Maladaptive Expression of Metabolic Enzymes and Activity in Heart Failure

 描述(由申请人提供)；这项工作的总体目标是阐明和缓解可能导致心功能障碍和在压力超负荷心脏中进展为失代偿性肥厚的不适应性代谢重构的机制。这一建议源于我们实验室的两项新发现：1)心脏中储存的甘油三酯(TG)是相当动态的，但在衰竭的心脏中，TG的周转是缓慢的。 甘油三酯含量，后者发现以来在无糖尿病的心力衰竭患者中得到证实。甘油三酯周转率的损失减少了甘油三酯对线粒体脂肪酸氧化的贡献，更重要的是，损害了PPARα的甘油三酯脂解活性。我们已经报道，虽然棕榈酸酯可以维持肥厚心脏中甘油三酯代谢和PPARα活性的降低，但油酸盐可以使这些参数正常化；2)我们的实验室首次报道了肝脏限速酶--肉碱棕榈酰转移酶I(CPT1)在肥厚心脏中的蛋白质含量增加。我们还发现，在健康心脏中，肝脏CPT1(CPT1A)的急性表达导致了两个令人惊讶的结果：粮农组织矛盾的减少和心肌心钠素mRNA的升高，这两个都是经典观察到的对病原性应激的反应。初步数据显示，CPT1A的表达被MIR-370抑制，而在肥厚的心脏中，Mir370的含量很低。因此，我们假设：1)补充油酸丰富的饮食对横断性主动脉缩窄大鼠的心脏有好处，a)维持甘油三酯的周转和PPARα靶基因的表达，b)影响神经酰胺的形成，c)从而减轻功能障碍和失代偿。2)肥厚心脏CPT1a的升高是影响心脏失代偿的早期代谢重塑的关键步骤，并与肥厚的信号转导有关。3)肥厚心脏中CPT1a的增加通过CPT1乙酰化和丙二酸化的改变与FAO的减少有关，这些变化通过恢复Mir-370的含量来响应CPT1a的调节。目的1)比较棕榈酸酯(三棕榈素)和富油酸酯(三油酸脂)饮食对大鼠全心转移术后心脏失代偿的影响，以及(B)研究三酸甘油酯和三棕榈素饮食对大鼠全心转移术后甘油三酯(TG)周转率、PPARα靶基因表达、低密度脂蛋白A氧化和脂毒性酰基中间体的影响。目的2确定异构体向CPT1A(肝脏)表达的转变在LCFA氧化减少和进展为失代偿和早期心衰中所起的作用。心脏特异的CPT1a缺失小鼠，不能增加CPT1a对TAC的反应，将检查对TAC的功能和肥大反应。通过CPT1b(肌肉异构体)含量和CPT1乙酰化/丙二酸化的排他性改变改变粮农组织的可能性，将在限制性缺乏CPT1a反应的情况下阐明。目的3阐明CPT1a在TAC过程中由于miR-370的减少而引起的潜在的非适应性上调，以及CPT1a的表达在这两种CPT1亚型的乙酰化和丙二酸化中的作用。在大鼠心脏中，TAC导致的低MIR-370将被急剧过度表达的MIR-370所抵消，以抑制CPT1A及其下游效应。

 DESCRIPTION (provided by applicant); The overall goal of this work is to elucidate and mitigate mechanisms of maladaptive metabolic remodeling that may contribute to cardiac dysfunction and the progression to decompensated hypertrophy in the pressure overloaded heart. The proposal originates from two novel findings in our laboratory: 1) that stored triglyceride (TG) in the heart is quite dynamic, but TG turnover is slow in the failing heart as is TG content, the latter finding since being confirmed in heart failure patients without diabetes. The loss of TG turnover reduces the contribution of long chain fatty acids (LCFA) from TG to mitochondrial fatty acid oxidation (FAO) and importantly, impairs TG lipolytic activation of PPARα. We have reported that while palmitate sustains this reduced TG metabolism and PPARα activation in hypertrophied hearts, oleate normalizes each of these very same parameters; 2) our lab first reported increased protein content of the liver isoform of the rate limiting enzyme in FAO, carnitine palmitoyltransferase I (CPT1) in hypertrophied hearts. We also found acute expression of the liver CPT1 (CPT1a) in healthy hearts induced two surprising results; a paradoxical reduction in FAO and elevated myocardial atrial natriuretic peptide mRNA, both classically observed responses to pathogenic stress. Preliminary data show CPT1a expression is suppressed by Mir-370 and that Mir370 content is low in hypertrophied hearts. Thus, we hypothesize that: 1) Supplying an oleate rich diet provides benefits to rat hearts following transverse aortic constriction (TAC) by a) maintaining TG turnover and PPARα target gene expression, b) influencing the formation of ceramide species, and c) thereby attenuating dysfunction and decompensation. 2) Increased CPT1a in hypertrophied hearts is a key step in the early metabolic remodeling that influences cardiac decompensation and is linked to hypertrophic signaling. 3) Increased CPT1a in hypertrophied hearts is linked to reduce FAO via changes in CPT1 acetylation and malonylation, and these changes respond to CPT1a regulation via restored Mir-370 content. Aim 1 a) determines effects of palmitate- (tripalmitin) versus oleate-rich (triolein) diets on decompensation after TAC in rat hearts, and b) determines if triolein and tripalmitin diets post-TAC affect TG turnover, PPARα target gene expression, LCFA oxidation and lipotoxic acyl-intermediates. Aim 2 determines the role of the isoform shift to CPT1a (liver) expression in the reduced LCFA oxidation and progression toward decompensation and early HF. Cardiac specific, CPT1a null mice, that are unable increase CPT1a in response to TAC, will be examined for functional and hypertrophic responses to TAC. The potential for altered FAO through exclusive changes in CPT1b (muscle isoform) content and CPT1 acetylation/malonylation, will be elucidated in the restricted absence of a CPT1a response. Aim 3 elucidates potentially maladaptive upregulation of CPT1a, due to reduced Mir-370 during TAC, and the role of CPT1a expression in acetylation and malonylation of both CPT1 isoforms. Low Mir-370 following TAC in rat hearts will be countered by acutely overexpressing Mir-370 to suppress CPT1a and downstream effects.