Regulation of Aldosterone Production in the Adrenal

描述(由申请人提供)： 醛固酮是维持人体内液体和电解质(钠)平衡的主要矿物质皮质激素。然而，肾上腺产生和分泌醛固酮的异常会导致和/或加剧一些人类疾病，包括高血压和充血性心力衰竭。这些疾病在退伍军人中很普遍，近350万退伍军人被诊断患有高血压，其中约10%患有充血性心力衰竭。同样，许多退伍军人超重或肥胖，伴随而来的与超重相关的疾病，包括高血压。超重导致高血压的机制尚不清楚；然而，一些研究表明，这与醛固酮水平升高有关。我们最近的新结果表明，生理浓度的极低密度脂蛋白(VLDL)在体外刺激多个肾小球带细胞模型中的醛固酮产生。这一结果表明，与极低密度脂蛋白水平升高(血脂异常)相关的肥胖可能导致高血压，至少部分原因是不适当的醛固酮分泌。为了加深我们对极低密度脂蛋白诱导的醛固酮产生机制的了解，本研究提出了三个具体的目标：(1)检验生理和病理生理学的极低密度脂蛋白浓度将增强对其他醛固酮产生的生理刺激物的反应的假说，并确定参与极低密度脂蛋白刺激作用的信号机制；(2)检验极低密度脂蛋白的脂类成分诱导醛固酮分泌的假说并确定其活性成分；(3)检验假说：切割编码磷脂酶D2(PLD2)的基因也调节体内、基础和与饮食诱导的肥胖相关的极低密度脂蛋白水平升高的醛固酮水平。这些假说将通过监测不同浓度的极低密度脂蛋白和其他醛固酮激动剂处理的肾小球细胞模型中的醛固酮产生来检验。此外，VLDL所利用的信号转导机制将通过过度表达和RNA干扰介导的击倒策略来确定，以影响信号分子的水平，然后确定这些操作对VLDL诱导的醛固酮产生的影响。将使用变性/降解蛋白质和提取组成极低密度脂蛋白的脂质的预处理，以及鉴定极低密度脂蛋白脂质成分的脂质组学，以确定极低密度脂蛋白中负责刺激醛固酮产生的因素。这一极低密度脂蛋白成分的作用将在确定极低密度脂蛋白的醛固酮刺激作用的研究中得到验证，该研究使用浓缩和耗竭策略来改变已确定的活性物质的水平。在体内，PLD2基因敲除小鼠模型将被用来确定PLD2基因缺失对基础和慢性血管紧张素II注射或饮食诱导肥胖时肾上腺醛固酮水平和醛固酮合成酶(CYP11B2)表达的影响。拟议中的研究将探讨极低密度脂蛋白调节醛固酮生成的能力，这将扩大我们对肥胖引起的极低密度脂蛋白水平升高在肥胖和/或瘦人高血压发病中的作用的认识，以及极低密度脂蛋白激活信号异常在这些人高血压中的可能参与。

DESCRIPTION (provided by applicant): Aldosterone is the main mineralocorticoid hormone involved in maintaining fluid and electrolyte (sodium) balance in the human body. However, abnormalities in aldosterone production and secretion from the adrenal gland result in and/or exacerbate several human diseases including high blood pressure and congestive heart failure. These disorders are prevalent in the veteran population, with nearly 3.5 million veterans diagnosed with hypertension and approximately 10% of these with congestive heart failure. Similarly, many veterans are overweight or obese, with the attendant disorders associated with excess weight, including hypertension. The mechanism by which excess weight causes hypertension is unclear; however, some studies have suggested a link with increased aldosterone levels. Our recent novel results demonstrate that physiological concentrations of very-low-density lipoprotein (VLDL) stimulate aldosterone production in multiple zona glomerulosa cell models in vitro. This result suggests a possible mechanism by which obesity, which is associated with elevated VLDL levels (dyslipidemia), can result in hypertension resulting, at least in part, from inappropriate aldosterone secretion. To increase our understanding of the mechanisms underlying VLDL-induced aldosterone production, three specific aims are proposed in this study: (1) test the hypothesis that physiological and pathophysiological VLDL concentrations will enhance the response to other physiological stimulators of aldosterone production and determine the signaling mechanisms involved in the stimulatory action of VLDL, (2) test the hypothesis that a lipid component of VLDL elicits aldosterone secretion and define this active component, and (3) test the hypothesis that ablation of the gene encoding phospholipase D2 (PLD2), an important signal mediating aldosterone production in vitro, also regulates aldosterone levels in vivo, basally and with elevated VLDL levels related to diet-induced obesity. These hypotheses will be tested by monitoring aldosterone production in glomerulosa cell models treated with various concentrations of VLDL and other aldosterone agonists. In addition, the signal transduction mechanisms utilized by VLDL will be defined using overexpression and RNA interference-mediated knock down strategies to influence the levels of signaling molecules followed by a determination of the effect of these manipulations on VLDL-induced aldosterone production. Pretreatment to denature/degrade the protein and extraction of the lipids comprising VLDL, as well as lipidomics to identify VLDL lipid components, will be used to determine the agent in VLDL responsible for stimulating aldosterone production. The role of this VLDL component will be verified in studies determining the aldosterone stimulatory effect of VLDL pretreated using enrichment and depletion strategies to alter levels of the identified active agent. In vivo a PLD2 knockout mouse model will be used to determine the effects of the loss of PLD2 on aldosterone levels and aldosterone synthase (CYP11B2) expression in the adrenal basally and upon chronic angiotensin II infusion or with diet-induced obesity. The proposed studies examining the ability of VLDL to modulate aldosterone production will expand our knowledge of the role of obesity-increased VLDL levels in the development of hypertension in obese and/or lean individuals, as well as the possible involvement of abnormalities in the VLDL-activated signals in hypertension in these individuals.