Exercise increases the generation of reactive oxygen species that are potentially harmful. Regular exercise, on the contrary, has been reported to have a number of health benefits even late in life. The specific aim of this study was to explore effects of regular exercise on oxidative status of DNA in the aged animal model.
We found that 2 months of regular treadmill running of aged rats (21 month-old: human equivalent of approximately 50 years of age) significantly reduced 8-oxodG content to the level of young adult animals (11 month-old: human equivalent of approximately 30 years of age) in both nuclear and mitochondrial DNA of the liver. The levels in old animals were 2- and1.5-fold higher than those in young adults for the nucleus and mitochondria, respectively. The activity of the repair enzyme OGG1 was up-regulated significantly in the nucleus but not in mitochondria by the exercise.
To our knowledge, this is the first report demonstrating that regular exercise can significantly reduce oxidative damage to both nuclear and mitochondrial DNA. It is noted that such an effect was observed in nonmuscle tissue. We have previously reported that regular swimming exercise reduced oxidative protein damage in the brain of middle-aged rats. We suggest that these beneficial outcomes are due to hormetic effect of moderate oxidative stress and adaptation to stronger stresses, being a basis of health benefits of regular exercise in old age.
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