A novel role of cholesterol and SR-BI in adipocyte biology

胆固醇和 SR-BI 在脂肪细胞生物学中的新作用

• 批准号: 10733720
• 负责人: Chieko Mineo
• 金额: $ 49.36万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-09-01 至 2027-08-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10733720
• 关键词: ATAC-seq; Address; Adipocytes; Adipose tissue; Affinity; Binding; Binding Sites; CRISPR/Cas technology; Cardiovascular Diseases; Caveolae; Cell Size; Cell membrane; Cholesterol; Cholesterol Homeostasis; Chromosome 12; Data; Disease; Distal; Electron Microscopy; Enhancers; Enzymes; Fatty acid glycerol esters; Gene Expression Regulation; Genes; Genetic; Genetic Predisposition to Disease; Genetic Transcription; Goals; Hepatocyte; Hi-C; High Density Lipoprotein Cholesterol; High Density Lipoproteins; High Fat Diet; Homeostasis; Human; Intervention; Investigation; Knowledge; Ligands; Lipids; Lipoproteins; Liver X Receptor; LoxP-flanked allele; Macrophage; Maintenance; Mediating; Medical Research; Membrane Microdomains; Metabolic Diseases; Mus; Mutagenesis; Nonesterified Fatty Acids; Obesity; Phenotype; Play; Process; Regulation; Research Project Grants; Role; SR-BI receptor; Sterols; Structure; Testing; Text; Tissues; Transcriptional Regulation; Triglycerides; United States National Institutes of Health; Up-Regulation; Wild Type Mouse; adipocyte biology; cohort; combat; deep learning algorithm; experimental study; feeding; genome wide association study; high density lipoprotein receptor; in vivo; knock-down; lipid metabolism; mouse model; mutant; novel; obesity development; obesity risk; promoter; steroid hormone; transcription factor; uptake

Project Summary (30 lines of text) Adipocytes play a key role in energy homeostasis, storing energy in the form of triglyceride (TG). In addition to neutral lipids, adipocytes contain abundant free cholesterol derived from circulating HDL cholesterol. There is a strong positive correlation between adipocyte cholesterol content and TG content, suggesting mechanistic linkage between adipocyte cholesterol and TG regulation. However, how adipocyte cholesterol is modulated by HDL cholesterol, and if and how cholesterol homeostasis in adipocytes influences TG accumulation are unknown. Scavenger receptor class B type I (SR-BI, encoded by SCARB1) is a high-affinity HDL receptor that is abundant in adipocytes. We recently discovered that mice selectively deficient in SR-BI in adipocytes (SR- BI∆AD) are protected from high fat diet-induced adiposity, their adipocytes are smaller, and they have decreased white adipose tissue (WAT) HDL cholesterol uptake and cellular cholesterol content. The overall goal of the project is to elucidate how HDL cholesterol and SR-BI influence adipocyte TG content, and to determine if adipocyte SR-BI expression is genetically regulated in humans to potentially impact the risk of obesity. Three Aims will be pursued in novel mouse models and cultured human adipocytes. Aim 1 will determine if HDL cholesterol and SR-BI promote adipocyte TG accumulation through transcriptional regulation of genes that control lipid homeostasis. We have determined that in SR-BI∆AD WAT the expression of liver X receptor β (LXRβ) and its target genes is downregulated and the content of oxysterols, which are LXR ligands, is decreased. Aim 1 will test the hypothesis that via HDL cholesterol uptake, adipocyte SR-BI promotes TG accumulation by providing the substrate for Cyp27a1 which converts cholesterol to oxysterols, leading to upregulation of LXRβ and its target genes. Aim 2 will determine if HDL cholesterol and SR-BI promote adipocyte TG accumulation by supporting adipocyte free fatty acid (FFA) uptake, which occurs in caveolae, which are cholesterol-rich plasma membrane domains. By electron microscopy we have discovered that caveolae content is markedly decreased in SR-BIAD adipocytes. Aim 2 will test the hypothesis that SR-BI-mediated HDL cholesterol uptake promotes FFA uptake and subsequent TG accumulation by supporting caveolae formation and maintenance. Aim 3 will determine how adipocyte SR-BI expression is transcriptionally regulated in humans, and if there is a genetic predisposition to obesity related to adipocyte SR-BI expression. Using a novel deep learning algorithm, we have identified a potential distal enhancer for SCARB1 within a region on Chr 12 harboring SNPs highly associated with obesity. In cultured human adipocytes, CRISPR/Cas9 deletion of the candidate region decreases SR-BI expression. Using further mutagenesis and interrogation of transcription factor binding sites, we will test the hypothesis that there is a remote enhancer of SCARB1 that harbors SNPs that influence the risk of obesity by their impact on adipocyte SR-BI expression. Collectively the proposed studies will reveal fundamental processes by which HDL cholesterol and SR-BI govern adipocyte function and thereby impact the development of obesity.

