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PubMed1981

Studies on complementation in argininosuccinate synthetase and argininosuccinate lyase deficiencies in human fibroblasts.

Complementation tests after polyethylene glycol fusion have been performed between 10 citrullinemic strains with argininosuccinate synthetase deficiency and between five strains with argininosuccinate lyase deficiency. No complementation was observed between the citrullinemic strains, while two groups of complementation were defined with the argininosuccinate lyase deficients strains. Since the restoration of activity was not total, we assumed that complementation is probably intragenic.

Amino Acid Metabolism, Inborn Errors↗
PubMed1985

Differentiation of transient hyperammonemia of the newborn and urea cycle enzyme defects by clinical presentation.

We reviewed clinical data in 33 patients with transient hyperammonemia of the newborn (THAN): six previously unreported cases and 27 from the literature. Thirteen neonates with urea cycle enzyme deficiencies (UCED) served for comparison. No differences were found in the incidence of perinatal complications, route of delivery, Apgar scores, sex, or incidence or time of onset of seizures. On the other hand, neonates with THAN had significantly lower birth weights (mean +/- SEM 2282 +/- 78 gm vs 3336 +/- 222 gm, P less than 0.001) and gestational ages (35.1 +/- 0.5 weeks vs 39.6 +/- 0.5 weeks, P less than 0.001). Mean time of onset of respiratory distress (3.9 +/- 1.4 hours vs 71.5 +/- 26.1 hours, P less than 0.001), ventilatory support (P less than 0.001), lethargy (P less than 0.005), and coma (P less than 0.005) occurred earlier in THAN. Distinctive laboratory findings in patients with THAN included abnormal chest radiographic findings and plasma ammonium concentrations that were higher (1871 +/- 209 microM vs 973 +/- 169 microM, P less than 0.02) at an earlier age. Respiratory distress occurred in all but one patient with THAN before 24 hours; in contrast, only 62% of infants with UCED had respiratory symptoms, and none before 30 hours. In this retrospective study, the clinical presentation alone differentiated THAN from UCED.

Amino Acid Metabolism, Inborn Errors↗
PubMed1980

Plasma alpha-ketoglutarate in urea cycle enzymopathies and its role as a harbinger of hyperammonemic coma.

Metabolic observations during early stages of hyperammonemia in two infants with ornithine transcarbamylase deficiency suggest that plasma alpha-ketoglutarate concentration ([alpha-KG]) becomes subnormal before the development of hyperammonemic coma. In one case, plasma [NH4+] remained normal until 40 days of age when it rose to 58 microM. However, this hyperammonemia was preceded by a fall in plasma [alpha-KG] to 15 microM at 27 days of age. It was only after severe hyperammonemia was established at 50 days of age that coma supervened. In the second case, plasma [alpha-KG] became subnormal (14 microM) 8 days before the rise in plasma ammonium concentration [NH4+] (52 microM) and 14 days before the onset of hyperammonemic coma. In eight patients with urea cycle enzymopathies, there was a highly significant (P less than 0.01) negative linear correlation between [NH4+] and [alpha-KG]. In patients with portal-systemic encephalopathy, there was a similar relationship between [NH4+] and [alpha-KG], although the absolute [alpha-KG] levels in these patients were normal (23 +/- 4 microM) while the patients were hyperammonemic (88 +/- 25 microM).

Adolescent↗
PubMed2003

Tandem mass spectrometric analysis for disorders in amino, organic and fatty acid metabolism: two year experience in South Korea.

Seoul Clinical Laboratories began screening newborns and high risk group blood spots with tandem mass spectrometry (MS/MS) in April 2001. The goal was to determine approximate prevalence of metabolic disorders and optimization of decision criteria for estimation of preventive effect with early diagnosis. Approximately 44,300 neonates and children were screened and the estimated prevalence (newborn/high risk group), sensitivity, specificity and recall rate amounted to 1:2000 / 1:1250, 94.1 %, 99.7 %, and 0.04 %, respectively. Confirmed 35 multiple metabolic disorders (newborn/high risk) were as follows; 16 amino acid disorders [classical PKU(3/4), BH4 deficient-hyperphenylalaninemia(0/1), Citrullinemia(2/0), Homocystinuria(0/2), Hypermethioninemia(0/1), Tyrosinemia(1/0)], OTC deficiency (0/1), MSUD (2/0), 10 organic acidurias [Propionic aciduria(2/1), Methylmalonic aciduria(0/1), Isovaleric aciduria(2/1), 3-methylcrotonylglycineuria(1/0), Glutaric aciduria type 1(2/0)], 9 fatty acid oxidation disorders [LCHAD def. (2/2), Mitochondrial TFP def.(0/1), VLCAD def.(1/0), LC3KT def.(0/1), SCAD def (1/0), MADD def (0/1). The relatively normal development of 15 patients with metabolic disorders among newborns (except for the expired) demonstrates the usefulness of newborn screening by MS/MS for early diagnosis and medical intervention. However, close coordination between the MS/MS screening laboratory and the metabolic clinic/biochemical geneticists is needed to determine proper decision of screening parameters, confirmation diagnosis, follow-up scheme and additional tests.

