Gut Microbial Predictors of Type 2 Diabetes Remission Following Bariatric Surgery

Purpose Distinct anatomical rearrangements of the gastrointestinal tract achieved by various types of bariatric surgery cause changes in nutrient intake and gut microbiota. The contribution of such gut microbiota changes to remission of type 2 diabetes (T2D) remains unclear. Aim We examined gut microbiota changes following banded Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) in a randomised study, in relation to T2D remission. Materials and Methods Whole-metagenome shotgun sequencing was carried out on paired stool samples at pre- and 1-year post-surgery collected from 44 participants with T2D randomised to banded Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). Taxonomic composition and predicted functional potential of the gut bacteria were identified using HUMANn2, and annotated using MetaCyc. Five-day dietary records (analysed using FoodWorks v8.0), body weight and diabetes status were recorded at both time points. Results RYGB participants had higher percentage excess weight loss than SG (p = 0.01), even though dietary intake was similar at 1-year post-surgery. Similar proportions achieved diabetes remission (HbA1c < 48 mmol/mol without medications) after either RYGB (68%) or SG (59%). RYGB resulted in increased abundances of Firmicutes and Proteobacteria, while SG resulted in increased Bacteroidetes. Pre-surgery, an increased abundance of Eubacteriaceae (p = 0.01) and Alistipes putredinis (p = 0.01) was observed in those who went on to remit from T2D post-surgery. Following surgery, Lachnospiraceae (p = 0.04) and Roseburia (p = 0.01) species were more abundant in those who had achieved T2D remission. Conclusions Specific stool bacterial taxa may signal likelihood of T2D remission after bariatric surgery which is potentially mediated by increases in Lachnospiraceae and Roseburia.