need to address the growing burden of age-related diseases, researchers have turned their attention towards targeting the hallmarks of aging. These hallmarks encompass various cellular and molecular processes, including genomic instability, telomere attrition, epigenetic alterations, and mitochondrial dysfunction, among others [4]. Strategies aimed at modulating these hallmarks offer promising avenues for interventions designed to mitigate the effects of aging and promote healthy aging.

In recent years, orthomolecular medicine has gained traction as a promising approach to combat aging-related processes. The use of supplementation, particularly with longevity supplements, has shown potential in enhancing healthspan and slowing down the aging process [5]. Human trials exploring the efficacy of regenerative compounds and senolytics have yielded promising results, particularly in addressing age-related skin damage and cognitive decline [6,7,8].

Furthermore, nutraceutical interventions targeting neuroinflammation, oxidative stress, and metabolic disruption have demonstrated encouraging outcomes in preserving cognitive function and promoting longevity [9]. Among these interventions, nicotinamide adenine dinucleotide (NAD+), a critical cofactor involved in various metabolic pathways, has emerged as a key player in the aging process [10].

Studies have consistently shown a decline in NAD+ levels with age, highlighting its potential as a target for age-related pathologies [11]. Administration of NAD+ precursors has shown promise in delaying muscle atrophy, improving neurodegenerative pathologies, and restoring metabolic function in model organisms [12,13,14].

Moreover, synergistic supplementation with NAD+ enhancing compounds has been proposed to further optimize the longevity-promoting effects of NAD+ precursor administration [15].

While repurposed drugs like rapamycin and metformin have shown potential in extending lifespan, their clinical efficacy in humans remains uncertain due to limited data from clinical trials [16]. However, a plethora of potent ingredients and nutraceuticals are under investigation for their ability to modulate the NAD+ axis and offer geroprotection by combating the aging process and promoting overall health.

The pursuit of longevity and healthy aging represents a multifaceted endeavor, requiring a comprehensive understanding of the underlying biological mechanisms and innovative interventions. The role of NAD+ metabolism and its intricate interactions with other longevity-promoting pathways offer promising avenues for future research and therapeutic development. By unraveling the complexities of aging at the molecular level and leveraging emerging technologies, we stand poised to usher in a new era of preventive medicine aimed at enhancing quality of life and extending healthy aging for generations to come.

NAD+, NMN, and NR Metabolism: Central to Cellular Function and Homeostasis

Nicotinamide adenine dinucleotide (NAD+) is a cornerstone molecule in eukaryotic cells, playing dual critical roles in energy transduction and cell signaling. Initially recognized for its essential function in ATP synthesis, the complexity of NAD+ biology has expanded with the discovery of its involvement in various degradation processes. Enzymes such as CD38/CD157/SARM1, ADP-ribosyl transferases (ARTs), poly-ADP polymerases (PARPs), and sirtuins utilize NAD+ to mediate vital cellular activities, including DNA repair, apoptosis, cell survival, lifespan regulation, metabolic adjustments, and responses to inflammation and infection. These processes underscore the significance of NAD+ in maintaining organismal homeostasis.

NAD+ is synthesized from two nucleosides linked by a pyrophosphate group. This structure includes a ribose ring with adenine in one nucleoside and nicotinamide in the other, leading to the formation of adenosine diphosphate ribose (ADPR) and nicotinamide mononucleotide (NMN). The pathways for NAD+ synthesis are versatile, incorporating precursors from tryptophan and vitamin B3 (niacin and nicotinamide), along with intermediates like nicotinamide riboside (NR) and NMN, highlighting the dynamic nature of NAD+ metabolism.

NR and NMN play pivotal roles in the NAD+ metabolic cycle, acting in both the degradation and re-synthesis of NAD+. These cycles of NAD+ metabolism exhibit diversity across different species and biological kingdoms, illustrating the evolutionary adaptation of NAD+ biosynthesis mechanisms. In mammals, NAD+ can be produced through de novo synthesis from tryptophan, the salvage pathway utilizing nicotinamide, or the Preiss-Handler pathway using niacin. Notably, recent discoveries have emphasized the importance of reduced forms of NR and NMN, such as dihydronicotinamide riboside (NRH) and dihydronicotinamide mononucleotide (NMNH), in promoting NAD+ synthesis.

The gut microbiota emerges as a significant factor in NAD+ metabolism, converting NMN into nicotinic acid mononucleotide (NAMN) through deamidation, which then enters the Preiss-Handler pathway for NAD+ synthesis. This microbial pathway contrasts with the direct absorption and metabolism seen in mammalian systems, indicating a complex interplay between host and microbiota in NAD+ homeostasis.

Nicotinamide riboside (NR) enhances NAD+ levels through two distinct pathways: direct salvage pathway absorption or conversion to nicotinamide by BST1, followed by microbial metabolism to nicotinic acid. This dual pathway highlights the intricate mechanisms regulating NAD+ levels and the potential cross-talk between amidated and deamidated metabolic routes.

The metabolic pathways of NAD+, NMN, and NR are critical to understanding how cells maintain their energy balance and respond to physiological stresses. The redundancy and tissue-specific importance of these pathways remain areas of active research, promising to reveal new insights into cellular metabolism and potential therapeutic targets for diseases related to NAD+ dysregulation. This comprehensive overview of NAD+ metabolism not only highlights the complexity of cellular energetics and signaling but also underscores the potential for innovative interventions in metabolic and age-related diseases.

Fig. – Chemical structure and schematic illustration of the beneficial health effects of NAD+ precursors NMN and NR

Fig. – NAD biosynthesis pathways in humans (A) and plants (B). NMN could be uptake through CD73-mediated dephosphorylating to NR, or via a transporter encoded by gene SLC12A8. Arrows dotted indicate a putative pathway. Precursors/Metabolites: KYN: N-formylkynurenine; NMN (nicotinamide mononucleotide); NMNH (dihydronicotinamide mononucleotide); NR (nicotinamide riboside); NRH (dihydronicotinamide riboside); NAR (nicotinic acid riboside); NAM (nicotinamide); NA (nicotinic acid); NAMN (nicotinic acid mononucleotide); NAAD (nicotinic acid adenine dinucleotide), QA (quinolinic acid); TRYP (tryptophan). Enzymes: AK, adenosine kinase; CD73/CD38/CD157, ectoenzimas; IDO, indoleamine 2,3-dioxygenase; NADPPase (NAD pyrophosphatase); NADS (NAD synthase); NAMPT, nicotinamide phosphoribosyltransferase; NAPT (nicotinate phosphoribosyltransferase); NARK (nicotinic acid ribose kinase); NIC (nicotinamidase); NMNAT (nicotinamide/nicotinic acid mononucleotide adenylyltransferase); NRase (nicotinamide riboside nucleosidase); NRD (nicotinamide riboside deaminase); NRK1/2: nicotinamide riboside kinases; NUDase (5′- nucleotidase); PARPs, poli-ADPR polymerases; PNP, purine nucleoside phosphorylase; QPRTase: QA-phosphoribosyltransferase; SIRTs, sirtuins, TDO, tryptophan 2,3-dioxygenase. Image created with https://www.biorender.com/

The Crucial Role of NAD+ in Cellular Metabolism and Homeostasis

Nicotinamide adenine dinucleotide (NAD+) and its reduced form, NADH, play pivotal roles in cellular metabolism, impacting everything from energy production to the regulation of oxidative stress and the maintenance of cellular health. This detailed analysis explores the dynamic balance of NAD+ and NADH within the cell, the critical pathways for NAD+ biosynthesis, and the significant implications of these processes for health and disease.

NAD+, NADH, and Cellular Metabolism

NAD+ acts as a crucial cofactor for oxidoreductases in multiple catabolic processes, facilitating the transfer of electrons in redox reactions. It is essential in glycolysis, the oxidative decarboxylation of pyruvate, the tricarboxylic acid cycle, β-oxidation of fatty acids, and alcohol metabolism. Through these processes, NAD+ enables the harvesting of energy from glucose, amino acids, and fatty acids, converting these substrates into ATP, the energy currency of the cell. Without NAD+, critical metabolic pathways would halt, underscoring its importance in energy metabolism.

Conversely, NADH, the reduced form of NAD+, serves as an electron donor in various biochemical reactions. It plays a vital role in the reduction of pyruvate to lactate, recycling NAD+ to maintain glycolytic flow, and acts as a cofactor in polyunsaturated fatty acid desaturation, supporting alternative mechanisms for regenerating NAD+. The high-energy electrons from NADH are also transferred to the mitochondrial electron transport chain, driving oxidative phosphorylation under aerobic conditions, which is a major source of ATP production in cells.

NADP+, NADPH, and Their Functions

Approximately 10% of cellular NAD+ is phosphorylated to form NADP+, which, like NAD+, serves as a cofactor in critical biosynthetic pathways and stress responses. NADPH, the reduced form of NADP+, is involved in the reductive biosynthesis of fatty acids, cholesterol, and steroids. It also plays a key role in the oxidative stress response, acting in the respiratory burst of neutrophils and in the reduction of glutathione disulfide to glutathione. A newly identified hydride transfer complex (HTC) illustrates the intricate balance of these cofactors, transferring hydride ions from NADH to NADP+, thus linking the catabolic and anabolic states of the cell and highlighting the complexity of cellular redox regulation.

Biosynthesis of NAD+

Maintaining NAD+ homeostasis is critical for cellular health, with cells relying on a balance between biosynthesis and consumption. NAD+ can be synthesized from dietary precursors through various pathways, including the de novo synthesis from tryptophan and the salvage pathway from nicotinamide. The de novo pathway, initiated by the conversion of tryptophan to kynurenine, plays a role in immune response modulation, highlighting the interconnection between metabolism and immune function. Meanwhile, the salvage pathway, primarily responsible for NAD+ production, recycles nicotinamide into NAD+, showcasing the cell’s efficiency in maintaining essential cofactor levels.

Deciphering the Intricacies of NAD+ Homeostasis: Implications for Aging and Disease

Nicotinamide adenine dinucleotide (NAD+) stands as a pivotal coenzyme in metabolic processes, intricately involved in vital pathways governing energy expenditure, stress adaptation, and circadian rhythm maintenance. However, the delicate balance of NAD+ homeostasis is disrupted with advancing age, characterized by a sharp decline in NAD+ levels. This decline is attributed to the activity of CD38, an enzyme responsible for the degradation of NAD+, which undermines the synthesis pathways of NAD+ during the aging process [17].

Understanding the dynamics of NAD+ homeostasis is crucial for comprehending various biological functions. NAD+-consuming enzymes, such as CD38, sirtuins (SIRT), poly [ADP-ribose] polymerase 1 (PARP1), and the neuronal degenerating factor SARM1, emerge as key players in the aging pathology and potential targets for geroprotective interventions [18,19].

NAD+ synthesis occurs through de novo pathways utilizing nicotinic acid (NA), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN), or via the NAD+ salvage pathway, crucial for replenishing NAD+ stores in the body [20]. Furthermore, an extracellular conversion of NMN to NR by the cell surface enzyme CD73 contributes to intracellular NAD+ maintenance [21].

The enzyme nicotinamide N-methyltransferase (NNMT) also plays a critical role in regulating cellular NAD+ levels. By methylating nicotinamide to methylnicotinamide (MNT), NNMT reduces free nicotinamide availability for NAD+ synthesis, impacting NAD+ homeostasis. Despite associations with obesity and diabetes mellitus type two, NNMT exhibits beneficial effects by stabilizing SIRT1 and protecting against oxidative stress-induced cellular injury [22,23,24].

Interestingly, methylnicotinamide has been linked to increased lifespan, offering intriguing insights into its potential role in aging processes [25]. Moreover, the development of NNMT inhibitors shows promise in the treatment of various pathologic conditions, including cancer, obesity, metabolic disorders, and alcohol-related fatty liver disease [22,26,27,28,29].

The intricate interplay between NNMT, MNT, and the pathways they regulate underscores their significance in NAD+ homeostasis and the complex disease states influencing the aging process. Unraveling these intricacies presents opportunities for novel therapeutic strategies aimed at mitigating age-related decline and addressing associated pathologies.

The Nexus of NAD+, Sirtuins, and Longevity: A Pathway to Promising Aging Interventions

In the quest to unlock the secrets of longevity and combat age-related ailments, attention has increasingly turned to the intricate interplay between nicotinamide adenine dinucleotide (NAD+), sirtuins, and pathways promoting longevity.

Disruptions in NAD+ homeostasis and the loss of protective sirtuin activity have emerged as pivotal targets for interventions aimed at enhancing healthspan and longevity [30]. Studies have demonstrated that supplementation with NAD+ precursors, such as nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), can mitigate age-related declines in NAD+ levels, offering potential therapeutic benefits for age-related diseases [13,31,32]. Aging is characterized by a decline in the NAD+/NADH ratio, predominantly due to the depletion of NAD+ stores rather than an increase in NADH [12]. Restoring NAD+ levels has been shown to rescue mitochondrial regulatory function, counteracting NAD+-induced pseudohypoxic mitochondrial stress associated with aging [14].

SIRT1, a member of the sirtuin protein family, plays a crucial role in the cellular response to stress and has been implicated in longevity. However, research findings on the effects of SIRT1 activation on lifespan have been mixed and context-dependent. Nevertheless, studies have observed correlations between elevated SIRT1 expression and longevity-related markers, such as increased telomere length and improved insulin sensitivity in high-level athletes [33].

The beneficial effects of SIRT1 may stem from its ability to deacetylate and activate Forkhead transcription factors, including FoxO and PGC1α [34,35]. FoxOs are involved in stress resistance, apoptosis, and tumor suppression, with activation linked to longevity in model organisms [36,37]. The insulin/insulin-like growth factor signaling pathway, mediated by FoxO activity, regulates critical processes such as growth, metabolism, and longevity [38,39].

PGC1α plays a pivotal role in mitochondrial biogenesis and energy metabolism. Overexpression of PGC1α has been associated with improved insulin sensitivity and mitochondrial function, offering potential benefits for metabolic disorders [40,41,42]. Additionally, AMP-activated protein kinase (AMPK), a key regulator of energy expenditure, exhibits bidirectional interactions with SIRT1 and further modulates longevity-related processes by inhibiting mTOR signaling [43].

Furthermore, SIRT1 activity influences nuclear factor κB (NF-κB) signaling, a pathway implicated in inflammatory responses. By inhibiting NF-κB signaling, SIRT1 can mitigate chronic inflammation associated with aging and age-related diseases [44].

Maintaining adequate NAD+ levels appears crucial for optimal SIRT1 activity during aging, highlighting the potential significance of NAD+ modulation in promoting longevity [31,45,46,47]. Thus, interventions targeting NAD+ synthesis and SIRT1 activation present promising avenues for enhancing healthspan and delaying the onset of age-related pathologies.

Figure . The CD38/NAD+/SIRT1 Axis. NAD+ levels in the body can be influenced by the supplementation of precursors nicotinamide (NAM), nicotinamide riboside (NR), and nicotinamide mononucleotide (NMN). NAD+ levels decrease with age and are further metabolized by the activation of SIRT1, PARP1, SARM1, and CD38. Restoring NAD+ levels allows for an increase in SIRT1 activity due to increased substrate availability, resulting in the inhibition of age-promoting pathways and activation of adaptive and protective transcription factors and processes. The central lineage may be described as the CD38/NAD+/SIRT1 axis, and targeting this access with nutraceutical interventions may prevent the age-related decline of NAD+ levels in the body. Black lines indicate conversion or activation. Red lines indicate inhibitors or destroyers of the indicated target.

The Interplay Between PARPs and Sirtuins in NAD+ Homeostasis and Metabolic Regulation

The intricate dance of cellular metabolism and genomic stability hinges upon the delicate balance of nicotinamide adenine dinucleotide (NAD+) utilization by two key protein families: poly(ADP-ribose) polymerases (PARPs) and sirtuins. Amidst this molecular choreography, PARPs emerge as pivotal players in DNA repair and genomic maintenance through a process known as poly(ADP-ribosyl)ation (PARylation) [1, 2]. Within the PARylation process, PARP proteins facilitate the addition of ADP-ribose polymers to themselves and nuclear target proteins, necessitating the cleavage of NAD+ into nicotinamide (NAM) [3, 4].

The PARP family comprises a diverse array of proteins, with PARP1 standing out as a prominent member responsible for approximately 90% of NAD+ consumption within the PARP family [5]. This voracious appetite for NAD+ places PARPs in direct competition with sirtuins, whose activities are also reliant on NAD+ availability [6, 7]. Consequently, dysregulation of PARP activity can perturb NAD+ homeostasis, exerting profound effects on cellular physiology.

