By Pat Anson, Editor
A new study is adding to the growing body of evidence linking gut bacteria to autoimmune and gastrointestinal diseases – research that could lead to new and more effective treatments.
Researchers at the University of Utah used animal studies to show that a certain type of yeast can aggravate symptoms of Inflammatory Bowel Disease (IBD). Their findings, published in the journal Science Translational Medicine, also suggest that allopurinol, a generic drug already on the market, could offer some relief.
IBD is an autoimmune disease characterized by chronic inflammation of the gastrointestinal tract, causing diarrhea, pain, fatigue and weight loss.
For years doctors have used the presence of yeast antibodies, specifically antibodies in the yeast Saccharomyces cerevisiae, to differentiate between Crohn’s disease and ulcerative colitis, two variations of IBD. But it was unclear the role that yeast played in relation to IBD.
“To me this was a huge hole in our understanding of the role of yeast in IBD and our health,” said June Round, PhD, an associate professor in pathology at the University of Utah School of Medicine.
Round and her research team studied two types of yeast that are common in healthy people and IBD patients. Saccharomyces cerevisiae, also called Baker’s yeast, is a prominent organism in the environment and in our food. Rhodotorula aurantiaca is also commonly found in the environment, as well as milk and fruit juice.
Scientists gave each type of yeast to laboratory mice that had been treated with chemicals to induce IBD-like symptoms. The symptoms worsened in mice fed S. cerevisiae, but not in those fed R aurantiaca.
“The mice fed S. cerevisiae experienced significant weight loss, diarrhea, bloody stool, just like a person with IBD,” said Tyson Chiaro, graduate student in Round’s lab.
Further study revealed that the mice fed S. cerevisiae had a higher concentration of nitrogen-rich compounds, called purines, than the mice fed R. aurantiaca. Unlike other yeasts, S. cerevisiae cannot break down purines that accumulate in the intestinal tract and produce uric acid. Uric acid exacerbates inflammation, which may worsen IBD symptoms.
When the mice were treated with allopurinol, a medication used to block the production of uric acid in gout patients, the drug significantly reduced their intestinal inflammation.
“Our work suggests that if we can block the mechanism leading to the production of uric acid, perhaps with allopurinol, IBD patients with a high concentration of S. cerevisiae antibodies may have a new treatment option to reduce inflammation, which could allow the intestine time to heal,” said Round.
E. Coli linked to IBD and spondyloarthritis
Another recent study has helped researchers identify E. coli bacteria found in people with Crohn's disease that can trigger inflammation associated with spondyloarthritis, a painful arthritic condition that affects the spine and joints.
Researchers used fecal samples from IBD patients to identify bacteria in the gut that were coated with antibodies called immunoglobulin-A (IgA) that fight infection. Using flow cytometry, in which fluorescent probes are used to detect IgA-coated bacteria, the researchers found the E. coli bacteria were abundant in fecal samples from patients with both Crohn's disease and spondyloarthritis.
"Our findings may allow us to develop diagnostic tools to stratify Crohn's patients with spondyloarthritis symptoms as well as patients at risk," said senior author Dr. Randy Longman, an assistant professor of medicine and director of the Jill Roberts Institute Longman Lab at Weill Cornell Medicine.
Longman and his research team found that patients with Crohn's disease and spondyloarthritis had high levels of Th17 cells, which help fight inflammation. The finding may help physicians select therapies that target inflammation in both the bowels and the joints.
"We knew there was smoke but we didn't know where the fire was," said Dr. Kenneth Simpson, a professor of small animal medicine at Cornell's College of Veterinary Medicine. "If we can block the ability of bacteria to induce inflammation, we may be able to kick Crohn's disease and spondyloarthritis into remission."
The study findings are also published in Science Translational Medicine