Role of PTG in Adipocytic Glycogen Metabolism

描述（由申请人提供）：脂肪细胞通过调节甘油三酯的储存和动员以及多种脂肪因子的分泌，在维持整体能量稳态中发挥关键作用。然而，控制脂肪细胞脂质代谢的分子机制还不完全清楚。特别是，葡萄糖储存作为糖原在调节脂质代谢中的潜在作用尚未研究，这主要是由于脂肪组织中糖原的绝对水平较低。然而，我们已经提供了一种新的转基因模型的初步数据，证明小鼠脂肪细胞能够稳定储存比对照同窝出生仔多100-400倍的糖原。这些结果是通过过表达内源性脂肪细胞蛋白PTG获得的，该蛋白PTG将蛋白磷酸酶-1靶向糖原。我们的中心假设是，脂肪细胞糖原水平是积极建立和捍卫，而不是从一个残余的默认机制的结果。此外，我们将测试的假设，PTG表达的转录调控是一个关键的决定因素，在脂肪组织中的糖原水平，这反过来又调节脂肪生成和脂解的速率。为了验证这些假设，我们提出了三个具体目标。在目标1中，我们将确定特定的启动子元件和转录因子，诱导PTG在脂肪形成过程中的表达和介导的激素调节成熟脂肪细胞中的PTG水平。在目标2中，我们将产生并表征可诱导的脂肪组织特异性PTG敲除小鼠系，以确定破坏脂肪细胞糖原储存对脂质代谢和细胞功能的影响。最后，在目标3中，我们将充分研究糖原代谢的双向调节对全球能量利用的代谢影响。我们将利用一套完整的方法，包括体外测定原代脂肪细胞的能量储存和动员，以及体内测量能量动员和使用。累积起来，这些实验确定了PTG在控制脂肪细胞糖原储存中的作用，并将研究脂肪组织中糖原和脂质代谢之间未被充分认识但潜在的基本代谢联系。公共卫生相关性：肥胖和由此产生的代谢并发症， 2型糖尿病在这个国家正以惊人的速度增长。我们将检验葡萄糖和脂质储存协同调节脂肪细胞能量代谢的假设。我们还将确定改变脂肪细胞中糖原储存对其体外和体内功能的影响。

DESCRIPTION (provided by applicant): Adipocytes play a crucial role in the maintenance of global energy homeostasis through the regulated storage and mobilization of triglyceride and secretion of a variety of adipokines. However, the molecular mechanisms by which adipocytic lipid metabolism is controlled are not completely understood. In particular, the potential role of glucose storage as glycogen in the modulation of lipid metabolism has not been investigated, largely due to the low absolute levels of glycogen in adipose tissue. However, we have provided preliminary data from a novel transgenic model demonstrating that murine adipocytes are capable of stably storing 100-400-fold more glycogen than control littermates. These results were obtained by overexpression of the endogenous adipocytic protein PTG, which targets protein phosphatase-1 to glycogen. Our central hypothesis is that adipocytic glycogen levels are actively established and defended rather than result from a residual default mechanism. Further, we will test the supposition that the transcriptional regulation of PTG expression is a critical determinant of glycogen levels in adipose tissue, which in turn modulates rates of lipogenesis and lipolysis. To test these hypotheses, we propose three specific Aims. In Aim 1, we will define the specific promoter elements and transcription factors that induce PTG expression during adipogenesis and mediate the hormonal modulation of PTG levels in mature adipocytes. In Aim 2, we will generate and characterize an inducible, adipose-tissue specific PTG knockout mouse line to determine the impact of disrupting adipocytic glycogen storage on lipid metabolism and cell function. Finally, in Aim 3, we will fully investigate the metabolic impact of bi-directional modulation of glycogen metabolism on global energy utilization. We will utilize an integrated set of approaches, including in vitro assays of energy storage and mobilization in primary adipocytes coupled with in vivo measurement of energy mobilization and usage. Cumulatively, these experiments define the role of PTG in the control of adipocytic glycogen storage and will investigate the underappreciated but potentially fundamental metabolic connections between glycogen and lipid metabolism is adipose tissue. PUBLIC HEALTH RELEVANCE: Obesity and the resulting metabolic complications such as type 2 diabetes are increasing at an alarming rate in this country. We will test the hypothesis that glucose and lipid storage work coordinately to regulate energy metabolism in the adipocyte. We will also determine the impact of altering glycogen storage in fat cells on their function in vitro and in vivo.