PPARa and related nuclear receptors in non-alcoholic fatty liver disease

项目摘要/摘要 肥胖和2型糖尿病的流行增加了相关心脏代谢性疾病的患病率 包括血清甘油三酯(TGS)升高和非酒精性脂肪性肝病(NAFLD)。有复活的 对靶向肝核受体PPARα的药物感兴趣。这种贝特类药物已经用于 高甘油三酯血症，并有新的认识，TGS独立地导致动脉粥样硬化的心血管 降低TGS可降低风险的疾病。此外，PPAR激动剂可能是首批药物之一 批准用于NAFLD。NAFLD的不良临床结局，如肝硬变衰竭，肝细胞癌， 和肝脏相关的死亡都与肝纤维化密切相关。我们在NAFLD小鼠模型中的初步数据 意外显示PPARα缺乏和PPARα激动剂治疗均未能改变肝脏脂肪变性， 但显著影响纤维化(分别增加和减少纤维化)。PPARα在肝细胞中的结合功能 调节DNA，影响脂代谢关键基因的表达。相关的核受体HNF4α是 不是药物靶点，但调节相似的基因和绑定相似的调节DNA。我们假设这种相互作用 PPARα和HNF4DNA结合的α影响肝细胞基因调控，与其发病机制有关 非酒精性脂肪肝的治疗。我们的实验探索全基因组的核受体结合部位和基因调控， 在正常和脂肪变性的肝脏中，基本和对药物的反应。目标1定义了PPARα的相互依赖关系 和HNF4α在肝脏基因调控中的作用，使用其中一种或两种都缺乏的小鼠模型。Aim 2扩展了这些研究 在小鼠模型和人类生物样本中，PPARα和HNF4α对非酒精性脂肪肝的作用。AIM 3部署了功能强大的 研究序列特异性α结合中PPARDNA和HNF4DNA相互作用的遗传学工具。通过比较 近交系小鼠品系，影响结合基序的自然多态将揭示选择性和 常见的PPARα和HNF4α结合。在人类肝脏样本中，我们将检验这样一个假设，即非 编码PPARα/HNF4α基因组结合位点的遗传变异是甘油三酯人群差异的基础 水平、非酒精性脂肪肝及其对PPARα激动剂的反应。除了这种潜在的临床相关性，这些 研究使用创新的基因组和遗传学方法来解决生物学中尚未回答的关键问题 PPARα，包括其与相关核受体的相互作用。

PROJECT SUMMARY/ABSTRACT The epidemic of obesity and type 2 diabetes has increased prevalence of associated cardiometabolic diseases including elevated serum triglycerides (TGs) and non-alcoholic fatty liver disease (NAFLD). There is resurgent interest in drugs targeting the hepatic nuclear receptor PPARα. Such fibrate drugs are already used in hypertriglyceridemia, and there is new appreciation that TGs independently cause atherosclerotic cardiovascular disease such that lowering TGs reduces risk. Furthermore, PPAR agonists may be among the first drugs approved for NAFLD. Adverse clinical outcomes in NAFLD like cirrhotic liver failure, hepatocellular carcinoma, and liver-related death are all closely linked to hepatic fibrosis. Our preliminary data in a NAFLD mouse model show unexpectedly that PPARα deficiency and PPARα agonist treatment both fail to change hepatic steatosis, but markedly affect fibrosis (increasing and decreasing it, respectively). PPARα functions in hepatocytes to bind regulatory DNA and affect expression of key genes in lipid metabolism. The related nuclear receptor HNF4α is not a drug target, yet regulates similar genes and binds similar regulatory DNA. We hypothesize that the interplay of PPARα and HNF4α in DNA binding affects hepatocyte gene regulation, relevant to the pathogenesis and therapeutics of NAFLD. Our experiments probe genome-wide nuclear receptor binding sites and gene regulation, in normal and steatotic livers, basally and in response to drugs. Aim 1 defines the interdependency of PPARα and HNF4α in liver gene regulation, using mouse models deficient in either or both. Aim 2 extends these studies of PPARα and HNF4α to NAFLD, in both mouse models and human biospecimens. Aim 3 deploys the powerful tools of genetics to characterize PPARα and HNF4α interplay in sequence-specific DNA binding. By comparing inbred mouse strains, natural polymorphisms affecting binding motifs will reveal mechanisms for selective and common DNA binding by PPARα and HNF4α. In human liver samples, we will test the hypothesis that that non- coding genetic variants in PPARα/HNF4α genomic binding sites underlie some differences among people in TG levels, NAFLD, and response of these to PPARα agonist drugs. Beyond this potential clinical relevance, these studies use innovative genomic and genetic approaches to address key unanswered questions in the biology of PPARα, including its interplay with related nuclear receptors.