Intrarenal Mechanisms of Ghrelin in Obesity-Hypertension

生长素释放肽在肥胖-高血压中的肾内机制

• 批准号: 9337433
• 负责人: SHETAL H PADIA
• 金额: $ 35.55万
• 依托单位: UNIVERSITY OF VIRGINIA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-25 至 2021-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9337433
• 关键词: Blood Pressure; Blood Vessels; Chronic; Conscious; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Data; Development; Duct (organ) structure; Ductal Epithelial Cell; Embryo; Epidemic; Equilibrium; Essential Hypertension; Excretory function; Foundations; Gene Expression; Gene Expression Regulation; Glomerular Filtration Rate; Goals; High Fat Diet; Hormones; Human; Hypertension; In Vitro; Infusion procedures; Kidney; Knowledge; Liquid substance; Measures; Mediating; Mediator of activation protein; Metabolic; Microdialysis; Mission; Modeling; Molecular; Natriuresis; Obesity; Pathogenesis; Pathway interactions; Perfusion; Pharmacology; Physiological; Pituitary Gland; Production; Public Health; RNA; Rattus; Regulation; Renal Blood Flow; Reporting; Research; Risk; Role; Signal Pathway; Sodium; Stomach; System; Techniques; Telemetry; Testing; Time; Tissues; Tubular formation; United States National Institutes of Health; Weight; Weight Gain; autocrine; epithelial Na+ channel; ghrelin; ghrelin receptor; in vivo; increased appetite; interstitial; knock-down; knockout gene; mortality; new therapeutic target; novel; pressure; prevent; receptor; receptor expression; receptor function; response; success

PROJECT SUMMARY Excess weight gain contributes up to 65% of the risk of primary hypertension, and the increase in blood pressure (BP) in response to high-fat diet (HFD) is preceded by significant reductions in renal sodium (Na+) excretory capacity. Normal Na+ excretion is then only achieved at the expense of elevated renal perfusion pressure. Over time, the kidneys reset to require an elevated BP in order to continue to excrete a normal Na+ load. The knowledge of novel pathways regulating renal Na+ flux is therefore crucial to our success in optimizing therapy for major public health conditions such as obesity- hypertension. Recently, we reported that (1) direct renal infusion of ghrelin, the most potent, appetite-stimulating hormone in the body, activates GRs in the collecting duct (CD) to increase cAMP and ENaC-dependent Na+ reabsorption in rats; (2) renal infusion of a GR antagonist alone (to elucidate the actions of endogenous ghrelin), induces a robust natriuresis, indicating that physiological levels of circulating ghrelin regulate Na+ reabsorption under normal conditions; and (3) in HFD, renal GR expression is increased, and pharmacological blockade of intrarenal GRs prevents HFD- induced hypertension in rats. While these data establish some basic information regarding intrarenal GR expression and function, nothing is known about intrarenal production of ghrelin and its signaling pathways (Aim 1) or the contribution of GR-mediated antinatriuresis to the pathogenesis of HFD-induced hypertension (Aim 2). In this application, we propose studies in vitro using CD cells & in vivo using a HFD model of obesity- hypertension to study the mechanisms of the renal ghrelin-GR system. To isolate the role of the renal GR in chronic responses, we have developed a small inhibitory RNA (siRNA), that when infused chronically into the kidney, specifically transfects & knocks down CD GRs, while preserving GR expression in the other tissues. The major advantage of this over gene knockout is that it permits reduction in the gene expression without dangers of embryonic lethality and with less risk of compensatory gene regulation. We will also measure molecules released into the renal interstitium in response to renal manipulations of GR expression in conscious rats utilizing a novel microdialysis technique which permits analysis of mediators closer to target receptors and less prone to circulatory degradation. Thus, the ability to move fluidly between in vitro molecular and in vivo functional responses specific to the GR is a major significant aspect of the approach.

项目概要 体重增加过多导致原发性高血压风险高达 65%，并且血液中的血液浓度增加 高脂饮食 (HFD) 导致血压 (BP) 升高之前，肾钠 (Na+) 会显着降低 排泄能力。只有以肾灌注升高为代价才能实现正常的 Na+ 排泄 压力。随着时间的推移，肾脏会重置，需要升高血压才能继续排出正常的 Na+ 加载。因此，了解调节肾脏 Na+ 通量的新途径对于我们在这方面的成功至关重要。 优化针对肥胖-高血压等主要公共卫生状况的治疗。最近，我们报道了 (1) 直接肾输注胃饥饿素（体内最有效的食欲刺激激素），可激活体内的 GR 集合管 (CD) 增加大鼠 cAMP 和 ENaC 依赖性 Na+ 重吸收； (2)肾输注 单独使用 GR 拮抗剂（以阐明内源性生长素释放肽的作用）可诱导强烈的尿钠排泄，表明 正常情况下，循环胃饥饿素的生理水平调节 Na+ 的重吸收；和 (3) 在 HFD，肾脏 GR 表达增加，肾内 GR 的药物阻断可预防 HFD- 诱发大鼠高血压。虽然这些数据建立了有关肾内 GR 的一些基本信息 表达和功能，对于 ghrelin 的肾内产生及其信号通路一无所知 （目标 1）或 GR 介导的抗尿钠排泄对 HFD 诱发高血压发病机制的贡献 （目标 2）。在此应用中，我们建议使用 CD 细胞进行体外研究，并使用 HFD 肥胖模型进行体内研究 - 高血压研究肾ghrelin-GR系统的机制。分离肾 GR 在 为了缓解慢性反应，我们开发了一种小抑制性 RNA (siRNA)，当长期将其注入 肾脏，专门转染并敲低 CD GR，同时保留其他组织中的 GR 表达。 与基因敲除相比，这种方法的主要优点是它可以减少基因表达而不需要 胚胎致死的危险和补偿性基因调控的风险较小。我们也会测量 清醒状态下肾对 GR 表达的操作响应释放到肾间质的分子 大鼠利用一种新型微透析技术，可以分析更接近目标受体的介质， 不易发生循环退化。因此，在体外分子和体内分子之间流畅移动的能力 遗传资源特有的功能反应是该方法的一个重要方面。