Assays - Acylcarnitines
Long-term stability of amino acids and acylcarnitines in dried blood spots used for neonatal screening by tandem mass spectrometry
Author: K.A. Strnadová, M. Holub, A. Mühl, G. Heinze, R. Ratschmann, H.J. Mascher, S. Stöckler-Ipsiroglu, F. Waldhauser, F. Votava, J. Lebl, O.A. Bodamer
Publisher: Clin Chem 2007, 53, 717-722
Background: Dried blood filter cards, collected for newborn screening, are often stored for long periods of time. They may be suitable for the retrospective diagnosis of inborn errors of metabolism, but no data are currently available on the long-term stability of amino acids and acylcarnitine species.
Methods: We analysed amino acids and acylcarnitines by tandem mass spectrometry in 660 anonymous, randomly selected filter cards from 1989 through 2004. We assessed long-term stability of metabolites by linear regression and estimated annual decrease of concentration for each metabolite.
Results: Concentrations of free carnitine increased by 7.6 % per year during the first 5 years of storage and decreased by 1.4 % per year thereafter. Alanine, arginine, leucine, methionine, and phenylalanine decreased by 6.5 %, 3.3 %, 3.1 %, 7.3 %, and 5.7 % per year, respectively. Acetylcarnitine, propionylcarnitine, citrulline, gylcine, and ornithine decreased by 18.5 %, 27.4 %, 8.1 %, 14.7 %, and 16.3 % per year during the first 5 years, respectively; thereafter the decline was more gradual. Tyrosine decreased by 1.7 % per year during the first 5 years and 7.9 % per year thereafter. We could not analyze medium- and long-chain acylcarnitine species because of low physiological concentrations.
Conclusion: Estimation of the annual decrease of metabolites may allow for the retrospective diagnosis of inborn errors of metabolism in filter cards that have been stored for long periods of time.
Endurance exercise training and L-carnitine supplementation stimulates gene expression in the blood- und muscle cells in young athletes and middle aged subjects
Author: A. Lohninger, A. Sendic, E. Litzlbauer, R. Hofbauer, H. Staniek, D. Blesky, C. Schwieglhofer, M. Eder, H. Bergmüller, H.J. Mascher, D.G. Mascher
Publisher: Chemical Monthly 2005, 136, 1425-1442
Endurance exercise training is known to increase fatty acid (FA) oxidation during exercise and to stimulate mRNA synthesis of mitochondrial carnitine acyltransferases in skeletal muscle. To test the hypothesis that long-term endurance training induces cellular adaptions in different tissues, we determined the relative mRNA abundances of these genes in skeletal muscle and in blood cells from young athletes and middle aged untrained persons.
The first trial examined 6 cross-country skiers, at the start of high volume/low intensity exercise training and 6 months later, when training at the same exercise intensity had elicited a significantly slower rate of lactate accumulation.
In the second trial of 24 middle aged untrained (12 placebo and 12 carnitine supplemented) probands the mRNA expression was determined at the beginning and after three months of a low intensity endurance training program. A 5-fold increase of the muscle form of carnitine palmitoyltransferase 1 (CPT1B), a 4-fold increase in carnitine acetyltransferase (CRAT), and a 6-fold increase in the mRNA content of the main carnitine carrier OCTN2 in the muscles of the athletes were determined by reverse transcription quantitative real time polymerase chain reaction (RTPCR). The corresponding values examined in white blood cells were 12 (CPT1B), 4-(CTP1A), and 5-fold (OCTN2). In WBC of middle aged untrained subjects, the mRNA content of the liver form of the carnitine palmitoyferase 1 (CPT1A) was stimulated 2-fold (placebo group) and 8-fold in the carnitine supplemented probands. The relative abundances of CPT1B mRNA were increased by a factor of 3 (placebo) and 5 (carnitine supplemented), respectively. The mRNA abundances of OCTN2 increased 5-fold (placebo) and 7-fold (carnitine supplemented).
While the plasma carnitine levels also remained low during the study period in athletes, normal levels were determined in untrained subjects and significantly increased levels were found after carnitine supplementation. A marked increase of acylcarnitine excretion resulting in a reduction of the portion of short-chain acylcarnitines, other than acylcarnitine, due to carnitine supplementation could be interpreted as a detoxifying function.
The results of the present study may offer the opportunity to use the blood cells as a target for differential gene expressions and as an indicator for responses of skeletal muscle to exercise and / or nutrient supplementation.