The Oseberg study demonstrated a higher one year remission rate of type 2 diabetes after Roux-en-Y gastric bypass (RYGB) than after sleeve gastrectomy (SG). To explore mechanisms for the superiority of RYGB we assessed changes in glucose, C-peptide and incretin hormones after a 25 g OGTT and an IVGTT and calculated Disposition Indexes (DI) of beta cell function (DIIVGTT and DIOGTT). We used linear mixed models for repeated measures. Patients randomized to either RYGB (n=54) or SG (n=55), had a mean (SD) age of 48 (10) years, BMI 42.3 (5.3) kg/m², HbA1c 66 (18) mmol/mol, and 72 (66%) were women. OGTT and IVGTT were performed in 97% and 91% of patients respectively. At one year, the OGTT-derived glucose levels at 60-120 minutes were significantly lower after RYGB than after SG (all p<0.05). The OGTT-derived increase in measures of C-peptide, GIP and GLP-1 from 0 to 15 minutes were significantly higher in the RYGB group, mean (95% CI) between group difference: C-peptide 257 (66, 448) pmol/L, p=0.008; GIP 11 (4, 19) pmol/L, p=0.005; and GLP-1 29 (20, 38) pmol/L, p<0.001. DIIVGTT and DIOGTT increased three- to fivefold in both groups with no significant difference between groups. Post-OGTT glucose levels were significantly lower after RYGB as compared with SG, possibly mediated by a greater increase in GIP, GLP-1 and C-peptide levels.
F. Fatima: Other Relationship; Self; South-Eastren Reagional Health Authority Norway. J. Hjelmesæth: Advisory Panel; Self; Novo Nordisk A/S. K.I. Birkeland: None. H.L. Gulseth: None. J.K. Hertel: None. M. Svanevik: None. R. Sandbu: None. B. Hartmann: None. J.J. Holst: Advisory Panel; Self; AstraZeneca, Merck Sharp & Dohme Corp., Novo Nordisk A/S, Zealand Pharma A/S. Other Relationship; Spouse/Partner; Antag Therapeutics. D. Hofsø: None.