Citric acid mitigates soybean meal induced inflammatory response and tight junction disruption by altering TLR signal transduction in the intestine of turbot, Scophthalmus maximus L

• Published in: Fish & shellfish immunology 2019-09, Vol.92, p.181-187
• Main Authors: Zhao, Sifan, Chen, Zhichu, Zheng, Jing, Dai, Jihong, Ou, Weihao, Xu, Weiqi, Ai, Qinghui, Zhang, Wenbing, Niu, Jin, Mai, Kangsen, Zhang, Yanjiao
• Format: Article
• Language: English
• Subjects: Animal Feed - analysis; Animals; Citric acid; Citric Acid - administration & dosage; Citric Acid - metabolism; Diet - veterinary; Dietary Supplements - analysis; Fish Proteins - physiology; Flatfishes - immunology; Glycine max - adverse effects; Glycine max - chemistry; Inflammation - chemically induced; Inflammation - metabolism; Intestinal inflammatory response; Intestines - drug effects; Intestines - physiology; Random Allocation; Signal Transduction; Soybean meal; Tight junction protein; Tight Junctions - immunology; Toll-like receptor; Toll-Like Receptors - physiology; Turbot
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2019.06.004

A 12-week feeding trial was conducted to investigate the effect of citric acid on the involvement of TLRs in the soybean meal induced inflammatory response and tight junction disruption in the distal intestine of juvenile turbot (Scophthalmus maximus L.). Four isonitrogenous and isolipidic practical diets were formulated: fish meal-based diet (FM); 40% fish meal protein in FM replaced with soybean meal protein (SBM); SBM + 1.5% citric acid and SBM + 3% citric acid. Compared to the FM, diet SBM significantly increased the gene expression of TLRs (TLR2, TLR3, TLR5b, TLR9, TLR21, TLR22) and MyD88, as well as TLR related molecules (NF-κB, IRF-3, p38 and JNK), which were remarkably reduced by dietary citric acid. Similarly, citric acid supplementation in SBM markedly depressed gene expression of pro-inflammatory cytokines (TNF-α and IFN-γ) and pore-forming tight junction protein Claudin-7, and enhanced gene expression of the anti-inflammatory cytokine TGF-β1 and TJ proteins related to the decrease in paracellular permeability (Claudin-3, Claudin-4, Occludin, Tricellulin and ZO-1). Compared to the SBM, the concentration of IgM and C4 in serum was significantly reduced by dietary citric acid. In brief, dietary citric acid could synchronously inhibit TLRs-dependent inflammatory response regulated by NF-κB and IRF3, as well as cause TLRs-dependent tight junction disruption modulated by p38 and JNK. Therefore, citric acid could function on mitigating soybean meal induced enteropathy in the distal intestine of juvenile turbot. •Dietary citric acid could alleviate the intestinal enteropathy caused by soybean meal in turbot.•Citric acid showed anti-inflammation in intestine via the TLR-mediated activation of NF-κB and IRF-3 signaling pathways.•Citric acid could strengthen the intestinal tight junction via the TLR-mediated p38 and JNK pathways.