Effects of hyperglycemia on oxidative stress and antioxidant potential in patients with type 2 diabetes

Many in vitro studies have suggested that oxidative stress induced by hyperglycemic conditions has a pivotal role in the pathogenesis of vascular complications in diabetics. This study intended to evaluate the oxidative stress and antioxidant potential in patients with type 2 diabetes mellitus (DM), and to clarify the relation between oxidative stress and metabolic derangements including chronic hyperglycemia. We measured the levels of derivatives of reactive oxidative metabolites (ROM) and biological antioxidant potential (BAP) in 59 patients with type 2 DM and 10 healthy controls. Diabetic patients showed a significant increase in ROM levels and a decrease in adjusted BAP/ROM ratios compared with those of control. But no differences were found in BAP levels between the two groups. ROM levels were found to positively correlate with HbA1c, plasma glucose, and waist size, and adjusted BAP/ROM ratios negatively correlated with HbA1c, plasma glucose, waist size, and serum triglycerides. Stepwise multiple regression analysis indicated that HbA1c and waist size were independent factors contributing to the elevated ROM levels. The ROM level in patients with type 2 DM with metabolic syndrome was significantly higher than that in patients without metabolic syndrome. Glycemic control with glimepiride or miglitol for 3 months reduced ROM levels significantly by 9%. These results clearly demonstrate that glycemic control and visceral obesity are independently associated with an increasing oxidative stress in patients with type 2 DM.