Microbiota alterations after gastric bypass versus sleeve gastrectomy in patients with type 2 diabetes (Oseberg)

Bariatric surgery is the most efficient treatment for type 2 diabetes (T2D) and has been associated with changes in the gut microbiome. The altered gut microbiome observed after bariatric surgery is suggested to contribute to improved glucose metabolism in the host. Sleeve gastrectomy (SG) is the most common type of bariatric surgery, while gastric bypass (RYGB) has a higher frequency of T2D remission. Here we analyzed the fecal microbiome in patients with T2D randomized to either SG or RYGB in a triple-blind, randomized controlled trial. Both surgeries shifted the microbiome majorly in a similar direction, but RYGB produced larger shifts 1 year after surgery. The extent of microbiome change was associated with higher circulating GLP-1 levels and beta-cell function following surgery, independent of weight loss. The functional potential of the microbiota was also altered, along with shift in fermentation products, in both surgery types. We observed decreased potential for carbohydrate degradation in the post-bariatric surgery microbiome, with accompanying increase in potential for butyrate production, especially from amino acids such as lysine. Both surgeries were associated with increased gene richness and methanogenic Archaea, while RYGB was associated with increased relative abundance of Escherichia spp. following surgery. Both increased shift in fermentation products and higher increase in gene richness, and larger increase in potential for butyrate production from amino acids was linked to T2D remission. Increased abundance of Archaea and gene richness that previously been associated with metabolic health. These shifts indicates that the gut maintains an anaerobic environment following surgery and suggest that microbial adaptations to the altered milieu following surgery may contribute to metabolic improvements in the host.