miR-378/378* promotes hepatic lipid accumulation and progression of NAFLD to NASH

描述(申请人提供)：非酒精性脂肪性肝病(NAFLD)是最常见的肝脏疾病，估计在工业化世界的总人口中有20%-30%的患病率。它与许多风险因素有关，包括II型 糖尿病、肝细胞癌、心血管疾病和高脂血症。MicroRNAs(MiRNAs)是一类新的自然产生的非编码小RNA，通过抑制靶基因的表达，在许多代谢疾病中发挥关键作用。现在公认的是，将特定的miRNAs或antimiRs导入疾病细胞和组织可以诱导良好的治疗反应。事实上，miR-122抑制剂已经作为丙型肝炎病毒感染的治疗剂进入了第三阶段临床试验。肝细胞是控制脂肪代谢的主要细胞类型，也是非酒精性脂肪性肝病脂肪堆积的主要部位。为了探讨它们在NAFLD发生发展中的潜在作用，我们最初鉴定了在肝细胞中高水平和特异性表达的miRNAs，并发现其中之一miR-378/378*在高脂饮食(HFD)维持的小鼠肝脏中显著诱导。此外，通过抑制miR-378/378*，我们能够显著防止HFD治疗小鼠的肝脏脂肪堆积和高脂血症。生物信息学和验证研究表明，miR-378/378*直接抑制NASH和血脂异常的两个守门人NRF1(核呼吸因子1)和SORT1(Sortilin 1)，并诱导NASH的启动子TNF？的表达。这些发现使我们假设miR-378/378*通过同时调节NRF1、SORT1和TNF？的表达来促进肝脏脂质堆积和NAFLD向NASH的进展。本项目的目标是确定miR-378/378*与NRF、SORT1和TNF？调节肝脏脂肪堆积和NAFLD向NASH的进展。本研究的长期目标是阐明NAFLD的潜在机制(S)及其向NASH的进展，并开发miRNA抑制剂作为治疗这两种疾病的药物。我们设计了三个具体目标来检验我们的假设。具体地说，我们将(1)建立miR-378/378*影响HFD治疗小鼠肝脂的功能增益研究，并确定它们的抑制是否通过调节NRF1和SORT1来阻止肝脏脂肪堆积；(2)确定miR-378/378*在促进NAFLD向NASH进展中的作用，并阐明这一过程的潜在机制；以及(3)评估miR-378/378*、SORT1、NRF1和TNF？在一组来自NAFLD和NASH谱系患者的肝脏样本中。我们的研究旨在建立miR-378/378*作为调节肝脏脂代谢和NAFLD向NASH进展的新途径。强大的初步数据和合乎逻辑和合理的实验设计相结合，使该项目具有很高的可行性。这些结果将为了解miRNAs的生理作用和机制提供新的见解，以及它们对这两种肝病的潜在治疗应用。

DESCRIPTION (provided by applicant): Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder with a prevalence estimated to be in 20-30% of the general population within the industrialized world. It is associated with a number of risk factors, including, type II diabetes, hepatocellular carcinoma (HCC), cardiovascular disease, and hyperlipidemia. MicroRNAs (miRNAs) are a new class of naturally occurring small non-coding RNAs that are known to play critical roles in a number of metabolic disorders, in part, by inhibiting expression of target genes. It is now well established that the introduction of specific miRNAs, or antimiRs into diseased cells and tissues can induce favorable therapeutic responses. Indeed, miR-122 inhibitor has entered phase III clinical trials as a therapeutic agent for HCV infection. Hepatocytes are the major cell type that controls lipid metabolism and the primary site of lipid accumulation in NAFLD. To address their potential role in the development of NAFLD, we initially identified miRNAs that are highly and specifically expressed in hepatocytes and found that one of them, miR-378/378*, is significantly induced in the livers of mice maintained on a high fat diet (HFD). Further, by inhibiting miR-378/378* we were able to significantly prevent hepatic lipid accumulation and hyperlipidemia in HFD-treated mice. Bioinformatic and validation studies revealed that miR-378/378* directly inhibited NRF1 (nuclear respiratory factor 1) and SORT1 (Sortilin 1), two gatekeepers of NASH and dyslipidemia, and induced expression of TNF?, a promoter of NASH. These findings led us to hypothesize that miR-378/378* promotes hepatic lipid accumulation and the progression of NAFLD to NASH by simultaneously modulating expression of NRF1, SORT1 and TNF?. The objective of this project is to determine the roles of the crosstalk of miR-378/378* with NRF, SORT1 and TNF? in regulating hepatic lipid accumulation and the progression of NAFLD to NASH. The long-term goal of this study is to elucidate the underlying mechanism(s) of NAFLD and its progression to NASH, and develop miRNA inhibitors as therapeutic agents for both disorders. Three Specific Aims are designed to test our hypothesis. Specifically, we will (1) establish gain-of-function studies for miR-378/378* in affecting hepatic lipids in HFD-treated mice, and determine whether their inhibition prevents hepatic lipid accumulation via modulation of NRF1 and SORT1; (2) determine the role of miR-378/378* in promoting progression of NAFLD to NASH, and elucidate the underlying mechanisms of this process; and (3) evaluate the levels of miR-378/378*, SORT1, NRF1 and TNF? in a set of liver samples from patients with a spectrum of NAFLD and NASH. Our studies are designed to establish miR-378/378* as a new pathway for the regulation of hepatic lipid metabolism and the progression of NAFLD to NASH. The combination of strong preliminary data and a logical and rationally based experimental design make this project highly feasible. The results will provide novel insights into the physiological roles and mechanisms of miRNAs, in addition to their potential therapeutic application for both of these hepatic disorders.