Data_Sheet_2_Modulation of Gilthead Sea Bream Gut Microbiota by a Bioactive Egg White Hydrolysate: Interactions Between Bacteria and Host Lipid Metabolism.pdf

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有经肥胖大鼠实验证实具有抗氧化及抗肥胖活性的卵清蛋白水解物（egg white hydrolysate, EWH）的植物性饲料时，鱼类的日粮、生长性能与肠道黏膜附着菌群（前肠）之间的关联。本实验以金头鲷（Sparus aurata）幼鱼为研究对象，饲喂周期共计8周。实验鱼以接近视觉饱足的投喂量饲喂，日粮分为三大类：以鱼粉（fish meal, FM）/鱼油（fish oil, FO）为基础的对照组日粮（CTRL），以及添加或未添加EWH的植物性日粮。受采食量下降与饲料转化率轻微受损的影响，对照组实验鱼的特定生长率从2.16%逐步降至EWH饲喂组的1.88%。无论是否添加EWH，饲喂植物性日粮均会诱发前肠发生增生性炎症。但EWH可改善因FM/FO替换所诱导的杯状细胞减少，以及肝脏与肠道脂质堆积状况。对肠道黏膜菌群进行Illumina测序后，每个样本平均获得136252条有效序列，在97%相似度阈值下可归类为2117个操作分类单元（operational taxonomic unit, OTU）。各组间细菌多样性水平无显著差异，但EWH饲喂组的菌群丰富度显著降低。在门水平上，对照组与EWH饲喂组的变形菌门（Proteobacteria）占比最高；而随着FM/FO被替换，厚壁菌门（Firmicutes）占比下降，放线菌门（Actinobacteria）占比上升。日粮添加EWH可使放线菌门的占比恢复至正常水平，同时还可使拟杆菌门（Bacteroidetes）与螺旋体门（Spirochaetes）的占比达到最高。进一步分析可见，乳杆菌目（Lactobacillales）在所有组中均广泛存在。此外，由棒状杆菌属（Corynebacterium）与诺卡氏菌属（Nocardioides）代表的多糖水解酶分泌菌，其丰度会因FM/FO替换而上升；而降解黏蛋白的链球菌属（Streptococcus）仅在饲喂未添加EWH的植物性日粮的实验鱼体内丰度升高。此外，EWH饲喂组中丙酸杆菌属（Propionibacterium）的高丰度与肠道内丙酸浓度升高呈正相关。有益肠道健康的丙酸与胆固醇的拮抗作用，可解释EWH饲喂组菌群中初级胆汁酸生物合成与类固醇降解通路丰度偏低的现象。综上，本研究结果进一步证实了肠道菌群在宿主代谢调控，尤其是脂质代谢调控中的核心作用，同时表明具有生物活性的EWH肽可作为鱼类的抗肥胖因子和/或饱感因子发挥功能。