Deng Junming, Zhang Xindang, Lin Beibei, Mi Haifeng, Zhang Lu
College of Fisheries, Guangdong Ocean University, Zhanjiang, 524088, China; College of Animal Science and Technology, Yunnan Agricultural University, Kunming, 650201, China.
College of Animal Science and Technology, Yunnan Agricultural University, Kunming, 650201, China; College of Fisheries, Henan Normal University, Xinxiang, 453007, China.
Fish Shellfish Immunol. 2023 Oct;141:109041. doi: 10.1016/j.fsi.2023.109041. Epub 2023 Aug 30.
Arabinoxylan (AX) has been deemed as an antinutritional factor, but limited information has addressed the effects of dietary AX on intestinal health of fish. The present study investigated the effects of dietary AX on intestinal mucosal physical and immunological barriers of rainbow trout (Oncorhynchus mykiss). Five isoproteic and isolipidic experimental diets (AXE, AX0, AX2.5, AX5 and AX10) were formulated to contain 0.03% arabinoxylanase as well as 0%, 2.5%, 5% and 10% AX, respectively. Each diet was randomly distributed to triplicate groups of 35 juvenile (average weight 3.14 ± 0.02 g) per tank in a rearing system maintained at 17 ± 1 °C for 9 weeks. Dietary AX supplementation regardless of inclusion levels significantly (P < 0.05) depressed the growth performance and feed utilization. The plasma endothelin-1 and d-lactic acid contents as well as diamino oxidase activity were significantly higher in fish fed diet AX10 compared to fish fed diet AX0. Dietary inclusion of 5-10% AX resulted in decreased intestinal villus height, goblet cell number and desmosome density, increased crypt depth, short and irregular microvilli, widened intercellular space; down-regulated the mRNA levels of occludin in hindgut, claudin3 and ZO-1 in foregut and midgut, but up-regulated the mRNA levels of claudin12 and claudin15 in midgut as well as claudin23 in foregut, midgut and hindgut. Furthermore, dietary 5-10% AX supplementation decreased the midgut and hindgut complement 3, complement 4 and sIgT contents as well as the midgut IgM and hindgut IL-10 contents. Conversely, the hindgut TNF-α and IL-6 contents increased with the rising dietary AX level. RT-qPCR demonstrated that the pro-inflammatory cytokines (IL-1β, IL-6, IL-8, IL-12β, IFN-γ, and TNF-α) and pIgR mRNA levels in midgut and hindgut were up-regulated by dietary AX inclusion of 5-10% AX. Meanwhile, the mRNA levels of p38 MAPK, IκBα, and NF-κB p65 in midgut and hindgut raised gradually with the increasing dietary AX content. The Western blot results showed that the protein expression levels of p38 MAPK and NF-κB generally increased with the rising dietary AX content. Dietary treatment with 0.03% arabinoxylanase did not affect the growth performance and intestinal health of rainbow trout (P > 0.05). In conclusion, excessive dietary AX inclusion (5-10%) increased the intestinal permeability and induced the intestinal inflammatory response via activating MAPK/NF-κB signaling pathway, and ultimately damaged the intestinal barrier function of rainbow trout.
阿拉伯木聚糖（AX）被认为是一种抗营养因子，但关于日粮AX对鱼类肠道健康影响的信息有限。本研究调查了日粮AX对虹鳟（Oncorhynchus mykiss）肠道黏膜物理屏障和免疫屏障的影响。配制了五种等蛋白、等脂的实验饲料（AXE、AX0、AX2.5、AX5和AX10），分别含有0.03%的阿拉伯木聚糖酶以及0%、2.5%、5%和10%的AX。将每种饲料随机分配到养殖系统中，每个水箱中饲养35尾幼鱼（平均体重3.14±0.02 g），每组设三个重复，饲养温度保持在17±1℃，为期9周。无论AX添加水平如何，日粮中添加AX均显著（P<0.05）降低了生长性能和饲料利用率。与饲喂AX0日粮的鱼相比，饲喂AX10日粮的鱼血浆内皮素-1、d-乳酸含量以及二胺氧化酶活性显著更高。日粮中添加5-10%的AX导致肠道绒毛高度、杯状细胞数量和桥粒密度降低，隐窝深度增加，微绒毛短且不规则，细胞间隙增宽；后肠中闭合蛋白、前肠和中肠中紧密连接蛋白3和闭锁小带蛋白-1的mRNA水平下调，但中肠中紧密连接蛋白12和紧密连接蛋白15以及前肠、中肠和后肠中紧密连接蛋白23的mRNA水平上调。此外，日粮中添加5-10%的AX降低了中肠和后肠补体3、补体4和分泌型免疫球蛋白T含量以及中肠免疫球蛋白M和后肠白细胞介素-10含量。相反，后肠肿瘤坏死因子-α和白细胞介素-6含量随着日粮AX水平的升高而增加。实时定量聚合酶链反应（RT-qPCR）表明，日粮中添加5-10%的AX上调了中肠和后肠中促炎细胞因子（白细胞介素-1β、白细胞介素-6、白细胞介素-8、白细胞介素-12β、干扰素-γ和肿瘤坏死因子-α）和多聚免疫球蛋白受体（pIgR）的mRNA水平。同时，中肠和后肠中p38丝裂原活化蛋白激酶（p38 MAPK）、核因子κB抑制蛋白α（IκBα）和核因子κB p65的mRNA水平随着日粮AX含量的增加而逐渐升高。蛋白质免疫印迹结果显示，p38 MAPK和核因子κB的蛋白质表达水平一般随着日粮AX含量的升高而增加。用0.03%阿拉伯木聚糖酶进行日粮处理对虹鳟的生长性能和肠道健康没有影响（P>0.05）。总之，日粮中过量添加AX（5-？10%）会增加肠道通透性，并通过激活丝裂原活化蛋白激酶/核因子κB信号通路诱导肠道炎症反应，最终损害虹鳟的肠道屏障功能。 （注：原文中“AX10”处似乎多了个问号，译文已按正确理解翻译。）
