Reactivity of secretory immunoglobulin A against gut bacteria is attenuated by high-fat diet consumption

Secretory immunoglobulin A (SIgA) is predominant antibody secreted into the gut relating to maintain gut homeostasis. In the present study, we focused on the SIgA coating of gut bacteria as a mucosal immune response affecting the gut bacteria following a high-fat diet (HFD). This study newly showed that the level of SIgA coating of gut bacteria was significantly decreased in HFD-fed mice than normal-fat diet (NFD)-fed mice. Furthermore, we found that the relative abundances of gut bacteria were significantly negatively or positively correlated with the level of SIgA coating of gut bacteria in NFD-fed and HFD-fed mice. Our observations suggest that a decrease in the level of SIgA coating of the gut bacteria through a HFD might relate to HFD-induced changes in bacterial composition

Cyclic nigerosylnigerose ameliorates DSS-induced colitis with restoration of goblet cell number and increase in IgA reactivity against gut microbiota in mice

Cyclic nigerosylnigerose (CNN) is a cyclic oligosaccharide. Oral administration of CNN promotes immunoglobulin A (IgA) secretion in the gut. IgA is a major antibody secreted into the gut and plays a crucial role in suppressing gut inflammation due to commensal gut microbiota. To investigate the effect of administration of CNN to promote IgA secretion on gut inflammation, experimental colitis was induced with dextran sulfate sodium (DSS) in Balb/c mice after 6 weeks of CNN pre-feeding. The severity of colitis was evaluated based on a disease activity index (DAI), the gene expression of inflammatory cytokines, and a histological examination. The CNN-treated mice with DSS-induced colitis (CNN-DSS group) showed significantly lower DAI scores and mRNA levels of interleukin-1 compared with the CNN-untreated mice with DSS-induced colitis (DSS group). Histological examination of the colon revealed that the pathological score was significantly lower in the CNN-DSS group compared with the DSS group due to the reduced infiltration of immune cells. The number of goblet cells was significantly higher in the CNN-DSS group compared with the DSS group. The IgA concentration and the ratio of microbiota coated with IgA were evaluated in the cecal content. Although there was no difference in the IgA concentration among groups, a higher proportion of cecal microbiota were coated with IgA in the CNN-DSS group compared with that in the DSS group. These results suggest that CNN might preserve goblet cells in the colon and promote IgA coating of gut microbiota, which synergistically ameliorate gut inflammation in mice with DSS-induced colitis

Reactivity of secretory immunoglobulin A against gut bacteria is attenuated by high-fat diet consumption

Secretory immunoglobulin A (SIgA) is predominant antibody secreted into the gut relating to maintain gut homeostasis. In the present study, we focused on the SIgA coating of gut bacteria as a mucosal immune response affecting the gut bacteria following a high-fat diet (HFD). This study newly showed that the level of SIgA coating of gut bacteria was significantly decreased in HFD-fed mice than normal-fat diet (NFD)-fed mice. Furthermore, we found that the relative abundances of gut bacteria were significantly negatively or positively correlated with the level of SIgA coating of gut bacteria in NFD-fed and HFD-fed mice. Our observations suggest that a decrease in the level of SIgA coating of the gut bacteria through a HFD might relate to HFD-induced changes in bacterial composition