The repercussions of PARP dysregulation reverberate across a spectrum of human diseases, including xeroderma pigmentosum group A, progeroid diseases, ataxia telangiectasia, and Cockayne syndrome [8, 9]. Notably, in Cockayne syndrome, hyperactivation of PARP1 precipitates a cascade of events leading to NAD+ depletion and inhibition of SIRT1 activity [10]. However, interventions targeting PARP activity, such as PARP inhibitors or NAD+ supplementation, have shown promise in mitigating these effects, offering potential avenues for therapeutic intervention [11, 12].

Moreover, the interplay between PARPs and sirtuins extends beyond DNA repair, encompassing broader metabolic regulation. In instances of diet-induced obesity, PARP1 emerges as a central protagonist, capable of dampening SIRT1 activity through NAD+ depletion [13]. However, genetic or pharmacological interventions targeting PARP1 have demonstrated the ability to restore NAD+ levels, enhance SIRT1 activity, and ameliorate metabolic dysfunction, offering hope for combating obesity-related complications [14, 15].

While PARP1 dominates the narrative of NAD+ consumption within the PARP family, PARP2 emerges as a nuanced player, wielding both catalytic and regulatory functions [16]. Parp2-knockout mice exhibit enhanced SIRT1 activity and improved metabolic outcomes, suggesting a regulatory role for PARP2 in modulating SIRT1 expression [17]. This interplay between PARP2 and SIRT1 underscores the complexity of NAD+ signaling pathways and the need for further investigation into the specific functions of individual PARP family members.

Exploring the Role of CD38 and CD157 in NAD+ Regulation and Aging Biology

In the intricate landscape of cellular metabolism and aging biology, the enzymes CD38 and CD157 emerge as key protagonists, orchestrating the delicate balance of nicotinamide adenine dinucleotide (NAD+) levels and influencing a myriad of physiological processes. Belonging to the family of cyclic ADP-ribose (cADPR) synthases, these enzymes play pivotal roles in nucleotide metabolism and cellular signaling, with implications for aging and disease [1].

CD38 and its counterpart CD157 exhibit multifaceted enzymatic activities, encompassing both NAD+ glycohydrolase and ADP-ribosyl cyclase functions. Through these catalytic reactions, NAD+ is cleaved into nicotinamide (NAM) and ADP-ribose, while simultaneously generating the Ca2+-mobilizing second messenger molecule cADPR [2, 3]. Notably, CD38 displays a low Michaelis constant (Km) value for NAD+, rendering it a voracious consumer of this vital cofactor [4].

The implications of CD38-mediated NAD+ consumption extend far beyond simple metabolic regulation, intertwining with processes integral to aging biology. In Cd38-deficient mice, tissue NAD+ levels are markedly elevated, underscoring the central role of CD38 in age-related NAD+ decline [5, 6]. This elevation in NAD+ levels consequentially leads to enhanced activity of sirtuins, including SIRT1 and SIRT3, pivotal players in mitochondrial and lysosomal functions [7]. Moreover, pharmacological inhibition of CD38 with compounds like 78c has shown promise in restoring NAD+ levels and extending longevity in aged mice [8].

In contrast, the role of CD157 in NAD+ regulation and aging remains less well-defined. While CD157 shares enzymatic similarities with CD38, its efficiency in cADPR synthesis is considerably lower [9]. Nevertheless, CD157 may serve as a biomarker for identifying tissue-resident vascular endothelial stem cells, hinting at potential roles in tissue homeostasis and regeneration [10].

Despite their disparate roles, CD38 and CD157 collectively underscore the intricate interplay between NAD+ metabolism and aging biology. As research in this field progresses, elucidating the specific functions of these enzymes promises to deepen our understanding of cellular aging and unveil novel therapeutic avenues for age-related diseases.

The Role of SARM1 in NAD+ Depletion and Neurodegeneration

Within the intricate tapestry of cellular biology, the enzyme SARM1 emerges as a critical regulator of nicotinamide adenine dinucleotide (NAD+) metabolism, wielding profound implications for neurodegenerative diseases and traumatic brain injuries. Unlike its extracellular counterpart CD38, SARM1 operates as an intracellular NAD+-consuming glycohydrolase, orchestrating a cascade of events culminating in axonal degeneration [1].

Under normal physiological conditions, NAD+ binding to the armadillo/heat repeat motifs (ARMs) domain of SARM1 facilitates the inhibition of its Toll/interleukin receptor (TIR) domain NADase activity, maintaining cellular homeostasis [2]. However, in the aftermath of axonal injury, disruption of the NAD+-binding site or destruction of the ARM-TIR interaction precipitates constitutive activation of SARM1 [3]. This activation event triggers the dimerization of the TIR domain, resulting in the relentless consumption of NAD+ and subsequent metabolic collapse [4].

Recent advancements in our understanding of SARM1 activation have shed further light on the intricate mechanisms underlying axonal degeneration. Upon injury, binding of nicotinamide mononucleotide (NMN) induces a conformational change in the ARM domain, destabilizing the peripheral ARM domain ring and disrupting ARM-TIR interaction [5]. This conformational shift facilitates the self-association of the TIR domain, culminating in the activation of NADase function and triggering axonal degeneration [6].

The newfound insights into SARM1 activation pave the way for novel therapeutic strategies aimed at preventing or ameliorating neurodegenerative diseases and traumatic brain injuries. By targeting SARM1 as a metabolic sensor of the NMN/NAD+ ratio in neurons, researchers envision the development of interventions capable of preserving cellular integrity and halting the progression of debilitating neurological conditions [7].

Fig. – NAD+ regulates macrophage polarization. LPS challenge induces the generation of mitochondrial reactive oxygen species (mROS). This increase in ROS results in DNA damage and subsequent PARP activation, which consume NAD+ to repair damaged DNA and maintain genomic integrity. The NAD+ salvage pathway replenishes the NAD+ pools through increased NAMPT expression, thus initiating glycolytic reaction and programming pro-inflammatory macrophage polarization. In another context, diminished NAD+ levels are attributed to decreased QPRT expression in the de novo synthesis pathway. Low NAD+ concentration impairs mitochondrial respiration, thus inversely increasing glycolysis and facilitating inflammatory responses of macrophages. In addition, CD38 acts as another important NAD+-consuming enzyme during pro-inflammatory macrophage polarization.

The Complex Role of NAD+ Metabolism in Immune Response

Nicotinamide adenine dinucleotide (NAD+), a pivotal molecule in cellular metabolism, has emerged as a key player in the intricate dance of immune response. Serving as both a cofactor for metabolic enzymes and a substrate for various NAD+-consuming enzymes, NAD+ lies at the heart of cellular functions and adaptability to environmental changes. The exploration of NAD+ metabolism within the realm of immunometabolism has unveiled its significant influence on both innate and adaptive immunity, shedding light on its potential for novel therapeutic strategies.

NAD+ in Innate Immunity: A Balancing Act

The innate immune system, our first line of defense, demonstrates a remarkable plasticity influenced by the levels of intracellular NAD+. In neutrophils, for instance, the deletion of optic atrophy 1 (OPA1), a protein integral to the mitochondrial inner membrane, disrupts NAD+ regeneration. This impairment leads to a reduction in glycolysis rate, ATP production, and ultimately, the formation of neutrophil extracellular traps, highlighting NAD+’s pivotal role in neutrophil function.

Mast cells and their role in allergic reactions further exemplify the critical nature of NAD+ levels. Diminished NAD+ correlates with enhanced mast cell degranulation and anaphylactic responses. Interestingly, supplementation with NAD+ precursors, such as NMN and NR, has been shown to attenuate IgE-mediated anaphylactic responses in mouse models, revealing a potential therapeutic pathway mediated by the sirtuin SIRT6.

Moreover, NAD+ metabolism is integral to the function and activation of natural killer (NK) cells. Enhancing NAD+ levels through NMN supplementation boosts antitumor immunity, showcasing increased cytokine production and cytotoxic activity. This evidence underscores the complexity and context-dependent nature of NAD+ functions in innate immune cells, where enhancing NAD+ can yield diverse immunological outcomes.

Adaptive Immunity and NAD+: A Fine-Tuned Regulation

The role of NAD+ extends into the adaptive immune system, influencing the functions of macrophages and their phenotypic polarization. Studies have shown that NAD+ depletion, achieved through inhibiting the enzyme NAMPT, decreases the secretion of pro-inflammatory cytokines like TNF-α, altering macrophage morphology and function. Conversely, activation of the NAMPT-mediated NAD+ salvage pathway is crucial for the pro-inflammatory polarization of macrophages in response to stimuli such as lipopolysaccharide (LPS).

This dynamic regulation is further complicated by the mitochondrial production of reactive oxygen species (mROS) during macrophage activation, triggering extensive DNA damage responses and consequent NAD+ consumption. A decrease in NAD+ levels prompts an increased expression of NAMPT, sustaining glycolysis and the pro-inflammatory state. Inhibiting NAMPT, therefore, presents a novel therapeutic avenue in conditions like acute intestinal inflammation, where NAD+ metabolism modulation could shift macrophages from a pro-inflammatory to an anti-inflammatory phenotype.

The Paradox of NAD+ in Immunometabolism

The immunometabolic landscape is nuanced, with NAD+ sitting at a crossroads of metabolic pathways that dictate cellular fate and function. The same strategies that boost NAD+ levels can have divergent effects on immune cells, depending on the cellular context and the metabolic pathways engaged. For instance, while low doses of endotoxin leverage the NAMPT-dependent NAD+ salvage pathway to support pro-inflammatory responses, high doses trigger a switch to IDO1-dependent de novo NAD+ biosynthesis, leading to anti-inflammatory properties and immune tolerance.

This paradox underscores the potential of targeting NAD+ metabolism in treating inflammatory diseases, aging, and cancer. However, it also highlights the complexity of such interventions, necessitating a deep understanding of the context-specific roles of NAD+ in immune cell biology.

The exploration of NAD+ metabolism in the immune response unveils a rich tapestry of cellular processes that are vital for health and disease. The dual role of NAD+ in supporting both pro-inflammatory and anti-inflammatory states, depending on the context, presents both challenges and opportunities for therapeutic intervention. As research continues to unravel the complexities of NAD+ metabolism, the potential for innovative treatments targeting immune disorders, aging, and cancer grows ever more promising. Future studies are poised to further elucidate the intricate mechanisms at play, paving the way for targeted therapies that harness the power of NAD+ metabolism to modulate immune responses for better health outcomes.

The Pivotal Role of NAD+ in Shaping Adaptive Immunity: A Comprehensive Overview

The intricacies of adaptive immunity, a crucial component of the immune system that provides a targeted response to pathogens and tumors, have long fascinated scientists. One of the more recent revelations in this field is the significant role played by Nicotinamide adenine dinucleotide (NAD+) in adaptive immune responses. Research into the biological effects of NAD+ on adaptive immunity, which began in earnest in the early 2000s, has uncovered its vital role in T cell regulation, offering new insights into potential therapeutic strategies for cancer, autoimmune diseases, and beyond.

Fig. 3 – NAD+ regulates T cell fates through environmental lactate. SLC5A12-mediated lactate uptake into CD4+ T cells in the inflamed tissue reshapes their effector phenotypes, resulting in RORγt activation and subsequent IL-17 transcription via nuclear PKM2/STAT3 and enhanced fatty acid synthesis. It also leads to these renascent Th17 cell retention in the inflamed tissue as a result of reduced glycolysis and enhanced fatty acid synthesis. On the other hand, the continuous lactate catabolism through lactate dehydrogenase consumes amounts of NAD+ contents. The insufficient NAD+ pools cannot sustain NAD+-dependent enzymatic reactions involving glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and 3-phosphoglycerate dehydrogenase (PGDH). The dysfunction of GAPDH and PGDH leads to the depletion of post-GAPDH glycolytic intermediates and the 3-phosphoglycerate derivative serine that are important fuels for T cell proliferation. The environmental lactate eventually suppresses effector T cell proliferation.

NAD+-Induced Cell Death: A Double-Edged Sword in Immune Regulation

One of the earliest observations was that extracellular NAD+ could induce cell death in specific T cell subpopulations, notably naïve T cells and regulatory T cells (Tregs), through a process known as NAD+-induced cell death (NICD). This process, mediated by the ADP-ribosyl-transferase 2 (ART2) enzyme, involves the transfer of ADP-ribose from NAD+ to the P2X7 receptor on T cells, triggering apoptosis. This mechanism plays a critical role in the immune resistance observed in non-small cell lung cancer, where ART1 overexpression on lung cancer cells enhances susceptibility to NICD, thereby impeding effective antitumor immunity.

The interplay between ART and CD38 on the cell surface further complicates the regulatory mechanisms of extracellular NAD+ metabolism. CD38 acts to mitigate ART’s pro-apoptotic activities by reducing local NAD+ bioavailability, thus serving as a survival factor during inflammation. This delicate balance between inducing and preventing cell death highlights the complex role of NAD+ in immune regulation.

Diverse Sensitivities and Immunotherapeutic Implications

The susceptibility of different T cell subpopulations to NICD underscores the dynamic nature of T cell homeostasis. While extracellular NAD+ preferentially targets resting T cells and Tregs for apoptosis, other T cells, such as thymocytes and primed T cells lacking ART2 expression, remain resistant. This selective sensitivity has therapeutic implications, particularly in cancer, where reducing tumor-infiltrating Tregs could enhance antitumor immunity. Systemic administration of NAD+ has been shown to diminish Treg populations in various tumor models, pointing to a potential strategy for bolstering antitumor responses.

NAD+ in T Cell Activation and Differentiation

Beyond its role in cell death, NAD+ is essential for T cell activation and differentiation. Manipulating intracellular NAD+ levels, whether through supplementation with precursors or by targeting NAD+-biosynthetic or -consuming pathways, has profound effects on T cell function. For instance, NAD+ depletion can reduce T cell proliferation and inflammatory cytokine production, offering relief in models of autoimmune disease such as experimental autoimmune encephalomyelitis (EAE).

Conversely, boosting NAD+ levels can enhance T cell responses, including calcium mobilization, proliferation, and cytokine release, highlighting the potential of NAD+ manipulation in reinforcing immune responses. This duality suggests that NAD+ metabolism could be a critical lever in controlling T cell-mediated inflammation and autoimmunity.

Targeting NAD+ Metabolism in Disease Treatment

The regulation of NAD+ metabolism extends to therapeutic strategies for cancer and autoimmune diseases. Overexpression of CD38, for example, has been linked to T cell dysfunction in cancer, suggesting that co-inhibition of CD38 and PD-L1 could improve the efficacy of immune checkpoint inhibitors. Similarly, targeting NAD+-consuming enzymes like CD38 in systemic lupus erythematosus (SLE) could enhance T cell responses and reduce infection risk by improving bioenergetic fitness and viability.

Moreover, the role of NAD+ in metabolic reprogramming of T cells, particularly in the context of lactate metabolism and the NAD+/NADH ratio, underscores its importance in immune cell function. Dysregulation of NAD+ metabolism can drive pathogenic T cell responses in diseases such as lupus nephritis and rheumatoid arthritis, suggesting that targeting NAD+ biosynthesis or degradation pathways could offer novel therapeutic avenues.

NAD+, A Central Metabolite in Immunoregulation

The diverse roles of NAD+ in adaptive immunity, from regulating T cell death to influencing T cell activation and differentiation, underscore its central importance in immunoregulation. The ability to manipulate NAD+ levels and metabolism opens up new possibilities for treating a range of diseases, from cancer to autoimmune disorders. As our understanding of NAD+ metabolism deepens, so too does the potential for innovative therapeutic strategies that harness this critical metabolite to modulate immune responses for better health outcomes.

Exploring the Therapeutic Potential of NAD+ in Human Inflammatory Diseases

The pivotal role of Nicotinamide adenine dinucleotide (NAD+) in cellular metabolism, especially in regulating immune responses, has catapulted it to the forefront of potential therapeutic agents for various inflammatory conditions. Recent years have seen a surge in exploring NAD+ metabolism’s therapeutic and preventive capabilities across a wide array of preclinical models and disease settings, including Inflammatory Bowel Disease (IBD), Experimental Autoimmune Encephalomyelitis (EAE), and Systemic Lupus Erythematosus (SLE). The promising outcomes from these studies have paved the way for numerous clinical trials, aiming to validate the safety and efficacy of NAD+ therapeutics in managing inflammatory diseases. This article delves into the latest advancements in clinical trials focusing on the therapeutic implications of NAD+ across different disease spectrums.

