Nonalcoholic Steatohepatitis: Natural History, Pathogenesis and Therapy

非酒精性脂肪性肝炎：自然史、发病机制和治疗

• 批准号: 10697805
• 负责人: Yaron Rotman
• 金额: $ 188.53万
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10697805
• 关键词: 4 hydroxynonenal; Adult; Affect; Agonist; Alleles; Animal Model; Antioxidants; Breath Tests; Carbohydrates; Cell model; Cirrhosis; Clinical; Clinical Trials; Code; Devices; Diglycerides; Disease; Drug Industry; Eating; Effectiveness; Energy Metabolism; Enrollment; Enzymes; Etiology; Fatty Acids; Fatty Liver; Fatty acid glycerol esters; Fibrosis; Food Energy; Functional disorder; GLP-I receptor; Genes; Genetic study; Genotype; Hepatic; Hepatocyte; Histologic; Human; Hydroxysteroids; In Vitro; Individual; Inflammation; Ingestion; Injury; Knockout Mice; Label; Lead; Lipids; Liquid substance; Liver; Liver diseases; Malignant neoplasm of liver; Metabolic; Metabolism; Methods; Modality; Morbidity - disease rate; Natural History; Nutrient; Oral; Oxidative Stress; Oxidoreductase; Pathogenesis; Pathway interactions; Patients; Phenotype; Physiological; Physiology; Plasma; Play; Population; Proteins; RNA Splicing; Retinoids; Role; Sampling; Severities; Single Nucleotide Polymorphism; Site; Structure; Study models; Tertiary Protein Structure; Time; United States; United States National Institutes of Health; Up-Regulation; Vitamin E; adduct; cell injury; clinical center; clinical predictors; cohort; density; effective therapy; end stage liver disease; experimental study; fatty acid oxidation; genetic association; genetic variant; genome wide association study; healthy volunteer; high risk; human subject; improved; in vivo; insulin signaling; interest; intrahepatic; lipid biosynthesis; lipidome; lipidomics; liver injury; liver transplantation; mortality; mouse model; new therapeutic target; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; novel therapeutics; particle; pediatric patients; randomized placebo controlled trial; response; therapeutic target; transcriptomics

Nonalcoholic fatty liver disease (NAFLD) is marked by accumulation of fat in liver cells with accompanying inflammation and variable degrees of cell injury and fibrosis. When cell injury and fibrosis are present, the disease has a potential to progress and is referred to as nonalcoholic steatohepatitis (NASH), which can lead to cirrhosis, liver cancer, morbidity and mortality. The etiology of NASH is not clear nor is there an approved treatment modality for it. NAFLD has become an extremely common disorder, estimated to affect up to 30% of individuals in the US. Unfortunately, it commonly goes unrecognized, as demonstrated by our recent finding that over a 5-year period, 28% of subjects enrolled as healthy volunteers to studies at the NIH Clinical Center were likely to have underlying NAFLD. As such, there is a clear need to understand the pathophysiology of the disease and its treatment. Our focus on NAFLD is three-fold: first, we aim to identify and characterize key genes that play a role in the pathogenesis of NAFLD through the use of genetic studies and cell- or animal models and identify their suitability as therapeutic target. Second, we aim to understand the physiology of fat accumulation and injury in the liver, especially as it relates to handling of oral caloric load. Third, we hope to identify and refine effective treatments for the disorder. Genome wide association (GWA) studies identified single nucleotide polymorphisms (SNPs) that are associated with increased hepatic fat or elevated liver enzymes, presumably reflecting nonalcoholic fatty liver disease (NAFLD). We initiated a study to investigate whether these SNPs are associated with histological severity in a large cohort of NAFLD patients. We confirmed the association of the rs738409G allele in the PNPLA3 gene with steatosis and were first to describe its association with histological severity. In