Colonic mucosal protection is provided by the mucus gel, mainly
composed of mucins. Several factors can modulate the formation
and the secretion of mucins, and among them butyrate, an endproduct of carbohydrate fermentation. However, the specific
effect of butyrate on the various colonic mucins, and the
consequences in terms of the mucus layer thickness are not
known. Our aim was to determine whether butyrate modulates
colonic MUC genes expression in vivo and whether this results in
changes in mucus synthesis and mucus layer thickness. Mice
received daily for 7 days rectal enemas of butyrate (100 mM)
versus saline. We demonstrated that butyrate stimulated the
gene expression of both secreted (Muc2) and membrane-linked
(Muc1, Muc3, Muc4) mucins. Butyrate especially induced a 6-fold
increase in Muc2 gene expression in proximal colon. However,
butyrate enemas did not modify the number of epithelial cells
containing the protein Muc2, and caused a 2-fold decrease in the
thickness of adherent mucus layer. Further studies should help
understanding whether this last phenomenon, i.e. the decrease
in adherent mucus gel thickness, results in a diminished
protective function or not.