Effect of dietary fructans and dexamethasone administration on the insulin response of ponies predisposed to laminitis.
Authors: Bailey, Menzies-Gow, Harris, Habershon-Butcher, Crawford, Berhane, Boston, Elliott
Journal: Journal of the American Veterinary Medical Association
Summary
# Editorial Summary Insulin resistance is a known risk factor for laminitis in horses and ponies, yet identifying at-risk individuals without obesity remains clinically challenging. Bailey and colleagues investigated whether dietary fructans and dexamethasone administration could unmask compensated insulin resistance in laminitis-predisposed (LP) ponies, comparing their responses to healthy controls across several experimental conditions. LP ponies demonstrated inherent insulin resistance (insulin sensitivity 0.27 vs 0.64 × 10⁴ L min⁻¹ mU⁻¹), with serum insulin concentrations significantly elevated at pasture, declining on hay alone, then increasing 5.5-fold when inulin (a fructan) was added at 3 g/kg bodyweight daily—a striking metabolic response absent in control ponies. The dexamethasone suppression test similarly revealed the LP group's dysregulation: their serum insulin surged to 222.9 mU/L at 19 hours post-administration compared with just 45.6 mU/L in controls, indicating the underlying insulin resistance becomes exaggerated under metabolic stress. These findings have practical significance for identifying laminitis risk: non-obese ponies showing excessive insulin elevation following fructan challenge or corticosteroid use warrant dietary management and closer laminitis monitoring, whilst the dramatic response to inulin highlights why pasture restriction and careful hay selection remain crucial preventive strategies for susceptible individuals.
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Practical Takeaways
- •Laminitis-prone ponies should be managed on restricted hay diets rather than pasture; avoid dietary supplements containing inulin and other fructans that trigger marked insulin spikes
- •High insulin response to stress (including medications like dexamethasone) in susceptible ponies warrants careful monitoring during illness or treatment protocols
- •Identifying and managing insulin resistance through diet before clinical laminitis develops may be critical for prevention in predisposed animals
Key Findings
- •Laminitis-predisposed ponies demonstrated insulin resistance with median insulin sensitivity of 0.27 × 10⁴ L min⁻¹ mU⁻¹ compared to 0.64 × 10⁴ in controls
- •Pasture feeding induced significantly higher serum insulin in LP ponies, which decreased on hay diet but increased 5.5-fold when inulin was added to hay
- •LP ponies showed exaggerated insulin response to dexamethasone suppression test (222.9 mU/L at 19 hours) versus controls (45.6 mU/L)
- •Compensated insulin resistance phenotype in laminitis-predisposed ponies can be revealed through dietary fructan supplementation or dexamethasone administration