Muscle Health and NAD+ Supplementation

Skeletal muscle, a critical component in maintaining overall physiological well-being, has been a significant focus area for NAD+ therapeutics. Preclinical studies in rodents have highlighted the potential of NR (Nicotinamide Riboside) supplementation in improving skeletal muscle function and mitigating pathological processes.

A landmark clinical trial involving the administration of 1g oral NR daily for 21 days showcased an augmented skeletal muscle NAD+ metabolome and reduced circulating inflammatory cytokines, demonstrating NR’s bioavailability and immunomodulatory properties in human muscle without affecting mitochondrial bioenergetics.

However, a subsequent study in overweight and obese patients indicated that while NR effectively increased NAD+ levels, it did not significantly impact energy metabolism or insulin resistance, suggesting that the anti-inflammatory benefits of NAD+ manipulation might not directly translate to metabolic disease treatment.

Cardiac Function and NAD+ Restoration

The heart’s dependence on NAD+ for metabolic and mitochondrial function has been well-documented, with decreased cardiac NAD+ levels being causally linked to heart failure pathologies. Animal model studies have shown that boosting cardiac NAD+ levels can improve myocardial mitochondrial function and energy metabolism. However, the role of NAD+ in modulating heart failure’s chronic sterile inflammation—a key disease progression driver—remains underexplored in clinical settings. A recent human study administering oral NR to patients with stage D heart failure reported promising outcomes, including enhanced blood NAD+ levels, improved cellular respiration, and a significant reduction in NLRP3 inflammasome and inflammatory cytokines. These preliminary results underscore the potential of NAD+ boosters in breaking the vicious cycle of cardiac inflammation and disease progression, although further large-scale, long-term studies are needed to confirm these findings.

NAD+ in the Battle Against COVID-19

The COVID-19 pandemic has underscored the critical role of metabolic health and immune response in disease severity and mortality. Hyperinflammatory responses and metabolic dysfunctions, including NAD+ and glutathione (GSH) deficiencies, have been identified as key factors in severe COVID-19 cases. Recent clinical trials employing combined metabolic activators (CMAs), including NAD+ and GSH precursors, have shown promising results, with patients experiencing shorter durations to symptom-free recovery and improved inflammation and antioxidant metabolism markers. Additionally, targeting NAD+ degradation pathways, specifically the CD38/NAD+ axis, emerges as a novel therapeutic strategy, potentially mitigating the lung immunopathology observed in severe COVID-19 cases.

Unveiling the Nexus of NAD+ and Circadian Rhythm: Insights into Aging and Disease

Nicotinamide adenine dinucleotide (NAD+) plays a pivotal role in orchestrating the intricate dance of the circadian metabolic clock, crucial for maintaining physiological rhythms essential for health and well-being. Recent research has shed light on the profound impact of NAD+ availability on circadian regulation and its implications for aging and disease.

Studies in aging mice have revealed a stark correlation between NAD+ levels and the proper functioning of the circadian clock. Older mice, characterized by diminished NAD+ stores, exhibit prolonged repression of CLOCK/BMAL1 transcription, leading to disrupted mitochondrial and transcriptional oscillations [48]. However, supplementation and restoration of NAD+ in circadian mutant mice have shown promising results in re-establishing proper respiratory oscillations and circadian metabolic regulation, primarily through the regulatory activity of SIRT3 [49]. These findings underscore the critical role of NAD+ and sirtuin activation in maintaining the integrity of endogenous clocks and suggest potential therapeutic avenues for addressing age-related perturbations in circadian processes [50].

Furthermore, NAD+ deficiencies have been implicated in various age-related diseases, prompting ongoing research into NAD+-based interventions to mitigate these common afflictions [51,52,53,54]. The intricate interplay between NAD+ availability and circadian regulation unveils novel insights into the underlying mechanisms of aging and age-related pathologies, offering promising targets for intervention.

In addition to its role in circadian rhythm regulation, NAD+ homeostasis is intricately linked to mitochondrial metabolism, a fundamental process crucial for cellular function and energy production [55]. Perturbations in NAD+ levels, often exacerbated by the activity of the NAD+-degrading enzyme CD38, can disrupt mitochondrial function and contribute to metabolic disorders and age-related diseases [56]. CD38, known for its involvement in immune activation and inflammatory signaling, emerges as a key player in the regulation of NAD+ availability and SIRT1 activity [57,58].

Interestingly, CD38 expression increases with age, correlating with heightened NAD+ degradation and susceptibility to age-related metabolic diseases [59]. While CD38 deficiency has shown protective effects against obesity, metabolic disorders, and cancer progression in animal models, further research is needed to elucidate its implications for human health [60]. Moreover, the intricate interplay between CD38, senescent cells, and inflammation underscores the complex nature of age-related pathologies [61].

Senescent cells, characterized by permanent growth arrest, accumulate with age and contribute to chronic inflammation, a phenomenon known as “inflammaging” [62]. The expression of CD38 in senescent cells exacerbates NAD+ decline, further perpetuating age-related biological deficits [63,64,65]. Targeting CD38 activity or expression presents a promising interventional strategy to enhance NAD+ availability and mitigate age-related pathologies.

Unlocking the Potential of NMN as an NAD+ Boosting Therapeutic: A Comprehensive Analysis

As the pursuit of interventions to counteract aging-related decline intensifies, a promising avenue emerges in the form of NAD+ boosting therapeutics. Among the various NAD+ precursors, Nicotinamide Mononucleotide (NMN) has garnered significant attention for its potential to enhance NAD+ levels efficiently. This article provides a detailed examination of NMN’s role in NAD+ supplementation, exploring its bioavailability, therapeutic benefits, and safety considerations.

NAD+ precursors, including NR, NMN, and NAM, play crucial roles in NAD+ synthesis. Notably, NMN stands out due to its streamlined conversion process to NAD+, requiring only one step compared to other precursors. Clinical studies have demonstrated the efficacy of NMN supplementation in increasing NAD+ levels and improving various health parameters.

For instance, a study involving adults aged 40 to 65 years showed a significant increase in intracellular NAD+/NADH ratio following 60 days of NMN supplementation at a dosage of 300 mg daily. This provides valuable evidence supporting NMN’s role as a safe and effective NAD+ booster.

Moreover, NMN supplementation exhibits promising outcomes across diverse health conditions. Research indicates its potential in addressing cardiovascular and neurodegenerative diseases, as well as combating aging-related mechanisms such as telomere attrition. Short-term supplementation of NMN has shown to increase telomere length and modulate gut microbiota, suggesting broader systemic benefits beyond NAD+ augmentation.

Furthermore, NMN supplementation appears to enhance physiological functions, including aerobic capacity and circadian rhythm regulation. Studies on adult runners revealed improved respiratory parameters and aerobic capacity following NMN supplementation. Additionally, NMN has been linked to enhancements in sleep quality and physical performance among older adults, underscoring its potential in promoting healthy aging.

Despite these promising findings, concerns regarding safety persist. Recent data raised alarms about the potential risk of cancer metastasis associated with NR administration. However, contrasting evidence demonstrates the safety of NMN supplementation, with studies reporting no adverse effects even at relatively high doses. Nonetheless, further research is imperative to elucidate potential discrepancies in safety profiles among NAD+ precursors.

To bridge the gap between preclinical findings and clinical applicability, ongoing clinical trials are investigating the translatability and mechanistic actions of NMN supplementation. These trials aim to provide comprehensive insights into NMN’s therapeutic potential and safety profile, facilitating informed decision-making in clinical practice.

In conclusion, NMN emerges as a promising therapeutic agent for boosting NAD+ levels and combating age-related decline. Its efficacy in enhancing NAD+ levels, coupled with its potential health benefits and favorable safety profile, positions NMN as a frontrunner in the quest for anti-aging interventions. However, continued research is essential to fully harness the therapeutic potential of NMN and ensure its safety and efficacy in clinical settings.

Table 1. Various clinical trials (completed and ongoing) detailing the use of NMN and other NMN derivates to improve health, metabolic markers, and disease parameters.

Clinical Trials	Compound of Interest
Nicotinamide Mononucleotide Increases Muscle Insulin Sensitivity in Prediabetic Women [82]	NMN
Effect of Oral Administration of Nicotinamide Mononucleotide on Clinical Parameters and Nicotinamide Metabolite Levels in Healthy Japanese Men [83]	NMN
Nicotinamide Mononucleotide Supplementation Enhances Aerobic Capacity in Amateur Runners: a randomized, double-blind study [77]	NMN
Effect of 12-Week Intake of Nicotinamide Mononucleotide on Sleep Quality, Fatigue, and Physical Performance in Older Japanese Adults: a randomized, double-blind placebo-controlled study [79]	NMN
Safety Evaluation of Beta-nicotinamide Mononucleotide Oral Administration in Healthy Adult Men and Women [84]	NMN
The Efficacy and Safety of Beta-nicotinamide Mononucleotide (NMN) Supplementation in Healthy Middle-aged Adults: a randomized, multicenter, double-blind, placebo-controlled, parallel-group dose-dependent clinical trial [85]	NMN
A Multicenter, Randomized, Double-Blind, Parallel Design, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Uthever (NMN Supplement), an Orally Administered Supplementation, in Middle-Aged and Older Adults [73]	NMN
MIB-626, an Oral Formulation of a Microcrystalline Unique Polymorph of Beta-Nicotinamide Mononucleotide, Increases Circulating Nicotinamide Adenine Dinucleotide and its Metabolome in Middle-Aged and Older Adults [86]	MIB-626
Phase 2a MIB-626 vs. Placebo COVID-19 (NCT05038488)	MIB-626
Effect of Oral NAD+ Precursors Administration on Blood NAD+ Concentration in Healthy Adults (NICO) (NCT05517122)	NAM, NR, and NMN
Effect of NMN Supplementation on Organ System Biology (VAN) (NCT04571008)	NMN
Pharmacodynamics and Tolerance of Nicotinamide Mononucleotide (NMN, 400mg/Day) in Healthy Adults (NCT04862338)	NMN
Study to Evaluate the Effect of Nicotinamide Mononucleotide (NMN) As an Adjuvant to Standard of Care (SOC) On Fatigue Associated with Covid-19 Infection (NCT05175768)	NMN
Nicotinamide Mononucleotide in Hypertensive Patients (NCT04903210)	NMN
Safety and Pharmacokinetics of Nicotinamide Mononucleotide (NMN) in Healthy Adults (NCT04910061)	NMN
Effect of NMN (Nicotinamide Mononucleotide) on Polycystic Ovary Syndrome (NMN) (NCT05305677)	NMN
Effect of NMN (Nicotinamide Mononucleotide) on Diminished Ovarian Reserve (Including Premature Ovarian Insufficiency) (NCT05485610)	NMN
Effect of NMN on Muscle Recovery and Physical Capacity in Healthy Volunteers with Moderate Physical Activity (NCT04664361)	NMN

Maximizing NAD+ Restoration: A Combined Approach Towards Anti-Aging Intervention

Amidst the burgeoning interest in anti-aging strategies, the spotlight increasingly falls on interventions aimed at bolstering NAD+ levels. Clinical trials exploring the efficacy of NAD+ boosting compounds are gaining traction, yet standardized metrics to assess their benefits remain imperative. This article delves into the potential of combining NAD+ precursors with other geroprotective agents to optimize anti-aging effects, considering factors such as SIRT1 activation, CD38 inhibition, and methylation support.

NAD+ precursors have demonstrated promise in human trials, laying a foundation for further exploration of their synergistic effects with other pathways involved in NAD+ metabolism. The involvement of CD38 and SIRT1 pathways underscores the complexity of NAD+ regulation, presenting opportunities for interventions to amplify NAD+ boosting effects. By targeting multiple pathways simultaneously, the potential for maximizing NAD+ restoration becomes evident.

One pivotal approach revolves around supplementing safe doses of NMN alongside other geroprotectors and nutraceuticals, thereby augmenting endogenous NAD+ levels. This combinatorial strategy not only ensures the replenishment of physiological NAD+ levels but also harnesses the longevity benefits inherent in these compounds.

Several geroprotectors have shown promise in enhancing endogenous NAD+ levels while conferring their own anti-aging benefits. For instance, resveratrol, a polyphenol found in red wine, is known for its SIRT1 activation properties, which synergize with NMN supplementation to potentiate NAD+ restoration. Similarly, quercetin, a flavonoid abundant in fruits and vegetables, exhibits CD38 inhibition, complementing NMN’s actions in bolstering NAD+ levels.

Moreover, the inclusion of methylation support agents such as betaine and trimethylglycine (TMG) further enhances the efficacy of NAD+ boosting interventions. These compounds facilitate the methylation of nicotinamide, a precursor to NAD+, thereby augmenting NAD+ synthesis and promoting epigenetic regulation.

The synergistic health effects observed with the combination of NMN and geroprotectors underscore the potential of this approach in combating aging-related decline. By harnessing the complementary mechanisms of action of various compounds, a multifaceted strategy emerges to counteract the physiological effects of aging comprehensively.

The integration of NAD+ precursors with other geroprotectors represents a promising avenue in the quest for anti-aging interventions. Through synergistic interactions with pathways involved in NAD+ metabolism, this combined approach offers a nuanced strategy to restore youthful NAD+ levels and mitigate age-related deterioration. As research in this field progresses, further insights into the synergistic effects of different compounds will undoubtedly pave the way for more effective and personalized anti-aging interventions.

The Role of NAD+ in Hypertension: A Pathway to Innovative Therapeutic Strategies

Hypertension remains a critical challenge in public health, implicated in approximately 8.5 million global deaths annually due to its major role in the development of stroke, ischemic heart disease, and renal disease. The pathophysiology of hypertension is complex, with endothelial dysfunction and arterial stiffness recognized as pivotal factors contributing to the onset of atherosclerotic cardiovascular diseases. Recent research underscores the significance of improving vascular function to not only curb the morphological changes associated with atherosclerosis but also to mitigate its later clinical complications. This understanding has catalyzed a push for deeper insights into the molecular underpinnings of hypertension and the vascular damage it induces, aiming to uncover novel therapeutic avenues for its management.

Central to the discussion on innovative treatment strategies is the role of Nicotinamide adenine dinucleotide (NAD+), a coenzyme integral to various cellular processes, which notably diminishes with age. The decline of NAD+ levels is associated with numerous aging-related diseases, including hypertension. Efforts to boost NAD+ levels through dietary supplements and the modulation of its metabolic pathways have shown promise in preclinical studies, where NAD+ administration in aged mice ameliorated endothelial dysfunction and lessened arterial stiffness. Furthermore, clinical trials in elderly humans have demonstrated that supplementation with nicotinamide riboside, a precursor to NAD+, can effectively reduce arterial stiffness, underscoring the potential of NAD+ replenishment as a targeted therapeutic strategy for hypertension.

The biosynthesis and degradation of NAD+ are tightly regulated processes, with CD38 emerging as a crucial enzyme in the NAD+ degradation pathway. Inhibition of CD38 has been shown to prevent the age-associated decline in NAD+ levels, improve metabolic function, and diminish DNA damage accumulation. In addition to its protective effects against metabolic dysfunction, CD38 inhibition has also been found to shield against endothelial injury following ischemic events in animal models. However, the relationship between CD38 expression, NAD+ levels, and hypertension in humans remains underexplored. Given that hypertension is increasingly recognized as a chronic inflammatory condition, the involvement of inflammation in the regulation of CD38 expression offers a novel perspective on the disease’s mechanism.

This study posits that the depletion of NAD+ in endothelial cells, driven by CD38 activation, plays a critical role in the elevation of blood pressure (BP) and the exacerbation of vascular damage in hypertension. The inflammatory response, triggered by macrophage infiltration into the vascular endothelium, is hypothesized to be a key factor in activating CD38 and thus depleting NAD+. Through the examination of NAD+ levels in peripheral blood mononuclear cells and aortas of hypertensive patients, along with the analysis of BP and vascular dysfunction, this research seeks to delineate the link between NAD+ dynamics and hypertension. Additionally, a randomized control trial is conducted to evaluate the impact of nicotinamide mononucleotide supplementation on BP and vascular health in hypertensive individuals, providing a mechanistic insight into the potential therapeutic benefits of targeting NAD+ metabolism in hypertension management.

The implications of this study could significantly shift the paradigm in hypertension treatment, highlighting the importance of cellular metabolism and inflammation in the disease’s pathogenesis. By unraveling the intricate relationship between NAD+ levels, CD38 activity, and hypertension, this research paves the way for novel interventions that target these molecular pathways, offering hope for more effective management of hypertension and its associated vascular complications.

