Abstract

Context: Roux-en-Y gastric bypass (RYGB) is associated with high bone turnover. In healthy subjects, feeding causes acute reduction of bone resorption, which is regulated by several intestinal and pancreatic peptides. Objective: Our objective was to assess bone turnover after feeding in patients with RYGB. Design and Setting: This was a cross-sectional case-control study at a university hospital. Participants: Fifteen postmenopausal women who underwent RYGB 7.4 +/- 4.1 years previously were matched by age and body mass index with 15 nonoperated women (controls). Main Outcomes: Serum PTH, calcium, phosphorus, insulin, carboxy telopeptide (CTX), procollagen type I N-terminal propeptide (P1NP), and glucagon-like peptide 2 (GLP-2) were measured while fasting and after a standard meal (SM). Results: The fasting calcium, phosphorus, and PTH were similar in both groups and exhibited similar decreases after an SM. The fasting CTX level was higher in the RYGB than in the control group (0.589 +/- 0.18 vs 0.382 +/- 0.11 ng/mL; P < .05) and fell to a nadir of 42.2% of the basal value in the RYGB and 53.9% in controls (P < .05). The fasting and postprandial P1NP levels were similar in both groups and fell to a nadir of 85.8% in the RYGB and 89.3% in controls. Insulin and GLP-2 levels were similar during fasting in both groups. RYGB patients had exaggerated postprandial insulin and GLP-2 response compared with the controls with the insulin and GLP-2 area under the curve being significantly higher in the RYGB group. There was a significant negative correlation between the peak of insulin levels and the CTX changes. Conclusion: The acute reduction in bone resorption after feeding is preserved in RYGB and is even higher than in nonoperated subjects. This phenomenon is related to the increase of postprandial levels of insulin. These findings suggest a bone-protecting mechanism in RYGB that may counteract the elevated bone resorption that occurs during fasting.