Distinct fasting and postprandial bile acid responses following Roux-en-Y and one-anastomosis gastric bypass

Bariatric surgery is the most effective long-term treatment for obesity, but how different surgical techniques affect metabolic outcomes remains unclear. Bile acids (BAs), increasingly recognized as metabolic regulators, rise postprandially after surgery and may mediate some of these effects. This exploratory study investigates the differential impact of Roux-en-Y gastric bypass (RYGB) and one-anastomosis gastric bypass (OAGB) on BA profiles and associated metabolic outcomes over one year.

Forty-five patients with obesity (15 men, 30 women; mean (SD) age 46.6 (7.1) years) were randomized to receive either RYGB (n = 24) or OAGB (n = 20). Clinical assessments, body composition measurements (Dual energy X-ray absorptiometer), fasting blood tests including lipids and inflammation markers, 360-minute mixed meal test, and oral glucose tolerance test were conducted 4-6 weeks before and at 6 and 12 months after operation. Plasma total and 15 individual BAs (LC-MS) were measured at eight time points during the mixed meal test.

RYGB led to an increase in postprandial secondary BAs from baseline to 12 months (p = 0.004), particularly deoxycholic acid (DCA; p < 0.001) and glycodeoxycholic acid (GDCA; p = 0.006) compared with OAGB. In contrast, OAGB led to an increase in postprandial primary taurine-conjugated BAs (p = 0.039), especially taurochenodeoxycholic acid (TCDCA; p = 0.036) compared with RYGB. Similarly, RYGB increased unconjugated secondary BAs, especially DCA, whereas OAGB increased conjugated primary BAs, like TCA and GCA during fasting. Metabolic improvements were similar in both groups. Post-RYGB increases in secondary BAs correlated with improved insulin sensitivity and post-OAGB increases in primary taurine-conjugated BAs correlated with higher fat mass preservation during weight loss.

RYGB and OAGB differentially modulate BA profiles over one year, with RYGB increasing secondary BAs and OAGB increasing taurine-conjugated primary BAs. These findings suggest distinct mechanisms contributing to their metabolic benefits.