Clinical, Genetic, and Urinary Factors Associated with Uromodulin Excretion.

BACKGROUND AND OBJECTIVES The urinary excretion of uromodulin is influenced by common variants in the UMOD gene, and it may be related to NaCl retention and hypertension. Levels of uromodulin are also dependent of the renal function, but other determinants remain unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We tested associations between the urinary excretion of uromodulin; medical history and medication; serum and urinary levels of electrolytes, glucose, and uric acid; and the genotype at the UMOD/Protein Disulfide Isomerase-Like, Testis Expressed locus (rs4293393 and rs12446492); 943 participants from the CARTaGENE Cohort, a random sample from the Canadian population of 20,004 individuals, were analyzed. Participants with available genotyping were obtained from a substudy addressing associations between common variants and cardiovascular disease in paired participants with high and low Framingham risk scores and vascular rigidity indexes. RESULTS The population studied was 54±9 years old, with 51% women and eGFR of 9±14 ml/min per 1.73 m(2). Uromodulin excretion was 25 (11-42) mg/g creatinine. Using linear regression, it was independently higher among patients with higher eGFR, the TT genotype of rs4293393, and the TT genotype of rs12446492. The fractional excretions of urate and sodium showed a strong positive correlation with uromodulin, likely linked to the extracellular volume status. The presence of glycosuria and the use of uricosuric drugs, which both increased the fraction excretion of urate, were independently associated with a lower uromodulin excretion, suggesting novel interactions between uric acid and uromodulin excretion. CONCLUSIONS In this large cohort, the excretion of uromodulin correlates with clinical, genetic, and urinary factors. The strongest associations were between uric acid, sodium, and uromodulin excretions and are likely linked to the extracellular volume status.