pediatric patients, the high-risk rs738409G allele was associated with an earlier presentation of disease. Similarly, we discovered an association of several SNPs near or in the gene for hydroxysteroid (17) dehydrogenase 13 (HSD17B13) with histological features of NAFLD. In-depth genotyping of the gene region demonstrated associations of coding and splice-site SNPs in the gene with NAFLD, confirming a possible role for the protein in the pathogenesis of NASH. HSD17B13 is an enzyme that we found to be predominantly expressed in the liver and to colocalize with lipid droplets. We identified that HSD17B13 is involved in retinoid metabolism and that genetic variants that lead to loss of its enzymatic function are genetically associated with decreased severity of NAFLD. We further characterized the structure of the protein and the domains in it that are key to its function. These findings generated remarkable interest in the pharmaceutical industry and several HSD17B13 inactivating agents are being studied in human subjects as potential therapies for NASH. Despite the promising genetic association and pharma interest, the actual physiological role of HSD17B13 in vivo and the mechanism by which its inactivation leads to protection from NASH-associated injury are still unknown. To improve our understanding of HSD17B13s role, we established an Hsd17b13 knock-out mouse model and are currently studying it under multiple condition, aiming to replicate the human phenotype. Our mouse and cell models allow us to pinpoint the mechanism by which loss of HSD17B13 protects the liver from injury, as well as its association with other metabolic features. As NAFLD is intricately related to food intake and energy metabolism, we are undertaking clinical trials to evaluate the handling and fate of nutrients by the fatty liver. We used the BreathID real-time breath test device in combination with a labeled fatty acid to demonstrate a decrease in the rate of fatty acid oxidation in subjects with NAFLD compared to controls. We recently studied NAFLD subjects after ingestion of a liquid mixed meal. We collected plasma samples at multiple time points and utilized a lipidomic approach and parallel mouse models to identify an increase in packaging of hepatic diacylglycerols (DAG) into very low density lipprotein (VLDL) particles after a meal, that is unique to NAFLD. Finally, we are currently performing an additional study, where liver samples from subjects with NAFLD are obtained before and after an oral carbohydrate load aimed to elucidate the hepatic transcriptomic and lipidomic response as well as effects on intra-hepatic insulin signaling. Vitamin E has been shown in a randomized placebo-controlled trials to be an effective therapy for NASH. Curiously, treatment with vitamin E resulted not only in a decrease in injury (thought to reflect its antioxidant effect) but was also associated with a decrease in liver fat, through an unknown mechanism. We combined a clinical mechanistic trial with in vitro experiments to determine the mechanism of action of vitamin E. We identified a key cellular pathway by which oxidative stress (a common feature of NAFLD) increases liver fat through upregulation of hepatic de novo lipogenesis and confirmed that vitamin E blocks the activation of this pathway through its antioxidant activity. We were able to establish an automated method to quantify hepatic 4-hydroxynonenal (4-HNE) adducts, a marker of oxidative stress-induced damage, and confirmed its applicability with samples from the vitamin E trial. In a current trial, subjects with NAFLD are treated with semaglutide, a glucagon like peptide 1 (GLP-1) receptor agonist with effectiveness against NASH previously shown. This study aims to elucidate the mechanism of action of semaglutide in treating NASH, its effects on the liver lipidome and identify early predictors of clinical response.

