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 +/- 1.56 mu mol/L to 4.42 +/- 3.92 mu mol/L (P = 0.005); conjugated BA levels increased from 0.99 +/- 1.42 mu mol/L to 3.59 +/- 3.70 mu mol/L (P = 0.01) and unconjugated BA levels increased from 0.18 +/- 0.24 mu mol/L to 0.83 +/- 0.70 mu mol/L (P = 0.009)]. With RYGB, there was a trend toward increased BA [total: 1.37 +/- 0.97 mu mol/L to 3.26 +/- 3.01 mu mol/L (P = 0.07); conjugated: 1.06 +/- 0.81 mu mol/L to 2.99 +/- 3.02 mu mol/L (P = 0.06)]. After HC diet, the level of unconjugated BA decreased [0.92 +/- 0.55 mu mol/L to 0.32 +/- 0.43 mu mol/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 ofWAT TGR5 protein is unaffected.