Defining mechanisms for lipid transport across capillary endothelial cells

定义脂质跨毛细血管内皮细胞转运的机制

• 批准号: 8962344
• 负责人: Stephen G. Young
• 金额: $ 38.5万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-02 至 2019-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8962344
• 关键词: Address; Adipose tissue; Affect; Area; Atherosclerosis; Binding; Binding Sites; Birds; Blood Circulation; Blood capillaries; CD36 gene; Capillary Endothelial Cell; Cardiomyopathies; Cell membrane; Cells; Chickens; Cloning; Complementary DNA; Complex; Coronary Arteriosclerosis; Coronary heart disease; Cytosol; Defect; Diffuse; Diffusion; Electrons; Endothelial Cells; Equipment; Evolution; Fatty Acids; Fishes; Genetic; Genetic Polymorphism; Health; Heparan Sulfate Proteoglycan; Human Resources; Hyperlipidemia; Hypertriglyceridemia; Image; Investigation; Knockout Mice; Laboratories; Left; Lipids; Lipolysis; Lipoproteins; Mammals; Mediating; Metabolism; Methods; Molecular; Movement; Mus; Muscle Cells; Mutation; Nutrient; Organ; Organism; Plasma; Process; Proteins; Reagent; Regulation; Research Personnel; Resolution; Risk; Role; Site; Skeletal Muscle; Testing; Time; Tissues; Triglyceride Metabolism; Triglycerides; Uncertainty; Vertebrates; Vesicle; Zebrafish; capillary; cell type; design; disorder risk; imaging modality; improved; in vivo; insight; interest; interstitial; lipid transport; lipoprotein lipase; mouse model; particle; trafficking

 DESCRIPTION (provided by applicant): Title of Project: "Defining mechanisms for lipid transport across capillary endothelial cells" Our objective is to understand how lipids from triglyceride-rich lipoproteins (TRLs) move across capillary endothelial cells towards parenchymal cells. Our interest in this topic-the least understood area within plasma triglyceride metabolism-arose from our efforts to understand molecular mechanisms for the intravascular processing of TRLs. During the past few years, we showed that GPIHBP1, a GPI-anchored protein of capillary endothelial cells, is solely responsible for shuttling lipoprotein lipase (LPL) from the interstitial spaces to its site of action in the capillary lumen. More recenty, we showed that the LPL-GPIHBP1 complex is critical for the margination of TRLs along capillaries (so that the LPL-mediated processing of TRLs can proceed). The movement of lipid nutrients across capillaries to parenchymal cells is crucial for delivering fuel to vital organs an lipids for storage in adipose tissue. Unfortunately, there are few insights into this process. No one understands: (1) whether the fatty acid products of lipolysis simply diffuse across endothelial cells; (2) whether lipids move across endothelial in the very same vesicles that shuttle GPIHBP1 and LPL; (3) whether intact TRLs move across endothelial cells to the subendothelial spaces; and (4) whether binding of fatty acids by CD36 on endothelial cells is required for lipid transport across capillaries. Also, no one understands how lipids move across capillaries in other vertebrates (e.g., birds, fish). In those organisms, GPIHBP1 is absent and LPL appears to be located largely, if not exclusively, in the extravascular spaces (i.e., it is not associated with capillaries). In other vertebrates, we suspect that the TRLs might be transported across capillaries to the subendothelial spaces-to where the LPL is located. An improved understanding of TRL metabolism in other vertebrates will likely yield insights into accessory mechanisms for TRL processing in mammals. One of the main reasons for the slow progress in understanding lipid transport across capillaries is that there has been no way to visualize lipid transport. "Seeing" how lipids move across capillaries is crucial for deciphering molecular mechanisms and designing testable hypotheses. Fortunately, we have overcome the "imaging roadblock." During the past two years, we have used NanoSIMS and backscattered electron (BSE) imaging to create high-resolution images of TRLs as they marginate along capillaries and as the TRL lipids move across endothelial cells to parenchymal cells. These studies have demonstrated that some TRL lipids move across endothelial cells in vesicles, but additional high-resolution imaging studies are required to determine if diffusion of fatty acids along plasma membranes-or transport of lipids across the cytosol-is involved. The same methods can be used to define the role of specific proteins (e.g., CD36) in lipid transport across endothelial cels. For the next five years, we will use NanoSIMS and BSE imaging to define the cellular and molecular mechanisms for lipid transport across capillaries. We will also define the in vivo functional relevance of CD36 for the transport of TRL-derived lipids across capillary endothelial cells.

 描述（由适用提供）：项目的标题：“定义跨毛细管内皮细胞脂质转运的机制”我们的目标是了解如何在毛细血管内皮细胞上移动富含甘油三酸酯的脂蛋白（TRL）的脂质如何向副乳腺细胞移动。我们对这个主题的兴趣 - 血浆甘油三酸酯代谢 - 动rose中最少的领域，我们从我们的努力中了解了TRL的分子机制。在过去的几年中，我们表明GPIHBP1是毛细血管内皮细胞的GPI锚定蛋白，完全负责将脂蛋白脂肪酶（LPL）从间质空间穿上毛细血管腔内的作用部位。最近，我们表明LPL-GPIHBP1复合物对于沿毛细管的TRL边缘至关重要（因此可以进行LPL介导的TRL处理）。脂质营养物质跨毛细血管向副细胞的运动对于向重要器官提供脂质以存储脂肪组织至关重要。不幸的是，对此过程几乎没有见解。没有人理解：（1）脂解的脂肪酸产物是否只是在内皮细胞中弥漫； （2）脂质是否在穿梭GPIHBP1和LPL的相同蔬菜中遍布内皮； （3）完整的TRL是否在内皮细胞上移动到下皮空间； （4）CD36是否需要在毛细血管上脂质转运对内皮细胞上的脂肪酸结合。同样，没有人知道脂质如何在其他脊椎动物的毛细血管上移动（例如鸟类，鱼）。在这些生物体中，GPIHBP1不存在，LPL似乎在很大程度上（即使不是仅限于）在血管外空间中（即，它不是 与毛细血管相关）。在其他脊椎动物中，我们怀疑TRL可能会跨毛细血管运输到LPL所在的地下上皮空间。对其他脊椎动物中TRL代谢的增强理解可能会产生对哺乳动物中TRL加工的辅助机制的见解。理解跨毛细血管脂质运输的进展缓慢的主要原因之一是没有办法可视化脂质传输。 “看到”脂质如何在毛细血管上移动对于解密分子机制和设计可检验的假设至关重要。幸运的是，我们已经克服了“成像障碍”。在过去的两年中，我们使用纳米菌和反向散射电子（BSE）成像来创建TRL沿毛细血管划分的高分辨率图像，并且随着TRL脂质在跨内皮细胞中移动到副细胞。这些研究表明，一些TRL脂质在蔬菜中的内皮细胞上移动，但是需要其他高分辨率成像研究来确定脂肪酸是否沿质膜或脂质在涉及的脂质中的运输是否扩散。可以使用相同的方法来定义特定蛋白质（例如CD36）在跨内皮胶的脂质转运中的作用。在接下来的五年中，我们将使用Nanosims和BSE成像来定义跨毛细血管脂质转运的细胞和分子机制。我们还将定义CD36在TRL衍生脂质跨毛细血管内皮细胞中的运输中的体内功能相关性。