阿拉伯木聚糖对不同食性鱼类肠道黏膜屏障功能的影响及其差异机制研究

Antinutritional factor present in plant-derived protein sources is one of key factors restricting the utilization of these plant-derived protein sources in fish feeds. Non-starch polysaccharides (NSP) are the major cell wall components in plants, and also are the main antinutritional factors in fish feeds. However, limited information is available about the antinutritional mechanism of NSP so far. Based on metabolomics and 16S rDNA sequencing technique, our previous studies showed that the discrepancy of utilization of soybean meal among fish with different food habits might mainly depend on their sensibility and tolerance to NSP present in soybean meal, and the antinutritional effects of NSP may be related to the intestinal mucosal barrier injury induced by dietary NSP. Based on our previous studies, a 12-week feeding trial, using rainbow trout (Oncorhynchus mykiss), tilapia (Oreochromis niloticus × Oreochromis aureus) and grass carp (Ctenopharyngodon idella) as a test carnivorous, omnivorous and herbivorous fish, respectively, and taking araboxylan as the representative of soy NSP, will be conducted to compare the effects of different dosage of dietary araboxylan on the intestinal mucosal barrier function (intestinal mucosal permeability, diamine oxidase activity and endothelin-1 content in blood and intestinal mucosa, plasma bacterial endotoxin content) of rainbow trout, tilapia and grass carp. In addition, the influences of different dosage of dietary araboxylan on the mechanical, chemical, biological and immunological barriers and signaling pathways (mitogen-activated protein kinase (MAPK) pathway, phosphoinositide 3-kinase (PI3K)-Akt pathway, nuclear factor kappa B (NF-κB) pathway) related to intestinal mucosal barrier function in fish with different food habits (rainbow trout, tilapia and grass carp) will be evaluated, and thereby to clarify the distinct mechanism of intestinal mucosal barrier dysfunction induced by dietary araboxylan among fish with different food habits. The results obtained during the study are expected to have significant academic contributions and practical implications.

抗营养因子是限制鱼类高效利用植物蛋白源的主要障碍。非淀粉多糖是植物细胞壁主要组分，也是鱼类饲料中主要的抗营养因子，但对其抗营养机制却知之甚少。本项目组前期研究发现，不同食性鱼类利用豆粕能力的差异源于其对豆粕中非淀粉多糖的响应差异，而这种响应差异与其肠道黏膜屏障功能调节密切相关。本项目拟在前期研究基础上，分别以虹鳟、罗非鱼和草鱼作为肉食性、杂食性和草食性鱼类代表，以阿拉伯木聚糖(AX)作为非淀粉多糖代表，比较研究不同剂量AX对虹鳟、罗非鱼和草鱼肠道黏膜屏障功能(黏膜通透性、血液和黏膜二胺氧化酶活性及内皮素-1含量、血液内毒素含量)的影响；并比较分析不同剂量AX对虹鳟、罗非鱼和草鱼肠道黏膜机械屏障、化学屏障、生物屏障和免疫屏障及相关信号通路(MAPK、PI3K-Akt、NF-κB)的影响，进而阐明AX调节不同食性鱼类肠道黏膜屏障功能的差异机制。预期研究成果将具有重要的理论价值和广泛的应用前景。

抗营养因子是限制鱼类高效利用植物蛋白源的主要障碍。非淀粉多糖是植物细胞壁主要组分，也是鱼类饲料中的主要抗营养因子，但对其抗营养作用机制却了解甚少。本项目分别以虹鳟、罗非鱼和草鱼作为肉食性、杂食性和草食性鱼类代表，以阿拉伯木聚糖(AX)作为非淀粉多糖代表，比较研究了不同剂量(0%、2.5%、5%、10%)AX对虹鳟、罗非鱼和草鱼生长性能、肠道黏膜屏障功能、肠道黏膜机械屏障、化学屏障、生物屏障和免疫屏障及相关信号通路的影响；此外，还比较研究了不同结构特性(溶解性、黏性、可发酵性)AX对大口黑鲈生长性能和肠道健康的影响。结果表明：2.5～10%AX显著降低了虹鳟和罗非鱼生长性能和饲料利用率，5～10%AX显著降低了草鱼生长性能和饲料利用率；高剂量(5～10%)AX均明显破坏了不同食性鱼类肠道黏膜机械屏障、化学屏障和免疫屏障，降低肠道有益菌丰度，提高有害菌丰度，损伤肠道黏膜屏障功能，进而抑制鱼类生长；高剂量AX导致虹鳟肠道黏膜促炎因子(IL-6、IL-8、TNF-α)上调，抑炎因子(IL-10、TGF-β)下调；罗非鱼肠道黏膜促炎因子(IL-6、IL-8)和抑炎因子(IL-10、TGF-β)同步上调；草鱼肠道黏膜促炎因子(IL-8、IL-12、TNF-α)和抑炎因子(IL-10、TGF-β)同步下调；不同结构特性AX差异调控大口黑鲈肠道健康；水溶性AX呈现明显的抗营养效应，但不溶性AX未呈现类似抗营养效应；高黏度AX破坏大口黑鲈肠道黏膜屏障，但AX可发酵性有助于缓解其负面效应。由此可见，不同食性鱼类对饲料中AX耐受性均较低，且不同食性鱼类肠道免疫屏障对AX响应差异较大；植物性饲料原料中所含水溶性AX具有明显的抗营养效应，不利于鱼类肠道健康和生长。本项目研究不仅补充完善了AX对鱼类的抗营养机理，还可为实现鱼类对植物蛋白源的高效利用提供科学依据，具有重要的经济价值和广泛的应用前景。