Improvements in Glucose Metabolism Early After Gastric Bypass Surgery Are Not Explained by Increases in Total Bile Acids and Fibroblast Growth Factor 19 Concentrations

Abstract

Bile acids and fibroblast growth factor 19 (FGF19) have been suggested as key mediators of the improvements in glucose metabolism after Roux-en-Y gastric bypass (RYGB). To describe fasting and postprandial state total bile acid (TBA) and FGF19 concentrations before and after RYGB and relate them to parameters of glucose metabolism, glucagon-like peptide-1, cholecystokinin, and cholesterol fractions. A prospective descriptive study was performed at the Department of Endocrinology, Hvidovre Hospital, Hvidovre, Denmark. Thirteen type 2 diabetic (T2D) patients and 12 normal glucose tolerant (NGT) subjects participated in the study. A 4-hour liquid meal test was performed before and 1 week, 3 months, and 1 year after RYGB. We measured fasting and postprandial TBA and FGF19 concentrations. Fasting TBA concentrations decreased in NGT subjects (P < .001) and were unchanged in T2D patients 1 week after surgery, but then increased gradually in both groups with time from surgery (ANOVA Ptime < .001). Area under the curve (AUC) TBA was decreased in NGT subjects 1 week after RYGB (before surgery, 567 mmol * min/L [interquartile range, 481-826]; 1 wk, 419 [381-508]; P = .009) and was unchanged in T2D patients (894 [573-1002]; 695 [349-1147]; P = .97) but then increased with time from surgery in both groups (Ptime < .001). Fasting FGF19 concentrations were unchanged acutely after RYGB (NGT, 140 pg/mL [100-162], 134 [119-204], P = .42; T2D, 162 [130-196], 154 [104-164], P = .68) and remained unchanged throughout the follow-up period. AUC FGF19 increased gradually with time after surgery (Ptime < .001), resembling the changes seen with AUC TBA. One week after RYGB, glucose metabolism improved, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol decreased, and cholecystokinin and glucagon-like peptide-1 secretion increased, whereas FFA concentrations were unchanged. TBA and FGF19 do not explain acute changes in glucose metabolism, cholesterol fractions, and gut hormone secretion after RYGB.