For over 100 years, scientists have sought to understand what links a person’s general intelligence, health and aging.
In a new study, a University of Missouri scientist suggests a model where mitochondria, or small energy producing parts of cells, could form the basis of this link.
This insight could provide valuable information to researchers studying various genetic and environmental influences and alternative therapies for age-related diseases, such as Alzheimer’s disease.
“There are a lot of hypotheses on what this link is, but no model to link them all together,” said David Geary, Curators Distinguished Professor of Psychological Sciences in the MU College of Arts and Science.
“Mitochondria produce cellular energy in the human body, and energy availability is the lowest common denominator needed for the functioning of all biological systems.
Mitochondria are thought to have originated from an ancient symbiosis that resulted when a nucleated cell engulfed an aerobic prokaryote.
The engulfed cell came to rely on the protective environment of the host cell, and, conversely, the host cell came to rely on the engulfed prokaryote for energy production.
Over time, the descendants of the engulfed prokaryote developed into mitochondria, and the work of these organelles – using oxygen to create energy – became critical to eukaryotic evolution
Modern mitochondria have striking similarities to some modern prokaryotes, even though they have diverged significantly since the ancient symbiotic event.
For example, the inner mitochondrial membrane contains electron transport proteins like the plasma membrane of prokaryotes, and mitochondria also have their own prokaryote-like circular genome.
One difference is that these organelles are thought to have lost most of the genes once carried by their prokaryotic ancestor. Although present-day mitochondria do synthesize a few of their own proteins, the vast majority of the proteins they require are now encoded in the nuclear genome.
What Is the Purpose of a Mitochondrial Membranes?
As previously mentioned, mitochondria contain two major membranes.
The outer mitochondrial membrane fully surrounds the inner membrane, with a small intermembrane space in between.
The outer membrane has many protein-based pores that are big enough to allow the passage of ions and molecules as large as a small protein.
In contrast, the inner membrane has much more restricted permeability, much like the plasma membrane of a cell.
The inner membrane is also loaded with proteins involved in electron transport and ATP synthesis.
This membrane surrounds the mitochondrial matrix, where the citric acid cycle produces the electrons that travel from one protein complex to the next in the inner membrane.
At the end of this electron transport chain, the final electron acceptor is oxygen, and this ultimately forms water (H20).
At the same time, the electron transport chain produces ATP. (This is why the the process is called oxidative phosphorylation.)
During electron transport, the participating protein complexes push protons from the matrix out to the intermembrane space.
This creates a concentration gradient of protons that another protein complex, called ATP synthase, uses to power synthesis of the energy carrier molecule ATP
Assembly pathways of the mitochondrial ATP synthase. (Upper) Assembly of human ATP synthase. The free F1domain or an F1–c-ring intermediate binds to the peripheral stalk. The supernumerary subunits e, g, and f associate and promote the insertion of ATP6 and ATP8. Addition of 6.8PL and DAPIT stabilizes the inserted ATP6/ATP8, leading to formation of the proton-conducting channel between ATP6 and the c-ring. The inhibitory protein IF1 that blocks ATP hydrolysis of uncoupled ATP synthase is released. (Lower) Assembly of yeast ATP synthase. The chaperones Atp11 and Atp12 promote formation of the F1 domain. The INAC binds to the c-ring, as well as to an assembly intermediate that contains Atp6, Atp8, the peripheral stalk, the F1 domain, and the maturation factors Atp10 and Atp23. The INAC thus supports proper association of the c-ring with Atp6 to allow formation of the proton-conducting channel. Subsequently, the supernumerary subunits are added to promote dimerization of the enzyme. (Inset) Structural subunits of human and yeast ATP synthase. Asterisks mark mitochondrially encoded subunits. IM, inner mitochondrial membrane; IMS, intermembrane space; OSCP, oligomycin sensitivity-conferring protein.
My model shows mitochondrial function might help explain the link between general intelligence, health and aging.”
Geary’s insight came as he was working on a way to better understand gender-specific vulnerabilities related to language and spatial abilities with certain prenatal and other stressors, which may also involve mitochondrial functioning.
Mitochondria produce ATP, or cellular energy.
They also respond to their environment, so Geary said habits such as regular exercise and a diet with fruits and vegetables, can promote healthy mitochondria.
“These systems are being used over and over again, and eventually their heavy use results in gradual decline,” Geary said. “Knowing this, we can help explain the parallel changes in cognition and health associated with aging.
Also with good mitochondrial function, the aging processes will occur much more slowly.
Mitochondria have been relatively overlooked in the past, but are now considered to relate to psychiatric health and neurological diseases.”
Geary said chronic stress can also damage mitochondria that can affect the whole body – such as the brain and the heart – simultaneously.
The study, “The spark of life and the unification of intelligence, health and aging,” was published in Current Directions in Psychological Science.
More information: David C. Geary, The Spark of Life and the Unification of Intelligence, Health, and Aging, Current Directions in Psychological Science (2019). DOI: 10.1177/0963721419829719
Journal information: Current Directions in Psychological Science
Provided by University of Missouri-Columbia
