SummaryOver 73,700 adults age 40-79, nearly 70% African American, were recruited at community health centers across 12 southeastern states; individual characteristics were recorded and biologic specimens collected at baseline for later follow-up. The Southern Community Cohort Study is a unique national resource for assessing determinants of racial/ethnic differentials in diseases.

Background and Objective The oral microbiome may help to maintain systemic health, including how it affects blood glucose levels; however, direct evidence linking the oral microbiome with diabetes is lacking. Material and Methods We compared the oral microbiome profiles of 98 participants with incident diabetes, 99 obese non-diabetics, and 97 normal weight non-diabetics, via deep sequencing of the 16S rRNA gene. Results We found that the phylum Actinobacteria was present significantly less abundant among diabetes patients than among the controls (P=3.9 × 10−3); the odds ratio (OR) and 95% confidence interval (CI) was 0.27(0.11–0.66) for those individuals who had relative abundance higher than the median value. Within this phylum, five families and seven genera were observed, and most of them were less abundant among diabetes patients. Notably, genera Actinomyces and Atopobium were associated with 66% and 72% decreased risk of diabetes with P values of 8.9 × 10−3 and 7.4 × 10−3, respectively. Stratified analyses by race showed that most taxa in this phylum were associated with diabetes in both black and white participants. This phylum was also less abundant among non-diabetic obese subjects compared to normal weight individuals, especially genera Mobiluncus, Corynebacterium and Bifidobacterium, which showed P <0.05. Conclusion Our study revealed that multiple bacteria taxa in the phylum Actinobacteria are associated with risk of type 2 diabetes. Some are also associated with the prevalence of obesity, suggesting that the oral microbiome may play an important role in diabetes etiology.

Our findings suggest that major differences in diabetes prevalence between African Americans and Whites may simply reflect differences in established risk factors for the disease, such as SES, that typically vary according to race.

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