Peli1对病理性心肌肥大脂质氧化的调控作用与机制研究

Maintenance of the inherent metabolic profile of the heart and, as a result, maintaining mitochondrial oxidative metabolism without switching to glucose reliance is beneficial for optimal function and energetics during the development of pathological cardiac hypertrophy. Peli1 belongs to E3 ligase family, and HNF4α is a key nuclear receptor regulates lipid metabolism. And we found that Peli1 knocout could improve the expression of key genes involved in FAO which impaired by TAC. And, HNF4α protein was slightly up-regulated in TAC heart compared to sham group, but HNF4α increased more in Peli1 knockout mice heart. Notably, HNF4α ubiquitination was positively correlated with Peli1, and greatly increased after Peli1 knockout. In vitro, mechanical stretch significantly induced Peli1 expression, meanwhile, Peli1 knockout protected cardiomyocytes hypertrophy by improving the expression of FAO gene, significantly. In summary, we hypothesize that Peli1 over expression due to pressure overload impairs myocardial FAO. The mechanism is mainly because that Peli1 promotes the ubiquitination of HNF4α and inhibits the compensatory effect of HNF4α, ofcourse Peli1 knockout can reverse the above phenomenon. If do, it will provide a novel theoretical basis for clinical treatment of pathological cardiac hypertrophy.

新研究观点，维持心肌细胞线粒体FAO可保护病理心肌肥大。Peli1是一种具有E3泛素连接酶活性的蛋白；HNF4α是调节脂质代谢的核受体。前期实验，发现Peli1敲除能改善TAC所致FAO关键基因的表达下降；TAC术后，HNF4α蛋白轻微上调，Peli1敲除后HNF4α明显增多；TAC术后，组织中HNF4α泛素化与Peli1正相关，Peli1敲除后HNF4α泛素化减少。细胞实验，Peli1敲除改善机械牵张所致细胞肥大，同时提高FAO基因的mRNA水平及增强脂肪酸氧化；还发现Peli1过表达可降低HNF4α的水平，而MG132可以抑制这种作用。由此提出假说，Peli1参与调控心肌细胞的脂质氧化；其机制与Peli1促进HNF4α的泛素化修饰，抑制HNF4α对病理性心肌肥大脂质氧化的代偿作用有关。若顺利完成可为临床治疗病理性心肌肥大提供全新理论依据。

阐明压力过负荷导致病理性心肌肥大的发生机制，寻找能够延缓心肌肥大进展的有效生物学靶点，是目前基础研究和临床实践亟待解决的重大问题之一。借助Peli1敲除鼠、AAV9-HNF4a过表达、原代心肌细胞等工具与实验。我们发现，Peli1敲除改善TAC诱导的病理性心肌肥大，增强心肌组织中HNF4a及下游靶基因的表达，改善机械牵张诱导的心肌细胞肥大并增强细胞脂质代谢；AAV9-HNF4a改善TAC诱导的心肌肥大并增强脂质代谢基因表达；过表达HNF4α改善血管紧张素II诱导的心肌细胞肥大并增强细胞脂质代谢；Peli1主要促进HNF4a蛋白，K307，K309位点的泛素化。综上，我们得出Peli1参与调控心肌细胞的脂质氧化，从而影响压力过负荷所致病理性心肌肥大的发生发展，其机制主要与Peli1通过其E3泛素连接酶活性促进HNF4α的泛素化修饰，抑制HNF4α对病理性心肌肥大脂质氧化的代偿作用有关。

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