Role of Txnip in adapting fuel metabolism to nutritional state

Txnip 在使燃料代谢适应营养状态中的作用

• 批准号: 8136515
• 负责人: Simon To-Yuen Hui
• 金额: $ 32.83万
• 依托单位: UNIVERSITY OF CALIFORNIA LOS ANGELES
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2014-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8136515
• 关键词: 5' -AMP-activated protein kinase; Ablation; Antioxidants; Apoptosis; Autophagocytosis; Binding; Biogenesis; Cardiovascular Diseases; Cell physiology; Cells; Characteristics; Cholecalciferol; Congenic Mice; DNA; Data; Defect; Development; Diabetes Mellitus; Diet; Electron Microscopy; Electron Transport; Embryo; Energy Metabolism; Exhibits; Extrahepatic; Fasting; Fatty acid glycerol esters; Feedback; Fibroblasts; First Name; Food deprivation (experimental); Gene Expression; Genes; Glucose; Glutathione; Glycolysis; Goals; HL60; Health; Heart; Human; Hypoglycemia; Insulin; Ketone Bodies; Knock-out; Knockout Mice; Knowledge; Lead; Life; Link; Lipids; Liver; Measures; Mediating; Metabolic; Metabolism; Mitochondria; Modeling; Molecular; Mouse Strains; Mus; Muscle; Mutation; Myocardium; NAD+ kinase; NADP; Nutritional; Nutritional status; Obesity; Organism; Oxidation-Reduction; Oxidative Phosphorylation; Oxidative Stress; PTEN gene; Pathway interactions; Pentosephosphate Pathway; Phenotype; Physiological; Play; Polarography; Prevention; Process; Production; Proteins; Proteomics; Public Health; Quality Control; Reactive Oxygen Species; Recombinants; Recommendation; Regulation; Regulatory Pathway; Research; Resistance; Respiration; Role; Signal Pathway; Signal Transduction; Site; Skeletal Muscle; Study Section; Sulfhydryl Compounds; System; Testing; Therapeutic; Thioredoxin; Tissues; design; glucose uptake; human TXNIP protein; insight; insulin sensitivity; interest; lipid metabolism; mitochondrial dysfunction; oxidation; oxidative damage; positional cloning; response

DESCRIPTION (provided by applicant): The ability to properly respond to prolonged periods of nutritional scarcity is vital to the survival of all living organisms. Thioredoxin interacting protein (Txnip) is a key metabolic regulator of this important adaptation process. Txnip modulates cellular sulfhydryl redox through its binding to thioredoxin and thereby inhibiting its redox function. Txnip knockout (TKO) mice become hypoglycemia, hypertriglycerdemia and hyperketonemia when fasted and cannot survive long-term fasting. Using tissue-specific Txnip knockout mice, we have identified that impaired mitochondrial oxidation in the muscle is the major contributor leading to these metabolic abnormalities. To compensate for energy deficiency, glucose uptake and glycolysis are elevated. Despite having impaired mitochondrial oxidation, TKO mice showed increased insulin/Akt signaling due to decreased amount of active PTEN (reduced form) and were resistance to high fat diet-induced diabetes. The goal of our proposed studies is to understand the molecular mechanisms by which Txnip alters mitochondrial function. Aim 1 is focused on identification of molecular defects leading to impaired mitochondrial oxidation in TKO mice. Electron microscopy will be used to detect alterations in mitochondrial ultrastructure. Mitochondrial respiration will be measured by polarography and the defective component in the oxidative phosphorylation pathway will be identified. Preliminary data obtained since our last submission showed that cellular NADPH level is decreased in TKO hearts. In Aim 2, we will test the hypothesis that lower NADPH availability increases mitochondrial oxidative stress, thereby leads to impaired fuel oxidation. Cellular antioxidant and ROS defense system will be measured as well as the levels of oxidative modified proteins, DNA and lipids in the mitochondria. To show the causative link between NADPH levels and mitochondrial function, NADPH levels in TKO embryonic fibroblasts will be modulated by adenoviral expression of NAD kinase. Correlation between cellular NADPH levels and mitochondrial oxidative stress and respiration will be determined. Our preliminary data also showed that AMPK signalling pathway is blunted in TKO mice. Aim 3 is to determine the link between blunted AMPK signaling and impaired mitochondrial function in TKO mice. The AMPK regulatory pathway will be dissected so as to determine how Txnip ablation causes impaired AMPK activation. Constitutively active AMPK will be expressed in TKO fibroblasts to test if correct AMPK signalling could rescue the respiration defective phenotype. Aim 4 is to determine how Txnip modulates mitochondrial function. Using targeted expression of wild-type and various mutations of Txnip in TKO fibroblasts, we will identify the subcellular site of action of Txnip and its essential functional features necessary for modulating mitochondrial oxidation. In addition, proteomics approach will be used to identify partners interacting with Txnip. This integrative approach will provide fundamental new knowledge on how Txnip regulates mitochondrial function and its link to metabolic regulation. PUBLIC HEALTH RELEVANCE: We have identified that Txnip is essential for maintaining proper metabolic response to changes in nutritional status and demonstrated that Txnip modulates mitochondrial fuel oxidation and insulin sensitivity in cardiac and skeletal muscle. Mitochondrial dysfunction and abnormal fuel metabolism are linked to the development of obesity, diabetes and cardiovascular disease. Results of this proposed research will provide fundamental information that may lead to better prevention and/or therapeutics for diabetes and cardiovascular disease in humans.

