Probing the Role of Mitochondrial Short-chain Carbon Homeostasis in the Hypertrophied and Failing Heart

摘要 目前心力衰竭 (HF) 的治疗主要针对适应不良的心外神经激素回路 以“一刀切”的方式。对基于机制的直接疗法的需求尚未得到满足 在心力衰竭早期阶段以心脏为目标。越来越多的证据表明，在发展过程中 心力衰竭时，线粒体 ATP 生成失调。一个完善的代谢特征 心脏衰竭是从使用脂肪酸作为正常心脏的主要燃料来源转向其他燃料，例如 如葡萄糖。这种燃料转移发生在心脏肥大和衰竭发展的早期。然而， 这种心脏燃料转换与线粒体呼吸功能逐渐减弱的潜在联系 HF 发展过程中 ATP 产生能力尚未建立，超出了单纯的关联。 在当前的资助期间，我们取得了一系列发现，支持以下前提： 心脏脂肪酸氧化（FAO）紊乱会导致线粒体能量功能障碍和 HF 的发展包括： 1) 识别粮农组织路径最后步骤中的独特“瓶颈” 为辅酶 A (CoA) 等关键辅因子的消耗和还原当量的转移奠定基础 远离电子传递链的复合体I； 2）酮体，3-羟基丁酸酯（3OHB），一种高效的酮体 绕过长链FAO的心脏燃料，减少小和小心脏的心脏重塑和心室功能障碍 心力衰竭的大型动物模型； 3) 增加心脏线粒体氧化能力，包括FAO通量，通过 心脏特异性删除编码 RIP140 (Nrip1) 的基因可防止心脏肥大生长并减少 小鼠压力超负荷引起的心脏重塑和功能障碍。这些发现导致中央 该多PI R01更新提案的假设：肥厚心脏结果中FAO的下调 -氧化螺旋内的瓶颈导致线粒体 ATP 能力降低 生产和；减少的粮农组织通量为利用葡萄糖和 心脏肥大生长所需的合成代谢途径的其他来源。这些假设将 通过两个目标进行测试。在目标1中，我们将对心脏功能、线粒体、 野生型、csRIP140-/-（高FAO）和csPPARα-/-（低FAO）小鼠的蛋白质组和基因组反应 小鼠心力衰竭的发生。目标 2 旨在确定 RIP140 缺陷防御的机制 对抗病理性心脏肥厚生长。拟议工作的长期目标是确定 导致衰竭心脏中线粒体能量崩溃的机械事件并识别节点 监管点可以作为候选治疗策略，旨在重新平衡燃料利用和 增强线粒体 ATP 生成能力，针对心力衰竭的早期阶段。

SUMMARY Current therapies for heart failure (HF) are largely directed at maladaptive extra-cardiac neurohormonal circuits in a “one size fits all” approach. There is a significant unmet need for mechanism-based therapies directly targeting the heart during early stages of HF. Increasing evidence has shown that during the development of heart failure, mitochondrial generation of ATP becomes dysregulated. A well-established metabolic signature of the failing heart is a shift from using fatty acids as the chief fuel source of the normal heart, to other fuels such as glucose. This fuel shift occurs early in the development of cardiac hypertrophy and failure. However, the potential linkage of this cardiac fuel switch to the progressive diminution in mitochondrial respiratory function and ATP producing capacity during the development of HF has not been established beyond a mere association. During the current funding period, we have made a series of discoveries that support the premise that disturbances in cardiac fatty acid oxidation (FAO) contribute to mitochondrial energetic dysfunction and the development of HF including: 1) identification of distinct “bottlenecks” in the terminal steps of the FAO pathway setting the stage for depletion of key cofactors such as Coenzyme A (CoA) and diversion of reducing equivalents away from complex I of the electron transport chain; 2) the ketone body, 3-hydroxybutryate (3OHB), an efficient cardiac fuel that bypasses long-chain FAO, reduces cardiac remodeling and ventricular dysfunction in small and large animal models of HF; and 3) increasing cardiac mitochondrial oxidative capacity, including FAO flux, by cardiac-specific deletion of the gene encoding RIP140 (Nrip1) prevents cardiac hypertrophic growth and reduces cardiac remodeling and dysfunction caused by pressure overload in mice. These findings have led to the central hypotheses of this multi-PI R01 renewal proposal: Downregulation of FAO in the hypertrophied heart results in bottlenecking within the -oxidation spiral leading to reduced capacity for mitochondrial ATP production and; reduced FAO flux sets the stage for utilization of carbon sources from glucose and other sources in anabolic pathways necessary for cardiac hypertrophic growth. These hypotheses will be tested by two aims. In Aim 1, we will conduct in-depth assessment of the cardiac functional, mitochondrial, proteomic and genomic response of wild-type, csRIP140-/- (high FAO), and csPPAR-/- (low FAO) mice during development of HF in mice. Aim 2 is designed to determine the mechanisms whereby RIP140 deficiency defends against pathological cardiac hypertrophic growth. The long-term objectives of the proposed work are to define the mechanistic events leading to mitochondrial energetic collapse in the failing heart and to identify nodal regulatory points that could serve as candidate therapeutic strategies aimed at re-balancing fuel utilization and enhancing mitochondrial ATP-producing capacity aimed at the early stages of heart failure.