Nuclear hormone receptor regulation of cholesterol absorption

核激素受体调节胆固醇吸收

基本信息

批准号：
8077874
负责人：
JOYCE J REPA
金额：
$ 30.78万
依托单位：
UT SOUTHWESTERN MEDICAL CENTER
依托单位国家：
美国
项目类别：
财政年份：
2008
资助国家：
美国
起止时间：
2008-08-01 至 2013-05-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8077874
关键词：
ATP-Binding Cassette Transporters Affect Area Back Bile Acid Biosynthesis Pathway Bile Acids Bile fluid Biliary Biological Assay Carrier Proteins Cell Line Cells Chemicals Cholelithiasis Cholesterol Cholesterol Homeostasis Computer Simulation Cycloheximide Data Development Dietary Fats Elements Enterocytes Equilibrium Excretory function Exhibits Factor X Fenofibrate Gene Targeting Genes Genetic Transcription Health Hepatic Hormones Human Individual Differences Intestines Knockout Mice LDL Cholesterol Lipoproteins Ligands Liver Mammals Mediating Messenger RNA Methods Modeling Molecular Molecular Biology Molecular Mechanisms of Action Mus Nuclear Hormone Receptors Nuclear Orphan Receptor Pathway interactions Peroxisome Proliferator-Activated Receptors Pharmaceutical Preparations Physiology Play Production Proteins RXR Regulation Relative (related person)Reporter Repression Role Serum Sterols System Testing Therapeutic Transcriptional Regulation Work absorption cholesterol absorption cholesterol trafficking cholesterol transporters ezetimibe hypercholesterolemia inhibitor/antagonist interest novel promoter receptor response tool transcription factor uptake

项目摘要

DESCRIPTION (provided by applicant): Mammals acquire cholesterol by two pathways: de novo synthesis of cholesterol and cholesterol absorption. The contribution of each of these pathways in humans is roughly equivalent, and in the last several years, with the identification of proteins integral to cholesterol absorption, there is increased interest in identifying ways to regulate intestinal sterol uptake to ultimately reduce serum LDL-cholesterol levels. In previous work, we observed that the retinoid X receptor (RXR) ligand LG268 dramatically reduced cholesterol absorption in mice. Further studies revealed that this activity could be attributed to RXR's role as an obligate heterodimer partner with two nuclear orphan receptors: the liver X receptor (LXR) by regulation of ATP-binding cassette transporters ABCG5/G8; and the farnesoid X receptor (FXR) by regulation of bile acid production. In preliminary work presented here, we establish that LG268 continues to affect cholesterol absorption in a manner independent of LXR and FXR. Therefore, the long-term objective of this proposal is to elucidate the molecular mechanism(s) responsible for RXR-mediated inhibition of cholesterol absorption and identify additional means of regulating this important cholesterol acquisition pathway. Specific Aim 1. Define the molecular mechanism of action of RXR. We will use various nuclear hormone receptor knockout mice, an intestinal explant culture system, and selective synthetic ligands to establish if RXR is acting as a homodimer, an obligate heterodimer partner, or through interaction with another transcription factor (transrepression) to reduce cholesterol absorption. Specific Aim 2. Identify the ultimate intestinal target gene responsible for RXR-mediated inhibition of cholesterol absorption. Of all the genes evaluated thus far, only NPC1L1, a putative cholesterol transporter shows altered expression by RXR. We will use the human Caco2 cell line to interrogate the NPC1L1 promoter by cell reporter assay. Specific Aim 3. Identify the RXR-regulated primary target gene that affects NPC1L1 expression. Preliminary results establish that RXR does not act directly on the NPC1L1 gene, but induces production of an intermediate responsible for NPC1L1 transcriptional regulation. We will use microarray, ChIP-on-Chip, and NPC1L1-promoter ChIP methods to define the transcriptional regulators of NPC1L1. PUBLICH HEALTH RELEVANCE: The studies proposed in this application will reveal novel targets for cholesterol-lowering therapies to control serum LDL-cholesterol levels. Additional mechanisms to reduce the cholesterol transport protein, NPC1L1, particularly in an intestine-specific manner, may result in the development of safer drugs for the treatment of hypercholesterolemia and cholelithiasis.

描述（由申请人提供）：哺乳动物通过两种途径获得胆固醇：从头合成胆固醇和胆固醇吸收。这些途径在人类中的贡献大致相当，在过去的几年中，通过鉴定蛋白质对胆固醇吸收不可或缺的蛋白质，人们对确定调节肠道固醇摄取的方法有更多的兴趣，以最终降低血清LDL-胆固醇水平。在先前的工作中，我们观察到类维生素X受体（RXR）配体LG268大大降低了小鼠的胆固醇吸收。进一步的研究表明，该活性可以归因于RXR作为与两个核孤儿受体的强制性异二聚体伴侣的作用：通过调节ATP结合盒式转运蛋白ABCG5/G8，肝X受体（LXR）的作用；肝脏X受体（LXR）；通过调节胆汁酸的产生，Farnesoid X受体（FXR）。在此处介绍的初步工作中，我们确定LG268继续以独立于LXR和FXR的方式影响胆固醇的吸收。因此，该提案的长期目标是阐明负责RXR介导的胆固醇吸收抑制的分子机制，并确定调节这种重要的胆固醇采集途径的其他方法。特定目的1。定义RXR作用的分子机理。我们将使用各种核激素受体基因敲除小鼠，肠外植培养系统和选择性合成配体来确定RXR是否充当同型二聚体，强制性异二聚体伴侣，或通过与另一个转录因子（transepression）相互作用以减少胆固醇的吸收。具体目标2。确定负责RXR介导的胆固醇吸收抑制的最终肠道靶基因。在到目前为止评估的所有基因中，仅NPC1L1，推定的胆固醇转运蛋白显示出RXR的表达改变。我们将使用人CACO2细胞系通过细胞报告基因测定法询问NPC1L1启动子。具体目标3。确定影响NPC1L1表达的RXR调节的主要靶基因。初步结果表明，RXR不直接作用于NPC1L1基因，而是诱导负责NPC1L1转录调控的中间体产生。我们将使用微阵列，芯片和NPC1L1启动器芯片方法来定义NPC1L1的转录调节剂。 Publich健康相关性：本应用程序中提出的研究将揭示降低胆固醇疗法的新靶标，以控制血清LDL-胆固醇水平。减少胆固醇转运蛋白NPC1L1的其他机制，特别是以肠特异性方式，可能导致开发更安全的药物来治疗高胆固醇血症和胆石症。