New study demonstrates how oral bacteria can amplify gut inflammation

Building on the growing link between poor oral health and gastrointestinal disease, new research from the University of Michigan has homed in on the possible mechanisms by which periodontitis can exacerbate the gut inflammation seen in patients with inflammatory bowel disease (IBD).

It is becoming increasingly clear the trillions of bacteria living inside our bodies have profound effects on our general health. While a great deal of research has focused directly on the gut microbiome, evidence is emerging demonstrating compelling ways our oral bacteria can influence the rest of our body.

Recent studies have revealed fascinating links between poor oral health and hypertension. One team of researchers has even demonstrated how oral bacteria seems to directly modulate beneficial blood pressure reductions seen immediately following exercise.

For several years researchers have been tracking an intriguing association between periodontitis and IBD. A recently published meta-analysis confirmed the significance of this relationship, however, the causality of this association is still yet to be established.

This new research set out to explore the mechanisms by which bacteria in the mouth could possibly influence the severity of gastrointestinal disease. In a collaborative effort bringing together gastroenterology and dental research teams, a detailed animal study presents a convincing mechanistic hypothesis to explain the oft-cited association.

The first pathway of action proposed in the study demonstrates how periodontitis results in an increase of certain bacterial species in the oral cavity. These bacteria were then seen to spread from the mouth into the gut, where they can directly trigger inflammation. Importantly, the research suggests this pathway doesn’t cause IBD in isolation, as generally a healthy gut microbiome can fight back against an influx of bad bacteria.

“The normal gut microbiome resists colonization by exogenous, or foreign, bacteria,” says Nobuhiko Kamada, one of the authors on the new study. “However, in mice with IBD, the healthy gut bacteria are disrupted, weakening their ability to resist disease-causing bacteria from the mouth.”

A second observation in the study revealed gum disease bacteria activating production of immune T cells in the mouth. These immune cells were then seen to migrate to the gut and enhance gastrointestinal inflammation.

“This exacerbation of gut inflammation driven by oral organisms that migrate to the gut has important ramifications in emphasizing to patients the critical need to promote oral health as a part of total body health and wellbeing,” explains the study’s co-author William Giannobile.

The study is cautious to add there is no evidence either of these two pathways of action occur in healthy individuals. This means there is no suggestion oral disease is the sole cause of gastrointestinal inflammation. Instead, there needs to be pre-existing gut microbiome dysregulation for this kind of IBD exacerbation to occur. Another co-author on the study, Shrinivas Bishu, says this research points to possible reasons why some IBD patients are more resistant to treatment than others, and suggests monitoring oral health in patients could be an additional tool for managing gut inflammation.

“This study importantly implies that clinical outcomes in IBD may be improved by monitoring oral inflammation – an intriguing concept,” says Bishu.

The new study was published in the journal Cell.

Source: University of Michigan

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