Lipid peroxidation and antioxidant enzyme activities in patients with type1 diabetes mellitus

To evaluate oxidative stress in type I diabetes mellitus, two antioxidant e nzymes in erythrocytes, copper-zinc superoxide dismutase (SOD EC 1.15.1.1.) and seleno-dependent glutathione peroxidase (GSH-Px; EC 1.11.19), and two indexes of peroxidation in plasma, thiobarbituric acid reactive substances (TBARS) and organic hydroperoxides (OHP), were measured in 118 patients wit h insulin-dependent diabetes mellitus (IDDM), classified in accordance with the presence or absence of vascular complications and the degree of metabo lic control established by the HbA1c level. Ninety healthy subjects made up the control group. According to our results, plasmatic TBARS and OHP conce ntrations are significantly higher in diabetics than in controls, and these differences are accentuated in diabetic people with vascular disorders. Th e GSH-Px activity was significantly reduced in diabetic patients with poor and medium metabolic control in relation to the control group, regardless o f the existence or absence of vascular disorders. No differences in SOD act ivity between diabetic and control groups were found. A significant positiv e correlation between TEARS and HPO (r=0.683, p<0.001) was found in both th e control and diabetic groups. Among the lipid parameters studied, there we re only significantly positive correlations between TEARS and total cholest erol; TEARS and tryglicerides; OHP and total cholesterol and OHP and trygli cerides. Positive correlations between TEARS and HbA1c and between OHP and and HbA(1c), and negative correlations between GSH-Px and HbA(1c) and betwe en SOD and HbA(1c) were also found. The multiple regression analysis shows that TEARS and HPO correlate negatively with GSH-Px. There was no significa nt correlation with SOD.