Beta-Oxidation and Susceptibility to Fatty Liver Disease

β-氧化和对脂肪肝疾病的易感性

• 批准号: 7484072
• 负责人: JAMAL A IBDAH
• 金额: $ 26.25万
• 依托单位: UNIVERSITY OF MISSOURI-COLUMBIA
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7484072
• 关键词: Acids; Affect; Age; Aging; Cessation of life; Cirrhosis; Data; Defect; Development; Euglycemic Clamping; Fatty Acids; Fatty Liver; Gene Proteins; Generations; Genes; Glucose Clamp; Goals; Hepatic; Hepatocyte; Individual; Inflammation; Inflammatory; Inflammatory Response; Injury; Injury to Liver; Insulin Receptor; Insulin Resistance; Liver; Liver diseases; Measurement; Measures; Mitochondria; Mitochondrial Proteins; Modeling; Molecular Profiling; Multienzyme Complexes; Mus; Muscle; NF-kappaB-inducing kinase; Natural Immunity; Neonatal; Nonesterified Fatty Acids; Numbers; Oxidative Stress; Pathogenesis; Pathway interactions; Patients; Peripheral; Phosphatidylinositols; Phosphorylation; Phosphotransferases; Population; Predisposition; Prevention; Protein Overexpression; Proteins; Reactive Oxygen Species; Relative (related person); Research Personnel; Role; Salicylic Acid; Salicylic Acids; Signaling Molecule; Superoxide Dismutase; Superoxides; Testing; Tissues; Transgenic Mice; Transgenic Organisms; Wild Type Mouse; basal insulin; cytokine; fatty acid oxidation; glucose production; glucose uptake; human SOD2 protein; inhibitor/antagonist; insulin receptor serine kinase; kinase inhibitor; long chain fatty acid; mouse model; non-alcoholic fatty liver; nonalcoholic steatohepatitis; oxidation; prevent; programs; tempol

DESCRIPTION (provided by applicant): Nonalcoholic fatty liver disease (NAFLD) is considered the most common form of liver disease, yet its underlying pathogenesis is poorly understood. Evidence suggests that pathogenesis of NAFLD involves increased levels of free fatty acids, activation of innate immunity genes, and insulin resistance. Although mitochondrial beta-oxidation is the major pathway for oxidation of fatty acids, its role in the pathogenesis of NAFLD remains unknown. We generated a mouse model for mitochondrial trifunctional protein (MTP) that catalyzes the last 3 steps in long chain beta-oxidation. Homozygous mice suffer neonatal death. Our preliminary data document that aging heterozygous mice develop hepatic steatosis associated with oxidative stress and insulin resistance. This proposal uses this murine model to investigate mechanisms underlying NAFLD. Our central hypothesis is that heterozygosity for MTP causes insulin resistance and liver injury associated with hepatic steatosis by increasing cellular oxidative stress. We propose studies towards the following specific aims: 1) To test that heterozygosity for an MTP defect results in an age-associated steatosis with superoxide overproduction leading to activation of the inhibitor KB kinase (IKK), insulin resistance, and liver injury, and to test that prevention of oxidative stress prevents both insulin resistance and hepatic injury in the heterozygous mice. Studies will be conducted to determine the temporal relationship between oxidative stress and hepatic steatosis/injury, insulin resistance, and IKK. We also propose interventional studies to prevent oxidative stress by either scavenging superoxide species using Tempol or by crossing our MTP heterozygous mice to transgenic mice overexpressing superoxide dismutases. 2. To test that activation of IKK causes a) NFkB activation leading to a low-grade inflammation and hepatic injury and b) impaired IRS- dependent activation of the Principal Investigator3K-Akt pathway leading to insulin resistance in mice heterozygous for an MTP defect and to test that inhibition of IKK reverses insulin resistance and hepatic injury. For this, we will measure the content and activation status of IKK and NFkB in both liver and muscle and assess the expression profile of proinflammatory cytokines in liver. We also propose to measure basal and insulin- stimulated contents and phosphorylation/activation status of Akt and the upstream signaling molecules Principal Investigator3K and IRS-1/2 in both liver and muscle. The relative contribution of hepatic and peripheral insulin resistance to whole body insulin resistance will be assessed using hyperinsulinemic-euglycemic clamp. To test the causative relationship between IKK, insulin resistance, and hepatic inflammatory response, mice will be treated with acetyl salicylic acid (ASA), a known IKK inhibitor and then NFkB activation, hepatic inflammation, insulin resistance, and activation status of the Principal Investigator3K/Akt pathway will be evaluated.

描述（由申请人提供）：非酒精性脂肪肝病（NAFLD）被认为是最常见的肝病形式，但其潜在的发病机制却知之甚少。有证据表明，NAFLD 的发病机制涉及游离脂肪酸水平升高、先天免疫基因激活和胰岛素抵抗。尽管线粒体β-氧化是脂肪酸氧化的主要途径，但其在NAFLD发病机制中的作用仍不清楚。我们构建了线粒体三功能蛋白 (MTP) 的小鼠模型，该蛋白催化长链 β-氧化的最后 3 个步骤。纯合子小鼠在新生时就会死亡。我们的初步数据表明，衰老的杂合小鼠会出现与氧化应激和胰岛素抵抗相关的肝脂肪变性。该提案使用该小鼠模型来研究 NAFLD 的潜在机制。我们的中心假设是，MTP 杂合性通过增加细胞氧化应激，导致胰岛素抵抗和与肝脂肪变性相关的肝损伤。我们建议针对以下具体目标进行研究：1) 测试 MTP 缺陷的杂合性会导致年龄相关的脂肪变性，并伴有超氧化物过量产生，从而导致抑制剂 KB 激酶 (IKK) 激活、胰岛素抵抗和肝损伤，并测试表明，预防氧化应激可预防杂合小鼠的胰岛素抵抗和肝损伤。将进行研究以确定氧化应激与肝脂肪变性/损伤、胰岛素抵抗和 IKK 之间的时间关系。我们还提出了通过使用 Tempol 清除超氧化物物质或通过将我们的 MTP 杂合小鼠与过度表达超氧化物歧化酶的转基因小鼠杂交来预防氧化应激的介入研究。 2. 测试 IKK 的激活会导致 a) NFkB 激活导致低度炎症和肝损伤，b) 主要研究者 3K-Akt 通路的 IRS 依赖性激活受损，导致 MTP 缺陷杂合子小鼠的胰岛素抵抗，以及测试抑制 IKK 可逆转胰岛素抵抗和肝损伤。为此，我们将测量肝脏和肌肉中 IKK 和 NFkB 的含量和激活状态，并评估肝脏中促炎细胞因子的表达谱。我们还建议测量肝脏和肌肉中Akt 和上游信号分子Principal Investigator3K 和IRS-1/2 的基础含量和胰岛素刺激含量以及磷酸化/激活状态。将使用高胰岛素正常血糖钳夹评估肝脏和外周胰岛素抵抗对全身胰岛素抵抗的相对贡献。为了测试 IKK、胰岛素抵抗和肝脏炎症反应之间的因果关系，将用乙酰水杨酸 (ASA)（一种已知的 IKK 抑制剂）治疗小鼠，然后对 NFkB 激活、肝脏炎症、胰岛素抵抗和主要研究者 3K 的激活状态进行治疗/Akt 途径将被评估。