AimsTo gain insight into the extent of oxidative stress and DNA damage in diabetic kidney disease (DKD), a serious complication of diabetes, we compared the levels of the oxidative stress-related metabolite 8-hydroxy-2'-deoxyguanosine (8-OHdG) in a case-control study accurately matching diabetic patients with and without renal complications. MethodsWe analysed serum 8-OHdG in relation to clinical indicators of kidney function in a group of type-2 diabetes patients including 33 patients with DKD and 33 without DKD. ResultsCirculating levels of 8-OHdG were higher in patients with DKD than in those without (4.6+0.7 ng/mL vs 4.0+0.8 ng/mL, p=0.002). In a logistic regression analysis adjusting for potential confounders, 8-OHdG was associated with DKD (OR: 2.90, 95%CI:1.15-7.34; p=0.02) and in a linear regression model, a 1 ng/mL increase of this biomarker entailed a reduction of 11.5 mL/min/1.73m2 in the renal filtration rate. Furthermore, an interaction analysis showed that glycated hemoglobin was a modifier of the relationship between 8-OHdG and study outcomes (p for effect modification=0.02). ConclusionThis study supports the role of oxidative stress in the pathogenesis of diabetic nephropathy and highlights the potential of serum 8-OHdG as a biomarker for assessing oxidative stress and DNA damage in patients with diabetes and renal complications.