Dietary Zn proteinate with moderate chelation strength alleviates heat stress-induced intestinal barrier function damage by promoting expression of tight junction proteins via the A20/NF-κB p65/MMP-2 pathway in the jejunum of broilers

Background The aim of this study was to determine whether and how Zn proteinate with moderate chelation strength(Zn-Prot M) can alleviate heat stress(HS)-induced intestinal barrier function damage of broilers.A completely randomized design was used for comparatively testing the effects of Zn proteinate on HS and non-HS broilers.Under high temperature(HT),a1(Control,HT-CDN)+2(Zn source) × 2(added Zn level) factorial arrangement of treatments was used.The 2 added Zn sources were Zn-Prot M and Zn sulfate(ZnS),and the 2 added Zn levels were 30and 60 mg/kg.Under normal temperature(NT),a CON group(NT-CON) and pair-fed group(NT-PF) were included.Results The results showed that HS significantly reduced mRNA and protein expression levels of claudin-1,occludin,junctional adhesion molecule-A(JAMA),zonula occludens-1(ZO-1) and zinc finger protein A20(A20) in the jejunum,and HS also remarkably increased serum fluorescein isothiocyanate dextran(FITC-D),endotoxin and interleukin(IL)-1βcontents,serum diamine oxidase(DAO) and matrix metalloproteinase(MMP)-2 activities,nuclear factor kappa-B(NF-κB) p65 mRNA expression level,and protein expression levels of NF-κB p65 and MMP-2 in the jejunum.However,dietary supplementation with Zn,especially organic Zn as Zn-Prot M at 60 mg/kg,significantly decreased serum FITC-D,endotoxin and IL-1β contents,serum DAO and MMP-2 activities,NF-κB p65 mRNA expression level,and protein expression levels of NF-κB p65 and MMP-2 in the jejunum of HS broilers,and notably promoted mRNA and protein expression levels of claudin-1,ZO-1 and A20.Conclusions Our results suggest that dietary Zn,especially 60 mg Zn/kg as Zn-Prot M,can alleviate HS-induced intestinal barrier function damage by promoting the expression of TJ proteins possibly via induction of A20-mediated suppression of the NF-κB p65/MMP-2 pathway in the jejunum of HS broilers.