The bugs that live inside our intestines may play a role beyond just regulating digestion -- a new study in mice suggests they could also impact the body's immune system.
Mayo Clinic and University of Illinois at Urbana-Champaign researchers found that having an overabundance of a certain kind of gut bacteria -- more than what is considered typical -- could actually lead to autoimmune diseases like painful rheumatoid arthritis in people who may be susceptible to the disease.
"This study is an important advance in our understanding of the immune system disturbances associated with rheumatoid arthritis," Dr. Eric Matteson, M.D., chairman of rheumatology at Mayo Clinic, who was not involved in the study, said in a statement. "While we do not yet know what the causes of this disease are, this study provides important insights into the immune system and its relationship to bacteria of the gut, and how these factors may affect people with genetic susceptibilities to disease."
The study, which was published in the journal PLoS ONE, was conducted in mice that were engineered to have a gene that is known to predispose to rheumatoid arthritis. Researchers also engineered mice to have a gene that made them resistant to rheumatoid arthritis, so that they could compare the gut flora of both kinds of mice.
The researchers also found that female mice had a tripled risk of developing an autoimmune disease compared with male mice, which they said is similar to how women are more likely to develop rheumatoid arthritis than men.
HuffPost earlier reported that there are around 1.5 million people in the U.S. currently living with rheumatoid arthritis, according to Centers for Disease Control statistics.
"The next step for us is to show if bugs in the gut can be manipulated to change the course of disease," study researcher Veena Taneja, Ph.D., of the Mayo Clinic, said in a statement.
Gut bacteria may play a role in other conditions too, according to recent studies. MSNBC reported on a story last year in the journal Gastroenterology, which showed that disrupting the gut flora of mice could actually change their moods.
And the Los Angeles Times reported on a 2009 study in the journal Science Translational Medicine, which showed that when you eat a diet that is high in sugar and fat, it could actually change what kinds of bacteria live in your gut. This change in flora could then impact the ease with which you gain weight -- and the difficulty in losing it, according to the Los Angeles Times.