Mechanisms and Consequences of Defective Flow-Induced Potassium Secretion in the Metabolic Syndrome

项目摘要/摘要：代谢综合征影响5000万美国人，并与 患有肥胖症和胰岛素抵抗。高钾血症与危及生命的心律失常和 死亡率增加，患有胰岛素抵抗和2型糖尿病的患者更容易患上高钾血症。 然而，肾脏钾(K)处理的潜在紊乱仍未被探索。作为我们正在进行的 NIH赞助的胰岛素抵抗中离子通道功能的研究，我们，研究人员(PI和Co-I)， 发现在远端肾单位，血流诱导的钾分泌(FIKS)由BK通道和肾钾介导 手柄有缺陷。BK通道的缺失会导致肾脏K处理的缺陷，并损害K的适应。 这项建议的目的是确定BK通道减少的潜在机制- 介导的远端肾单位FIKs及其对钾适应和高钾血症的影响 胰岛素抵抗综合症。R01拨款将提供必要的资源来检验这一假设 远端肾单位胰岛素抵抗是BK通道缺陷伴胰岛素降低的一种表现 信号导致BK通道活动中断，从而导致FIKs和K适应缺陷，以及 易患高钾血症。为了检验这一假设，我们提出了两个具体目标。目标1是确定 胰岛素抵抗小鼠远端肾单位BK通道功能障碍的细胞机制。 使用对照组和胰岛素抵抗小鼠，我们将测量远端的表达和亚细胞定位 使用两种创新的方法，并将研究钙离子和电压 BK通道的灵敏度。我们还将衡量有缺陷的BK频道对K适应的影响和 代谢综合征中的高钾血症。目标2是确定胰岛素受体信号受损是否在 远端肾单位足以表现为胰岛素抵抗时的BK通道功能障碍。用一本小说 肾小管胰岛素受体基因敲除小鼠，我们将检测BK和钙通道的表达，并 使用与目标1类似的方法进行亚细胞定位。我们将研究BK的钙和电压敏感性 在对照组和基因敲除小鼠中的通道，并将测量胰岛素受体信号缺失对K 适应和高血钾。我们还将测量与胰岛素和BK通道相关的细胞信号通路。 我们预计，这些结果将通过确定适当的饮食和 防治胰岛素相关疾病高钾血症的药物靶点 抵抗力，如肥胖和2型糖尿病。拟议的研究是创新的，因为我们将 直接研究肾脏BK通道在胰岛素抵抗中的调节，并将使用新的试剂和 尖端技术，以了解缺陷Fix对高钾血症的后果。通过 建议的研究，我们还将了解胰岛素在肾脏中的胰岛素信号机制 抵抗综合征和饮食在决定这种综合征的心血管结局中的作用。

PROJECT SUMMARY / ABSTRACT: The metabolic syndrome affects 50 million Americans, and is associated with obesity and insulin resistance. Hyperkalemia is associated with life-threatening cardiac arrhythmias and increased mortality, and patients with insulin resistance and Type 2 diabetes are susceptible to hyperkalemia. However, potential derangements in renal potassium (K) handling remain unexplored. As part of our ongoing NIH-sponsored studies of ion channel function in insulin resistance, we, the Investigators (PI and Co-I), uncovered that flow-induced K secretion (FIKS) in the distal nephron, mediated by BK channels, and renal K handling is defective. Deletion of BK channels leads to defective renal K handling, and impaired K adaptation. The objective of this proposal is to determine the mechanisms underlying the reduction in BK channel- mediated FIKS in the distal nephron and to determine the consequences for K adaptation and hyperkalemia in the insulin resistance syndrome. The R01 Grant will provide the necessary resources to test the hypothesis that insulin resistance in the distal nephron is a phenocopy for BK channel deficiency with decreased insulin signaling leading to disrupted BK channel activity, and thus, defective FIKS and K adaptation, and predisposition to hyperkalemia. To test this hypothesis, we propose two specific aims. Aim #1 is to determine the cellular mechanisms of distal nephron BK channel dysfunction in a mouse model of insulin resistance. Using control and insulin resistant mice, we will measure expression and subcellular localization of distal nephron BK and Ca2+- channels using two innovative methodologies, and will study the Ca2+ and voltage sensitivity of BK channels. We will also measure the impact of defective BK channels on K adaptation and hyperkalemia in the metabolic syndrome. Aim #2 is to determine whether impaired insulin receptor signaling in the distal nephron is sufficient to phenocopy the BK channel dysfunction of insulin resistance. Using a novel renal tubular insulin receptor knockout mouse, we will measure BK and Ca2+ channel expression, and subcellular localization using similar methods to Aim #1. We will study the Ca2+ and voltage sensitivity of BK channels in control and knockout mice and will measure the effect of deletion of insulin receptor signaling on K adaptation and hyperkalemia. We will also measure cell signaling pathways related to insulin and BK channels. We anticipate that these results will significantly advance the field by identifying appropriate dietary and pharmaceutical targets for the prevention and treatment of hyperkalemia in diseases associated with insulin resistance, such as obesity and Type 2 diabetes mellitus. The proposed research is innovative in that we will directly study the regulation of renal BK channels in insulin resistance and will employ novel reagents and cutting-edge techniques to understand the consequences of defective FIKS for hyperkalemia. Through the proposed studies, we will also learn about mechanisms of insulin signaling in the kidney in the insulin resistance syndrome and the role of diet in determining cardiovascular outcomes in this syndrome.