Serum uromodulin and Roux-en-Y gastric bypass – improvement of a marker reflecting nephron mass

Abstract Background Early diagnosis of kidney disease in obese patients and in such with type 2 diabetes mellitus (T2D) can significantly improve treatment outcome. Serum uromodulin (sUMOD) may be a sensitive parameter for early detection of nephropathy. Objectives To analyze sUMOD and traditional markers of kidney function within a cohort study in patients with and without obesity or T2D undergoing metabolic surgery compared to blood donors. Setting University of Heidelberg, Germany. Materials and Methods Patients with obesity (body mass index (BMI) >35 kg/m 2 ) without T2D (n=10) and with T2D (n=10), and patients with non-severe obesity (BMI 25-35 kg/m 2 ) and insulin-dependent T2D (n=16) undergoing Roux-en-Y gastric bypass (RYGB) were enrolled. The control group consisted of 190 blood donors. sUMOD was compared with established renal markers. Results Using sUMOD, impaired kidney function at baseline was present in both groups with T2D, and in none of the patients with obesity without T2D. This impairment was not detectable through traditional markers. Significant improvement of sUMOD was shown in patients with obesity and T2D 12 months postoperatively (from 130.0 ± 77.5 ng/ml to 239.5 ± 179.0 ng/ml (p=0.004)) and in patients with non-severe obesity and T2D 6 months after RYGB (from 140.6 ± 78.0 ng/ml to 298.7 ± 154.0 ng/ml (p=0.017)). In patients with obesity without T2D sUMOD remained stable (p=0.375). Conclusions sUMOD may serve as a tissue specific biomarker in incipient diabetic nephropathy. Improvement of sUMOD after RYGB seems to profoundly restore the structural integrity of nephrons in these patients at risk for diabetic nephropathy.