Oxidative Stress in Older Adults: Effects of Fitness and Lifetime Physical Activity

Abstract

We previously demonstrated an age-related decline in the ability to constrain oxidative stress induced by forearm ischemia-reperfusion (I/R) and that this response could be improved with a dietary antioxidant intervention. Reactive oxygen species (ROS) at low concentrations are important in cell signaling with one important effect being upregulation of endogenous antioxidant enzymes. Therefore, repeated bouts of transient ROS production induced by acute exercise may also increase the ability to constrain oxidative stress and reduce oxidative damage. PURPOSE: This cross-sectional study tested the hypothesis that physical fitness and/or lifetime physical activity modulate the capacity to constrain acute oxidative stress and basal urinary excretion of oxidative damage products in healthy older men and women. METHODS: We compared 40 fit and 39 unfit men and women, ages 60-78y (mean age: 66 ± 5y). Fitness status was classified by measuring VO2 max and maximal leg power, using age- and gender appropriate norms. Lifetime physical activity (low, moderate, high) was assessed with the Historical Leisure Physical Activity (HLPA) questionnaire. The capacity to constrain oxidative stress was measured as plasma F2-isoprostane (F2isoP) responses to forearm I/R. Basal systemic levels of oxidative damage were assessed by measuring urinary excretion products of lipid and nucleic acid oxidation. RESULTS: VO2max, maximal leg power, and HLPA score were significantly different between groups (p<0.001). F2isoP levels were significantly increased in response to the I/R trial (p<0.001). Fit individuals who reported high lifetime physical activity had significantly lower I/R-induced F2isoP response compared to unfit individuals who reported low lifetime physical activity (p<0.05). Compared to the unfit, sedentary group, the fit active group also had significantly lower levels of urinary markers of oxidative damage (8-OHdG, 8-oxo-G; p<0.01, isoprostanes; p<0.05). CONCLUSION: These data indicate that higher physical fitness levels and lifetime physical activity of healthy older adults are associated with greater antioxidant defenses and lower oxidative damage to lipids and nucleic acids. Furthermore, these results suggest that "quality" (VO2 max) and "quantity" (lifetime physical activity) may both be important in determining antioxidant capacity as the differences were not as marked when analyzed by either factor alone. Supported by NIH Grant R03 AG030551.