ALTERED ANTIOXIDANT ENZYME DEFENSES IN INSULIN-DEPENDENT DIABETIC MENWITH INCREASED RESTING AND EXERCISE-INDUCED OXIDATIVE STRESS

Impaired antioxidant defences may predispose to the increased resting and exercise-induced oxidative stress found in patients with insulin-d ependent diabetes mellitus (IDDM). We investigated major erythrocyte a ntioxidant enzyme activities at rest acid in response to sustained, mo derate intensity physical exercise in young diabetic men (n = 9) previ ously reported to have markedly elevated plasma lipid peroxidation and blood glutathione levels compared with control men (n = 13) (Laaksone n et al. 1996). Al rest, erythrocyte glutathione reductase activity wa s 15% higher in the diabetic group (P = 0.049). Se-glutathione peroxid ase and glutathione-S-transferase activities were similar in both grou ps. 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 al 60% of the subjects' peak oxygen consumption, S e-glutathione peroxidase activity rose by about 14% in the control gro up (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 catala se 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 home ostasis in response to increased oxidative stress. Upregulation of Se- glutathione peroxidase activity in response to physical activity appea red to be impaired in men with IDDM.