Insulin Regulation of Hepatic Function via Zone-Specific Transcriptional Programs

胰岛素通过区域特异性转录程序调节肝功能

基本信息

批准号：
10396110
负责人：
Sudha B Biddinger
金额：
$ 56.05万
依托单位：
BOSTON CHILDREN'S HOSPITAL
依托单位国家：
美国
项目类别：
财政年份：
2021
资助国家：
美国
起止时间：
2021-05-01 至 2026-04-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10396110
关键词：
Adult Affect Bile Acid Biosynthesis Pathway Bile Acids CYP8B1 gene Cell Nucleus Cells Cholesterol Clinical Clinical Research Data Development Disease Disease Progression Enzymes Epidemic Fluorescent in Situ Hybridization Gene Expression Genes Genetic Transcription Goals Hepatic Hepatocyte Homeostasis Human Hydroxylation Individual Inflammation Inflammatory Insulin Insulin Receptor Insulin Resistance Intervention Knock-out Lead Lipids Liver Liver Failure Liver diseases Malignant neoplasm of liver Measures Mediating Metabolic Mus Pathogenesis Pathway interactions Patients Physiological Population Predisposition Prevention Process Reaction Reporting Repression Resistance development Role Site Societies Study models Techniques Testing Transcriptional Regulation Triglyceride Metabolism Triglycerides base beta catenin bile acid metabolism cell injury effective therapy insulin mediators insulin regulation insulin signaling liver inflammation liver injury mouse model non-alcoholic fatty liver disease nonalcoholic steatohepatitis novel prevent programs response single molecule targeted treatment

项目摘要

Non-alcoholic fatty liver disease (NAFLD) has reached epidemic proportions in our society, and yet our understanding of the pathogenesis of this disorder remains rudimentary 7. Clinical studies show a close correlation between insulin resistance and the development and progression of NAFLD 8,9. To understand mechanistically the changes in triglyceride, cholesterol, and bile acid metabolism that occur with the development of NAFLD, a clear understanding of how insulin regulates these processes is necessary. Until now, studies of insulin action in the liver have been done with the assumption that all hepatocytes are equivalent. This assumption was made out of practicality, as our ability to isolate and analyze different populations of hepatocytes individually was limited. Yet, hepatocytes clearly vary in terms of the metabolic functions they perform, and their susceptibility to different insults 10. For example, the perivenous hepatocytes are the predominant site of bile acid synthesis and the most common site of triglyceride accumulation in NAFLD 11,12. Here, we will determine how insulin modulates gene expression in the perivenous hepatocytes to maintain homeostasis. Our novel, unpublished preliminary data reveal a striking example of zone-specific transcriptional regulation by insulin. We find that insulin suppresses Cyp8b1 only in the perivenous hepatocytes. Cyp8b1 encodes the sole enzyme capable of catalyzing the 12a-hydroxylation of bile acids 13; 12a-hydroxylated bile acids increase hepatic cholesterol and promote the progression to non-alcoholic steatohepatitis (NASH) 14-16. In the absence of insulin, the de-repression of Cyp8b1 in the perivenous hepatocytes is associated with increased 12a- hydroxylated bile acids, increased hepatic cholesterol, and severe inflammation. The fact that NAFLD progression in humans is also associated with an increase in 12a-hydroxylated bile acids and hepatic cholesterol, and the fact that inflammation marks the development of non-alcoholic steatohepatitis, a more severe and progressive form of disease, highlight the importance of studying this pathway 17-19. Based on these and other preliminary data, we hypothesize that insulin modulates the activity of b-catenin, a master transcriptional regulator that is activated only in the perivenous hepatocytes 20, to maintain normal lipid homeostasis and prevent inflammation. To test this hypothesis, we aim to (1) define the insulin-regulated cellular transcriptional programs in the liver using single-nuclei sequencing; and (2) dissect the role of b-catenin in producing the transcriptional and physiological response to insulin. We expect that insulin can reprogram the perivenous hepatocytes by modulating b-catenin driven transcription, and that this is required for normal homeostasis. Such results may ultimately lead to the development of precise interventions that reverse the effects of insulin resistance in the perivenous hepatocytes, preventing NASH.

非酒精性脂肪肝（NAFLD）在我们的社会中已达到流行病的程度，但我们的对这种疾病发病机制的了解仍处于初级阶段 7. 临床研究表明，胰岛素抵抗与 NAFLD 发生和进展之间的相关性 8,9。要了解从机制上讲，随着发育而发生的甘油三酯、胆固醇和胆汁酸代谢的变化对于 NAFLD 来说，有必要清楚地了解胰岛素如何调节这些过程。迄今为止，研究胰岛素在肝脏中的作用是在假设所有肝细胞都是等效的情况下进行的。这假设是出于实用性，因为我们有能力分离和分析不同的肝细胞群个别是有限的。然而，肝细胞在其代谢功能及其代谢功能方面存在明显差异。对不同损伤的敏感性 10. 例如，静脉周围肝细胞是胆汁的主要部位 NAFLD 中酸合成和甘油三酯积累最常见的位点 11,12。在这里，我们将确定胰岛素如何调节静脉周围肝细胞的基因表达以维持体内平衡。我们新颖的、未发表的初步数据揭示了区域特异性转录的一个引人注目的例子通过胰岛素调节。我们发现胰岛素仅在静脉周围肝细胞中抑制 Cyp8b1。 CYP8B1 编码能够催化胆汁酸 12a-羟基化的唯一酶 13； 12a-羟基胆汁酸增加肝脏胆固醇并促进非酒精性脂肪性肝炎 (NASH) 的进展 14-16。在在缺乏胰岛素的情况下，静脉周围肝细胞中 Cyp8b1 的去抑制与 12a- 的增加有关羟基化胆汁酸、肝脏胆固醇增加和严重炎症。 NAFLD 的事实人类的进展也与 12a-羟基胆汁酸和肝脏的增加有关。胆固醇，以及炎症标志着非酒精性脂肪性肝炎的发展这一事实，严重且进行性的疾病，强调了研究该途径的重要性 17-19。基于这些和其他初步数据，我们假设胰岛素调节 β-连环蛋白的活性，β-连环蛋白是仅在静脉周围肝细胞 20 中激活的转录调节因子，以维持正常的脂质体内平衡并预防炎症。为了检验这一假设，我们的目标是 (1) 定义胰岛素调节的细胞使用单核测序在肝脏中进行转录程序； (2) 剖析 β-连环蛋白在产生对胰岛素的转录和生理反应。我们期望胰岛素能够重新编程静脉周围肝细胞通过调节β-连环蛋白驱动的转录，这是正常的必需的体内平衡。这些结果可能最终导致精确干预措施的发展，从而扭转这一局面。胰岛素抵抗对静脉周围肝细胞的影响，预防 NASH。