REDUCTION OF ACTIVITY, BUT NO DECREASE IN CONCENTRATION, OF ERYTHROCYTE CU,ZN-SUPEROXIDE DISMUTASE BY HYPERGLYCEMIA IN DIABETIC-PATIENTS

Cu,Zn-superoxide dismutase(SOD) activity in erythrocytes is affected b y various diseases, including diabetes mellitus (DM). We investigated changes in the Cu,Zn-SOD activity compared to changes in the Cu,Zn-SOD concentration in erythrocytes obtained from patients with Type 2 (non -insulin-dependent) diabetes mellitus. Cu,Zn-SOD activity in erythrocy tes was significantly lower in Type 2 DM patients than in healthy non- diabetic subjects. The activity correlated negatively with HbA(1c), bu t not with other indicators of metabolic control, such as fasting bloo d glucose or plasma cholesterol or triglyceride. However, there was no statistically significant difference in erythrocyte concentration of Cu,Zn-SOD between diabetic and control samples. Concentration did not correlate with enzymatic activity or HbA(1c). These findings indicate that the inactivation of Cu,Zn-SOD activity in erythrocytes of Type 2 DM patients by hyperglycaemia may be slow, because there is a negative correlation between the enzyme activities and HbA(1c) levels, but not fasting blood glucose levels. This is consistent with glycosylation o f the active site of Cu,Zn-SOD, without any effect of hyperglycaemia o n the concentration of Cu,Zn-SOD. (C) 1998 John Wiley & Sons, Ltd.