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PubMed2004

Pathophysiology, diagnosis, and treatment of methylmalonic aciduria-recent advances and new challenges.

Classical methylmalonic aciduria is a relatively rare inborn error of branched-chain amino acid metabolism, occurring in 1:50,000 to 1:80,000 newborns. Three decades after its recognition, major progress has been made in survival and prevention of neurological sequelae in affected children, if the diagnosis is made early and treatment and follow-up care are meticulous. Therapy consists of a specially formulated protein diet, carnitine supplementation, and vigorous emergency treatment during intercurrent illnesses aimed at preventing the development of catabolism. Recently the clinician has been challenged by partially unexpected long-term complications. These include chronic neurological symptoms, specifically an extrapyramidal movement disorder caused by progressive destruction of the basal ganglia, which are similar to those observed in other organic acid disorders, such as propionic aciduria or glutaric aciduria type I. Unexpected and unique is the development of chronic renal failure in a major subset of patients. As the pathophysiological basis of renal failure is still obscure, no causative treatment is available and hemodialysis may become necessary. Experience with transplantation of liver, kidney, or kidney and liver is very limited and allows as yet no conclusions. Interdisciplinary research efforts in this field should reveal new pathophysiological links and hopefully provide additional therapeutic approaches.

Amino Acid Metabolism, Inborn Errors↗
PubMed1993

Cutaneous findings of nutritional deficiencies in children.

Nutritional deficiencies may be associated with a variety of cutaneous findings in children. This review emphasizes new developments relating to cutaneous findings of nutritional deficiencies. Zinc deficiency, acrodermatitis enteropathica, and acrodermatitis enteropathica-like eruptions are seen with a variety of conditions including cystic fibrosis, anorexia nervosa, and breastfeeding. Similar cutaneous findings not related to zinc deficiency may also occur with such metabolic disorders as methylmalonic aciduria, multiple carboxylase deficiency, essential fatty acid deficiency and other amino acid deficiencies. Vitamin K deficiency is associated with hemorrhagic disease of the newborn and coagulopathy. Vitamin A deficiency presents with a variety of systemic findings and distinctive dermatologic findings. Acute vitamin A deficiency may be seen in children infected with measles and is associated with more severe disease. The systemic and cutaneous findings of vitamin C deficiency, scurvy, are discussed.

Ascorbic Acid Deficiency↗
PubMed1997

Intragenic complementation at the human argininosuccinate lyase locus. Identification of the major complementing alleles.

To determine the molecular and biochemical basis of intragenic complementation observed at the human argininosuccinate lyase (ASL) locus, we identified the ASL alleles in ASL-deficient cell strains with two unique complementation phenotypes: (i) frequent complementers, strains that participated in the majority of complementation events, and (ii) high activity complementers, strains in which complementation was associated with a relatively high level of restoration of ASL activity. Four mutations (Q286R, D87G, A398D, and a deletion of exon 13) were identified in the four strains examined. One of the two frequent complementers was homozygous, and the other heterozygous, for the Q286R allele. Similarly, one of the two high activity complementers was homozygous, and the other heterozygous, for the D87G allele. When the Q286R and D87G mutations were introduced by site-directed mutagenesis into wild-type ASL cDNA, each conferred loss of ASL activity in COS cell transfection assays. To test directly the hypothesis that intragenic complementation occurs at the ASL locus, one of the major complementation events observed previously, between strains carrying the Q286R and D87G alleles, was reconstructed in COS cell transfection assays. A partial restoration of ASL activity, comparable with the increase seen in the fibroblast complementation analysis, was observed on joint cotransfection of these two alleles. The results provide molecular confirmation of the major features of the ASL mutant complementation map, identify the Q286R and D87D alleles as the frequent and high activity complementing alleles, respectively, and provide direct proof of intragenic complementation at the ASL locus.

Alleles↗
PubMed1989

Altered acyl-CoA metabolism in riboflavin deficiency.

