Oral Amino Acid Administration Decreases Oxidative Stress and Improves Brachial Reactivity in Elderly Individuals

Atherosclerosis is a major cause of death in elderly individuals. Endothelial dysfunction is recognized as a key early event in atherogenesis. In the present study, we evaluated the possible beneficial effect of amino acid administration on endothelial regulation in elderly subjects.A total of 25 healthy elderly subjects were administered essential amino acids (EAA) for 4 months. Before and after EAA administration, each subject underwent brachial reactivity investigation with and without an intra-arterial infusion of 4 micromol/min of N(G)-monomethyl-l-arginine (L-NMMA), an inhibitor of nitric oxide (NO) synthase.At baseline, age correlated with free plasma insulin growth factor-1 IGF-1 (r = -0.48; P.01), plasma Trolox equivalent antioxidant capacity (TEAC) (r = -0.40; P.04), and thiobarbituric acid-reactive substances (TBARS) (r = 0.42, P.04), and homeostasis model assessment (HOMA) index (r = 0.45, P.03), as well as with changes in diameter (r = -0.49, P.01) and flow (r = -0.43, P.03). Administration of EAA was associated with a significant increase in plasma TEAC (P.001) and decline in plasma TBARS (P.001) and with improvement in changes in diameter (7.15 +/-1.10 v 8.98 +/-1.80, P.001) and flow (5.6 +/-1.2 v 6.4 +/- 1.2, P.03). These latter two associations were independent of changes in HOMA index (P.04 for both correlations). The beneficial effects of EAA administration on brachial reactivity were partly attenuated by L-NMMA.Administration of EAA may improve brachial reactivity in elderly persons and may also protect against the development of atherosclerosis via the rise in plasma-free IGF-1 levels.