A recent University of Pennsylvania study found that the oral microbiome is affected by diabetes, causing a shift to increase its pathogenicity. 

Dana Graves, senior author on the new study and vice dean of scholarship and research at Penn’s School of Dental Medicine, conducted the study in response to a report from the European Federation of Periodontology and the American Academy of Periodontology stating there is no compelling evidence that diabetes is directly linked to changes in the oral microbiome.

Using a mouse model that mimics Type 2 diabetes, Dr. Graves and colleagues found that the oral microbiome of mice with diabetes shifted, and that the change was associated with increased inflammation and bone loss. 

In comparing the oral microbiome of diabetic mice to that of healthy mice, the researchers found the microbiomes were similar prior to the diabetic mice’s development of high blood sugar levels, or hyperglycemia. Once the diabetic mice were hyperglycemic, however, their microbiome became distinct from that of the healthy mice and had a less diverse community of bacteria. In addition, the diabetic mice had periodontitis—including a loss of bone supporting the teeth—and increased levels of IL-17, a signaling molecule important in immune response and inflammation. Increased levels of IL-17 in humans are associated with periodontal disease.

The researchers investigated further by transferring microorganisms from the diabetic mice to normal germ-free mice and found that these recipient mice developed bone loss and showed more markers of inflammation than normal mice. These results confirmed that the microbiome was causing the periodontitis.

The researchers suspected that inflammatory cytokines, and specifically IL-17, were contributing to this reaction, so they repeated the microbiome transfer experiments after injecting the diabetic donors with an anti-IL-17 antibody. They found the mice that received microbiomes from the treated diabetic mice had much less severe bone loss compared to mice that received a microbiome transfer from untreated mice, which “demonstrate unequivocally” that the inflammatory changes that enhance bone loss in periodontitis are driven by diabetes-induced changes in the oral microbiome.

According to Dr. Graves, the study highlights the importance for people with diabetes of controlling blood sugar and practicing good oral hygiene.