Zinc oxide influences mitogen-activated protein kinase and TGF-β1 signaling pathways, and enhances intestinal barrier integrity in weaned pigs

Weaning is the most significant event in the life of pigs and is always related with intestinal disruption. Although it is well known that zinc oxide (ZnO) exerts beneficial effects on the intestinal barrier, the mechanisms underlying these effects have not yet been fully elucidated. We examined whether ZnO protects the intestinal barrier via mitogen-activated protein kinases and TGF-1 signaling pathways. Twelve barrows weaned at 21d of age were randomly assigned to two treatments (0 verus 2200mg Zn/kg from ZnO) for 1 wk. The results showed that supplementation with ZnO increased daily gain and feed intake, and decreased postweaning scour scores. ZnO improved intestinal morphology, as indicated by increased villus height and villus height:crypt depth ratio, and intestinal barrier function, indicated by increased transepithelial electrical resistance and decreased mucosal-to-serosal permeability to 4-ku FITC dextran. ZnO decreased the ratios of the phosphorylated to total JNK and p38 (p-JNK/JNK and p-p38/p38), while it increased the ratio of ERK (p-ERK/ERK). Supplementation with ZnO increased intestinal TGF-1 expression. The results indicate that supplementation with ZnO activates ERK 1/2, and inhibits JNK and p38 signaling pathways, and increases intestinal TGF-1 expression in weaned pigs.