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A case of the Rett syndrome with acute encephalopathy induced during calcium hopantenate treatment.

We report a girl with the Rett syndrome who had acute encephalopathy probably induced by calcium hopantenate (HOPA). This 4-year-6-month-old girl had a history of moderate developmental delay and had received HOPA administration when first admitted at 2 years 6 months of age with hypoglycemia, hyperammonemia, lactic and pyruvic acidemia, and non-ketotic dicarboxylic aciduria. After this episode, she showed the rapid destructive stage of the Rett syndrome, i.e., severe psychomotor retardation with loss of speech, peculiar stereotypic hand movements, autistic behavior and seizures. Despite subsequent investigations, including analysis of urinary metabolites of organic and amino acids, measurement of serum carnitine and a muscle biopsy, we could not clarify the primary metabolic abnormalities in this girl.

Acute Disease↗

Detection of inborn errors of metabolism in unselected patients from pediatric intensive care units in Porto Alegre, Brazil: evaluation of screening techniques.

1. The present study provides an analysis of the interpretation and usefulness of mass biochemical urine screening tests currently applied to a population of severely ill children consisting of 232 unselected individuals, under various medications, held in intensive care units. 2. Testing for glycosaminoglycans by the cetyltrimethylammonium bromide reaction is of little benefit to this population. The Ehrlich reaction, used to detect porphobilinogen, should be reserved for cases which present clinical symptoms. Owing to the large number of false-positives and because chromatography or electrophoresis can easily be used to detect tyrosine, it is suggested that the nitrosonaphthol test be abandoned. The cyanide nitroprusside reaction should be used when chromatography or electrophoresis suggests cystinuria, homocystinuria or beta-mercapto lactate disulfiduria. 3. Because of its high sensitivity in detecting reducing substances, the Clinitest is useful for selecting samples to be investigated further by sugar chromatography. 4. Given the relatively high frequency of organic acidurias, particularly methylmalonic aciduria, in intensive care unit populations, it is suggested that the p-nitroaniline reaction be incorporated into the battery of chemical urine tests. 5. A comparison between paper chromatography and high voltage paper electrophoresis in terms of effective analysis of amino acid patterns demonstrated that chromatography is preferential, since this is as sensitive as electrophoresis, does not require a special apparatus and permits the simultaneous use of plasma and urine from the same patient, thus facilitating the interpretation of amino acid patterns.

Amino Acid Metabolism, Inborn Errors↗

Carnitine metabolism and human carnitine deficiency.

Carnitine in the human body is derived from the intake of preformed dietary carnitine and biosynthesized carnitine, stemming from the metabolism of lysine and methionine. Carnitine is synthesized in liver and kidney, stored in skeletal muscle, and excreted mainly in urine. Carnitine has two main functions, i.e., transporting long-chain fatty acids into the mitochondrial matrix for beta-oxidation to provide cellular energy and modulating the rise in intramitochondrial acyl-CoA/CoA ratio, which relieves the inhibition of many intramitochondrial enzymes involving glucose and amino acid catabolism. Thus, the main consequence of carnitine deficiency is impaired energy metabolism. Human carnitine deficiency can be either hereditary or acquired. Hereditary carnitine deficiency can be grouped into three clinical entities: myopathic carnitine deficiency, systemic carnitine deficiency, and organic acidurias. Acquired carnitine deficiency is due to inadequate intake, increased requirement, and increased loss of carnitine. The definite diagnosis of carnitine deficiency is based on the determination of free- and acylcarnitine levels in serum, urine, and/or tissues. The estimated safe and adequate daily carnitine intake for adults is 150-500 mumol/day whereas pharmacological doses of carnitine are required for the treatment of hereditary carnitine deficiency.

Animals↗

Orotic aciduria and increased nitrogen catabolism in rats.

