Table_3_Modulation of Gilthead Sea Bream Gut Microbiota by a Bioactive Egg White Hydrolysate: Interactions Between Bacteria and Host Lipid Metabolism.xlsx

This study aimed to highlight the relationship between diet, animal performance and mucosal adherent gut microbiota (anterior intestine) in fish fed plant-based diets supplemented with an egg white hydrolysate (EWH) with antioxidant and anti-obesogenic activity in obese rats. The feeding trial with juveniles of gilthead sea bream (Sparus aurata) lasted 8 weeks. Fish were fed near to visual satiety with a fish meal (FM)/fish oil (FO) based diet (CTRL) or a plant-based diet with/without EWH supplementation. Specific growth rate decreased gradually from 2.16% in CTRL fish to 1.88% in EWH fish due to a reduced feed intake, and a slight impairment of feed conversion ratio. Plant-based diets feeding triggered a hyperplasic inflammation of the anterior intestine regardless of EWH supplementation. However, EWH ameliorated the goblet cell depletion, and the hepatic and intestinal lipid accumulation induced by FM/FO replacement. Illumina sequencing of gut mucosal microbiota yielded a mean of 136,252 reads per sample assigned to 2,117 OTUs at 97% identity threshold. The bacterial diversity was similar in all groups, but a significantly lower richness was found in EWH fish. At the phylum level, Proteobacteria reached the highest proportion in CTRL and EWH fish, whereas Firmicutes were decreased and Actinobacteria increased with the FM/FO replacement. The proportion of Actinobacteria was restored by dietary EWH supplementation, which also triggered a highest amount of Bacteroidetes and Spirochaetes. At a closer look, a widespread presence of Lactobacillales among groups was found. Otherwise, polysaccharide hydrolases secretors represented by Corynebacterium and Nocardioides were increased by the FM/FO replacement, whereas the mucin-degrading Streptococcus was only raised in fish fed the plant-based diet without EWH. In addition, in EWH fish, a higher abundance of Propionibacterium was related to an increased concentration of intestinal propionate. The antagonism of gut health-promoting propionate with cholesterol could explain the inferred underrepresentation of primary bile acid biosynthesis and steroid degradation pathways in the EWH fish microbiota. Altogether, these results reinforce the central role of gut microbiota in the regulation of host metabolism and lipid metabolism in particular, suggesting a role of the bioactive EWH peptides as an anti-obesity and/or satiety factor in fish.

本研究旨在阐明饲喂添加具抗氧化与抗肥胖活性的卵清水解物（egg white hydrolysate, EWH）的植物性饲料时，鱼类的饮食、生长性能与肠道黏膜黏附菌群（前肠）之间的关联。本实验以金头鲷（Sparus aurata）幼鱼为研究对象，饲养周期共计8周。实验鱼以接近视觉饱食度的频次饲喂两类饲料：一类是以鱼粉（fish meal, FM）/鱼油（fish oil, FO）为基础的对照组饲料（CTRL），另一类为添加或未添加EWH的植物性饲料。相较于对照组鱼类的2.16%，EWH组鱼类的特定生长率逐渐降至1.88%，该现象源于采食量降低以及饲料转化率小幅受损。无论是否添加EWH，饲喂植物性饲料均会触发前肠增生性炎症。但EWH可改善FM/FO替代所诱导的杯状细胞耗竭以及肝脏与肠道脂质蓄积。对肠道黏膜菌群进行Illumina测序后，每个样本平均获得136252条有效读段，在97%相似度阈值下可归类为2117个操作分类单元（operational taxonomic unit, OTU）。各组细菌的多样性水平相近，但EWH组鱼类的菌群丰富度显著降低。在门水平上，对照组与EWH组鱼类的变形菌门（Proteobacteria）占比最高；而随着FM/FO被替代，厚壁菌门（Firmicutes）占比下降，放线菌门（Actinobacteria）占比上升。日粮添加EWH可恢复放线菌门的占比，同时可使拟杆菌门（Bacteroidetes）与螺旋体门（Spirochaetes）的丰度达到最高水平。进一步分析显示，各组中乳杆菌目（Lactobacillales）均广泛存在。此外，FM/FO替代可使分泌多糖水解酶的棒状杆菌属（Corynebacterium）与诺卡氏菌属（Nocardioides）丰度升高；而降解黏蛋白的链球菌属（Streptococcus）仅在饲喂未添加EWH的植物性饲料的鱼类中丰度提升。另外，EWH组鱼类中丙酸杆菌属（Propionibacterium）的高丰度与肠道内丙酸浓度升高相关。有益于肠道健康的丙酸与胆固醇的拮抗作用，可解释EWH组鱼类菌群中初级胆汁酸生物合成与类固醇降解通路的推断性低丰度现象。综上，本研究结果进一步证实了肠道菌群在宿主代谢尤其是脂质代谢调控中的核心作用，表明具有生物活性的EWH肽可作为鱼类的抗肥胖因子和/或饱食因子。