We have recently described the effects of riboflavin deficiency on the metabolism of dicarboxylic acids (Draye et al. (1988) Eur. J. Biochem. 178, 183-189). As both mitochondria and peroxisomes are thought to be involved, we have examined the activities of various enzymes in these organelles in the livers of riboflavin-deficient rats. Mitochondrial beta-oxidation of fatty acids was severely depressed due to loss of activity of the three fatty acyl-CoA dehydrogenases, whereas there was an enhancement of peroxisomal beta-oxidation due to an increased activity of the FAD-dependent fatty acyl-CoA oxidase, although the activities of other peroxisomal flavoproteins, D-amino acid oxidase and glycolate oxidase, were lowered. Hepatocyte morphometry revealed an increase in the numbers of peroxisomes, indicating a proliferation induced by the deficiency. The mitochondrial acyl-CoA dehydrogenases involved in branched-chain amino acid metabolism were also severely decreased leading to characteristic organic acidurias. There was some loss of activity of the flavin-dependent sections of the electron transport chain (complexes I and II), but these were probably not sufficient to affect normal function in vivo. The specificity of these effects allows the use of the riboflavin-deficient rat as a model for the study of dicarboxylate metabolism.

Acyl Coenzyme A↗
PubMed1996

Erythroblastopenia associated with methylmalonic aciduria. Case report and in vitro studies.

Various cytopenias, including neutropenia, thrombocytopenia and pancytopenia, have been reported in association with inborn errors of branched amino acid metabolism. We report here on a case of anemia associated with erythroblastopenia-that is less frequent in this context-in a neonate with methylmalonic aciduria. We used a semisolid erythroid culture system to investigate the effect on in vitro erythropoiesis of organic acids found in excess in this patient: methylmalonic (MMA) and propionic (PA) acids. First, the addition of 10% serum of the patient to a normal bone marrow progenitor culture suppressed the erythrocyte colony-forming unit growth in comparison to a pool of normal serum, while the addition of a 1:1 mixture of normal and patient serum resulted in an intermediate inhibition. MMA, when added to culture medium, resulted in a moderate inhibition of erythropoiesis only at a higher concentration than observed in our patient or reported in other cases. Conversely, PA showed an inhibitory effect at a concentration commonly observed in methylmalonic aciduria. The same effect was observed when the cells were in the presence of PA only for 72 h and then secondly plated in semisolid culture. Neither MMA nor PA showed any effect on the cell number and viability after a 3-, 4- or 7-day incubation except at the highest concentration tested.

Amino Acid Metabolism, Inborn Errors↗
PubMed1997

Structural organization of the human short-chain acyl-CoA dehydrogenase gene.

Short-chain acyl-CoA dehydrogenase (SCAD) is a homotetrameric mitochondrial flavoenzyme that catalyzes the initial reaction in short-chain fatty acid beta-oxidation. Defects in the SCAD enzyme are associated with failure to thrive, often with neuromuscular dysfunction and elevated urinary excretion of ethylmalonic acid (EMA). To define the genetic basis of SCAD deficiency and ethylmalonic aciduria in patients, we have determined the sequence of the complete coding portion of the human SCAD gene (ACADS) and all of the intron-exon boundaries. The SCAD gene is approximately 13 kb in length and consists of 10 exons. Four polymorphic sites have previously been detected by sequencing of cDNA from fibroblasts of patients excreting elevated amounts of EMA. Three of these polymorphisms (321T/C, 990C/T, 1260G/C) are silent variants, while a 625G/A polymorphism results in an amino acid replacement and has been shown to be associated with ethylmalonic aciduria. From analysis of 18 unrelated Danish families, we show that the four SCAD gene polymorphisms constitute five allelic variants of the SCAD gene, and that the 625A variant together with the less frequent variant form of the three other polymorphisms (321C, 990T, 1260C) constitutes an allelic variant with a frequency of 22% in the general Danish population. Using fluorescence in-situ hybridization, we confirm the localization of the human SCAD gene to the distal part of Chromosome (Chr) 12 and suggest that the SCAD gene is a single-copy gene. The evolutionary relationship between SCAD and five other members of the acyl-CoA dehydrogenase family was investigated by two independent approaches that gave similar phylogenetic trees.

