Abstract
BACKGROUND: Obesity has emerged as a global health crisis. Increasing evidence suggests that imbalances in gut and oral microbiota are linked to obesity, with specific microbial profiles influencing metabolic dysfunction and weight gain. Given the distinct ecological niches and the importance of gut and oral microbiota in obesity, this study analyzed both oral and fecal microbiota in adults with obesity, aiming to identify potential niche-specific microbial signatures associated with the condition. RESULTS: The comparison of fecal and oral microbiota communities between individuals with obesity and non-obese controls revealed significant differences in microbial composition and diversity. The predominant genera identified in both sample types were Prevotella, Faecalibacterium, Streptococcus, and Porphyromonas. A notable restructuring of microbial communities was observed between fecal and oral samples, regardless of obesity status. Furthermore, obesity-associated changes in microbial co-occurrence networks were found to be niche-specific, with reduced modularity in stool samples. In contrast, saliva microbial networks appeared to be more compartmentalized than those in stool. MaAsLin 3 and ANCOM-BC2 analyses identified five niche-specific taxa associated with obesity. These included positive associations in saliva with Granulicatella sp902479935, Lancefieldella sp938036925, Peptostreptococcus stomatis, Rothia sp916715725, as well as a negative association in saliva with Faecalibacterium sp934503275. Mediation analysis indicated that the second principal component partially mediated these effects, with Lancefieldella sp938036925 and others serving as positive contributors. The taxa Wolinella, Phocaeicola, and Bulleidia, which exhibited high abundance in saliva, were consistently selected by all machine learning models. CONCLUSIONS: This study contributes to the growing body of literature investigating the relationship between obesity and microbial communities. Using 16 S rRNA gene amplicon sequencing, we characterized distinct microbial compositions in both saliva and fecal samples from individuals with obesity compared to normal-weight controls within a defined geographic population. The results suggest that the salivary microbiome may contain potential associative biomarkers indicative of obesity risk, warranting further in-depth investigation.