Cardiac dysfunction after ischemic AKI in mice

摘要 本提案的总体目标是确定急性肾损伤（阿基）导致 急性心功能不全临床上，AKI介导的心功能不全被称为心肾综合征型 3（CRS3）。CRS 3的基础机制尚未得到很好的理解， 已经被确认。我们最近证明缺血性阿基导致小鼠心功能障碍， 与心脏ATP水平降低50%有关。因此，心脏的能量代谢和生产 在阿基期间受损，并且是CRS 3的基本特征。为了鉴定CRS 3的介导物，我们 检查了血浆和心脏代谢物。我们希望能发现循环代谢物水平的增加 可能会影响心脏能量代谢相反，我们发现， 维持心脏能量产生和抗氧化防御在阿基后的血浆和心脏中缺乏， 包括十几种氨基酸和抗氧化剂谷胱甘肽。在心脏应激期间，氨基酸 ATP生产的基本底物。谷氨酰胺是特别重要的，因为它可以被代谢为 ATP和谷胱甘肽合成的底物。麸质是心脏中含量最丰富的抗氧化剂 并且对于维持正常的能量产生是至关重要的， 线粒体功能和抑制氧化磷酸化（OXPHOS）。OXPHOS发生在线粒体内 并且通常是心脏ATP产生的主要机制。我们的初步数据显示， 阿基：1）心脏线粒体功能和OXPHOS受损，2）心脏超氧化物（O2●-，一种ROS） 谷氨酰胺显著增加心肌ATP，降低O2●-。基于这些 数据，我们的总体假设是，在阿基期间缺乏能量底物和谷胱甘肽前体， 导致活性氧增加，OXPHOS减少，ATP产生减少， 功能障碍我们有三个目标。目的1：通过代谢途径确定阿基对心脏能量代谢的影响。 通量分析目的2：确定谷氨酰胺改善心肌ATP生成的机制， 阿基，在体内，假设谷氨酰胺会减少心脏O2●-，增加ATP的产生，并改善 线粒体和心脏功能。目的3：确定促进谷氨酰胺代谢的底物 阿基后的心脏ATP产生，离体，假设代谢为谷胱甘肽是主要的 谷氨酰胺有益的机制。由于阿基的并发症长期以来一直被认为是由于 代谢废物和其他物质的积累，这些物质可以通过透析去除以使患者受益， 我们的总体假设，即底物缺乏是一种伤害机制，是一种范式转变，挑战了 这是肾脏病学中最基本的概念之一， 阿基患者，尤其是透析患者。

Abstract The overall goal of this proposal is to determine the mechanisms by which acute kidney injury (AKI) leads to acute cardiac dysfunction. Clinically, AKI-mediated cardiac dysfunction is known as cardiorenal syndrome type 3 (CRS3). The mechanisms underpinning CRS3 are not well understood and few plausible mediators of CRS3 have been identified. We recently demonstrated that ischemic AKI causes cardiac dysfunction in mice which was associated with a 50% reduction in cardiac ATP levels. Thus, cardiac energy metabolism and production is impaired during AKI and is a fundamental characteristic of CRS3. To identify mediators of CRS3, we examined plasma and cardiac metabolites. We expected to identify increased levels of circulating metabolites that might affect cardiac energy metabolism. Rather, we found that numerous metabolites necessary to maintain cardiac energy production and anti-oxidant defense were deficient in the plasma and heart after AKI, including over a dozen amino acids and the anti-oxidant glutathione. During cardiac stress, amino acids are essential substrates for ATP production. Glutamine is particularly important since it can be metabolized to substrates for both ATP and glutathione synthesis. Glutathione is the most abundant anti-oxidant in the heart and is critical to maintain normal energy production since excess reactive oxygen species (ROS) impairs mitochondrial function and inhibits oxidative phosphorylation (OXPHOS). OXPHOS occurs within mitochondria and is normally the major mechanism of cardiac ATP production. Our preliminary data demonstrate that during AKI: 1) cardiac mitochondrial function and OXPHOS are impaired, 2) cardiac superoxide (O2●-, an ROS) is significantly increased, 3) glutamine significantly increases cardiac ATP and reduces O2●-. Based on these data, our overall hypothesis is that the deficiency of energy substrates and glutathione precursors during AKI results in increased reactive oxygen species, reduced OXPHOS, reduced ATP production, and cardiac dysfunction. We have 3 Aims. Aim 1: Determine the effect of AKI on cardiac energy metabolism via metabolic flux analysis. Aim 2: Determine the mechanisms by which glutamine improves cardiac ATP production after AKI, in vivo, with the hypothesis that glutamine will reduce cardiac O2●-, increase ATP production, and improve mitochondrial and cardiac function. Aim 3: Determine the substrates of glutamine metabolism that improve cardiac ATP production after AKI, ex vivo, with the hypothesis that metabolism to glutathione is the primary mechanism of glutamine benefit. Since the complications of AKI have long been considered to be due to the accumulation of metabolic wastes and other substances that may be removed by dialysis for patient benefit, our overall hypothesis that substrate deficiency is a mechanisms of harm is a paradigm shift that challenges one of the most fundamental notions in nephrology and will have wide ranging implications regarding the care of patients with AKI, particularly regarding dialysis.