Age and sex differences in human skeletal muscle: Role of reactive oxygen species

Previous studies, conducted on experimental animals, have indicated that re active oxygen species (ROS) are involved in the aging process. The objectiv e of this work was to study the relationship between oxidative damage and h uman skeletal muscle aging, measuring the activity of the main antioxidant enzymes superoxide dismutase (total and MnSOD), glutathione peroxidase (GPx ) and catalase in the skeletal muscle of men and women in the age groups: y oung (17-40 years), adult (41-65 years) and aged (66-91 years). We also mea sured glutathione and glutathione disulfide (GSH and GSSG) levels and the r edox index; lipid peroxidation and protein carbonyl content. Total SOD acti vity was lower in the 66-91 year-old vs. the 17-40 year-old men; MnSOD acti vity was significantly greater in 66-91 year-old vs. 17-40 year-old women. GPx activity remained unchanged. The activity of catalase was lower in adul ts than in young men but higher in the aged. We observed no changes in GSH levels and significantly higher GSSG levels only in aged men vs. adult men, and a significant decrease in aged women vs. aged men. The protein carbony l content increased significantly in the 41-65 and 66-91 year-old vs. the 1 7-40 year-old men. Finally, young women have lower lipid peroxidation level s than young men. Significantly higher lipid peroxidation levels were obser ved in aged men vs, both young and adult men, and the same trend was notice d for women. We conclude that oxidative damage may play a crucial role in t he decline of functional activity in human skeletal muscle with normal agin g in both sexes; and that men appear to be more subject to oxidative stress than women.