Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy.

This study explored lipid metabolism in horses afflicted with atypical myopathy, a severe muscle disease. The researchers found high excretion levels of various acids and glycines in the urine and plasma of the affected horses, pointing to a potential deficiency in mitochondrial dehydrogenases – a characteristic also observed in a similar human disease called glutaric acidemia type II.

Methods

• This research involved examination of urine samples from 10 horses suffering from atypical myopathy. These were measured for levels of various organic acids, glycine conjugates, and acylcarnitines.
• The horses’ results were compared with those of 15 control horses, 12 of which were healthy and three of which suffered from acute myopathy due to other causes.
• The team also tested the plasma of the affected horses for similar markers.
• Dehydrogenase activities in the lateral vastus muscle from one horse with atypical myopathy was measured and compared with two healthy horses.

Results

• The affected horses demonstrated increased excretion of substances like lactic acid, ethylmalonic acid, 2-methylsuccinic acid, and various glycines and carnitines when compared to the control horses.
• Similar results were seen in the plasma analysis for these predominantly short-chain acylcarnitines.
• The muscle analysis revealed deficiencies in short-chain acyl-CoA dehydrogenase, medium-chain acyl-CoA dehydrogenase, and isovaleryl-CoA dehydrogenase in the affected horse versus the controls.

Conclusion

• The team suspected that there was a deficiency in a number of mitochondrial dehydrogenases in all 10 cases studied. These are important enzymes that help to break down various acids and sarcosine. This kind of deficiency is also seen in a severe human disorder called glutaric acidemia type II.
• The researchers propose that these metabolic irregularities could explain the high fatality rate and prevalence of atypical myopathy, a toxic equine muscle disease.

This study therefore represents an important piece of research into understanding the metabolic mechanisms behind atypical myopathy in horses, which could guide future therapeutic strategies.