Resistance exercise training decreases oxidative damage to DNA and increases cytochrome oxidase activity in older adults
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Regular resistance exercise increases muscle strength and induces muscle fibre hypertrophy in older adults. Although the underlying causes of aging remain unclear, like acute exercise, aging is associated with oxidative stress. In ageing, however, oxidative stress is closely associated with mitochondrial dysfunction as proposed by the mitochondrial theory of aging. The effect of regular resistance exercise upon mitochondrial function and oxidative stress in older adults is unknown. Twenty-eight older men and women (approximately 68.5+/-5.1 yr) performed whole-body resistance exercise training for 14 weeks. Muscle biopsies were taken before and 72 h following the last exercise bout from the vastus lateralis. Urine samples were also taken at the time of tissue collection. Resistance exercise training was associated with a decrease in 8-OHdG (Pre: 10783+/-5856, Post: 8897+/-4030 ng g(-1) creatinine; p<0.05). Protein content for CuZnSOD, MnSOD, and catalase, and enzyme activities for citrate synthase, mitochondrial ETC complex I+III, and complex II+III were not significantly different from baseline. However, complex IV activity was significantly higher after training as compared to before training (Pre: 2.2+/-0.5, Post: 2.9+/-0.9 micromol min(-1) g(-1)ww; p<0.05), as was the ratio of complex IV to complex I (Pre: 11.1+/-9.3, Post: 14.5+/-10.3; p<0.05). There were no apparent changes in normal mtDNA content or visible mtDNA deletion products as a function of training. These data suggest that regular resistance exercise decreases oxidative stress, but does not affect mtDNA. Moreover, increases in complex IV of the electron transport chain may have an indirect antioxidant effect in older adults and may improve function in daily activities.