AUTHOR=Lu Zhiyuan , Feng Lin , Jiang Wei-Dan , Wu Pei , Liu Yang , Jiang Jun , Kuang Sheng-Yao , Tang Ling , Li Shu-Wei , Liu Xiang-An , Zhong Cheng-Bo , Zhou Xiao-Qiu TITLE=Mannan Oligosaccharides Application: Multipath Restriction From Aeromonas hydrophila Infection in the Skin Barrier of Grass Carp (Ctenopharyngodon idella) JOURNAL=Frontiers in Immunology VOLUME=Volume 12 - 2021 YEAR=2021 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2021.742107 DOI=10.3389/fimmu.2021.742107 ISSN=1664-3224 ABSTRACT=The objective of this study was to evaluate the efficacy of dietary Mannan oligosaccharides (MOS) supplementation on skin barrier function and the mechanism of on-growing grass carp (Ctenopharyngodon idella). Five hundred-forty grass carp were fed for sixty days from the growing stage with six different level MOS diets (0, 200, 400, 600, 800, 1000 mg kg-1). At the end of the growth trial, the fourteen days Aeromonas hydrophila challenge experiment has proceeded. The obtained data indicate that MOS could: (1) decline skin lesion morbidity after challenged pathogenic bacteria; (2) maintain physical barrier function via improving antioxidant ability, inhibiting excessive apoptosis, and strengthening the tight junction between the epithelial cell and related signaling pathway (Nrf2/Keap1, p38MAPK, and MLCK); (3) regulate immune barrier function by modulating the production of antimicrobial compound and expression of involved cytokines and related signaling pathway (TOR and NFκB); Finally, we concluded that MOS supplementation reinforced the disease resistance and protected fish skin barriers function under infection of Aeromonas hydrophila.