Direct identification of propionylcarnitine in propionic acidaemia: biochemical and clinical results of oral carnitine supplementation.

Urinary short-chain acylcarnitine in a patient with propionic acidaemia and low levels of free carnitine was found to consist mainly of propionylcarnitine. The compound was isolated by sequential paper and thin layer chromatography and identified by ammonia desorption chemical ionization mass spectrometry. Treatment of the patient with oral carnitine supplements led to a near-normalization of the plasma free carnitine concentrations and an increase in his muscle tone. The propionylcarnitine excretion rose and there was a simultaneous decrease in the methylcitrate output. Carnitine treatment did not prevent the occurrence of an episode of metabolic decompensation.

Octanoylglucuronide excretion in patients with a defective oxidation of medium-chain fatty acids.

Octanoyl-beta-D-glucuronide was identified in the urine of five patients with hypoketotic hypoglycemia and dicarboxylic aciduria due to a defective beta-oxidation of medium-chain fatty acids. Two subjects who ingested large amounts of medium-chain triglycerides also excreted large amounts of the glucuronide. The substance was extracted from the urine with ethyl acetate and analyzed by: (1) gas chromatography/mass spectrometry (GC-MS) of the trimethylsilyl derivative and (2) preparative one-dimensional thin-layer chromatography followed by enzymatic hydrolysis with beta-glucuronidase and again GC-MS. A quantitative analysis was performed indirectly by measuring the urinary bound octanoate after the removal of octanoylcarnitine. Octanoylglucuronide represents an additional mechanism for the detoxification of octanoate; its formation may be of help for the maintenance of carnitine homeostasis in patients with medium-chain acyl-CoA dehydrogenase deficiency.