The Nuclear Receptor-Aster Pathway in Enterohepatic Metabolism

肠肝代谢中的核受体-Aster途径

• 批准号: 10263359
• 负责人: PETER J TONTONOZ
• 金额: $ 48.98万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-14 至 2025-06-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10263359
• 关键词: Address; Adrenal Cortex; Affect; Agonist; Bile Acids; Bile fluid; Binding; Biochemical; Biological; Cell membrane; Cells; Cholesterol; Cholesterol Esters; Chylomicrons; Complex; Crystallization; Data; Development; Diabetes Mellitus; Dietary Cholesterol; Dietary Fats; Disease; Drug Targeting; Endocrine; Enterocytes; Excretory function; Family; Gastrointestinal Diseases; Gene Expression; Genes; Genetic Transcription; HDL receptor; Hepatic; Hepatocyte; High Density Lipoprotein Cholesterol; Homeostasis; Image; Intervention; Intestines; Knockout Mice; Ligands; Link; Lipids; Liver; Malignant Neoplasms; Mammals; Membrane; Metabolic; Metabolic Diseases; Metabolism; Molecular; Movement; Mus; Nuclear Hormone Receptors; Nuclear Pore Complex; Nuclear Receptors; Pathway interactions; Pharmaceutical Preparations; Pharmacology; Plasma; Play; Production; Proteins; Reagent; Regulation; Reporting; Resolution; Role; SR-BI receptor; Series; Signal Transduction; Small Intestines; Steroid biosynthesis; Sterols; Structure; Testing; Therapeutic Intervention; Tissues; Tracer; Triglycerides; absorption; apical membrane; base; basolateral membrane; cell type; cholesterol absorption; ezetimibe; in vivo; inflammatory disease of the intestine; inhibitor/antagonist; insight; lipid metabolism; lipid transport; nonalcoholic steatohepatitis; novel; overexpression; protein transport; receptor; recruit; response; reverse cholesterol transport; small molecule inhibitor; uptake; vesicle transport

ABSTRACT Lipids are important endocrine signals in the enterohepatic axis that control gene expression by activating nuclear hormone receptors. Hepatic and intestinal lipid metabolism are key factors in establishing systemic cholesterol and triglyceride homeostasis in mammals. Excess lipid accumulation in these tissues is linked to diabetes, NASH, cancer and other diseases. Our long-term objective is to reveal fundamental mechanisms by which lipid-activated nuclear receptors orchestrate cellular and systemic lipid homeostasis. In the current application, we focus on regulation of a novel sterol-transport pathway by LXR and FXR. We have discovered a family of mammalian proteins (Aster-A, -B and -C) that play an important role in cholesterol movement. The 3 Asters are expressed in a tissue-specific manner and are differentially regulated by nuclear receptors. Aster- B is a target for regulation by sterol-activated LXRs, while Aster-C is regulated by the bile acid-activated FXR. We hypothesize the Asters play key roles in lipid homeostasis in the enterohepatic axis, including dietary lipid absorption, chylomicron production and reverse cholesterol transport. We further hypothesize that Asters are important contributors to the pharmacological effects of LXR and FXR agonists. We will address these hypotheses with the following specific aims. Specific Aim 1 will define the role of FXR-regulated Aster-C in hepatic cholesterol transport. We will use a combination of cellular, biochemical, imaging, and in vivo studies to define the pathway for Aster-C-dependent cholesterol transport in hepatocytes. We have generated liver- specific Aster-C knockout mice, and preliminary analysis reveals them to have altered hepatic and plasma lipid levels. We will perform metabolic analyses and in vivo cholesterol tracer studies to interrogate systemic cholesterol flux. We will analyze how loss or overexpression of Aster proteins affects the movement of HDL- cholesterol into bile and for systemic reverse cholesterol transport at baseline and in response to FXR agonists. Specific Aim 2 will elucidate the role of Asters in intestinal cholesterol transport. We will analyze mice lacking Aster-B, Aster-C, or both to test the importance of Asters in dietary cholesterol absorption and chylomicron production. Preliminary analysis has revealed reduced uptake of dietary cholesterol and reduced enterocyte cholesterol ester content in the absence of both Asters. We will further test whether Asters contribute to trans-intestinal cholesterol excretion. Finally, we have discovered that the approved drug ezetimibe, which inhibits intestinal cholesterol uptake, is a selective ligand for Aster-C, and we have solved the crystal structure of the Aster-C–ezetimibe complex. Based on these findings we will determine whether the Aster pathway contributes to the pharmacological effects of ezetimibe. Completion of our aims is expected to provide fundamental insight into pathways governing lipid transport, and may identify new opportunities for intervention in metabolic disease.

抽象的 脂质是肠肝轴中重要的内分泌信号，通过激活 核激素受体肝脏和肠道脂质代谢是建立全身系统的关键因素。 哺乳动物中胆固醇和甘油三酯的稳态与这些组织中过量的脂质积累有关。 我们的长期目标是揭示糖尿病、NASH、癌症和其他疾病的基本机制。 当前，脂质激活核受体协调细胞和全身脂质稳态。 在应用中，我们重点关注 LXR 和 FXR 对新型甾醇转运途径的调节。 哺乳动物蛋白家族（Aster-A、-B 和 -C），在胆固醇运动中发挥重要作用。 3 Aster- 以组织特异性方式表达，并受到核受体的差异调节。 B 是甾醇激活的 LXR 调节的靶标，而 Aster-C 则受胆汁酸激活的 FXR 调节。 我们认为紫菀在肠肝轴的脂质稳态中发挥着关键作用，包括膳食脂质 我们进一步研究了 Aster 的吸收、乳糜微粒的产生和逆转胆固醇的转运。 LXR 和 FXR 激动剂药理作用的重要贡献者我们将解决这些问题。 具有以下具体目标的假设将定义 FXR 调节的 Aster-C 在其中的作用。 我们将结合细胞、生化、成像和体内研究。 为了定义肝细胞中 Aster-C 依赖性胆固醇转运的途径，我们已经生成了肝细胞。 特定的 Aster-C 基因敲除小鼠，初步分析显示它们的肝脏和血浆脂质发生了改变 我们将进行代谢分析和体内胆固醇示踪研究来询问全身情况。 我们将分析 Aster 蛋白的缺失或过度表达如何影响 HDL- 的运动。 胆固醇进入胆汁，并在基线时和响应 FXR 进行全身性反向胆固醇转运 具体目标 2 将阐明 Aster 在肠道胆固醇转运中的作用。 缺乏 Aster-B、Aster-C 或两者均缺乏的小鼠，以测试 Aster 在膳食胆固醇吸收和 初步分析显示，膳食胆固醇的摄取减少并减少。 在没有Asters的情况下，我们将进一步测试Asters是否存在肠细胞胆固醇酯含量。 最后，我们发现了批准的药物。 依折麦布抑制肠道胆固醇摄取，是 Aster-C 的选择性配体，我们已经解决了 根据这些发现，我们将确定 Aster-C-依折麦布复合物的晶体结构。 Aster 途径有助于依折麦布的药理作用，预计将完成我们的目标。 提供对脂质运输途径的基本见解，并可能发现新的机会 干预代谢性疾病。