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

项目摘要/摘要 肥胖是心血管疾病、糖尿病、脂肪肝和某些癌症的重要风险因素。在……里面 对热量过多的反应，白色脂肪组织(WAT)储存库通过肥大和增殖而扩张。 肥大，即先前存在的白色脂肪细胞大小的增加，与不健康的代谢有关。 状态、炎症升高和胰岛素抵抗。相比之下，Wat增生，招募了新的肥胖者 来自脂肪组织基质血管(SV)壁龛的祖细胞与更多的 新陈代谢健康的状态。肥胖还会导致细胞外基质(ECM)的病理性积聚 WAT中的蛋白质，这与新陈代谢紊乱密切相关。调控的信号通路 脂肪组织纤维化目前尚不清楚；然而，激活脂肪组织中的前体细胞的调节通路 脂肪组织SV生态位可能决定促纤维化和成脂细胞命运之间的平衡。因为 纤维化是由影响SV小室的分泌因子控制的，靶向是这个隔室，而不是 分化的脂肪细胞本身可能代表着一种治疗干预肥胖症和 代谢并发症。我们发现，分泌蛋白主动脉羧肽酶样蛋白(ACLP)是 在SV细胞中被激活，它抑制脂肪细胞的分化，同时刺激促纤维化细胞的命运。此外, 我们的初步发现将ACLP信号与转化生长因子β和血小板源生长联系起来 因子受体途径。我们假设在SV小丘钝器中ACLP信号通路被激活 成脂性增生并导致纤维化，导致WAT功能障碍和代谢性疾病。为了测试这一点 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/磷蛋白质组学在脂肪组织SV前体细胞研究中描绘ACLP信号 抑制成脂分化和刺激细胞外基质产生的级联反应。在目标2中，我们将确定 WAT中导致纤维原细胞扩张和细胞外基质产生的启动机制 血管和Wat器官培养。在目标3中，我们将确定在体内消除ACLP信号是否 脂肪组织SV壁龛促进脂肪细胞增殖并防止饮食诱导的代谢 疾病。我们将有条件地删除高脂饮食和低脂饮食小鼠的SV小生境中的ACLP。措施 WAT纤维化、全身代谢和血管重塑的研究将检验是否消除ACLP依赖 SV利基中的信号可预防WAT纤维化，并提供代谢益处。预期的结果 这些研究是确定控制促纤维化/抗脂肪生成细胞命运开关的信号通路， 这会导致病理性的WAT重塑和代谢不健康的状态。我们设想钝化的ACLP 通过识别SV生态位中可操作的信号转导靶点进行信号转导将减少病理性ECM堆积 作为一种干预措施来抑制肥胖引发的疾病。

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.