CARBOHYDRATE AND LIPID METABOLIC PATHWAYS

我们的长期目标是开发和应用新的方法，显著提高我们对生理和病理状态下的碳水化合物和脂肪代谢的理解，特别是糖尿病。这些方法有共同的安全的2H-富集体水与2H20。我们计划实现以下七个相互关联的具体目标。1.定量测定肝糖原含量对肝糖原水解、循环和周转的影响。2.通过标记从2H20开始测量甘油从头形成的速率，并确定：(I)肝和肾脏在甘油产生、脂肪酸再酯化和脂肪分解定量中的作用，以及(Ii)脂肪组织用来再酯化脂肪酸的甘油-3-P的碳源。3.确定2H20标记葡萄糖C_1上H的途径(S)，并确定这种标记如何影响糖异生和糖原分解的计算。4.建立一种基于体水2H-富集度的糖异生定量方法。5.评估转醛醇酶反应在多大程度上影响糖异生和糖原分解的定量6.将这些技术应用于NIDDM高危人群的糖异生测定(I)。(Ii)在NIDDM患者中，以及(Iii)在NIDDM患者中，然后使用二甲双胍治疗。7.将这些技术应用于肥胖患者的糖异生测量。受试者将摄入2H2O(通过葡萄糖中的C5/C2 2H标记比率来测量葡萄糖异生对葡萄糖产生的贡献)，并将注入(6，6-2H2)葡萄糖(以测量葡萄糖周转)。通过将葡萄糖碳结合到六亚甲基四胺中进行检测，葡萄糖碳上的2H-浓缩将扩大六倍。糖异生的贡献可能与~(13)C-核磁共振波谱测定的肝糖原含量有关。我们的研究将确定糖异生在糖尿病高血糖中的作用，(Ii)作为NIDDM发病的一个可能的病因因素，以及(Iii)在二甲双胍的作用机制中。他们将有助于确定上身肥胖受试者患胰岛素抵抗、NlDDM和心血管疾病的倾向是否与糖异生增加有关。此外，糖原到葡萄糖的直接转换可能被证明是糖原含量的重要调节因素。我们的研究将为脂肪组织中的葡萄糖和脂肪代谢如何适应禁食提供新的线索。

Our long-term objective is to develop and apply novel methods that will significantly advance our understanding of carbohydrate and lipid metabolism in physiological and pathological states, in particular diabetes. These methods have in common the safe 2H- enrichment of body water with 2H20. We plan to achieve the following seven interrelated specific aims. 1. To quantitate glycogen hydrolysis, cycling, and turnover as a function of liver glycogen content. 2. To measure the rate of de novo glycerol formation via labeling from 2H20, and to define: (i)the role of liver and kidney in glycerol production, fatty acid reesterification, and lipolysis quantitation., and (ii) the source of carbon of glycerol-3-P used by adipose tissue to reesterify fatty acids. 3. To determine the pathway(s) by which 2H20 labels H on C1 of glucose, and to define how this labeling affects calculations of gluconeogenesis and glycogenolysis. 4. To develop a method for quantitating glyconeogenesis, based on 2H-enrichment of body water. 5. To evaluate to what extent the transaldolase reactions affect quantitations of gluconeogenesis and glycogenolysis 6. To apply these techniques to measurements of gluconeogenesis (i) in subjects who are at high risk for NIDDM. (ii) in NIDDM patients, and (iii) in the NIDDM patients then treated with metformin. 7. To apply these techniques to measurements of gluconeogenesis in obese patients. The subjects will ingest 2H2O (to measure the contribution of gluconeogenesis to glucose production from the C5/C2 2H-labeling ratio in glucose), and will be infused with (6,6-2H2) glucose (to measure glucose turnover). The 2H-enrichment at the glucose carbons will be amplified six-fold by incorporating them into hexamethylenetetramine for assay. The contribution of gluconeogenesis will be related to hepatic glycogen content measured by 13C-NMR spectroscopy. Our studies will define the role of gluconeogenesis (i) in diabetic hyperglycemia, (ii) as a possible etiologic factor in the onset of NIDDM, and (iii) in the mechanism of metformin's action. They will help establish whether the propensity of upper body obese subjects to insulin resistance, NlDDM, and cardiovascular disease is related to increased gluconeogenesis. Also, the direct conversion of glycogen to glucose may prove to be an important regulator of glycogen content. Our studies will shed new light on how glucose and lipid metabolism in adipose tissue adapts to fasting.