The Microbial Metabolites, Short-Chain Fatty Acids, Regulate Colonic T _reg Cell Homeostasis

Protecting the Guts

Regulatory T cells (T _regs ) in the gut are important sentinels in maintaining the peace between our gut and its trillions of resident bacteria and have been shown to be regulated by specific strains of bacteria in mouse models. Smith et al. (p. 569 , published online 4 July; see the Perspective by Bollrath and Powrie ) asked whether metabolite(s) generated by resident bacterial species may regulate T _regs in the gut. Indeed, short-chain fatty acids (SCFAs), bacterial fermentation products of dietary fibers produced by a range of bacteria, restored colonic T _reg numbers in mice devoid of a gut microbiota and increased T _reg numbers in colonized mice. The effects of SCFAs on T _regs were mediated through GPCR43, a receptor for SCFAs, which is expressed on colonic T _regs . Mice fed SCFAs were protected against experimentally induced colitis in a manner that was dependent on GPR43-expressing T _regs .