Objective: Periodontal disease, caused by infection with gram-negative anaerobic bacteria, is the biggest risk factor for losing teeth in most westernized countries. Recently, periodontal disease has been regarded as complication of diabetes, since it develops frequently and progress rapidly in diabetic subject. However, although association between diabetes and minimal chronic inflammation induced by periodontal disease has been reported, association between differences in microbiota and periodontal diseases in diabetic subject have not been well examined.

Research Design and Methods: Among participants of the population-based Iwaki study of Japanese held in 2016, those with information of oral cavity environment evaluated by the salivary multi-test, and microbiota of saliva samples evaluated using 16S rRNA sequencing were included in the study (n=1078). Diabetes: HbA1c levels ≧6.5% or FBG ≧126 mg/dl; normal glucose tolerance (NGT): HbA1c levels <6.0% or FBG <100 mg/dl.

Results: The number of dental caries-causing bacterium was significantly higher (3.15±1.61 vs. 2.61±1.61, p <0.01), and the saliva buffer capacity was significantly lower (71.9±10.8 vs. 77.8±10.4, p <0.01) in diabetic subjects compared to those with NGT. Further, proportion of the phylum Firmicutes was higher (41.3±12.4% vs. 37.2±11.6%, p <0.01), and the phylum Bacteroidetes was significantly lower (18.9±8.5% vs. 20.9±8.3%, p=0.01) in diabetic subjects compared to those with NGT.

Conclusions: Abnormal glucose tolerance may change oral microbiota, induce dental caries, and be a risk factor for periodontal disease. We will further examine association between microbiota and diabetes in taxonomic category below phylum, and, also, in consideration with nutrients consumed.


S. Mizushiri: None. M. Daimon: None. H. Murakami: None. M. Murabayashi: None. Y. Matsuhashi: None. A. Kamba: None.

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