非酒精性脂肪肝病（NAFLD）的标志是肝细胞中脂肪的积累，伴有炎症和细胞损伤和纤维化的变化程度。当存在细胞损伤和纤维化时，该疾病可能会进展，并被称为非酒精性脂肪性肝炎（NASH），这可能导致肝硬化，肝癌，发病率和死亡率。纳什的病因尚不清楚，也没有批准的治疗方式。 NAFLD已成为一种极为普遍的疾病，估计会影响美国30％的人。不幸的是，我们最近的发现表明，在5年的时间里，有28％的受试者成为NIH临床中心研究的健康志愿者可能有28％的受试者可能在NAFLD的基础。因此，显然需要了解该疾病的病理生理及其治疗。 我们对NAFLD的关注是三个方面：首先，我们旨在通过使用遗传研究和细胞或动物模型来识别和表征在NAFLD在NAFLD发挥作用的关键基因，并确定其适合性作为治疗靶点。其次，我们旨在了解肝脏脂肪积累和损伤的生理，尤其是与口服热量负荷处理有关的生理。第三，我们希望识别并完善对该疾病的有效治疗方法。 基因组广泛的缔合（GWA）研究确定了与肝脂肪升高或肝脏升高有关的单核苷酸多态性（SNP），大概反映了非酒精性脂肪肝病（NAFLD）。我们开始了一项研究，以研究这些SNP是否与大量NAFLD患者队列中的组织学严重程度相关。我们证实了PNPLA3基因中rs738409g等位基因与脂肪变性的关联，并首先描述了其与组织学严重程度的关联。在小儿患者中，高危卢比的等位基因与较早的疾病相关。 同样，我们发现了羟基固醇附近或基因中的几个SNP（17）脱氢酶13（HSD17B13）与NAFLD的组织学特征的关联。基因区域的深入基因分型表明，基因中的编码和剪接位点SNP与NAFLD的关联，证实了该蛋白质在NASH发病机理中的可能作用。 HSD17B13是一种酶，我们发现它主要在肝脏中表达并与脂质液滴共定位。我们确定HSD17B13参与性类维生素性代谢，并且导致其酶促功能丧失的遗传变异与NAFLD的严重程度降低相关。我们进一步表征了蛋白质及其域的结构，这些结构是其功能的关键。这些发现对制药行业产生了巨大的兴趣，正在研究人类受试者作为NASH的潜在疗法中的几种HSD17B13灭活剂。 尽管有希望的遗传关联和药物兴趣，但HSD17B13在体内的实际生理作用以及其失活导致保护NASH相关损伤的机制仍然未知。为了提高我们对HSD17B13S角色的理解，我们建立了HSD17B13敲除小鼠模型，目前正在多种条件下研究它，旨在复制人类表型。我们的小鼠和细胞模型使我们能够指出HSD17B13损失可保护肝脏免受损伤的机制，以及与其他代谢特征的关联。 由于NAFLD与食物摄入和能量代谢相关，因此我们正在进行临床试验，以评估脂肪肝脏的营养的处理和命运。与对照组相比，我们使用了呼气实时呼气测试装置与标记的脂肪酸结合使用，以证明NAFLD受试者的脂肪酸氧化速率降低。摄入液体混合餐后，我们最近研究了NAFLD受试者。我们在多个时间点收集了血浆样品，并利用了脂质组方法和平行小鼠模型来确定肝二酰基甘油（DAG）的包装增加到一餐后密度非常低的含氧蛋白（VLDL）颗粒中，这是NAFLD所独有的。最后，我们目前正在进行一项额外的研究，其中在口服碳水化合物载荷之前和之后获得了来自NAFLD受试者的肝脏样品，旨在阐明肝转录组和脂肪症反应以及对肝内胰岛素信号的影响。 维生素E在随机的安慰剂对照试验中已显示为NASH的有效疗法。奇怪的是，维生素E的治疗不仅导致损伤减少（被认为反映了其抗氧化作用），而且还通过未知的机制与肝脏脂肪减少有关。我们将一项临床机械试验与体外实验结合在一起，以确定维生素E的作用机理。我们确定了一种关键的细胞途径，通过该途径，氧化应激（NAFLD的一个共同特征）通过上调从头开始脂肪生成而增加肝脏脂肪，并确认维生素E通过其抗氧化剂的活性阻止了这种途径的激活。我们能够建立一种自动化方法来量化肝4-羟基烯醇（4-HNE）加合物，这是氧化应激诱导的损伤的标记，并证实了其适用于维生素E试验中的样品。 在当前的试验中，患有NAFLD的受试者是用半瓜肽（像肽1（GLP-1）受体激动剂这样的胰高血糖素治疗的，对先前显示的NASH有效性。这项研究旨在阐明半氟丁物在治疗NASH，其对肝脂质组的作用并确定临床反应的早期预测指标。