Equine intern University of Edinburgh Roslin, England, United Kingdom
Abstract:
Background: In human obesity and insulin dysregulation (ID), adrenal activation often exacerbates metabolic dysfunction. However, limited information exists on equine obesity or equine metabolic syndrome (EMS).
Hypothesis: Obesity is associated with adrenal activation and EMS horses show an amplified adrenal response to an oral glycaemic challenge test.
Animals: Serum samples from a prior multicentred prospective case-control study in the UK, Germany, and Sweden comprised of 31 healthy and 40 EMS-diagnosed horses, both university and privately-owned were utilized.
Methods: Serum was analysed by LC-MS/MS for quantification of 18 steroids, pre and post the glycaemic test. Multivariate regression models and two-way ANOVAs determined the relationship between steroids and obesity/EMS, and the effect of obesity/EMS on response to the test.
Results: The final model best predicting obesity (BCS >6/9) was increased cortisol and decreased corticosterone and cortisone (P = 0.02, NPP 69.7%, PPV 70.83%). Decreased aldosterone was predictive of EMS (P = 0.01, NPV 66.7, PPV 80%). No good predictors of regional adiposity were identified. The glycaemic challenge test increased progesterone (P=0.003) and decreased cortisone in all animals. Obesity was associated with an increased 11-deoxycortisol response to glucose (P=0.04). EMS animals showed a significant increase in cortisol (P=0.02), corticosterone (P=0.04), 11-deoxycortisol (P=0.03), and 11-deoxycorticosterone (P=0.03) compared to healthy animals.
Conclusions: The study concludes that obesity is linked with adrenal activation, with a compensatory change in cortisol to cortisone metabolism. EMS results in an exaggerated glucocorticoid response to a glycaemic challenge, both raising pathophysiological and clinical questions for further investigation.