In vitro incorporation of [14C] bicarbonate into orotic acid by rat liver slices was used to study the rate of orotic acid (OA) biosynthesis in the presence of physiological (0.73 mM) and saturation concentrations (5 mM) of NH4Cl. The influence of body size on OA synthesis in rats fed purified L-amino acid diets with (C) or without (-Arg) was examined. OA biosynthesis was significantly greater at both NH4Cl concentrations examined in liver slices obtained from -Arg rats for all sizes of rats. A linear decrease (r = 0.92) in OA synthesis as a function of body size was observed for rats fed either of the diets. The rate of OA biosynthesis was also found to increase linearly (r = 0.98) in livers from rats fed increasing dietary protein when determined by incubation with physiological concentrations of NH4Cl. OA biosynthesis was also found to increase with increase in length of fasting. Alteration in urinary OA and urea confirm these rates of synthesis. These results support the hypothesis that when the urea cycle is overtaxed, carbamyl phosphate (CP) synthesized intramitochondrially by CP synthetase I may be shunted into pyrimidine biosynthesis.

Aging↗

Hyperoxaluria in L-glyceric aciduria: possible nonenzymic mechanism.

Hydroxypyruvate inhibited the oxidation of [1-14C]glyoxylate to [14C] oxalate whether catalyzed by a purified preparation of glycolic acid oxidase from human liver, lactate dehydrogenase, a human liver extract, or a lobe of rat liver. It also brought about the nonenzymic decarboxylation of [1-14C]glyoxylate when it was present in the above assay systems. Radioactive isotope dilution and high-performance liquid chromatography analysis revealed the autooxidation of hydroxypyruvate to oxalate on standing in buffered solution at pH 7.4. In view of these observations, the current hypothesis of the role of lactate dehydrogenase in inducing hyperoxaluria in L-glyceric aciduria has been reexamined, and a possible nonenzymic mechanism by which oxalate may originate from hydroxypyruvate under such conditions has been proposed.

Amino Acid Metabolism, Inborn Errors↗

Clinical and molecular heterogeneity in very-long-chain acyl-coenzyme A dehydrogenase deficiency.

Very-long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency is an increasingly recognized defect of mitochondrial fatty acid beta-oxidation manifesting with episodes of metabolic decompensation or isolated recurrent myoglobinuria. In this report the clinical, biochemical, and molecular studies in a series of five patients (four Italian and one Spanish) with this disorder are discussed. Biochemical studies included the determination of fibroblast substrate oxidation rates and enzyme activity and Western blot analysis of VLCAD protein. Molecular analysis was performed by sequencing the VLCAD gene from the genomic DNA. Clinical features were within the spectrum previously reported. Four patients presented in infancy or childhood with episodes of severe metabolic decompensation and dicarboxylic aciduria. Two exhibited cardiomyopathy. The fifth patient presented with isolated recurrent rhabdomyolysis, with no cardiomyopathy or dicarboxylic aciduria. In all patients a significant loss of VLCAD activity associated with a marked reduction of VLCAD protein levels occurred. Molecular analysis disclosed one novel missense mutation (Cys437Tyr) and four previously reported mutations, including two missense substitutions (Phe418Leu and Arg419Trp), a single amino acid deletion (Lys258del), and one splice site mutation (IVS8-C(-2)), which was present in all four Italian patients. All patients exhibited compound heterozygosity. The phenotypic variability and the high genotypic heterogeneity of this hereditary metabolic disorder is reported.

Acyl-CoA Dehydrogenase↗

A comprehensive screening method for detecting organic acidurias and other metabolic diseases in acutely sick infants and children.

A protocol is described for the comprehensive screening of acutely ill neonates and infants for inherited metabolic diseases, with particular reference to the organic acidurias. A group of simple initial tests provide positive pointers to metabolic disorders, leading to comprehensive screening tests for the aminoacidopathies and organic acidurias. Specimen chromatograms of urinary organic acids in the normal neonate, infant, and child, obtained using the methods described, are given and compared with that from the urine of a child with previously unreported 2-hydroxyglutaric aciduria. The place of the scheme in the management of inherited metabolic disease in the perinatal period and its relationship to other screening programmes are discussed. It is estimated that use of the protocol would allow the detection of about one-half of the known inborn errors of metabolism, including the aminoacidopathies, the organic acidurias, the hyperammonaemias, and several disorders of carbohydrate metabolism, many of which present acutely in the neonate and infant.

