Endocrine Abstracts

JOINT341

Introduction: Bariatric surgery improves beta-cell function and insulin sensitivity in people with type 2 diabetes short-term. Comparative long-term data on the glycaemic effects of gastric bypass vs sleeve gastrectomy remain limited.

Methods: Prespecified secondary analyses of a two-armed, single centre, RCT conducted at Vestfold Hospital Trust (Norway). Adult patients with obesity and type 2 diabetes were randomised (1:1) to undergo either gastric bypass or sleeve gastrectomy and were followed for 5 years. The study assessed changes from baseline in beta-cell glucose sensitivity (modelled from c-peptide deconvolution), postprandial GLP-1 hormone profile, and intestinal absorption rate of paracetamol, using a 25g 180-minute oral glucose tolerance test (OGTT). Acute insulin response to glucose (AIRg) and peripheral insulin sensitivity (Si) were estimated with a 180- minute intravenous glucose tolerance test (IVGTT). Outcomes were assessed according to intention to treat principles utilizing generalized linear mixed models for repeated measures using identity link. Statistical analyses; Stata (version 18).

Results: A total of 109 patients were randomised to gastric bypass (n = 54) or sleeve gastrectomy (n = 55). The baseline demographic characteristics were comparable between the groups (mean age 47. 7 years [SD 9. 6], BMI 42. 3 kg/m² [5. 3], HbA1c 8. 1% [1. 7], and 72 [66%] were women). At 5-year follow-up, 73 (67%) participants underwent an OGTT and an IVGTT. During follow-up, beta-cell glucose sensitivity increased three-fold following gastric bypass, compared with a two-fold increase after sleeve gastrectomy, between-group difference 0. 35 pmol/kg/min/mmol (95%CI [0. 01 to 0. 70]; P = 0. 042). The incremental area under the curve (iAUC_0-180) for GLP-1 increased after gastric bypass only, between-group difference 797 pmol/l*min (95%CI [172 to 1422]; P = 0. 012). AIRg increased two- to three-fold in both surgical groups (between-group difference: -54 mU/l per min [95%CI [-144 to 36], P = 0. 239]), and Si approximately doubled in each group (between-group difference: 0. 3 mU/l^-1*min^-1 [95% CI -0. 4 to 1. 0, P = 0. 358]). Paracetamol peak concentration (C_max) was higher, whilst time to peak concentration (T_max) was shorter after gastric bypass than after sleeve gastrectomy, between-group difference 57 mmol/l (95%CI [44 to 71]; P < 0. 001) and -27 minutes (95%CI [-36 to -18]; P < 0. 001), respectively.

Discussion: The insulin secretion and peripheral insulin sensitivity improved similarly during 5 years of follow-up after both surgical procedures. However, gastric bypass was associated with higher paracetamol and GLP-1 levels, and a greater insulin response to changes in glucose levels after an oral glucose-paracetamol load. This suggests accelerated gastric emptying, and a more pronounced influence on the entero-insular axis after gastric bypass as compared with sleeve gastrectomy.