The serum uromodulin level is associated with kidney function.

Background: In chronic kidney diseases of various etiologies, the urinary excretion of uromodulin is usually decreased in parallel with the glomerular filtration rate. This study aimed to investigate whether serum uromodulin is associated with kidney function.

Methods: Within the framework of the Seniorlabor study, a subset of subjectively healthy individuals 60 years of age and older were included in the study. Serum uromodulin was measured with ELISA. The relationship between serum uromodulin and different stages of kidney function (i.e., cystatin C-based 2012-CKD-EPI eGFRCysC>90 mL/min/1.73 m2, 60-89 mL/min/1.73 m2, 45-59 mL/min/1.73 m2, and <45 mL/min/1.73 m2) was investigated. Furthermore, the relationship between serum uromodulin and other markers of kidney function (i.e., creatinine, cystatin C, and urea) was assessed.

Results: In total, 289 participants (140 males/149 females; mean age 71±7 years) were included in the study. There were significant differences in serum uromodulin among the four groups according to different kidney function stages (p<0.001). Serum uromodulin displayed inverse relationships with creatinine (r=-0.39), cystatin C (r=-0.42), and urea (r=-0.30) and, correspondingly, a positive relationship with eGFRCysC (r=0.38, p<0.001 for all). These associations remained intact when fitting a regression model that incorporated age, gender, body mass index, and current smoking status as covariates.

Conclusions: Serum uromodulin behaves in a manner opposite that of the different conventional renal retention markers by displaying lower concentrations with decreasing kidney function. As uromodulin is produced by the cells of the thick ascending limb of the loop of Henle, lower uromodulin serum levels may reflect a reduction in number or function of these cells in chronic kidney disease.