85-LB: Glucose-Dependent Insulinotropic Polypeptide (GIP) Contributes Substantially to the Improved Beta-Cell Function during Sitagliptin Treatment in Persons with Type 2 Diabetes
Authors: STENSEN SIGNE , GASBJERG LÆRKE S. , ROSENKILDE METTE M. , HARTMANN BOLETTE , VILSBØLL TINA , HOLST JENS J. , CHRISTENSEN MIKKEL B. , KNOP FILIP K. 
Published: June 2021

In persons with type 2 diabetes (T2D), dipeptidyl peptidase 4 (DPP-4) inhibitor treatment improves glycemic control by raising the active levels of the insulinotropic gut hormones glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide (GIP). Using the GIP receptor antagonist GIP(3-30)NH2, we investigated endogenous GIP’s contribution to the insulinotropic effect of DPP-4 inhibition (assessed by insulin secretion rate (ISR) relative to plasma glucose). In a double-blind, placebo-controlled, cross-over study, 12 persons (eight men and four women) with T2D (mean ± SD; BMI 27.4 ± 2.6 kg/m2, HbA1c 7.1 ± 1.4% (54 ± 15 mmol/mol)) underwent two randomized 12-13-day treatment courses with DPP-4 inhibitor (sitagliptin 100 mg once-daily) and placebo, respectively, with an interposed 1-3-week washout period. In the end of each treatment period, two randomized 5-hour liquid mixed-meal tests with infusion of GIP(3-30)NH2 (1,200 pmol/kg/min) or saline (placebo) were performed. During placebo treatment, GIP(3-30)NH2 lowered postprandial serum C-peptide (determined as difference in baseline-subtracted area under curve (ΔbsAUC%) ± SEM: −31 ± 9%, P = 0.005) and increased postprandial plasma glucose excursions (ΔAUC% ± SEM: 7.3 ± 2.8%, P = 0.017) compared to saline. Sitagliptin increased concentrations of active GIP(1-42) (ΔAUC% ± SEM: 153 ± 21%, P &lt; 0.0001) and lowered fasting plasma glucose (mean: 8.7 vs. 7.6 mmol/L, P &lt; 0.0004), whereas postprandial glucose excursions were unchanged compared to placebo treatment. GIP(3-30)NH2 caused a reduction in AUCISR/AUCglucose ratio equivalent to 37 ± 12% of the increments due to sitagliptin. In conclusion, we demonstrate an insulinotropic and glucose-lowering effect of endogenous GIP in persons with T2D and show that endogenous GIP is responsible for more than one third of the improved beta cell function observed during DPP-4 inhibitor treatment.

Disclosure
S. Stensen: None. L. S. Gasbjerg: Stock/Shareholder; Self; Antag Therapeutics. M. M. Rosenkilde: Board Member; Self; Bainan Biotech, Synklino ApS, Board Member; Spouse/Partner; Antag Therapeutics, Bainan Biotech, Consultant; Self; Antag Therapeutics, Bainan Biotech, Synklino ApS, Stock/Shareholder; Self; Antag Therapeutics, Bainan Biotech, Synklino ApS, Stock/Shareholder; Spouse/Partner; Antag Therapeutics, Bainan Biotech. B. Hartmann: None. T. Vilsbøll: Consultant; Self; Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Bristol-Myers Squibb Company, Gilead Sciences, Inc., Lilly Diabetes, Merck Sharp & Dohme Corp., Mundipharma International, Novo Nordisk, Sanofi, Sun Pharmaceutical Industries Ltd. J. J. Holst: Consultant; Self; Novo Nordisk, Other Relationship; Self; Antag Therapeutics, Bainan Biotech, MSD Corporation, Novo Nordisk, Other Relationship; Spouse/Partner; Antag Therapeutics, Bainan Biotech, Synklino ApS. M. B. Christensen: None. F. K. Knop: Advisory Panel; Self; MSD Corporation, Novo Nordisk A/S, Sanofi, Consultant; Self; AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, Novo Nordisk A/S, Pharmacosmos, Zealand Pharma A/S, Research Support; Self; Novo Nordisk A/S, Zealand Pharma A/S, Speaker’s Bureau; Self; AstraZeneca, Bayer AG, Boehringer Ingelheim Pharmaceuticals, Inc., Eli Lilly and Company, MSD Corporation, Novo Nordisk A/S.

Funding
European Foundation for the Study of Diabetes/Lilly European Diabetes Research Programme (2018); A.P. Møller Foundation