Abstract
Free and total carnitine quantification is important as a complementary test for the diagnosis of unusual metabolic diseases, including fatty acid degradation disorders. The present study reports a new method for the quantification of free and total carnitine in dried plasma specimens by isotope dilution electrospray tandem mass spectrometry with sample derivatization. Carnitine is determined by looking for the precursor of ions of m/z = 103 of N-butylester derivative, and the method is validated by comparison with radioenzymatic assay. We obtained an inter- and intra-day assay coefficient of variation of 4.3 and 2.3, respectively. Free and total carnitine was analyzed in 309 dried plasma spot samples from children ranging in age from newborn to 14 years using the new method, which was found to be suitable for calculating reference age-related values for free and total carnitine (less than one month: 19.3 +/- 2.4 and 23.5 +/- 2.9; one to twelve months: 28.8 +/- 10.2 and 35.9 +/- 11.4; one to seven years: 30.7 +/- 10.3 and 38.1 +/- 11.9; seven to 14 years: 33.7 +/- 11.6, and 43.1 +/- 13.8 micro M, respectively). No difference was found between males and females. A significant difference was observed between neonates and the other age groups. We compare our data with reference values in the literature, most of them obtained by radioenzymatic assay. However, this method is laborious and time consuming. The electrospray tandem mass spectrometry method presented here is a reliable, rapid and automated procedure for carnitine quantitation.
Highlights
The number of inherited metabolic diseases is increasing as a result of many reports of cases related to alterations in several metabolic pathways, contributing to the advancement of research and technology developed in this field
The accuracy of free carnitine measurement was further evaluated by analysis of 95 stored plasma specimens and by comparing the values with those obtained by radioenzymatic assay
The main function of carnitine is to shuttle activated long-chain fatty acids (fatty acylcoenzyme A (CoA)) from the cytosol to the mitochondria matrix for ß-oxidation, and to remove from mitochondria short-chain, medium-chain and long-chain fatty acids that accumulate as a result of normal and abnormal metabolism, maintaining adequate cellular levels of free CoA
Summary
The number of inherited metabolic diseases is increasing as a result of many reports of cases related to alterations in several metabolic pathways, contributing to the advancement of research and technology developed in this field. The inborn errors of metabolism are usually caused by defective enzymes or cofactors and most are of autosomal recessive inheritance. This results in the accumulation of abnormal metabolites that might be detectable in biological fluids of affected patients. The differential diagnosis of metabolic disorders can be difficult even when more detailed biochemical analysis is performed. The main objective of such analysis is to identify the cause of the metabolic disturbance, which might be temporary or perma-. Pourfarzam nent, and eventually arrive at a possible diagnosis by further detailed testing, which includes specific enzyme assays or DNA testing
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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