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Effects of endogenous GIP in patients with type 2 diabetes.

Center for Clinical Metabolic Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark. Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Antag Therapeutics Aps, Copenhagen, Denmark. Department of Geriatrics, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark. Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Steno Diabetes Center Copenhagen, Gentofte, Denmark. Department of Clinical Pharmacology, Bispebjerg Hospital, University of Copenhagen, Copenhagen, Denmark.

European journal of endocrinology. 2021;(1):33-45
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Abstract

OBJECTIVE The insulinotropic effect of exogenous, intravenously infused glucose-dependent insulinotropic polypeptide (GIP) is impaired in patients with type 2 diabetes. We evaluated the effects of endogenous GIP in relation to glucose and bone metabolism in patients with type 2 diabetes using a selective GIP receptor antagonist and hypothesized that the effects of endogenous GIP were preserved. DESIGN A randomized, double-blinded, placebo-controlled, crossover study. METHODS Ten patients with overweight/obesity and type 2 diabetes (mean±s.d.; HbA1c 52 ± 11 mmol/mol; BMI 32.5 ± 4.8 kg/m2) were included. We infused a selective GIP receptor antagonist, GIP(3-30)NH2 (1200 pmol/kg/min), or placebo (saline) during two separate, 230-min, standardized, liquid mixed meal tests followed by a meal ad libitum. Subcutaneous adipose tissue biopsies were analyzed. RESULTS Compared with placebo, GIP(3-30)NH2 reduced postprandial insulin secretion (Δbaseline-subtracted area under the curve (bsAUC)C-peptide% ± s.e.m.; -14 ± 6%, P = 0.021) and peak glucagon (Δ% ± s.e.m.; -11 ± 6%, P = 0.046) but had no effect on plasma glucose (P = 0.692). Suppression of bone resorption (assessed by circulating carboxy-terminal collagen crosslinks (CTX)) was impaired during GIP(3-30)NH2 infusion compared with placebo (ΔbsAUCCTX; ±s.e.m.; -4.9 ± 2 ng/mL × min, P = 0.005) corresponding to a ~50% reduction. Compared with placebo, GIP(3-30)NH2 did not affect plasma lipids, meal consumption ad libitum or adipose tissue triglyceride content. CONCLUSIONS Using a selective GIP receptor antagonist during a meal, we show that endogenous GIP increases postprandial insulin secretion with little effect on postprandial glycaemia but is important for postprandial bone homeostasis in patients with type 2 diabetes.