Dietary fat-induced taurocholic acid production promotes pathobiont and colitis in IL-10(−/−) mice

The composite human microbiome of Western populations has likely changed over the past century, brought on by new environmental triggers that often have a negative impact on human health(1). Here we show that consumption of a diet high in saturated (milk derived)-fat (MF), but not polyunsaturated (safflower oil)-fat (PUFA), changes the conditions for microbial assemblage and promotes expansion of a low abundance, sulfite-reducing pathobiont, Bilophila wadsworthia(2). This was associated with a pro-inflammatory T(H)1 immune response and increased incidence of colitis in genetically susceptible IL-10(−/−), but not wild type mice. These effects are mediated by MF-promoted taurine-conjugation of hepatic bile acids, which increases the availability of organic sulfur used by sulfite-reducing microbes like B. wadsworthia. When mice were fed a low-fat (LF) diet supplemented with taurocholic, but not with glycocholic acid, for example, a bloom of B. wadsworthia and development of colitis were observed in IL10(−/−) mice. Together these data show that dietary fats, by promoting changes in host bile acid composition, can dramatically alter conditions for gut microbial assemblage, resulting in dysbiosis that can perturb immune homeostasis. The data provide a plausible mechanistic basis by which Western type diets high in certain saturated fats might increase the prevalence of complex immune-mediated diseases like inflammatory bowel diseases in genetically susceptible hosts.