Peri-operative antibiotics acutely and significantly impact intestinal microbiota following bariatric surgery.

Bariatric surgery is the most effective treatment for weight loss. Vertical sleeve gastrectomy (VSG) involves the resection of ~ 80% of the stomach and was conceived to purely restrict oral intake. However, evidence suggests more complex mechanisms, particularly postoperative changes in gut microbiota, in facilitating weight loss and resolving associated comorbidities. VSG in humans is a complex procedure and includes peri-operative antibiotics and caloric restriction in addition to the altered anatomy. The impact of each of these factors on the intestinal microbiota have not been evaluated. The aim of this study was to determine the relative contributions of each of these factors on intestinal microbiota composition following VSG prior to substantial weight loss. Thirty-two obese patients underwent one of three treatments: (1) VSG plus routine intravenous peri-operative antibiotics (n = 12), (2) VSG with intravenous vancomycin chosen for its low intestinal penetrance (n = 12), and (3) caloric restriction (n = 8). Fecal samples were evaluated for bacterial composition prior to and 7 days following each intervention. Only patients undergoing VSG with routine peri-operative antibiotics showed a significant shift in community composition. Our data support the single dose of routine peri-operative antibiotics as the most influential factor of intestinal microbial composition acutely following VSG.

Bile Acids Increase Independently From Hypocaloric Restriction After Bariatric Surgery.

OBJECTIVES: To measure changes in the composition of serum bile acids (BA) and the expression of Takeda G-protein-coupled receptor 5 (TGR5) acutely after bariatric surgery or caloric restriction. SUMMARY BACKGROUND DATA: Metabolic improvement after bariatric surgery occurs before substantial weight loss. BA are important metabolic regulators acting through the farnesoid X receptor and TGR5 receptor. The acute effects of surgery on BA and the TGR5 receptor in subcutaneous white adipose tissue (WAT) are unknown. METHODS: A total of 27 obese patients with type 2 diabetes mellitus were randomized to Roux-en-Y gastric bypass (RYGB) or to hypocaloric diet (HC diet) restriction (NCT 1882036). A cohort of obese patients with and without type 2 diabetes mellitus undergoing vertical sleeve gastrectomy was also recruited (n = 12) as a comparison. RESULTS: After vertical sleeve gastrectomy, the level of BA increased [total: 1.17 ±â€Š1.56 µmol/L to 4.42 ±â€Š3.92 µmol/L (P = 0.005); conjugated BA levels increased from 0.99 ±â€Š1.42 µmol/L to 3.59 ±â€Š3.70 µmol/L (P = 0.01) and unconjugated BA levels increased from 0.18 ±â€Š0.24 µmol/L to 0.83 ±â€Š0.70 µmol/L (P = 0.009)]. With RYGB, there was a trend toward increased BA [total: 1.37 ±â€Š0.97 µmol/L to 3.26 ±â€Š3.01 µmol/L (P = 0.07); conjugated: 1.06 ±â€Š0.81 µmol/L to 2.99 ±â€Š3.02 µmol/L (P = 0.06)]. After HC diet, the level of unconjugated BA decreased [0.92 ±â€Š0.55 µmol/L to 0.32 ± 0.43 µmol/L (P = 0.05)]. The level of WAT TGR5 gene expression decreased after surgery, but not in HC diet. Protein levels did not change. CONCLUSIONS: The levels of serum BA increase after bariatric surgery independently from caloric restriction, whereas the level of WAT TGR5 protein is unaffected.