Understanding the metabolic pathology of pediatric obesity and NAFLD

项目摘要 非酒精性脂肪性肝病（NAFLD）是目前世界上最常见的肝病， 40%的肥胖青年和高达10%的一般儿科人群。NAFLD的一些特征在以下方面相似： 儿童和成人，但纤维化和炎症更常见于汇管区，并发生在早期， 儿童NAFLD患者多于成人。这预示着在早期肝病会迅速进展为终末期肝病。 成年对于大多数患有NAFLD的儿童，驱动NAFLD起源和快速进展的机制 疾病仍然未知。因此，有一个关键的，未得到满足的需要，研究具体的基本模式， 肝脏中的代谢和分子变化是儿童特有的发育和进展的基础。 NAFLD。肝脏新生脂肪生成（DNL）是NAFLD成人肝脂肪变性的主要驱动因素， 胰岛素抵抗会加速这种变化。此外，通过TCA循环流向异源生殖（GNG）的通量是 增加，促进线粒体损伤，肝损伤和进展为非酒精性脂肪性肝炎 （NASH）通过氧化应激。DNL和GNG发生率升高是否以及如何促进儿童NAFLD 不明microRNA（miRNA）是动物模型中DNL和GNG的关键调节因子， 在成人NAFLD患者中存在潜在的生物标志物，但在儿科NAFLD中研究不足。我们的初步数据 显示与对照相比，青少年NAFLD患者的血清miR-122和miR-192增加。 然而，儿童NAFLD中循环miRNAs的完整谱现在有可能开发出非- 儿童侵入性生物标志物面板。我们将结合联合收割机新型示踪剂、RNA和组织成像方法， 区分儿科NAFLD临床显著阶段之间的代谢和分子变化。我们 假设DNL和GNG比率增加是NAFLD进展的原因途径， 在儿童中，miR-122和miR-192驱动脂肪变性发展为NASH，并且空间异质性 在汇管区基因表达、纤维化和氧化活性是导致 孩子在目标1中，使用口服示踪剂方法测量NAFLD青少年的DNL和GNG， 在健康的同龄人中，他们被归类为肥胖或正常体重。在目标2中，在血清中的miRNA分析和 肝脏将决定它们作为NAFLD生物标志物和疾病介质的作用。在目标3中，我们将执行 肝活检的高分辨率分子成像以确定纤维化的丰度和分布， 能量学和成绩单这项研究将首次确定GNG和DNL是否驱动了 儿童NAFLD的发病机制，miRNA是否是诊断NAFLD的循环生物标志物，以及 肝基因表达、氧化代谢和胶原形成的门脉周围分布是否 儿童NAFLD患者特有的与更差的代谢评估相关。总的来说， 利用独特的工具，我们将确定亚细胞病因，早期机制，并可能 NAFLD儿童特有的可改变的途径和生物标志物。

PROJECT SUMMARY Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease worldwide and affects nearly 40% of obese youth and up to 10% of the general pediatric population. Some features of NAFLD are similar in children and adults, yet fibrosis and inflammation are more common in the portal zone and occur earlier in pediatric NAFLD patients than adults. This portends a rapid progression to end-stage liver disease in early adulthood. For the majority of children with NAFLD, mechanisms driving the origin and rapid progression of disease remain unknown. Thus, there is a critical, unmet need to study the specific underlying patterns of metabolic and molecular changes in the liver underlying development and progression unique to children with NAFLD. Hepatic de novo lipogenesis (DNL) is a primary driver of hepatic steatosis in adults with NAFLD and is accelerated by insulin resistance. Additionally, flux through the TCA cycle toward gluconeogenesis (GNG) is increased, which promotes mitochondrial damage, liver injury, and progression to nonalcoholic steatohepatitis (NASH) through oxidative stress. Whether and how elevated rates of DNL and GNG advance pediatric NAFLD is unknown. MicroRNAs (miRNA) are critical regulators of DNL and GNG in animal models and emerging as potential biomarkers in adults with NAFLD but are understudied in pediatric NAFLD. Our preliminary data show that serum miR-122 and miR-192 are increased in adolescent NAFLD patients compared to controls. However, a complete profile of circulating miRNAs in pediatric NAFLD is now possible to develop a non- invasive biomarker panel for children. We will combine novel tracer, RNA, and tissue imaging methods to discriminate the metabolic and molecular changes among clinically-significant stages of pediatric NAFLD. We hypothesize that increased rates of DNL and GNG are causative pathways for progression from NAFLD in children, that miR-122 and miR-192 drive the development of steatosis to NASH, and that spatial heterogeneity in portal zone gene expression, fibrosis, and oxidative activity are responsible for the unique histopathology in children. In aim 1, an oral tracer approach is used to measure DNL and GNG in adolescents with NAFLD and in healthy peers who are classified as either obese or normal weight. In aim 2, miRNA analyses in serum and liver will determine their role as biomarkers for NAFLD and mediators of the disease. In aim 3, we will perform high resolution molecular imaging of liver biopsies to determine the abundance and distribution of fibrosis, energetics, and transcripts. This study will establish for the first time whether GNG and DNL drive the pathogenesis of pediatric NAFLD, whether miRNAs are circulating biomarkers for diagnosis of NAFLD, and whether the periportal distribution of liver gene expression, oxidative metabolism, and collagen formation unique to pediatric NAFLD patients are associated with worse metabolic assessments. Collectively, by taking advantage of unique tools, we will identify the sub-cellular etiology, early mechanisms, and potentially modifiable pathways and biomarkers unique to children with NAFLD.