Altered antioxidant enzyme defences in insulin‐dependent diabetic men with increased resting and exercise‐induced oxidative stress

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Abstract
Impaired antioxidant defences may predispose to the increased resting and exercise‐induced oxidative stress found in patients with insulin‐dependent diabetes mellitus (IDDM). We investigated major erythrocyte antioxidant enzyme activities at rest and in response to sustained, moderate intensity physical exercise in young diabetic men (n = 9) previously reported to have markedly elevated plasma lipid peroxidation and blood glutathione levels compared with control men (n = 13) (Laaksonen et al. 1996). At rest, erythrocyte glutathione reductase activity was 15% higher in the diabetic group (P = 0.049). Se‐glutathione peroxidase and glutathione‐S‐transferase activities were similar in both groups. Red cell Cu, Zn‐superoxide dismutase and catalase activities were lower in the IDDM group (P = 0.033 and P = 0.023, respectively). After 40 min of exercise at 60% of the subjects' peak oxygen consumption, Se‐glutathione peroxidase activity rose by about 14% in the control group (P = 0.003), but not in the IDDM group (P = 0.47). Exercise did not cause significant changes in other enzyme activities in either group. To conclude, lower erythrocyte Cu, Zn‐superoxide dismutase and catalase activity in young men with IDDM at rest may contribute to increased oxidative stress. On the other hand, increased glutathione reductase activity may represent a compensatory upregulation of glutathione homeostasis in response to increased oxidative stress. Upregulation of Se‐glutathione peroxidase activity in response to physical activity appeared to be impaired in men with IDDM.

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