Dietary choline enhanced skin immune response of juvenile grass carp might be related to STAT3 and NF-kB signaling pathway (Ctenopharyngodon idella)

Abstract Background: Choline is an indispensable vitamin of fish; which deficiency affects fish health. Fish health is affected by skin immune function. Hence, the present study was conducted to investigate the effects of dietary choline on skin immune function as well as underlying mechanisms of juvenile grass carp (Ctenopharyngodon idella).Results: The results exhibited that dietary choline (1) advanced the content of phosphatidylcholine (PC), betaine, and choline in grass crap skin (P < 0.05), up-regulated the mRNA abundance of choline transporter CHT1, CTL5, and CTL1 indicating that dietary choline could increase the contents of choline might be connected with choline transporters in the grass carp skin; (2) receded skin lesion and increased the level of IgM, C4, C3, and the activities of acid phosphatase (ACP) and lysozyme activity (LZ), raised mucin2, β-defensin, hepcidin, and LEAP-2B mRNA abundance (rather than LEAP-2A), down-regulated pro-inflammatory cytokines mRNA abundance (IFN-γ2, IL-15, TNF-α, IL-6, IL-12P40, and IL-1β) in skin of juvenile grass carp (P < 0.05), up-regulated anti-inflammatory cytokines mRNA abundance ( IL-10, IL-4/13A, TGF-β1, IL-11, and IL-4/13B) in grass crap skin (P < 0.05) demonstrating that choline enhanced the skin immune function; (3) down-regulated the mRNA abundance of IKKγ, NF-κBp52, , IKKβ, c-Rel, NF-κBp65, STAT3b2, STAT3b1 JAK1, and JAK2 as well as protein level of NF-κBp65 and p-STAT3 Tyr705 in nucleus, inhibited the mRNA and protein level of IkBα (P < 0.05), indicating that choline enhanced immune function might be relevant to JAK/STAT3 and NF-κB signaling pathway in fish skin.Conclusions: In conclusion, choline enhanced the skin immune function might be relate to JAK/STAT3 and NF-κB signaling molecules in fish. Furthermore, based on immune indices of grass carp (9.28-108.97g) skin (C3 and IgM contents as well as ACP activities), the choline requirements were estimated to be 1475.81, 1364.24, and 1574.37 mg/kg diet, respectively.