Lipoperoxidation and antioxidant capacity in patients with poorly controlled type 2 diabetes

Type 2 diabetes is a heterogeneous disease resulting from insulin resistance and/or from a beta-cell secretory defect. Hyperglycemia, which occurs during type 2 diabetes, causes disorders of oxidative-antioxidative balance in the cells, leading to increased free-radical formation. Reduced antioxidant capacity is supposed to be one of the causes of the occurrence of complications in type 2 diabetes. The aim of this study was to evaluate lipoperoxidation and plasma antioxidant status in patients with poorly controlled type 2 diabetes with or without complications. In this study, 15 patients with type 2 diabetes without complications and 11 patients with type 2 diabetes with complications were enrolled. The 'ferric-reducing ability of plasma' showed no differences between the two experimental groups. A small, nonsignificant, Superoxide dismutase (SOD) activity reduction was observed in patients with diabetes with complications when compared to those patients with diabetes without complications; on the contrary, we found increased lipoperoxidation in patients with diabetes with complications compared with those patients with diabetes without complications. We also observed a positive correlation between malondialdehyde levels and high density lipoprotein or vitamin E in all analyzed patients with type 2 diabetes. Data obtained from our study show that patients with poorly controlled type 2 diabetes with complications have higher lipoperoxidation than patients with complication-free diabetes, although a residual compensatory response to hyperglycemia-induced oxidative stress occurs.