(P20-017-25) Glucose-Dependent Insulinotropic Polypeptide and Glucagon After Weight Loss Induced by Diet or Bariatric Surgery

Objectives: The aim of this research was to compare the effects of a very low-energy diet (VLED), alone or combined with sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB), on glucose-dependent insulinotropic polypeptide (GIP) and glucagon plasma concentrations, and to investigate potential associations between these hormones and metabolic health.

Methods: Data from the parent study (The effect of DIet-induced weight loss versus Sleeve gastrectomy and Gastric bypass on Appetite, DISGAP) were used for this analysis. Participants with severe obesity underwent 10 weeks of a VLED alone (n=15) or combined with SG (n=15) or RYGB (n=14). Fasting and postprandial plasma concentrations of glucagon and GIP, insulin sensitivity indices, respiratory quotient (RQ), and resting energy expenditure (REE) were measured pre-and post-intervention. The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and the Matsuda Index were used as insulin sensitivity indices. Differences in hormonal profiles between groups at follow-up were evaluated using ANCOVA (after adjusting for concentrations at baseline). Associations between changes in hormones and metabolic outcomes were tested using regression analysis.

Results: Glucagon levels (fasting and area under the curve (AUC)) were higher, while postprandial GIP levels were lower after RYGB compared to SG and VLED (p < 0.05). Increased postprandial glucagon was associated with decreased Matsuda Index in the RYGB group (p < 0.01), and positively associated with increased REE in all groups (p=0.02). Increased fasting GIP was positively correlated with increased RQ (p=0.03) and HOMA-IR in all groups (p < 0.01).

Conclusions: RYGB showed lower GIP and greater glucagon concentrations compared to the other weight loss treatments. Future research should investigate how these hormones influence metabolic health and post-treatment outcomes.

Funding Sources: Liaison Committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology (NTNU) and the W.T. Garvey Endowed Scholarship.