Background

Higher preoperative severity of metabolic comorbidities can lead to sub-optimal metabolic recovery and decrease the incidence of disease remission following Roux-en-Y gastric bypass (RYGB). Gut microbiota are recognized as mediators of obesity and metabolic dysfunction and are altered by RYGB. We hypothesize that differences in microbiota reflect metabolic health severity and may impact response to RYGB.

Methods

Using a novel scoring system, we objectively scored diabetes mellitus, hypertension, and dyslipidemia in women undergoing RYGB to identify two groups as 'metabolically healthy obesity' (MHO) (n=15) or 'metabolically unhealthy obesity' (MUHO) (n=15). We then compared the pre- and 2-month post-RYGB comorbidity severity and fecal microbiota patterns between these groups.

Results

Mean age was 42 +- 9.1 years. There was no difference in preoperative BMI between groups (MHO 46.9 vs. MUHO 44.5 kg/m2, p= 0.39). RYGB significantly reduced BMI in both groups (MHO -5.8; MUHO -6.2 kg/m2), but postoperative BMI was not different between groups (p=0.67). HbA1c improved postoperatively (MHO-preop 5.8 vs MHO-2M 5.4 (p<0.001); MUHO-preop 7.8 vs MUHO-2M 6.6 (p<0.001)). Microbiota composition was not different between MHO and MUHO preoperatively. However, RYGB altered 55 species in MHO (ANCOM, p<0.05), but no significant compositional changes were detected in MUHO post-RYGB.

Conclusions

The lack of response of the gut microbiome to RYGB in the MUHO group suggests a RYGB-resistant microbiota community in these patients. Further study to understand the associations of microbial communities with metabolism could unmask unique mechanisms that drive disease phenotypes and the metabolic responses to RYGB.