Detailed Analysis of NAD+, NMN, and NR in Dietary Sources

The quest for enhancing bodily NAD+ levels has turned the spotlight on dietary sources of its precursors: nicotinamide mononucleotide (NMN), nicotinamide riboside (NR), and others such as nicotinamide (NAM) and nicotinic acid (NA). Research in this area aims to identify foods that naturally contain these compounds, offering an alternative or adjunct to supplementation for boosting NAD+ biosynthesis.

NMN and NR in Foods: Analytical Insights

• Edamame Beans and Avocados: Among the first studies to quantify NMN in foods, Mills et al. (2016) reported significant levels of NMN in edamame beans, with concentrations ranging from 0.47 to 1.88 mg per 100g, and in avocados, from 0.36 to 1.60 mg per 100g. This pioneering work illuminated the presence of NMN in commonly consumed plant-based foods, hinting at their potential role in dietary NAD+ enhancement.
• Broccoli, Cucumber, Cabbage, and Tomato: The same study by Mills et al. also identified these vegetables as sources of NMN, albeit in smaller amounts compared to edamame and avocados. The findings suggest a broader dietary basis for NMN intake, extending to a variety of plant foods.
• Milk (Bovine and Human): Ummarino et al. (2017) delved into the content of NR and NMN in milk, unveiling that bovine milk contains NR concentrations of 0.5–3.6 μM, while human milk is richer in NMN, with levels of 2.1–9.8 μM. This indicates milk as a viable source of these NAD+ precursors, with variations between species highlighting the importance of dietary diversity for NAD+ biosynthesis.
• Seafood and Raw Meats: Although not as rich in NMN as plant sources, these animal products were found to contain NMN at concentrations of 0.06–0.42 mg per 100g, presenting another avenue for dietary intake of NAD+ precursors.
• Craft Beers: Recent advancements have shown the potential of yeast-mediated production of NR and NMN in craft beers, with hops playing a role in enhancing NR levels during fermentation. This novel discovery points to fermented beverages as emerging sources of NAD+ precursors.

The Role of Cooking and Food Processing

The analysis of NAD+ precursors in foods also considers the impact of cooking and processing techniques. The work by Ummarino et al. highlighted how traditional methods for measuring niacin in foods might inadvertently account for NR and NMN after these compounds are hydrolyzed to NA under the conditions of hot acid or alkaline extraction. This underscores the complexity of accurately quantifying NAD+ precursors in dietary sources and the potential for cooking processes to alter their availability.

Microbiota and Bioavailability

The role of the gut microbiota in converting NMN to NAD+ precursors such as nicotinic acid mononucleotide (NAMN) further complicates the landscape of dietary NAD+ enhancement. This microbial pathway, alongside mammalian metabolic processes, signifies the intricate interplay between diet, digestion, and cellular NAD+ synthesis.

The identification and quantification of NAD+, NMN, and NR in foods represent a burgeoning field of research with significant implications for nutrition science and health. As analytical techniques advance and more data becomes available, the potential for dietary strategies to support cellular health and longevity through NAD+ biosynthesis becomes increasingly tangible. Future studies are needed to clarify the bioavailability, optimal intake levels, and long-term effects of dietary NAD+ precursors, paving the way for evidence-based recommendations and the development of NAD+-boosting functional foods.

An In-depth Analysis of NMN and NR Supplementation: Safety, Pharmacokinetics, and Clinical Insights

The burgeoning interest in the therapeutic potential of Nicotinamide Mononucleotide (NMN) and Nicotinamide Riboside (NR) supplements is underscored by their central role in enhancing NAD+ levels, crucial for cellular metabolism, DNA repair, and overall health. This detailed examination draws upon a constellation of clinical trials and studies, delving into the safety, pharmacokinetics, and physiological effects of these NAD+ precursors across various health conditions.

Clinical Trials Landscape

A spectrum of clinical trials (e.g., NCT04228640, NCT04910061 on safety and pharmacokinetics; NCT04823260, NCT04685096 on aging; and others focusing on hypertension, heart failure, COVID-19, and mitochondrial function) underscores the multifaceted research into NMN and NR. These trials aim to elucidate not just the potential health benefits but also the safety profile and body’s handling of these compounds.

Safety and Efficacy: A Closer Look

Safety Concerns and Pharmacokinetics: A pivotal aspect of NMN and NR supplementation is their safety profile. Studies have explored various dosages, with one key study revealing that doses up to 1500 mg/kg/day of synthetic NMN were safe in rats over a 90-day period, despite some physiological changes at higher doses. Human trials have similarly demonstrated the safe metabolism of NMN, with doses ranging from 100 to 500 mg showing significant metabolite increase in plasma without adverse effects. Yet, the rapid degradation of NMN in blood storage poses challenges for accurate pharmacokinetic studies.

Therapeutic Potential and Risks: While the therapeutic prospects of NMN and NR are promising, including for conditions like ulcerative colitis (ClinicalTrials.gov Identifier: NCT06214078), concerns linger about their long-term impact. For instance, NMN supplementation in an oncogenic mouse model suggested a potential for promoting tumorigenic processes under certain stress conditions, highlighting the complexity of NAD+-dependent processes and the need for cautious evaluation.

Clinical Outcomes and Health Implications: On the efficacy front, NMN and NR supplementation has shown various health benefits. Oral NR supplementation has been linked to significant increases in NAD+ concentrations and metabolites associated with NAD+ synthesis, without elevating harmful byproducts. These findings suggest a potential for NR in enhancing cellular health and metabolism. Moreover, preliminary studies indicate NMN’s role in improving skeletal muscle biology and metabolic profiles, hinting at its broader implications for muscle physiology and metabolic health.

Pharmacological Insights

The pharmacokinetics of NMN and NR, characterized by rapid absorption and subsequent distribution to tissues, highlight the dynamic nature of NAD+ metabolism. This rapid metabolism suggests a need for tailored dosing strategies to maintain therapeutic NAD+ levels without overexposure. Additionally, the increase in NAD+ levels and related metabolites post-supplementation underscores the potential of NMN and NR to positively influence health outcomes, from mitochondrial function to cardiovascular health.

As the body of evidence grows, so does the understanding of NMN and NR’s safety, pharmacokinetics, and therapeutic potential. Future studies should aim to address the long-term effects of supplementation, optimal dosing regimens, and the mechanisms underlying the health benefits of these NAD+ precursors. Moreover, exploring the interplay between NAD+ metabolism and chronic diseases could unlock new therapeutic avenues, reinforcing the importance of rigorous clinical evaluation in substantiating the health claims of NMN and NR supplements.

Table 1 – Effects of NMN and NR using in preclinical and clinical studies

NAD+ precursor	Experimental model	Treatment	Outcomes	Reference
NMN	Cerebromicrovascular endothelial cells (CMVECs) isolated from 3- and 24-month-old male F344xBN rats	Cultured primary CMVECs were treated NMN (5 × 10−4 mol/L) for 1 to 5 days	Restoration of angiogenic capacity (formation of capillary-like structures, proliferative, and migratory capability) and attenuation of oxidative stress in aged CMVECs	[140]
	Young (3 months) and aged (24 months) male C57BL/6 mice	Intraperitoneal injections of 500 mg NMN/kg body weight per day for 14 days	Reverse the aging-induced cerebrovascular endothelial dysfunction. Rescued the neurovascular coupling responses associated with an improved cognitive performance by increasing endothelial NO-mediated vasodilation	[141]
	Male Sprague–Dawley rats (12 weeks old)	Intraperitoneal administration of 100 mg/kg on alternate days for a period of 3 months	Prevented neuronal loss and rescued the memory deficits in diabetic rats. Increased brain NAD+ levels, normalized the diabetes-induced decrease in both SIRT1 and PGC-1α, preserving protein deacetylation, and hippocampal biochemical and mitochondrial respiration	[26]
	12- and 14-month-old females C57BL6/JAusb mice	2 g/L in drinking water for 4 weeks	Increased NAD(P)H levels and rejuvenated oocyte quality, leading to fertility restoration and reversal of the adverse effect of maternal age on embryo development	[142]
	Model of isoproterenol-induced cardiac fibrosis in male C57/B6 mice (8–10 weeks old)	Intraperitoneal injections of 500 mg/kg every 3 days before and after isoproterenol injection	Prevention of cardiac dysfunction and attenuation of cardiac hypertrophy. The NAD+ levels and SIRT1 activity were restored, inhibiting oxidative stress, and Smad3 acetylation	[143]
	Model aging mice (male C57BL/6 mice 24-month-old)	Intraperitoneal injections of 500 mg NMN/kg body weight per day for 2 weeks	Anti-aging changes in pro-inflammatory and pro-atherogenic miRNA expression profile in the aorta. Rescue of vascular function and attenuation of oxidative stress	[144]
	24-month-old C57BL/6 mice	Intraperitoneal injections of 500 mg/kg body weight per day for 2 weeks	Reversion of age-related changes in neurovascular mRNA expression profile, leading to the rescue of youthful neurovascular phenotype and to the improvement of cerebromicrovascular endothelial function. Induction of genes involved in mitochondrial rejuvenation, anti-inflammatory, and anti-apoptotic effects, such as SIRT1-mediated upregulation of PGC-1α, FOXO3- and FOXO4-	[145]
	Eight healthy men 45–60 years old	Oral NMN (300 mg/day) after 30 min of breakfast for 90 days	Elongating telomere length in peripheral blood mononuclear cells (PBMC)
NR	Humans 10 twin pairs	Escalating dose of NR supplementation (250 to 1000 mg/day) for 5 months	DNA methylation and modulation epigenetic control of gene expression in muscle and adipose tissue. Reprogramming of tissue NAD+ and mitochondrial metabolism and muscle stem cell identity	[47•]
	Alzheimer’s disease mouse model	NR treatment (12 mM given in their drinking water for 3 months before the tests)	It normalized reduced cerebral NAD+/NADH ratio, lessened phosphorylated Tau, DNA damage, neuroinflammation, and apoptosis of hippocampal neurons	[24]
	8-week-old specific pathogen-free male C57BL/6 J mice	Gavage of NR (400 mg/kg body weight/day) + 50% (v/v) ethanol	NR alleviated the alcohol-induced liver injury. It inhibited the activation of the PP1 pathway, improving serum and liver triglyceride levels and lipid accumulation. Also, NR intervention changed the gut microflora structure and restored the abundance of gut microflora to a level similar to those in normal mice (control). It restored the reduction of bile acid levels in mice feces induced by alcohol exposure, which was correlated with gut microflora	[8]
	C57BL/6 J and Fndc5 knockout (Fndc5−/−) mice with non-alcoholic fatty liver disease (NAFLD) induced by high-fat or methionine/choline-deficient diet	Diet of pellets with NR 400 mg/kg/day for 12–16 weeks. Or intraperitoneal injections 400 mg/kg/day during 2 weeks	Reversion of NAFLD by regulating SIRT2-deppendent Fndc5 deacetylation and deubiquitination, which stimulates the “exerkine” Fndc5/irisin	[146]
	4-week-old male C57BLKS/J db/db mice (transgenic diabetic model) and age-matched C57BL/6 J mice (control)	NR-supplemented food (approximately 400 mg/kg/day) for 12 weeks	Accelerated diabetic wound healing and angiogenesis. Reversion of the reduced NAD concentration in BM-EPCs. It raised the number of EPCs and elevated the tube formation and adhesion ability of BM-EPCs in vitro. NR upregulated Sirt1 expression modulating acetylated PGC-1α expression, and increased p-AMPK/AMPK and VEGF. Furthermore, prevented the accumulation of subcutaneous fat and serum insulin and increasing serum adiponectin levels	[147]
	6-week-old male Balb/c mice for C26 Adenocarcinoma–induced cancer cachexia model	Diet supplemented with NR at 200 or 400 mg/kg daily for 3 weeks	Prevention C26 adenocarcinoma–induced muscle atrophy and weight loss. It restored cachexia-induced fat loss, reverting the epididymal lipolysis and inhibiting the adipose triglyceride lipase gene. NR diet decreased the cytokines TNF-α and IL-6. Increased SIRT1 and mitogen-activated protein kinases (ERK1/2 and JNK) were inactivated. Also, it inhibited muscle-specific ubiquitin–proteasome ligases, such as atrogin-1 and MuRF-1. Genes implicated in muscle atrophy and degradation, Pax7 and mitofusin-2 respectively, were attenuated. PCG-1α, a marker for muscle regeneration, was restored	[148]
	15-months-old male C57BL/6 J mice	Chow supplemented to provide NR at 300 mg or 600 mg/kg/day for 4 weeks	Enhancement of treadmill endurance and open-field activity in middle-aged mice NR increased the size of aerobic muscle fibers, enlarging the slow-twitch fibers In addition, it boosted aerobic and anaerobic, basal and maximal respiration of both mice- and human-derived myogenic progenitors in vitro. The differentiation of human myogenic progenitors toward multinucleated skeletal muscle myotubes was improved along with greater myofiber size, fusion index, and expression of differentiation markers	[149]

Detailed Analysis of NMN and NR Supplementation for Anti-Aging

NAD+ Levels and Age-Related Decline

• Decline in NAD+ Levels: Research consistently shows a decline in NAD+ levels across various tissues with aging, critical for cellular metabolism and energy production. Studies highlight a significant reduction, with some reporting over a 50% decrease in NAD+ levels in older adults compared to younger individuals [96, 97].

NMN and NR Supplementation Studies

• NMN Supplementation: In aged mice, NMN supplementation (500 mg/kg body weight daily) has been shown to significantly increase NAD+ levels in key metabolic tissues such as the liver and skeletal muscle within just one week of treatment [13]. This increase in NAD+ has been associated with improvements in metabolic health markers, including enhanced insulin sensitivity and reduced signs of age-related metabolic decline.
• NR Supplementation: Clinical trials involving NR have demonstrated promising outcomes. For example, a dose of 300 mg/day of NR for 8 weeks in a study involving middle-aged adults led to a significant increase in NAD+ levels by approximately 40%, improving markers of mitochondrial function and reducing oxidative stress [63].

Impact on Aging Biomarkers

• Telomere Lengthening: NMN treatment has been associated with telomere lengthening in animal models. Specifically, NMN administered in drinking water (approximately 5 mM) for 8 weeks showed notable lengthening of telomeres in generation 4 mice, indicating a reversal of cellular age [36].
• Mitochondrial Function: Long-term NMN administration at doses of 100 to 300 mg/kg/day for 12 months significantly enhanced mitochondrial respiratory capacity and reversed age-associated gene expression changes in skeletal muscle [1••].

Therapeutic Implications and Considerations

• Safety and Efficacy: While these supplements show promise, determining the optimal dose for safety and efficacy in humans is ongoing. The established upper intake level of NMN for safety in humans has been suggested at 900 mg per day based on rat studies extrapolated to human equivalent doses [82].
• CD38 and NAD+ Decline: The role of CD38 in NAD+ decline highlights a target for potentially mitigating age-related decreases in NAD+. Inhibition or knockdown of CD38 has been shown to preserve NAD+ levels and mitigate signs of aging in preclinical models [99].

The therapeutic potential of NMN and NR in the context of aging and age-related diseases is underscored by their ability to elevate NAD+ levels, improve mitochondrial function, and potentially reverse biomarkers of cellular aging, such as telomere length. However, the translation of these findings into human health benefits requires further clinical investigation to fully understand the implications of long-term supplementation and to establish guidelines for their use in anti-aging therapies. As research progresses, NMN and NR remain at the forefront of potential interventions for extending healthspan and improving quality of life in aging populations.

Exploring the Anti-COVID-19 Potential of NMN and NR

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has highlighted the vulnerability of certain populations, particularly the elderly, to severe outcomes. The aging process, characterized by immunosenescence and inflammaging, exacerbates the risk, complicating the immune system’s ability to combat the virus effectively. This vulnerability is partly attributed to the shortening of telomeres and a decrease in naïve lymphocytes, leading to impaired immune function and an increase in pro-inflammatory cytokines, which are critical factors in the severity of COVID-19 infections.

NAD+ and COVID-19

Research indicates a dysregulation in the genes related to NAD+ synthesis and usage during SARS-CoV-2 infection, suggesting an increased demand for NAD+ metabolic pathways. Poly(ADP-ribose) polymerases (PARPs), which play a critical antiviral role, require NAD+ for the inhibition of viral genome translation. However, the virus encodes a macrodomain protein that disrupts this process, facilitating viral replication and virulence by inhibiting PARPs’ protective effects. This leads to excessive PARPs activation and NAD+ consumption, underscoring the potential therapeutic importance of boosting NAD+ levels to restore antiviral functions.

