FAT AND CARBOHYDRATE METABOLISM IN SKELETAL MUSCLE

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 这项核心研究和技术开发项目有三个目标。所有这些都与新方法的发展有关，以测量对人类脂肪和碳水化合物生物化学重要的关键通量和代谢物。从长远来看，我们设想了一套临床研究方案，包括全身给药13C和2H，以确定全身葡萄糖产生的动力学，肝脏脂肪酸氧化等，这是理解胰岛素抵抗状态的生理学的基础。同时，器官特异性磁共振成像和光谱可以用来探测骨骼肌和肝脏等关键器官的新陈代谢。基于我们在代谢稳定同位素分析方面的成功，加上我们在磁化转移造影剂(PARACEST试剂)方面的最新进展，这一目标可以在实验动物中实现，并将在人类受试者身上进行概念验证开发。具体目标1是在啮齿动物模型中实施和评估新的代谢成像方法。MRI的葡萄糖成像将在三组大鼠中进行研究：对照组动物、甲亢大鼠和Zucker肥胖大鼠。通过对营养状态和胰升糖素的调控，改变整个动物体内葡萄糖的浓度和分布。葡萄糖周转、尿素周转、酮生成、全身性脂肪分解和肝脏13氧化的同时测量将用同位素方法测定。具体目标#2是继续开发测量受试者肝脏13氧化、全身脂肪分解、糖异生和肝脏TCA循环通量的方法。临床和科学界希望能够定期测量肝脏中的脂肪酸氧化。在核心3的这一目标中，核心1开发的方法将扩展到患者和志愿者。将在三个人群中测量肝脏糖异生和氧化作用：禁食、高脂饮食和2型糖尿病。我们已经展示了在这些不同的代谢状态下葡萄糖产生途径的代谢变化，其中一些是戏剧性的变化。最后，具体目标#3是评估T2糖尿病患者骨骼肌细胞内脂肪含量和线粒体功能。T2D患者可能存在心肌细胞内脂肪含量异常、肝糖异生过多和线粒体功能普遍缺陷。在空腹对照组和年龄匹配的2型糖尿病患者的小腿肌肉中，将进行三项测量：细胞内脂肪含量、ATP合成速率(通过31P核磁共振磁化转移)和柠檬酸循环通量(通过1H去偶联，13C观察核磁共振)。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This core research and technology development project has three aims. All are related to the development of new approaches to measuring key fluxes and metabolites important to fat and carbohydrate biochemistry in people. Over the long term, we envision a set of clinical research protocols involving systemic administration of 13C and 2H to determine the kinetics of whole-body glucose production, hepatic fatty acid oxidation, etc., whichare fundamental to understanding the physiology of insulin-resistant states. Simultaneously, organ-specific MR imaging and spectroscopy can be used to probe metabolism in critical organs such as skeletal muscle and liver. Based on our success with stable isotope analysis of metabolism plus our recent progress with magnetization transfer contrast agents (PARACEST agents), this goal can be achieved in experimental animals, and proof-of-concept development will be carried out in human subjects. Specific Aim #1 is to implement and evaluate new metabolic imaging methods in rodent models. Glucose imaging by MRI will be studied in three populations of rats: control animals, hyperthyroid rats, and Zucker fatty rats. By manipulation of nutritional state and glucagon, the concentration and distribution of glucose will be altered in the whole animal. Simultaneous measures of glucose turnover, urea turnover, ketone production, systemic lipolysis and hepatic 13 oxidation will be determined by isotope methods. Specific Aim #2 is to continue development of methods to measure hepatic 13 - oxidation, whole-body lipolysis, gluconeogenesis and hepatic TCA cycle flux in human subjects. The clinical and scientific community wants to be able to routinely measure fatty acid oxidation in the liver. In this Aim of Core 3, methods developed in Core 1 will be extended to patients and volunteers. Hepatic gluconeogenesis and 13 oxidation will be measured in three human populations: fasting, high fat diet, and type 2 diabetes. We have already shown metabolic changes in glucose production pathways in these various metabolic states, some of which are dramatic changes. Finally, specific Aim #3 is to assess intramyocellular fat content and mitochondrial function in skeletal muscle of patients with T2 diabetes. Abnormal intramyocellular fat content, excess hepatic gluconeogenesis, and a widespread defect in mitochondrial function have been postulated among patients with T2D. In calf muscle of fasted control subjects and age matched patients with type 2 diabetes, three measurements will be made: intramyocellular fat content, ATP synthesis rates (by 31p NMR magnetization transfer) and citric acid cycle flux (by 1 H decouple, 13C observe NMR).