Protective effect of probiotics on the intestinal mucosal barrier and expression of Zonulin, ZO-1, and MUC1 in the intestinal tissue of yaks

Abstract Background Diarrhea is the most common disease among yak calves in Tibetan breeding farms, primarily caused by E.coli. The study aimed to investigate the preventive effect and mechanisms of probiotics on E. coli-induced intestinal mucosal barrier damage in yak calves. Methods Twenty-four healthy yaks were randomly divided into four groups: control group, model group (E.coli O78), treatment group A (E.coli O78 + probiotics), and treatment group B (E.coli O78 + flufenicol). Serum levels of Zonulin protein were detected by ELISA, intestinal pathological changes were observed by HE staining, and mRNA levels of Zonulin, ZO-1, and MUC1 in intestinal tissues were quantitatively measured by PCR. Results The results showed that compared to the control group, the model group exhibited a significant increase in the serum Zonulin level of calves (P < 0.01). Following probiotic treatment, serum Zonulin levels in group A treatment decreased significantly compared to the model group (P < 0.01), while serum Zonulin levels in group B treatment also showed a significant decrease (P < 0.05). In contrast to the control group, the intestinal mucosa of the model group had extensive infiltration of inflammatory cells, along with degeneration, necrosis, and exfoliation of intestinal epithelial cells. Treatment Group A exhibited an intact intestinal structure with very well-developed intestinal villi and glands, indicating that probiotics had a protective effect on the intestinal mucosal structure and reduced intestinal mucosal damage, improvement of intestinal health in calf yaks. The results of the quantitative fluorescence assay revealed that probiotics significantly reduce the expression of Zonulin mRNA in the intestinal mucosa (P < 0.05), and increase the expression of ZO-1 and MUC1 mRNA (P < 0.05), indicating that probiotics can inhibit or increase the expression of proteins related to intestinal permeability pathways and play a role in the prevention and treatment of E.coli O78 induced diarrhea in yak calves. Conclusion The findings of this study suggest that probiotics can influence proteins which involved in intestinal permeability and have an obvious effect on the treatment and prevention of diarrhea caused by E. coli O78. Probiotics can be used as an alternative drug for the treatment and prevention of such types of diseases.