Phytochemical-induced mucin accumulation in the gastrointestinal lumen is independent of the microbiota

The mucus layer is critical to gastrointestinal health and ecology. Dietary phytochemicals are well documented to stimulate mucus production and secretion, but the underlying mechanism and effects on gut health are poorly understood. We fed germ-free and conventional mice diets containing approximately 0.4% of polyphenols per gram to determine if the phytochemical-induced accumulation of mucin in the gastrointestinal lumen is dependent on the microbiota. In addition, we assess how increased mucin shapes microbial communities in conventional mice. Germ-free mice receiving a pea (Pisum sativuum) seed coat proanthocyanidin-containing diet (PA) had greater levels of fecal mucin compared to the non-proanthocyanidin-containing (NPA) pea seed coat diet control (P < 0.05), confirming that fecal mucin accumulation is independent of the gut microbiota. Conventional mice fed the PA diet and a red osier dogwood (ROD; Cornus sericea) extract diet (DW) had higher mucin levels compared to a control diet without phytochemicals (P < 0.01 and P < 0.05, respectively). The increase in luminal mucin was associated with consistent increases in bacterial taxa belonging to Lachnospiraceae and [Clostridium] leptum species and a decrease in Romboutsia species. We conclude that phytochemicals have the ability to alter gut microbial ecology by increasing the amount of mucin in the gastrointestinal lumen.