Oral microbiome changes in subjects with obesity following bariatric surgery compared to lean counterparts

Keun-Suh Kim ¹ Hee Sam Na ² Tae Jung Oh ^3,4 Hyejung Han ² Jiyeon Kim ¹ Jin-Sil Hong ¹ Hyo-Jung Lee ^1* Young Suk Park ^5* Jin Chung ^2*

• ¹ Department of Periodontology, Section of Dentistry, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
• ² Department of Oral Microbiology, School of Dentistry, Pusan National University, Busan, Republic of Korea
• ³ Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Republic of Korea
• ⁴ Department of Internal Medicine, College of Medicine, Seoul National University, Seoul, Republic of Korea
• ⁵ Department of Surgery, Seoul National University Bundang Hospital, Seongnam, Republic of Korea

This study aimed to compare oral microbiome profiles between obese and lean individuals without clinical periodontitis, and to assess changes in the oral microbiome of obese subjects following bariatric surgery. Individuals with a body mass index (BMI) > 30 were enrolled in the obese group, whereas those with a BMI < 23 served as controls. The obese surgery group, which consented to bariatric surgery, was followed up at 1, 3, and 6 months with clinical examinations. Oral examinations were conducted and periodontal disease was classified based on the probing results. Saliva, buccal and subgingival microbiome samples were analyzed for community diversity, relative bacterial abundance, and differential abundance analysis between control(n=24) and obese group(n=31). To evaluate the effect size and statistical power, we used micropower, a simulationbased method for Permutational Multivariate Analysis of Variance-based β-diversity comparisons. The obese group exhibited distinct alpha diversity (buccal : Chao1 p = 0.0002, Shannon p= 0.0003, supragingival : Shannon p < 0.0001) compared with the control group.The obese group exhibited distinct alpha diversity (buccal : Chao1 p = 0.0002, Shannon p= 0.0003, supragingival : Shannon p < 0.0001) and principal coordinate analysis compared with the control group. Bray-Curtis distance analysis indicated a significant disparity in microbiome composition distribution in saliva samples ( p = 0.003) and buccal ( p = 0.002) and subgingival plaque samples (p = 0.001). Although the obese and normal weight groups exhibited no significant periodontal differences, the obese group showed distinct species associated with periodontal disease, especially in subgingival plaque including Filifactor alocis, Peptostreptococcaceae spp., Prevotella spp., and Treponema maltophilum. Cluster analysis of the obese surgery group indicated the emergence of microbiomes associated with a healthy state that increased over time including Streptococcus salivarious and various Veillonella spp., whereas clusters containing periodontal pathogens including Porphyromonas spp., tended to diminish. Thus, the oral microbiome at 6 months post-bariatric surgery indicates a potential shift towards a healthy periodontal state.