Gluconeogenesis and Glycogenolysis - Role and Regulation

描述（由申请人提供）：本申请的目的是更好地了解正常和胰岛素抵抗状态下体内葡萄糖生成（糖异生和糖原溶解）的激素和神经调节。具体目的是了解1)脑胰岛素信号在控制肝脏葡萄糖产生中的生理相关性，2)身体通过调节激素分泌和作用来防御低血糖的机制，以及3)糖异生和糖原溶解在胰岛素抵抗状态下决定肝脏葡萄糖产生的相互作用，以期指导治疗干预。研究将在手术准备的禁食有意识的狗中进行，并根据协议要求安装各种采样和输注导管（例如肾上腺切除术，放置在门静脉和肝静脉，椎动脉和颈动脉，第三脑室的导管等）。葡萄糖代谢将通过A-V差（肝脏、肠道、后肢）和示踪剂（3h -葡萄糖）技术进行评估。采用A-V差和同位素（2H2O， 3h -葡萄糖，13c -丙氨酸）法测定糖异生和糖原分解。此外，为了探索控制的分子机制，将采取活组织检查（肝脏，下丘脑，肌肉，脂肪等）来评估各种细胞信号级联，mRNA表达，蛋白质水平和酶活性。激素水平将通过生长抑素或肾上腺切除术和激素替代来控制。神经介质将通过阻滞剂输注或手术去神经控制来控制。底物水平将通过外源性输注或药理学操作来控制。这些研究的结果将增强我们对体内葡萄糖生成控制的理解，从而促进糖尿病和肥胖患者明显代谢问题的解决方案的发展。公共卫生相关性：肝脏产生过多葡萄糖是糖尿病患者高血糖的主要原因，可能由肝脏和中枢胰岛素抵抗引起；这笔拨款将用于研究胰岛素调节肝脏的机制。胰岛素治疗后的低血糖是糖尿病患者严格控制血糖的主要限制；该项目将进一步阐明机体防御低血糖的机制。饮食引起的肥胖与胰岛素抵抗有关，是糖尿病的主要原因；该项目将探索胰岛素抵抗发展的机制，并研究潜在的治疗策略。

DESCRIPTION (provided by applicant): The objective of this application is to better understand the hormonal and neural regulation of glucose production (gluconeogenesis and glycogenolysis) in vivo in the normal and insulin resistant state. The specific aims are to understand 1) the physiologic relevance of brain insulin signaling in the control of hepatic glucose production, 2) the mechanisms by which the body defends itself against hypoglycemia through modulation of hormone secretion and action, and 3) the interplay between gluconeogenesis and glycogenolysis in determining hepatic glucose production in the insulin resistant state with a view to directing therapeutic intervention. Studies will be carried out in fasted conscious dogs prepared surgically and fitted with a variety of sampling and infusion catheters (e.g. adrenalectomy, catheters placed in the portal and hepatic veins, vertebral and carotid arteries, 3rd cerebral ventricle, etc.) as required by the protocol. Glucose metabolism will be assessed using A-V difference (liver, gut, hind limb) and tracer (3H-glucose) techniques. Gluconeogenesis and glycogenolysis will be determined using A-V difference and isotopic (2H2O,3H-glucose, 13C-alanine) methods. In addition, to explore molecular mechanisms of control, biopsies (liver, hypothalamus, muscle, fat, etc) will be taken for assessment of various cellular signaling cascades, mRNA expression, protein levels and enzyme activities. Hormonal levels will be controlled using somatostatin or adrenalectomy and hormone replacement. Neural mediators will be controlled using blocker infusion or surgical denervation. Substrate levels will be controlled by exogenous infusion or pharmacologic manipulation. The results from the proposed studies should enhance our understanding of the control of glucose production in vivo and thereby facilitate the development of solutions to metabolic problems evident in the diabetic and obese patient. PUBLIC HEALTH RELEVANCE: Overproduction of glucose by the liver is a major contributor to hyperglycemia in diabetes and may result from hepatic and central insulin resistance; this grant will address the mechanisms by which insulin regulates the liver. Low blood sugar following insulin treatment is the major limitation to tight control of glycemia in the individual with diabetes; this project will further elucidate the mechanisms by which the body defends itself against hypoglycemia. Diet induced obesity is associated with insulin resistance and is a major cause of diabetes; this project will explore the mechanisms involved in the development of insulin resistance and potential treatment strategies will be investigated.