Impairment of intestinal barrier associated with the alternation of intestinal flora and its metabolites in cow's milk protein allergy

Cow's milk protein allergy (CMPA), one of the most prevalent food allergies, seriously affects the growth and development of infants and children with the rising incidence and prevalence. The dysbiosis of intestinal flora acts to promote disease including allergic disease. Therefore, studying the role of intestinal flora in allergic diseases holds great promise for developing effective strategies to mitigate the risk of food allergies. This study aims to elucidate the role of disrupted intestinal flora and its metabolites in children with CMPA.16S rDNA sequence analysis was applied to characterize the changes in the composition of intestinal flora. The findings revealed heightened diversity of intestinal flora in CMPA, marked by decreased abundance of Firmicutes and Bacteroidetes, and increased abundance of Proteobacteria and Actinobacteria. Furthermore, metabolite analysis identified a total of 1245 differential metabolites in children with CMPA compared to those in healthy children. Among these, 765 metabolites were down-regulated, while 480 were up-regulated. Notably, there were 10 negative differential metabolites identified as bile acids and derivatives, including second bile acids, such as deoxycholic acid, ursodeoxycholic acid and isoursodexycholic acid. The intestinal barrier was further analyzed and showed that the enterocytes proliferation and the expression of Claudin-1, Claudin-3 and MUC2 were down-regulated with the invasion of biofilm community members in the CMPA group. In summary, these findings provide compelling evidence that food allergies disrupt intestinal flora and its metabolites, consequently damaging the intestinal barrier's integrity to increase intestinal permeability and immune response.