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

• 批准号: 10210751
• 负责人: Sudha B Biddinger
• 金额: $ 63.25万
• 依托单位: BOSTON CHILDREN'S HOSPITAL
• 依托单位国家: 美国
• 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/10210751
• 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; Injury; 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; mouse model; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; novel; prevent; programs; response; single molecule; targeted treatment

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.

非酒精性脂肪肝疾病（NAFLD）在我们的社会中达到了流行比例，但我们 对这种疾病的发病机理的理解仍然是基本的7。临床研究表明 胰岛素抵抗与NAFLD 8,9的发展和进展之间的相关性。理解 从机械上讲，甘油三酸酯，胆固醇和胆汁酸代谢的变化随发育而发生的 在NAFLD中，需要清楚地了解胰岛素如何调节这些过程。到目前为止，研究 肝脏中的胰岛素作用是通过假设所有肝细胞等效的假设进行的。这 假设是出于实用性而构成的，因为我们分离和分析不同种群的肝细胞的能力 单独有限。然而，肝细胞显然在其执行的代谢功能方面有所不同，他们 对不同侮辱的敏感性10。例如，骨肝细胞是胆汁的主要部位 酸合成和NAFLD 11,12中甘油三酸酯积累的最常见位点。在这里，我们将确定 胰岛素如何调节细胞肝细胞中的基因表达以维持稳态。 我们的小说，未发表的初步数据揭示了一个特定区域转录的引人注目的例子 胰岛素调节。我们发现，胰岛素仅在细胞肝细胞中抑制CYP8B1。 CYP8B1 编码能够催化胆汁酸的12a-羟基化13的唯一酶。 12a羟基化的胆汁酸 增加肝胆固醇并促进非酒精性脂肪性肝炎（NASH）14-16的进展。在 缺乏胰岛素，CYP8B1在细胞肝细胞中的抑制与12A--的增加有关 羟基化的胆汁酸，肝胆固醇增加和严重的炎症。 Nafld的事实 人类的进展还与12A-羟基化的胆汁酸和肝的增加有关 胆固醇以及炎症标志着非酒精性脂肪性肝炎的发展，更多 严重而渐进的疾病形式突出了研究这一途径17-19的重要性。基于这些 和其他初步数据，我们假设胰岛素调节了B-Catenin的活性，Master 转录调节剂仅在细胞肝细胞20中激活，以保持正常脂质 稳态并防止炎症。为了检验该假设，我们旨在（1）定义胰岛素调节的细胞 使用单核测序在肝脏中的转录程序； （2）剖析b-catenin在 产生对胰岛素的转录和生理反应。我们希望胰岛素可以重新编程 通过调节b-catenin驱动的转录，细胞的细胞肝细胞，这是正常的 稳态。这样的结果最终可能导致开发精确的干预措施，以扭转 胰岛素耐药性在细胞肝细胞中的影响，防止NASH。