Adiponectin transport: endothelial modulation of adipokine function

描述（由申请人提供）：随着肥胖和肥胖相关疾病的惊人增长，了解脂肪组织的内分泌功能是至关重要的，因为脂肪因子调节全身代谢和胰岛素敏感性。脂肪因子脂联素在肥胖症中表达增加，通过在肝脏和骨骼肌等多种组织中的信号传导具有积极的代谢作用。我们的实验室已经证明了不同大小的脂联素复合物（大小从90到1080kDa）对胰岛素敏感性的不同功效。我推测内皮细胞对脂联素有一个转运屏障，并可能对脂联素进行代谢相关性处理。我们的初步体内数据表明，脂联素的循环时间和半衰期是大小依赖性的。我们测量的脂联素分子大小表明，通过内皮的运输限制是致病的。此外，遗传分析显示内皮细胞中屏障功能基因的变化，体外transwell研究表明，内皮细胞上的脂联素信号增加了脂联素和相当大小的葡聚糖分子的单层渗透性。这些数据强烈暗示了内皮在积极调节脂联素转运和组织可及性。因此，在目标1中，我打算确定脂联素转运中血管内皮细胞的作用，并确定脂联素通过哪些分子途径进入组织。在目标2中，我提出脂联素通过淋巴吸收进入循环，并提出旨在证明这一途径的必要性的实验，确定其调节剂，并证明其在肥胖中的作用。初步数据显示脂联素在间质液和淋巴结内，以及膳食脂肪对外周淋巴功能的影响。目的1将利用脂联素及其受体的小鼠模型研究脂联素的转运和体外转运系统以及脂联素与内皮细胞的分子相互作用。对于目标2，将使用类似的体内和体外系统来探索间质转运和脂肪因子与淋巴管内皮细胞的相互作用。这两个目标将使我能够充分确定内皮屏障调节脂联素转运和可及性的机制，并为控制脂肪因子反应提供潜在的基础。 公共卫生相关性：脂联素在脂肪组织分泌因子中是独特的，因为它对全身代谢和胰岛素敏感性表现出积极的影响。随着我国肥胖及肥胖相关疾病的日益增多，了解脂联素的转运及其分子功能，以最大限度地发挥其作用是非常必要的。在这里，我们提出内皮细胞在调节脂联素转运和进入组织中起着重要作用，并试图确定这些机制。

DESCRIPTION (provided by applicant): With the alarming rise of obesity and obesity related diseases, understanding the endocrine functions of adipose tissue is crucial because adipokines regulate systemic metabolism and insulin sensitivity. Inversely expressed with obesity, the adipokine adiponectin has positive metabolic effects via signaling in various tissues such as liver and skeletal muscle. Our laboratory has demonstrated differential efficacy of various sized adiponectin complexes, with sizes from 90 to 1080kDa, on insulin sensitivity. I hypothesize that the endothelium presents a transport barrier to adiponectin and may process the molecule for metabolic relevance. Our preliminary in vivo data demonstrate that adiponectin circulation time and half-life are size dependent. Our measured molecular sizes of adiponectin indicate transport limitations across the endothelium as being causative. Additionally, genetic analyses display changes in barrier function genes in endothelial cells and in vitro transwell studies demonstrate that adiponectin signaling on endothelial cells increases monolayer permeabilty to adiponectin and comparably-sized dextran molecules. These data strongly implicate the endothelium in actively modulating adiponectin transport and tissue accessibility. Therefore, in Aim 1, I intend to define the role of blood endothelial cells in adiponectin transport and determine by which molecular pathways adiponectin is made tissue accessible. In Aim 2, I propose that adiponectin enters circulation via lymphatic uptake and present experiments designed to demonstrate the necessity of this pathway, determine its modulators, and demonstrate its role in obesity. Preliminary data show adiponectin in interstitial fluid and within lymph nodes and the effect of dietary fat on peripheral lymphatic function. Aim 1 will utilize mouse models manipulating adiponectin or its receptors to examine adiponectin transport and in vitro systems of transport and molecular interactions with endothelial cells. For Aim 2, similar in vivo and in vitro systems will be used to explore interstitial transport and adipokine interaction with lymphatic endothelial cells. These two aims will allow me to fully define the mechanisms by which endothelial barriers modulate adiponectin transport and accessibility, and provide a potential basis for controling adipokine responses. PUBLIC HEALTH RELEVANCE: Adiponectin is unique among adipose tissue secretory factors in that it exhibits positive effects on systemic metabolism and insulin sensitivity. With the rise of obesity and obesity related diseases in our country, it is essential to understand adiponectin transport and molecular functions to maximize its benefits. Here, we propose that the endothelium plays an important role in modulating adiponectin transport and access to tissue and seek to determine these mechanisms.