Effects of roux‐en‐Y gastric bypass surgery on postprandial fructose metabolism

Objective Fructose is partly metabolized in small bowel enterocytes, where it can be converted into glucose or fatty acids. It was therefore hypothesized that Roux‐en‐Y gastric bypass (RYGB) may significantly alter fructose metabolism. Methods We performed a randomized clinical study in eight patients 12‐17 months after RYGB and eight control (Ctrl) subjects. Each participant was studied after ingestion of a protein and lipid meal (PL) and after ingestion of a protein+lipid+fructose+glucose meal labeled with 13C‐fructose (PLFG). Postprandial blood glucose, fructose, lactate, apolipoprotein B48 (apoB48), and triglyceride (TG) concentrations, 13C‐palmitate concentrations in chylomicron‐TG and VLDL‐TG, fructose oxidation (13CO2 production), and gluconeogenesis from fructose (GNGf) were measured over 6 hours. Results After ingestion of PLFG, postprandial plasma fructose, glucose, insulin, and lactate concentrations increased earlier and reached higher peak values in RYGB than in Ctrl. GNGf was 33% lower in RYGB than Ctrl (P = 0.041), while fructose oxidation was unchanged. Postprandial incremental areas under the curves for total TG and chylomicrons‐TG were 72% and 91% lower in RYGB than Ctrl (P = 0.064 and P = 0.024, respectively). ApoB48 and 13C‐palmitate concentrations were not significantly different. Conclusions Postprandial fructose metabolism was not grossly altered, but postprandial lipid concentrations were markedly decreased in subjects having had RYGB surgery.