Adipose Tissue Angiogenesis and Metabolic Disease

描述（由申请人提供）：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。脂肪组织具有重要的生理作用，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中脂肪异位沉积，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成年人中形成功能性脂肪组织所必需的毛细血管网的生长协调尚不清楚。使用一种新的方法来评估脂肪组织毛细血管的形成，我们发现，在人类的胰岛素水平与增强脂肪组织血管生成正相关。此外，胰岛素直接刺激来自小鼠皮下脂肪垫的外植体的毛细血管生长，其方式与高脂饮食（HFD）喂养强烈协同。这些数据支持脂肪组织血管生成和脂肪生成协调以响应过量热量摄入而扩大脂肪组织的假设。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。具体目标1。明确高脂饮食刺激脂肪组织毛细血管芽形成的机制。我们将a）确定HFD喂养是否改变潜在内皮细胞前体的数量，以及增加内皮细胞增殖，B）确定HFD是否诱导造血源性前体募集到脂肪组织中，以及c）确定脂肪组织巨噬细胞在介导HFD中观察到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。具体目标2。明确胰岛素刺激毛细血管芽形成的机制。高分辨率显微镜技术将用于鉴定a）响应胰岛素信号传导和B）响应胰岛素增殖的细胞。胰岛素信号通路的探针以及BrDU示踪将用于确定组织中内皮细胞、脂肪组织来源的干细胞或推定的内皮祖细胞的反应性。初步数据表明，胰岛素刺激脂肪细胞产生促血管生成因子。我们提出的策略，通过蛋白质组学技术来确定这些因素。具体目标3。明确HFD增强胰岛素刺激毛细血管芽形成的机制。我们已经确定了短期HFD上调的生长因子和信号通路，它们可能介导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该过程的影响。此外，我们将进行一个公正的搜索从脂肪组织分泌因子HFD喂养的动物，可以提高胰岛素的作用，使用共培养和生化方法来识别这些因素。! 公共卫生相关性：我们将研究血管如何在脂肪组织中形成，这一过程称为“血管生成”。“这个过程是脂肪组织扩张和充分储存多余热量所必需的。这些研究将帮助我们了解脂肪组织如何扩张，以及为什么脂肪组织分布在不同个体的不同区域（腹部或四肢）。它还将帮助我们了解一些但不是所有超重个体患心脏病和糖尿病的潜在机制。

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. ! PUBLIC HEALTH RELEVANCE: We will be studying how blood vessels form in adipose tissue, a process known as "angiogenesis." This process is required for adipose tissue to expand and adequately store excess calories. These studies will help us understand how adipose tissue expands and why adipose tissue is distributed into different regions (abdomen or limbs) in different individuals. It will also help us understand the potential mechanisms by which some but not all overweight individuals develop heart disease and diabetes.