Gut microbiota adaptation after weight loss by Roux-en-Y gastric bypass or sleeve gastrectomy bariatric surgeries

Abstract Background Gut microbiota could be involved in the metabolic improvement after surgery. Objective The aim of the current study was to evaluate the short-term evolution of the gut microbiomeafter different bariatricsurgery procedures and their functionality, and relate it with obesity resolution. Setting University Hospital, Spain Methods We studied 28 patients with severe obesity: 14 underwent a Roux-en-Y gastric bypass (RYGB) and 14 underwent laparoscopic sleeve gastrectomy( SG). All patients were examined before and 3 months after the correspondent bariatricsurgery. Gut microbiomeprofile was assessed by the sequencing of amplicons from the 16sDNA gene by next generation sequencing (NGS). Results Gut microbiota profiles significantly differed between surgical procedures. RYGB suffered the largest changes in the microbiota population. SGand RYGB differed in their profiles with higher levels of Akkermansia, Eubacterium, Haemophilus and Blautia for SG, while Veillonella, Slackia, Granucatiella and Acidaminococcusresulted with greater levels in RYGB. RYGB microbiota changes were reflected also at functionality level, especially in pathways related to environmental adaptation. A biomarker discoveryanalysis revealed the genus Blautia as characteristic in SG, while Veillonellawas of RYGB. Conclusion Our study shows a shift of the gut microbiomeafter a bariatricsurgery in a procedure- related manner. Gut microbiomechanges are related to the adaptation to the changing gut environment and could be related to the pH fluctuations.