Distinct oral and fecal microbiota composition in preschool children with overweight/obesity: a cross-sectional study

Limited research has explored the relationship between microbiota characteristics in both the oral cavity and the intestine, and the prevalence of obesity or overweight status in preschool-aged children. In this study, we collected saliva, oral mucosal plaque, supragingival dental plaque, and fecal samples from 47 preschool children aged 3 to 6 with obesity/overweight, along with 34 age-matched normal-weight controls. These samples were subjected to 16S rRNA gene sequencing for microbial analysis. We found that the overweight/obesity group exhibited a lower richness and diversity of fecal microbiota compared to the control group. Distinct niche-specific clustering was observed across different oral niches. In the overweight/obesity group, five genera showed significantly higher abundance, while six genera showed significantly lower levels in saliva samples. In mucosal samples, five genera exhibited increased abundance, whereas two genera had reduced levels in dental plaque samples. In fecal samples, two genera displayed significantly higher abundance, while eight genera showed lower levels. These distinct microbial taxa were also correlated with clinical parameters, including body mass index (BMI) and skin-fold thickness (SFT). Furthermore, correlation analysis showed that the oral bacteria were significantly negatively correlated with fecal bacteria, which was markedly attenuated in children with overweight/obesity. Overall, our study identifies distinct microbial signatures in the oral cavity and intestine of preschool children with overweight/obesity, compared to those with normal weight. These findings offer new insights into the potential role of microbial dysbiosis in the development of childhood obesity, providing a foundation for future strategies aimed at preventing and intervening in childhood obesity and overweight. KEY POINTS: • Distinct niche-specific clustering was observed between different oral niches. • Shifts of abundance observed in obese children were correlated with BMI and SFT. • Negative correlations between oral and fecal genera were weaker in overweight/obese children.