Acyl-CoA Dehydrogenase↗
PubMed2003

Plasma urea-cycle-related amino acids, ammonium levels, and urinary orotic acid excretion in short-bowel patients managed with an oral diet.

BACKGROUND AND AIMS: The small intestine contains several enzymes involved in arginine synthesis and converts glutamine to citrulline, the major compound for endogenous arginine synthesis. This study was conducted to assess the plasma status of urea-cycle intermediates and orotic urinary excretion in short-bowel patients. METHODS: Thirteen stable short-bowel syndrome patients (7 men; 60.2+/-15.2 years) were studied. Patients were divided into moderately resected (Group A; n=6) and severely resected (Group B; n=7) according to their remnant bowel length (Group A: 61-150 cm; Group B: < or =60 cm). All subjects were consuming an oral diet plus dietetic supplements. Plasma urea-cycle amino acids, ammonium and urinary orotic acid were determined. RESULTS: Plasma glutamine levels were significantly higher in both patient groups than in the control group (P<0.001). Regarding citrulline, Group B levels were significantly lower vs. controls (P<0.001). Comparisons between patient groups showed higher arginine in Group A (P<0.05) and non-statistically lower citrulline in Group B. Blood ammonium and orotic urinary excretion were normal. CONCLUSIONS: Although plasma citrulline and glutamine alterations were found, patients showed no hyperammonemia or orotic aciduria, which suggests a certain degree of adaptation in arginine and related amino acid metabolism, when an adequate dietary supply of arginine is provided.

Adult↗
PubMed1975

Determination of urinary carbamylaspartate and dihydro-orotate in normal subjects and in patients with hereditary orotic aciduria.

An isotope dilution assay for urinary dihydro-orotic acid and carbamylaspartic acid (CAA) has been developed which has been shown to yield accurate measurements for these pyrimidine precurosrs. Dihydro-orotic acid could not be detected in 24-hour urine specimens from 10 normal adults and 7 normal children, or in specimens from 2 children with hereditary orotic aciduria Type I. Small amounts (approximately 10 mumole per 24 hours) of carbamylaspartic acid are excreted in normal urine, and there was a modest elevation in CAA excretion in the 2 patients with hereditary orotic aciduria.

Adult↗
PubMed2002

Glutaric aciduria type III: a distinctive non-disease?

Glutaric aciduria type III is a rare metabolic abnormality leading to persistent isolated glutaric acid excretion. We report the clinical and biochemical phenotypes of three affected children. The first patient is a boy with dysmorphic features and a chromosomal deletion (monosomy 6q26-qter) in whom a persistent glutaric aciduria (500 mmol/mol creatinine, normal <10) was detected during a routine metabolic investigation. The second boy suffered from acute gastroenteritis and hyperthyroidism, when an excessively high urinary glutaric acid excretion was identified (1460 mmol/mol creatinine). The third patient is a girl with constantly elevated glutaric acid in her urine (290 mmol/mol creatinine) but no symptoms of significant disease. In all our patients, glutaric aciduria type I (glutaryl-CoA dehydrogenase deficiency), glutaric aciduria type II (multiple acyl-CoA dehydrogenation defect), and secondary forms of glutaric aciduria (for example due to intestinal infections or mitochondrial dysfunction) could be excluded. Loading with the precursor amino acid lysine in all patients as well as with pipecolic acid in the third case led to an increase in urinary glutaric acid excretion, proving the endogenous origin of glutarate. Glutaric aciduria type III (a defect reported to be caused by peroxisomal glutaryl-CoA oxidase deficiency) is our presumptive diagnosis. However, peroxisomal glutaryl-CoA oxidase is not well characterized and no reliable approach for the direct determination of this enzyme is available to us. To our knowledge, in the English language literature only a single patient with glutaric aciduria type III has been described. Our cases reported here confirm the earlier assumption that glutaric aciduria type III is not related to a distinctive phenotype. Glutaric aciduria type III appears to be a rare metabolic abnormality, presumably of peroxisomal metabolism. However, its pathophysiological impact still needs further investigation.

Amino Acid Metabolism, Inborn Errors↗