The role of oxidative stress in diabetic retinopathy

Purpose To investigate the role of oxidative stress in the development of diabetic retinopathy. Methods This study included 25 patients with diabetic retinopathy (group I), 34 patients with non-insulin-dependent diabetes mellitus without any angiopathy complications (group II) and 26 healthy subjects (group III). The serum malondialdehyde (MDA)-like metabolite levels as an index of lipid peroxidation, the erythrocyte glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and serum vitamin C levels of the patients and healthy subjects were measured. Results The mean serum concentration of MDA-Like metabolites of patients in group I was 4.38 +/- 1.31 nmol/ml, in group II was 3.38 +/- 0.95 nmol/ml and in group III was 2.61 +/- 0.85 nmol/ml. There were significant differences between the groups (p = 0.001 for group I compared with group II, p = 0.0001 for group I compared with group III and p = 0.002 for group II compared with group III). There was a significant correlation between the serum lipid peroxidation concentrations and duration of the disease (r = 0.36, p = 0.047). The mean erythrocyte GSH-Px and SOD levels of group I were respectively 68.97 +/- 18.04 and 1597.78 +/- 296.46 U/g Hb, of group II were 64.30 +/- 19.26 and 1581.33 +/- 278.08 U/g Hb, and of group III were 65.52 +/- 17.58 and 1587.44 +/- 281.17 U/g Hb. There were no significant differences among the antioxidant enzyme levels in the three groups (p > 0.05). The mean serum vitamin C level in group I was 42.72 +/- 8.90 mu mol/l, in group II was 49.26 +/- 11.52 mu mol/l and in group III was 58.57 +/- 9.75 mu mol/l. There were significant differences among the mean serum vitamin C levels of the three groups (p = 0.02 for group I versus group II p = 0.001 for group I versus group III and p = 0.002 for group II versus group III). Conclusions Free radicals forming in diabetes mellitus and increasing over time may play a role in the development of diabetic retinopathy, which is an important complication of the disease.