Regulation of Aldosterone Production in the Adrenal

描述（由申请人提供）： 醛固酮是主要的盐皮质激素参与维持液体和电解质（钠）的平衡在人体内。然而，醛固酮产生和肾上腺分泌的异常导致和/或加重几种人类疾病，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，伴随着与超重相关的疾病，包括高血压。超重导致高血压的机制尚不清楚;然而，一些研究表明与醛固酮水平增加有关。我们最近的新研究结果表明，生理浓度的极低密度脂蛋白（VLDL）刺激醛固酮的生产在多种肾小球细胞模型在体外。这一结果提示了一种可能的机制，与VLDL水平升高（血脂异常）相关的肥胖可导致高血压，至少部分原因是不适当的醛固酮分泌。为了增加我们对VLDL诱导的醛固酮产生机制的理解，本研究提出了三个具体目标：（1）检验生理和病理生理VLDL浓度将增强对醛固酮产生的其它生理刺激物的反应的假设，并确定参与VLDL刺激作用的信号传导机制，（2）检验VLDL的脂质成分促进醛固酮分泌的假设，并确定这种活性成分，和（3）检验编码磷脂酶D2（PLD 2）的基因的切除也调节体内醛固酮水平的假设，磷脂酶D2是体外介导醛固酮产生的重要信号，基础和VLDL水平升高与饮食诱导的肥胖有关。这些假设将通过监测用不同浓度的VLDL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利用的信号转导机制将使用过表达和RNA干扰介导的敲低策略来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。预处理以使蛋白质变性/降解和提取包含VLDL的脂质，以及脂质组学以鉴定VLDL脂质组分，将用于确定VLDL中负责刺激醛固酮产生的试剂。该VLDL组分的作用将在确定VLDL的醛固酮刺激作用的研究中进行验证，所述VLDL使用富集和消耗策略进行预处理以改变所鉴定的活性剂的水平。体内PLD 2敲除小鼠模型将用于确定PLD 2缺失对肾上腺中醛固酮水平和醛固酮合酶（CYP 11 B2）表达的影响，所述影响是基础的和慢性血管紧张素II输注后或饮食诱导的肥胖。拟议的研究检查的能力，极低密度脂蛋白调节醛固酮的生产将扩大我们的知识的作用，肥胖增加极低密度脂蛋白水平的发展中的高血压的肥胖和/或瘦的个人，以及可能参与异常的极低密度脂蛋白激活的信号在高血压在这些人。

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.