Regulation of Bile Acid Synthesis by Nuclear receptors

核受体对胆汁酸合成的调节

• 批准号: 7196124
• 负责人: JOHN Y. L. CHIANG
• 金额: $ 30.46万
• 依托单位: NORTHEAST OHIO MEDICAL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-08-01 至 2011-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7196124
• 关键词: Regulation; Bile; Acid; Synthesis; Nuclear

DESCRIPTION (provided by applicant): Bile acids are physiological agents that facilitate absorption, transport and disposal of steroids, nutrients, metabolites and xenobiotics. Bile acids also are signaling molecules that activate nuclear receptors to regulate lipid and glucose homeostasis. Dysregulation of bile acid metabolism causes dyslipidemia, gallstone, liver, and cardiovascular diseases, and diabetes. Bile acids, insulin and cytokines inhibit CYP7A1, the first and rate-limiting enzyme of the bile acid synthesis pathway in the liver. The expression of CYP7A1 is mainly regulated at gene transcriptional level. Bile acid activates the FXR/SHP pathway, and several cell signaling pathways to inhibit CYP7A1 gene transcription. The mechanism of nuclear receptors and signaling pathways regulating CYP7A1 gene transcription remain to be elucidated. Most studies on CYP7A1 gene regulation have been performed in animal models. We have observed marked differences in regulation of the human and rodent CYP7A1 genes. Our central hypothesis is that as an acute phase response to inflammation and liver injury, bile acids and other stimuli activate the PI3K/AKT and MAP kinase signaling pathways, and signal crosstalk regulates nuclear receptors and co-regulators to remodel CYP7A1 and CYP8B1 chromatins. The specific aim 1 will study nuclear receptor and co-regulator modulation of CYP7A1 and CYP8B1 chromatin. The roles of HNF4? and FTP, and their co-regulators Prox1, PGC-1?, histone deacetylase (HDAC) and silencing information regulator (SIRT1) will be studied. HepG2 and primary human hepatocytes will be used for chromatin immunoprecipitation (ChIP), co-IP and mammalian two-hybrid assays to study DNA-protein and protein-protein interaction. Aim 2 will study the crosstalk of bile acid, cytokine, insulin, glucagon and PMA signaling pathways in regulating CYP7A1/CYP8B1 gene transcription. Real time PCR, siRNA, and microarrays will be used to identify genes involved in signaling crosstalk. Am 3 will study hepatocyte growth factor (HGF) regulation of CYP7A1 gene transcription to identify signaling pathway and crosstalk with insulin signaling. The objective of this research is to elucidate the molecular mechanism of nuclear receptor and signaling pathway regulation of bile acid synthesis. This study could contribute to understanding the mechanisms of metabolic diseases caused by dysregulation of bile acid synthesis and develop therapeutic agents to treat dyslipidemia, liver diseases, obesity and type II diabetes.

说明(申请人提供)：胆汁酸是促进类固醇、营养素、代谢物和外源物质的吸收、运输和处置的生理剂。胆汁酸也是信号分子，激活核受体来调节脂质和葡萄糖的动态平衡。胆汁酸代谢失调会导致血脂异常、胆结石、肝脏和心血管疾病以及糖尿病。胆汁酸、胰岛素和细胞因子抑制肝脏胆汁酸合成途径的第一个也是限速酶--细胞色素P7A1。细胞色素P7A1的表达主要在基因转录水平进行调控。胆汁酸激活FXR/SHP通路和几个细胞信号通路来抑制CYP7A1基因的转录。核受体和信号通路调控细胞色素P7A1基因转录的机制尚不清楚。大多数关于CYP7A1基因调控的研究都是在动物模型中进行的。我们观察到人类和啮齿动物CYP7A1基因的调控存在显著差异。我们的中心假设是，作为对炎症和肝损伤的急性时相反应，胆汁酸和其他刺激激活了PI3K/AKT和MAP激酶信号通路，信号串扰调节核受体和辅助调节因子来重塑CYP7A1和CYP8B1染色质。具体目标1将研究细胞色素P7A1和细胞色素P8B1染色质的核受体和协同调控。HNF4的作用是什么？和Fp，以及它们的共同调节因子Prox1、PGC-1？、组蛋白脱乙酰酶(HDAC)和沉默信息调节因子(SIRT1)。HepG2和原代人肝细胞将用于染色质免疫沉淀(ChIP)、共IP和哺乳动物双杂交实验，以研究DNA-蛋白质和蛋白质-蛋白质的相互作用。目的2研究胆汁酸、细胞因子、胰岛素、胰高血糖素和PMA信号通路在调节细胞色素P7A1/8B1基因转录中的相互作用。实时聚合酶链式反应、小干扰RNA和微阵列将被用于识别与信号串扰有关的基因。AM 3将研究肝细胞生长因子(HGF)对细胞色素P7A1基因转录的调控，以确定信号通路及其与胰岛素信号的串扰。本研究的目的是阐明胆汁酸合成的核受体和信号通路调控的分子机制。本研究有助于了解胆汁酸合成失调引起的代谢性疾病的发病机制，并开发治疗血脂异常、肝脏疾病、肥胖和II型糖尿病的药物。