Researchers in Japan have carried out a mouse study that reveals a mechanism through which gut bacteria influence the immune system's role in reducing inflammation. The mechanism works via a fatty acid known as butyrate, which results when the bacteria digest dietary fiber.
The researchers, led by a group from the RIKEN Center for Integrative Medical Sciences (IMS-RCAI) in Kanagawa, believe their findings make a case for using butyrate to treat inflammatory bowel diseases, such as Crohn's disease.
There is already evidence that the gut bacteria in patients with inflammatory bowel disease do not make butyrate, and that they have low levels of the fatty acid in their gut.
But those studies concluded that the reason butyrate helped to reduce inflammation was because it acted as an energy source for cells lining the colon.
New findings make a case for using butyrate to treat inflammatory bowel diseases, such as Crohn's disease, researchers say.
This new study is the first to suggest an alternative explanation - a molecular mechanism by which butyrate influences the production of cells that calm down the effect of other cells - by reducing inflammation response.
In a report published in a recent online issue of Nature, the researchers describe how, by switching on genes ("epigenetic switching") the fatty acid causes the immune system to produce more regulatory T cells in the gut.
They showed how it acts on precursor or "naïve" T cells to promote their differentiation into regulatory T cells and that this occurred by changing expression of the genes responsible for turning the naïve T cells into regulatory T cells.
Potential to treat IBD, allergy and autoimmune disease
The researchers also found that the guts of mice with colitis increased in regulatory T cells, and their inflammatory symptoms improved after they were given butyrate in their diets.
Study leader Dr. Hiroshi Ohno, of the Laboratory for Epithelial Immunobiology at RIKEN, says:
He says butyrate is a natural and safe therapy, plus it is cheap, making it an attractive, affordable option for both patients and society.
"Regulatory T cells are important for the containment of excessive inflammatory responses as well as autoimmune disorders. Therefore, these findings could be applicable for the prevention and treatment of inflammatory bowel disease (IBD), allergy and autoimmune disease."
The study adds to an increasing pile of evidence about the important role that gut microbes play in human health, for better and for worse.
For example, at a recent Society for General Microbiology conference, UK researchers presented evidence suggesting gut bacteria may cause cancer by disarming the immune system.