In vivo effect of glucose-dependent insulinotropic peptide (GIP) on the gene expression of calcitonin peptides in human subcutaneous adipose tissue

Abstract

BackgroundIncreased plasma levels of calcitonin gene-related peptide‐I (CGRP-I) and procalcitonin (Pro-CT) (both also named calcitonin peptides (CT peptides)) are associated with obesity and systemic inflammation. Glucose-dependent insulinotropic polypeptide (GIP), a nutrient-dependent incretin hormone, was recently found to induce CGRP-I and CT expression in human adipocytes in vitro. However, a physiological relevance of a possible interaction between GIP and CT peptides has not yet been studied. MethodsIn this study, we analyzed the effect of GIP on the expression of CGRP-I and CT mRNA in human subcutaneous adipose tissue within a randomized, controlled trial. Seventeen male obese subjects were infused with GIP [2.0pmolkg−1min−1 for 240min] or placebo, either in the fasting state, during euglycemic–hyperinsulinemic (EC) or hyperglycemic–hyperinsulinemic clamps (HC). ResultsThe CGRP-I gene expression was detected in all investigated adipose tissue samples, whereas very low CT expression was found in only 8 out of 116 analyzed samples. No significant influence of either GIP or glucose and insulin infusions on the CGRP-I and CT expression was observed in any of the individual experiments (GIP infusion, EC and HC) or in the combined analysis of all experiments with and without GIP. Furthermore, CGRP-I expression was not correlated with plasma GIP level before or after 240min of infusions or clamps. ConclusionIn contrast to in vitro data, an acute application of GIP has no effect on mRNA expression of CT peptides in subcutaneous adipose tissue of obese humans.