ABSTRACT
Tandem MS "profiling" of acylcarnitines and amino acids was conceived as a first-tier screening method, and its application to expanded newborn screening has been enormously successful. However, unlike amino acid screening (which uses amino acid analysis as its second-tier validation of screening results), acylcarnitine "profiling" also assumed the role of second-tier validation, due to the lack of a generally accepted second-tier acylcarnitine determination method. In this report, we present results from the application of our validated UHPLC-MS/MS second-tier method for the quantification of total carnitine, free carnitine, butyrobetaine, and acylcarnitines to patient samples with known diagnoses: malonic acidemia, short-chain acyl-CoA dehydrogenase deficiency (SCADD) or isobutyryl-CoA dehydrogenase deficiency (IBD), 3-methyl-crotonyl carboxylase deficiency (3-MCC) or ß-ketothiolase deficiency (BKT), and methylmalonic acidemia (MMA). We demonstrate the assay's ability to separate constitutional isomers and diastereomeric acylcarnitines and generate values with a high level of accuracy and precision. These capabilities are unavailable when using tandem MS "profiles". We also show examples of research interest, where separation of acylcarnitine species and accurate and precise acylcarnitine quantification is necessary.
Subject(s)
Acetyl-CoA C-Acyltransferase/deficiency , Acyl-CoA Dehydrogenase/deficiency , Amino Acid Metabolism, Inborn Errors/diagnosis , Carbon-Carbon Ligases/deficiency , Carnitine/analogs & derivatives , Lipid Metabolism, Inborn Errors/diagnosis , Urea Cycle Disorders, Inborn/diagnosis , Acetyl-CoA C-Acyltransferase/blood , Acetyl-CoA C-Acyltransferase/cerebrospinal fluid , Acetyl-CoA C-Acyltransferase/urine , Acyl-CoA Dehydrogenase/blood , Acyl-CoA Dehydrogenase/cerebrospinal fluid , Acyl-CoA Dehydrogenase/urine , Amino Acid Metabolism, Inborn Errors/blood , Amino Acid Metabolism, Inborn Errors/cerebrospinal fluid , Amino Acid Metabolism, Inborn Errors/urine , Betaine/analogs & derivatives , Betaine/blood , Betaine/cerebrospinal fluid , Betaine/urine , Carbon-Carbon Ligases/blood , Carbon-Carbon Ligases/cerebrospinal fluid , Carbon-Carbon Ligases/urine , Carnitine/blood , Carnitine/cerebrospinal fluid , Carnitine/urine , Chromatography, High Pressure Liquid/methods , Chromatography, High Pressure Liquid/standards , Female , Humans , Infant, Newborn , Isomerism , Lipid Metabolism, Inborn Errors/blood , Lipid Metabolism, Inborn Errors/cerebrospinal fluid , Lipid Metabolism, Inborn Errors/urine , Male , Neonatal Screening , Reproducibility of Results , Sensitivity and Specificity , Tandem Mass Spectrometry/standards , Urea Cycle Disorders, Inborn/blood , Urea Cycle Disorders, Inborn/cerebrospinal fluid , Urea Cycle Disorders, Inborn/urineABSTRACT
Chronic relapsing experimental allergic encephalomyelitis, an animal model of multiple sclerosis, was induced in Strain 13 guinea-pigs by subcutaneous injection of spinal cord homogenate and Freund's incomplete adjuvant supplemented with Mycobacterium tuberculosis. High resolution 1H NMR spectra of CNS tissue extracts indicated that the levels of choline metabolites, particularly betaine, were elevated in the spinal cord tissue, the principal site of lesion formation in this guinea-pig strain. The spectra also show that N-acetylated compounds are slightly depleted in the disease. The results are discussed in relation to the biochemical interpretation of NMR spectra obtained in vivo from patients with multiple sclerosis.
