Deficiency of perforin and hCNT1, a novel inborn error of pyrimidine metabolism, associated with a rapidly developing lethal phenotype due to multi-organ failure.

Pyrimidine nucleotides are essential for a vast number of cellular processes and dysregulation of pyrimidine metabolism has been associated with a variety of clinical abnormalities. Inborn errors of pyrimidine metabolism affecting enzymes in the pyrimidine de novo and degradation pathway have been identified but no patients have been described with a deficiency in proteins affecting the cellular import of ribonucleosides. In this manuscript, we report the elucidation of the genetic basis of the observed uridine-cytidineuria in a patient presenting with fever, hepatosplenomegaly, persistent lactate acidosis, severely disturbed liver enzymes and ultimately multi-organ failure.

A sensitive mass spectrometry platform identifies metabolic changes of life history traits in C. elegans.

Abnormal nutrient metabolism is a hallmark of aging, and the underlying genetic and nutritional framework is rapidly being uncovered, particularly using C. elegans as a model. However, the direct metabolic consequences of perturbations in life history of C.

A novel UPLC-MS/MS based method to determine the activity of N-acetylglutamate synthase in liver tissue.

Background: N-acetylglutamate synthase (NAGS) plays a key role in the removal of ammonia via the urea cycle by catalyzing the synthesis of N-acetylglutamate (NAG), the obligatory cofactor in the carbamyl phosphate synthetase 1 reaction. Enzymatic analysis of NAGS in liver homogenates has remained insensitive and inaccurate, which prompted the development of a novel method.

Methods: UPLC-MS/MS was used in conjunction with stable isotope (N-acetylglutamic-2,3,3,4,4-d acid) dilution for the quantitative detection of NAG produced by the NAGS enzyme.

Cerebrospinal fluid in tuberculous meningitis exhibits only the L-enantiomer of lactic acid.

Background: The defining feature of the cerebrospinal fluid (CSF) collected from infants and children with tuberculous meningitis (TBM), derived from an earlier untargeted nuclear magnetic resonance (NMR) metabolomics study, was highly elevated lactic acid. Undetermined was the contribution from host response (L-lactic acid) or of microbial origin (D-lactic acid), which was set out to be determined in this study.

Methods: In this follow-up study, we used targeted ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) to determine the ratio of the L and D enantiomers of lactic acid in these CSF samples.

Mitochondrial protein acetylation is driven by acetyl-CoA from fatty acid oxidation.

Mitochondria integrate metabolic networks for maintaining bioenergetic requirements. Deregulation of mitochondrial metabolic networks can lead to mitochondrial dysfunction, which is a common hallmark of many diseases. Reversible post-translational protein acetylation modifications are emerging as critical regulators of mitochondrial function and form a direct link between metabolism and protein function, via the metabolic intermediate acetyl-CoA.

Inhibition of the isoprenoid biosynthesis pathway; detection of intermediates by UPLC-MS/MS.

The isoprenoid biosynthesis pathway provides the cell with a variety of compounds which are involved in multiple cellular processes. Inhibition of this pathway with statins and bisphosphonates is widely applied in the treatment of hypercholesterolemia and metabolic bone disease, respectively. In addition, since isoprenylation of proteins is an important therapeutic target in cancer research there is interest in interfering with isoprenoid biosynthesis, for which new inhibitors to block farnesylation and geranylgeranylation of small GTPases are being developed.

New insights on the mechanisms of valproate-induced hyperammonemia: inhibition of hepatic N-acetylglutamate synthase activity by valproyl-CoA.

Background & Aims: Hyperammonemia is a frequent side-effect of valproic acid (VPA) therapy, which points to an imbalance between ammoniagenesis and ammonia disposal via the urea cycle. The impairment of this liver-specific metabolic pathway induced either by primary genetic defects or by secondary causes, namely associated with drugs administration, may result in accumulation of ammonia. To elucidate the mechanisms which underlie VPA-induced hyperammonemia, the aim of this study was to evaluate the effect of both VPA and its reactive intermediate, valproyl-CoA (VP-CoA), on the synthesis of N-acetylglutamate (NAG), a prime metabolite activator of the urea cycle.

The role of ELOVL1 in very long-chain fatty acid homeostasis and X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (X-ALD) is caused by mutations in the ABCD1 gene encoding the peroxisomal ABC transporter adrenoleukodystrophy protein (ALDP). X-ALD is characterized by the accumulation of very long-chain fatty acids (VLCFA; > or =C24) in plasma and tissues. In this manuscript we provide insight into the pathway underlying the elevated levels of C26:0 in X-ALD.

Molecular characterization of iodotyrosine dehalogenase deficiency in patients with hypothyroidism.

Context: The recent cloning of the human iodotyrosine deiodinase (IYD) gene enables the investigation of iodotyrosine dehalogenase deficiency, a form a primary hypothyroidism resulting from iodine wasting, at the molecular level.

Objective: In the current study, we identify the genetic basis of dehalogenase deficiency in a consanguineous family.

Results: Using HPLC tandem mass spectrometry, we developed a rapid, selective, and sensitive assay to detect 3-monoiodo-l-tyrosine and 3,5-diodo-l-tyrosine in urine and cell culture medium.

The human peroxisomal ABC half transporter ALDP functions as a homodimer and accepts acyl-CoA esters.

Peroxisomes play a major role in human cellular lipid metabolism, including the beta-oxidation of fatty acids. The most frequent peroxisomal disorder is X-linked adrenoleukodystrophy (X-ALD), which is caused by mutations in the ABCD1 gene. The protein involved, called ABCD1, or alternatively ALDP, is a member of the ATP-binding-cassette (ABC) transporter family and is located in the peroxisomal membrane.

Aromatic l-aminoacid decarboxylase deficiency: unusual neonatal presentation and additional findings in organic acid analysis.

Aromatic l-aminoacid decarboxylase (AADC) deficiency is a neurotransmitter defect leading to a combined deficiency of catecholamines and serotonin. Patients are usually detected in infancy due to developmental delay, hypotonia, and extrapyramidal movements. Diagnosis is based on an abnormal neurotransmitter metabolite profile in CSF and reduced AADC activity in plasma.

beta-Ureidopropionase deficiency: an inborn error of pyrimidine degradation associated with neurological abnormalities.

beta-Ureidopropionase deficiency is an inborn error of the pyrimidine degradation pathway, affecting the cleavage of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid. In this study, we report the elucidation of the genetic basis underlying a beta-ureidopropionase deficiency in four patients presenting with neurological abnormalities and strongly elevated levels of N-carbamyl-beta-alanine and N-carbamyl-beta-aminoisobutyric acid in plasma, cerebrospinal fluid and urine. No beta-ureidopropionase activity could be detected in a liver biopsy obtained from one of the patients, which reflected the complete absence of the beta-ureidopropionase protein.