Bacterial Extracellular Vesicle Composition in Human Urine and the 10-Year Risk of Abdominal Obesity.

Objective: We aimed to evaluate a causal relationship between commensal bacteria and abdominal obesity. Methods: A prospective study, including 2222 adults who provided urine samples at baseline, was performed. These samples were used for assays of genomic DNA from bacterial extracellular vesicles (EVs). During the 10-year period, the incidence rates of obesity (measured as body mass index) and abdominal obesity (measured as waist circumference) were ascertained as outcomes. To evaluate associations of bacterial composition at the phylum and genus levels with the outcomes, the hazard ratio (HR) and its confidence interval (95% CI) were estimated. Results: No significant association was observed for the risk of obesity, whereas the risk of abdominal obesity was inversely associated with the composition of Proteobacteria and positively associated with that of Firmicutes (adjusted P value <0.05). In joint analysis for the combination groups of Proteobacteria and Firmicutes composition tertiles, the group with top tertiles of both Proteobacteria and Firmicutes showed a significant HR of 2.59 (95% CI: 1.33 - 5.01) compared with the reference with lower tertiles (adjusted P value <0.05). Some genera of these phyla were associated with the risk of abdominal obesity. Conclusions: These findings suggest that bacterial composition in urinary EV samples can predict the 10-year risk of abdominal obesity.