Detection of MCPG metabolites in horses with atypical myopathy.
Authors: Bochnia Mandy, Sander Johannes, Ziegler Joerg, Terhardt Michael, Sander Stefanie, Janzen Nils, Cavalleri Jessika-M V, Zuraw Aleksandra, Wensch-Dorendorf Monika, Zeyner Annette
Journal: PloS one
Summary
Atypical myopathy (AM) in horses has been attributed primarily to hypoglycin A (HGA) from Acer seeds, but this 2019 study investigated whether methylenecyclopropylglycine (MCPG)—a structurally similar compound found in various Sapindaceae fruits—also contributes to the disease. Using high-performance liquid chromatography-tandem mass spectrometry, researchers quantified MCPG and its metabolites (MCPF-glycine and MCPF-carnitine) alongside HGA derivatives in serum and urine samples from horses that had consumed *Acer pseudoplatanus* seeds and developed clinical AM, compared with healthy controls. MCPG and its active metabolites were detected in affected horses alongside the previously identified HGA metabolites, and strong inhibition of β-oxidation was evident from elevated acyl glycines and carnitines—notably, MCPF-carnitine correlated strongly with isobutyryl-carnitine (r = 0.93), suggesting potent disruption of fatty acid metabolism. These findings broaden our understanding of AM aetiology beyond HGA alone and have implications for both diagnostic protocols and risk assessment, particularly regarding exposure to other Sapindaceae species that may pose similar toxicity risks to grazing horses. Professionals involved in investigating AM cases, whether through clinical diagnosis or toxicological screening, should now account for MCPG metabolites when evaluating biochemical markers of poisoning.
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Practical Takeaways
- •When investigating suspected atypical myopathy cases with Acer seed exposure, ensure diagnostic laboratories measure both HGA-derived and MCPG-derived metabolites for accurate diagnosis
- •Understanding that multiple toxic metabolites contribute to AM pathogenesis helps explain the severity and variable presentation of cases in practice
- •Recognition that Sapindaceae family seeds beyond just Acer species (ackee, lychee, longan) contain MCPG suggests broader risk for toxicity than previously thought
Key Findings
- •MCPG and its metabolites (MCPF-glycine, MCPF-carnitine) were detected in serum and urine of horses with atypical myopathy following Acer pseudoplatanus seed ingestion
- •Both HGA and MCPG-derived metabolites were present in affected horses, indicating dual toxic pathways in Acer seed poisoning
- •Strong correlations were found between MCPF-carnitine and isobutyryl-carnitine (r=0.93) and between MCPF-glycine and valeryl-glycine (r=0.87), indicating severe β-oxidation inhibition
- •MCPG must be included in biochemical diagnostic analysis for atypical myopathy to accurately assess poisoning mechanisms