Role of PTG in Adipocytic Glycogen Metabolism

描述(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，在维持全球能量平衡方面发挥关键作用。然而，控制脂肪细胞脂肪代谢的分子机制尚不完全清楚。特别是，葡萄糖储存作为糖原在调节脂肪代谢中的潜在作用还没有被研究，这主要是由于脂肪组织中糖原的绝对水平很低。然而，我们已经提供了一个新的转基因模型的初步数据，表明小鼠脂肪细胞能够稳定地储存比对照小鼠多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，PTG针对蛋白磷酸酶-1的糖原。我们的中心假设是，脂肪细胞糖原水平是积极建立和防御的，而不是残留的默认机制的结果。进一步，我们将验证这样的假设，即PTG表达的转录调控是脂肪组织中糖原水平的关键决定因素，糖原水平反过来调节脂肪生成和脂解的速率。为了检验这些假设，我们提出了三个具体目标。在目标1中，我们将确定在脂肪形成过程中诱导PTG表达的特定启动子元件和转录因子，并介导成熟脂肪细胞PTG水平的激素调节。在目标2中，我们将建立并鉴定一个可诱导的、脂肪组织特异性的PTG基因敲除小鼠系，以确定干扰脂肪细胞糖原储存对脂肪代谢和细胞功能的影响。最后，在目标3中，我们将全面研究糖原代谢的双向调节对全球能源利用的代谢影响。我们将利用一套集成的方法，包括体外分析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。总而言之，这些实验确定了PTG在控制脂肪细胞糖原储存中的作用，并将研究糖原和脂肪组织之间未被充分认识但潜在的基础代谢联系。公共卫生相关性：肥胖和由此产生的代谢并发症，如 在这个国家，2型糖尿病正在以惊人的速度增长。我们将验证葡萄糖和脂肪储存协同工作来调节脂肪细胞能量代谢的假设。我们还将在体外和体内确定改变脂肪细胞中糖原储存对其功能的影响。

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.