BACKGROUND: Corticosteroids are used routinely in horses and induce insulin dysregulation (ID). Nutrition is important for ID management and includes low nonstructural carbohydrate (NSC) diets and, often, high-protein ration balancers (RB). Insulin and incretin secretion increase after high-protein meals
corticosteroids may influence these effects. HYPOTHESIS: A high-protein mixed meal will induce hyperinsulinemia and increased concentrations of glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) in horses with ID
dexamethasone (DEX) will amplify this effect. ANIMALS: Five horses with naturally occurring ID. METHODS: Horses underwent an IV glucose tolerance test and a feed challenge test (FCT
1 kg RB). Tests were repeated after DEX administration (0.08 mg/kg PO q24h, 7 days). Insulin, glucose, and incretin dynamics were compared pre- and post-DEX. RESULTS: Corticosteroids exacerbated post-prandial hyperinsulinemia and hyperglycemia after a high-protein meal. The FCT area under the curve for insulin (AUC CONCLUSIONS AND CLINICAL IMPORTANCE: Metabolic responses to a high-protein mixed meal were exacerbated by corticosteroids. Horses receiving corticosteroids had larger GIP responses, which may enhance post-prandial hyperinsulinemia.