Obesity influences composition of salivary and fecal microbiota and impacts the interactions between bacterial taxa

Abstract

Obesity is an increasing global health concern and is associated with a broad range of morbidities. The gut microbiota are increasingly recognized as important contributors to obesity and cardiometabolic health. This study aimed to characterize oral and gut microbial communities, and evaluate host:microbiota interactions between clinical obesity classifications. We performed 16S rDNA sequencing on fecal and salivary samples, global metabolomics profiling on plasma and stool samples, and dietary profiling in 135 healthy individuals. We grouped individuals by obesity status, based on body mass index (BMI), including lean (BMI 18-24.9), overweight (BMI 25-29.9), or obese (BMI [≥]30). We analyzed differences in microbiome composition, community inter-relationships, and predicted microbial function by obesity status. We found that salivary bacterial communities of lean and obese individuals were compositionally and phylogenetically distinct. An increase in obesity status was positively associated with strong correlations between bacterial taxa, particularly with bacterial groups implicated in metabolic disorders including Fretibacterium, and Tannerella. Consumption of sweeteners, especially xylitol, significantly influenced compositional and phylogenetic diversities of salivary and fecal bacterial communities. In addition, obesity groups exhibited differences in predicted bacterial metabolic activity, which was correlated with hosts metabolite concentrations. Overall, obesity was associated with distinct changes in bacterial community dynamics, particularly in saliva. Consideration of microbiome community structure, and inclusion of salivary samples may improve our ability to understand pathways linking microbiota to obesity and cardiometabolic disease. IMPORTANCEObesity is a worldwide epidemic that is associated with a wide range of health issues. Microbiota were shown to influence metabolism and obesity development. Our study aimed to evaluate the interactions between obesity, salivary and fecal microbiota, and metabolite concentrations in healthy individuals. The oral bacterial community was more impacted by the obesity status of the host than fecal microbiota. Consistently for oral and fecal microbiota, the number of strong interactions between bacteria increased with the increase in the obesity status. Several predicted microbial metabolic pathways that were shown to be associated with metabolic health were uniquely enriched between obesity groups. In addition, these metabolic pathways were correlated with plasma and stool metabolites. Our results suggest that oral microbiota might better reflect the obesity status of the host than fecal microbiota, and that correlations between microbial taxa are altered during obesity.