Amino Acids↗

Rat malonyl-CoA decarboxylase; cloning, expression in E. coli and its biochemical characterization.

Malonyl-CoA decarboxylase (E.C.4.1.1.9) catalyzes the conversion of malonyl-CoA to acetyl-CoA. Although the metabolic role of this enzyme has not been fully defined, it has been reported that its deficiency is associated with mild mental retardation, seizures, hypotonia, cadiomyopathy, developmental delay, vomiting, hypoglycemia, metabolic acidosis, and malonic aciduria. Here, we isolated a cDNA clone for malonyl CoA decarboxylase from a rat brain cDNA library, expressed it in E. coli, and characterized its biochemical properties. The full-length cDNA contained a single open-reading frame that encoded 491 amino acid residues with a calculated molecular weight of 54, 762 Da. Its deduced amino acid sequence revealed a 65.6% identity to that from the goose uropigial gland. The sequence of the first 38 amino acids represents a putative mitochondrial targeting sequence, and the last 3 amino acid sequences (SKL) represent peroxisomal targeting ones. The expression of malonyl CoA decarboxylase was observed over a wide range of tissues as a single transcript of 2.0 kb in size. The recombinant protein that was expressed in E. coli was used to characterize the biochemical properties, which showed a typical Michaelis-Menten substrate saturation pattern. The Km and Vmax were calculated to be 68 microM and 42.6 micromol/min/mg, respectively.

Amino Acid Sequence↗

Bilateral arachnoid cysts of the temporal fossa in four children with glutaric aciduria type I.

Glutaric aciduria type I is an uncommon inborn error of metabolism. It is a serious disease, often with a fatal outcome. This study reports the presence of bilateral temporal fluid collections, probably bilateral arachnoid cysts, in association with glutaric aciduria type I. The CT and, when available, MR studies from five patients with this disorder were reviewed. Four of the patients had findings consistent with bilateral arachnoid cysts of the temporal fossa. This is a rare occurrence, with only 11 such cases reported in the literature. The observed association between temporal fluid collections and glutaric aciduria type I suggests that patients with bilateral arachnoid cysts should be investigated for this metabolic disorder.

Amino Acid Metabolism, Inborn Errors↗

Tandem mass neonatal screening in Taiwan--report from one center.

BACKGROUND/PURPOSE: Neonatal screening using tandem mass spectrometry (MS/MS) started in Taiwan in 2000. We evaluated the efficacy of this system by analyzing the frequency of diseases and the outcome of the patients identified. METHODS: Between August 2001 and July 2004, 199, 922 neonates were screened for 10 amino acids and acylcarnitines using MS/MS in a single center. RESULTS: In total, 29 cases of inborn errors of metabolism were detected. The overall prevalence was one per 6894 births. The most common inborn error found was 3-methylcrotonyl CoA carboxylase deficiency (10 cases, 34.5%), but none of the cases needed aggressive treatment. There were two cases of type I glutaric aciduria, two cases of maple syrup urine disease, and one case of type II citrullinemia, and early therapeutic intervention was effective for all of them. CONCLUSION: We found that MS/MS neonatal screening was valuable in the early diagnosis of severe and treatable inborn errors of metabolism such as organic acidemias and urea cycle disorders. It also detected less severe disorders that required only observation.

Amino Acids↗

A report of two families with sarcosinaemia in Hong Kong and revisiting the pathogenetic potential of hypersarcosinaemia.

INTRODUCTION: Sarcosinaemia is a rare metabolic disorder which has not been reported in Asia. CLINICAL PICTURE: The urine samples of 2 patients were screened as a routine metabolic screening offered for patients with mental retardation in our hospital. We used gas chromatography-mass spectrometry (GC-MS) which is capable of detecting abnormal pattern in amino acids and organic acids. Plasma sarcosine level was further quantified by GC-MS. The same methods were used in the investigations of asymptomatic family members. Urine examination by GC-MS revealed excessive amount of sarcosine in urine (normally undetectable) and their plasma sarcosine levels were raised. The 2 differential diagnoses of presence of sarcosine in urine--glutaric aciduria type II and folate deficiency--were ruled out by the absence of abnormal organic acids in the initial urine screen and by normal serum folate level respectively. Screening of the 2 families identified excessive sarcosine in urine in 2 siblings, one from each family. However, these 2 siblings of indexed patients thus identified have no neurological or developmental problem. CONCLUSION: Our finding was consistent with the notion that sarcosinaemia is a benign condition picked up coincidentally during screening for mental retardation.

