Increased glycated Cu,Zn-superoxide dismutase levels in erythrocytes of patients with insulin-dependent diabetis mellitus.

Our previous study indicated that erythrocyte Cu,Zn-superoxide dismutase (Cu,Zn-SOD) undergoes glycation and inactivation in vivo (1) and in vitro (2). The aim of the present study was to assess glycated Cu,Zn-SOD in patients with insulin-dependent diabetes mellitus. Glycated Cu,Zn-SOD, which binds to a boronic acid affinity column, was measured by the enzyme-linked immunosorbent assay. The percentage of the glycated form in 25 insulin-dependent diabetic children was 40.2 +/- 8.2%; this was significantly higher than that in the normal controls (P less than 0.01). The specific activity of the glycated form in the diabetic children was 163,000 +/- 33,000 IU/mg Cu,Zn-SOD protein, significantly lower than that in controls (P less than 0.01). These data indicate that glycated and less active Cu,Zn-SOD is increased in erythrocytes of patients with insulin-dependent diabetes mellitus.