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低效率，以产生能量，由代偿性招募替代途径和改变的代谢基因表达在压力过载的心脏中施加。目的是产生新的代谢策略，以减轻心肌病的发展，导致明显的心力衰竭。正在进行的研究已经阐明了1)心肌肥厚中nadph依赖性苹果酸酶（ME）表达的增加，增加了进入TCA循环第二段的复跳通量，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)肥厚心脏中肉碱棕榈酰基转移酶I （L- cpt1）肝脏(L)异构体的表达增加，与脂肪酸氧化减少相一致；3)肥大心脏中甘油三酯（TAG）库的含量和周转率大幅降低，这与TAG对脂肪酸氧化的贡献丧失相一致。基于当前资助期的这些关键发现，实验验证了这样的假设：正常的TAG含量和周转量是维持脂肪酸氧化的基线脂溶作用所必需的，而脂肪酸氧化对代谢支持收缩性的灵活性至关重要；心脏肥肥性中脂质储存动力学的紊乱，部分是由于苹果酸酶和L- CPT1介导的脂肪酸氧化的不适应转变。影响收缩代谢效率。该假设将使用动态模式13C核磁共振基因改变的大鼠心脏和转基因小鼠心脏与压力过载肥大进行测试。目的1通过在正常心脏中以腺病毒为基础的ME过表达和在肥大中RNA抑制ME，研究ME表达增加对肥大大鼠心脏甘油三酯动力学和氧化还原调节的影响。本研究还旨在测试脂肪酸链长度和膳食脂肪对心肌肥厚中TAG动态的影响，以及由于ME表达差异而导致的丙酮酸代谢命运。目的2通过抑制L-CPT1 RNA，检测L-CPT1表达增加对肥大大鼠心脏脂肪酸储存动力学和氧化相互活性及平衡的功能意义。Aim 3探讨脂肪酸摄取增强和PPAR1表达对脂肪酸转运蛋白1 （FATP1）过表达或低过表达转基因小鼠肥大心脏TAG动力学和氧化变化的影响。我们提出了一种综合的方法来研究心肌肥厚中代谢酶表达的潜在不适应变化，而不是研究单一的酶，同时探索肥厚中TAG动力学降低的潜在机制和功能意义。预期的发现将有助于对一个具有临床重要性的局部问题的基本机制理解，即在失代偿性肥厚的发病机制中，心脏脂质动力学失调和收缩功能障碍之间的联系。

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.