Amino Acids↗
PubMed2003

A mouse model of argininosuccinic aciduria: biochemical characterization.

Argininosuccinate lyase (AL) has several roles in intermediary metabolism. It is an essential component of the urea cycle, providing a pathway for the disposal of excess nitrogen in mammals. AL links the urea cycle to the tricarboxylic acid (TCA) cycle by generating fumarate. Finally, AL is required for the endogenous production of arginine. In this latter role it may function outside ureagenic organs to provide arginine as a substrate for nitric oxide synthases (NOS). Increasing evidence suggests that argininosuccinate synthetase (AS) and AL are more globally expressed, and the coordinate regulation of AS and AL gene expression with that of the inducible form of NOS (iNOS) provides evidence that this may facilitate the regulation of NOS activity. Deficiency of AL leads to the human urea cycle disorder argininosuccinic aciduria. We produced an AL deficient mouse by gene targeting in order to investigate the role of AL in endogenous arginine production. This mouse also provides a model of the human disorder to explore the pathogenesis of the disorder and possible new treatments. Metabolic studies of these mice demonstrated that they have the same biochemical phenotype as humans, with hyperammonemia, elevated plasma argininosuccinic acid and low plasma arginine. Plasma nitrites, derived from NO, were not reduced in AL deficient mice and there was no significant difference is the level of cyclic GMP, the second messenger induced by NO.

Amino Acid Metabolism, Inborn Errors↗
PubMed1994

Pitfalls in aminoacid and organic acid analysis: 3-hydroxypropionic aciduria.

Pitfalls in organic acid analysis can originate from inadequate methodology, analytical interferences, in vivo interactions and from pre-analytical conditions which often are unknown to the specialized analytical laboratory. Among the latter, ingested food and additives, metabolites of food processing or medications have to be considered. Bacterial metabolites from the gastrointestinal or urogenital system or formed after sample collection can lead to pitfalls as well. An example of such a patient whose urinary metabolites mimic at first glance inherited propionic aciduria is described.

Amino Acid Metabolism, Inborn Errors↗
PubMed1998

Glutaric aciduria type I with high residual glutaryl-CoA dehydrogenase activity.

Two brothers with dystonia and slight MRI changes in the basal ganglia had normal urinary glutaric acid excretion, but slightly increased 3-hydroxyglutarate and conjugated glutarate excretions. Both siblings have high residual glutaryl-CoA dehydrogenase activity, and are compound heterozygotes for two mutations - R227P and V400M reported to be disease-causing in patients with glutaric aciduria type I.

Amino Acid Metabolism, Inborn Errors↗
PubMed2004

The role of methionine in ethylmalonic encephalopathy with petechiae.

BACKGROUND: Among patients with ethylmalonic aciduria, a subgroup with encephalopathy, petechial skin lesions, and often death in infancy is distinct from those with short-chain acyl-coenzyme A dehydrogenase deficiency or multiple acyl-coenzyme A dehydrogenase deficiency. The nature of the molecular defect in this subgroup is unknown, and the source of the ethylmalonic acid has been unclear. OBJECTIVE: To determine whether the administration of candidate amino acids increased the excretion of ethylmalonic acid. DESIGN: Examination of patterns of organic acids excreted in the urine before and following loading doses of isoleucine and methionine. SETTING: General clinical research center. PATIENT: An infant with ethylmalonic aciduria, global developmental delay, acrocyanosis, and intermittent showers of petechiae. MAIN OUTCOME MEASURE: Excretion of ethylmalonic acid in the urine. RESULTS: Loading with methionine increased the excretion of ethylmalonic acid, whereas loading with isoleucine did not. Restriction of the dietary intake of methionine decreased ethylmalonic acid excretion. CONCLUSION: In ethylmalonic acid encephalopathy with petechiae, methionine is a precursor of ethylmalonic acid.

Amino Acids↗
PubMed1993

Physiology and pathophysiology of organic acids in cerebrospinal fluid.

