Bile acylcarnitine profiles in pediatric liver disease do not interfere with the diagnosis of long-chain fatty acid oxidation defects.
BACKGROUND
Plasma acylcarnitine measurement is an important diagnostic tool for inherited disorders of fatty acid and organic acid metabolism. Biliary excretion has been shown to be the primary route of excretion for acylcarnitines and analysis of bile acylcarnitine profiles may provide greater sensitivity for detecting metabolic disorders. Disorders of fatty acid oxidation frequently present with deranged liver function and the effect of hepatic disease on biliary acylcarnitine excretion are unknown.


METHODS
We measured biliary acylcarnitine levels in pediatric patients aged 6 months to 1 year undergoing open liver biopsy with prospectively determined non-metabolic liver disease in order to determine the effect of the liver disease on acylcarnitine excretion. Bile was collected in syringes and was transported immediately and stored at -70 degrees C until the time of testing. The disease patient population consisted of 2 patients with known defects in long- and short-chain fatty acid oxidation (long-chain L-3-hydroxy acyl-CoA dehydrogenase: LCHAD and short-chain L-3-hydroxy acyl-CoA dehydrogenase: SCHAD). The sample from the LCHAD patient was collected at autopsy and the patient with SCHAD deficiency was subsequently diagnosed as part of the prospective study and removed from the unknown etiology group. Acylcarnitine profiles were obtained for each specimen as butylated derivatives using tandem mass spectrometry.


RESULTS
The non-metabolic liver disease had no effect on the diagnostic value of bile acylcarnitine levels for detecting LCHAD deficiency. The concentrations of bile long-chain acylcarnitine species analyzed from patients with non-metabolic liver disease were far lower than the levels seen in LCHAD deficiency which also demonstrated a characteristic pattern of 3-hydroxyacylcarnitine excretion. In SCHAD deficiency, for which pathognomonic markers have not yet been established, bile analysis did not improve the diagnostic ability.


CONCLUSIONS
The analysis of bile acylcarnitines for the diagnosis of long-chain fatty acid oxidation defects will provide unbiased information even in the presence of severe non-metabolic liver disease.
Fuda
Franklin
F
Department of Pathology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX, and Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, PA 19104-4399, United States.
Narayan
Srinivas B
SB
Squires
Robert H
RH
Bennett
Michael J
MJ
D001646:Bile / Q000378:metabolism*; D001706:Biopsy; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007223:Infant; D008107:Liver Diseases / Q000175:diagnosis* / Q000378:metabolism*; D010084:Oxidation-Reduction
D005227:Fatty Acids; C116917:acylcarnitine; D002331:Carnitine