Regulation of Bile Acid Synthesis by Nuclear receptors

描述（由申请人提供）：胆汁酸是促进类固醇、营养素、代谢物和外源物质的吸收、运输和处置的生理制剂。胆汁酸也是激活核受体以调节脂质和葡萄糖稳态的信号分子。胆汁酸代谢失调会导致血脂异常、胆结石、肝脏疾病、心血管疾病以及糖尿病。胆汁酸、胰岛素和细胞因子抑制 CYP7A1，CYP7A1 是肝脏中胆汁酸合成途径的第一个限速酶。 CYP7A1的表达主要在基因转录水平上受到调控。胆汁酸激活 FXR/SHP 途径和多种细胞信号传导途径来抑制 CYP7A1 基因转录。核受体和信号通路调节CYP7A1基因转录的机制仍有待阐明。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 基因的调控存在显着差异。我们的中心假设是，作为对炎症和肝损伤的急性期反应，胆汁酸和其他刺激物激活 PI3K/AKT 和 MAP 激酶信号通路，信号串扰调节核受体和协同调节器以重塑 CYP7A1 和 CYP8B1 染色质。具体目标 1 将研究 CYP7A1 和 CYP8B1 染色质的核受体和协同调节器调节。 HNF4的作用？和 FTP 及其共同调节因子 Prox1、PGC-1?、组蛋白脱乙酰酶 (HDAC) 和沉默信息调节因子 (SIRT1) 将被研究。 HepG2 和原代人肝细胞将用于染色质免疫沉淀 (ChIP)、co-IP 和哺乳动物双杂交测定，以研究 DNA-蛋白质和蛋白质-蛋白质相互作用。目标 2 将研究胆汁酸、细胞因子、胰岛素、胰高血糖素和 PMA 信号通路在调节 CYP7A1/CYP8B1 基因转录中的串扰。实时 PCR、siRNA 和微阵列将用于识别参与信号串扰的基因。 Am 3 将研究肝细胞生长因子 (HGF) 对 CYP7A1 基因转录的调节，以确定信号通路以及与胰岛素信号的串扰。本研究的目的是阐明核受体和信号通路调控胆汁酸合成的分子机制。这项研究可能有助于了解胆汁酸合成失调引起的代谢疾病的机制，并开发治疗血脂异常、肝病、肥胖和 II 型糖尿病的治疗药物。

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.