Oxidative stress in the metabolic syndrome

The metabolic syndrome represents a cluster of several risk factors for atherosclerosis that increases the risk of future cardiovascular events. In this study, we evaluated whether oxidative stress is increased in subjects with the metabolic syndrome. We studied 100 subjects (50 men and 50 women) with the metabolic syndrome, as defined by the Adult Treatment Panel III, and 50 (25 men and 25 women) matched subjects without the syndrome. Insulin sensitivity was assessed with the homeostasis model assessment (HOMA) methods; endothelium-dependent flow-mediated vasodilation (FMD) was evaluated in the right brachial artery with a high-resolution ultrasound machine; oxidative stress was assessed by measuring the circulating levels of nitrotyrosine (NT), considered a good marker for the formation of endogenous peroxynitrite. Compared with control subjects, patients with the metabolic syndrome had greater waist circumference, higher HOMA and systolic pressure values, higher triglyceride and lower HDL-cholesterol levels. NT levels were higher (0.44 +/- 0.12 mu mol/l, mean +/- SD) while FMD was lower [7.3 (4.4/9.6), median and interquartile range] in subjects with the metabolic syndrome as compared with control subjects [0.27 +/- 0.08 and 11.8 (8.6/14.9), respectively, p < 0.001]. There was an increase in NT levels and HOMA score as the number of components of the metabolic syndrome increased. NT levels were associated with waist circumference (r=0.38, p=0.01), triglycerides (r=0.32, p < 0.02), systolic blood pressure (r=0.21, p < 0.05) and fasting glucose (r=0.24, p < 0.05). The oxidative stress that accompanies the metabolic syndrome is associated with both insulin resistance and endothelial dysfunction, providing a connection which is highly deleterious for vascular functions.