MITOCHONDRIAL FUNCTION AND INSULIN RESISTANCE

线粒体功能和胰岛素抵抗

• 批准号: 8363888
• 负责人: CHRISTOPHER B NEWGARD
• 金额: $ 1.61万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8363888
• 关键词: ATP Synthesis Pathway; Acetates; Amino Acids; Animal Model; Animals; Biochemistry; Biological; Blood Glucose; Branched-Chain Amino Acids; Caprylates; Carnitine; Cells; Citric Acid Cycle; Complex; Conscious; Diabetes Mellitus; Diet; Fatty acid glycerol esters; Funding; Gluconeogenesis; Glucose; Glutamates; Glycerol; Goals; Grant; Hand; Head; Hepatic; Human; Hydroxybutyrates; Hyperglycemia; Hyperinsulinism; Individual; Infusion procedures; Insulin Resistance; Investigation; Isotope Labeling; Label; Link; Lipids; Liver; Measurement; Measures; Metabolism; Methods; Mitochondria; Monitor; Muscle; National Center for Research Resources; Nutrient; Organ; Overweight; Pathway interactions; Patient Selection; Patients; Pattern; Plasma; Principal Investigator; Propionates; Protocols documentation; Pyruvate; Rattus; Research; Research Infrastructure; Resources; Rest; Skeletal Muscle; Source; Technology; Testing; Tracer; Translating; United States National Institutes of Health; acylcarnitine; blood glucose regulation; cost; glucose production; glycogenolysis; human subject; in vivo; insulin secretion; liver function; muscle metabolism; oxidation; programs; research study; skeletal; technology development

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Coexistence of hyperglycemia and hyperinsulinemia indicates profound disruption of the glucose homeostasis functions of liver and skeletal muscle. This Project (Project 4 of a Program Project headed by Dr. Newgard) is motivated by the desire to understand the interaction of branched chain amino acids (BCAAs) with intermediary metabolism in both organs in human subjects. As outlined in the Overview section and Project 1 of this application, BCAAs may compete with other macro-nutrients for oxidation in skeletal muscle, and anaplerotic fluxes in both muscle and liver may be abnormal. In the presence of a high fat diet, anticipated secondary effects include accumulation of acylcarnitines and intra-cellular lipids in muscle, both markers of skeletal insulin resistance. Of course, specific amino acids also have complex effects on insulin secretion, carnitine metabolism and other aspects of biochemistry, and at this point it is not clear if abnormal BCAA metabolism significantly impacts mitochondrial function in either organ. Our colleagues in Projects 1, 2 and 3 of the Program Project will test these ideas in isolated cells and in animal models, but there will still be a need to measure fluxes in relevant pathways and measure specific metabolites in both the liver and skeletal muscle in relevant human subjects. In spite of the potential power of 13C tracer methods for studying skeletal muscle metabolism, this technology is little used, outside of a handful of labs, for one simple reason: suitable 13C enriched substrates that compete effectively for oxidation in the citric acid cycle have not been identified. A focus is to develop better methods to deliver high 13C enrichment of citric acid cycle intermediates in skeletal muscle and liver simultaneously. Although the immediate target is to assess biochemistry in the setting of elevated plasma BCAAs, these new methods will be widely applicable to studies of human metabolism and are in keeping with the historical theme of this program project of linking technology development with hypothesis-driven diabetes investigation. The specific aims of the project are as follows: 1) To develop a protocol that labels citric acid cycle intermediates with 13C to a high level (>20%) in both skeletal muscle and liver in conscious rats. In separate experiments, 13C-enriched acetate, ¿ hydroxybutyrate plus propionate, octanoate, and lactate or pyruvate will be infused intravenously, and 13C enrichment in skeletal muscle glutamate, hepatic glutamate and blood glucose will be determined at steady-state. The combination of tracer(s) that yield the best combination of high 13C enrichment in skeletal muscle and plasma glucose will be selected for further studies in humans. 2) To translate the 13C infusion protocol developed in animals to healthy human subjects and refine 31P magnetization transfer methods. The infusion conditions necessary to achieve steady-state isotope labeling in skeletal muscle will be determined by serial 1H decoupled 13C NMR spectra at 7T. The 13C labeling pattern in plasma glucose will be monitored to assure steady-state in glucose isotopomers and to determine whether 13C enriched glucose, generated by the liver, contributes significantly to plasma glucose. In this aim, we will also compare two 31P NMR methods, inversion transfer and saturation transfer, for measurement of ATP synthesis rates in resting skeletal muscle. 3) To test the primary hypothesis that overweight subjects with elevated BCAAs have altered mitochondrial function in skeletal muscle plus altered liver gluconeogenesis. Selection of patients will be achieved by analysis of BCAA and related metabolites by Core B of this program. Specifically, we anticipate that skeletal muscle mitochondrial function (ATP turnover by 31P NMR) may be normal in these individuals but that intermediary skeletal muscle metabolism in these individuals will be altered as reflected by excess IMCL, excess acylcarnitines and an increase in anaplerosis. We will also test whether the network of glucose production pathways  glycogenolysis, gluconeogenesis from glycerol and gluconeogenesis from the citric acid cycle  in liver is abnormal among these subjects. In summary, our goal is to integrate new high field NMR technologies with those already largely in hand for understanding mitochondrial function in liver and skeletal muscle of humans, thereby serving as a project that translates the biological / mechanistic findings of Projects 1, 2, and 3 to human studies. A high priority will be placed on developing a protocol that will be well-accepted by patients.

