Background: The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP-1) augment post-prandial insulin secretion. Managing equine insulin dysregulation (ID) often involves feeding high-protein ration balancers. Recent studies suggest that dietary amino acids can promote GIP secretion, enhancing post-prandial [insulin]; this may increase the risk of hyperinsulinemia following consumption of high-protein meals in horses with ID.
Hypothesis: Consumption of high-protein meals will increase post-prandial [GIP] and [GLP-1] in horses with experimentally-induced ID. Animals: Adult light-breed horses with normal [ACTH] (n = 7).
Methods: Each horse underwent a frequently-sampled insulin-modified IV glucose tolerance test to characterize systemic insulin/glucose dynamics and a feed challenge test (FCT; 1 kg ration balancer [min 32% CP, max 13% NSC] consumed within 15 minutes, [GIP] and [GLP-1] measured 0-240 minutes afterward). Both tests were repeated after induction of ID (dexamethasone, 0.08 mg/kg PO SID, 7 days). Outcomes, including [GIP] and [GLP-1] during the FCT, were compared between baseline and ID.
Results: [GIP] and [insulin] increased after a high-protein meal; ID AUC-GIP (1166 ± 363 pg/mL) was significantly higher than baseline AUC-GIP (767 ± 199 pg/mL; P = 0.014). There was no difference in AUC-GLP-1 between baseline (50.7 ± 16.6 pg/mL) and ID (39.1 ± 25.3 pg/mL; P = 0.47).
Conclusions and Clinical Importance: Horses with experimentally-induced ID displayed significantly greater GIP responses to a high-protein meal than at baseline, suggesting that GIP plays a role exacerbating post-prandial hyperinsulinemia in this context.
