Amiloride Improves Endothelial Function and Reduces Vascular Stiffness in Female Mice Fed a Western Diet

Abstract

Obese premenopausal women lose their sex related cardiovascular disease protection and develop greater arterial stiffening than age matched men. In female mice, we have shown that consumption of a Western diet (WD), high in fat and refined sugars, is associated with endothelial dysfunction and vascular stiffening, which occur via activation of mineralocorticoid receptors and associated increases in epithelial Na+ channel (ENaC) activity on endothelial cells (EnNaC). Herein our aim was to determine the effect that reducing EnNaC activity with a very-low-dose of amiloride would have on decreasing endothelial and arterial stiffness in young female mice consuming a WD. To this end, we fed female mice either a WD or control diet and treated them with or without a very-low-dose of the ENaC-inhibitor amiloride (1 mg/kg/day) in the drinking water for 20 weeks beginning at 4 weeks of age. Mice consuming a WD were heavier and had greater percent body fat, proteinuria, and aortic stiffness as assessed by pulse-wave velocity than those fed control diet. Treatment with amiloride did not affect body weight, body composition, blood pressure, urinary sodium excretion, or insulin sensitivity, but significantly reduced the development of endothelial and aortic stiffness, aortic fibrosis, aortic oxidative stress, and mesenteric resistance artery EnNaC abundance and proteinuria in WD-fed mice. Amiloride also improved endothelial-dependent vasodilatory responses in the resistance arteries of WD-fed mice. These results indicate that a very-low-dose of amiloride, not affecting blood pressure, is sufficient to improve endothelial function and reduce aortic stiffness in female mice fed a WD, and suggest that EnNaC-inhibition may be sufficient to ameliorate the pathological vascular stiffening effects of WD-induced obesity in females.

Potential Role of Antihypertensive Medications in Preventing Excessive Arterial Stiffening

“…1). Consistent with this notion, our recent research in obese mice indicated that inhibition of ENaC with very low doses of amiloride, an EnNaC inhibitor, decreases oxidative stress, endothelium permeability, inflammation, arterial fibrosis, aortic stiffness, as well as cardiac diastolic dysfunction without affecting blood pressure or Na + retention [11•, 12]. …”

“…Recent research has underscored the role of activated EC Na channels (EnNaC) in promoting a stiff endothelium and associated impaired endothelial NO synthase (eNOS) activation in aortic and mesenteric arteries [11•, 12]. RAAS-mediated activation of EnNaC induces serum and glucocorticoid-regulated kinase 1 (SGK1) activation which impairs ENaC ubiquitination/degradation, leading to its accumulation in the plasma membrane, and a net increase in Na + channel activity [11•].…”

“…Recent research has underscored the role of activated EC Na channels (EnNaC) in promoting a stiff endothelium and associated impaired endothelial NO synthase (eNOS) activation in aortic and mesenteric arteries [11•, 12]. RAAS-mediated activation of EnNaC induces serum and glucocorticoid-regulated kinase 1 (SGK1) activation which impairs ENaC ubiquitination/degradation, leading to its accumulation in the plasma membrane, and a net increase in Na + channel activity [11•]. Increased EnNaC expression and membrane abundance in ECs leads to enhanced Na + influx, polymerization of G-actin to F-actin, reduced EC eNOS activity and NO production, and the development of arterial stiffening [13•, 14•] (Fig.…”

“…Importantly, regulation of RAAS in the vasculature is increased by consumption of western diets, which contribute to arterial fibrosis and increased arterial stiffness [1]. Recent research indicates that aldosterone and diet-induced obesity increase EnNaC expression and activation, leading to reduced NO production that is associated with increases in EC cortical stiffness [11•, 12]. There is also an interaction between specific interactive components of the RAAS.…”

“…cfPWV is recommended as an appropriate method to measure arterial stiffness as established in 2015 by the American Heart association (AHA) Council for High Blood Pressure [2]. New technologies such as atomic force microscopy also provide a powerful investigative tool in detecting cell’s and tissue’s stiffness at the nano-scale as shown in our recent studies [11, 25]. The European Society of Hypertension (ESH)/European Society of Cardiology (ESC) further suggest that a threshold value (12 m/s) in PVW is recommended as an indicator of increased arterial stiffness [47].…”