Metabolic inflexibility is related to elevated muscle anaerobic glycolysis

摘要 肥胖和代谢综合征在美国很普遍，是发病率和 死亡率。本申请中的研究旨在确定特定的代谢表型(依赖程度增加 骨骼肌无氧糖酵解和代谢不灵活)在超重个体中是明显的和 与严重肥胖者的体重相近。超重受试者将被选为高空腹和低空腹乳酸 浓度(厌氧糖酵解的一个指标)，并接受葡萄糖钳夹和肌肉活检 在静息状态下获得(目标1)。严重肥胖组将接受与初选相同的测试 变量为基础和胰岛素刺激的体内肌肉底物氧化(近红外光谱分析； 近红外光谱(NIRS)、肌肉乳酸释放(微透析)、粗面内质网、肌肉匀浆氧化丙酮酸和脂肪 酸。次要变量是静息/空腹血浆乳酸、全身醋酸盐氧化、肌纤维类型、 通透性纤维在不同底物作用下的耗氧量、线粒体数量 蛋白质、VO2峰、REE、RER、体型(3D扫描仪)和身体成分(DEXA)。在目标2a中，数据来自 该钳将用于评估新陈代谢的灵活性。主要变量是代谢灵活性(变化 对胰岛素和葡萄糖的反应)；底物氧化(近红外光谱和肌肉匀浆氧化 丙酮酸和脂肪酸)；以及厌氧糖酵解(钳夹期间肌肉乳酸的释放)。次要的 变量是外周和肝脏的胰岛素敏感性。在目标2b中，对3天高脂肪饮食的反应将是 在饮食前后进行测定和肌肉活检。主要变量是以下指标 代谢灵活性对HFD和底物氧化的响应(NIRS，肌肉匀浆氧化 丙酮酸和脂肪酸)和体内肌肉乳酸的产生。次要变量是外围变量和 肝脏胰岛素敏感性。目标2c将检验从研究中获得的原代细胞培养的能力。 易受胰岛素或脂肪孵育的影响。主要的变量是新陈代谢的灵活性 葡萄糖胰岛素(胰岛素对葡萄糖氧化和乳酸产生的刺激)和代谢灵活性 对脂肪的反应(与脂肪酸孵育24小时后，脂肪酸氧化增加)。目标3将决定是否 恢复严重肥胖者代谢灵活性的干预措施(胃旁路手术)将 还可以减少对厌氧糖酵解的依赖。受试者将接受葡萄糖钳夹和肌肉活组织检查 手术前后。主要变量是代谢灵活性(RER对葡萄糖的响应变化 夹住时的胰岛素)，底物氧化(近红外光谱，肌肉匀浆氧化丙酮酸和脂肪酸) 体内肌肉乳酸的释放。次要变量是静息/空腹乳酸、外周和肝脏 培养的肌肉细胞的胰岛素敏感性、全身醋酸盐氧化和代谢灵活性。的意图 这项研究是为了确定随后发展为肥胖的风险个体的指数。

Summary Obesity and the metabolic syndrome are prevalent in the United States and responsible for morbidity and mortality. The studies in this application aim to determine if a specific metabolic phenotype (increased reliance on anaerobic glycolysis in skeletal muscle and metabolic inflexibility) in overweight individuals is evident and approximates that of the severely obese. Overweight subjects will be selected for high and low fasting lactate concentrations (an indicator of anaerobic glycolysis) and undergo a glucose clamp with a muscle biopsy obtained in the resting state (Aim 1). A severely obese group will undergo the same tests with the primary variables being basal and insulin stimulated in vivo muscle substrate oxidation (near infrared spectrospopy; NIRS), muscle lactate release (microdialysis), RER, and muscle homogenate oxidation of pyruvate and fatty acids. Secondary variables are resting/fasting plasma lactate, whole body acetate oxidation, muscle fiber type, oxygen consumption in permeabilized fibers exposed to various substrates, quantities of mitochondrial proteins, VO2peak, REE, RER, body shape (3D-scanner) and body composition (DEXA). In Aim 2a, data from the clamp will be used to assess metabolic flexibility. The primary variables are metabolic flexibility (change in RER in response to insulin + glucose); substrate oxidation (NIRS and muscle homogenate oxidation of pyruvate and fatty acids); and anaerobic glycolysis (muscle lactate release during the clamp). Secondary variables are peripheral and hepatic insulin sensitivity. In Aim 2b, responses to a 3-day high fat diet will be determined and muscle biopsies obtained before and after the diet. The primary variables are indices of metabolic flexibility in response to the HFD and substrate oxidation (NIRS, muscle homogenate oxidation of pyruvate and fatty acids) and in vivo muscle lactate production. Secondary variables are peripheral and hepatic insulin sensitivity. Aim 2c will examine the ability of primary cell cultures derived from the research subject to respond to insulin or lipid incubation. The primary variables are metabolic flexibility in response to glucose + insulin (insulin stimulation of glucose oxidation and lactate production) and metabolic flexibility in response to fat (increase in fatty acid oxidation after 24 hr incubation with fatty acids). Aim 3 will determine if an intervention (gastric bypass surgery) which restores metabolic flexibility in severely obese individuals will also reduce dependence on anaerobic glycolysis. Subjects will undergo a glucose clamp and a muscle biopsy before and after the surgery. Primary variables are metabolic flexibility (change in RER in response to glucose + insulin during a clamp), substrate oxidation (NIRS, muscle homogenate oxidation of pyruvate and fatty acids) and in vivo muscle lactate release. Secondary variables are resting/fasting lactate, peripheral and hepatic insulin sensitivity, whole-body acetate oxidation, and metabolic flexibility of cultured muscle cells. The intent of this research is to determine indices of individuals at risk for the subsequent development of obesity.