Investigating folliculin as a regulator of VLDL-TG secretion in non-alcoholic fatty liver disease and steatohepatitis

研究卵泡素作为非酒精性脂肪肝和脂肪性肝炎中 VLDL-TG 分​​泌的调节剂

• 批准号: 10679361
• 负责人: Chelsea Thorsheim
• 金额: $ 4.77万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2026-02-28
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10679361
• 关键词: Affect; American; Biological Assay; Blood Circulation; Cirrhosis; Compensation; Data; Development; Diet; Disease; Enzymes; FDA approved; FRAP1 gene; Fatty acid glycerol esters; Feedback; Fibrosis; Folliculin; Genes; Genetic Transcription; Hepatic; Histology; Human; Human Genetics; Immunohistochemistry; Infection; Inflammation; Intervention; Investigation; Knock-out; Knockout Mice; Lead; Lecithin; Left; Lipids; Liver; Measures; Mediating; Messenger RNA; Metabolic; Mus; Non-Insulin-Dependent Diabetes Mellitus; Nuclear; Obesity; Organ; Pathogenesis; Pathway interactions; Patients; Peripheral; Persons; Pharmacotherapy; Phosphorylcholine; Predisposition; Primary carcinoma of the liver cells; Process; Proteins; Public Health; Regulation; Research; Risk; Risk Factors; Role; Signal Transduction; Steatohepatitis; Testing; Therapeutic; Tissues; Transcriptional Activation; Triglycerides; Up-Regulation; Very low density lipoprotein; Wild Type Mouse; Work; career; defined contribution; detection of nutrient; fatty acid oxidation; feeding; genetic variant; human disease; improved; insight; lipid biosynthesis; liver metabolism; mouse model; non-alcoholic fatty liver; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; overexpression; particle; prevent; therapeutic target; transcription factor; uptake; very low density lipoprotein triglyceride

Abstract Non-alcoholic fatty liver disease (NAFLD) is a rapidly emerging public health risk. Approximately 35% of Americans have NAFLD, and if left untreated, NAFLD can progress to non-alcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Although obesity and Type II diabetes have emerged as risk factors, disease pathogenesis is poorly understood. Accordingly, there are no FDA-approved pharmacotherapies currently available for patients with NAFLD/NASH. An ideal therapeutic would target multiple hepatic lipid homeostatic processes, including de novo lipogenesis (DNL), fatty acid oxidation (FAO), and very-low-density lipoprotein (VLDL)-triglyceride (TG) secretion, as attempts to modulate a single lipid homeostatic process have often led to undesirable compensation from the remaining pathways. Our lab has identified the protein folliculin (FLCN) as a potential therapeutic target. Mice with hepatic deletion of FLCN are robustly protected against steatosis when challenged with NAFLD-inducing diets via an FLCN-mTORC1-TFE3 signaling axis. TFE3 suppresses DNL and induces genes involved in FAO to decrease hepatic TG content in FLCN-null livers. Given that VLDL-TG secretion is heavily regulated by TG availability, we expected to see a compensatory decrease in VLDL-TG secretion rate in FLCN-null mice. Strikingly, however, we saw marked upregulation of VLDL-TG secretion in FLCN deficient mice, which makes FLCN even more appealing as a therapeutic target. I hypothesize that upregulated VLDL-TG secretion is critical to the robust protection against steatosis afforded by liver deletion of FLCN, and that activated TFE3 is necessary and sufficient for VLDL-TG secretion. To test this, I will generate FLCN knockout (KO), TFE3 KO, and FLCN/TFE3 double knockout (DKO) mice and assess VLDL-TG secretion rates. I will overexpress constitutively active TFE3 in wild-type mice to test if TFE3 is sufficient for VLDL-TG secretion. My preliminary data further lead me to hypothesize that the upregulated VLDL-TG secretion in FLCN- null livers is mediated by TFE3-dependent transcriptional activation of CTP:phosphocholine cytidylyltransferase alpha (CCTa). CCTa is the rate-limiting enzyme in the synthesis of phosphatidylcholine, a critical necessary component for VLDL-TG secretion. My preliminary data show increased CCTa mRNA and protein levels in FLCN knockout mice. I will generate FLCN KO, CCTa KO, FLCN/CCTa DKO mice. I will assess their susceptibility to NAFLD/NASH and perform VLDL-TG secretion assays. Completion of this work would provide insight into the regulation of hepatic lipid homeostatic processes affected in NAFLD/NASH, as well as demonstrate FLCN to be a promising therapeutic target for treatment.

摘要 非酒精性脂肪性肝病（NAFLD）是一种迅速出现的公共卫生风险。约35%的 美国人患有NAFLD，如果不进行治疗，NAFLD可能进展为非酒精性脂肪性肝炎（NASH）， 肝硬化和肝细胞癌虽然肥胖和II型糖尿病已经成为危险因素， 疾病的发病机制知之甚少。因此，没有FDA批准的药物治疗 目前可用于NAFLD/NASH患者。理想的治疗方法是靶向多种肝脏脂质 稳态过程，包括从头脂肪生成（DNL），脂肪酸氧化（FAO）和极低密度 脂蛋白（VLDL）-甘油三酯（TG）分泌，因为试图调节单一的脂质稳态过程， 通常导致来自剩余路径的不期望的补偿。我们实验室已经鉴定出蛋白质毛囊素 （FLCN）作为潜在的治疗靶点。FLCN肝脏缺失的小鼠对以下疾病具有稳健的保护作用： 通过FLCN-mT 0 RC 1-TFE 3信号传导轴用NAFLD诱导饮食激发时的脂肪变性。TFE3 抑制DNL并诱导FAO相关基因降低FLCN缺失肝脏中的肝脏TG含量。给定 VLDL-TG分泌受TG可用性的严重调节，我们预期VLDL-TG分泌的代偿性降低， FLCN缺失小鼠中的VLDL-TG分泌速率。然而，引人注目的是，我们看到VLDL-TG显著上调， 这使得FLCN作为治疗靶点更有吸引力。我假设 上调的VLDL-TG分泌对肝脏缺失提供的抗脂肪变性的强大保护至关重要 的FLCN，并激活TFE 3是必要的和足够的VLDL-TG分泌。为了测试这一点，我将生成 FLCN敲除（KO）、TFE 3 KO和FLCN/TFE 3双敲除（DKO）小鼠，并评估VLDL-TG分泌 rates.我将在野生型小鼠中过表达组成型活性TFE 3，以测试TFE 3是否足以用于VLDL-TG 分泌物。我的初步数据进一步使我假设FLCN中VLDL-TG分泌上调， 空肝由TFE 3依赖的CTP：磷酸胆碱胞苷酰转移酶的转录激活介导 α（CCT a）。CCTa是磷脂酰胆碱合成中的限速酶， VLDL-TG分泌的组分。我的初步数据显示，在FLCN中， 敲除小鼠我将产生FLCN KO、CCT a KO、FLCN/CCT a DKO小鼠。我会评估他们对 NAFLD/NASH并进行VLDL-TG分泌测定。这项工作的完成将有助于深入了解 在NAFLD/NASH中影响肝脏脂质稳态过程的调节，以及证明FLCN是 一个有希望的治疗靶点。