Lipid peroxidation and activities of antioxidant enzymes in erythrocytes of patients with non-insulin dependent diabetes with or without diabetic nephropathy

Background. Diabetes is known to involve oxidative stress. However, data on oxidative stress in diabetic nephropathy is scant. The aim of this study was to examine lipid peroxidation and activities of key antioxidant enzymes in non-insulin dependent diabetes (NIDDM) without nephropathy and in those with diabetic nephropathy. Methods. Twenty-one NIDDM outpatients with obvious diabetic nephropathy (persistent proteinuria, over 0.5 g/day and albumin excretion over 200 mu g/min), 14 NIDDM outpatients with a long diabetic history but without hypertension and with normal urinary albumin excretion rate (<20 mu g/min) and 19 healthy persons were studied. Malondialdehyde (MDA) content of erythrocytes was quantified by HPLC according to Young et al. In erythrocytes, superoxide dismutase (SOD) activity was determined by the adrenaline method of Misra and Fridovich and catalase was estimated according to Beers and Sizer. Results. MDA content was significantly elevated in erythrocytes of NIDDM patients without nephropathy vs the control group and even higher in erythrocytes of NIDDM patients with diabetic nephropathy. SOD and catalase activities were lower in erythrocytes of NIDDM patients without nephropathy than in the control group and lowest in erythrocytes of NIDDM patients with nephropathy. Conclusions. These results confirm oxidative stress in erythrocytes of NIDDM patients with nephropathy. The intensity of oxidative stress appeared to be greater than in NIDDM patients without nephropathy.