A new collaborative study by US researchers reveals that inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis may be the latest condition made worse by poor oral health.
Nobuhiko Kamada, assistant professor of internal medicine in the division of gastroenterology at the University of Michigan, noticed an emerging link in research literature between an overgrowth of foreign bacterial species in the guts of people with IBD—bacteria that are normally found in the mouth.
“I decided to approach the dental school to ask the question, does oral disease affect the severity of gastrointestinal diseases?” Professor Kamada said.
The new mouse study, published in Cell, shows two pathways by which oral bacteria appear to worsen gut inflammation.
In the first pathway, periodontitis leads to an imbalance in the normal healthy microbiome found in the mouth, with an increase of bacteria that cause inflammation. These disease-causing bacteria then travel to the gut.
However, this alone may not be enough to set off gut inflammation. The team demonstrated that oral bacteria may aggravate gut inflammation by looking at microbiome changes in mice with inflamed colons.
“The normal gut microbiome resists colonisation by exogenous, or foreign, bacteria,” Professor Kamada said.
“However, in mice with IBD, the healthy gut bacteria are disrupted, weakening their ability to resist disease-causing bacteria from the mouth.”
The team found that mice with both oral and gut inflammation had significantly increased weight loss and more disease activity.
In the second proposed pathway, periodontitis activates the immune system’s T cells in the mouth. These mouth T cells travel to the gut where they, too, exacerbate inflammation. The gut’s normal microbiome is held in balance by the action of inflammatory and regulatory T cells that are fine-tuned to tolerate the resident bacteria. But, said Professor Kamada, oral inflammation generates mostly inflammatory T cells that migrate to the gut, where they, removed from their normal environment, end up triggering the gut’s immune response, worsening disease.
“This exacerbation of gut inflammation driven by oral organisms that migrate to the gut has important ramifications in emphasising to patients the critical need to promote oral health as a part of total body health and wellbeing,” co-author William Giannobile said.