Iron is an important
mineral element for fish. In this study, we investigated the influences of
dietary iron deficiency on intestinal immune function as well as underlying signaling of on-growing grass carp (Ctenopharyngodon idella). Fish were fed with six graded level of
dietary iron for sixty days, and a fourteen days' challenge test under
infection of Aeromonas hydrophila thereafter. Results showed that compared with optimal
iron level,
iron deficiency increased
enteritis morbidity, decreased
lysozyme (LZ) and
acid phosphatase (ACP) activities,
complement 3 (C3), C4 and
immunoglobulin M (
IgM) concentrations and down-regulated
mRNA levels of
hepcidin,
liver expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, Mucin2, β-defensin-1, anti-inflammatory
cytokines transforming growth factor β1 (TGF-β1), TGF-β2,
interleukin 4/13A (IL-4/13A), IL-4/13B,
IL-10,
IL-11 and
IL-15, inhibitor of κBα (IκBα), target of
rapamycin (TOR) and
ribosomal protein S6 kinase 1 (S6K1), whereas up-regulated
mRNA levels of pro-inflammatory
cytokines IL-1β,
interferon γ2 (IFN-γ2),
IL-8,
IL-12p35,
IL-12p40 and
IL-17D,
nuclear factor kappa B (NF-κB) p65, IκB
kinases α (IKKα), IKKβ and eIF4E-binding
protein (4E-BP) in intestine of on-growing grass carp, indicating that
iron deficiency impaired intestinal immune function of fish under
infection of A. hydrophila. Besides,
iron excess also increased
enteritis morbidity and impaired immune function of fish under
infection of A. hydrophila. In addition, the effect of
ferrous fumarate on intestinal immune function of on-growing grass carp is more efficient than
ferrous sulfate. Finally, based on ability against
enteritis, LZ activities in mid intestine and distal intestine, we recommended adding 83.37, 86.71 and 85.39 mg
iron/kg into diet, respectively.