Excessive dietary salt intake can counteract the renoprotective effects of renin-angiotensin system (RAS) blockade in hypertensive patients with chronic kidney disease (CKD). In rodents, salt loading induces hypertension and renal damage by activating the mineralocorticoid receptor (MR) independently of plasma aldosterone levels. Thus, high salt-induced resistance to RAS blockade may be mediated by MR activation. To test this, a post hoc analysis of the Eplerenone Combination Versus Conventional Agents to Lower Blood Pressure on Urinary Antialbuminuric Treatment Effect (EVALUATE) trial was conducted. Thus, 304 non-diabetic hypertensive patients on RAS-blocking therapy were divided into tertiles according to salt intake (estimated 24-h urinary sodium excretion at baseline) and compared in terms of percent reduction in urinary albumin-to-creatinine ratio (UACR) at 52 weeks relative to baseline. The eplerenone-treated patients in the highest sodium excretion tertile exhibited significantly greater reduction in UACR than the placebo subjects in the same tertile (-22.5% vs. +21.8%, p = 0.02). This disparity was not observed in the lowest (-10.2% vs. -0.84%, p = 0.65) or middle (-19.5% vs. +9.5%, p = 0.22) tertiles. Similar systolic blood pressure changes were observed. In the whole cohort, reduction in UACR correlated positively with reduction in systolic blood pressure (r2 = 0.04, p = 0.02). These results support the hypothesis that excessive salt intake can enhance resistance to RAS blockade by activating MR. They also suggest that eplerenone plus RAS blockade may be effective for CKD in hypertensive patients, especially those with excessive salt intake.
Keywords: Albuminuria; Angiotensin; Blood pressure; Mineralocorticoid receptor; Sodium chloride.