This study evaluated the effect of methionine supplementation, predation risk and their interaction on gut histology, whole-body cortisol levels, and intestinal gene expression in zebrafish. A total of 360 one-year-old animals were maintained under two environmental conditions and fed diets containing different methionine sources. Fish were fed either a control diet (CTL, without methionine supplementation), a diet supplemented with dl-methionine (DLM), or a diet supplemented with methionine dipeptide (MM) in the absence (AP) of a predator or in the presence of the predator (PP) for 48 h or 20 days. Predator-induced stress for 20 days resulted in lower body weight. Zebrafish fed methionine-supplemented diets had higher weight gain than control fish. We found no effect of predation stress or methionine supplementation on cortisol level. Predation risk and methionine supplementation showed no interaction effect on dipeptide transporter gene expression. After 48 h of predation pressure, zebrafish had higher mRNA expression of SOD2, CAT and GPX1 in the gut. After 20 days of exposure to the predator, zebrafish fed methionine-supplemented diets had lower expression of GPX1, SOD2 and CAT than those diet CTL. Methionine dipeptide and free methionine supplementation improved growth, intestinal health and survivability of zebrafish both conditions.

中文翻译：

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在捕食风险下补充蛋氨酸二肽的斑马鱼肠道中 PEPT1、CAT、SOD2 和 GPX1 基因的表达

本研究评估了补充蛋氨酸、捕食风险及其相互作用对斑马鱼肠道组织学、全身皮质醇水平和肠道基因表达的影响。共有 360 只一岁的动物在两种环境条件下饲养，并喂食含有不同蛋氨酸来源的饮食。给鱼喂食对照饮食（CTL，不添加蛋氨酸）、添加dl的饮食-蛋氨酸 (DLM)，或在没有捕食者 (AP) 或捕食者 (PP) 存在 48 小时或 20 天的情况下补充蛋氨酸二肽 (MM) 的饮食。捕食者引起的压力持续 20 天导致体重降低。饲喂补充蛋氨酸的斑马鱼比对照鱼的体重增加更高。我们发现捕食应激或补充蛋氨酸对皮质醇水平没有影响。捕食风险和补充蛋氨酸对二肽转运蛋白基因表达没有相互作用。捕食压力48小时后，斑马鱼肠道中SOD2、CAT和GPX1的mRNA表达较高。与捕食者接触 20 天后，饲喂补充蛋氨酸的斑马鱼 GPX1 的表达降低，SOD2和CAT比那些饮食中的CTL。蛋氨酸二肽和游离蛋氨酸补充剂改善了斑马鱼的生长、肠道健康和生存能力。