Insulin, Renal Sodium Transport and Blood Pressure

胰岛素、肾钠转运和血压

• 批准号: 6929844
• 负责人: Carolyn Mary Ecelbarger
• 金额: $ 24.87万
• 依托单位: GEORGETOWN UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-08-01 至 2007-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6929844
• 关键词: SDS polyacrylamide gel electrophoresis; biological transport; blood pressure; confocal scanning microscopy; high performance liquid chromatography; hyperinsulinism; immunocytochemistry; immunoprecipitation; insulin; insulin receptor; laboratory rat; messenger RNA; phosphorylation; polymerase chain reaction; renal tubular transport; sodium channel; telemetry; transport proteins; tyrosine

DESCRIPTION (provided by applicant): Hyperinsulinemia has been linked to hypertension in both animals and humans. Furthermore, insulin has been shown to result in sodium retention by the kidney. In cell culture, insulin directly increases sodium transport capacity of the amiloride-sensitive sodium channel (ENaC), normally located in the renal connecting tubule and collecting duct. Inappropriate retention of sodium in the distal portion of the tubule could result in expanded extracellular fluid volume and hypertension. However, it is not clear what are direct versus indirect effects of hyperinsulinemia with regard to sodium balance. Furthermore, the impact of hyperinsulinemia on the expression and regulation of specific renal sodium transporters and/or channels has not been aqequately studied. Antibodies against many of these proteins have only recently become available. In this proposal, we plan to test the overall hypothesis that insulin and "insulin sensitizing agents", such as PPAR-gamma agonists, will, as a whole, increase the protein abundances of several critical sodium transport proteins expressed in the kidney. We will examine both chronic and acute changes in the abundance and cellular location of these proteins by semi-quantitative immunoblotting and immunohistochemistry. For specific aim 1, we plan to assess the direct effect of increased circulating insulin levels on the relative abundances of the two primary apical sodium transport proteins of the postmacula densa portion of the renal tubule: 1) the amiloride-sensitive epithelial sodium channel (ENaC); and 2) the thiazide-sensitive Na-CI cotransporter (NCC). In specific aim 2, we will evaluate the correlation of changes in ENaC subunit and NCC protein abundances with changes in rat blood pressure, and sensitivity to transporter or channel selective diuretics, i.e., amiloride and polythiazide. In specific aim 3, we will address candidate cellular mechanisms for the increase in ENaC subunit or NCC protein abundances observed with insulin infusion. In specific aim 4 we will evaluate relative changes in cellular distribution of both NCC and ENaC subunits in response to acute and chronic insulin exposure. Finally, in specific aim 5, we will investigate the impact of dietary PPAR-gamma agonists on the regulation of all of the major renal sodium transporter proteins in normal rats and insulin resistant, obese Zucker rats. These studies will, hopefully, provide us with an enlightened understanding of the role of insulin in sodium balance.

描述（由申请人提供）：高胰岛素血症与动物和人类的高血压有关。 此外，胰岛素已被证明会导致肾脏钠潴留。 在细胞培养中，胰岛素直接增加阿米洛利敏感钠通道（ENaC）的钠转运能力，该通道通常位于肾连接小管和集合管中。 钠在肾小管远端的不适当滞留可能导致细胞外液体积增加和高血压。 然而，目前尚不清楚高胰岛素血症对钠平衡的直接影响和间接影响是什么。 此外，高胰岛素血症对特定肾钠转运蛋白和/或通道的表达和调节的影响尚未得到充分研究。 针对这些蛋白质中的许多的抗体最近才出现。 在本提案中，我们计划测试总体假设，即胰岛素和“胰岛素增敏剂”（例如 PPAR-γ 激动剂）总体上会增加肾脏中表达的几种关键钠转运蛋白的蛋白质丰度。 我们将通过半定量免疫印迹和免疫组织化学检查这些蛋白质的丰度和细胞位置的慢性和急性变化。 对于具体目标 1，我们计划评估循环胰岛素水平增加对肾小管致密斑后部分两种主要顶端钠转运蛋白相对丰度的直接影响：1) 阿米洛利敏感上皮钠通道 (ENaC) ）； 2)噻嗪类敏感的Na-Cl协同转运蛋白(NCC)。 在具体目标 2 中，我们将评估 ENaC 亚基和 NCC 蛋白丰度变化与大鼠血压变化的相关性，以及对转运蛋白或通道选择性利尿剂（即阿米洛利和多噻嗪）的敏感性。 在具体目标 3 中，我们将探讨通过胰岛素输注观察到的 ENaC 亚基或 NCC 蛋白丰度增加的候选细胞机制。 在具体目标 4 中，我们将评估 NCC 和 ENaC 亚基的细胞分布对急性和慢性胰岛素暴露的相对变化。 最后，在具体目标 5 中，我们将研究膳食 PPAR-γ 激动剂对正常大鼠和胰岛素抵抗、肥胖 Zucker 大鼠中所有主要肾钠转运蛋白的调节的影响。 希望这些研究能让我们对胰岛素在钠平衡中的作用有更深入的了解。