Impact of insulin on lactate metabolism

项目总结/摘要 本研究的目的是探讨胰岛素促进乳酸燃烧的假说， 为将来研究这种调节对葡萄糖稳态和糖尿病的重要性奠定了基础。 通过糖酵解和糖异生相互转化，葡萄糖和乳酸代谢紧密结合。 连接.乳酸产生和消耗之间的不平衡导致乳酸浓度改变， 这会影响神经功能。此外，乳酸积累（高乳酸血症）是最常见的 在危重病人中遇到代谢改变。了解乳酸盐生产的控制， 因此，利用是医学上相关的，特别是为了更完全地阐明型糖尿病的病理生理学。 2糖尿病.然而，与葡萄糖不同的是，调节乳酸稳态的机制在很大程度上是未知的。 在这里，我将研究胰岛素对乳酸代谢的全身性和组织特异性影响， 胰岛素通过TCA循环促进乳酸氧化，并探讨其生化机制。到 为此，目标1将研究胰岛素对全身和器官特异性TCA循环活性的影响。到 测量胰岛素对全身能量代谢的影响，在短暂禁食后将胰岛素给予小鼠， 并且氧气消耗和二氧化碳产生将通过间接量热法测量。了解 胰岛素对器官特异性TCA代谢的影响，将使用 新的动态同位素示踪方法结合LC-MS和通量建模。目标2将探讨机制 胰岛素通过其改变组织TCA代谢。特别是，我将评估乳酸增加是否 对TCA循环的贡献取决于（i）胰岛素对葡萄糖摄取的诱导，（ii）胰岛素对脂肪代谢的抑制， 脂肪分解和作为替代燃料的循环游离脂肪酸的相关减少，或（iii）胰岛素的直接 刺激乳酸燃烧，可能通过调节丙酮酸脱氢酶（PDH）活性。这些替代品 将使用基因工程小鼠模型和体内代谢通量分析进行严格检查。 这些研究的完成将大大促进对哺乳动物代谢的理解， 阐明了一个可能对代谢性疾病发病机制具有重要意义的潜在主要调节机制， 综合征申请人在细胞代谢通量分析方面具有独特的既有优势， 亚细胞水平，但以前没有在体内工作。因此，培训计划旨在建立 生理学知识，动物处理技能和生物体水平的定量建模能力。采集 这些技术知识，再加上领导能力的进一步发展，将使申请人能够 最终成为一名开拓性的独立科学家，在空间尺度上定量研究新陈代谢， 从亚细胞到有机体

Project Summary/Abstract The goal of this research is to explore the hypothesis that insulin promotes lactate burning, and to lay the groundwork for future investigation of the importance of such regulation to glucose homeostasis and diabetes. Actively transformed to each other by glycolysis and gluconeogenesis, glucose and lactate metabolism are tightly connected. Imbalances between lactate production and consumption lead to altered lactate concentrations, which can affect glycemia. Moreover, lactate accumulation (hyperlactatemia) is one of the most frequently encountered metabolic alterations in critically ill patients. Understanding the control of lactate production and utilization is therefore medically relevant, especially for more completely elucidating the pathophysiology of type 2 diabetes. Unlike for glucose, however, the mechanisms regulating lactate homeostasis are largely unknown. Here I will investigate the systemic and tissue-specific impact of insulin on lactate metabolism, test the hypothesis that insulin promotes lactate oxidation via TCA cycle, and explore the underlying biochemical mechanisms. To this end, Aim 1 will investigate the impact of insulin on whole-body and organ-specific TCA cycle activity. To measure the effect of insulin on whole body energy metabolism, insulin will be given to mice after short fasting, and oxygen consumption and carbon dioxide production will be measured by indirect calorimetry. To understand the impact of insulin on organ-specific TCA metabolism, TCA flux in individual organs will be quantified, using a novel dynamic isotope tracing approach coupled to LC-MS and flux modeling. Aim 2 will explore the mechanisms by which insulin changes tissue TCA metabolism. In particular, I will assess whether increased lactate contribution to TCA cycle depends on (i) insulin’s induction of glucose uptake, (ii) insulin’s inhibition of adipose lipolysis and associated decrease in circulating free fatty acids as alternative fuels, or (iii) insulin’s direct stimulation of lactate burning, likely via regulation of pyruvate dehydrogenase (PDH) activity. These alternatives will be rigorously examined using genetically engineered mouse models and in vivo metabolic flux analysis. Completion of these studies is poised to substantially advance understanding of mammalian metabolism, by illuminating a potentially major regulatory mechanism of likely importance to the pathogenesis of metabolic syndrome. The applicant brings unique pre-existing strengths in metabolic flux analysis at the cellular and subcellular level, but has not previously worked in vivo. Accordingly, the training program is designed to build physiological knowledge, animal handling skills, and organismal-level quantitative modeling capacity. Acquisition of this technical knowledge, combined with further growth in leadership abilities, will position the applicant to eventually become a pioneering independent scientist, studying metabolism quantitatively across spatial scales, from subcellular to organismal.