Mechanisms and metabolic implications of LRP130 in NAFLD

描述(由申请人提供)：非酒精性脂肪性肝病(NAFLD)是美国肝病的主要原因。它跨越了从脂肪肝到称为NASH(非酒精性脂肪性肝炎)的叠加炎症的临床范围。NASH易导致不可逆转的肝硬变和肝细胞癌，这突出了确定潜在机制的必要性。在NAFLD中，有缺陷的线粒体释放出过量的活性氧(ROS)。线粒体ROS之所以引起人们的兴趣，是因为它与胰岛素抵抗和炎症有关，这是NAFLD的两个关键特征。线粒体功能障碍的机制尚不清楚；因此，了解其机制基础可能会减轻NAFLD。我们的初步数据表明，LRP130是线粒体功能和ROS的重要调节因子。在NAFLD中，我们观察到LRP130以疾病特异性的方式减弱。值得注意的是，小鼠肝脏中LRP130的缺失会导致胰岛素抵抗和炎症。从机制上讲，LRP130调节整个线粒体基因组。值得注意的是，LRP130深刻地影响呼吸链的形成、呼吸和超氧化物的形成。我们推测LRP130是肝脏线粒体缺陷与NAFLD进展之间的分子联系。我们提出了三个目的来质疑我们的假设：(1)评估LRP130在线粒体功能和超氧化物形成中的作用。LRP130对线粒体生物能量学的影响将通过细胞和小鼠的功能丧失和功能获得模型进行评估。我们将使用蓝色天然凝胶电泳法对呼吸链超复合体进行评估。线粒体功能将通过耗氧量、复合体活性、膜电位和超氧阴离子测量来衡量。(2)探讨LRP130在非酒精性脂肪性肝病中的作用。用高脂肪饮食挑战小鼠会导致脂肪肝。肝脏中缺乏LRP130的小鼠将使用一系列分析方法进行胰岛素敏感性和炎症评估：高胰岛素-正常血糖钳夹、胰岛素信号免疫检测、炎症组织学评估和细胞因子分析。将使用肝脏特异性LRP130转基因模型进行平行研究。(3)评价LRP130的转录调控和炎症调控。我们假设细胞因子减弱了LRP130的转录，并可能将细胞因子与线粒体缺陷和过量的超氧阴离子联系在一起。我们将使用遗传学研究、记者分析和染色质免疫沉淀来验证这一假说。由于对基本机制的了解不足，NAFLD患者ROS的治疗操作受到阻碍。我们在LRP130上的新发现将推动关于线粒体在NAFLD中作用的新范式。 公共卫生相关性： 肥胖容易引发心脏病、糖尿病和脂肪肝。肝脏脂肪积聚可能会加速心脏病和糖尿病的发展；因此，改变肝脏脂肪可能对治疗有益。这项提议将研究一种名为LRP130的基因在脂肪肝疾病中的作用，并可能为治疗糖尿病和心脏病提供新的方法。

DESCRIPTION (provided by applicant): Non-alcoholic fatty liver disease (NAFLD) is the leading cause of liver disease in the United States. It spans a clinical spectrum from fatty liver to superimposed inflammation called NASH (non-alcoholic steatohepatitis). NASH predisposes to irreversible cirrhosis and hepatocellular carcinoma, which highlights the need to identify underlying mechanisms. In NAFLD, defective mitochondria liberate excess reactive oxygen species (ROS). Mitochondrial ROS is of interest, because it is implicated in insulin resistance and inflammation, two key features of NAFLD. The mechanism for mitochondrial dysfunction is unknown; hence, understanding its mechanistic basis may mitigate NAFLD. Our preliminary data indicate that LRP130 is an important regulator of mitochondrial function and ROS. In NAFLD, we observed that LRP130 is attenuated in a disease specific manner. Notably, depletion of LRP130 in mouse liver induced insulin resistance and inflammation. Mechanistically, LRP130 regulates the entire mitochondrial genome. Notably, LRP130 profoundly influences respiratory chain formation, respiration and superoxide formation. We hypothesize that LRP130 is a molecular link between defective mitochondria in liver and progression of NAFLD. We propose three Aims to query our hypothesis: (1) Evaluate the role of LRP130 in mitochondrial function and superoxide formation. The impact of LRP130 on mitochondrial bioenergetics will be evaluated using loss- and gain-of-function models in cells and mice. We will evaluate respiratory chain supercomplexes using blue native gel electrophoresis. Mitochondrial function will be measured by oxygen consumption, complex activity, membrane potential and superoxide measurements. (2) Evaluate the role of LRP130 in non-alcoholic fatty liver disease. Fatty liver will be induced by challenging mice with a high fat diet. Mice deficient for LRP130 in liver will be evaluated for insulin sensitivity and inflammation using a complement of assays: hyperinsulinemic-euglycemic clamp, immunodetection of insulin signaling, histological evaluation of inflammation and cytokine profiling. Parallel studies will be conducted with a liver specific LRP130 transgenic model. (3) Evaluate transcriptional and inflammatory control of LRP130. We hypothesize that cytokines attenuate transcription of LRP130, and may link cytokines to defective mitochondria and excess superoxide. We will use genetic studies, reporter assays and chromatin immunoprecipitation to test this hypothesis. Therapeutic manipulation of ROS in NAFLD is impeded by an insufficient understanding of basic mechanisms. Our novel findings on LRP130 will advance new paradigms on the role of mitochondria in NAFLD. PUBLIC HEALTH RELEVANCE: Obesity predisposes to heart disease, diabetes and fatty liver disease. Accumulation of fat in the liver may accelerate the development of heart disease and diabetes; hence, altering liver fat may be of therapeutic benefit. This proposal will investigate the role of a gene called LRP130 in fatty liver disease, and may provide new ways to treat diabetes and heart disease.