Aging, or senescence, is generally viewed as a necessary component of human life. Gerontology encompasses the study of aging processes and aging effects, and one intriguing branch of gerontology seeks to understand the biological processes that facilitate aging. Many theories of aging exist, and more than a few consider the role of a tiny cellular structure that many individuals likely are not even aware of: the mitochondion. This structure aids in many cell functions, and disturbances in any of the following functions could potentially induce aging: cellular division, cell signaling, and cell death. Perhaps the most well-known mitochondrial theory of aging concerns the impact of unstable oxygen molecules called free radicals on mitochondrial structures.
Mitochondria might be thought of as cells’ energy factories. Each human cell possesses anywhere from dozens to thousands of of these factories. Every tiny mitochondrion works to produce energy that powers various processes, from breathing to walking. They create this energy by breaking down food molecules into electrons that are then stored in adenosine triphosphate (ATP) energy bundles.
The mitochondrial structures have a different kind of deoxyribonucleic acid (DNA) than other cellular parts. The DNA contained in mitochondria is known as mitochondrial DNA (mDNA), and it does not contain the same level of protection as traditional DNA. Both enzymes and proteins called histones typically protect DNA from any major damage, but mDNA lacks these substances. Therefore, as a mitochondrion sustains damage, so do the energy processes that dictate so much of human capability. Cellular degeneration is thus one of the more significant approaches to mitochondrial theories of aging.
A closely associated subdivision of the cell degeneration mitochondrial theory of aging is the free radicals theory. Most molecules in the body operate in a stable and predictable manner, yet instability can still arise, particularly in the body’s oxygen molecules. Once oxygen molecules lose their order, they are dubbed free radicals. These chaotic particles can wreak severe havoc on fragile areas, and they thrive in the mitochondrial areas, since each mitochondrion performs respiration for cells. Due to their lack of protection, the mitochondrial DNA strands are among the most vulnerable for a free radical attack.
Mitochondria have other key functions aside from energy production, and each of these functions can serve as a lens into mitochondrial theories of aging. For example, the substances are an important cornerstone of cellular division, by which one cell splits into multiple new cells. This process helps replace old and worn cells, so if cellular division slows or stops, then the effects of the proliferation of old cells will be felt both inside and outside the body. Dysfunctional mitochondria will greatly impact cell division capabilities.
On a related note, these structures may also largely dictate programmed cell death: a process where cells essentially self-destruct. Different processes that might facilitate this suicide include fragmenting DNA, mutating cell membranes, and breaking down and shrinking the cell’s nucleus. If programmed cell death is manifested through aging as many researchers believe, then the mitochondrion’s role in facilitating programmed cell death adds yet another aspect to mitochondrial theories of aging.
Cells can communicate with each other in large part because of mitochondria as well. Mitochondria aid in cell signaling, where cells transmit impulses of information relating to equilibrium, tissue repair, and other processes. Sustained mitochondrial damage can cause errors in this information processing. Researchers focused on error theories blame this outcome for many diseases. Aging theorists may also attribute faulty cell signaling to aging processes.
Many factors can influence a mitochondrion’s health and functioning. As mentioned earlier, the free radical theory provides one explanation for faulty mitochondria. Cellular mutations can inflict similar damage, and these mutations may result from diet, inherited conditions, or just simple chance. Sometimes, the damage occurs from natural wear and tear over time. Since most skin cells only have one mitochondrion to sustain them over a lifespan, it is perhaps unsurprising that the skin is one of the most visible areas for aging effects.
Research into the mitochondrial theories of aging has led to some remedy recommendations. For one, B complex vitamins are believed to alleviate and correct some of the enzyme defections caused by mitochondrial damage. In addition, the substances lipoic acid and alcar may redirect the brain’s energy-making activities toward mitochondria when these processes have been otherwise hindered.