Background

The impact of one-anastomosis gastric bypass (OAGB) surgery on human gut microbial communities beyond 6 months of having the procedure is unknown. The present pilot study characterized microbiota and cardiometabolic markers differences up to 12-months post-OAGB.

Methods

Seven female participants (mean-age 42 years, BMI 55 kg/m2) underwent a very-low calorie diet for 3 weeks prior to OAGB. At pre-surgery and at 3-, 6- and 12-months post-OAGB, fecal microbial communities were analysed by sequencing the V4 region of the 16S rRNA gene using MiSeq (illumina). Time-course changes in anthropometric measurements, blood pressure (BP), glycaemic status and lipid profile were also assessed.

Results

At 12-months post-OAGB, patients achieved significant reductions in BMI (-32.7%, P<0.05) and systolic BP (-17%, P<0.05), with trends for improved glycaemic control (HbA1c -21.5%). Four dominant gut phyla were detected: Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. Phylogenetic alpha-diversity analysis indicated that microbial richness and diversity were highest pre-surgery, lowest 6-months post-OAGB and returned towards baseline levels by 12-months post-OAGB. No significant differences were found for Shannon, Simpson and Choa1 diversity measures. For beta-diversity analysis, weighted UniFrac distance data detected significant time-course differences (p=0.019). Visually, community shifts were observed pre- vs. 3- and 6-months post-OAGB, but these changes were reversed by 12-months post-OAGB.

Conclusions

Accompanying significant falls in BMI and systolic BP, and trends for long-term glycaemic control, this study is the first to describe transient changes in the gut microbiota community of patients with Class III obesity 12-months post-OAGB, and to identify altered composition of dominant bacteria.