描述（由申请人提供）：适当应对延长营养短缺时期的能力对于所有生物体的生存至关重要。硫氧还蛋白相互作用蛋白（TXNIP）是这种重要适应过程的关键代谢调节剂。 TXNIP通过与硫氧还蛋白的结合调节细胞硫氧化还原，从而抑制其氧化还原功能。禁食时，TXNIP敲除（TKO）小鼠成为低血糖，高糖基糖症和高酮血症，无法在长期禁食中存活。使用组织特异性TXNIP敲除小鼠，我们已经确定肌肉中的线粒体氧化受损是导致这些代谢异常的主要因素。为了补偿能源缺乏，葡萄糖摄取和糖酵解升高。尽管线粒体氧化受损，但TKO小鼠由于有效PTEN量减少（减少形式）而显示出胰岛素/AKT信号的增加，并且对高脂肪饮食诱导的糖尿病具有抗性。我们提出的研究的目的是了解TXNIP改变线粒体功能的分子机制。 AIM 1的重点是鉴定分子缺陷，导致TKO小鼠线粒体氧化受损。电子显微镜将用于检测线粒体超微结构的改变。线粒体呼吸将通过极光学来测量，将确定氧化磷酸化途径中的缺陷成分。自上次提交以来获得的初步数据表明，TKO心脏中细胞NADPH水平降低。在AIM 2中，我们将检验以下假设：较低的NADPH可用性会增加线粒体氧化应激，从而导致燃料氧化受损。将测量细胞抗氧化剂和ROS防御系统，以及线粒体中氧化改性蛋白，DNA和脂质的水平。为了显示NADPH水平与线粒体功能之间的因果关系，TKO胚胎成纤维细胞中的NADPH水平将通过NAD激酶的腺病毒表达来调节。将确定细胞NADPH水平与线粒体氧化应激和呼吸之间的相关性。我们的初步数据还表明，TKO小鼠中AMPK信号通路被钝化。 AIM 3是确定TKO小鼠中钝化的AMPK信号传导和线粒体功能受损之间的联系。将阐述AMPK调节途径，以确定TXNIP消融如何导致AMPK激活受损。组成性活性AMPK将在TKO成纤维细胞中表达，以测试正确的AMPK信号是否可以挽救呼吸有缺陷的表型。 AIM 4是确定TXNIP如何调节线粒体功能。使用野生型的靶向表达和TKO成纤维细胞中TXNIP的各种突变，我们将确定TXNIP的亚细胞作用位点及其调节线粒体氧化所必需的必要功能特征。此外，蛋白质组学方法将用于识别与TXNIP相互作用的伴侣。这种综合方法将提供有关TXNIP如何调节线粒体功能及其与代谢调节的联系的基本新知识。公共卫生相关性：我们已经确定TXNIP对于维持对营养状况变化的适当代谢反应至关重要，并证明TXNIP调节心脏和骨骼肌中的线粒体燃料氧化和胰岛素敏感性。线粒体功能障碍和异常燃料代谢与肥胖，糖尿病和心血管疾病的发展有关。这项拟议的研究的结果将提供基本信息，从而可以改善人类糖尿病和心血管疾病的预防和/或治疗疗法。