Adipose MTP and FIT2 in the regulation of plasma lipids, obesity and atherosclerosis

摘要-项目1：高水平的载脂蛋白(apoB-LPs)是危险因素 治疗心血管疾病。ApoB-LP的产生需要微粒体甘油三酯(TG)转移蛋白(MTP)。 然而，MTP在不产生apoB-LPs的脂肪组织中的作用尚不清楚。脂肪储存诱导 跨膜蛋白2(FIT2)是另一种甘油三酯结合蛋白，参与脂滴(LD)的形成 脂肪组织。虽然MTP在内质网(ER)的管腔中发挥作用，但FIT2帮助萌发 LDS从内质网膜向胞浆扩散。我们推测这两种甘油三酯结合蛋白 执行不同的功能，影响脂肪细胞生物学，肝脏脂肪代谢，以及 动脉硬化。我们发现，脂肪特异性MTP缺陷(A-MTTP−/−)小鼠对饮食具有抵抗力。 诱导性肥胖、肝骨病和动脉粥样硬化，但脂肪FIT2缺乏导致肝骨病 和炎症。这些截然不同的表型迫使我们去问，MTP缺乏是否可以改善 与FIT2缺乏相关的病理。 目的1.1：脂肪MTP在高甘油三酯血症、肝骨病和动脉粥样硬化中的作用。我们 结果表明，脂肪MTP对脂肪甘油三酯脂肪酶(ATGL)有抑制作用。我们将：1)询问脂肪MTP是否也调节 其他脂肪酶超越ATGL；2)与P2和P3一起工作，以阐明高甘油三酯血症的机制和 减少肝脏骨质疏松症；以及3)与C1-C3合作解释为什么A-MTTP−/−的动脉粥样硬化程度较低 老鼠。这些研究将揭示MTP如何促进脂肪甘油三酯的储存和肥胖。我们建议 抑制脂肪特有的MTP功能将减少肥胖和动脉粥样硬化。 目的1.2：MTP和FIT2在脂肪生物学、肝骨病和动脉粥样硬化中的作用。给定 MTP和FIT2在脂肪细胞中的不同作用和作用部位，我们将研究脂肪特异性的作用 MTP和FIT2缺乏对全身代谢、脂肪分解和动脉粥样硬化的影响，并询问MTP是否 在C1-C3的帮助和P2和P3的专业知识的帮助下，缺陷可以改善FIT2相关的病理。 我们的研究将：1)提供有关脂肪MTP和FIT2在脂肪、肝脏和 血管生物学；2)建立新的小鼠模型；3)解释MTP和FIT2在代谢中的作用，TG 水解、脂肪酸分泌和氧化；4)定义脂肪-肝脏串扰如何控制肥胖， 高甘油三酯血症、肝骨质疏松症和动脉粥样硬化。载脂蛋白B-脂蛋白作用机制的研究 生产取决于与P2的合作。然后我们将与P3合作：1)研究血管内分解代谢 脂肪特异性MTP和FIT2缺陷小鼠产生的载脂蛋白B-LP，2)通过以下方式监测载脂蛋白B-LP的摄取 3)阐明脂肪细胞和巨噬细胞的促炎或抗炎反应。 RNA-seq和单细胞RNA-seq的生物信息学分析(通过C1)，LP表征(通过C2)，以及 动脉粥样硬化研究(由C3进行)将对脂肪特异性蛋白如何调节新陈代谢产生新的见解。

ABSTRACT – PROJECT 1: High blood levels of apoB-containing lipoproteins (apoB-Lps) are risk factors for cardiovascular diseases. ApoB-Lp production requires microsomal triglyceride (TG) transfer protein (MTP). However, MTP’s role in adipose tissue, which does not produce apoB-Lps, is unknown. Fat storage-inducing transmembrane protein 2 (FIT2) is another TG-binding protein that is involved in lipid droplet (LD) formation in adipose tissue. While MTP functions in lumen of the endoplasmic reticulum (ER), FIT2 assists in the budding of LDs from the ER membrane towards cytosol. We hypothesize that these two TG binding proteins perform different functions that affect adipocyte biology, hepatic lipid metabolism, and atherosclerosis. We showed that adipose-specific MTP deficient (A-Mttp−/−) mice are resistant to diet- induced obesity, hepatosteatosis and atherosclerosis, but adipose FIT2 deficiency causes hepatosteatosis and inflammation. These contrasting phenotypes compel us to ask if MTP deficiency can ameliorate pathologies associated with FIT2 deficiency. Aim 1.1: Role of adipose MTP in hypertriglyceridemia, hepatosteatosis, and atherosclerosis. We showed that adipose MTP inhibits adipose TG lipase (ATGL). We will: 1) ask if adipose MTP also modulates other lipases beyond ATGL; 2) work with P2 and P3 to elucidate mechanisms for hypertriglyceridemia and reduced hepatosteatosis; and 3) collaborate with C1–C3 to explain why atherosclerosis is lower in A-Mttp−/− mice. These studies will uncover how MTP promotes adipose TG storage and obesity. We propose that inhibiting adipose-specific MTP function will reduce obesity and atherosclerosis. Aim 1.2: Role of MTP and FIT2 in adipose biology, hepatosteatosis, and atherosclerosis. Given the distinct roles and sites of action of MTP and FIT2 within adipocytes, we will study the effect of adipose-specific MTP and FIT2 deficiencies on whole-body metabolism, adipose lipolysis, and atherosclerosis, and ask if MTP deficiency ameliorates FIT2-associated pathology with help from C1–C3 and expertise from P2 and P3. Our studies will: 1) provide novel information on the roles of adipose MTP and FIT2 in adipose, liver, and vascular biology; 2) generate novel mouse models; 3) explain roles of MTP and FIT2 in metabolism, TG hydrolysis, and FA secretion and oxidation; and 4) define how adipose–liver crosstalk controls obesity, hypertriglyceridemia, hepatosteatosis, and atherosclerosis. Elucidating the mechanisms of apoB-Lps production depends on collaboration with P2. We will then work with P3 to: 1) study intravascular catabolism of apoB-Lps produced by adipose–specific MTP- and FIT2-deficient mice, 2) monitor apoB-Lp uptake by endothelial cells, and 3) elucidate pro- or anti-inflammatory responses in adipocytes and macrophages. Bioinformatics analyses of RNA-seq and single cell RNA-seq (by C1), Lp characterization (by C2), and atherosclerosis studies (by C3) will yield novel insights into how adipose-specific proteins regulate metabolism.