Impact on bulk 15N natural isotopic abundance in hair of kidney function in type 2 diabetic nephropathy

Abstract

summary Background and aims: Nephropathy is a serious long-term complication in type 2 diabetic patients. Few data are available about nitrogen metabolism in diabetic nephropathy. Bulk 15 N natural isotopic abundance (NIA) in hair has been shown modified in different pathologies with altered protein metabolism. We have compared bulk 15 N NIA in hair proteins in type 2 diabetic patients to look for differences between groups with or without nephropathy. Methods: Case patients were type 2 diabetic patients with high urinary albumin concentrations (� 20 mg/L or 30 mg/24 h on two of three urine collections) and/or an estimated glomerular filtration rate (eGFR) below 60 mL min � 1 1.73 m � 2 , according to the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) formula. Control subjects were type 2 diabetic patients of the same geographical origin with long-term diabetes, normo-albuminuria and eGFR above 60 mL min � 1 1.73 m � 2 . The bulk 15 NN IA values for hair were measured by isotope ratio measurement mass spectrometry coupled with an elemental analyzer. Results: Thirty-three patients in the nephropathy group and 31 in the control group were included. The mean age of the participants was 69 ± 8 years, and the mean duration of diabetes was 22 ± 8 years. Bulk hair 15 N NIA were 8.9 ± 0.7‰ in the nephropathy group and 9.0 ± 0.5‰ in the control group (p ¼ 0.41). Positive correlations were found between bulk hair 15 N NIA with eGFR (p < 0.01) and with urinary urea concentration (p < 0.01), and a negative correlation with the urinary albumin-to-creatinine ratio (p < 0.001). Conclusions: Bulk hair