Novel mechanisms regulating VLDL secretion and non-alcoholic fatty liver diseases

摘要 非酒精性脂肪性肝病（NAFLD）是目前一种高度流行的肝病形式。nafld是 以肝细胞中脂质蓄积为特征，可进展为非酒精性脂肪性肝炎 （NASH），其增加了肝细胞死亡、炎症和纤维化。的分子基础 NAFLD/NASH的发生和发展仍然知之甚少。因此，没有有效的治疗方法 对于这种迅速发展的健康问题的治疗是可用的。因此，在这方面存在明显的未满足的研究需求。 区肝脏极低密度脂蛋白（VLDL）分泌在调节肝内和肝外脂肪中是必不可少的。 血管内脂质稳态和VLDL分泌受损导致脂肪变性。细胞膜蛋白1 VMP1是一种ER膜蛋白，通过促进自噬体的关闭来调节自噬。 最近的证据表明，VMP1在脂蛋白分泌中起着关键作用，与其自身的功能无关。 自噬功能在培养的肝癌细胞和斑马鱼。该应用程序的主要优点是 了解VMP1调节脂质代谢和NAFLD进展的作用和机制。 我们的建议是重要的，因为它是研究一种新的途径，调节脂质代谢， NAFLD的发展。在此应用程序下进行的工作将丰富NAFLD领域关于 VMP1作为ER-线粒体和ER-ERGIC-高尔基体串扰的中心调节物的关键作用， NAFLD发展过程中VLDL的多层分泌我们的总体科学前提是， 阐明了VMP1的损失损害VLDL分泌并促进NAFLD/NASH的途径。我们 关键的初步数据支持了这一提议，包括：1）肝细胞特异性缺失VMP1， 小鼠VLDL分泌受损，导致肝脂肪变性和NASH; 2）VMP1对协调ER-1和ER-2的表达至关重要。 线粒体和ER-高尔基体相互作用调节NAFLD中VLDL的分泌。三个具体目标是 建议：1）确定VMP1的缺失降低肝磷脂酰胆碱的机制， 磷脂酰乙醇胺含量，导致VLDL分泌受损和NASH; 2）测定磷脂酰乙醇胺含量， VMP1缺失降低COPII和ERGIC-53蛋白，损害VLDL ER-高尔基体的机制 运输和VLDL分泌;和3）确定VMP1在改善饮食诱导的受损VLDL中的作用 分泌物和NASH。这项工作的长期目标是确定VMP1依赖的途径， NAFLD/NASH的发病机制，并通过靶向VMP1开发潜在的策略。

Abstract Nonalcoholic fatty liver disease (NAFLD) is currently a highly prevalent form of liver disease. NAFLD is characterized by the accumulation of lipids in hepatocytes that can progress to nonalcoholic steatohepatitis (NASH), which has increased hepatocyte death, inflammation and fibrosis. The molecular basis of the development and progression of NAFLD/NASH are still poorly understood. As a result, no effective therapeutic treatments for this burgeoning health problem are available. Thus, there is a clear unmet research need in this area. Hepatic very-low-density lipoprotein (VLDL) secretion is essential in regulating intrahepatic and intravascular lipid homeostasis, and impaired VLDL secretion leads to steatosis. Vacuole membrane protein 1 (VMP1) is an ER membrane protein that regulates autophagy by promoting the closure of autophagosomes. Recent evidence demonstrates that VMP1 plays a critical role in lipoprotein secretion independent of its autophagy function in cultured hepatoma cells and zebrafish. The major OBJECTIVES of this application are to understand the role and mechanisms by which VMP1 regulates lipid metabolism and NAFLD progression. Our proposal is SIGNIFICANT because it is to investigate a novel pathway in regulating lipid metabolism and development of NAFLD. Work performed under this application will enrich the NAFLD field regarding the critical role of VMP1 as a central regulator of ER-mitochondria and ER-ERGIC-Golgi crosstalk which regulate VLDL secretion at multilayers in the development of NAFLD. Our overall SCIENTIFIC PREMISE is that elucidating pathways whereby loss of VMP1 impairs VLDL secretion and promotes NAFLD/NASH. Our proposal is supported by KEY PRELIMINARY DATA including: 1) Hepatocyte-specific deletion of VMP1 in mice impaired VLDL secretion resulting in hepatic steatosis and NASH; 2) VMP1 is critical to concert ER- mitochondria and ER-Golgi crosstalk to regulate VLDL secretion in NAFLD. Three SPECIFIC AIMS are proposed: 1) Determine the mechanisms by which loss of VMP1 decreases hepatic phosphatidylcholine and phosphatidylethanolamine content resulting in impaired VLDL secretion and NASH; 2) Determine the mechanisms by which loss of VMP1 decreases COPII and ERGIC-53 proteins, impairs VLDL ER-Golgi trafficking and VLDL secretion; and 3) Determine the role of VMP1 in ameliorating diet-induced impaired VLDL secretion and NASH. The LONGTERM GOAL of this work is to identify VMP1-dependent pathways in the pathogenesis of NAFLD/NASH and develop potential strategies by targeting VMP1.