Oxidative stress and nitric oxide related parameters in type II diabetes mellitus: effects of glycemic control

Objectives: The aim of this study is to investigate the status of oxidative stress and nitric oxide related parameters in type II diabetes mellitus (D M) patients in which heart disease, atherosclerosis, retinopathy, and nephr opathy commonly occur, and also to determine the effect of glycemic control on these parameters. Design and methods: Erythrocyte copper zinc-superoxide dismutase (CuZn-SOD) , erythrocyte and plasma selenium dependent glutathione peroxidase (Se-GPx) , erythrocyte catalase (CAT) activities, erythrocyte and plasma thiobarbitu ric acid reactive substances (TBARS) levels; nitrite/nitrate (NO2-/NO3-), c yclic guanosine monophosphate (cGMP) and nitrotyrosine levels in plasma of type II DM patients were measured. Results: Erythrocyte CuZn-SOD activities in type II DM were significantly h igher than those of the control subjects (p < 0.05). TEARS levels in type I I DM were significantly higher than the control subjects (p < 0.001). Plasm a NO2-/NO3- levels in type II DM patients both during poor glycemic control and after three months of oral antidiabetic treatment were significantly h igher than those of the control subjects (p < 0.001). Plasma cGMP levels in type II DM patients during poor glycemic control were significantly lower than those of control subjects (p < 0.001). Conclusion: These results indicate that oxidative status and nitric oxide m etabolism are affected in type II DM patients. We found high CnZn-SOD activ ity in type II DM patients. This increased activity could not protect the p atients against the reactive oxygen species (ROS), since lipid peroxidation (defined by erythrocyte and plasma TEARS levels) still occurs in DM patien ts. After the therapy with oral antidiabetic agents for three months, eryth rocyte SE-GPx and CAT activities were found to be decreased below the contr ol values. Our results suggested that the low cGMP levels in the study may be a good marker of endothelium dysfunction in DM. (C) 2001 The Canadian So ciety of Clinical Chemists. All rights reserved.