Elucidating ACLP-dependent signaling pathways in the adipose tissue stromal-vascular niche

项目总结/摘要 肥胖是心血管疾病、糖尿病、脂肪肝和某些癌症的重要危险因素。在 响应于热量过量，白色脂肪组织（WAT）贮库通过肥大和增生而扩大。 肥大，即先前存在的白色脂肪细胞的大小增加，与不健康的代谢有关。 状态，炎症升高和胰岛素抵抗。相反，WAT增生，新脂肪的招募 来自位于脂肪组织基质血管（SV）龛中的祖细胞的细胞，与更多的 代谢健康的状态。肥胖还可导致细胞外基质（ECM）的病理性积聚 WAT中的蛋白质，这与代谢紊乱密切相关。调节信号通路 脂肪组织纤维化目前是未知的;然而，激活脂肪组织中祖细胞的调节途径， 脂肪组织SV小生境可能决定促纤维化和脂肪形成细胞命运之间的平衡。因为 纤维化是由分泌的因子控制的，这些因子冲击SV生态位，靶向该隔室，而不是 分化的脂肪细胞本身可能代表了治疗肥胖症的治疗干预的新途径， 代谢并发症我们发现，分泌蛋白主动脉羧肽酶样蛋白（ACLP）， 它在SV细胞中被激活，并抑制脂肪细胞分化，同时刺激促纤维化细胞命运。此外，本发明还提供了一种方法， 我们的初步发现将ACLP信号传导与转化生长因子β和血小板源性生长联系起来， 因子受体途径。我们推测，在SV生态位中ACLP信号通路的激活， 脂肪形成性增生并诱导纤维化，导致WAT功能障碍和代谢疾病。为了验证这一 假设，在目标1中，我们将使用新的ACLP重组蛋白和高分辨率 蛋白质组学/磷酸蛋白质组学在脂肪组织SV祖细胞研究中描绘ACLP信号传导 抑制脂肪形成分化并刺激ECM产生的级联反应。在目标2中，我们将确定 启动机制，导致扩大的促纤维化细胞和ECM生产在WAT使用分离的 血管和WAT器官培养。在目标3中，我们将确定是否在体内消除ACLP信号传导， 脂肪组织SV小生境增强脂肪细胞增生并防止饮食诱导的代谢 疾病我们将有条件地删除ACLP在SV小生境中的小鼠进行高和低脂肪饮食。措施 WAT纤维化、全身代谢和血管重塑将测试是否消除ACLP依赖性 SV小生境中的信号传导防止WAT纤维化并提供代谢益处。预期的结果 这些研究鉴定了控制促纤维化/抗脂肪形成细胞命运转换的信号通路， 这会导致病理性WAT重塑和代谢不健康状态。我们设想钝化ACLP 通过鉴定SV小生境中的可作用信号传导靶点的信号传导将减少病理性ECM积累 作为一种干预措施来抑制肥胖引起的疾病。

PROJECT SUMMARY/ABSTRACT Obesity is a significant risk factor for cardiovascular disease, diabetes, fatty liver disease, and some cancers. In response to caloric excess, white adipose tissue (WAT) depots expand through hypertrophy and hyperplasia. Hypertrophy, the increase in size of preexisting white adipocytes, is associated with an unhealthy metabolic state, elevated inflammation, and insulin resistance. In contrast, WAT hyperplasia, the recruitment of the new fat cells from progenitors that reside in the adipose tissue stromal vascular (SV) niche, is associated with a more metabolically healthy state. Obesity also can induce the pathological accumulation of extracellular matrix (ECM) proteins in WAT, which is strongly associated with metabolic perturbations. The signaling pathways that regulate adipose tissue fibrosis are currently unknown; however, regulatory pathways that activate progenitor cells in the adipose tissue SV niche likely determine the balance between profibrotic and adipogenic cell fates. Because fibrosis is controlled by secreted factors that impinge on the SV niche, targeting this compartment, rather than the differentiated adipocyte itself, may represent a novel avenue for therapeutic intervention to treat obesity and metabolic complications. We discovered that the secreted protein aortic carboxypeptidase-like protein (ACLP) is activated in SV cells and it represses adipocyte differentiation, while stimulating a profibrotic cell fate. In addition, our preliminary findings connect ACLP signaling to the transforming growth factor β and platelet derived growth factor receptor pathways. We hypothesize that activation of ACLP signaling pathways in the SV niche blunts adipogenic hyperplasia and induces fibrosis, contributing to WAT dysfunction and metabolic disease. To test this hypothesis, in Aim 1 we will use novel ACLP recombinant proteins and high resolution proteomics/phosphoproteomics in studies of adipose tissue SV progenitor cells to delineate ACLP signaling cascades that repress adipogenic differentiation and stimulate ECM production. In Aim 2 we will identify the initiating mechanisms that lead to the expansion of profibrotic cells and ECM production in WAT using isolated blood vessels and WAT organ culture. In Aim 3 we will determine whether eliminating ACLP signaling in vivo in the adipose tissue SV niche enhances adipocyte hyperplasia and protects against diet induced metabolic disease. We will conditionally delete ACLP in the SV niche in mice subjected to a high and low fat diets. Measures of WAT fibrosis, whole body metabolism, and vascular remodeling will test whether eliminating ACLP-dependent signaling in the SV niche prevents WAT fibrosis and provides metabolic benefit. The anticipated outcome of these studies is the identification of signaling pathways that control a profibrotic/anti-adipogenic cell fate switch, which drives pathological WAT remodeling and a metabolically unhealthy state. We envision that blunting ACLP signaling by identifying actionable signaling targets in the SV niche will reduce pathological ECM accumulation as an intervention to inhibit obesity-induced diseases.