Sirtuins and Inflammation Regulation

Sirtuins, specifically SIRT1, SIRT2, and SIRT3, modulate the intensity of inflammatory responses, potentially mitigating cytokine storms associated with severe COVID-19 cases. SIRT6, in particular, suppresses NF-κB signaling, pivotal in apoptosis and cellular senescence, suggesting that enhancing NAD+ levels could be beneficial in managing COVID-19 by supporting immune response and reducing inflammation.

Clinical Evidence on NMN and NR Efficacy

A notable case study involving critically ill patients over 50 years old reported significant COVID-19 symptom resolution following an NMN cocktail treatment, suggesting NMN’s potential in reversing severe outcomes like cytokine storms. Furthermore, a study on combined metabolic activators (CMAs), including NR, showed significantly faster recovery times in COVID-19 patients, reinforcing immune responses and regulating metabolism.

ATP Metabolism and COVID-19 Severity

Severe COVID-19 cases have been linked to alterations in purinergic metabolism, with higher ATP levels and lower adenosine levels observed, contributing to disease severity. The reduced expression of ectonucleotidases CD39 and CD73 in severe cases disrupts the anti-inflammatory regulation by adenosine, suggesting a potential therapeutic angle in modulating ATP metabolism and exploring the role of NAD+ in this context.

Analytical Insights into NMN and NR Supplementation Against COVID-19

Case Study on NMN Supplementation in Critically-ill COVID-19 Patients

A case study involving 10 critically-ill COVID-19 patients over the age of 50 years explored the effects of an NMN cocktail treatment. The treatment regimen consisted of 83 mL of NMN mixed with 400 mL of water, consumed twice daily before breakfast and dinner. This intervention led to notable clinical improvements:

• Pre-treatment Condition: Patients exhibited low oxygen saturation, pulmonary infiltrates, and elevated inflammation biomarkers, indicative of severe COVID-19.
• Post-treatment Outcomes: There was a rapid improvement in bilateral pulmonary infiltrates, fever resolution, and a decrease in inflammation biomarkers. These changes suggest a significant amelioration of COVID-19 symptoms.
• Relapse in a Discontinued Case: A patient who discontinued the treatment after 3 days experienced a relapse with fever and pulmonary infiltrates 8 days later, underscoring the potential importance of continuous NMN supplementation for sustained symptom resolution.

This case study indicates that NMN supplementation could play a crucial role in reversing severe COVID-19 complications, such as cytokine storms, potentially contributing to improved patient outcomes.

Combined Metabolic Activators (CMAs) Study

Another significant study examined the efficacy of combined metabolic activators (CMAs) in improving COVID-19 outcomes. The CMAs consisted of a mixture of NR (1 g), L-carnitine tartrate (3.73 g), N-acetylcysteine (2.55 g), and serine (12.35 g), administered orally twice daily after meals for 14 days. The key findings from this study include:

• Recovery Times: Patients receiving CMAs experienced significantly faster complete recovery times compared to the placebo group, with recovery times of 6.6 vs 9.3 days in a phase 2 study and 5.7 vs 9.2 days in a phase 3 trial.
• Biochemical Improvements: Treatment with CMAs led to notable improvements in plasma levels of inflammation and antioxidant metabolism-related biomarkers, including alanine aminotransferase (ALT), lactate dehydrogenase (LDH), creatinine, glucose, and proteins. These changes suggest a reinforced immune response and regulated amino acid and lipid metabolism in treated patients.

These studies collectively highlight the promising therapeutic potential of NMN and NR supplementation, along with CMAs, in mitigating the severity and improving recovery times in COVID-19 patients. The data underscores the need for further research to fully understand the mechanisms, optimize dosing, and confirm the efficacy of these treatments in larger, diverse patient populations.

The specificity of these findings provides valuable insights into the role of NAD+ metabolism in combating COVID-19, opening avenues for targeted therapeutic strategies to support patients facing this global health challenge.

Detailed Exploration of the Anti-Inflammatory Effects of NMN and NR

NR Supplementation and Inflammatory Response in PBMCs

• Study Overview: A 24-hour administration of Nicotinamide Riboside (NR) to Peripheral Blood Mononuclear Cells (PBMCs) from healthy subjects demonstrated significant anti-inflammatory effects.
• Key Findings:
  • NR mimicked the fasting effect, blunting NLRP3 inflammasome activation.
  • Enhanced mitochondrial quality control via SIRT3 activation.
  • Reduced mitochondrial ROS levels through decreased acetylation of SOD2 and isocitrate dehydrogenase 2, and increased mitochondrial SOD2 activity.
  • Significantly decreased secretion of IL-1β and TNF-α in monocytes (IL-1β reduction over 50% from ~22,000 to ~10,000 pg/mL; TNF-α reduction over 75% from >2,000 to <500 pg/mL) and in macrophages (IL-1β reduction around 20% from >300 to <250 pg/mL; TNF-α reduction approximately 45% from ~1,800 to ~1,000 pg/mL).

NR Supplementation in Older Men

• Therapy Dosage: 1g of oral NR per day for 3 weeks.
• Outcomes:
  • Increased NAD+ metabolome levels in whole blood and skeletal muscle.
  • Significant reduction in circulating levels of inflammatory cytokines (IL-2, IL-5, IL-6, TNF-α) with reductions noted from ~20 to ~5 pg/mL for interleukins and from ~250 to ~200 pg/mL for TNF-α.

NMN’s Impact on Pro-inflammatory Cytokines

• Treatment Details: NMN supplementation at 500 μM concentration.
• Effects on Macrophage Cell Lines: Demonstrated in LPS-activated mouse and human macrophage cell lines (THP-1, RAW264.7), NMN:
  • Decreased production of pro-inflammatory cytokines.
  • Alleviated LPS-induced inflammation and oxidative stress through the COX-2-PGE2 axis.
  • Downregulated COX-2 expression and significantly decreased mRNA expressions and extracellular secretion of IL-6 and IL-1β.
  • Reduced cellular levels of prostaglandin E2 (PGE2).
  • Suppressed inflammation-associated pathways, including prostanoid biosynthesis, LPS/IL-1 mediated inhibition of RXR function, IL-6 signaling, and NF-κB signaling.

Conclusion and Implications

The detailed analysis of the anti-inflammatory effects of NMN and NR supplementation provides strong evidence of their potential therapeutic benefits. By modulating inflammatory responses at the cellular level, enhancing mitochondrial quality control, and reducing pro-inflammatory cytokine production, these NAD+ precursors offer promising avenues for treating and possibly preventing conditions associated with chronic inflammation.

These findings highlight the complex interplay between NAD+ metabolism and the immune system’s response to inflammation, suggesting that NMN and NR could be key components in developing new anti-inflammatory therapies. Further research, including larger clinical trials, will be essential to fully elucidate the mechanisms, optimize dosing strategies, and confirm the long-term efficacy and safety of NMN and NR supplementation in diverse populations.

Regulation of Energy Metabolism through NAD+ Precursors

NAD+ in Energy Production Pathways

NAD+ is instrumental in major energy production pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid oxidation. A decline in NAD+ levels signifies an imbalance in energy homeostasis, affecting energy-sensing pathways critical for maintaining a balance between energy production and expenditure. This imbalance is associated with various metabolic disorders, such as insulin resistance and fatty liver.

Impact of Nutrient Conditions on NAD+ Levels

• Under high-fat and -protein intake conditions, NAD+ levels decrease, illustrating the impact of excess calorie consumption on NAD+ or the NAD+/NADH ratio.
• The adenosine monophosphate-activated protein kinase (AMPK) acts as a cellular energy regulator, sensing changes in the intracellular AMP/ATP ratio and maintaining cellular energy stores by activating catabolic pathways and inhibiting anabolic pathways.

Therapeutic Interventions with NR and NMN

• NR Administration:
  • Dose: 450 mg/kg body weight for 45 days.
  • Outcomes: Stabilized myocardial NAD+ levels, increased glycolysis, and citrate and acetyl-coenzyme A metabolism in a mouse model of dilated cardiomyopathy, attenuating heart failure development.
  • Additional effects: In mice, NR supplementation (400 mg/kg/day) stimulated SIRT1 and SIRT3 activity, enhancing mitochondrial function, oxidative metabolism, energy expenditure, and endurance performance. It also protected against hyperinsulinemia, elevated cholesterol levels, and weight gain induced by a high-fat diet.
• NMN Administration:
  • Dose: 500 mg/kg body weight intraperitoneally injected for 21 days.
  • Outcomes: Reduced adiposity, hepatic and plasma triglyceride levels in offspring of mice fed either a chow or high-fat diet. Beneficial effects on glucose tolerance were observed in metabolically compromised mice (high-fat diet from obese progenitress).
  • Additional study findings: NMN supplementation (400 mg/kg for 8 weeks) modulated exercise-induced benefits and oxidative stress markers in obese mice, highlighting its antioxidative effects.

These studies underscore the potential of NAD+ precursors like NMN and NR in regulating energy metabolism and their therapeutic effects across various conditions. While NR and NMN have shown promise in enhancing mitochondrial function and addressing metabolic dysfunctions, their efficacy can vary based on dietary conditions and the metabolic health of the subjects. The precise modulation of NAD+ levels through these precursors offers a nuanced approach to treating metabolic disorders, indicating the need for further research to optimize therapeutic strategies and understand the conditions under which these interventions are most effective.

Anti-Diabetic Effects of NMN and NR: A Closer Look at the Data

Redox Imbalance and Diabetic Complications

• Key Mechanism: The hallmark of diabetes mellitus, hyperglycemia, leads to a redox imbalance, notably between NAD+ and NADH ratios, triggering oxidative stress and metabolic syndromes.
• Pathway Disturbance: High-fat and -protein intake can decrease NAD+ levels, affecting AMP/ATP ratios and subsequently NAD+/NADH balance. This imbalance, or pseudohypoxia, initiates reductive stress and mitochondrial dysfunction, leading to oxidative damage [117].

Therapeutic Interventions and Outcomes

• NR and Diabetic Cardiomyopathy:
  • Dosage: 400 mg/kg/day oral gavage for 4 weeks.
  • Outcomes: Improved cardiac function in diabetic mice by elevating myocardial NAD+ content, promoting mitochondrial fusion via mitofusin 2, and activating the SIRT1-PGC1α-PPARα pathway to suppress oxidative stress and cell apoptosis [19].
• NMN against Chronic Fructose Feeding:
  • Dosage: 100 µmol/l for islet culture; 500 mg/kg body weight intraperitoneally, 16 hours before tissue sampling.
  • Benefits: Restored insulin secretion and corrected inflammation-induced islet dysfunction. Improved glucose-stimulated insulin secretion in fructose-rich diet-fed mice, indicating a protective effect against beta cell failure through an anti-inflammatory mechanism [20].
• NMN in Type 2 Diabetes Models:
  • Dosage: 500 mg/kg body weight/day intraperitoneally for 11 days.
  • Effects: Substantially ameliorated impaired glucose tolerance and enhanced hepatic insulin sensitivity. The treatment reversed gene expression changes related to oxidative stress, inflammatory response, and circadian rhythm, partly due to SIRT1 activation [13].
• NMN in Aged BESTO Mice:
  • Dosage: 500 mg/kg body weight, 14 hours prior to assays.
  • Results: Restored glucose-stimulated insulin secretion and improved glucose tolerance in aged BESTO and wild-type mice by increasing NAD+ levels and restoring phenotypes lost with age [98].
• NMN Supplementation in Postmenopausal Women:
  • Dosage: 250 mg/day orally for 10 weeks in women with overweight or obesity and prediabetes.
  • Outcomes: Increased NAD+ content in PBMCs and improved insulin signaling and sensitivity in skeletal muscle [38].

The detailed examination of NMN and NR’s anti-diabetic effects reveals significant therapeutic potential across various models, from mitigating diabetic cardiomyopathy in mice to improving insulin sensitivity in postmenopausal women. These findings underscore the critical role of NAD+ precursors in reversing the oxidative stress and inflammation associated with diabetic conditions, offering promising avenues for future treatments. As research progresses, these NAD+ enhancing therapies could become integral to managing diabetes mellitus and its complications, further emphasizing the need for continued exploration in this field.

The Interplay Between Gut Microbiota and NAD+ in Host Health

Protective Effects of Gut Microbial NMN on Acute Pancreatitis (AP)

• Study Findings: NMN derived from gut microbiota was shown to ameliorate AP injury in mouse models by:
  • Increasing NAD+ levels
  • Activating the SIRT3-PRDX5 pathway
• Therapeutic Dosage: Pretreatment with NMN (500 mg/kg body weight/day) was administered intraperitoneally for 28 consecutive days.
• Outcomes: Enhanced NAD+ biosynthesis in the pancreas, mitigated AP-mediated mitochondrial dysfunction, oxidative damage, and inflammation in a partially SIRT3-dependent manner.

NMN, NR, and Gut Microbiota Modulation

• Selective Growth Stimulation: NMN and NR have been found to selectively stimulate the growth of beneficial bacteria such as Bifidobacterium and Lactobacillus, which are linked to:
  • Improved gut health
  • Prevention of diarrhea
  • Enhanced gut barrier function
  • Reduced inflammation
  • Support for the immune system

Impact of NR on High-Fat Diet-induced Weight Gain

• Study Design: Mice were fed with a 60% high-fat diet supplemented with 0.4% NR for 168 days.
• Weight Gain Reduction: There was an almost 16% reduction in weight gain in NR-supplemented mice compared to the control group.
• Blood Glucose Levels: A reduction in fasting blood glucose levels was observed.
• Gut Microbiota Alteration: Dietary NR supplementation and FMT from NR-treated donors altered the intestinal microorganisms composition, enriching butyrate-producing Firmicutes.

NMN’s Role in Inflammatory Bowel Disease (IBD) and Colitis Models

• IBD Study Dosage: NMN was administered via gavage at a dose of 1 mg/g of body weight for 21 days.
• Outcomes: Increased microbial abundance and diversity, improved mucus secretion, and enhanced expression of tight-junction proteins, attenuating intestinal mucosal permeability.

Long-term NMN Treatment and Gut Microbiota Modulation

• Dosage: 0.1 to 0.6 mg/mL of NMN in drinking water for 12 weeks.
• Effects:
  • Increased abundance of butyric acid-producing bacteria and other probiotics such as Akkermansia muciniphila.
  • Decreased abundance of harmful bacteria like Bilophila and Oscillibacter.
  • Improved integrity of the intestinal epithelium and reduced mucosal permeability.

The intricate relationship between gut microbiota and NAD+ metabolism plays a crucial role in maintaining host health, particularly in the context of metabolic and inflammatory diseases. NMN and NR not only act directly to improve host NAD+ levels and metabolic health but also modulate gut microbiota composition in ways that confer protective effects against diseases like acute pancreatitis, obesity, and IBD. These findings underscore the potential of targeting the gut microbiota-NAD+ axis as a therapeutic strategy, although further research is needed to fully understand the mechanisms and optimize interventions.

Understanding the Fate of NAD+ Post Intravenous Administration: A Clinical Insight

The therapeutic potential of Nicotinamide Adenine Dinucleotide (NAD+) has garnered significant interest within the medical community, particularly concerning its intravenous (IV) application for enhancing cellular homeostasis and treating various conditions. A recent study has provided valuable insights into the pharmacokinetics of NAD+ following IV administration, documenting the changes in levels of NAD+ and its key metabolites in both plasma and urine over an 8-hour period using a clinical dosing regimen of 750 mg NAD+.

Key Findings from the Study:

• Safety and Hepatic Function Improvement: The IV infusion of NAD+ at 750 mg over a 6-hour period did not produce any observable adverse events in the test cohort. Instead, a reduction in plasma activities of enzymes indicative of hepatic stress, such as LD, AST, and GGT, was observed. This suggests an enhancement in the integrity of both intrahepatic and post-hepatic tissues within the 8-hour timeframe.
• Metabolic Dynamics of NAD+ and Metabolites: Contrary to expectations, plasma NAD+ levels did not show an increase until after 2 hours, peaking at approximately 400% above baseline for NAD+ and metabolites (NAM, meNAM, and ADPR) at the 6-hour mark. This delay indicates a rapid, complete tissue uptake and/or metabolism of NAD+ and its metabolites in the initial hours post-infusion.
• Enzymatic Catabolism and Metabolite Formation: The study highlights the role of various enzymes, including sirtuins (SIRTs 1–7), ADP-ribose transferases (ARTs), poly(ADP-ribose) polymerases (PARPs), and cyclic ADP-ribose synthases (CD38, CD157), in the effective catabolism of NAD+. Notably, extracellular NAD+ pyrophosphatases and the cell-surface protein CD73 contribute to the degradation of NAD+ to AMP and NMN, and the conversion of NMN into NR, respectively.
• Implications for NAD+ Based Therapies: The findings underscore the complex fate of IV-administered NAD+, challenging previous assumptions about its immediate bioavailability and underscoring the body’s capacity for rapid utilization. The observed rapid sequestration into tissue or extravascular compartments highlights the potential of NAD+ based therapies in conditions associated with NAD+ depletion.

