The measurement of carnitine and acyl-carnitines: application to the investigation of patients with suspected inherited disorders of mitochondrial fatty acid oxidation.
We describe an improved radio-enzymatic method for the measurement of carnitine, short-chain acyl-carnitine and long-chain acyl-carnitine in plasma and tissue. An internal standard, hexadecanoyl-[CH3-3H]-carnitine was synthesised and used to improve the determination of long-chain acyl-carnitine. The between and within batch precisions were 10.4 and 7%, respectively. Control data for neonates, infants, children and adults in the fed and fasted state are documented. In addition we confirm the hypocarnitinaemia associated with pregnancy. Patients with medium-chain acyl-CoA dehydrogenase deficiency were studied during episodes of hypoglycaemia. In both fasted controls and patients there were high concentrations of short-chain acyl-carnitine, however in the latter group there were also low concentrations of free carnitine. We suggest that the monitoring of plasma carnitine and its derivatives is a useful adjunct to the investigation of children suspected to suffer from inherited disorders of mitochondrial beta-oxidation. We also describe a sample preparation procedure suitable for high performance liquid chromatographic analysis of specific acyl-carnitines from urine, plasma and tissue homogenates. The recoveries of acetyl-carnitine, octanoyl-carnitine and hexadecanoyl carnitine from urine were 101.5, 95 and 91% and from plasma 99.5, 91.5 and 85.5%, respectively. Acyl-carnitines (C2-C16) were analysed as their p-bromophenacyl derivatives by reverse-phase high performance liquid chromatography using a ternary gradient of acetonitrile/water/triethylamine phosphate. We report ten patients who excreted octanoyl-carnitine, hexanoyl-carnitine and in some cases a small amount of decanoyl-carnitine. In most of these cases suberylglycine and dicarboxylic acids were also detected by GC/MS. We had access to cultured fibroblasts from five of these patients and were able to demonstrate medium-chain acyl-CoA dehydrogenase deficiency by direct enzyme assay.
Bhuiyan
A K
AK
Human Metabolism Research Centre Department of Clinical Biochemistry, Medical School, University of Newcastle upon Tyne, UK.
Jackson
S
S
Turnbull
D M
DM
Aynsley-Green
A
A
Leonard
J V
JV
Bartlett
K
K
D000375:Aging / Q000097:blood; D002331:Carnitine / Q000032:analysis* / Q000097:blood / Q000652:urine; D002675:Child, Preschool; D005215:Fasting / Q000097:blood; D005227:Fatty Acids / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D030342:Genetic Diseases, Inborn / Q000378:metabolism*; D006801:Humans; D007223:Infant; D008928:Mitochondria / Q000378:metabolism*; D010084:Oxidation-Reduction; D010172:Palmitoylcarnitine / Q000302:isolation & purification; D010472:Perchlorates; D011869:Radioligand Assay; D015203:Reproducibility of Results; D012995:Solubility
D005227:Fatty Acids; D005230:Fatty Acids, Nonesterified; D010472:Perchlorates; D010172:Palmitoylcarnitine; D002331:Carnitine