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 子项目的主要研究者可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， NCRR赠款不直接向子项目或子项目工作人员提供资金。 高血糖和高胰岛素血症的共存表明肝脏和骨骼肌的葡萄糖稳态功能的严重破坏。该项目（由Newgard博士领导的项目4）的动机是希望了解支链氨基酸（BCAAs）与人类受试者两个器官中的中间代谢的相互作用。如本申请的概述部分和项目1所述，支链氨基酸可能与其他大量营养素竞争骨骼肌中的氧化，肌肉和肝脏中的回补通量可能异常。在存在高脂肪饮食的情况下，预期的次要作用包括酰基肉毒碱和肌肉中细胞内脂质的积累，这两种标志物都是骨骼胰岛素抵抗。 当然，特定的氨基酸也对胰岛素分泌，肉毒碱代谢和生物化学的其他方面有复杂的影响，目前尚不清楚异常的BCAA代谢是否会显著影响任一器官的线粒体功能。我们在项目1、2和3中的同事将在分离的细胞和动物模型中测试这些想法，但仍然需要测量相关途径中的通量，并测量相关人类受试者肝脏和骨骼肌中的特定代谢物。尽管13 C示踪方法用于研究骨骼肌代谢的潜在能力，但除了少数实验室之外，这种技术很少使用，原因很简单：尚未确定在柠檬酸循环中有效竞争氧化的合适的13 C富集底物。一个重点是开发更好的方法，以提供高13 C富集柠檬酸循环中间体在骨骼肌和肝脏同时。虽然当前的目标是在血浆支链氨基酸升高的情况下评估生物化学，但这些新方法将广泛适用于人体代谢研究，并符合该计划项目的历史主题，即将技术开发与假设驱动的糖尿病研究联系起来。 该项目的具体目标如下： 1)开发一种在清醒大鼠的骨骼肌和肝脏中用13 C标记柠檬酸循环中间体的方案，使其达到高水平（>20%）。 在单独的实验中，将静脉输注13 C富集的乙酸盐、羟基丁酸盐加丙酸盐、辛酸盐和乳酸盐或丙酮酸盐，并在稳态下测定骨骼肌谷氨酸盐、肝谷氨酸盐和血糖中的13 C富集。 将选择产生骨骼肌中高13 C富集和血浆葡萄糖的最佳组合的示踪剂组合用于在人体中的进一步研究。 2)将在动物中开发的13 C输注方案转化为健康的人类受试者，并改进31 P磁化转移方法。在骨骼肌中实现稳态同位素标记所需的输注条件将通过7 T下的系列1H去耦13 C NMR光谱来确定。 将监测血浆葡萄糖中的13 C标记模式，以确保葡萄糖同位素异构体的稳态，并确定肝脏产生的13 C富集葡萄糖是否对血浆葡萄糖有显著贡献。 在这个目标中，我们还将比较两种31 P NMR方法，反转转移和饱和转移，用于测量静息骨骼肌ATP合成速率。 3)检验BCAA升高的超重受试者骨骼肌线粒体功能改变和肝脏新生改变的主要假设。 通过本项目核心B分析BCAA和相关代谢物来选择患者。 具体而言，我们预计，骨骼肌线粒体功能（ATP营业额31 P NMR）可能是正常的，在这些人，但在这些人中间骨骼肌代谢将被改变，反映了过量IMCL，过量酰基肉毒碱和回补的增加。我们还将测试葡萄糖产生途径的网络是否  糖原分解、甘油的异生和柠檬酸循环的异生  肝脏的异常。 总之，我们的目标是将新的高场NMR技术与那些已经掌握的用于了解人类肝脏和骨骼肌中线粒体功能的技术相结合，从而将项目1，2和3的生物学/机械学发现转化为人类研究。 一个高度优先事项将放在制定一个协议，将被病人接受。