Oxidative stress and other risk factors associated with diabetic nephropathy in type 2 diabetes mellitus

Abstract

Introduction. The aim of the study was to examine whether biomarkers of oxidative stress and antioxidant enzyme activities are among other risk factors for diabetic nephropathy (DN). Methods. The study involved 70 patients with type 2 diabetes (37 males, aged 41 to 81 years) allocated to two groups: one of 32 patients with DN and the other of 38 patients without DN. In the study of oxidative stress 15 healthy persons were included. All examined patients were interviewed and underwent objective examination. Their serum and urine samples were analyzed in order to estimate the quality of glycoregulation and kidney function. Protein thiol groups (P-SH), antioxidant enzyme activities [superoxide dismutase (SOD) and glutathione peroxidase (GPX)] were determined in plasma spectrophotometrically and malondialdehyde-adducts (MDA) by enzyme immunoassay. Results. No significant differences were found between the two groups for demographic characteristics, duration and treatment of diabetes, blood pressure, fasting glucose level and HbA1c. Patients with DN had a higher body mass index, lower estimated glomerular filtration rate (eGFR) and higher albuminuria and proteinuria. Plasma activity of GPX and SOD as well as levels of MDA adducts and P-SH groups were similar in patients with and without DN, but GPX and SOD plasma activities were significantly lower and plasma level of MDA significantly higher in all patients than in healthy controls. Patient gender, age, BMI, HbA1c and plasma level of P-SH and MDA were selected as significant predictors of DN. Patient age, duration of diabetes, serum phosphorus, uric acid levels and plasma SOD activity were negatively associated with eGFR. Patient age, serum levels of protein and albumin and plasma GPX activity were negatively, while systolic BP, serum levels of uric acid and cholesterol were positively associated with proteinuria. Conclusion. Biomarkers of oxidative protein and lipid damage were selected as risk factors for DN, besides several other well known risk factors.

Keywords

• diabetic nephropathy
• antioxidant enzymes
• oxidative damage biomarkers