Serum 8-Hydroxy-Guanine Levels Are Increased in Diabetic Patients

Abstract

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 diabetic 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 HbA1c. We also could not find any correlation between serum 8-OHG levels and age, duration of diabetes, serum lipids, or creatinine or albumin 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.