Regulation of Hepatic Metabolic Function by Parenteral Nutrition

描述(申请人提供)：这项研究的长期目标是确定肠外脂肪营养如何调节肝脏代谢功能和改变婴儿肝脏疾病的风险。接受完全肠外营养(TPN)的婴儿患代谢性肝病的风险增加。我们对早产仔猪的初步研究表明，与肠内营养相比，富含植物甾醇和n-6脂肪酸(FA)的TPN可以诱导肝脏胆汁淤积、脂肪变性和炎症。TPN还抑制血浆FGF19，这是法尼类X受体(FXR)的产物，FXR激动剂的治疗逆转了TPN喂养的仔猪的胆汁淤积。我们的中心假设是，肠外脂肪营养不含植物甾醇，富含n-3vs.n-6FA，将通过激活FXR来预防TPN喂养的早产仔猪的TPN相关性肝胆汁淤积和脂肪变性。目的1检验不含植物甾醇的肠外脂肪营养是否能预防非脂负荷的TPN喂养的早产猪肝脏代谢功能障碍。我们将使用体内代谢(13C-胆汁酸周转和13C-棕榈酸氧化动力学)以及肝脏转录和代谢组学方法来系统地量化肝脏胆汁酸和脂肪代谢的代谢途径。RNAseq分析和代谢组谱将被用来识别潜在的新的肝脏基因和基因网络的差异表达。目的2检测注射用大豆脂肪乳剂中的植物甾醇是否通过拮抗FXR受体功能而导致胆汁淤积和代谢性肝病。我们将检测~(13)C-胆汁酸代谢动力学、血清生化标志物、肝脏组织病理学以及FXR和FXR靶基因的组织表达，特别是参与胆汁酸代谢的细胞色素P7A1。我们将使用肝细胞来测量FXR活性的表达，并利用单个植物甾醇以及FXR的激动剂和拮抗剂来建立分子机制的特异性。目的3检测天然和新型FXR选择性胆汁酸刺激的肠道FGF19分泌是否通过反馈调节FXR和细胞色素P7A1信号来预防TPN诱导的胆汁淤积。我们将检测~(13)C-胆汁酸代谢动力学、血清标志物、肝组织病理学以及FXR、FGF19、CYP7A1和参与胆汁酸代谢的靶基因的组织表达。我们将利用仔猪肝细胞培养来检测FXR靶基因的mRNA表达以及FGF19、植物甾醇和不同脂肪乳剂存在下的成纤维细胞生长因子受体-4信号转导。这些研究将测试新的机制，以确定肠外脂肪营养中的植物甾醇是否会在临床相关的新生儿动物模型中对肝脏代谢功能和疾病产生不利影响。这些针对早产猪的研究具有很高的转化性，并将在婴儿营养支持和预防肝病方面带来新的临床实践。

DESCRIPTION (provided by applicant): The long-term goal of this research is to establish how parenteral lipid nutrition regulates hepatic metabolic function and alters the risk of liver disease in infants. Infants given total parenteral nutrition (TPN) have increased risk for metabolic liver diseases. Our preliminary studies in premature piglets show that TPN enriched with phytosterols and n-6 fatty acids (FA) induces hepatic cholestasis, steatosis and inflammation compared to enteral nutrition. TPN also suppresses plasma FGF19, a product of farnesoid X receptor (FXR), and treatment with an FXR-agonist reverses cholestasis in TPN-fed piglets. Our central hypotheses is that parenteral lipid nutrition devoid of phytosterols and enriched with n-3 vs. n-6 FA and will prevent the TPN- associated hepatic cholestasis and steatosis in premature TPN-fed piglets via activation of FXR. AIM 1 will test whether parenteral lipid nutrition devoid of phytosterols prevents hepatic metabolic dysfunction independent of lipid load TPN-fed premature pigs. We will use in vivo metabolic (13C-bile acid turnover and 13C-palmitate oxidation kinetics) and liver transcriptomic and metabolomic approaches to systematically quantify metabolic pathways in hepatic bile acid and lipid metabolism. RNAseq analysis and metabolomic profiling will be used to identify differential expression of potentially novel hepatic genes and gene networks. Aim 2 will test whether phytosterols present in parenteral soybean-lipid emulsions induce cholestasis and metabolic liver disease via antagonism of FXR receptor function. We will measure 13C-bile acid turnover kinetics, serum biochemical markers, liver histopathology, and tissue expression of FXR and FXR target genes, especially CYP7A1, involved in bile acid metabolism. We will use hepatocytes to measure expression of FXR activity and establish the specificity of the molecular mechanisms using individual phytosterols as well as an agonist and antagonist of FXR. AIM 3 will test whether intestinal FGF19 secretion stimulated by natural and novel FXR- selective bile-acids prevents TPN-induced cholestasis by feedback regulation of FXR and CYP7A1 signaling. We will measure 13C-bile acid turnover kinetics, serum markers, liver histopathology, and tissue expression of FXR, FGF19, CYP7A1 and target genes involved in bile acid metabolism. We will use piglet hepatocytes cultures to measure mRNA expression of FXR target genes and FGF receptor-4 signaling in the presence of FGF19, phytosterols and different the lipid emulsions. These studies will test novel mechanisms to establish whether phytosterols in parenteral lipid nutrition adversely affect hepatic metabolic function and disease in a clinically-relevant, neonata animal model. These studies in premature pigs are highly translational and will lead to new clinical practices in nutritional support and prevention of liver disease in infants.