Regulation of Hepatobiliary Bile Acid Homeostasis in Neonatal Obstructive Cholestasis

项目总结 胆道闭锁(BA)导致严重的胆汁酸平衡紊乱，是导致胆汁酸失衡的主要原因 新生儿梗阻性胆汁淤积症。核激素受体法尼醇对胆汁酸稳态的调节 X受体(FXR)通过激活肠道和肝脏激素成纤维细胞生长因子19(FGF19)。 FGF19抑制肝细胞色素P450 7a1(Cyp7a1)的胆汁酸合成 胆汁酸合成。在健康婴儿中，FGF19主要在肠道中表达，在肝脏中表达较少。在……里面 相比之下，BA婴儿肝脏FGF19升高，以补偿肠道胆汁酸诱导的FGF19丢失 分泌物。BA婴儿肝脏FGF19和胆汁酸积聚的增加表明 FGF19信号通常抑制肝脏Cyp7a1和胆汁酸的合成。胆汁的第二来源 肝细胞和胆管细胞的酸合成是通过Cyp27a1的替代途径。我们有一条鸿沟 通过FXR-FGF19信号调节Cyp7a1和Cyp27a1如何促进胆汁酸的知识 新生儿梗阻性胆汁淤积症的动态平衡。这项建议旨在理解适应性、时效性- 肝脏补偿肠道胆汁酸信号改变的依赖机制及其如何 补偿通过经典途径和替代途径影响胆汁酸的合成。我们的中心假设是 肝脏对梗阻性胆汁淤积的适应性导致肝细胞FXR-FGF19信号增加，但 抑制Cyp7a1或补偿Cyp27a1以维持胆汁酸蓄积。在目标1a中，我们 将表征胆汁淤积性肝损伤的个体发生、胆汁酸稳态和细胞特异性肝细胞和 胆管结扎新生猪模型中胆管细胞基因表达特征。 在目标1b中，我们将量化涉及胆汁的fxr和fgf19信号通路的分子机制。 人培养肝细胞和胆管细胞长期接触胆汁酸过程中的酸合成 有机化合物。在目标2a中，我们将测试FGF19输注是否以剂量依赖的方式抑制Cyp7a1在 BDL后的早、晚时间点。在目标2b中，我们将测试早期激活FXR-FGF19信号是否具有保护作用 抗胆汁淤积。这项研究将有助于了解胆汁酸的调节机制。 新生儿梗阻性胆汁淤积症的动态平衡和测试潜在的治疗干预措施。 职业发展和环境：增强我作为独立人士未来成功的潜力 研究人员I将接受道格拉斯·伯林博士的指导，并接受稳定同位素动力学使用方面的培训 建模、质谱分析、rna-seq管道分析和可视化，以及肝脏器官 培养。本次培训将在优秀的儿童营养研究环境中进行 NIDDK消化疾病中心技术核心和专家教员的支持下的研究中心(CNRC) 贝勒医学院的监督委员会。这个项目将为我提供科学专业知识和研究 在儿科肝病领域开展独立研究的技能。

PROJECT SUMMARY Biliary atresia (BA) results in severe disruption of bile acid homeostasis and is the predominant disease causing neonatal obstructive cholestasis. Bile acid homeostasis in regulated by the nuclear hormone receptor Farnesoid X Receptor (FXR) by activation of the intestinal and hepatic hormone, fibroblast growth factor 19 (FGF19). FGF19 suppresses bile acid synthesis of hepatic cytochrome P450 7a1 (Cyp7a1), the key enzyme for classical bile acid synthesis. In healthy infants, the FGF19 expression is mainly in the intestine and low in the liver. In contrast, hepatic FGF19 is elevated in BA infants to compensate for loss of intestinal bile acid-induced FGF19 secretion. The increase in hepatic FGF19 and bile acid accumulation in BA infants suggests an uncoupling of FGF19 signaling that normally suppresses hepatic Cyp7a1 and bile acid synthesis. A secondary source of bile acid synthesis in hepatocytes and cholangiocytes is the alternative pathway via Cyp27a1. There is a gap in our knowledge of how the regulation of Cyp7a1 and Cyp27a1 via FXR-FGF19 signaling contributes to bile acid homeostasis during neonatal obstructive cholestasis. This proposal aims to understand the adaptive, time- dependent mechanism by which the liver compensates for altered intestinal bile acid signaling and how this compensation effects bile acid synthesis via the classical and alternative pathways. Our central hypothesis is that hepatic adaptation to obstructive cholestasis leads to increased hepatocyte FXR-FGF19 signaling, but with impaired suppression of Cyp7a1 or compensation by Cyp27a1 to sustain bile acid accumulation. In Aim 1a we will characterize the ontogeny of cholestatic liver injury, bile acid homeostasis, and cell-specific hepatocyte and cholangiocyte gene expression signatures in a newly developed neonatal pig model of bile duct ligation (BDL). In Aim 1b, we will quantify the molecular mechanisms of FXR and FGF19 signaling pathways involved in bile acid synthesis during long-term bile acid exposure using human cultured hepatocyte and cholangiocyte organoids. In Aim 2a, we will test whether FGF19 infusion dose-dependently suppresses Cyp7a1 expression at early and late time points after BDL. In Aim 2b, we will test if early activation of FXR-FGF19 signaling protects against BDL induced cholestasis. This study will provide understanding of the mechanism that regulate bile acid homeostasis in the context of neonatal obstructive cholestasis and test potential therapeutic interventions. Career development and environment: To enhance my potential for future success as an independent researcher I will receive mentorship from Dr. Douglas Burrin, PhD and training in use of stable isotope kinetics modeling, mass spectrometry analysis, RNA-seq pipeline analysis and visualization, and hepatic organoid culturing. This training will be conducted in an outstanding research environment of the Children’s Nutrition Research Center (CNRC) with support of NIDDK Digestive Disease Center technical cores and an expert faculty oversight committee at Baylor College of Medicine. This project will give me the scientific expertise and research skills to launch an independent research career in the field of pediatric liver diseases.