Novel FXR-dependent Molecular Mechanisms in the Regulation of Liver Metabolism

肝脏代谢调节中 FXR 依赖性新分子机制

• 批准号: 9889118
• 负责人: Peter A Edwards
• 金额: $ 53.48万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-03-15 至 2022-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9889118
• 关键词: Adult; Affect; Agonist; Attenuated; Bile Acids; CYP7A1 gene; Clinical; Clinical Treatment; Clinical Trials; Complement; Data; Diet; Dietary Fats; Enzymes; Essential Fatty Acids; Fatty Acids; Future; Gene Expression Profiling; Genes; Genetic Transcription; Health system; Hepatic; Individual; Intestines; Knockout Mice; Label; Linoleic Acids; Lipids; Liver; Liver diseases; Measures; Mediating; Messenger RNA; Metabolic; Metabolic Pathway; Methods; Modeling; Molecular; Monounsaturated Fatty Acids; Mus; Nuclear Receptors; Pathway interactions; Physiological Processes; Play; Polyunsaturated Fatty Acids; Process; Public Health; Publishing; Receptor Activation; Regulation; Repression; Role; Techniques; Testing; Therapeutic; Therapeutic Intervention; Transcription Repressor; Triglycerides; Work; absorption; chronic liver disease; clinical care; design; experimental study; farnesoid X-activated receptor; hepatocyte injury; in vivo; insight; lipid biosynthesis; lipid metabolism; liver metabolism; mRNA Transcript Degradation; mouse model; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; novel; overexpression; particle; prevent; receptor; western diet

PROJECT SUMMARY/ABSTRACT Non-alcoholic fatty liver disease (NAFLD) is now the most prevalent liver disease, and affects almost one third of adults. Progression from early stages such as steatosis to non-alcoholic steatohepatitis (NASH) requires both the accumulation of triglyceride (TAG) and hepatocyte injury. NASH can be reversed, yet there are limited therapeutic options available. Recent clinical trials have shown that targeting the nuclear receptor FXR holds significant therapeutic promise to treat NASH. FXR activation can be beneficial because FXR is thought to decrease lipogenesis in the liver through an FXR SHP SREBP1C pathway. In the current application, we challenge this paradigm. We have used the potent synthetic and specific FXR agonist GSK2324 to show that FXR activation reduces both liver TAG levels and lipid synthesis in both chow and western diet (WD)-fed wild- type, but not Fxr–/– mice. We then show that GSK2324 treatment reduces TAG levels in the livers of Shp–/– and Srebp1c–/– mice, suggesting these two genes are not essential for the FXR-dependent decrease in hepatic TAG levels, at least in chow-fed mice. We have used lipidomic analysis to show that FXR activation results in selective decreases in specific TAG species. We have also used in vivo labeling techniques to measure newly synthesized lipids, and show that FXR activation selectively alters lipid synthesis. Gene expression analysis supports and explains these specific changes in TAG species, and led us to identify 2 key lipid metabolism mRNAs that are potently reduced in wild-type, Shp–/– and Srebp1c–/– mice but not Fxr–/– mice treated with GSK2324. We have also used a novel non-invasive method to show that FXR activation reduces absorption of dietary lipids. We have now designed two specific aims to determine the molecular mechanisms involved in the reduction of hepatic TAGs following FXR activation. We will use in vivo labeling and lipidomic analysis and various KO mice to determine whether intestinal or hepatic FXR, Shp or Srebp1c are required for FXR-dependent changes in hepatic lipid synthesis and intestinal lipid absorption in a model for NAFLD. We will also determine the molecular mechanism involved in the repression of the two key lipid metabolism genes following FXR activation. Our preliminary data suggest that a new FXR target gene, that we recently identified, promotes the degradation of mRNAs encoding the two key lipid genes. Finally, we will use AAV-dependent expression of these two genes, to determine if overexpression can, either alone or in combination, prevent the decrease in hepatic TAG species following FXR activation. We will also determine whether the FXR-dependent decrease in lipid absorption can be attenuated by increasing the bile acid pool size. Our studies will provide new insights into the mechanisms by which FXR activation alters lipid metabolism. This is likely to be important since FXR agonists are currently being used clinically. Further, our discoveries suggest that targeting specific genes that are downstream of FXR, either individually or in combination, may hold significant promise for future therapeutic intervention to treat NAFLD.

项目摘要/摘要 非酒精性脂肪肝病（NAFLD）现在是最普遍的肝病，几乎三分之一 成人。从早期阶段（例如脂肪变性到非酒精性脂肪性肝炎（NASH））的发展需要 甘油三酸酯（TAG）和肝细胞损伤的积累。纳什可以逆转，但有限 可用的治疗选择。最近的临床试验表明，靶向核接收器FXR保持 对治疗纳什的重要治疗承诺。 FXR激活可能是有益的，因为FXR被认为是 通过FXR SHP SREBP1C途径减少肝脏中的脂肪生成。在当前的应用程序中，我们 挑战这个范式。我们已经使用了潜在的合成和特定的FXR激动剂GSK2324来表明 FXR激活降低了Chow和Western Diet（WD）野生饮食中的肝标签水平和脂质合成 类型，但不是FXR - / - 小鼠。然后，我们表明GSK2324治疗可降低SHP - / - 和 SREBP1C - / - 小鼠，这表明这两个基因对于肝标签的FXR依赖性降低不是必不可少的 水平，至少在食小鼠中。我们已经使用了脂肪组分析来表明FXR激活会导致选择性 减少特定标签规格。我们还使用体内标记技术来测量新合成的 脂质，并表明FXR活化有选择地改变脂质合成。基因表达分析支持并 解释了标签物种的这些特定变化，并使我们确定了2个关键的脂质代谢mRNA 在野生型，shp –/ - 和srebp1c - / - 小鼠中的可能减少，但不是fxr - / - 用GSK2324处理的小鼠。我们有 还使用一种新型的非侵入性方法表明FXR激活减少了饮食脂质的滥用。我们 现在已经设计了两个特定的目的，以确定肝脏还原所涉及的分子机制 FXR激活后的标签。我们将使用体内标记和脂质组分析以及各种KO小鼠 确定肠道依赖FXR依赖性变化需要肠道或肝FXR，SHP或SREBP1C是否需要 NAFLD模型中的脂质合成和肠道脂质浮雕。我们还将确定分子 FXR激活后两个关键脂质代谢基因表达涉及的机制。我们的 初步数据表明，我们最近确定的一个新的FXR靶基因促进了降解 编码两个关键脂质基因的mRNA。最后，我们将使用这两个基因的AAV依赖性表达， 为了确定过表达是否可以单独或结合起来，请防止肝标签物种的减少 遵循FXR激活。我们还将确定FXR依赖性脂质滥用的降低是否可以 通过增加胆汁酸池的大小来减弱。我们的研究将为机制提供新的见解 FXR激活改变了脂质代谢。这可能很重要，因为FXR激动剂目前是 在临床上使用。此外，我们的发现表明，针对FXR下游的特定基因， 单独或结合在一起，可能对将来的治疗干预措施具有巨大的希望 nafld。