Age-specific Effect of Acute Antioxidant Consumption on Endothelial Function

Abstract

There is convincing evidence of an overall increase in plasma free radical concentration with advancing age and a subsequent reduction in nitric oxide (NO) bioavailability which has been implicated in the age related decline in endothelial function. PURPOSE: Compare the effect of acute antioxidant (AO) consumption on FMD and reactive hyperemia in young and older subjects. METHODS: Flow-mediated vasodilation (FMD) and reactive hyperemia were evaluated following consumption of either placebo (PL) or an oral AO cocktail (Vitamin C, 1000mg; Vitamin E, 600 I.U.; Alpha-lipoic acid, 600 mg) in 64 (42 young, 25 ± 1 yrs; 22 older, 70 ± 2 yrs) healthy volunteers. Blood velocity and brachial artery (BA) diameter (ultrasound Doppler) were assessed before and after 5-min forearm circulatory arrest. Serum markers of lipid peroxidation (thiobarbituric acid reactive substances [TBARS]), total AO capacity (ferric reducing AO power [FRAP]), endogenous AO activity (superoxide dismutase [SOD] and catalase [CAT]), and vitamin C were determined. RESULTS: In the PL trial, an age-related reduction in BA vasodilation was evident (young: 7.4 ± 0.6 %; older: 4.6 ± 0.5 %). Following AO consumption, FMD improved in older subjects (PL: 4.6 ± 0.5 %; AO: 7.7 ± 0.7 %) but declined in the young (PL: 7.4 ± 0.6%; AO: 5.8 ± 0.6%). Reactive hyperemia was reduced with age (young: 23866 ± 2110 ml/min2; older: 19846 ± 1242 ml/min2), but AO administration did not alter the response in either group. Markers of oxidative stress (TBARS) increased with age (young: 1.51 ± 0.19 μM; older: 2.42 ± 0.17 μM), and AO administration significantly increased FRAP, SOD, CAT, and vitamin C in both groups. CONCLUSIONS: Together, these data demonstrate that AO consumption at over-the-counter doses acutely improves endothelial function in the elderly, while disrupting normal endothelium-dependent vasodilation in the young, and suggest that this age-related decline is due, at least in part, to elevated oxidative stress.