The association of oral microbiota and oral-gut microbial co-presence with obesity in Chinese children.

AIM: The oral cavity harbors a complex microbial community that is increasingly recognized for its association with systemic diseases, such as cardiovascular diseases. Furthermore, a significant proportion of oral microbiota is swallowed, potentially influencing the gut microbiota. This potential oral-gut microbial linkage is hypothesized as a pathway through which oral microbes exert systemic effects. This study aims to investigate the association between oral microbiota and childhood obesity, and to explore the co-presence patterns between oral and gut microbiota in relation to childhood obesity. MATERIALS AND METHODS: This study is a case-control study. We recruited participants aged 6-17 years from Beijing Children's Hospital, collecting saliva and fecal samples. Both parts of the study performed 16S rRNA gene sequencing on the samples, comparing microbial diversity between obese (OB) and normal-weight (NW) children. We aggregated relative abundances of major bacterial phyla and genera to identify differentially abundant genera between groups. Linear discriminant analysis effect size (LEfSe) was used to identify genera significantly different between NW and OB children. Additionally, we examined correlations between key oral genera and clinical indicators. Genera detected in both oral cavity and gut samples at > 10% prevalence were defined as "co-present genera". A random forest model was constructed to distinguish NW from OB children. RESULTS: A total of 136 children were enrolled, comprising 68 individuals in the OB group and 68 in the NW group. There were no significant differences observed in age, gender, birth weight, or height. Oral microbiota diversity and composition significantly differed between OB and NW groups. LEfSe analysis identified Neisseria, Peptostreptococcus, and Oribacterium as potential discriminative genera in the OB oral microbiota. The co-present genera exhibited distinct relative abundance patterns across sites. A Random Forest model based on 23 oral and 7 gut co-present genera achieved an area under the curve of 0.73. Notably, both Veillonella and Bifidobacterium were identified as key bacterial genera in both the oral cavity and the gut. CONCLUSIONS: This study indicated that the oral microbiome is closely associated with childhood obesity. Consequently, the oral microbiome represents a highly attractive target for future obesity prevention strategies.