Nutrient Overload, Insulin Resistance, and Hepatic Mitochondrial Dysfunction

摘要 来自动物研究的有力证据和来自人类成像研究的间接数据表明， 肝线粒体活性在非酒精性脂肪性肝炎病理生理学中的关键作用 (纳什)。我们在NASH患者中的初步数据表明，有两种缓解过度的治疗方法 营养应激、热量限制(CR)和运动训练(EX)改善肝脏组织学。我们最近 在啮齿动物模型中的研究证实，EX对肝脏组织学的治疗作用是中介的 通过增加肝脏线粒体的含量和功能。目前还不清楚是否有类似的 这种治疗对肝脏线粒体的有益影响发生在人类身上。的中心假设 该项目是营养过载导致肝脏线粒体功能障碍，线粒体功能障碍是 Nash病理，且这种过载的改善将导致线粒体的更高效率 生物能量学和改进的肝脏组织学。为了检验这些假设，一种联合治疗方案 60例NASH患者将使用CR和EX降低肝内三酰甘油(IHTG)。基线 治疗组中9个月的肝脏活检将与30名患者的重复活检进行比较。 正在接受规范的临床管理。我们将完成以下具体目标。SA1将利用 来自NASH患者的肝脏活检样本，以及在减肥手术中获得的肝脏样本，以 确定较晚期肝病患者的肝脏线粒体是否在体外和 体外，表现出较差的能量生成(质量控制)、生物发生和有丝分裂；SA2将分离 9个月后再次检测肝脏线粒体IHTG缺失是否与改善有关 从基因表达、酶水平评估线粒体功能、生物发生和质量控制 和脂肪酸氧化。SA3将在以下情况下测量受试者的全身葡萄糖和脂肪酸流量- 积极治疗(CR EX)和标准护理。措施将在基线和9点之后进行 月，以及用于量化外周养分处置和减少的数学模型 以比较其对线粒体功能、纤维化的影响，并通过活组织检查- 通过组织学评估确定NASH活性评分。总而言之，这些研究将 通过以下方面的发现显著促进了NAFLD领域的发展：1)过度 营养应激导致肝脏线粒体功能降低2)两者之间的关系 NASH的线粒体活性和组织学特征。重要的是，这项工作将发挥持久的作用 通过确定人类肝脏线粒体功能障碍是否可逆对该领域的影响。

Abstract Strong evidence from animal studies and indirect data from human imaging studies, implicate reduced liver mitochondrial activity as a key event in the pathophysiology of nonalcoholic steatohepatitis (NASH). Our preliminary data in NASH patients demonstrate that two treatments that relieve excess nutrient stress, caloric restriction (CR) and exercise training (EX), improve liver histology. Our recent studies in a rodent model established that the therapeutic effect of EX on liver histology is mediated through increases in both hepatic mitochondrial content and function. It is unknown whether a similar beneficial effect of such treatment on liver mitochondria occurs in humans. The central hypotheses of this project is that nutrient overload results in hepatic mitochondrial dysfunction, a key mediator of NASH pathology, and that amelioration of this overload will result in greater efficiency of mitochondrial bioenergetics and improved liver histology. To test these hypotheses, a treatment regimen combining CR and EX will be used to reduce intrahepatic triacylglycerols (IHTG) in 60 NASH patients. Baseline and 9-month liver biopsies in the treated group will be compared to repeat biopsies from 30 patients undergoing standard clinical management. We will complete the following specific aims. SA1 will utilize liver biopsy samples from patients with NASH, and liver samples obtained during bariatric surgery, to determine whether patients with more advanced liver disease have liver mitochondria that, in vitro and ex vivo, exhibit poor energy generation (quality control), biogenesis, and mitophagy; SA2 will isolate hepatic mitochondria again after 9-months to test whether loss of IHTG is associated with improved mitochondrial function, biogenesis and quality control as assessed by gene expression, enzyme levels and fatty acid oxidation. SA3 will measure whole body glucose and fatty acid flux in subjects under- going active treatment (CR+EX) and standard care. Measures will be made at baseline and after 9 months, and mathematical modeling used to quantitate peripheral nutrient disposal and the reduction in liver nutrient burden to compare its influence on mitochondrial function, fibrosis, and by the biopsy- determined NASH activity score using histological assessment. In summary, these studies will significantly advance the field of NAFLD through discoveries of 1) the mechanisms by which excess nutrient stress contributes to reduced hepatic mitochondrial function and 2) the relationships between mitochondrial activity and the histologic features of NASH. Importantly, this work will exert a sustained influence on the field by determining whether hepatic mitochondrial dysfunction is reversible in humans.