Adiponectin transport: endothelial modulation of adipokine function

描述（申请人提供）：随着肥胖和肥胖相关疾病的急剧增加，了解脂肪组织的内分泌功能至关重要，因为脂肪因子调节全身代谢和胰岛素敏感性。脂肪因子脂联素与肥胖呈负表达，通过肝脏和骨骼肌等多种组织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。我假设内皮对脂联素存在运输障碍，并可能对脂联素分子进行代谢相关处理。我们的初步体内数据表明，脂联素循环时间和半衰期与大小有关。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屏障功能基因的变化，体外transwell研究表明，内皮细胞的脂联素信号传导增加了脂联素和同等大小的葡聚糖分子的单层通透性。这些数据强烈暗示内皮在积极调节脂联素运输和组织可及性。因此，在Aim 1中，我打算定义血液内皮细胞在脂联素运输中的作用，并确定脂联素通过哪些分子途径进入组织。在Aim 2中，我提出脂联素通过淋巴摄取进入循环，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。初步数据显示间质液和淋巴结内存在脂联素，膳食脂肪对周围淋巴功能有影响。目的1将利用操纵脂联素或其受体的小鼠模型来检查脂联素转运和体外转运系统以及与内皮细胞的分子相互作用。在Aim 2中，类似的体内和体外系统将用于探索淋巴内皮细胞间质转运和脂肪因子的相互作用。这两个目标将使我能够充分定义内皮屏障调节脂联素运输和可及性的机制，并为控制脂肪因子反应提供潜在的基础。

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.