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.

项目概要（30行文字） 脂肪细胞在能量稳态中发挥着关键作用，除了以甘油三酯（TG）的形式储存能量。 中性脂质，脂肪细胞含有丰富的来自循环高密度脂蛋白胆固醇的游离胆固醇。 脂肪细胞胆固醇含量与TG含量之间呈强正相关，提示机制 脂肪细胞胆固醇和 TG 调节之间的联系然而，脂肪细胞胆固醇是如何调节的。 HDL 胆固醇，以及脂肪细胞中的胆固醇稳态是否以及如何影响 TG 积累 B 型清道夫受体 I 型（SR-BI，由 SCARB1 编码）是一种高亲和力 HDL 受体。 我们最近发现小鼠脂肪细胞中选择性缺乏 SR-BI（SR-BI）。 BIΔAD）免受高脂肪饮食引起的肥胖的影响，他们的脂肪细胞更小，并且减少了 白色脂肪组织 (WAT) HDL 胆固醇摄取和细胞胆固醇含量的总体目标。 该项目旨在阐明 HDL 胆固醇和 SR-BI 如何影响脂肪细胞 TG 含量，并确定是否 人类脂肪细胞 SR-BI 表达受到基因调控，可能会影响肥胖风险三。 将在新型小鼠模型和培养的人类脂肪细胞中追求目标 1 将确定 HDL 是否存在。 胆固醇和 SR-BI 通过转录调控基因促进脂肪细胞 TG 积累 我们已确定 SR-BIΔAD WAT 中肝脏 X 受体 β (LXRβ) 的表达。 其靶基因被下调，作为LXR配体的氧甾醇的含量降低。 1 将检验以下假设：通过 HDL 胆固醇摄取，脂肪细胞 SR-BI 通过以下方式促进 TG 积累： 为 Cyp27a1 提供底物，将胆固醇转化为氧固醇，导致 LXRβ 上调 及其目标基因将确定 HDL 胆固醇和 SR-BI 是否通过促进脂肪细胞 TG 积累。 支持脂肪细胞游离脂肪酸 (FFA) 的摄取，这种情况发生在小窝中，小窝是富含胆固醇的血浆 通过电子显微镜，我们发现小凹的含量明显减少。 目标 2 将检验 SR-BI 介导的 HDL 胆固醇摄取促进的假设。 通过支持小窝的形成和维持来吸收 FFA 和随后的 TG 积累将是目标 3。 确定脂肪细胞 SR-BI 表达在人类中如何进行转录调控，以及是否存在遗传因素 与脂肪细胞 SR-BI 表达相关的肥胖倾向使用一种新颖的深度学习算法，我们得到了相关结果。 在 Chr 12 上一个含有高度相关 SNP 的区域内鉴定出 SCARB1 的潜在远端增强子 在培养的人类脂肪细胞中，候选区域的 CRISPR/Cas9 缺失会降低 SR-BI。 通过进一步诱变和询问转录因子结合位点，我们将测试 假设 SCARB1 的远程增强子含有 SNP，可通过以下方式影响肥胖风险： 它们对脂肪细胞 SR-BI 表达的影响将共同揭示基本过程。 HDL 胆固醇和 SR-BI 控制脂肪细胞功能，从而影响肥胖的发展。