NMR of Mitochondrial Transporters in Cardiac Hypertrophy

描述（由申请人提供）： 拟议研究的总体目标是阐明和对抗脂肪酸和碳水化合物代谢的能量生产效率低下，这是由压力超负荷心脏中替代途径的代偿性招募和代谢基因表达的改变造成的。目的是产生新的代谢策略，以减轻导致明显心力衰竭的心肌病的发展。正在进行的工作已经阐明：1）在心脏肥大中增加的NADPH依赖性苹果酸酶（ME）表达，增加了进入TCA循环第二跨度的回补流量，并可能影响脂肪酸氧化和储存的调节，对收缩性有明显影响; 2）肝脏（L）肉毒碱棕榈酰转移酶I（L-CPT 1）亚型的表达增加在肥大的心脏中，这与减少的脂肪酸氧化相一致; 3）在肥大的心脏中，三酰甘油（TAG）池的含量和周转率两者的大的减少与TAG对脂肪酸氧化的贡献的损失相一致。基于当前资助期的这些关键发现，实验测试了以下假设：需要正常的TAG含量和周转来维持对脂肪酸氧化的基线脂解贡献，这对收缩性的代谢支持的灵活性至关重要，并且部分地，由于通过苹果酸酶的回补和通过L-CPT 1的脂肪酸氧化的适应不良的变化，影响收缩的代谢效率。将使用遗传改变的大鼠心脏和具有压力超负荷肥大的转基因小鼠心脏的动态模式13 C NMR来测试该假设。目的1利用腺病毒介导的正常心肌ME过表达和肥大心肌ME的RNA抑制，研究ME表达增加对肥大大鼠心肌甘油三酯动力学和氧化还原调节的影响。该目的还测试了脂肪酸链长度和膳食脂肪对心脏肥大中TAG动力学的影响以及由于ME表达差异引起的丙酮酸盐的代谢命运。目的2：通过L-CPT 1 RNA抑制，检测L-CPT 1表达增加对肥大大鼠心脏脂肪酸储存动力学和氧化之间的相互作用和平衡的功能意义。目的3探讨增加脂肪酸摄取和PPAR 1表达对脂肪酸转运蛋白1（FATP 1）过表达或低表达转基因小鼠肥大心脏TAG动力学和氧化的影响。而不是调查一个单一的酶，我们提出了一个综合的方法来调查潜在的适应不良的变化，在心肌肥厚的代谢酶表达，同时探索潜在的机制，减少TAG动力学在肥大的功能意义。预期的研究结果将有助于一个基本的，机械的理解，一个具有临床意义的局部问题，这是心脏脂质动力学失调和收缩功能障碍之间的联系，在失代偿性肥大的发病机制。

DESCRIPTION (provided by applicant): The overall objective of the proposed research is to elucidate and counter inefficiencies in fatty acid and carbohydrate metabolism for energy production, imposed by compensatory recruitment of alternative pathways and altered metabolic gene expression in pressure overloaded hearts. Aims are intended to yield new metabolic strategies to mitigate the development of cardiomyopathy leading to overt heart failure. Ongoing work has elucidated 1) increased NADPH-dependent malic enzyme (ME) expression in cardiac hypertrophy that increases anaplerotic flux into the second span of the TCA cycle and may impact on regulation of fatty acid oxidation and storage, with apparent effects on contractility; 2) increased expression of the liver (L) isoform of carnitine palmitoyltransferase I (L-CPT1) in hypertrophied hearts that coincides with reduced fatty acid oxidation; 3) large reductions in both content and turnover rates of the triacylglyceride (TAG) pool in hypertrophied hearts that coincide with a loss of the contribution from TAG to fatty acid oxidation. Based on these key findings of the current funding period, experiments test the hypothesis that normal TAG content and turnover are required to maintain baseline lipolytic contributions to fatty acid oxidation, which is critical to the flexibility of the metabolic support of contractility, and that dysregulation of lipid storage dynamics in cardiac hypertrophy, in part, due to maladaptive shifts in anaplerosis via malic enzyme and fatty acid oxidation via L- CPT1, affects the metabolic efficiency of contraction. The hypothesis will be tested using dynamic-mode 13C NMR of genetically altered rat hearts and transgenic mouse hearts with pressure overload hypertrophy. Aim 1 investigates the effects of increased ME expression on both triglyceride dynamics and redox regulation in hypertrophied rat hearts using adenoviral-based ME overexpression in normal hearts and RNA suppression of ME in hypertrophy. This aim also tests the effects of fatty acid chain length and dietary fat on TAG dynamics in cardiac hypertrophy and the metabolic fate of pyruvate due to differential ME expression. Aim 2 tests the functional significance of increased L-CPT1 expression on the reciprocal activity and balance between fatty acid storage kinetics and oxidation in hypertrophied rat hearts using L-CPT1 RNA inhibition. Aim 3 explores the influences of augmented fatty acid uptake and PPAR1 expression on the changes in TAG dynamics and oxidation in hypertrophied hearts of transgenic mice with either fatty acid transporter 1 (FATP1) overexpression or low overexpression of PPAR1. Rather than investigate a single enzyme, we propose an integrative approach to investigate potentially maladaptive changes in metabolic enzyme expression in cardiac hypertrophy, while exploring the potential mechanisms for, and functional significance of reduced TAG dynamics in hypertrophy. The anticipated findings will contribute a basic, mechanistic understanding to a topical problem of clinical importance, which is the link between dysregulation of cardiac lipid dynamics and contractile dysfunction in the pathogenesis of decompensated hypertrophy.