Adipose Tissue Angiogenesis and Metabolic Disease

描述(申请人提供)：本项目的目标是了解控制人类脂肪组织发育和功能的机制。脂肪组织发挥着重要的生理作用，包括调节饱腹感、全身能量平衡、长寿和生殖健康。脂肪组织发育异常导致肝脏和肌肉异位脂肪沉积，并伴有胰岛素抵抗和代谢性疾病。脂肪细胞的生长和分化如何与形成成人功能性脂肪组织所需的毛细血管网络的生长相协调尚不清楚。使用一种新的方法来评估脂肪组织的毛细血管形成，我们发现人类的胰岛素水平与增强的脂肪组织血管生成呈正相关。此外，胰岛素直接刺激小鼠外周脂肪垫外植体的毛细血管生长，这种方式与高脂饮食(HFD)喂养有很强的协同作用。这些数据支持这样的假设，即脂肪组织的血管生成和脂肪生成是协调的，以扩大脂肪组织，以响应过多的热量摄入。我们试图揭示高脂饮食和胰岛素协同刺激脂肪组织血管生成的细胞和分子机制。具体目的1.明确高脂饮食刺激脂肪组织毛细血管发芽形成的机制。我们将a)确定HFD喂养是否改变潜在内皮细胞前体的数量，同时增加内皮细胞的增殖；b)确定HFD是否诱导造血祖细胞向脂肪组织募集；以及c)确定脂肪组织巨噬细胞在介导HFD所见的毛细血管生长增加中的作用。后者与我们理解炎症、肥胖、血管生成和胰岛素抵抗之间的关系有关。明确胰岛素刺激毛细血管发芽形成的机制。高分辨率显微镜技术将被用来识别a)对胰岛素信号做出反应，b)对胰岛素做出反应而增殖的细胞。胰岛素信号通路的探针以及BrDU示踪将用于定义组织中内皮细胞、脂肪组织来源的干细胞或假定的内皮祖细胞的反应性。初步数据显示，胰岛素刺激脂肪细胞产生促血管生成因子。我们提出了通过蛋白质组学技术识别这些因子的策略。明确HFD增强胰岛素刺激毛细血管发芽形成的机制。我们已经确定了短期HFD上调的生长因子和信号通路，这可能介导了胰岛素对毛细血管生长的协同作用。我们将直接确定这些因素对毛细血管芽形成的影响以及胰岛素对这一过程的影响。此外，我们将不偏不倚地从高脂饲料喂养的动物的脂肪组织中寻找可以增强胰岛素作用的分泌因子，使用共培养和生化方法来鉴定这些因子。好了！

DESCRIPTION (provided by applicant): The goal of this project is to understand the mechanisms that control the development and function of human adipose tissue. Adipose tissue fulfills critical physiological roles, including the regulation of satiety, whole body energy homeostasis, longevity and reproductive health. Abnormalities of adipose tissue development result in ectopic lipid deposition in liver and muscle, accompanied by insulin resistance and metabolic disease. How the growth and differentiation of adipocytes is coordinated with the growth of the capillary network necessary to form functional adipose tissue in adults is not known. Using a novel method to assess adipose tissue capillary formation we find that insulin levels in humans positively correlate with enhanced adipose tissue angiogenesis. Moreover, insulin directly stimulates capillary outgrowth from explants from mouse epidydimal fat pads, in a manner that is strongly synergized by high-fat diet (HFD) feeding. These data support the hypothesis that adipose tissue angiogenesis and adipogenesis are coordinated to expand adipose tissue in response to excess caloric intake. We seek to uncover the cellular and molecular mechanisms by which adipose tissue angiogenesis is stimulated synergistically by high fat diet and insulin. Specific Aim 1. To define the mechanisms by which high fat diet stimulates adipose tissue capillary sprout formation. We shall a) determine whether HFD feeding alters the number of potential endothelial cell precursors, in conjunction with increasing endothelial cell proliferation, b) define whether HFD induces the recruitment of hematopoietic-derived precursors into adipose tissue, and c) define the role of adipose tissue macrophages in mediating the increased capillary outgrowth seen in HFD. This latter is relevant for our understanding the relationships between inflammation, obesity, angiogenesis and insulin resistance. Specific Aim 2. To define the mechanisms by which insulin stimulates capillary sprout formation. High- resolution microscopy techniques will be used to identify the cells that a) respond to insulin signaling, and b) proliferate in response to insulin. Probes for insulin signaling pathways, as well as BrDU tracing will be used to define the responsiveness of endothelial cells, adipose tissue-derived stem cells, or putative endothelial progenitor cells in the tissue. Preliminary data indicate that insulin stimulates the production of pro-angiogenic factors by adipocytes. We propose strategies to identify these factors through proteomic techniques. Specific Aim 3. To define the mechanism by which HFD potentiates insulin stimulation of capillary sprout formation. We have identified growth factors and signaling pathways that are up-regulated by short term HFD, and that may mediate the synergistic effect of insulin on capillary outgrowth. We will directly determine the effects of these factors on capillary sprout formation and on the effects of insulin on this process. In addition, we will conduct an unbiased search for secreted factors from adipose tissue from HFD-fed animals that could enhance insulin action, using co-culture and biochemical approaches to indentify such factors. !