Vesicle translocation and the metabolic syndrome

描述(申请人提供)：摘要胰岛素通过动员细胞内GLUT4储存小泡(GSv)刺激肌肉中葡萄糖的摄取，GLUT4储存小泡在细胞表面融合并将GLUT4葡萄糖转运体插入肌膜。GLUT4在基础细胞和胰岛素刺激细胞中的不同靶向决定了胰岛素的反应性。胰岛素抵抗是GSV调节受损的结果，并与代谢综合征和2型糖尿病的发病机制有关。胰岛素信号和囊泡运输的缺陷可能是GSV调节受损的原因之一。信号缺陷已经得到了很好的研究，但交易缺陷还没有被描述出来。最近的数据表明，GLUT4转运缺陷可能是肌肉中胰岛素抵抗的一个重要因素。然而，即使是正常的GSV贩运路径也是模糊的。这项提议建立在最近的工作基础上，这项工作首次从分子角度定义了一组受胰岛素调控的GSV。这些囊泡被TUG保留在细胞内，TUG将GSV连接到未受刺激的细胞中的高尔基体基质。胰岛素引起TRAG裂解释放GSV，并在质膜上插入GLUT4。尽管GSV的运输在多个步骤上受到胰岛素的控制，但数据表明，TRAG途径是调节的主要部位，在饮食诱导的小鼠胰岛素抵抗中受到影响。此外，GSV含有GLUT4以外的蛋白质，尤其是IRAP，它可能介导不同的生理作用来控制血管张力和水分动态平衡。因此，GSV转运受损不仅可能导致胰岛素抵抗(与葡萄糖摄取有关)，还可能导致其他 生理异常。在这里，我们建议测试肌肉中的TRAG通路对血糖动态平衡和其他生理学方面的贡献。利用转基因小鼠，Aim 1将测试肌肉中干扰拖拽作用对葡萄糖摄取和周转、能量消耗和其他代谢终点的影响。Aim 2将研究因高脂饮食导致胰岛素抵抗的小鼠，并阐明导致胰岛素抵抗的运输和/或信号缺陷是否被TUG干扰所绕过。目标3将研究破坏拖船行动如何影响水的动态平衡和血压。预计这些研究将提供基本的新见解，对理解葡萄糖稳态、胰岛素抵抗和代谢综合征具有非常重要的意义。公共卫生意义：2型糖尿病和糖尿病前期是一个巨大的公共健康负担，估计影响到美国40%的成年人。这些代谢异常经常作为包括高血压在内的一系列异常的一部分发生，从而导致相当大的发病率和死亡率。这里提出的研究将调查这些异常是如何发生的，以及这种代谢综合征的不同特征是否有共同的病理生理基础。

DESCRIPTION (provided by applicant): Abstract Insulin stimulates glucose uptake in muscle by mobilizing intracellular GLUT4 storage vesicles (GSVs), which fuse at the cell surface and insert GLUT4 glucose transporters into the sarcolemma. The differential targeting of GLUT4 in basal and insulin-stimulated cells determines insulin responsiveness. Insulin resistance results from impaired GSV regulation, and contributes to the pathogenesis of the metabolic syndrome and type 2 diabetes. Defects in both insulin signaling and vesicle trafficking may contribute to impaired GSV regulation. Signaling defects have been well studied, but trafficking defects are not characterized. Recent data suggest that GLUT4 trafficking defects may be an important contributor to insulin resistance in muscle. However, even normal GSV trafficking pathways are poorly defined. This proposal builds on recent work that, for the first time, defines a pool of insulin-regulated GSVs in molecular terms. These vesicles are retained intracellularly by TUG, which links GSVs to the Golgi matrix in unstimulated cells. Insulin causes TUG cleavage to release GSVs and to insert GLUT4 at the plasma membrane. Although GSV trafficking is controlled by insulin at multiple steps, data suggest that the TUG pathway is a major site of regulation, which is compromised in diet- induced insulin resistance in mice. Moreover, GSVs contain proteins other than GLUT4, notably IRAP, which may mediate distinct physiologic actions to control vascular tone and water homeostasis. Thus, impaired GSV trafficking may result not only in insulin resistance (with respect to glucose uptake) but also contribute to other abnormal physiology. Here, we propose to test the contribution of the TUG pathway in muscle to glucose homeostasis and to other aspects of physiology. Using transgenic mice, Aim 1 will test effects of disrupting TUG action in muscle on glucose uptake and turnover, energy expenditure, and other metabolic endpoints. Aim 2 will study mice rendered insulin-resistant by a high-fat diet, and elucidate whether the trafficking and/or signaling defects that contribute to insulin resistance are bypassed by TUG disruption. Aim 3 will study how disruption of TUG action affects water homeostasis and blood pressure. It is anticipated that, together, these studies will provide fundamental new insights that are highly significant for understanding glucose homeostasis, insulin resistance, and the metabolic syndrome. Public Health Significance: Type 2 diabetes and pre-diabetes are an enormous public health burden, estimated to affect >40% of adults in the United States. These metabolic abnormalities frequently occur as part of a constellation of abnormalities, including high blood pressure, which leads to substantial morbidity and mortality. The research proposed here will investigate how these abnormalities occur, and whether distinct features of this metabolic syndrome may have a shared pathophysiologic basis.