Lu Zhi-Yuan, Feng Lin, Jiang Wei-Dan, Wu Pei, Liu Yang, Jin Xiao-Wan, Ren Hong-Mei, Kuang Sheng-Yao, Li Shu-Wei, Tang Ling, Zhang Lu, Mi Hai-Feng, Zhou Xiao-Qiu
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.
Antioxidants (Basel). 2022 Apr 20;11(5):806. doi: 10.3390/antiox11050806.
Mannan oligosaccharides (MOS) are a type of functional oligosaccharide which have received increased attention because of their beneficial effects on fish intestinal health. However, intestinal structural integrity is a necessary prerequisite for intestinal health. This study focused on exploring the protective effects of dietary MOS supplementation on the grass carp’s (Ctenopharyngodon idella) intestinal structural integrity (including tight junction (TJ) and adherent junction (AJ)) and its related signalling molecule mechanism. A total of 540 grass carp (215.85 ± 0.30 g) were fed six diets containing graded levels of dietary MOS supplementation (0, 200, 400, 600, 800 and 1000 mg/kg) for 60 days. Subsequently, a challenge test was conducted by injection of Aeromonas hydrophila for 14 days. We used ELISA, spectrophotometry, transmission electron microscope, immunohistochemistry, qRT-PCR and Western blotting to determine the effect of dietary MOS supplementation on intestinal structural integrity and antioxidant capacity. The results revealed that dietary MOS supplementation protected the microvillus of the intestine; reduced serum diamine oxidase and d-lactate levels (p < 0.05); enhanced intestinal total antioxidant capacity (p < 0.01); up-regulated most intestinal TJ and AJ mRNA levels; and decreased GTP-RhoA protein levels (p < 0.01). In addition, we also found several interesting results suggesting that MOS supplementation has no effects on ZO-2 and Claudin-15b. Overall, these findings suggested that dietary MOS supplementation could protect intestinal ultrastructure, reduce intestinal mucosal permeability and maintain intestinal structural integrity via inhibiting MLCK and RhoA/ROCK signalling pathways.
甘露寡糖（MOS）是一种功能性寡糖，因其对鱼类肠道健康的有益作用而受到越来越多的关注。然而，肠道结构完整性是肠道健康的必要前提。本研究聚焦于探讨日粮中添加MOS对草鱼（Ctenopharyngodon idella）肠道结构完整性（包括紧密连接（TJ）和黏附连接（AJ））及其相关信号分子机制的保护作用。总共540尾草鱼（215.85±0.30克）投喂六种含有不同梯度MOS添加量（0、200、400、600、800和1000毫克/千克）的日粮，持续60天。随后，通过注射嗜水气单胞菌进行为期14天的攻毒试验。我们采用酶联免疫吸附测定（ELISA）、分光光度法、透射电子显微镜、免疫组织化学、实时定量聚合酶链反应（qRT-PCR）和蛋白质免疫印迹法来确定日粮中添加MOS对肠道结构完整性和抗氧化能力的影响。结果显示，日粮中添加MOS可保护肠道微绒毛；降低血清二胺氧化酶和d-乳酸水平（p<0.05）；增强肠道总抗氧化能力（p<0.01）；上调大多数肠道TJ和AJ的mRNA水平；并降低GTP-RhoA蛋白水平（p<0.01）。此外，我们还发现了一些有趣的结果，表明添加MOS对ZO-2和Claudin-15b没有影响。总体而言，这些发现表明，日粮中添加MOS可通过抑制肌球蛋白轻链激酶（MLCK）和RhoA/ROCK信号通路来保护肠道超微结构、降低肠道黏膜通透性并维持肠道结构完整性。
