AIMS: The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) influence metabolism through strong effects on pancreatic hormone secretion but also in a pancreas-independent manner. Here, we investigated the isolated extrapancreatic effects of endogenous GIP and GLP-1 by applying hormone receptor antagonists in totally pancreatectomized individuals.
METHODS: Twelve totally pancreatectomized individuals each underwent four 270-min liquid mixed meal tests (480 kcal) in a randomized study design with infusions of the GIP receptor antagonist GIP(3-30)NH(800 pmol/kg/min), the GLP-1 receptor antagonist exendin(9-39)NH(450 pmol/kg/min), GIP(3-30)NH + exendin(9-39)NH, and saline (placebo), respectively. Blood samples, appetite-related measures, heart rate, blood pressure, and ad libitum food intake data were collected. Participants continued their basal insulin but omitted bolus insulin in the morning of the experiment. 2 2 2 2
RESULTS: Infusions of GIP(3-30)NHand GIP(3-30)NH + exendin(9-39)NHattenuated meal-induced inhibition of bone resorption (carboxy-terminal collagen crosslinks) (nadir [mean ± SD] to 84 ± 9% and to 85 ± 8% of baseline, compared to placebo (64 ± 15%) (ps <0.05)). During exendin(9-39)NHand exendin(9-39)NH + GIP(3-30)NHco-infusion, GLP-1 plasma responses increased (ps <0.05). Infusion of GIP(3-30)NHor exendin(9-39)NHdid not affect other measurements. 2 2 2 2 2 2 2 2
CONCLUSION: Endogenous GIP contributes to the regulation of postprandial bone resorption independently of pancreatic factors. In contrast, GIP receptor and/or GLP-1 receptor antagonism had no measurable effects on glucose metabolism, gastric emptying, appetite, food intake, triglycerides, or haemodynamics, supporting a pancreatic contribution to some of these effects of the endogenous hormones, although the surgical reconstruction may have influenced the sensitivity of the targets.
