Western diets that are high in sugars, fats, and processed foods have been linked to a wide variety of health ailments. Now, researchers have determined that Western diets can also disrupt the crucial barrier in the gastrointestinal tract known as the gut mucosa. This disruption can raise an individual's risk of inflammation and infectious disease. Scientists have also identified a gut microbe called Blautia that has an important role in shielding the gut mucosa. The findings have been reported in Nature Communications.
"Our results contribute to an increased understanding of how the intestinal bacteria and the mucus layer work together, which may eventually lead to new treatment strategies for diseases linked to the Western diet such as the inflammatory bowel disease ulcerative colitis," said first study author Sandra Holmberg, a graduate student at Umeå University.
We need the trillions of microbes in our gut to help us digest food and absorb nutrients. The gut microbiome also produces important bioactive molecules during metabolic processes. But our body also needs to be protected from all of those microbes, and the gut mucosa helps create a defensive barrier that should be impermeable to the gut microbiome. When that barrier is weakened or damaged, serious problems can arise, and the risks of inflammation and infection rise.
Diet has been shown in previous research to affect the composition of the gut microbiome and the mucosal barrier. Western diets lead to a lowering of mucus production in the guts of mouse models, for example, and a weakening of the mucosal barrier.
Researchers have now analyzed the impact of dietary changes on the gut mucosa. Healthy volunteers increased the amount of fiber they consumed every day by ten grams, or the equivalent of around four apples or two cups of oatmeal. The investigators collected gut microbes from the study participants at the start and end of the study. These microbial samples were then implanted into mice that were fed a Western diet low in fiber.
Animals that received gut microbes collected at the start of the study, before added fiber intake, showed evidence of mucosal damage. But in the mice that received later microbial samples taken after the increased intake of fiber, the mucosal layer remained intact.
"The result highlights the significant role that dietary fiber has for our intestinal bacteria, which in turn contributes to maintaining the important mucus barrier," said study co-author Rachel Feeney, a doctoral candidate at Umeå University.
Additional work showed that levels of a bacterium called Blautia were higher after fiber consumption increased, and Blautia was linked to healthy gut mucosa in mice.
When a group of mice was fed a Western diet along with Blautia microbes, there was improvement in gut mucus function, similar to the effects of a transplant of gut microbes after a high-fiber diet.
Finally, the researchers showed that molecules called short-chain fatty acids (SCFAs) are released by Blautia, and are also able to stimulate the release of mucus. This seems to explain how the bacterium can trigger mucus production even when fiber intake is low. A variety of gut microbes that are linked to good health have been shown to release SCFAs, and Blautia appears to be another.
Blautia bacteria were also able to relieve symptoms of intestinal infection in a mouse model.
"Therefore, we concluded that the Blautia may also have protective effects in case of infection," noted study co-author Vishnu Prasoodanan, a postdoctoral fellow at Umeå University.
Sources: Umea University, Nature Communications
