Metabolic Signal Transduction in Adipocytes

描述(申请人提供)：调节脂肪的储存、释放和分泌是新陈代谢健康的关键。氧化还原是细胞内细胞功能的重要介质，通过血液代谢产物在细胞之间进行沟通。细胞外氧化还原是由脂肪细胞通过代谢产物和氨基酸感受到的，在那里它们可能作为脂肪细胞燃料处理和脂肪因子分泌的主要调节器。循环中的氧化还原代谢物由细胞产生并连接全身所有组织：包括硫醇(SH/SS)比率(反映在半胱氨酸/半胱氨酸和GSH/GSSG比率)、线粒体氧化还原状态(反映在ss-羟丁酸(ss-OHB)/乙酰乙酸酯(ACoC)比率(B/A))和胞浆氧化还原状态(反映在乳酸/丙酮酸比率(L/P))。氧化还原比率随着代谢状态(高脂肪饮食、禁食、糖尿病)、衰老和氧化应激而改变。许多观察结果支持氧化还原变化与活性氧和氮物种(ROS)之间的因果关系。在之前的授权期，我们证明了脂肪细胞通过线粒体机制产生ROS，并且丙酮酸清除ROS刺激了O2的消耗。我们还发现，体内摄入ROS清除剂N-乙酰半胱氨酸，可以增加呼吸，减少体内脂肪。我们的长期目标是通过调节脂肪组织功能来改善代谢健康。在这项应用中，我们将确定氧化还原介导的ROS产生改变脂代谢、脂肪因子分泌和线粒体对细胞外B/A或L/P比率或硫醇氧化状态变化的反应的条件，并将这些发现应用于动物。我们认为ROS诱导脂解的调节机制涉及线粒体自噬和ROS水平的调节。该应用将探索一种假设，即氧化还原作为代谢和线粒体反应的主要调节因子，通过线粒体生物能量学和自噬来调节ROS的产生、燃料的命运以及脂肪因子的分泌。目的1是确定影响脂肪分解、甘油三酯合成和脂肪因子分泌的最有效途径，并确定这些变化与细胞内氧化还原和ROS生成的关系。这些研究将确定调节脂肪细胞功能的代谢物或对，以及它们之间的相互关系。目的2通过评估RS对线粒体生物能量学、自噬和动力学的影响，探讨RS诱导的脂质处理和分泌功能改变的机制。这些研究将提供机制信息，并识别其修饰影响细胞功能的蛋白质。目的3是通过给动物喂食或输液来翻译氧化还原和RS诱导的脂质处理和脂肪因子的分泌。这些研究将为未来的人体研究提供必要的基础，以测试经过验证的概念。这些研究的结果将决定应用天然氧化还原机制来调节脂肪细胞的脂肪处理和脂肪因子分泌，以改善由过量脂肪组织引起的代谢健康的可行性。

DESCRIPTION (provided by applicant): Regulation of fat storage, release and secretion is key to metabolic health. Redox is an important mediator of cell function within cells that is communicated among cells by blood metabolites. Extracellular redox is sensed by fat cells, via metabolites and amino acids, where they may function as master regulators of adipocyte fuel handling and adipokine secretion. The circulating redox metabolites are produced by cells and link all tissues of the body: couples include the thiol (SH/SS) ratios, reflected in the cysteine/cystine and GSH/GSSG ratios, the mitochondrial redox state reflected in the ss-hydroxybutyrate (ss-OHB)/ acetoacetate (Acoc) ratio (B/A) and the cytosolic redox state reflected in the lactate/pyruvate ratio (L/P). Redox ratios change in response to metabolic status (high fat diet, fasting, diabetes), aging, and oxidative stress. Many observations support a causal relationship between redox changes and reactive oxygen and nitrogen species (ROS). During the prior grant period, we demonstrated that adipocytes generate ROS via a mitochondrial mechanism and that scavenging ROS with pyruvate stimulated O2 consumption. We also found that consumption of the ROS scavenger, n-acetyl cysteine, increased respiration and decreased body fat in vivo. Our long-term goal is to improve metabolic health by regulating adipose tissue function. In this application we will identify conditions where redox-mediated ROS generation alters lipid metabolism, adipokine secretion and mitochondrial responses to variations in the extracellular B/A or L/P ratio or thiol oxidation state and applying these findings to animals. We propose that the mechanism for ROS induced regulation of lipolysis involves mitochondrial autophagy and regulation of ROS levels. The application will explore the hypothesis that redox, as a master regulator of metabolic and mitochondrial responses, regulates generation of ROS, the fate of fuels, and adipokine secretion via mitochondrial bioenergetics and autophagy. Aim 1 is to determine the most effective way to impact lipolysis, triglyceride synthesis and adipokine secretion and determine how such changes relate to intracellular redox and ROS generation. These studies will define the metabolites or couples that modulate adipocyte function and the interrelationship if any among them. Aim 2 is to determine the mechanism of RS-induced functional changes on lipid handling and secretion by assessing the effect of the couples on mitochondrial bioenergetics, autophagy and dynamics. These studies will provide mechanistic information and identify proteins whose modification impacts cell function. Aim 3 is to translate redox and RS-induced lipid handling and adipokine secretion by feeding or infusion into animals. These studies will provide the essential underpinning for future human studies to test the validated concepts. The outcome of these studies will determine the feasibility of applying natural redox mechanisms to regulate adipocyte lipid handling and adipokine secretion to improve metabolic health caused by excess fat tissue.