The study investigated the effects of dietary isoleucine (Ile) on skin mucus barrier and epithelial physical barrier functions of hybrid bagrid catfish Pelteobagrus vachelli × Leiocassis longirostris. A total of 630 fish (33.11 ± 0.09 g) were fed semi-purified isonitrogenous diets containing 5.0 (control), 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile kg ⁻¹ diet for 8 weeks. The results indicated that dietary Ile increased (P < 0.05) in skin (1) mucus protein content and antimicrobial activity against three gram-negative bacteria (Aeromonas hydrophila, Escherichia coli, and Yersinia ruckeri) and two gram-positive bacteria (Streptococcus agalactiae and Staphylococcus aureus), (2) mucus lysofew information is available about the influencezyme (LZM), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities, and complement 3 and 4 (C3 and C4) and immunoglobulin M (IgM) contents, (3) intelectin 1 (intl1), intelectin 2 (intl2), c-type-lysozyme (c-LZM), g-type-lysozyme (g-LZM), and β-defensin mRNA levels. Dietary Ile decreased (P < 0.05) reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl (PC) contents, and up-regulated (P < 0.05) CuZnSOD, GST, GPX1a, muc5ac, muc5b, zonula occludens-1 (ZO-1), zonula occludens-2 (ZO-2), occludin, and claudin 3 mRNA levels in skin. These results indicated that Ile improved skin mucus barrier function via increasing mucus protein, C3 and C4, and IgM contents and antibacterial factors activities, and promoted epithelial physical barrier function via decreasing skin antioxidant damage and improving tight junction structure in hybrid bagrid catfish.

该研究调查了饮食中异亮氨酸（Ile）对杂色袋装cat鱼Pelteobagrus vachelli × Leiocassis longirostris的皮肤黏液屏障和上皮物理屏障功能的影响。总共对630条鱼（33.11±0.09 g）喂食了半纯的等氮日粮，其中包含5.0（对照），7.5、10.0、12.5、15.0、17.5和20.0 g Ile kg - ¹日粮，持续8周。结果表明，饮食中的Ile会增加（P  <0.05）皮肤（1）黏液蛋白含量，并且对三种革兰氏阴性细菌（嗜水气单胞菌，大肠杆菌和Rersinia ruckeri）和两种革兰氏阳性细菌（三种）具有抗菌活性无乳链球菌和金黄色葡萄球菌），（2）可获得关于影响酶（LZM），酸性磷酸酶（ACP）和碱性磷酸酶（AKP）活性以及补体3和4（C3和C4）和免疫球蛋白M（ IgM）含量，（3）整合素1（intl1），整合素2（intl2），c型溶菌酶（c-LZM），g型溶菌酶（g-LZM）和β-防御素mRNA水平。饮食中的Ile降低（P  <0.05）活性氧（ROS），丙二醛（MDA）和蛋白质羰基（PC）含量，并上调（P <0.05）CuZnSOD，GST，GPX1a，muc5ac，muc5b，zonula occludens-1（ZO-1），zonula occludens-2（ZO-2），occludin和claudin 3 mRNA水平在皮肤中。这些结果表明，Ile通过增加粘液蛋白，C3和C4以及IgM含量和抗菌因子的活性来改善皮肤粘液屏障功能，并通过减少皮肤抗氧化剂损伤和改善杂交袋装rid鱼的紧密连接结构来促进上皮物理屏障功能。