A Novel Tandem Mass Spectrometry Method for Rapid Confirmation of Medium- and Very Long-Chain acyl-CoA Dehydrogenase Deficiency in Newborns

BACKGROUND:Newborn screening for medium- and very long-chain acyl-CoA dehydrogenase (MCAD and VLCAD, respectively) deficiency, using acylcarnitine profiling with tandem mass spectrometry, has increased the number of patients with fatty acid oxidation disorders due to the identification of additional milder, and so far silent, phenotypes. However, especially for VLCADD, the acylcarnitine profile can not constitute the sole parameter in order to reliably confirm disease. Therefore, we developed a new liquid chromatography tandem mass spectrometry (LC-MS/MS) method to rapidly determine both MCAD- and/or VLCAD-activity in human lymphocytes in order to confirm diagnosis. METHODOLOGY:LC-MS/MS was used to measure MCAD- or VLCAD-catalyzed production of enoyl-CoA and hydroxyacyl-CoA, in human lymphocytes. PRINCIPAL FINDINGS:VLCAD activity in controls was 6.95+/-0.42 mU/mg (range 1.95 to 11.91 mU/mg). Residual VLCAD activity of 4 patients with confirmed VLCAD-deficiency was between 0.3 and 1.1%. Heterozygous ACADVL mutation carriers showed residual VLCAD activities of 23.7 to 54.2%. MCAD activity in controls was 2.38+/-0.18 mU/mg. In total, 28 patients with suspected MCAD-deficiency were assayed. Nearly all patients with residual MCAD activities below 2.5% were homozygous 985A>G carriers. MCAD-deficient patients with one other than the 985A>G mutation had higher MCAD residual activities, ranging from 5.7 to 13.9%. All patients with the 199T>C mutation had residual activities above 10%. CONCLUSIONS:Our newly developed LC-MS/MS method is able to provide ample sensitivity to correctly and rapidly determine MCAD and VLCAD residual activity in human lymphocytes. Importantly, based on measured MCAD residual activities in correlation with genotype, new insights were obtained on the expected clinical phenotype

Increased plasma carnitine concentrations in preeclampsia

OBJECTIVE: Preeclampsia is associated with abnormal lipid metabolism, including fatty acid metabolism. Carnitine plays an indispensable role in the oxidation of fatty acids. The aim of the study was to evaluate the possible role of abnormal fatty add oxidation in preeclampsia by comparing plasma carnitine levels between preeclamptic and healthy control pregnant women.METHODS: Plasma concentrations of free carnitine and short-, medium-, and long-chain acylcarnitines were investigated with electrospray tandem mass spectrometry in pregnant women with preeclampsia (n = 33) and in normotensive healthy pregnant control subjects (n = 28). Excluded were multiple pregnancies and women with preexistent hypertension, diabetes, renal dysfunction, immune disease, and intrauterine fetal death. Control subjects were healthy pregnant women without hypertension or proteinuria.RESULTS: The results revealed that, except for the medium-chain plasma acylcarnitines, all plasma carnitines were significantly increased (P &lt;.001) in the preeclamptic group (t test for impaired samples). Free carnitine and the short- and long-chain acylcarnitine values were increased by approximately 50% compared with the control group. Total and short-chain plasma acylcarnitine levels were significantly correlated to diastolic blood pressure, whereas no relationship could be demonstrated between carnitine concentrations and the variables proteinuria and systolic blood pressure.CONCLUSION: The considerable increased plasma carnitine concentrations, together with the accumulation of lipids, support the role of abnormal lipid metabolism in the pathophysiology of preeclampsia. It is suggested that toxic metabolites resulting from abnormal fatty acid oxidation in the placenta contribute to the endothelial dysfunction of preeclampsia. ( (C) 2004 by The American College of Obstetricians and Gynecologists.).</p