LOWER URINE UROMODULIN IS ASSOCIATED WITH TREND TO LOWER SODIUM EXCRETION IN MIDDLE-AGED SUBJECTS

Abstract

Objective: Recent GWAS studies found uromodulin gene polymorphisms to be associated with increased risk for hypertension (HT) and chronic kidney disease. It was hypothesized that relation of uromodulin with HT might be through effects on sodium renal excretion. Our aim was to analyse association of urinary uromodulin concentrations (uUMc) with blood pressure (BP) and sodium excretion in a group of untreated middle-aged subjects. Design and method: In this cross-sectional study 175 apparently healthy untreated subjects without a history for CV and with eGFR > 60 ml/min/1.73 m2 were enrolled. Fasting blood and urine 24-hour urine sample were obtained and BP was measured following ESH/ESC guidelines in office (Omron M6) and during regular working (ABPM: Mobile-O-Graph). Based on office BP subjects were divided according to the JNC-7 classification. Uromodulin was determined by Enzyme Linked Immunosorbent Assay (ELISA). Sodium and potassium excretion were analysed in 24-hour urine samples. Fractional sodium excretion (FENa) was calculated. Results: Optimal BP (OBP), prehypertension (PHT) and HT were diagnosed in 47 subjects (43% m, mean age 37), 68 subjects (74% m, mean age 30), and 60 subjects (72% m, mean age 39), respectively. Nonsignificant trend to higher uUMc was found in HT compared to PHT/OBP (52 vs 40/42, respectively). In multivariate linear regression analyses (F = 3.1; p = 0.002) uUMc was positively associated with waist circumference (β = 0.502, p = 0.01), creatinine clearance (β = 0.391, p = 0.03), urinary potassium (β = 0.378, p = 0.001), urinary sodium/potassium ratio (β = 0.413, p = 0.004), and negatively with sodium excretion (β = −0.479, p = 0.003) with a trend to lower FENA. In adjusted multivariate logistic regression analyses, uUMc was not predictor for either for HT or for PHT Conclusions: In our group lower uUMC was associated with lower natriuresis and FENa what is in line with previous observations indicating that decreased salt intake is related to lower uUMc. However, as some other authors found that lower uUMc is related to increased sodium reabsorption in proximal tubule we also observed trend to lower FENa.