The role of oxidative stress in diabetic retinopathy

Purpose To investigate the role of oxidative stress in the development of d iabetic retinopathy. Methods This study included 25 patients with diabetic retinopathy (group I) , 34 patients with non-insulin-dependent diabetes mellitus without any angi opathy complications (group II) and 26 healthy subjects (group III). The se rum malondialdehyde (MDA)-like metabolite levels as an index of lipid perox idation, the erythrocyte glutathione peroxidase (GSH-Px), superoxide dismut ase (SOD) and serum vitamin C levels of the patients and healthy subjects w ere 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 a nd in group III was 2.61 +/- 0.85 nmol/ml. There were significant differenc es 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 compare d with group III). There was a significant correlation between the serum li pid 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 respecti vely 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 am ong 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 w as 49.26 +/- 11.52 mu mol/l and in group III was 58.57 +/- 9.75 mu mol/l. T here 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). Conclusion s Free radicals forming in diabetes mellitus and increasing over time may p lay a role in the development of diabetic retinopathy, which is an importan t complication of the disease.