Endothelial Cell-specific Knockout of Epithelial Sodium Channel Prevents Aortic Stiffness, Cardiac Stiffness and Diastolic Dysfunction in Response to a Western Diet in Female Mice.

A western diet (WD), high in fructose and fat, is often accompanied by insulin resistance and cardiovascular disease characterized by endothelial cell (EC) dysfunction, increased arterial and cardiac stiffness, and diastolic dysfunction. Although premenopausal non-obese women are protected against cardiovascular disease, arterial stiffness and diastolic dysfunction, in obese women these abnormalities are more pronounced than in men. We have recently developed a clinically relevant, WD fed, murine model that exhibits increased aortic stiffness associated with vascular and cardiac dysfunction. In this model, female mice have high plasma aldosterone levels and increased mineralocorticoid receptor expression (MR) in both the vasculature and heart. One of the mechanisms by which MR activation promotes endothelial stiffness is through increased expression and activation of epithelial sodium channel (ENaC) in ECs (EnNaC). We reported increased aortic EC stiffness associated with increased expression of EnNaC in WD fed mice and suppression of aortic stiffness and improved diastolic function by treatment with a low dose of an MR antagonist or the ENaC inhibitor, amiloride. In this study, we tested the hypothesis that specific deletion of EnNaC, decreases aortic EC stiffness and improves vascular relaxation and diastolic function in WD fed female mice. To produce cell specific deletion of the EnNaC gene,”floxed” EnNaC mice were serially crossed with Tie 2-Cre transgene mice. This resulted in marked suppression of EnNaC expression in ECs. Female KO mice and littermate controls were fed a WD with high in fat (46%) and fructose (17.5%) for 12 weeks. Compared to mice fed a control diet (CD), aortic EC stiffness, measured ex vivo by atomic force microscopy (AFM) was significantly increased in WD fed mice and this was prevented in EnNaC KO mice fed WD. Decreased EC stiffness was associated with improved endothelial-dependent aortic relaxation in response to acetylcholine. Moreover, deletion of EnNaC also prevented WD induced impairment of diastolic function. Taken together, these findings support the notion that a WD promotes ECMR mediated activation of EnNaC and associated aortic stiffness, cardiac stiffness and diastolic dysfunction.