Effect of four-week metformin treatment on plasma and erythrocyte antioxidative defense enzymes in newly diagnosed obese patients with type 2 diabetes

The principal metabolic effect of metformin-an oral antihyperglycaemic agen t-is the improvement in the sensitivity of peripheral tissues and liver to insulin. This study examined the effect of metformin monotherapy on antioxi dative defence system activity in erythrocytes and plasma in diabetic patie nts. We studied the effect of metformin treatment on the activities of Cu, Zn-superoxide dismutase (EC 1. 15. 1. 1.), catalase (EC 1. 11. 1. 6.) and g lutathione peroxidase (EC 1. 11. 1. 9.) in relation to lipid peroxidation p roducts and reduced glutathione level in plasma and erythrocytes. In this s tudy we also examined erythrocytes' susceptibility to H2O2-induced oxidativ e stress during metformin therapy. Although metformin monotherapy ameliorat ed the imbalance between free radical-induced increase in lipid peroxidatio n (by reducing the MDA level in both erythrocytes and plasma) and decreased plasma and cellular antioxidant defences (by increasing the erythrocyte ac tivities of Cu, Zn, SOD, catalase and GSH level) and decreased erythrocyte susceptibility to oxidative stress, it had negligible effect to scavenge Fe ion-induced free radical generation in a phospholipid-liposome system.