Equine atypical myopathy: A metabolic study.
Authors: Karlíková R, Široká J, Jahn P, Friedecký D, Gardlo A, Janečková H, Hrdinová F, Drábková Z, Adam T
Journal: Veterinary journal (London, England : 1997)
Summary
Atypical myopathy (AM) represents a serious metabolic emergency in grazing horses, with hypoglycin A from sycamore seeds implicated as the causative toxin, yet the full biochemical picture of how this toxin disrupts equine metabolism remained unclear. Researchers analysed serum and urine samples from nine affected horses and twelve healthy controls using high-performance liquid chromatography with tandem mass spectrometry, examining metabolic signatures both at disease presentation and as clinical progression occurred. The study identified substantial alterations across multiple metabolic pathways: acylcarnitines (C2–C26) and glycine conjugates showed marked derangement, alongside significant changes in purine and pyrimidine metabolism, B-vitamin status (riboflavin, pyridoxate, pantothenate), and key amino and organic acids including aspartate, leucine and 2-oxoglutarate. These findings demonstrate that AM causes widespread metabolic dysfunction beyond simple carnitine depletion, affecting energy metabolism, nucleotide synthesis and crucial cofactor availability. For practitioners, understanding this broader metabolic profile may help refine supportive care strategies and inform earlier recognition of the disease's multi-system effects, whilst highlighting the importance of pasture management during high-risk periods when sycamore seed fall occurs.
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Practical Takeaways
- •Metabolic fingerprinting via LC-MS/MS can serve as a diagnostic tool to confirm atypical myopathy in grazing horses presenting with myopathy signs
- •Recognize that AM involves widespread metabolic derangement affecting energy metabolism (acylcarnitines), amino acid metabolism, and B vitamin pathways—not isolated muscle injury
- •If sycamore seeds are present in pastures during autumn/winter, heightened vigilance for AM is warranted; metabolic testing can expedite diagnosis and guide supportive care decisions
Key Findings
- •Significant alterations in glycine conjugates and acylcarnitines (C2-C26) detected in horses with atypical myopathy versus controls
- •Purine and pyrimidine metabolite concentrations were significantly altered in affected horses
- •Vitamin-related metabolites (riboflavin, trigonelline, pyridoxate, pantothenate) and specific amino acids (aspartate, leucine) and organic acids (2-oxoglutarate) showed dysregulation in AM cases
- •Metabolic profiling using LC-MS/MS successfully differentiated horses with atypical myopathy from healthy controls