The Nuclear Receptor-Aster Pathway in Enterohepatic Metabolism

肠肝代谢中的核受体-Aster途径

• 批准号: 10437873
• 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/10437873
• 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; gut inflammation; in vivo; inhibitor; 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 脂质是通过激活来控制基因表达的肠球皮轴中重要的内分泌信号 核马受体。肝脂质代谢和肠道脂质代谢是建立系统性的关键因素 哺乳动物中的胆固醇和甘油三酸酯稳态。这些组织中的脂质积累过多与 糖尿病，纳什，癌症和其他疾病。我们的长期目标是通过 脂质激活的核接收器协调细胞和全身性脂质稳态。在电流中 应用，我们专注于LXR和FXR对新型固醇传输途径的调节。我们发现了 在胆固醇运动中起重要作用的哺乳动物蛋白（Aster -A，-b和-c）家族。这 3紫色以组织特异性表达，并由核接收器不同。翠鸟 B是通过固醇激活的LXR调节的靶标，而Aster-C则由胆汁酸激活的FXR调节。 我们假设Asters在肠ep骨轴的脂质稳态中扮演关键角色，包括饮食脂质 抽象，乳糜微粒产生和反向胆固醇转运。我们进一步假设紫色是 LXR和FXR激动剂的药物效应的重要因素。我们将解决这些 具有以下特定目的的假设。特定的目标1将定义FXR调节的Aster-C在中的作用 肝胆固醇运输。我们将结合细胞，生化，成像和体内研究 定义肝细胞中蛋白石依赖性胆固醇转运的途径。我们已经产生了肝 特定的Aster-C敲除小鼠，初步分析表明它们已经改变了肝脂质和血浆脂质 水平。我们将进行代谢分析和体内胆固醇示踪剂研究以询问系统性 胆固醇通量。我们将分析阿特蛋白的损失或过表达如何影响HDL-的运动 胆固醇进入胆汁，用于基线时的全身反向胆固醇运输，并响应FXR 激动剂。具体的目标2将阐明紫色在肠道胆固醇转运中的作用。我们将分析 缺乏Aster-B，Aster-C或两者都可以测试紫ter在饮食胆固醇抽象和 乳糜微粒的产生。初步分析显示，饮食胆固醇的摄取减少并减少 在没有两个紫外线的情况下，肠上皮细胞胆固醇酯含量。我们将进一步测试是否 有助于智瑟胆固醇排泄。最后，我们发现已批准的药物 抑制肠道胆固醇摄取的ezetimibe是Aster-C的选择性配体，我们已经解决了 Aster-C-脱氮酰基复合物的晶体结构。根据这些发现，我们将确定是否 Aster途径有助于Ezetimibe的药物作用。我们的目标的完成将有望 提供有关管理脂质运输的途径的基本洞察力，并可能确定新的机会 干预代谢疾病。