Clinical Dosing and Pharmacokinetics of NAD+

• Dosage: 750 mg of NAD+ administered IV over 6 hours.
• Constant Rate: Infusion at 3 μmoles/min, totaling 1,080 μmoles by the end of 6 hours.
• Expected Intravascular Increase: Theoretically, every 30 min, an additional rise in plasma NAD+ levels of at least 18 μM was anticipated, considering an average blood volume of 5 liters.

Key Observations and Metabolic Insights

• Safety and Hepatic Function: The infusion did not produce observable adverse events. Instead, it was associated with reduced activities of enzymes indicative of hepatic stress (LD, AST, GGT), suggesting enhanced hepatic and bile duct tissue integrity within the 8-hour frame.
• Plasma and Urine NAD+ Levels: Contrary to expectations, plasma NAD+ levels did not rise until after 2 hours, peaking at ~400% above baseline for NAD+ and key metabolites (NAM, meNAM, and ADPR) only at the 6-hour mark.
• Urinary Excretion Peak: Both NAD+ and meNAM showed peak urinary excretion at 6 hours, indicating rapid metabolism or tissue uptake within the initial 2 hours of infusion.

Enzymatic Metabolism of NAD+

• Key Enzymes: Effective NAD+ catabolism is achieved through enzymes like sirtuins (SIRTs 1–7), ADP-ribose transferases (ARTs), poly(ADP-ribose) polymerases (PARPs 1–17), and cyclic ADP-ribose synthases (CD38, CD157), along with extracellular NAD+ pyrophosphatases.
• CD73’s Role: Converts NMN into NR, facilitating potential resynthesis to NAD+ across cell membranes.
• Evidence of CD38 Activity: A parallel rise in plasma NAM and ADPR suggested major metabolism of NAD+ to NAM and ADPR by NAD glycohydrolase activity, predominantly CD38, by the 6-hour time point.

Implications for NAD+ Based Therapies

This study illuminates the complex fate of IV-administered NAD+, underscoring a rapid, initial complete tissue uptake and/or metabolism of NAD+ and its metabolites, challenging prior assumptions about its pharmacokinetics. The absence of a rise in plasma or urine NAD+ levels until after 2 hours post-infusion suggests efficient sequestration into tissue or extravascular compartments, highlighting the body’s capacity for rapid NAD+ utilization and the potential therapeutic implications for conditions associated with NAD+ depletion.

These findings contribute significantly to the understanding of NAD+ pharmacokinetics and its metabolic impact, providing a crucial foundation for optimizing NAD+ based therapies, particularly in the context of metabolic and hepatic health. Further research is essential to explore the mechanisms of tissue uptake and the therapeutic potential of targeting specific metabolic pathways with NAD+ infusions.

NAD+ Metabolism and Therapeutic Applications: An In-depth Analysis

NAD+ and Its Crucial Role in Cellular Homeostasis

Nicotinamide Adenine Dinucleotide (NAD+) plays a pivotal role in redox reactions, facilitating vital processes like glycolysis, the tricarboxylic acid (TCA) cycle, and fatty acid oxidation. The balance of NAD+ is a hallmark of cellular energy homeostasis, with its depletion linked to various metabolic disorders.

The Preiss-Handler Pathway and NAD+ Biosynthesis

The conversion of nicotinic acid (NA) to NAD+ involves several steps, starting with the catalysis of NA to nicotinic acid mononucleotide (NAMN), followed by the conversion of NAMN to nicotinic acid adenine dinucleotide (NAAD), and culminating in the formation of NAD+. This pathway, although indirect, contributes significantly to the systemic levels of NAD+ alongside the more direct NAM salvage pathway.

Impact of NAD+ Precursors on Clinical Outcomes

Clinical trials have demonstrated the efficacy of NAD+ precursors like nicotinamide (NAM) and nicotinamide riboside (NR) in increasing blood NAD+ concentrations and mitigating the effects of conditions like UV immunosuppression and metabolic syndromes. For instance, oral administration of 500 mg NAM significantly increased blood NAD+ levels by 1.3-fold, while 1000 mg/d of NR elevated NAD+ levels by up to 2.7-fold in various cohorts.

The Role of Gut Microbiota in NAD+ Metabolism

Emerging research suggests a symbiotic relationship between gut microbiota and host NAD+ metabolism, with certain microbial metabolites enhancing NAD+ biosynthesis and contributing to the host’s metabolic health. This interaction underscores the potential of targeting gut microbiota as a novel approach to modulating NAD+ levels and treating related disorders.

Safety Profiles and Side Effects of NAD+ Precursors

While NAD+ precursors have shown promising therapeutic benefits, their safety profiles and potential side effects warrant careful consideration. NA, known for its use in treating dyslipidemia, can cause adverse effects like flushing and hyperglycemia. Conversely, NAM and NR appear to have a better tolerance in humans, with ongoing studies exploring their long-term safety and efficacy.

TABLE 2. The safety and antiaging effects of NMN in human clinical trials

Registration number	Design	Dose & duration	Indicators	Outcome	Location	References
UMIN000021309	Nonblinded, nonrandomized, non–placebo-controlled study; 10 healthy men aged 40–60 y	Oral administration: 100, 250 or 500 mg for 5 h	Clinical parameters, ophthalmic parameters, sleep quality score, serum parameters, NMN metabolites levels in plasma	↑NMN metabolites (2Py and 4Py) in plasma and bilirubin levels; ↓creatinine, chloride, and glucose levels within the normal ranges in serum; No significant changes in ophthalmic examination and sleep quality score; Single oral administration of NMN up to 500 mg is safe and well-tolerated in healthy men without causing any significant deleterious effects	Japan	[35]
jRCTs041200034	Double-blind, randomized, placebo-controlled study; 30 healthy volunteers aged 20–65 y	Oral administration: 250 mg daily for 12 wk	Adverse events, clinical parameters, blood and urine biochemical parameters, body composition, skeletal muscle mass, bone mineral mass, NAD+, and amino acid metabolome of blood	↑NAD+ and NAMN levels but not NMN; Pulse rate is strongly correlated with the increase in NAD+ level; No obvious adverse effects, and no significant changes in other indicators; Oral administration of NMN is safe	Japan	[140]
/	Double-blind, block-randomized, placebo-controlled study; 32 overweight or obese adults aged 55–80 y	Oral administration: 1000 mg once daily or twice daily for 14 d	NMN, NAD+, and NAD+ metabolome in blood and urine	1000 mg once or twice daily regimens were safe and associated with substantial dose-related increases in blood NAD levels and its metabolome	America	[122]
NCT03151239	Double-blind, randomized, placebo-controlled study; 25 postmenopausal and prediabetic women aged 55–75 y	Oral administration: 250 mg daily for 10 wk	NMN metabolites and NAD+ in plasma, PBMCs, and skeletal muscle; body composition and basal metabolic variables; skeletal muscle insulin sensitivity and signaling; skeletal muscle global transcriptome profile	↑ NAD+ and NMN metabolites in plasma; ↑ NMN metabolites in skeletal muscle but not NMN; ↑muscle insulin sensitivity, insulin signaling	America	[36]
ChiCTR2000035138	Double-blind, randomized, placebo-controlled study; 48 healthy recreationally trained runners aged 27–50 y	Oral administration: 300, 600 or 1200 mg daily for 6 wk	Body composition and cardiopulmonary function	↑aerobic capacity, enhanced O2 utilization of skeletal muscle; ↑VT in a dose-dependent manner; No obvious adverse symptoms and abnormal ECG	China	[145]
UMIN000036321	Double-blind, randomized, placebo-controlled study; 42 healthy old men aged ≥65 y	Oral administration: 250 mg daily for 12 wk	Clinical characteristics, blood and urine biochemical parameters, body composition, skeletal muscle mass, segmental lean	↑NAD+ and NAD+ metabolite levels in blood, improved muscle strength and performance, and no obvious adverse effects were observed	Japan	[141]
UMIN000038097	Double-blind, randomized, placebo-controlled study; 108 overweight or obese adults aged ≥65 y	Oral administration: 250 mg daily for 12 wk	body composition, muscle mass, bone mass, sleep quality, fatigue, physical performances	NMN intake in the afternoon is more effective in improving lower limb function and reducing drowsiness in older adults	Japan	[118]
NCT04228640	Nonblinded, nonrandomized, non–placebo-controlled study; 8 healthy men aged 45–60 y	Oral administration: 300 mg daily for 30–90 d	The telomere length of the PBMC	↑ telomere length of PBMC, which may be the potential molecular mechanisms of NMN for extending lifespan	China	[147]
NCT04228640	Double-blind, block-randomized, placebo-controlled study; 66 healthy participants aged 40–65 y	Oral administration: 300 mg NMN/d for 60 d	Blood cellular NAD+/NADH concentration in serum, six minutes walking endurance test, blood pressure, pulse pressure, SF-36 questionnaire, adverse events; blood biochemical parameters, HOMA-IR	↑NAD+/NADH levels in the serum, SF-36 score, minute walking endurance, and HOMA-IR index; ↓blood pressure, pulse pressure, and blood glucose; All test data did not have any statistically significant changes. However, the increase in NAD+/NADH levels in serum and the improvement in overall health and walking endurance were clinically significant	China	[146]
UMIN000043084	Double-blind, randomized, placebo-controlled study; 31 healthy participants aged 20–65 y	Oral administration: 1250 mg NMN/d for 4 wk	Safety evaluation of NMN oral administration in healthy adult men and women	Did not cause changes exceeding physiological variations (including anthropometry, hematological, biochemical, urine, and body composition)	Japan	[178]

2Py, N-methyl-2-pyridine-5-carboxamide; 4Py, N-methyl-4-pyridone-5-carboxamide; ECG, electrocardiogram; HOMA-IR, Homeostatic Model Assessment for Insulin Resistance; NAD, nicotinamide adenine dinucleotide; NAMN, nicotinic acid mononucleotide; NMN, nicotinamide mononucleotide; PBMC, peripheral blood mononuclear cell; SF-36, 36-Item Short Form Survey; VT, ventilatory threshold.

Assessing the Safety and Potential of NMN Supplementation: A Comprehensive Overview

In the realm of scientific research, particularly within the scope of anti-aging and health supplementation, Nicotinamide Mononucleotide (NMN) has garnered significant attention over the past few years. Researchers globally have embarked on a quest to determine whether the promising effects of NMN, observed in cellular and animal models, can be replicated in humans, thereby ushering in a new era of anti-aging interventions. This article delves into the current landscape of NMN research, specifically focusing on its safety, efficacy, and the broader implications of its use in human populations.

The inaugural human clinical trial to assess the safety of NMN supplementation was conducted by the Keio University School of Medicine in 2016, under the identifier UMIN000021309. This pioneering study marked the beginning of human-based research into NMN, involving a short-term trial on 10 healthy men. Participants were administered NMN capsules containing doses of 100, 250, or 500 mg after overnight fasting, followed by a 5-hour monitoring period. The study’s findings were pivotal, showing that while NMN metabolites in human plasma increased, no significant clinical symptoms or harmful effects were observed, indicating that NMN up to a 500 mg dose is safe and well-tolerated.

Following this initial foray, several other studies have been conducted, expanding the scope of research into NMN’s safety and potential benefits. These studies have explored various dosages and durations, including 250 mg daily for 6 to 12 weeks, and higher doses such as 300, 600, and 1200 mg daily for shorter periods. Notably, Harvard Medical School ventured into administering the highest recorded oral dose of 1000 mg twice daily over a 14-day period. Across these studies, NMN’s safety profile remained consistent, showcasing good tolerance among participants.

A recent investigation further solidified NMN’s safety profile by evaluating its effects in 31 healthy individuals aged 20 to 65 over 4 weeks, with a daily dosage of 1250 mg. This study also included an Ames test to evaluate mutagenicity, concluding that NMN is a non-mutagenic substance, safe and well-tolerated by the study cohort.

Despite these positive findings, the demographic diversity in NMN research has been somewhat limited, with a significant focus on older individuals. This skew towards older participants raises questions about the optimal timing for anti-aging interventions, suggesting a potential benefit from starting NMN supplementation at a younger, healthier age to maximize its longevity benefits. The limited number of participants in these studies, ranging from 8 to 108 individuals, also points to the preliminary phase of clinical research, emphasizing the need for larger, more inclusive studies.

Furthermore, the safety and efficacy of NMN are not solely confined to its lack of adverse effects. Some studies have ventured beyond safety assessments, examining the impact of NMN on NAD+ and its metabolites in the body. Notable findings include the observation of significant increases in NAD+ and NAMN concentrations in the blood post-NMN supplementation, with some studies also noting correlations between pulse rate and NAD+ concentration increases. These insights suggest a broader physiological impact of NMN, potentially linked to energy consumption and metabolic health.

Despite the overwhelmingly positive safety profile, a few studies have raised concerns about the potential for NMN to exhibit prodegenerative effects in specific contexts, such as in a chemotherapy-induced peripheral neuropathy mouse model and in enhancing proinflammatory states in oncogene-induced senescence cells. These findings, while isolated, underscore the necessity for continued research into NMN’s long-term effects and its interactions within complex biological systems.

In conclusion, the journey of NMN from a promising anti-aging compound in preclinical models to a potential dietary supplement or therapeutic for human use is fraught with both excitement and caution. The body of research thus far underscores NMN’s safety and tolerability in humans, providing a strong foundation for future studies. However, the quest to fully understand NMN’s efficacy, optimal dosage, and broader implications for human health is far from over. As the scientific community continues to unravel the mysteries of NMN, it remains imperative to approach each discovery with a balanced view, considering both the potential benefits and the need for vigilant, comprehensive research to ensure the well-being of all potential users.

