Undaria pinnatifida fucoidan contributes to anti-inflammation activity of Bacteroides in fiber-deficient mice via modulation of gut microbiota and protection of intestinal barrier integrity

Bacteroides as potential probiotics has several health benefits to the host, but its practical application faces many challenges due to its inherent properties. In this study, Bacteroides strains isolated from human feces alleviated colonic inflammation in mice, as evidenced by increased colon length and reduced tissue damage. Further study showed that anti-inflammation activity of Bacteroides strains was disturbed by dietary fiber deficiency (FD), which disrupted the balance between gut microbiota and colonic mucus layer, leading to a thinning of colonic mucus layer. A combination of Bacteroides strains and Undaria pinnatifida fucoidan (UPF) better alleviated colonic inflammation than either of them, including increases in the densities of goblet cells and glycoproteins and reduction in intestinal epithelial damage, pro-inflammatory cytokines and oxidative stress. The underlying mechanisms can be attributed to that UPF-induced alterations of mucosal microbiota cannot only directly benefit host health but also create an ecological condition that facilitates Bacteroides strains exert their healthy properties. In addition, both Bacteroides strains and UPF improved FD-induced lipid metabolism abnormality, mainly involving glycerophospholipid metabolism pathway. This study suggests that the application of Bacteroides has certain limitations, and UPF can be developed as a probiotic adjuvant for Bacteroides to enhance human health.