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The Effect of Dietary Sodium Intake on Ambulatory Blood Pressure Levels According to Urinary Uromodulin Levels in Patients With Chronic Kidney Disease
In Brief
An observational study for Chronic Kidney Disease and Hypertension. Completed, enrolled 130 participants across 1 site.
Detailed Summary
In chronic kidney disease (CKD), hypertension is characterized by the phenomenon of sodium-sensitivity, i.e., the disproportionate increase in blood pressure (BP) due to an increase in dietary sodium consumption to maintain homeostasis through urinary sodium excretion. Impaired renal circulation, blunt suppression of renin-angiotensin-aldosterone system, sympathetic nervous system overactivity, paradoxically reduced levels of atrial natriuretic peptide and hyperinsulinemia represent the main pathophysiologic mechanisms. Accumulated evidence has suggested that uromodulin plays a central role in the development of sodium-sensitive hypertension. Uromodulin is a kidney-specific glycoprotein which is exclusively produced by the epithelial cells lining the thick ascending limb and early distal convoluted tubule. It is currently recognized as a multifaceted player in kidney physiology and disease, with discrete roles for intracellular, urinary, interstitial and serum uromodulin. Among these, urinary uromodulin modulates renal sodium handling through regulating tubular transporters that reabsorb sodium and are targeted by diuretics, i.e., the loop diuretic-sensitive Na+-K+-2Cl- cotransporter type 2 (NKCC2) and the thiazide-sensitive Na+/Cl- cotransporter (NCC). Given these roles, the contribution of uromodulin to sodium-sensitive hypertension has been proposed. In preclinical models, uromodulin deficiency causes decreased BP that is resistant to dietary salt, while uromodulin overexpression causes hypertension due to increased tubular sodium reabsorption that is responsive to furosemide. Genetic human studies have identified robust associations of specific UMOD gene variants with sodium sensitivity and incident hypertension risk, while comprehensive Mendelian randomization studies have affirmed these associations by highlighting the causal relationship between UMOD variants, urinary uromodulin levels and hypertension. Furthermore, clinical studies in both healthy individuals and hypertensive patients have indicated a link between sodium sensitivity and uromodulin, directly affecting mean BP levels and BP response to salt intake. With regards to CKD population, solid data on the link of uromodulin with sodium sensitivity are currently missing from the literature. There is only a pediatric study in the setting of CKD (stages 2-3), which failed to show an association between urinary uromodulin levels indexed to urinary creatinine (UMOD/uCr) and either 24-hour or office BP; however, this study has several limitations, and its results should be interpreted with caution. To best of our knowledge, there is no study up to date investigating the effect of dietary sodium intake on 24-hour ambulatory blood pressure depending on urinary uromodulin levels in adult CKD patients.