RESUMEN
Glucagon-like peptide-1 (GLP-1), the principal incretin in horses, may play a role in the pathophysiology of insulin dysregulation (ID). This study aimed to describe its concentration in response to three preserved forages and four dynamic tests for ID in ponies. Twelve adult ponies of mixed ID status were given a meal of hay, soaked hay or haylage, an in-feed oral glucose test (OGT), oral sugar test (OST), an oral test using a proprietary breakfast cereal (WEET) or a combined glucose-insulin tolerance test (CGIT) weekly in a randomised cross-over study. Glucose, insulin and GLP-1 concentrations were measured before and following each intervention. Ponies were designated ID or non-ID and insulin resistant (IR) or non-IR according to OGT and CGIT results, respectively. All interventions apart from the CGIT provoked a GLP-1 response within 30â¯min. The OGT and WEET interventions, (containing the greatest dose of non-structural carbohydrate, 1.06 and 1â¯g/kg BW, respectively), resulted in a greater area under the curve (AUC) for GLP-1 compared to all other interventions (Pâ¯<â¯0.001). No difference in GLP-1 response was detected according to ID or IR status, despite there being strong positive correlations (rs [95â¯% CI]) between GLP-1 and insulin concentrations measured at individual time points (0.67 [0.62 - 0.71]; Pâ¯<â¯0.001) and as AUC (0.66 [0.49-0.79], Pâ¯<â¯0.001). These data do not support of the use of GLP-1 as an adjunctive diagnostic test for ID or IR, as defined by conventional intravenous or oral dynamic tests.
Asunto(s)
Estudios Cruzados , Péptido 1 Similar al Glucagón , Prueba de Tolerancia a la Glucosa , Animales , Péptido 1 Similar al Glucagón/metabolismo , Péptido 1 Similar al Glucagón/sangre , Caballos , Masculino , Prueba de Tolerancia a la Glucosa/veterinaria , Insulina/sangre , Femenino , Alimentación Animal/análisis , Glucemia/análisis , Carbohidratos de la Dieta , Resistencia a la InsulinaRESUMEN
Several tests have been advocated for diagnosis of insulin dysregulation (ID). Tests using simple sugars may not reflect the response to naturally ingested carbohydrates. This study aimed to evaluate agreement between the oral glucose test (OGT), the oral sugar test (OST), a novel oral test using a proprietary cereal (WEET), the IV combined glucose-insulin tolerance test (CGIT) and fasted basal insulin (FI) for diagnosis of ID. Each of the five tests above was performed on a group of six normal and six insulin dysregulated mixed-breed ponies in a randomised crossover study. Area under the curve (AUC) and maximum concentration of insulin from OGT, OST and WEET showed strong to very strong bivariate correlations (r = 0.85-0.94, and r = 0.87-0.92, respectively; P ≤ 0.001) and were significantly different between tests (associated with dose of carbohydrate) and between CGIT-positive and -negative ponies. Dichotomous results showed substantial agreement between OST and both WEET (κ = 0.65; P = 0.02) and OGT (κ = 0.67; P = 0.01) and between CGIT and both OST (κ = 0.63; P = 0.03) and OGT (κ = 0.67; P = 0.01), and no agreement between FI, which had low sensitivity, and all other tests (κ = 0.15 - 0.31; P > 0. 05). Palatability of WEET was variable, resulting in one pony being excluded for analysis of WEET data. Further work on development of an oral test using a more palatable feedstuff and appropriate cut-offs or diagnostic thresholds for tests of ID is warranted.