Serum 8-hydroxy-guanine levels are increased in diabetic patients

OBJECTIVE - The production of reactive oxygen species is increased in diabetic patients, especially in those with poor glycemic control. We have investigated oxidative damage in type 2 diabetic patients using serum 8-hydroxyguanine (8-OHG) as a biomarker. RESEARCH DESIGN AND METHODS - We studied 41 type 2 diabetic patients and compared them with 33 nondiabetic control subjects. Serum 8-OHG concentration was assayed using high-pressure liquid chromatography. RESULTS - The type 2 patients had significantly higher concentrations of 8-OHG in their serum than the control subjects (5.03 +/- 0.69 vs. 0.96 +/- 0.15 pmol/ml; P < 0.01). There was no association between the levels of 8-OHG and HbA(1c). We also could not find any correlation between serum 8-OHG levels and age, duration of diabetes, serum lipids, or creatinine or albumine excretion rate. Creatinine clearance showed marginal correlation with serum 8-OHG levels (P = 0.06). Among the diabetic patients, those with proliferative retinopathy had significantly higher 8-OHG levels than those with nonproliferative retinopathy or without retinopathy. Likewise, the serum 8-OHG levels in patients who had advanced nephropathy (azotemia) were higher than in patients with normoalbuminuria, microalbuminuria, or overt proteinuria. CONCLUSIONS - Our findings show that measuring serum 8-OHG is a novel convenient method for evaluating oxidative DNA damage. Diabetic patients, especially those with advanced microvascular complications, had significantly higher serum 8-OHG levels; this suggests that such changes may contribute to the development of microvascular complications of diabetes.