Serum acylcarnitine profile in endurance horses with and without metabolic dysfunction.
Authors: van der Kolk J H, Thomas S, Mach N, Ramseyer A, Burger D, Gerber V, Nuoffer J-M
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Serum Acylcarnitine Profiling in Endurance Horses Mitochondrial fatty acid oxidation (β-oxidation) becomes the primary energy substrate for horses competing in endurance races exceeding 80 km, as muscle glycogen stores become depleted during prolonged exercise. Van der Kolk and colleagues used electrospray tandem mass spectrometry to measure serum acylcarnitine profiles in 10 Arab endurance horses before and after a 160 km race, comparing metabolic responses between horses that successfully completed the race and four that showed poor performance. Finishing horses demonstrated an eight-fold increase in β-oxidation capacity (5,649 to 44,243 nmol/L) alongside a 17-fold rise in non-esterified fatty acids (0.08 to 1.32 mmol/L), indicating robust fat mobilisation and utilisation; poor-performing horses showed markedly blunted responses, with only a five-fold increase in β-oxidation and a 29-fold increase in circulating NEFA that was not effectively oxidised. Critically, both groups maintained similar free carnitine to acetylcarnitine ratios post-race despite their divergent performance outcomes, suggesting that carnitine availability—rather than oxidative capacity per se—may represent a limiting factor in endurance horse performance. For practitioners working with endurance competitors, these findings point towards carnitine status as a potential metabolic marker worthy of investigation and targeted nutritional support.
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Practical Takeaways
- •Serum acylcarnitine profiling can help identify endurance horses with metabolic dysfunction affecting fat oxidation capacity, enabling targeted nutritional or training interventions
- •Poor performance in endurance events may reflect impaired mitochondrial fatty acid utilization rather than inadequate energy mobilization; carnitine supplementation warrants investigation
- •Horses competing in races over 80 km depend almost entirely on β-oxidation of fatty acids due to glycogen depletion, making metabolic efficiency assessment critical for pre-race evaluation
Key Findings
- •Endurance exercise increased mitochondrial β-oxidation approximately 8-fold in finishing horses (5648.62 to 44,243.17 nmol/L, P=0.001)
- •Poor-performing horses showed only a 5-fold increase in β-oxidation despite a 29-fold increase in NEFA, suggesting impaired fatty acid utilization
- •Both groups had similar post-exercise free carnitine:acetylcarnitine ratios, indicating carnitine availability may limit endurance performance
- •High-performing horses demonstrated a 17-fold increase in lipolysis (NEFA 0.08 to 1.32 mmol/L) compared to poor-performers (0.02 to 0.58 mmol/L)