Involvement of glucagon-like peptide 1 in the glucose homeostasis regulation in obese and pituitary-dependent hyperadrenocorticism affected dogs

•GLP-1 and insulin are increased in PDH affected dogs.•Insulin resistance is more serious in PDH affected dogs than obese dogs.•Dogs affected with PDH fail to control insulin resistance.•HOMA indices are more altered in dogs with PDH. The incretin glucagon-like peptide 1 (GLP-1) enhances insulin secretion. The aim of this study was to assess GLP-1, glucose and insulin concentrations, Homeostatic Model Assessment (HOMAinsulin sensitivity and HOMAβ-cell function) in dogs with pituitary-dependent hyperadrenocorticism (PDH), and compare these values with those in normal and obese dogs. The Oral Glucose Tolerance Test was performed and the glucose, GLP-1 and insulin concentrations were evaluated at baseline, and after 15, 30, 60 and 120 minutes. Both basal concentration and those corresponding to the subsequent times, for glucose, GLP-1 and insulin, were statistically elevated in PDH dogs compared to the other groups. Insulin followed a similar behaviour together with variations of GLP-1. HOMAinsulin sensitivity was statistically decreased and HOMAβ-cell function increased in dogs with PDH. The higher concentrations of GLP-1 in PDH could play an important role in the impairment of pancreatic β-cells thus predisposing to diabetes mellitus.