The Safety and Anti-Ageing Effects of Nicotinamide Mononucleotide in Human Clinical Trials: An Update

Qin Song^1#, Xiaofeng Zhou^2#, Kexin Xu³, Sishi Liu³, Xinqiang Zhu⁴*, and Jun Yang^3,5*

Supplementary table 1 The effects of NAD⁺ precursors on the levels of NAD⁺ and its metabolites in human clinical trials

Dose	Duration	NAD+	NAD+ metabolome	Test sample	References
NMN 250 mg/day	5 hours	–	↑ 2Py, ↑ 4Py	Plasma	(35)
NMN 500 mg/day	5 hours	–	↑ 2Py, ↑ 4Py	Plasma
Baseline (Placebo)	2 weeks	No specific value is given	NMN 32.6 ng/mL, NAM 10.2 ng/mL, 1-Methyl NAM 7.57 ng/mL, 2-Py-NAM 103 ng/mL, NR 0.406 ng/mL	Blood	(122)
NMN 1 g once daily	2 weeks	↑ Increasing about 1-folds	↑ NMN 88.2 ng/mL, ↑ NAM 65.2 ng/mL, ↑ 1-Methyl NAM 146 ng/mL, ↑ 2-Py-NAM 2150 ng/mL, ↑ NR 1.3 ng/mL	Blood
NMN 1 g twice daily	2 weeks	↑ Increasing about 2-folds	↑ NMN 148 ng/mL, ↑ NAM 140 ng/mL, ↑ 1-Methyl NAM 276 ng/mL, ↑ 2-Py-NAM 4230 ng/mL, ↑ NR 1.48 ng/mL	Blood
Baseline (Placebo)	2 weeks	–	↑ 2Py 16700 ng/mL No significant change: NMN 333 ng/mL, NAM 174 ng/mL	Urine
NMN 1 g once daily	2 weeks	–	↑ 2Py 137000 No significant change: NMN 384 ng/mL, NAM 290 ng/mL	Urine
NMN 1 g twice daily	2 weeks	–	↑ 2Py 273000 ng/mL No significant change: NMN 308 ng/mL, NAM 703 ng/mL	Urine
Baseline (Placebo)	4/8/12/16 weeks	About 20 μm	No specific value is given	Blood	(140)
NMN 250 mg/day	4 weeks	↑ Increasing about 2.5-folds	↑ NAMN No significant change: NAAD, NMN, NR, NAR, NAM, NA, MNAM	Blood
NMN 250 mg/day	8 weeks	↑ Increasing about 2-folds	↑ NAMN No significant change: NAAD, NMN, NR, NAR, NAM, NA, MNAM	Blood
NMN 250 mg/day	12 weeks	↑ Increasing about 1.7-folds	↑ NAMN No significant change: NAAD, NMN, NR, NAR, NAM, NA, MNAM	Blood
NMN 250 mg/day	16 weeks	No significant change	No significant change: NAMN, NAAD, NMN, NR, NAR, NAM, NA, MNAM	Blood
Baseline (Placebo)	10 weeks	About 30 pg/mg	No specific value is given	PBMCs/ Plasma	(36)
NMN 250 mg/day	10 weeks	↑ Increasing about 1.7-folds in PBMC	↑ 2Py and 4Py in plasma	PBMCs/ Plasma
Baseline (Placebo)	10 weeks	About 3.5 pg/mg	No specific value is given	Skeletal muscle
NMN 250 mg/day	10 weeks	No significant change	↑ 2Py and 4Py	Skeletal muscle
Baseline (Placebo)	12 weeks	About 0.35 μm	No specific value is given	Blood	(141)
NMN 250 mg/day	12 weeks	↑ Increasing about 2.57-folds	↑ NMN, ↑ NR,↑ NAMN,↑ NAR No significant change: NA, NAM	Blood
Baseline (Placebo)	3 weeks	210 pmol/mg	NAAD 0.35 pmol/mg, MeNAM 0.35 pmol/mg, Me-2Py 1.1 pmol/mg, Me-4Py 0.3 pmol/mg, NR 1.25 pmol/mg, NAM 86.5 pmol/mg	Skeletal muscle	(131)
NR 1g/day	3 weeks	197 pmol/mg	↑ NAAD 0.73 pmol/mg, ↑ MeNAM 1.45 pmol/mg, ↑ Me-2-Py 6.6 pmol/mg, ↑ Me-4Py 1.6 pmol/mg No significant change:NR 1.4 pmol/mg, NAM 92 pmol/mg	Skeletal muscle
Baseline (Placebo)	3 weeks	20.9 μm	NMN 1.13 μm, NAAD 0.04μm, MeNAM 0.1μm, Me-2Py 1.44μm, Me-4Py 0.48μm, NR 0.15μm, NAM 9.5μm	Blood
NR 1g/day	3 weeks	↑ 47.75 μm	↑ NMN 1.63 μm, ↑ NAAD 0.18 μm, ↑ MeNAM 0.66 μm, ↑ Me-2Py 7.69 μm, ↑ Me-4Py 3.82 μm No significant change:NR 0.16 μm,NAM 10.6 μm	Blood
Baseline (Placebo)	3 weeks	–	NAR 10.3 μmol/mol, NR 31.7 μmol/mol, NAM 106.5 μmol/mol	Urine
NR 1g/day	3 weeks	–	↑ Me-2-py, ↑ Me-4Py, ↑ NAR 185.5 μmol/mol, ↑ NAM 282μmol/mol No significant change:NR 41.5 μmol/mol	Urine
NR 1 g twice daily	12 weeks	–	↑ NAM No significant change:MeNAM, Me-2Py, Me-4Py, NAR	Urine	(143)
NR 500 mg/day	2 days	–	↑ NADH, ↑ NADPH	Erythrocytes	(144)
Baseline (Placebo)	6 weeks	6.2 pmol/mg	NADP 3.3−17.9 pmol/mg, NAM 109−411 pmol/mg, NAAD 0.0−2.3 pmol/mg, NMN 0.0−5.5 pmol/mg	PBMCs	(120)
NR 1000 mg/day	6 weeks	↑ Increasing about 1.6-folds	↑ NAAD 0.0−8.7 No significant change:NADP 2.7−42.7 pmol/mg, NAM 171−1357 pmol/mg, pmol/mg, NMN 0.0−11.9 pmol/mg	PBMCs
Baseline (Placebo)	12 weeks	500-2500 pmol/mg	NADH 100-1000 pmol/mg, NADP 50-400 pmol/mg, NADPH 100-500 pmol/mg	Skeletal muscle	(142)
NR 1000 mg/day	12 weeks	No significant change	All no significant changes	Skeletal muscle
NR 1 g/day	1 weeks	↑ Increasing 2.7-folds	↑ NMN, ↑ NADP, ↑ NAM, ↑ MeNAM, ↑ Me-2Py, ↑ Me-4Py, ↑ NAAD	PBMCs	(130)
NR 1 g/day	1 weeks	–	↑ NAM, ↑ MeNAM, ↑ Me-2Py, ↑ Me-4Py	Plasma
NR 1 g/day	1 weeks	–	↑ NAM, ↑ MeNAM, ↑ Me-2Py, ↑ Me-4Py	Urine
NAM 500 mg	1 hour	↑ Increasing about 1.3-folds	–	Blood	(129)
NAM 500 mg	1.5 hours	No significant change	–	Blood
Baseline	9 days	27 μM	–	Blood	(132)
NR 250-2000 mg/day	9 days	↑ 50 μM	–	Blood
Baseline (Placebo)	8 weeks	21.0 ng/ml	NAM 22.3 ng/ml, MeNAM 3.1 ng/ml	Blood	(138)
NR 100 mg /day	8 weeks	24.3 ng/ml	No significant change:NAM 26.6 ng/ml, MeNAM 5.6 ng/ml	Blood
NR 300 mg /day	8 weeks	↑ 32.3 ng/ml	↑ MeNAM 10.1 ng/ml, No significant change:NAM 27.9 ng/ml	Blood
NR 1000 mg /day	8 weeks	↑ 49.2 ng/ml	↑ NAM 43.7 ng/ml, ↑ MeNAM 26.6 ng/ml	Blood
Baseline (Placebo)	8 weeks	–	MeNAM 4.1 ng/μg creatinine, Me2PY 15 ng/μg creatinine	Urine
NR 100 mg /day	8 weeks	–	No significant change: MeNAM 6.6 ng/μg creatinine, Me2PY 30 ng/μg creatinine	Urine
NR 300 mg /day	8 weeks	–	↑ MeNAM 10.6 ng/μg creatinine, ↑ Me2PY 51 ng/μg creatinine	Urine
NR 1000 mg /day	8 weeks	–	↑ MeNAM 17.8 ng/μg creatinine, ↑ Me2PY 113 ng/μg creatinine	Urine
Baseline (Placebo)	6 weeks	1.019 nmol/mg	NAAD, NAD, NADH, NADP, NADPH, NAM, NMN, MeNAM	Skeletal muscle	(139)
NR 1000 mg /day	6 weeks	1.125 nmol/mg	↑ NAAD, ↑ MeNAM, No significant change: NAD, NADH, NADP, NADPH, NAM, NMN	Skeletal muscle
Baseline	9 days	No specific value is given	–	Blood	(133)
NR 2000 mg/day	9 days	↑ Increasing about 2-folds	–	Blood
Baseline (Placebo)	7 days	No specific value is given	No specific value is given	Blood	(134)
NR 1000 mg/day	7 days	↑ Increasing about 2-folds	↑ NAAD, ↑ ADPR, ↑ Me-4Py	Blood
Baseline (Placebo)	32.4 ±2.53 days	No specific value is given	No specific value is given	Cerebrospinal fluid	(119)
NR 1000 mg/day	32.5 ±2.7 days	–	↑ Me2PY	Cerebrospinal fluid
NR 1000 mg/day	32.5 ±2.7 days	–	↑ NAAD, ↑ MeNAM, ↑ Me2PY, ↑ Me-4Py, ↑ Nam N-oxide	Skeletal muscle
NR 1000 mg/day	32.5 ±2.7 days	–	↑ NAAD, ↑ MeNAM	PBMCs
Baseline (Placebo)	10 weeks	No specific value is given	–	Blood	(135)
NR 500-1000 mg/day	10 weeks	↑ Increasing about 2-folds	–	Blood
Baseline (Placebo)	6 weeks	No specific value is given	No specific value is given	Blood	(136)
NR 500 mg twice daily	6 weeks	↑ Increasing about 1-folds	No significant change: NADH	Blood
Baseline	5 months	No specific value is given	No specific value is given	Blood	(137)
NR 250 mg/week, then 1000 mg/day	1 month, then 4 months	↑ Increasing about 2-folds	↑ NAAD, ↑ NMN, ↑ Me-4Py, No significant change: NAR, NADP, ADPR	Blood

“-”：It was not been tested, “↑”: Significant increasing.

Supplementary table 2 Completed but unpublished clinical trials and ongoing clinical trials

The safety and metabolic kinetics of NMN
Trial Name	Registration number		Design	Dose & duration	Indicators	Status	Location	Registration time
Assessment of the safety of long-term nicotinamide mononucleotide (NMN)	UMIN000030609		Open label, non-randomized, uncontrolled study; 30 healthy male aged 40-60 years	Oral administration: intake of NMN for 8 weeks	Physical and laboratory examinations, the kinetics of NMN and metabolites of nicotinamide, the effect of daily NMN administration on glucose metabolism	Completed	Japan	2019
Safety assessment of the yeast extract containing nicotinamide mononucleotide (NMN)	UMIN000039527	Double-blind, randomized, placebo-controlled study; 33 healthy adults aged 20-65 years		Oral administration: 2.5 g/day for 12 weeks	Height, weight, body fat percentage, BMI, systolic blood pressure, diastolic blood pressure, heart rate, blood test, urine testing, diary	Completed	Japan	2019
To evaluate the efficacy and safety of vitamin NMN in middle aged and older adults for anti-ageing and work-out enhancer	CTRI/2019/12/022514		Double-blind, randomized, placebo- controlled study; 66 adults aged 40-65 years	Oral administration: 2 capsules/day for 60 days	the efficacy of NMN in terms of stimulation of NAD+ metabolism	Completed	India	2020
A verification study of safety evaluation of excessive ingestion of NMN-containing food in humans: a randomized, double-blind, placebo-controlled, parallel study	UMIN000043084		Double-blind, randomized, placebo-controlled study; 32 adults aged 20 – 65 years	Oral administration: NMN-containing food once a day for 4 weeks.	Physical examination, urinalysis, blood test	Completed	Japan	2021
Safety observation study for healthy individuals of intravenous administration of NMN	UMIN000047134		Open label, non-randomized, uncontrolled study; 10 healthy adults aged 20-70 years	Single intravenous administration of NMN	NAD+ levels and SIRT1 activation in blood	Completed	Japan	2021
To evaluate the efficacy and safety of NMN as an anti-ageing Supplement in middle aged and older (40-65 years) adults	NCT04823260		Double-blind, randomized, placebo-controlled study; 90 healthy adults aged 40-65 years	Oral administration: 300 mg/day and 600 mg/day for 60 days	Blood cellular NAD+/ NADH, six walking endurance test, SF-36 questionnaire, telomerase test results, BMI, biological age using ageing. Ai 3.0 calculator	Completed	India	2021
Safety and pharmacokinetics of nicotinamide mononucleotide (NMN) in healthy adults	NCT04910061		Open label, non-randomized, non-controlled, monocentre repeated-dose study; 24 healthy adults aged 18-65 years	Oral administration:400 mg/day for 29 days	Adverse events, body temperature, heart rate and blood pressure, complete blood count, C reactive protein, AST, ALT, bilirubin, GGT, alkaline phosphatase, creatinine, creatine kinase, sodium, potassium, chloride	Active, not recruiting	Canada	2021
Pharmacodynamics and tolerance of nicotinamide mononucleotide (NMN) in healthy adults	NCT04862338		Open-label, single-arm, single-center study; 20 healthy adults aged 30-60 years	Oral administration:400 mg/day for 28 days	NAD+ and NMN concentrations in whole blood, NAD+ metabolite concentrations in plasma and urine, adverse events, mitochondrial DNA ratio, blood glucose and lipid levels, transaminases (ASAT, ALAT, GGT) levels in blood, blood cell count; bilirubin, creatinine, and CPK levels in blood, blood ionogram, diastolic and systolic blood pressure, heart rate, weight, body composition	Active, not recruiting	France	2021
Effect of oral ingestion of NMN on blood NAD derivatives concentration	UMIN000047042		Open label, non-randomized, self-control study; 10 healthy adults aged 20-70 years	Oral administration:250 mg/day for 12 weeks	Blood NAD+ level	No longer recruiting	Japan	2022
The efficacy of NMN on different diseases
Trial Name	Registration number		Design	Dose and duration	Indicators	Status	Location	Registration time
Impact of NMN for diabetic patients with physical frailty-NMN clinical study	jRCTs051190002		Double-blind, randomized, placebo-controlled study; 16 diabetic patients aged ≥ 65 years	Oral administration:250mg for six months	Grip strength and walking speed, muscle strength and volume, physical function, frality measurement (J-CHS scale), homed blood pressure and pulse rate measurement, diabetic condition and nephropathy, diabetic retinopathy	Completed	Japan	2019
Exploratory study of anti-aging effects of supplement intake	UMIN000043598		Double-blind, randomized, placebo-controlled study; 60 patients aged 45-65 years	Oral administration:2 capsules of NMN-containing continuously for 4 weeks	Mitochondrial number (mtDNA / gDNA), sirt1 gene expression level (sirt1 mRNA / GAPDH mRNA); urinary 8-OHdG, urinary pentosidine, blood fatty acid fraction, blood e-NAMPT, saliva Sirt2, intestinal flora, oral flora	Completed	Japan	2021
Effect of exercise nutrition intervention on pre-diabetes patients	ChiCTR2000040222		Parallel, placebo- controlled study; 100 pre-diabetes patients aged 50-80 years	Oral administration:500 or 1000 mg/day	Complete biochemical examination, scale (Life style assessment scale, SF-36, SAS, SDS, GAD-7, PHQ-9), physical fitness (6-minute walk test, short physical performance battery, the Scale of ageing vigor in epidemiology), general information (height, weight, body composition, waist circumference, hip circumference, thigh circumference and blood pressure), noninvasive detection of vascular endothelial function	Recruiting	China	2020
Nicotinamide Mononucleotide in hypertensive patients	NCT04903210		Single-blind, randomized, parallel study; 20 hypertensive patients aged 18-65 years	Oral administration:400 mg/day for two months	Flow mediated dilation (FMD), brachial-ankle pulse wave velocity, blood pressure, PBMC NAD+ levels, sleep quality, adverse events	Recruiting	China	2021
Effect of NMN (nicotinamide mononucleotide) on polycystic ovary syndrome	NCT05305677		Double-blind, randomized, placebo-controlled study; 120 female patients aged 20-40 years	Oral administration:600mg/day for 8 weeks	Gut microbiota, metabolomics, glucose tolerance, homeostasis Model Assessment for Insulin Resistance (HOMA-IR) index, endocrine hormones, ovarian volume, follicle number, changes in blood NAD+ level, changes in BMI, changes in waist-to-hip ratio, changes in blood pressure	Recruiting	China	2022
Effect of NMN (nicotinamide mononucleotide) on diminished ovarian reserve (including premature ovarian insufficiency)	NCT05485610		Double-blind, randomized, placebo-controlled study; 220 female patients aged 20-40 years	Oral administration:600mg/day for 3 months	Gut microbiota composition, blood sugar level, fasting insulin, Endocrine hormones including AMH, ovarian volume, follicle number, blood NAD+ level, changes in NAD-related metabolites in urine	Not yet recruiting	China	2022
The anti-ageing effects of NMN on skin
Trial Name	Registration number		Design	Dose and duration	Indicators	Status	Location	Registration time
Anti-wrinkle effect of beauty essence containing human stem cell components and NMN: single blinded study	UMIN000042828		Single-blinded, randomized study; 12 healthy female aged 35-59 years	External application: Only one side of the face, using test article for 4 consecutive weeks	Wrinkle grade	Completed	Japan	2020
Anti-ageing efficacy of a cosmetic formulation containing NMN (2%) versus placebo	NCT04685096		Cohort study; 89 healthy female aged 40-65	External application: twice daily application of creme containing 2% NMN for 55 days	Wrinkles, eye bags, dark circles, relaxed features, skin texture, moisture, puffiness, brightness, youth, swelling, wrinkling, radiance and tone	Completed	United States and China	2020
the effects of a longevity supplement on aging and photoaging	NCT05262036		Open label, randomized, placebo-controlled study; 38 adults aged 35-70 years	Oral administration:mixture (powder) of NOVOS Core (12 ingredients) + NOVOS boost (NMN) daily for 6 months	Fine lines and wrinkles, facial redness, pigmentation and texture, skin hydration and elasticity, fasting lipids, hemoglobin A1c, ultra-sensitive CRP, blood pressure, mental health survey, subjective skin health survey, epigenetic signals	Not yet recruiting	United States	2022
Other
Trial Name	Registration number		Design	Dose and duration	Indicators	Status	Location	Registration time
Effect of long-term oral administration of nicotinamide mononucleotide (NMN) on human health	UMIN000025739		Parallel, randomized study; 20 healthy adults aged 50-70 years	Oral administration: 100 mg/day and 200 mg/day for 24 weeks	Serum or plasma concentration of the following parameters:Thyroid-stimulating hormone (TSH), free triiodothyronine (Free T3), free thyroxine (Free T4), growth hormone (GH), prolactin, parathyroid hormone (PTH), dehydroepiandrosterone sulfate (DHEA-S), estradiol (E2), testosterone, calcitonin, adrenocorticotropic hormone (ACTH), arginine vasopressin (AVP), cortisol, aldosterone, ghrelin, inhibin, melatonin; mitochondria activity in leucocyte, Sirt1 and Sirt2 gene expressions in leucocyte	Completed	Japan	2017
Exploratory study on the health promotion effect of intake NMN-containing supplement	UMIN000041677		Single arm, non-randomized study; 30 healthy male aged 40-65 years	Oral administration:1 capsule of NMN-containing supplement at breakfast daily for four weeks	Oxidative stress level, 8-OHdG in semen, quantity, count and concentration of Sperm, testosterone, creatine, spermine and zinc in semen, questionnaire (life style)	Completed	Japan	2020
A study evaluating various aging markers by taking NMN supplements	UMIN000045347		Open label, non-randomized, uncontrolled study; 15 healthy female aged 50-80 years	Oral administration:300 mg/day for 8 weeks	IGF-1, DHEA-s, free testosterone, cortisol, TSH, FT3, FT4, Insulin, NMN, NAD, Sirt1 mRNA, immunity judgment test, measurement of fluorescent AGEs (AGE reader), skin VAS questionnaire	Completed	Japan	2021
Effect of NMN supplementation on organ system biology (van)	NCT04571008		Randomized, placebo-controlled study; 56 healthy adults aged 45-75 years	Oral administration:300 mg/day for 16 weeks	Muscle insulin sensitivity, glucose tolerance	Recruiting	United States	2020
Effect of NMN on muscle recovery and physical capacity in healthy volunteers with moderate Physical activity	NCT04664361		Double-blind, randomized, placebo-controlled study; 150 healthy male aged 20-49 years	Oral administration:250 mg/day and 500 mg/day for 38 days	Muscle recovery, physical capacity, cardiorespiratory recovery, blood lactate levels, perception of the intensity of post-exercise muscle pain (cramps), body composition, blood NAD+ levels	Recruiting	France	2021
Effect of oral NAD+ precursors administration on blood NAD+ concentration in healthy adults (NICO)	NCT05517122		Randomized, parallel-study; 68 healthy adults aged 18-50 years	Oral administration: NAM 500 mg/day, NR 1000 mg/day, NMN 1000 mg/day, for 14 days	NAD+ level in whole blood, for each NAD+ precursor	Recruiting	Switzerland	2022