项目摘要（文本30行） 脂肪细胞在能量稳态中起关键作用，以甘油三酸酯（TG）的形式存储能量。此外 脂肪细胞中性脂质含有源自循环的HDL胆固醇的丰富游离胆固醇。有一个 脂肪细胞胆固醇含量和TG含量之间的强阳性相关性，提示机械 脂肪细胞胆固醇与TG调节之间的联系。但是，如何调节脂肪细胞胆固醇 HDL胆固醇，以及脂肪细胞中的胆固醇稳态如何影响TG积累 未知。清道夫受体B类I类（SR-BI，由Scarb1编码）是一个高亲和力的HDL受体 脂肪细胞丰富。我们最近发现，小鼠在脂肪细胞中选择性缺陷（SR- Bi∆AD）受到保护免受高脂肪饮食引起的脂肪的保护，其脂肪细胞较小，并且已经改善了 白色脂肪组织（WAT）HDL胆固醇摄取和细胞胆固醇含量。总体目标 项目将阐明HDL胆固醇和SR-BI如何影响脂肪细胞TG含量，并确定是否是否 脂肪细胞SR-BI表达在人类中受到遗传调节，以影响肥胖的风险。三 目标将在新颖的小鼠模型和培养的人脂肪细胞中追求。 AIM 1将确定HDL是否 胆固醇和SR-BI通过转录基因的转录调节促进脂肪细胞TG积累 控制脂质稳态。我们已经确定在sr-biΔadWat中肝X受体β（LXRβ）的表达 它的靶基因被下调，氧化酚的含量（是LXR配体）得到了改善。目的 1将检验以下假设：通过HDL胆固醇摄取，脂肪细胞SR-BI促进TG的积累 提供CYP27A1的底物，该CYP27A1将胆固醇转化为氧甲醇，导致LXRβ上调 及其靶基因。 AIM 2将确定HDL胆固醇和SR-BI是否通过 支持脂肪细胞的无脂肪脂肪酸（FFA）摄取，该摄取发生在小窝中，富含胆固醇的血浆 膜域。通过电子显微镜，我们发现小窝含量显着提高 在sr-biad脂肪细胞中。 AIM 2将检验以下假设：SR-BI介导的HDL胆固醇摄取促进 FFA吸收和随后的TG积累，通过支持小窝形成和维护。目标3意志 确定脂肪细胞SR-BI表达如何在人类中转录调节，以及是否存在通用性 与脂肪细胞SR-BI表达有关的肥胖症的易感性。使用一种新颖的深度学习算法，我们有 确定了chr 12的区域内SCARB1的潜在远端增强子，该区域携带SNP高度相关的SNP 肥胖。在培养的人脂肪细胞中，候选区域的CRISPR/CAS9删除sr-bi 表达。使用进一步的诱变和转录因子结合位点的询问，我们将测试 假设有一个远程增强子Scarb1，它具有影响肥胖风险的SNP 它们对脂肪细胞SR-BI表达的影响。拟议的研究集体将揭示基本过程 HDL胆固醇和SR-BI控制脂肪细胞功能，从而影响对象的发展。