大豆黄酮对大菱鲆肠道健康的保护作用及机制研究

High levels of plant protein in diets for carnivorous fish species easily cause enteropathy. Since intestine is the most important digestive organ of fish and plays key roles in immunity and disease resistance, homeostasis of the intestine is crucial for securing optimal fish health and growth. The intestinal mucosal barriers (IMB) are widely regarded as the most important selective defensive barriers of animals to maintain intestinal homeostasis. The intestinal microbiota is also critical for intestinal homeostasis and its imbalance has been considered as pivotal factor in the initiation of chronic intestinal disease. Previous studies of the author focused on the effects of plant protein sources and the anti-nutritional factors in them on the intestinal health of turbot, and found that one of anti-nutritional factors in soybean meal, daidzein, could enhanced the function of IMB and improve the balance of intestinal bacterial community of turbot. Based on these results, this study is aimed at evaluating the protecting effects of daidzein on the IMB and intestinal microbiota of turbot when fish were fed diets with high levels of plant protein. The precise mechanisms involved will be investigated with the analysis of metagenomics and metabolites, analysis of transcriptomics, and transcriptional and phosphorylation level analysis of key proteins in relevant signaling pathways. The primary-cultured intestinal epithelial cells isolated from turbot will be also used as in vitro model to investigate the regulating effects of daidzein in this project. The results of this research will provide and deeper and more comprehensive insights into overall knowledge about effects of dietary daidzein on fish intestinal health. This project will be helpful for exploiting nutritional methods to alleviate the intestinal impairment caused by diets with high levels of plant protein, and consequently helpful for improving the efficiency of plant protein utilization in marine carnivorous fish.

饲料中高植物蛋白通常会诱发肉食性养殖鱼类肠道炎症反应。肠道黏膜屏障功能受损和肠道菌群结构紊乱是动物发生肠炎的首要原因。申请人前期在研究大豆黄酮“营养抗性”时却发现其在适量添加时反而具有增强鱼类肠道健康的作用。本项目拟通过在高植物蛋白饲料中添加不同剂量的大豆黄酮开展摄食生长实验，研究大豆黄酮对大菱鲆肠道黏膜屏障功能和肠道菌群结构的影响，评价大豆黄酮对大菱鲆肠道健康的保护作用；同时，结合肠道上皮细胞模型，基于组学测序及信息分析、分子生物学和传统微生物学等方法和技术，筛选和验证调控肠道黏膜屏障功能的主要信号通路、分析肠道微生物功能和代谢产物，筛选和验证特异性肠道微生物和主要代谢产物功能，进而阐释大豆黄酮对肠道黏膜屏障功能和肠道微生物的具体作用机制，全面解读和构建大豆黄酮改善鱼类肠道健康的调控模式。本研究结果将有助于探索通过营养学方法调控肠道健康状态进而提高肉食性鱼类对植物蛋白的利用效率。

鱼粉资源短缺是制约水产养殖发展的一个重要因素。但肉食性鱼类摄入一定量的植物蛋白源容易后发生肠炎症状，所以通过营养调控技术来提高来源广泛、价格低廉的植物蛋白源在养殖鱼类中的利用效率是促进健康养殖的重要途径之一。大豆黄酮在课题组的前期研究中表现出对鱼类肠道健康具有积极作用，本项目正是在此背景下对大豆黄酮在肉食性养殖鱼类大菱鲆开展了一系列全面系统深入的研究。研究结果表明大豆黄酮能够显著缓解大菱鲆因摄入高豆粕饲料引发的肠炎症状，改善其生长性能和机体健康。通过体内、体外实验相结合，阐释了大豆黄酮对大菱鲆肠道健康的保护作用机制，并且明确指出肠道微生物在大豆黄酮发挥作用中积极响应。项目对大豆黄酮在大菱鲆饲料中的应用技术进一步优化，提出改善大菱鲆肠道健康的营养策略。最后项目还拓展性的基于系统发育共生探究了包括大菱鲆在内的三种海水肉食性鱼类肠道微生物与宏量营养素代谢的关系，以便更具个性化选择鱼类益生菌。这些研究成果为解决高植物蛋白饲料诱发的鱼类肠炎问题、新型饲料添加剂的开发及鱼类个性化的益生菌选择提供了重要理论参考和技术支持。本项目相关成果已发表学术论文23篇，其中SCI收录论文22篇，中文核心期刊1篇，授权国家发明专利2项。