Preventive and Therapeutic Effects of NMN and NR: Unveiling the Potential

The exploration of Nicotinamide Mononucleotide (NMN) and Nicotinamide Riboside (NR) in the realm of preventive and therapeutic medicine represents a significant leap forward from traditional NAD+ biosynthesis precursors like tryptophan, nicotinamide (NAM), and nicotinic acid (NA). This journey marks a transition from combating pellagra—a condition historically treated with these precursors—to addressing a spectrum of modern health challenges including metabolic disorders, neurodegenerative diseases, and age-related decline.

From Pellagra to Modern-Day Maladies

Historically, the treatment for pellagra focused on mitigating symptoms through dietary supplementation of NAD+ precursors. However, each precursor comes with its limitations. Tryptophan’s involvement in various metabolic pathways limits its efficacy in sustaining NAD+ levels. NA, despite its cholesterol-lowering benefits, is marred by side effects like skin flushing. NAM, while effective in boosting NAD+ levels, inhibits sirtuin and PARP activities and, at high doses, can deplete the cellular methyl pool, potentially altering gene expression and protein function.

NMN and NR: A New Era of NAD+ Therapy

The pharmacokinetics of NMN and NR offer intriguing insights. NMN is retained longer in the body compared to NAM, hinting at a potentially more sustained elevation of NAD+ levels. The mechanism by which NR increases NAD+ levels more effectively than NAM or NA remains a subject of ongoing research, underscoring the need for direct comparisons to fully understand the unique benefits of each precursor.

NMN has emerged as a promising nutraceutical for preventing age-related physiological decline, demonstrating efficacy in improving conditions like diabetes and Alzheimer’s disease, enhancing aerobic capacity, and offering cardio- and vasoprotective actions. Its role in inhibiting inflammation and oxidative stress further supports its therapeutic potential.

NR has shown remarkable protective effects in models of Alzheimer’s disease, improving cognitive function, synaptic plasticity, and reducing neuroinflammation and neuronal apoptosis. Additionally, NR’s ability to ameliorate metabolic disorders, such as obesity and NAFLD, by enhancing energy expenditure and mitochondrial content, showcases its versatility as a therapeutic agent.

The Underlying Mechanisms

The therapeutic prowess of NMN and NR is attributed primarily to their capacity to elevate NAD+ levels, thereby enabling the activities of sirtuins and their downstream targets. This mechanism highlights the central role of NAD+ in cellular metabolism, stress responses, and repair processes. By bolstering NAD+ levels, NMN and NR not only counteract the physiological impacts of aging but also offer a proactive approach to managing and preventing a broad array of diseases.

Looking Forward

The exploration of NMN and NR’s preventive and therapeutic effects is a testament to the evolving understanding of NAD+ biology and its implications for human health. As research progresses, the potential of these compounds to revolutionize treatment paradigms across various health conditions becomes increasingly apparent. With their unique pharmacokinetic profiles and broad spectrum of health benefits, NMN and NR stand at the forefront of a new era in medical science, promising a future where age-related decline and chronic diseases may be effectively managed or even prevented through targeted nutritional supplementation.

Exploring the Synergistic Potential of Resveratrol and Pterostilbene in Anti-Aging Nutraceutical Interventions

In the quest for effective anti-aging strategies, the spotlight increasingly falls on nutraceutical compounds like resveratrol and pterostilbene. These non-flavonoid phenolic stilbenes, abundant in grapes and berries, have garnered significant attention for their potential to combat age-related disorders and promote longevity. However, their efficacy and mechanisms of action remain subjects of debate and scrutiny. This article provides a detailed analysis of the synergistic effects and therapeutic potential of resveratrol and pterostilbene in anti-aging interventions.

Resveratrol and pterostilbene have emerged as two of the most extensively studied nutraceuticals, lauded for their anti-inflammatory and antioxidant properties. Despite being context-dependent and yielding mixed results in preclinical models, clinical analyses have established their safety and bioavailability, paving the way for further exploration of their therapeutic benefits. Both compounds have shown promise in extending lifespan and improving various health parameters, albeit through different mechanisms.

Pterostilbene, in particular, stands out for its remarkable bioavailability and longevity-inducing effects. By activating longevity-associated genes, such as SIRT2, pterostilbene demonstrates the potential to enhance antioxidant function and combat age-related disorders. Its superior bioavailability compared to resveratrol positions it as a promising candidate for synergistic interventions aimed at maximizing NAD+ levels and promoting overall health.

Moreover, the combination of resveratrol and pterostilbene holds immense potential in modulating key pathways associated with aging and disease. By upregulating endogenous antioxidant enzymes and modulating inflammatory mediators, these compounds offer multifaceted protection against oxidative stress and inflammation. Co-administration of resveratrol and pterostilbene may further maximize their individual benefits, given their complementary mechanisms of action and synergistic effects.

Resveratrol, known for its association with the SIRT1 pathway, exhibits diverse health benefits ranging from neuroprotection to anti-cancer properties. While its direct role in SIRT1 activation remains debated, resveratrol’s ability to mimic the effects of caloric restriction and extend lifespan underscores its potential as an age-related metabolic modulator. Furthermore, resveratrol shows promise in improving cognitive function, cardiovascular health, and insulin sensitivity, offering comprehensive anti-aging benefits.

The combination of resveratrol and pterostilbene, supplemented with NMN, presents a cleverly tailored approach to anti-aging intervention. By synergistically enhancing NAD+ levels and promoting longevity-associated pathways, this combination strategy holds promise in delaying or even reversing the signs of aging. Clinical studies have demonstrated the efficacy of these combinations in increasing NAD+ levels and improving cellular protection, further supporting their potential in anti-aging interventions.

Resveratrol and pterostilbene represent promising candidates for nutraceutical interventions aimed at combating age-related decline. Their synergistic effects, when combined with NMN supplementation, offer a multifaceted approach to promoting longevity and preserving healthspan. As research in this field progresses, further insights into the mechanisms underlying these compounds’ therapeutic effects will undoubtedly pave the way for more effective and personalized anti-aging strategies.

Coenzyme Q10 (CoQ10), also known as ubiquinol, plays a crucial role in mitochondrial function, participating in the electron transport chain. Its significance in cellular energy production and antioxidant defense mechanisms makes it a compelling target for therapeutic interventions, particularly in the context of aging and age-related diseases. This article continues the exploration of nutraceutical interventions by focusing on the potential synergistic effects of CoQ10 supplementation alongside NAD+ precursors.

Low levels of CoQ10 have been linked to various diseases, including neurodegenerative disorders, diabetes, cancer, fibrosis, and cardiovascular diseases. Supplementation with CoQ10 aims to restore antioxidant activity, thereby ameliorating homeostatic disruptions associated with these conditions. Clinical studies have demonstrated the cardiovascular benefits of CoQ10 supplementation, including improvements in hyperglycemia, hypertension, oxidative stress, and the risk of cardiac events.

Furthermore, CoQ10 levels decline sharply with aging, highlighting its importance in age-related health maintenance. Enhanced longevity has been associated with higher mitochondrial levels of CoQ10, emphasizing the potential of supplementation in mitigating age-related diseases. Skeletal muscle integrity, inflammatory markers, and lipid integrity can all be positively influenced by CoQ10 supplementation, underscoring its multifaceted benefits in aging populations.

Importantly, CoQ10 and NAD+ supplementation demonstrate synergistic effects, particularly in conditions characterized by inflammation and oxidative stress, such as chronic fatigue syndrome (CFS). Studies have shown improvements in fatigue and metabolic parameters, along with an increase in NAD+/NADH levels, ATP production, and antioxidant defenses. These findings suggest a complementary relationship between CoQ10 and NAD+ in supporting cellular function and mitigating age-related decline.

The antioxidant, anti-inflammatory, and age-related effects of CoQ10 position it as a valuable component of comprehensive anti-aging strategies. Further research is warranted to elucidate the synergistic effects of combining NAD+ precursors with CoQ10 supplementation. By harnessing the potential of these compounds in tandem, there exists a promising opportunity to combat the biological processes of aging and promote overall health and longevity.

Betaine, a derivative of the beetroot plant, is a compound with osmoprotectant and anti-inflammatory properties. It serves as one of the primary methyl group donors involved in DNA methylation, playing a crucial role in regulating gene expression. Betaine has been shown to suppress inflammatory markers such as TNF-α, COX2, and NF-kB activity, thereby contributing to the postponement of aging-related pathologies. Interestingly, the degradation of NAD+ precursors, particularly NAM, can impact betaine levels, potentially compromising the availability of methyl donors essential for proper methylation health and function. Therefore, concurrent supplementation of NAD+ precursors alongside betaine may help maintain optimal methylation levels, mitigating age-related changes in gene expression.

Moving on to flavonoids, fisetin and quercetin stand out for their potent anti-cancer properties and senolytic activity. Fisetin, in particular, has shown promise as a geroprotective agent, extending lifespan and improving tissue homeostasis in experimental models. Clinical trials are currently underway to investigate its effects on inflammation and frailty in the elderly. Quercetin, on the other hand, exhibits a range of health benefits, including cardiovascular protection and anti-inflammatory effects. It also acts as a potent CD38 inhibitor, preserving NAD+ levels and protecting against metabolic disorders. Luteolin and apigenin, two other flavonoids, demonstrate anti-inflammatory, antioxidant, and anti-carcinogenic properties. Apigenin, in particular, is notable for its ability to inhibit CD38, leading to increased NAD+ availability and reduced cellular senescence. These flavonoids play a crucial role in the modulation of the NAD+/SIRT1/CD38 axis, contributing to overall longevity and healthspan.

Carotenoids, such as astaxanthin and lycopene, are powerful antioxidants with numerous health benefits. Astaxanthin, in particular, has been shown to upregulate SIRT1 expression, offering protection against oxidative stress and age-related pathologies. Studies in zebrafish have demonstrated its ability to increase NAD+ levels, suggesting its potential as a supplement to boost NAD+ availability in humans. Similarly, lycopene has shown promising results in improving physical performance and reversing insulin resistance in age-related vascular decline models. Combined therapy with NMN and lycopene has exhibited significant improvements in cognitive function and antioxidant defenses, highlighting its potential in combating age-related changes.

Nutraceutical interventions, including betaine, flavonoids, and carotenoids, offer promising avenues for promoting healthy aging and extending healthspan. Their diverse mechanisms of action, from modulating gene expression to enhancing antioxidant defenses and supporting mitochondrial function, make them valuable components of comprehensive anti-aging strategies. Further research and clinical trials will help elucidate the full potential of these compounds in promoting longevity and improving overall quality of life.

Figure-  Hypothesized model of supplementing NAD+ precursors with other NAD+ enhancing geroprotectors. In addition to NAD+ precursors to raise NAD+ levels and enhance SIRT1 activity, stilbenes are able to support NAD+ levels and further activate SIRT1. Many flavonoids retain senolytic and CD38-inhibitory activity and can further innervate NAD+ stores. Curcumin and carotenoids retain similar properties in addition to SIRT1 activation. This interacting web of support may result in higher NAD+ stores than precursor-alone administration, producing longevity-promoting transcriptional benefits.

Curcumin, a well-known compound found in turmeric, has emerged as a potent senolytic agent with potential benefits for age-related pathologies. It exhibits modulatory effects on longevity-related pathways, including mTOR and FoxO, and has been implicated in improving senescence in various age-related conditions. Curcumin has also shown promise in neurodegenerative diseases by upregulating SIRT1 and in cardiovascular health by activating AMPK. Its anti-cancer properties have been demonstrated in experimental models of head and neck squamous cell carcinoma, where it inhibits cancer cell migration and angiogenesis. Human studies have indicated that curcumin supplementation improves antioxidant capacity and aerobic performance, potentially through its interaction with SIRT3. However, further research is needed to explore the synergistic effects of curcumin with NAD+ boosting molecules in combination therapies.

Alpha-ketoglutarate (aKG) is a metabolic intermediate crucial for the Krebs cycle and is implicated in the aging process. It inhibits the TOR pathway and ATP synthase, extending lifespan in model organisms like C. elegans. Recent pilot clinical trials involving a novel formulation of aKG have shown promising results in reducing the biological age of participants. While aKG offers metabolic and antioxidant benefits, its interaction with NAD+ remains poorly understood and warrants further investigation.

Epigallocatechin gallate (EGCG), a polyphenol found in green tea, possesses neuroprotective, antioxidant, and anti-inflammatory properties. Studies have shown that EGCG can increase lifespan in rats under oxidative stress conditions. However, its role in modulating SIRT1 is unclear, with some studies indicating upregulation while others suggest downregulation, especially in cancer cells. The effects of EGCG on the NAD+/NADH ratio and its potential interaction with NAD+ boosting molecules need to be explored further to understand its mechanism of action in promoting longevity and healthspan.

Compounds like curcumin, alpha-ketoglutarate, and epigallocatechin gallate offer promising avenues for combating aging-related processes and promoting overall health. Their diverse mechanisms of action, from modulating longevity pathways to enhancing antioxidant defenses, underscore their potential as components of comprehensive anti-aging strategies. Further research and clinical trials are necessary to elucidate their full therapeutic potential and optimize their use in promoting healthy aging.

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Resource :

• https://www.mdpi.com/2072-6643/15/2/445
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10171153/
• https://www.nature.com/articles/s41392-023-01577-3
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10240123/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10240123/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751327/
• https://www.sciencedirect.com/science/article/pii/S2161831323013595

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