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

基本信息

批准号：
8520294
负责人：
Simon To-Yuen Hui
金额：
$ 31.68万
依托单位：
UNIVERSITY OF CALIFORNIA LOS ANGELES
依托单位国家：
美国
项目类别：
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/8520294
关键词：
5&apos -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

项目摘要

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）：正确应对长期营养短缺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）是这一重要适应过程的关键代谢调节因子。 Txnip 通过与硫氧还蛋白结合来调节细胞硫氢基氧化还原，从而抑制其氧化还原功能。 Txnip 基因敲除（TKO）小鼠在禁食时会出现低血糖、高甘油三酯血症和高酮血症，并且无法长期禁食。使用组织特异性 Txnip 敲除小鼠，我们发现肌肉中线粒体氧化受损是导致这些代谢异常的主要原因。为了补偿能量不足，葡萄糖摄取和糖酵解会升高。尽管线粒体氧化受损，但 TKO 小鼠由于活性 PTEN（还原型）数量减少而表现出胰岛素/Akt 信号增强，并且对高脂肪饮食诱导的糖尿病具有抵抗力。我们提出的研究的目标是了解 Txnip 改变线粒体功能的分子机制。目标 1 重点是鉴定导致 TKO 小鼠线粒体氧化受损的分子缺陷。电子显微镜将用于检测线粒体超微结构的变化。将通过极谱法测量线粒体呼吸，并鉴定氧化磷酸化途径中的缺陷成分。自我们上次提交以来获得的初步数据表明，TKO 心脏中的细胞 NADPH 水平降低。在目标 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修饰蛋白、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 水平将受到 NAD 激酶的腺病毒表达的调节。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 AMPK 信号通路在 TKO 小鼠中被削弱。目标 3 是确定 TKO 小鼠中 AMPK 信号减弱与线粒体功能受损之间的联系。将剖析 AMPK 调节途径，以确定 Txnip 消融如何导致 AMPK 激活受损。组成型活性 AMPK 将在 TKO 成纤维细胞中表达，以测试正确的 AMPK 信号传导是否可以挽救呼吸缺陷表型。目标 4 是确定 Txnip 如何调节线粒体功能。利用 TKO 成纤维细胞中 Txnip 野生型和各种突变的靶向表达，我们将确定 Txnip 的亚细胞作用位点及其调节线粒体氧化所需的基本功能特征。此外，蛋白质组学方法将用于识别与 Txnip 相互作用的伙伴。这种综合方法将为 Txnip 如何调节线粒体功能及其与代谢调节的联系提供基本的新知识。公共健康相关性：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 调节心肌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的燃料代谢与肥胖、糖尿病和心血管疾病的发生有关。这项拟议研究的结果将提供可能有助于更好地预防和/或治疗人类糖尿病和心血管疾病的基本信息。