Urinary 8-hydroxydeoxyguanosine levels in diabetic retinopathy patients

PURPOSE. Involvement of oxidative stress in the pathogenesis of diabetic microvascular complications has been proposed. Recently, 8-hydroxy-2'-deoxyguanosine (8-OHdG) has been reported to serve as a new sensitive biomarker of the oxidative DNA damage in vivo. This study was undertaken to investigate whether the urinary levels of 8-OHdG are altered in patients with type 2 diabetes. The authors also attempted to analyze the relationship between 8-OHdG levels and other clinical parameters of patients with diabetes, especially the relationship between oxidative DNA damage and the severity of the retinal lesions in patients with diabetic retinopathy. METHODS. The authors studied 60 patients with type 2 diabetes and compared them with 35 nondiabetic control subjects. Urinary 8-OHdG concentrations were assayed using competitive enzyme-linked immunosorbent assay. RESULTS. The patients with type 2 diabetes had significantly higher concentrations of 8-OHdG in their urine than the control subjects ( 19.6 +/- 6.7 vs 11.9 +/- 4.9 ng/mgCr; p< 0.05). The authors could not find any correlation between urinary 8-OHdG levels and age, duration of diabetes, or serum lipids. However, HbA1c values were significantly correlated with 8-OHdG values. Among the patients with diabetes, those with proliferative retinopathy had significantly higher 8-OHdG levels than those with nonproliferative retinopathy or without retinopathy. CONCLUSIONS. The authors' findings show that measuring urinary 8-OHdG is a novel convenient method for evaluating oxidative DNA damage in patients with diabetes, and it is also suggested that 8-OHdG could be a sensitive biomarker and may be helpful for the early diagnosis and treatment of patients with diabetic retinopathy.