Dipeptidyl peptidase-4 inhibitors do not alter GH/IGF-I axis in adult diabetic patients

Purpose: Incretin-based therapies have been introduced in clinical practice for type 2 diabetes mellitus (T2DM) treatment in the last few years. Current available medications of this class include glucagon-like peptide 1 (GLP-1) receptor agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors. In addition to GLP-1, DPP-4 is able to inactivate many others peptides as hypothalamic growth hormone-releasing hormone (GHRH). The aim of this exploratory study was to evaluate, on adult diabetic patients, the impact of therapy with incretins, particularly DPP-4 inhibitors on GH/IGF-I axis. Methods: 60 patients with T2DM were included in the study and they were divided into three groups (age and sex comparable) on the basis of their hypoglycemic drugs in the last 4 months: group 1 (17 patients, exenatide or liraglutide + metformin), group 2 (18 patients, sitagliptin or vildagliptin + metformin), group 3 (25 patients, metformin). Anthropometric data, glycemia, glycosylated hemoglobin (HbA1c), IGF-I and acid-labile subunit (ALS) were collected in all patients. Results: Weight, waist circumference and BMI of group 1 were significantly higher (P < 0.05) compared to the other groups. Fasting plasma glucose and HbA1c of the group 1 were similar compared to those of group 3 (P ns) and higher compared to those of group 2 (P < 0.05). IGF-I absolute values, IGF-I SDS were not significantly different in the three groups. Conclusions: Our data evidence that DPP-4 inhibition does not influence significantly GH/IGF-I system, confirming what was observed in animal models. Further studies are needed to better characterize the properties of these molecules on endocrine system