NT-PGC-1α 在心力衰竭发生发展中的作用及其机制

We have reported that the myocardial menergy expenditure and serum metabolites detected by 1H-NMR in patients with heart failure are significant different from healthy people. The PPARr coactivator-1α(PGC-1α) plays a key role in myocardial fuel metabolism and heart failure. As described in most reports，PGC-1α is downregulated during the development of heart failure.However,chronic overexpression of PGC-1α in heart leads to significant mitochondrial structural abnormalities and a severe cardiomyopathy. Rencently NT-PGC-1α, a novel, biologically active splice variant of PGC-1α was found, which retains the ability to interact with and transactivate nuclear hormone receptors through its N-terminal transactivation domain. In contrast to full-length PGC-1α which resides in the nucleus, NT-PGC-1α cycles between the nucleus and cytoplasm and has long half-life. However, it is still not clear whether NT-PGC-1α is relevant to the ocurrence and development of heart failure and whether it is do good to heart failure. To clarify the protective role and mechanism of NT-PGC-1α in heart failure, the effect on the concentration of NT-PGC-1α and PGC-1α in nucleus and cytoplasm will be observed by using different agonist, and the variation of myocardial fuel metabolism, function of heart and mitochondrial will be studied after the administration of the agonist or inhibitor of NT-PGC-1α in pressure-overloaded wild type mice and FL-PGC-1α-/- mice. In order to investigate the pathophysiological significance of NT-PGC-1α in myocardial fuel metabolism and the development of heart failure, the influence on the myocardial fuel metabolism and heart function will also be assessed after changing the ratio of nuclear concentration to cytoplasmic concentration by special medicine in wild type mice and FL-PGC-1α-/- mice. Our study will further clarify the relationship between heart failure and cardiac energy metabolism and suggest that NT-PGC-1α can be an attractive target for the treatment of heart failure.

我们报告了心衰患者心肌生物能量消耗增加和血清代谢1H－NMR图谱与健康人有明显差异。已知PGC-1α与心肌能量代谢及心衰密切相关，心衰时PGC-1α下调，但长期过表达可导致线粒体结构异常和心肌病。NT-PGC-1α是新发现的PGC-1α N末端同型异构体，有相似的转录激活和核受体结合区，且可位于胞核与胞浆中和半衰期长。本研究通过比较几种激动剂对心肌细胞胞浆和胞核内NT-PGC-1α和PGC-1α浓度的影响；使用NT-PGC-1α激动剂和抑制剂后，处于压力负荷心衰模型不同阶段的野生型和FL-PGC-1α-/-小鼠心肌能量代谢、线粒体功能及心功能变化；改变NT-PGC-1α胞浆/胞核浓度比值对野生型和FL-PGC-1α-/-心衰小鼠心肌能量代谢和心功能的影响，拟证明NT-PGC-1α具有心衰保护作用，探索NT-PGC-1α调节心肌能量代谢在心衰发生发展中的病理生理意义，为心衰提供新的治疗靶点。

代谢重构在心力衰竭发生发展中起有重要的作用。本项目对NT-PGC-1α在心力衰竭发生发展中的作用及其机制进行了探索。研究结果显示：(1)体外实验中观察到：NT-PGC-1α主要分布于细胞浆，PGC-1α主要分布在细胞核。P300、AICAR可以增加NT-PGC-1α、PGC-1α的表达，其作用可分别被C646、ara-A阻断；同样作为AMPK激活剂的二甲双胍具有与血管紧张素II（Ang II）不同的激活NT-PGC-1α、PGC-1α的作用，且不被血管紧张素受体抑制剂（氯沙坦）抑制；血清饥饿和低糖环境也可激活NT-PGC-1α、PGC-1α；提示NT-PGC-1α、PGC-1α具有可调节性，可通过不同刺激改变其表达水平。NT-PGC-1α可通过PPAR-α通路增加线粒体脂肪酸氧化代谢。PPAR-1α抑制剂MK886可以抑制过表达NT-PGC-1α所致的脂肪酸代谢增强，其抑制作用具有剂量依赖性。在心肌细胞功能实验中发现NT-PGC-1α通过增加线粒体功能可减轻不良刺激对心肌细胞的影响。采用核输出蛋白抑制剂selinexor和腺病毒ad-NLS-NT-PGC-1α转染可增加NT-PGC-1α的核内表达，核内NT-PGC-1α表达增加可增强其下游基因表达，并减轻Ang II和去甲肾上腺素所致的心肌肥厚。显著过表达NT-PGC-1α主要是通过增加核内表达介导下游调节糖、脂代谢、抗氧化应激、抗增值作用的因子表达增高。 (2)在体实验中发现： FL-PGC-1α-/-小鼠难以制备心梗后心衰模型，提前给与核输出蛋白抑制剂selinexor也不能降低转基因鼠FL-NT-PGC-1α-/-心肌梗死模型的死亡率。在心衰小鼠模型发现心功能恶化程度与PGC-1α、NT-PGC-1α表达下降相一致，而且其下游PPAR-α、CPT1/2、Acadm、SOD2/3的表达也下降，说明其脂肪酸代谢以及抗氧化能力下降。selinexor能够降低心衰小鼠模型的心重体重比值，但并不能增加MI后小鼠生存率和改善心功能。