In today's open access paper, researchers review the evidence for exercise to slow the aging of muscle tissue in part because it improves DNA repair mechanisms. How exactly damage to nuclear DNA contributes to aging beyond creating a raised risk of cancer remains a debated topic, despite recent conceptual advances. Nuclear DNA damage occurs constantly, near all of which is repaired. Yet the remaining damage largely occurs in genes that are not used or that are not all that important, and in cells with few replications remaining. Thus the ability to cause harmful alterations to cellular metabolism throughout a tissue was thought to be limited.
The first way in which nuclear DNA damage could meaningfully impact aging is via somatic mosaicism. When mutations occur in stem cells, those mutations spread slowly throughout a tissue over time via the descendants of the somatic daughter cells created by the mutated stem cells. A mosaic of combinations of mutations is established over years and decades, and there is at least some reasonably convincing evidence for this to increase the risk of a few age-related conditions.
More recently, researchers have provided evidence for the repeated repair of DNA double strand breaks, whether successful or not, and wherever the break occurred in the genome, to cause epigenetic changes characteristic of aging. These epigenetic changes alter the structure of nuclear DNA and thus the expression of genes. If support for this mechanism continues to accumulate, it provides a way for random molecular damage to DNA to produce the consistent outcome of harmful age-related epigenetic changes that is observed to occur in all cells.
In this second viewpoint, interventions such as exercise that are thought to slow aging in part by improving the operation of DNA repair mechanisms may not in fact be working as hypothesized. They may indeed be changing the operation of DNA repair, but the primary outcome of interest is to reduce the negative effects of double strand repair on the epigenetic control of nuclear DNA structure and gene expression, rather than improving the efficiency of DNA repair more generally.
Impact of exercise-induced DNA damage repair on age-related muscle weakness and sarcopenia
Sarcopenia, the progressive and generalized loss of skeletal muscle mass, strength, and function with aging, poses a significant public health challenge. A key contributor to sarcopenia is the accumulation of DNA damage, both nuclear and mitochondrial, coupled with a decline in DNA repair efficiency. This genomic instability, exacerbated by chronic oxidative stress and inflammation, impairs critical cellular processes including protein synthesis, mitochondrial function, and satellite cell regenerative capacity, ultimately leading to myofiber atrophy and weakness. Intriguingly, regular physical exercise, while acutely inducing transient DNA damage, concurrently activates and enhances DNA damage repair pathways, serving as a powerful physiological modulator of genomic integrity.
This review comprehensively explores the intricate interplay between exercise, DNA damage, and DNA repair in the context of age-related muscle decline. We delve into the molecular hallmarks of DNA damage (e.g., 8-OHdG, single and double strand breaks) and the major repair mechanisms (base excision repair, nucleotide excision repair, mismatch repair, homologous recombination, non-homologous end joining), detailing how acute exercise modalities (e.g., high-intensity interval training, resistance training) induce specific damage types primarily via reactive oxygen species. Crucially, we synthesize emerging evidence suggesting that chronic exercise training may upregulate the efficiency and capacity of DNA repair enzymes, particularly OGG1 in base excision repair, thereby mitigating the accumulation of deleterious genomic lesions. This exercise-induced enhancement of DNA repair directly contributes to maintaining mitochondrial health, preserving muscle stem cell function, and combating cellular senescence and inflammation, ultimately delaying or ameliorating sarcopenia and improving muscle functional outcomes in older adults.
View the full article at FightAging
