Diabetes Linked to Changes in Oral Microbiome, Periodontitis

Periodontitis is a gum infection that can result in tooth loss and other dental problems. Patients with diabetes are more likely to develop the infection due to a change in the oral microbiome, according to a new study published by Cell Host & Microbe.

The authors found that diabetes elicits changes in the oral microbiome to increase inflammation, which was also observed to increase the risk of bone loss.

"Up until now, there had been no concrete evidence that diabetes affects the oral microbiome," said senior study author Dana Graves, DDS, DMSc. "But the studies that had been done were not rigorous."

Previously, the European Federation of Periodontology and the American Academy of Periodontology reported that there was no substantial link between diabetes and changes in the oral microbiome.

However, the authors decided to explore potential oral microbiome changes in mouse models of type 2 diabetes.

"My argument was that the appropriate studies just hadn't been done, so I decided we'll do the appropriate study," Dr Graves said.

The investigators characterized the oral microbiome of mice with diabetes and healthy controls. They discovered that the 2 groups of mice had similar oral microbiomes when sampled prior to hyperglycemia, according to the authors.

Once the mice experienced hyperglycemia, the authors found that the microbiome changed and had a less diverse community of bacteria, according to the study. The mice with diabetes also developed periodontitis, including loss of bone supporting the teeth and increased levels of IL-17, which is involved with inflammation and human periodontitis.

"The diabetic mice behaved similar to humans that had periodontal bone loss and increased IL-17 caused by a genetic disease," Dr Graves said.

These results provide evidence of a link between oral microbiome and periodontitis; however, the findings could not be used to prove that microbiome changes led to the condition.

In an additional analysis, the investigators transferred the oral microbiome from the mice with diabetes to mice who were not exposed to any microbes.

The authors found that the germ-free mice developed bone loss after the transfer. Micro-CT scans revealed that the mice had a 42% reduction in bone loss compared with normal mice. The recipient mice also had an increase in markers of inflammation, according to the study.

"We were able to induce the rapid bone loss characteristic of the diabetic group into a normal group of animals simply by transferring the oral microbiome," Dr Graves said.

Since the results showed that microbiome changes resulted in periodontitis, the authors explored how this occurred.

The investigators then repeated the microbiome transfer, but injected the donor mice with an anti-IL-17 antibody prior to the transfer. They found that this time, the recipient mice had less severe bone loss compared with mice receiving the microbiome from untreated mice, according to the study.

These findings suggest that diabetes causes changes in the oral microbiome that result in inflammation and periodontitis, according to the authors.

While these findings were significant in mice, this approach is likely to be unsuccessful in humans due to the role IL-17 plays in immune protection, according to the study.

The authors also said that these results underscore the importance of controlling blood glucose levels and good oral hygiene for patients with diabetes.

"Diabetes is one of the systemic disease that is most closely linked to periodontal disease, but the risk is substantially ameliorated by good glycemic control," Dr Graves concluded. "And good oral hygiene can take the risk even further down."