Editors' ChoiceHost-Microbe Interactions

Another reason to eat more fiber

Sci. Signal.  16 Aug 2016:
Vol. 9, Issue 441, pp. ec184
DOI: 10.1126/scisignal.aai7897

When gut bacteria ferment dietary fiber, they produce short-chain fatty acids (SCFAs), which are both an energy source for intestinal epithelial cells and important modulators of host physiology and immunity. SCFAs can affect host metabolic pathways, activate G protein–coupled receptors (GPCRs), and inhibit histone deacetylases (HDACs). Kim et al. found that SCFAs enhanced the generation of antibody-producing B cells. Feeding mice a high-fiber diet or the SCFA propionate increased the amount of immunoglobulins in the serum and intestinal lumen and boosted the numbers of antibody-secreting B cells in the intestine and the number of immunoglobulin A (IgA)–coated bacteria in the colon. In vitro, the SCFAs acetate, propionate, and butyrate each stimulated the differentiation of naïve mouse or human B cells into antibody-secreting plasma cells, and acetate promoted the production of IgA and IgG and the expression of genes involved in B cell differentiation. Experiments with mouse B cells indicated that these effects were not caused by SCFA-mediated activation of GPCRs. Each of the three SCFAs increased histone acetylation in cultured mouse B cells, and feeding mice propionate or dietary fiber increased histone acetylation in B cells in vivo. SCFAs also increased acetyl-CoA production, glycolysis, mitochondrial respiration, and the production of lipid droplets in primary mouse B cells. These metabolic changes may aid in the energetically costly process of antibody production. Last, dietary fiber and propionate each reduced the susceptibility of mice to Citrobacter rodentium infection and increased the production of antibodies specific to C. rodentium after exposure to this pathogen. Thus, SCFAs act through multiple mechanisms to promote the ability of B cells to produce antibodies.

M. Kim, Y. Qie, J. Park, C. H. Kim, Gut microbial metabolites fuel host antibody responses. Cell Host Microbe 20, 202–214 (2016). [PubMed]