Amino Acid Metabolism, Inborn Errors↗

Comparative frequency and severity of hypoglycemia in selected organic acidemias, branched chain amino acidemia, and disorders of fructose metabolism.

The Institution's experience with hypoglycemia in different types of organic acidemias, branched chain amino acidemia (MSUD), and disorders of fructose metabolism was reviewed retrospectively. The charts of 144 patients who were followed for 1-5 years were studied for the severity and frequency of hypoglycemia. The patients were mainly Saudi; however, 10-25% were from neighboring countries. Therefore, the observations pertain to the genetic groups in the Arabian peninsula. Organic acidemias which primarily manifest with neurologic signs, such as 4-hydroxybutyric aciduria, infantile onset 3-methylglutaconic aciduria, and glutaric aciduria type 1 never showed hypoglycemia. Patients with beta-ketothiolase deficiency, biotinidase deficiency, or intermittent or intermediate MSUD, also did not have hypoglycemia during metabolic crisis. Hypoglycemia was rare and mild among neonates with classic MSUD, ethylmalonic aciduria, and isovaleric acidemia. Less than 50% of the patients with MSUD older than 8 months, pyruvate carboxylase deficiency, methylmalonic acidemia, or propionic acidemia had hypoglycemia during metabolic crisis. On the other hand, patients with 3-hydroxy-3-methyl glutaryl-CoA lyase deficiency, holocarboxylase synthetase deficiency, medium or long-chain acyl-CoA dehydrogenase deficiency, neonatal onset 3-methylglutaconic aciduria, glutaric aciduria type 2, and disorders of fructose metabolism invariably had moderate-to-severe hypoglycemia associated with metabolic crisis. The purpose of this report is to provide the pediatrician, particularly in the Middle East, with a diagnostic guideline to the identification and management of different types of organic acidemias, based on co-existing hypoglycemia.

Acidosis↗

Glutaric aciduria type II: evidence for a defect related to the electron transfer flavoprotein or its dehydrogenase.

Incubation of intact fibroblasts from a patients with glutaric aciduria type II with [2-14C]riboflavin showed normal synthesis of flavin mononucleotide and flavin adenine dinucleotide. This is taken as evidence for normal transport of riboflavin into the cells and normal activity of riboflavin kinase (EC 2.7.1.26) and flavin mononucleotide adenylyltransferase (EC 2.7.7.2). The ability of intact fibroblasts to oxidize 1-14C-fatty acids and [6-14C]lysine is impaired in the patient which together with the urinary excretion pattern of organic acids indicates a defective dehydrogenation of fatty acid acyl-CoAs and glutaryl-CoA. However, dehydrogenation of (C6-C10) fatty acid acyl-CoA derivatives and glutaryl-CoA was normal when the dehydrogenases were measured in fibroblast homogenate with artificial electron acceptors. In vivo, these dehydrogenases transfer their electrons to CoQ10 in the main electron transport chain via electron transfer flavoprotein and electron transfer flavoprotein dehydrogenase. Glutaric aciduria type II fibroblasts showed very diminished activity when the glutaryl-CoA dehydrogenase activity was measured without artificial electron acceptor but with intact endogenous electron transport system. As the NADH and succinate oxidation seems normal in glutaric aciduria type II patients, this is strong evidence for a defect in either the electron transfer flavoprotein or the electron transfer flavoprotein dehydrogenase.

Amino Acid Metabolism, Inborn Errors↗

Simultaneous retention index analysis of urinary amino acids and carboxylic acids for graphic recognition of abnormal state.

