Plasma antioxidant activity and cutaneous microvascular endothelial function in athletes and sedentary controls

Aging is associated with endothelial dysfunction in both conduit arteries and peripheral microcirculation. Furthermore, aging is associated with an increased susceptibility to free radical mediated tissue damage. The aim of this study was to assess the relationship between age, regular aerobic-endurance training, plasma antioxidant activity and microcirculatory skin blood flow in healthy individuals. Thirty-six male athletes (range: 22-74 years; VO2max 54.3 +/- 5.2 ml/kg/min) and 36 age-sex-matched sedentary controls (range: 20-75 years; VO2max 34.2 +/- 3.4 ml/kg/min) were studied. Each group was divided into a younger (<30 years) and an older (>60 years) subgroup. Hand and foot baseline and stimulated skin blood flow (SBF) was measured by laser-Doppler flowmetry. Plasma free radicals antioxidant capacity against both peroxyl and hydroxyl radicals was also evaluated as Total Oxyradical Scavenging Capacity (TOSC) units. Baseline SBFs were not significantly different between athletes and sedentary groups, while plasma TOSC values against peroxyl radicals (18.4 +/- 3.1 vs. 13.8.0 +/- 3.4 units/ml, P < 0.001) and hydroxyl radicals (8.7 +/- 2.5 vs 4.9 +/- 2.3 units/ml, P <0.001) was higher in athletes. Hand SBF after heating and ischemia and foot SBF after heating were higher in athletes (P <0.0001) than in the sedentary group. In the sedentary groups, the lowest tertile of age had higher plasma TOSC values than the highest tertile of age (ROO- 18.2 +/- 2.2 vs 8.8 +/- 1.4 units/ml; HO- 9.2 +/- 1.3 vs 3.7 +/- 0.5 units/ml, P < 0.001). Among athletes, the lowest and the highest tertile of age did not show significantly different plasma TOSC (young: ROO- 20.3 +/- 1.5 and HO-: 9.7 +/- 1.4 units/ml; older: ROO-: 17.1 +/- 1.3 and HO-: 9.0 +/- 0.8 units/ml, n.s.). Resting SBF was similar in all the subgroups; stimulated SBFs were lower in both subgroups of untrained respect to trained individuals (P <0.001). In the sedentary subjects, SBF was inversely related to age (r = -0.63; P <0.0001) and directly related to TOSC against peroxyl (r = 0.59, P <0.001) and hydroxyl radicals (r = 0.47, P <0.01). In athletes SBF was related only to VO2max (r = 0.36; P <0.05) and TOSC vs ROO. (r = 0.41, P <0.01). In conclusion, these results suggest that regular physical activity is associated with a better microvascular endothelial function in older athletes probably due to increased antioxidant defenses.