This study investigated the effects of
choline on intestinal mucosal immune and the possible mechanisms in fish by feeding juvenile Jian carp (Cyprinus carpio var. Jian) with graded levels of dietary
choline (165-1820 mg/kg diet) for 65 days. The results firstly showed that
choline deficiency induced inflammatory infiltration in the proximal intestine (PI), mid intestine (MI) and distal intestine (DI) of fish. Meanwhile, compared with the optimal
choline group,
choline deficiency decreased the activities of
lysozyme and
acid phosphatase, contents of
complement 3 and
IgM in the intestine, downregulated the
mRNA levels of
antimicrobial peptides (
liver-expressed antimicrobial peptide (LEAP) 2A and
defensin-3 in the PI and MI, LEAP-2B and
hepcidin in the PI, MI and DI), anti-inflammatory
cytokines (
interleukin (IL) 10 and
transforming growth factor β2 in the PI, MI and DI), and signaling molecule IκB in the PI, MI and DI; while upregulated the
mRNA levels of pro-inflammatory
cytokines (IL-6a and
tumor necrosis factor α in the MI and DI,
interferon γ2b in the PI and MI, IL-1β and IL-6b in the PI, MI and DI), and signaling molecules (
Toll-like receptor 4 in the MI, myeloid differentiation primary response 88 in the PI and MI,
Janus kinase 3 and
tyrosine kinase 2 in the MI and DI,
nuclear factor kappa B (NF-κB), signal transducers and activators of transcription (STAT) 4 and STAT5 in the PI, MI and DI) of juvenile Jian carp, further indicating that
choline deficiency caused
inflammation and immunity depression in the intestine of fish. But
choline deficiency decreased the PI IL-6a
mRNA level, and increased the DI LEAP-2A and defensin-3
mRNA levels with unknown reasons. Furthermore, dietary
choline deficiency downregulated
mRNA levels of tight junction (TJ)
proteins (
claudin 3c in the PI and MI,
claudin 7,
claudin 11 and
occludin in the PI, MI and DI) and signaling molecule
mitogen-activated protein kinases p38 in the PI, MI and DI of juvenile Jian carp, whereas upregulated the
mRNA levels of
claudin 3b in the MI and DI, and
claudin 3c in the DI. Moreover, the excessive
choline exhibited negative effects on intestinal immunity and TJ
proteins that were similar to the
choline deficiency. In summary, dietary
choline deficiency or excess caused the depression of intestinal mucosal immune by inducing
inflammation and dysfunction of the intestinal physical barrier, and regulating related signaling molecules of fish.