Leptin‐Induced Endothelial Dysfunction is Mediated by Endothelial Mineralocorticoid Receptor Epithelial Sodium Channel Activation in Female Mice

Rising rates of hypertension are significantly associated with rising rates of obesity. While the mechanisms of obesity‐associated hypertension have been heavily investigated, these studies have overwhelmingly favored men and male rodents as research subjects. Therefore, the sex‐specific mechanisms of obesity‐associated hypertension require investigation. Our lab has previously shown that the adipocyte‐derived hormone leptin, whose levels are drastically increased in obesity, is required for hypertension and endothelial dysfunction in obese female mouse models, the development of which is dependent on leptin‐induced aldosterone secretion and subsequent mineralocorticoid receptor (MR) activation. The epithelial sodium channel alpha (ENaC), whose transcription is directly upregulated by MR activation, has also been implicated in endothelial dysfunction in female mice. We therefore sought to test the hypothesis that endothelial MR activation mediates leptin‐induced endothelial dysfunction via increased activation of ENaC. To test that endothelial MR activation, specifically, is required for leptin‐induced endothelial dysfunction we infused female endothelial cell‐specific MR knockout mice (ECMR KO) with leptin (0.9 mg/kg/day) via subcutaneous osmotic minipump. Wild‐type mice (WT) developed endothelial dysfunction, as assessed by vascular (aortic rings) relaxation to acetylcholine (10 −9 M–10 −5 M, nonlinear fit curve), in response to leptin infusion (P<0.05, two‐way ANOVA, n=4–6). However, ECMR KO female mice infused with leptin were protected from endothelial dysfunction (n=6–7), indicating that endothelial MR activation mediates leptin‐induced endothelial dysfunction in female mice. In contrast, no effect of leptin nor endothelial MR deletion was observed on endothelial function in male WT and ECMR KO mice (n=2–5). To assess if MR‐mediated ENaC activation plays a role in leptin‐induced endothelial dysfunction, leptin‐infused female mice were treated with amiloride (ENaC antagonist, 100 ug/day in drinking water) which ablated endothelial dysfunction in female leptin‐infused mice (P<0.05, two‐way ANOVA, n=4), indicating that leptin‐induced endothelial dysfunction requires ENaC activation. In addition, we sought to assess the potential for leptin to upregulate endothelial cell ENaC expression in female mice. Isolated endothelial cells, which were obtained from the aorta via CD31‐specific magnetic bead sorting, were extracted from female Agouti hyperleptinemic obese mice and RT‐PCR analysis for mRNA expression of ENaC demonstrated elevated ENaC expression in hyperleptinemic mice (10.8±0.5‐fold change from lean control female mice, n=2–3). These elevations in endothelial ENaC mRNA expression are associated with elevated plasma aldosterone in hyperleptinemic female mice, indicating that leptin‐induced aldosterone induces endothelial dysfunction via increased MR activation, which ultimately leads to elevated ENaC expression and activation. Therefore, MR‐stimulated ENaC upregulation may play a crucial role in the development of leptin‐mediated cardiovascular diseases in obese females. Support or Funding Information This work was supported by the following: NIH 1R01HL130301‐01, AHA 16IRG27770047, NIH 5F32HL136191‐0 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .