The intestinal tract is inhabited by a large and diverse community of microbes collectively referred to as the gut microbiota. While the gut microbiota provides important benefits to its host, especially in metabolism and immune development, disturbance of the microbiota-host relationship is associated with numerous chronic inflammatory diseases, including
inflammatory bowel disease and the group of
obesity-associated diseases collectively referred to as
metabolic syndrome. A primary means by which the intestine is protected from its microbiota is via multi-layered mucus structures that cover the intestinal surface, thereby allowing the vast majority of gut bacteria to be kept at a safe distance from epithelial cells that line the intestine. Thus, agents that disrupt mucus-bacterial interactions might have the potential to promote diseases associated with gut
inflammation. Consequently, it has been hypothesized that emulsifiers,
detergent-like molecules that are a ubiquitous component of processed foods and that can increase bacterial translocation across epithelia in vitro, might be promoting the increase in
inflammatory bowel disease observed since the mid-twentieth century. Here we report that, in mice, relatively low concentrations of two commonly used emulsifiers, namely
carboxymethylcellulose and polysorbate-80, induced low-grade
inflammation and
obesity/
metabolic syndrome in wild-type hosts and promoted robust
colitis in mice predisposed to this disorder. Emulsifier-induced
metabolic syndrome was associated with microbiota encroachment, altered species composition and increased pro-inflammatory potential. Use of germ-free mice and faecal transplants indicated that such changes in microbiota were necessary and sufficient for both low-grade
inflammation and
metabolic syndrome. These results support the emerging concept that perturbed host-microbiota interactions resulting in low-grade
inflammation can promote adiposity and its associated metabolic effects. Moreover, they suggest that the broad use of
emulsifying agents might be contributing to an increased societal incidence of
obesity/
metabolic syndrome and other chronic inflammatory diseases.