Concentrations of organic acids in cerebrospinal fluid (CSF) appear to be directly dependent upon their rate of production in the brain. There is evidence that the net release of short-chain monocarboxylic acids from the brain is a major route for removing these products of cerebral metabolism. Concentrations of organic acids in blood and CSF are largely independent of each other. Quantitative reference values for the concentrations of organic acids in CSF and plasma as well as ratios of individual organic acids between CSF and plasma were determined in 35 pairs of samples from paediatric patients. Over 25 organic acids were quantifiable in all or in the majority of CSF and/or plasma specimens (limit of detection 1 mumol/L). There were substantial differences in the CSF/plasma ratios between subgroups of organic acids. Metabolites related to fatty-acid oxidation were present in CSF in substantially less amounts than in plasma. Organic acids related to carbohydrate and energy metabolism and to amino acid degradation were present in CSF in the same amounts as or slightly smaller amounts than in plasma. Finally, some organic acids were found in substantially higher amounts in CSF than in plasma, e.g. glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate. Studies of organic acids in CSF and plasma samples are presented from patients with 'cerebral' lactic acidosis, disorders of propionate and methylmalonate metabolism, glutaryl-CoA dehydrogenase deficiency and L-2-hydroxy-glutaric aciduria. It became apparent that derangements of organic acids in the CSF may occur independently of the systemic metabolism. Quantitative organic acid analysis in CSF will yield new information on the pathophysiology in the central nervous system (CNS) of these disorders and may prove necessary for successful monitoring of treatment of organoacidopathies, which present mainly with neurological disease. For example, in glutaryl-CoA dehydrogenase deficiency the urinary excretion of glutarate appears to be an inadequate parameter for monitoring the effect of dietary therapy, without plasma and CSF determinations. In L-2-hydroxyglutaric aciduria the elevation of L-2-hydroxyglutarate was found to be greater in CSF than in plasma. In addition, some other organic acids, glycolate, glycerate, 2,4-dihydroxybutyrate, citrate and isocitrate, were also elevated in the CSF of the patients out of proportion to normal levels in plasma and urine. High concentrations of an unknown compound, which was tentatively identified as 2,4-dihydroxyglutarate, were found in the CSF of patients with L-2-hydroxyglutaric aciduria.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗
PubMed1976

Neonatal argininosuccinic aciduria with normal brain and kidney but absent liver argininosuccinate lyase activity.

An infant is described who died at 6 days of age with hyperammonemia and argininosuccinic acid in the urine. Argininosuccinic acid lyase (AL) was absent in liver, decreased in red blood cells, but normal in brain and kidney. The instability of AL in frozen stored tissues accounts for previous reports of deficient AL activity in the brain and kidney of neonates with this disease. The variation of AL activity in the tissues of this patient demonstrates that more than one gene locus either codes for the structure of this enzyme or regulates its biosynthesis in different organs.

Amino Acid Metabolism, Inborn Errors↗
PubMed1998

Analysis of organic acids, amino acids, and carnitine in dogs with lipid storage myopathy.

Abnormal accumulations of lipid droplets, localized predominantly in histochemical type 1 fibers, were observed in fresh frozen sections of muscle biopsies from 25 dogs with myalgia, weakness, and muscle atrophy. Compared to controls, lactic acidemia, hyperalaninemia, lactic and pyruvic aciduria, variably increased urinary excretion of carnitine esters, and muscle carnitine deficiency were present. These findings support a metabolic block in oxidative metabolism resulting in lactic acidemia in dogs with lipid storage myopathy.

Acids↗
PubMed2003

Newborn urine screening programme in the province of Quebec: an update of 30 years' experience.

The introduction of our voluntary mass screening programme in 1971, in the province of Quebec, has permitted us to detect different inborn errors of metabolism in the newborn population using a thin-layer chromatographic (TLC) technique with sequential use of different sprays on the same plate. Abnormalities in amino acids and organic acids are detected in urine filter paper specimens of 21-day-old babies. Initial parental compliance is 90% and climbs to 99.25% for repeat sample requests. Screening is centralized in one laboratory, while diagnosis, counselling, management and follow-up are done in four regional centres. Over 25 inherited Mendelian disorders can be identified. There have been certain modifications in our programme throughout the years in order to increase efficiency, screen for a larger number of disorders, improve the quality of the collection of the urine filter paper samples, increase parental compliance and better manage the data bank. However, one goal has remained a priority: early prevention of genetic diseases. We present an overall view of our screening programme with an add-on technique to detect different organic acidurias, our recent statistics and the modifications implemented over the years.

Amino Acid Metabolism, Inborn Errors↗