精氨酸对鲫鱼大豆诱导型肠炎的肠道保护作用机制

Plant materials such as legume seeds would cause decreased growth performance. Imbalanced amino acids and anti-nutritional factors are main factors. Excessive use of legumes in feed will affect the health of the digestive tract of fish. Intestine has the functions of digestion and absorption of nutrients, maintaining the chemical, mechanical and immune barrier. It will be affected by diet to occur enteritis. Arginine is an essential amino acid in teleost and has important physiological functions in protecting the intestinal health; maintaining close connections; promoting migration of epithelial cell, regulating cytokines and improving cellular immunity. Gibel carp, a non-stomach fish, will be the research object in this project. Soy induced chronic enteritis model of gibel carp will be established firstly. Then l-arginine will be added into soybean based diet in a gradient concentrations. Sampling time will be based in the chronic enteritis model. The study of functional properties of arginine will be based on inflammatory bowel disease. We will study the effect of arginine on intestinal barrier functions and the main pathway of the immune response. Metabolomics and transcriptomics methods will be induced to study the protection mechanisms of arginine in the intestine. The result from this project will provide methods and theoretical basis for nutritional regulation of immunity in the fish intestine.

豆粕等植物原料影响养殖鱼类生长的原因主要是氨基酸不平衡和存在抗营养因子。饲料中过多的豆类原料会影响鱼类的消化道健康。肠道具有消化吸收和免疫屏障的功能，会受到饲料影响导致免疫反应。精氨酸是硬骨鱼类的必需氨基酸，在保护肠道健康方面也具有重要的生理功能：维持上皮细胞的紧密连接、促进上皮细胞的迁移、调节免疫细胞因子、改善细胞免疫等，可以缓解肠炎。因此本项目拟以无胃鱼异育银鲫作为研究对象，构建大豆诱导慢性肠炎的模型，获得相关参数。在大豆型饲料中补充精氨酸，根据模型进行取样，在肠道炎症发生的基础上研究精氨酸的功能特性。研究精氨酸对肠道的屏障功能的作用；对主要营养免疫应答通路的影响；结合代谢组和转录组方法探讨精氨酸的肠道保护机制。为用营养学手段调节鱼类消化道免疫力提供方案和理论依据。

本研究构建了异育银鲫大豆诱导型肠炎模型，在饲料中添加16%豆粕可观察到肠道炎症反应的发生，表现为组织损伤、氧化应激、炎症因子表达量升高等特征。在此基础上确定了在豆粕含量为16.5-33%的饲料导致异育银鲫肠炎发生、生长性能下降，而当豆粕饲料中添加精氨酸含量为1-2%时，对异育银鲫的消化吸收能力和生长具有促进作用。结果表明当饲料中精氨酸含量不充足时，如果有外界因素（豆粕的抗营养因子）诱发肠道的炎症反应，组织中的精氨酸首先作为一氧化氮（NO）的前体物质，由NO发挥抗病原、招募免疫细胞、诱导炎症等作用，而过度的炎症反应会导致炎症组织出现氧化应激、细胞凋亡等次级反应。在饲料中补充精氨酸的情况下，充足的精氨酸会同时调节PI3K-AKT-TOR通路，并且作为蛋白质合成的原料促进组织的修复和生长，同时精氨酸在各种酶作用下的代谢产物，如肌酸、鸟氨酸、脯氨酸、羟脯氨酸、多胺、GABA等也会通过调节JAK-STAT、NF-κB等通路，参与抗氧化应激、抗炎症、抗凋亡、促进细胞增殖分化等组织修复的过程。因此本研究结果表明肠道组织中充足的精氨酸在应对豆粕导致肠炎的过程中发挥了平衡炎症反应，促进组织修复的作用。