Combination of AT2R Agonist and Neprilysin Inhibitor is Superior Than the Combination of AT1R Antagonist and Neprilysin Inhibitor in Protecting Kidney from Injury in High‐Salt Fed Obese Rats

Abstract

Angiotensin II type 1 receptor (AT1R) antagonists, angiotensin II type 2 receptor (AT2R) agonists, and atrial natriuretic peptide (ANP) are natriuretics that provide reno- and cardiovascular protection and reduce blood pressure and volume load. An approved combination therapy (Entresto) of the AT1R blocker valsartan (VAL), and inhibitor of the ANP degrading enzyme neprilysin (NEP) sacubitril (SAC), for patients with heart failure and reduced ejection fraction was found to be associated with increased albuminuria, an indicator of kidney injury. Based on studies showing that AT2R activation affects various renin angiotensin system (RAS) components by decreasing activity of the classical arm components, and increasing expression and activity of those of the protective arm such as angiotensin converting enzyme 2 (ACE2), we hypothesized that AT2R agonist treatment in combination with SAC will provide better reno-protection compared to VAL + SAC. We tested this hypothesis in obese Zucker rats (OZR), in which kidney injury was induced by feeding a high salt diet. Male OZR were fed a 0.4% normal sodium (NSD) or 4% high sodium diet (HSD) and administered vehicle, AT2R agonist C21 (1 mg/kg/day) + SAC (10 mg/kg/day), or VAL (10 mg/kg/day) + SAC (10 mg/kg/day) (16 days, daily gavage). While total food intake was significantly decreased and water intake significantly increased by HSD feeding, neither treatment had an effect compared to the control group. Yet, C21 + SAC treatment, not VAL + SAC, prevented increases in body weight gain and kidney weight, a sign of hypertrophy. Analysis of 24-hr urine samples revealed that HSD caused a marked increase in albuminuria and proteinuria, which was significantly prevented by only C21 + SAC treatment. ANP was similarly preserved and associated with comparable inhibition of NEP activity in both treatment groups compared to HSD control. Furthermore, C21 + SAC treatment caused an increase in the renal expression of ACE2, and a decrease in renal renin activity, unlike VAL + SAC treatment. Moreover, HSD caused a reduction in plasma renin levels, which were increased 3-times by VAL + SAC, but not by C21 + SAC. Renal AT2R expression was unchanged in all treatment groups compared with HSD control group. On the other hand, renal AT1R expression was modestly increased by only VAL + SAC treatment. Taken together, this data suggests the combination of C21 + SAC provides strong reno-protection in obese animals fed HSD and is superior to the protection afforded by the combination of VAL + SAC. Differential regulation of the opposing arms of the RAS may be the basis of the superiority of C21 + SAC over VAL + SAC.