Simultaneous profiling analysis of urinary amino acids (AAs) and carboxylic acids (CAs) was combined with retention index (I) analysis for graphic recognition of abnormal metabolic state. The temperature-programmed I values of the AA and CA standards measured as ethoxycarbonyl (EOC)/methoxime (MO)/tert-butyldimethylsilyl (TBDMS) derivatives were used as the reference I values. Urine samples were subjected to the sequential EOC, MO and TBDMS reactions for the analysis by gas chromatography (GC) and GC-mass spectrometry. The complex GC profiles were then transformed into their respective I patterns in bar graphic forms by plotting the normalized peak area ratios (%) of the identified AAs and CAs against their reference I values as the identification numbers. When the present method was applied to infant urine specimens from normal controls and patients with inherited metabolic diseases such as phenylketonuria, maple syrup urine disease, methylmalonic aciduria or isovaleric aciduria, each I pattern of bar graph more distinctly displayed quantitative abundances of urinary AAs and CAs in qualitative I scale, thus allowing graphic discrimination between normal and abnormal states.

Acetamides↗

Symptoms and signs in organic acidurias.

Organic acidaemias can present with a wide variety of signs and symptoms. A survey of the clinical presentation of the organic acidurias shows that single symptoms are not characteristic or diagnostic. Clinical awareness coupled with appropriate laboratory investigation is required for the correct diagnosis to be reached.

Acids↗

Determination of argininosuccinate lyase and arginase activities with an amino acid analyzer.

The measurement of argininosuccinate lyase (ASase) and arginase, both in liver and erythrocytes, was developed by using a commercial amino acid analyzer. The method is based upon the use of two different substrates, argininosuccinate and arginine for ASase and arginase, respectively, and the measurement of only one final metabolite: ornithine. The use of ornithine as a marker of biological activity of ASase is related to the fact that in the urea cycle, the specific activity of arginase is much higher than that of ASase; thus, during in vitro determinations, arginine, which is the product of ASase, is rapidly converted to ornithine. The sensitivity of the methods is very high since we were able to detect both activities using very diluted rat liver homogenates (0.10 mg protein/ml) or few microliters of human blood. In rat liver the Vmax for ASase and arginase were respectively 0.54 and 140 mumol/h/mg protein; the apparent Km values 1.25 and 13.5 mM. In human erythrocytes the Vmax for the same enzymes were 7.2 and 170 nmol/h/mg Hb and the apparent Km values were 0.66 and 9.5 mM. In 10 healthy volunteers the specific activity of ASase and arginase determined in blood were respectively 8.60 +/- 0.46 and 124.1 +/- 14.5 nmol/h/mg Hb. The results obtained from 2 patients suffering from argininosuccinic aciduria were also reported. In these latter cases while ASase was not detectable in blood, arginase activity was at the lowest end of the confidence limits determined in healthy volunteers.

Amino Acids↗

Molecular cloning of mevalonate kinase and regulation of its mRNA levels in rat liver.

Mevalonate kinase [ATP:(R)-mevalonate 5-phosphotransferase, EC 2.7.1.36] may be a regulatory site in the cholesterol biosynthetic pathway, and a mutation in the gene coding for this enzyme is thought to cause the genetic disease mevalonic aciduria. To characterize this enzyme, a rat liver cDNA library was screened with a monospecific antibody, and a 1.7-kilobase cDNA clone coding for mevalonate kinase was isolated. The complete DNA sequence was determined, and the longest open reading frame coded for a protein containing 395 amino acids with a deduced molecular weight of 41,990. Identification of the cDNA clone was confirmed by expression of enzyme activity in yeast and by protein sequence data obtained from sequencing purified rat mevalonate kinase. The deduced amino acid sequence of mevalonate kinase contained a motif for the ATP-binding site found in protein kinases, and it also showed sequence homology to the yeast RAR1 protein. The size of mevalonate kinase mRNA in rat liver was approximately 2 kilobases. Treatment with diets containing cholesterol-lowering agents caused an increase in both mevalonate kinase activity and mRNA levels, whereas diets containing 5% cholesterol lowered the levels of both enzyme activity and mRNA. These data indicate that long-term regulation of enzyme activity in rat liver is controlled by changes in the levels of mevalonate kinase mRNA.

Amino Acid Sequence↗