Investigation of glucagon-like peptide-1 response to six oral carbohydrates in ponies.
Authors: Carslake H B, Pinchbeck G L, Argo C M, Dugdale A H A, McGowan C M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary Glucagon-like peptide-1 (GLP-1) has been proposed as a potentially useful marker in equine insulin dysregulation, but its diagnostic value remained unclear. Researchers fed twelve ponies with varying insulin status six different dietary interventions—hay, soaked hay, haylage, an oral glucose test, an oral sugar test, and a proprietary cereal—whilst measuring glucose, insulin and GLP-1 responses in a randomised cross-over design. All interventions except the combined glucose-insulin tolerance test triggered a GLP-1 response within 30 minutes, with the highest carbohydrate loads (oral glucose and cereal, delivering 1.06 g/kg and 1 g/kg bodyweight respectively) producing significantly greater GLP-1 area-under-curve values than other feeds. Notably, GLP-1 responses did not differ between insulin dysregulated and non-dysregulated ponies, despite strong positive correlations between GLP-1 and insulin concentrations at individual time points and overall curves. These findings indicate that GLP-1 measurement offers limited clinical utility as a supplementary diagnostic test for insulin dysregulation or insulin resistance in ponies, suggesting practitioners should rely on established oral and intravenous dynamic testing protocols rather than GLP-1 quantification for ID assessment.
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Practical Takeaways
- •GLP-1 measurement should not be added to diagnostic protocols for identifying insulin dysregulation or resistance in ponies, as it does not differentiate affected from unaffected animals despite correlating with insulin levels
- •High non-structural carbohydrate feeds (glucose tests and breakfast cereal) consistently trigger GLP-1 responses within 30 minutes; this may inform timing of metabolic testing protocols
- •The strong GLP-1-insulin correlation confirms the incretin effect operates in ponies, but this relationship alone does not help identify dysregulation cases
Key Findings
- •All interventions except CGIT provoked GLP-1 response within 30 minutes in ponies
- •OGT and WEET (1.06 and 1 g/kg BW non-structural carbohydrate) produced significantly greater GLP-1 AUC than other interventions (P < 0.001)
- •Strong positive correlations existed between GLP-1 and insulin at individual timepoints (rs = 0.67, P < 0.001) and as AUC (rs = 0.66, P < 0.001)
- •GLP-1 response did not differ by insulin dysregulation or insulin resistance status, making it unsuitable as an adjunctive diagnostic test for ID or IR