CONTEXT: Whether Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) differentially affect postprandial gastrointestinal hormones and β-cell function in type 2 diabetes remains unclear.

OBJECTIVE: To compare gastrointestinal hormones and β-cell function assessed by an oral glucose tolerance test (OGTT) 5 weeks and 1 year after surgery hypothesizing higher GLP-1 levels and greater β-cell response to glucose after RYGB than after SG.

DESIGN, SETTING, PATIENTS, AND INTERVENTIONS: Randomized, triple blind, single-center trial at a tertiary care center in Norway. Primary outcomes; diabetes remission and IVGTT derived β-cell function. Participants with obesity and type 2 diabetes allocated (1:1) to RYGB or SG.

MAIN OUTCOME MEASURES: Gastrointestinal hormone profiles and insulin secretion [β-cell glucose sensitivity (β-GS)] derived from 180 minutes OGTTs.

RESULTS: 106 patients (67% women), mean (SD) age 48 (10) years. Diabetes remission rates at 1-year were higher after RYGB than after SG, 77% versus 48%, p = 0.002. Incremental area under the curve (iAUC0-180) glucagon-like peptide-1 (GLP-1) and β-GS increased more after RYGB than after SG, 1-year between-group difference 1173 pmol/l*min (95% CI 569 to 1776), p = 0.0010, and 0.45 pmol/kg/min/mmol (95% CI 0.15 to 0.75), p = 0.0032, respectively. Post-surgery, fasting and postprandial ghrelin levels were higher and decremental AUC0-180 ghrelin, iAUC0-180 glucose-dependent insulinotropic polypeptide, and iAUC0-60 glucagon were greater after RYGB than after SG. Diabetes remission at 1 year was associated with higher β-GS and higher GLP-1 secretion.

CONCLUSIONS: RYGB was associated with greater improvement in β-cell function and higher postprandial GLP-1 levels than SG.