Endogenous Glucose-Dependent Insulinotropic Polypeptide Contributes to Sitagliptin-Mediated Improvement in β-Cell Function in Patients With Type 2 Diabetes

Signe Stensen, Lærke S Gasbjerg, Mette M Rosenkilde, Tina Vilsbøll, Jens J Holst, Bolette Hartmann, Mikkel B Christensen, Filip K Knop

Abstract

Dipeptidyl peptidase 4 (DPP-4) degrades the incretin hormones glucagon-like peptide 1 and glucose-dependent insulinotropic polypeptide (GIP). DPP-4 inhibitors improve glycemic control in type 2 diabetes, but the importance of protecting GIP from degradation for their clinical effects is unknown. We included 12 patients with type 2 diabetes (mean ± SD BMI 27 ± 2.6 kg/m2, HbA1c 7.1 ± 1.4% [54 ± 15 mmol/mol]) in this double-blind, placebo-controlled, crossover study to investigate the contribution of endogenous GIP to the effects of the DPP-4 inhibitor sitagliptin. Participants underwent two randomized, 13-day treatment courses of sitagliptin (100 mg/day) and placebo, respectively. At the end of each treatment period, we performed two mixed-meal tests with infusion of the GIP receptor antagonist GIP(3-30)NH2 (1,200 pmol/kg/min) or saline placebo. Sitagliptin lowered mean fasting plasma glucose by 1.1 mmol/L compared with placebo treatment. During placebo treatment, postprandial glucose excursions were increased during GIP(3-30)NH2 compared with saline (difference in area under the curve ± SEM 7.3 ± 2.8%) but were unchanged during sitagliptin treatment. Endogenous GIP improved β-cell function by 37 ± 12% during DPP-4 inhibition by sitagliptin. This was determined by the insulin secretion rate/plasma glucose ratio. We calculated an estimate of the absolute sitagliptin-mediated impact of GIP on β-cell function as the insulinogenic index during sitagliptin treatment plus saline infusion minus the insulinogenic index during sitagliptin plus GIP(3-30)NH2. This estimate was expressed relative to the maximal potential contribution of GIP to the effect of sitagliptin (100%), defined as the difference between the full sitagliptin treatment effect, including actions mediated by GIP (sitagliptin + saline), and the physiological response minus any contribution by GIP [placebo treatment + GIP(3-30)NH2]. We demonstrate insulinotropic and glucose-lowering effects of endogenous GIP in patients with type 2 diabetes and that endogenous GIP contributes to the improved β-cell function observed during DPP-4 inhibition.

Original languageEnglish
JournalDiabetes
Volume71
Issue number10
Pages (from-to)2209-2221
Number of pages13
ISSN0012-1797
DOIs
Publication statusPublished - 1 Oct 2022

Keywords

  • Blood Glucose/metabolism
  • Cross-Over Studies
  • Diabetes Mellitus, Type 2/metabolism
  • Dipeptidyl Peptidase 4
  • Dipeptidyl-Peptidase IV Inhibitors/pharmacology
  • Double-Blind Method
  • Gastric Inhibitory Polypeptide/metabolism
  • Glucagon-Like Peptide 1/metabolism
  • Glycated Hemoglobin A
  • Humans
  • Incretins/metabolism
  • Receptors, Gastrointestinal Hormone
  • Sitagliptin Phosphate/pharmacology

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