Ketone Body Metabolism and Integrated Metabolic Homeostasis

 描述（由申请人提供）：与肥胖流行病密切相关的非酒精性脂肪性肝病（NAFLD）疾病谱，包括非酒精性脂肪性肝炎（NASH），在美国所有成年人中的患病率接近30%。NAFLD显著增加了发展2型糖尿病和心血管疾病的风险，其自然史受到基因组和环境输入的严重影响，这些因素尚未完全了解。特别是，线粒体代谢的作用，它管理的氧化“处置”的脂肪，只有部分特点。线粒体酮体生成（生酮）通常被视为一种被动的代谢溢流管道，当碳水化合物和胰岛素供应不足时，β-氧化产物通过该管道， 已知的反馈交织途径，包括克雷布斯（三羧酸，TCA）循环，葡萄糖的生产，和脂质代谢。相反，我们的初步数据表明：（i）肝脏生酮能力直接影响肝脏中的这些代谢途径，即使在富含碳水化合物的进食状态下;（ii）与1型糖尿病不同，NAFLD/NASH和胰岛素抵抗是生酮相对未充分利用的状态，和（iii）单独的遗传诱导的生酮不足倾向于增加的肝脂肪变性，肝细胞损伤，和。我们的初步数据共同支持中心假设，即（i）生酮不是被动溢出途径，而是肝脏和综合生理稳态中的动态节点，（ii）谨慎的生酮增加可以缓解NAFLD/NASH和肝脏葡萄糖代谢紊乱，这将通过两个特定目的进行测试。在目标1中，我们将证明肝酮生成控制肝脏代谢稳态和线粒体功能的机制。我们将使用生酮功能不全的小鼠模型、高分辨率核磁共振（NMR）光谱和液相色谱法结合高质量准确度质谱（LC/MS）指导的代谢组学，在用稳定同位素标记的代谢燃料治疗的小鼠中进行研究。靶向和非靶向计算代谢组学和脂质组学方法将被用来全面量化生酮作用调节综合细胞器代谢稳态的生化空间。遗传和药理学的激发将揭示肝细胞代谢、线粒体功能和NAFLD/NASH发病机制之间的机制联系。在目标2中，我们将证明增加肝酮生成改善NAFLD发病机制和肝脏葡萄糖代谢紊乱。将在体内脂肪肝损伤小鼠模型中表达命运决定性生酮线粒体酶3-羟甲基戊二酰-CoA合酶的野生型或组成性高活性突变形式。将通过NMR光谱、综合LC/MS代谢组学和系统生理学方法定量不同肝酮生成对肝损伤和炎症、脂肪酸氧化、从头脂肪生成和葡萄糖生成的影响。

 DESCRIPTION (provided by applicant): Tightly linked to the obesity epidemic, disorders along the nonalcoholic fatty liver disease (NAFLD) spectrum, including nonalcoholic steatohepatitis (NASH), occur with nearly 30% prevalence among all adults in the United States. NAFLD dramatically increases the risks of developing type 2 diabetes and cardiovascular disease, and its natural history is heavily influenced by genomic and environmental inputs that are still incompletely understood. In particular, the role of mitochondrial metabolism, which governs the oxidative `disposal' of fats, has only been partially characterized. Mitochondrial ketone body generation (ketogenesis) is generally viewed as a passive metabolic overflow conduit through which products of β-oxidation pass when carbohydrates and insulin are in short supply, with little known feedback on interwoven pathways including the Krebs (tricarboxylic acid, TCA) cycle, glucose production, and lipid metabolism. On the contrary, our preliminary data indicate that (i) hepatic ketogenic capacity directly influences these metabolic pathways in liver, even in the carbohydrate-laden fed state; (ii) in contradistinction to type 1 diabetes, NAFLD/NASH and insulin resistance are states in which ketogenesis is relatively underutilized, and (iii) geneticaly-induced ketogenic insufficiency alone predisposes to increased hepatic steatosis, hepatocellular injury, and glycemia. Together our preliminary data support the central hypotheses that (i) ketogenesis is not a passive overflow pathway but rather a dynamic node in hepatic and integrated physiological homeostasis, and (ii) prudent ketogenic augmentation can mitigate NAFLD/NASH and disordered hepatic glucose metabolism, which will be tested through two Specific Aims. In Aim 1, we will demonstrate the mechanisms by which hepatic ketogenesis governs hepatic metabolic homeostasis and mitochondrial function. We will use mouse models of ketogenic insufficiency, high resolution nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography coupled to high mass accuracy mass spectrometry (LC/MS)-guided metabolomics in mice treated with stable isotopically-labeled metabolic fuels. Targeted and untargeted computational metabolomics and lipidomics approaches will be leveraged to comprehensively quantify the biochemical space through which ketogenesis regulates integrated organelle metabolic homeostasis. Genetic and pharmacological provocations will reveal mechanistic connections among hepatocyte metabolism, mitochondrial function, and NAFLD/NASH pathogenesis. In Aim 2, we will demonstrate that increasing hepatic ketogenesis ameliorates NAFLD pathogenesis and disordered hepatic glucose metabolism. Wild-type or constitutively hyperactive mutated versions of the fate-committing ketogenic mitochondrial enzyme 3-hydroxymethylglutaryl-CoA synthase will be expressed in mouse models of fatty liver injury in vivo. The effects of varying hepatic ketogenesis on hepatic injury and inflammation, fatty acid oxidation, de novo lipogenesis, and glucose production will be quantified by NMR spectroscopy, comprehensive LC/MS metabolomics, and systems physiological approaches.