Influence of uric acid and γ-glutamyltransferase on total antioxidant capacity and oxidative stress in patients with metabolic syndrome

Objective Metabolic syndrome (MS) is a cluster of risk factors for cardiovascular disease related mainly to insulin resistance, but also to oxidative stress. Uric acid and γ-glutamyltransferase (GGT) levels are also associated with MS and oxidative stress. This study was undertaken to assess the role of GGT and uric acid in adult patients with MS and its relation to oxidative stress and antioxidant defense. Methods A total of 88 adults (67 with MS and 21 controls) were selected among ambulatory patients and workers of the University Hospital of Londrina, Paraná, Brazil. Oxidative stress was assessed by determination of thiobarbituric acid–reactive substances and tert-butyl hydroperoxide–initiated chemiluminescence and antioxidant defenses by total radical-trapping antioxidant parameter. Results The MS group presented higher significant results (P < 0.0001) than the control group in all parameters of MS and uric acid and GGT levels and significant lower values (P < 0.0001) in high-density lipoprotein cholesterol levels. Thiobarbituric acid–reactive substances and total radical-trapping antioxidant parameter did not show statistically significant differences between groups. However, lipid hydroperoxides, evaluated by tert-butyl hydroperoxide–initiated chemiluminescence, showed higher significant results in the MS group (P = 0.045) than in the control group. Total antioxidant capacity did not decrease and thiobarbituric acid–reactive substances did not increase, probably due to increased uric acid (r = 0.239, P = 0.04) in the MS group. Conclusion The present study confirmed that GGT is a strong predictor of MS and that lipid peroxide measured by tert-butyl hydroperoxide–initiated chemiluminescence and GGT activity are reliable markers of oxidative stress in this syndrome.