Obesity alters composition and diversity of the oral microbiota in patients with type 2 diabetes mellitus independently of glycemic control

BACKGROUND AND OBJECTIVE: The involvement of the oral microbiota as a possible link between periodontitis, type 2 diabetes mellitus and obesity is still not well understood. The objective of the study was to investigate if glycemic control and obesity play a role in modulating the composition and diversity of the oral microbial ecology. MATERIAL AND METHODS: A cohort of patients with type 2 diabetes mellitus (n = 18) was recruited. Participants demonstrating improved glycemic control after 3 months (n = 6) were included in a second examination. A full mouth examination was performed to estimate periodontitis severity followed by sample collection (subgingival plaque and saliva). Generation of large sequence libraries was performed using the high-throughput Illumina MiSeq sequencing platform. RESULTS: The majority of participants (94.4%, n = 17) presented with moderate or severe forms of periodontitis. Differences in microbial composition and diversity between obese (BMI ≥ 30 kg/m(2)) and non-obese (BMI < 30 kg/m(2)) groups were statistically significant. Cross-sectional and longitudinal approaches failed to reveal statistically significant associations between HbA(1c) level and species composition or diversity. CONCLUSIONS: Obesity was significantly associated with the oral microbial composition. The impact of glycemic control on oral microbiota, however, could not be assured statistically.