Pan Fei-Yu, Wu Pei, Feng Lin, Jiang Wei-Dan, Kuang Sheng-Yao, Tang Ling, Tang Wu-Neng, Zhang Yong-An, Zhou Xiao-Qiu, Liu Yang
Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China.
Animal Nutrition Institute, Sichuan Agricultural University, Chengdu 611130, China; Fish Nutrition and Safety Production University Key Laboratory of Sichuan Province, Sichuan Agricultural University, Chengdu 611130, China; Key Laboratory for Animal Disease-Resistance Nutrition of China Ministry of Education, Sichuan Agricultural University, Chengdu 611130, China.
Fish Shellfish Immunol. 2017 May;64:122-136. doi: 10.1016/j.fsi.2017.03.012. Epub 2017 Mar 6.
This study was conducted to test the hypothesis that methionine hydroxy analogue (MHA) enhances the defense against enteritis occurrence via improving intestinal barrier function in fish. After 630 young grass carp (Ctenopharyngodon idella) (259.70 ± 0.47 g) fed six graded levels of MHA (0, 2.4, 4.4, 6.4, 8.5 and 10.5 g/kg diet) and one dl-methionine group (6.4 g/kg diet) for 8 weeks. At the end of feeding trial, 15 fish from each treatment were challenged with Aeromonas hydrophila for 14 days. The results indicated that optimal MHA enhanced the capacity of fish against enteritis emergence, which might be related to the positive effects of MHA on intestinal immunological and physical barrier function in fish. Dietary MHA supplementation enhanced intestinal immunological barrier function via (1) lysozyme (LZM) and acid phosphatase (ACP) activities, complement 3 (C3), C4 and immunoglobulin M (IgM) contents and up-regulated mRNA levels of liver-expressed antimicrobial peptide 2, hepcidin (head kidney), β-defensin-1; (2) repressing p38MAPK/IKKβ/IκBα/NF-κB signaling pathway to down-regulate pro-inflammatory cytokines mRNA levels except IL-8 mRNA level only in mid and distal intestine; (3) potentiating TOR-signal cascades to up-regulate anti-inflammatory cytokines. Meanwhile, dietary MHA supplementation improved intestinal physical barrier via (1) down-regulating c-Jun N-terminal kinase mRNA levels to inhibit death receptor and mitochondria pathways induced apoptosis; (2) modulating Keap1a/Nrf2 system to elevate antioxidant enzymes genes isoforms mRNA levels and corresponding enzymes activities, subsequently alleviate oxidative damage; (3) down-regulating MCLK gene expression to up-regulating occludin, zonula occluden 1 and claudins mRNA levels except claudin-7a and claudin-7b only in the proximal intestine. In conclusion, bases on the capacity defense against enteritis, proximal intestinal malondialdehyde content and lysozyme activity, the optimal MHA supplementation levels were 5.83, 5.59 and 6.07 g/kg diet (4.01 g/kg methionine basal), respectively. This study indicates that MHA exerts a positive effect on fish intestinal health status and a superior efficacy to dl-methionine based on the positive effects.
本研究旨在验证蛋氨酸羟基类似物（MHA）通过改善鱼类肠道屏障功能来增强对肠炎发生的防御能力这一假设。630尾幼草鱼（草鱼）（259.70±0.47克）分别投喂六种不同梯度水平的MHA（0、2.4、4.4、6.4、8.5和10.5克/千克饲料）以及一个DL-蛋氨酸组（6.4克/千克饲料），为期8周。在饲养试验结束时，对每个处理组的15尾鱼用嗜水气单胞菌攻毒14天。结果表明，最佳剂量的MHA增强了鱼类抵抗肠炎发生的能力，这可能与MHA对鱼类肠道免疫和物理屏障功能的积极作用有关。日粮中添加MHA通过以下方式增强肠道免疫屏障功能：（1）提高溶菌酶（LZM）和酸性磷酸酶（ACP）活性、补体3（C3）、C4和免疫球蛋白M（IgM）含量，并上调肝脏表达的抗菌肽2、铁调素（头肾）、β-防御素-1的mRNA水平；（2）抑制p38MAPK/IKKβ/IκBα/NF-κB信号通路，下调促炎细胞因子mRNA水平，但仅在中肠和远肠中IL-8 mRNA水平除外；（3）增强TOR信号级联反应，上调抗炎细胞因子。同时，日粮中添加MHA通过以下方式改善肠道物理屏障：（1）下调c-Jun氨基末端激酶mRNA水平，抑制死亡受体和线粒体途径诱导的细胞凋亡；（2）调节Keap1a/Nrf2系统，提高抗氧化酶基因亚型的mRNA水平和相应酶的活性，从而减轻氧化损伤；（3）下调MCLK基因表达，上调紧密连接蛋白、闭合蛋白1和闭合蛋白的mRNA水平，但仅在近端肠道中闭合蛋白-7a和闭合蛋白-7b除外。总之，基于对肠炎的防御能力、近端肠道丙二醛含量和溶菌酶活性，最佳MHA添加水平分别为5.83、5.59和6.07克/千克饲料（以4.01克/千克蛋氨酸为基础）。本研究表明，MHA对鱼类肠道健康状况具有积极影响，且基于这些积极作用，其效果优于DL-蛋氨酸。
