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Neuropediatrics Apr 2015Hereditary orotic aciduria is a rare metabolic disease that results from a defect of uridine-5-monophosphate synthase (UMPS). In affected patients, main clinical...
Hereditary orotic aciduria is a rare metabolic disease that results from a defect of uridine-5-monophosphate synthase (UMPS). In affected patients, main clinical symptoms are a markedly increased urinary excretion of orotic acid combined with megaloblastic anemia. This report describes a new case of UMPS deficiency without megaloblastic anemia but with epilepsy.
Topics: Anemia, Megaloblastic; Child, Preschool; Epilepsy; Humans; Male; Metabolic Diseases; Multienzyme Complexes; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase
PubMed: 25757096
DOI: 10.1055/s-0035-1547341 -
Analytical Biochemistry Dec 2018Excess urinary orotic acid excretion occurs in patients with some inborn errors of metabolic pathways such as pyrimidine synthesis and urea cycle. Thus, rapid diagnosis...
Excess urinary orotic acid excretion occurs in patients with some inborn errors of metabolic pathways such as pyrimidine synthesis and urea cycle. Thus, rapid diagnosis of orotic aciduria has a vital importance for patients. In this paper, a novel method for determination of orotic acid in urine samples by ion chromatography with suppressed conductivity detection was investigated. The separation of orotic acid from urine matrix was accomplished by using an anion exchange column with optimized isocratic eluent program which utilized 50 mM NaOH. The other chromatographic conditions were as follows: the suppressor current was 31 mA; the flow rate of mobile phase was 0.25 mL min; the column temperature was 30 °C; sample loop volume was 10 μL. Under optimized conditions, the limit of detection was 0.2 μmol L‾. Dramatically elevated orotic acid concentration was observed on pathological urine samples comparing to healthy urines, as expected. There are a good many advantages of the proposed method, but using an environmentally friendly reagent free system, no organic solvent employment and its quick nature, and being a sensitive and reliable method are the most obvious ones. The proposed method, therefore, may be utilized as an alternative technique for clinical laboratories.
Topics: Chromatography; Humans; Orotic Acid; Reproducibility of Results; Solvents; Temperature
PubMed: 30267708
DOI: 10.1016/j.ab.2018.09.016 -
Clinica Chimica Acta; International... Sep 2014Orotic aciduria in the presence of hyperammonemia is a key indicator for a defect in the urea cycle, specifically ornithine transcarbamylase (OTC) deficiency. Current...
BACKGROUND
Orotic aciduria in the presence of hyperammonemia is a key indicator for a defect in the urea cycle, specifically ornithine transcarbamylase (OTC) deficiency. Current newborn screening (NBS) protocols can detect several defects of the urea cycle, but screening for OTC deficiency remains a challenge due to the lack of a suitable assay. The purpose of this study was to develop a high-throughput assay to measure orotic acid in dried blood spot (DBS) specimens as an indicator for urea cycle dysfunction, which can be readily incorporated into routine NBS.
METHODS
Orotic acid was extracted from DBS punches and analyzed using flow-injection analysis tandem mass spectrometry (FIA-MS/MS) with negative-mode ionization, requiring <2 min/sample run time. This method was then multiplexed into a conventional newborn screening assay for analysis of amino acids, acylcarnitines, and orotic acid.
RESULTS
We describe 2 assays which can quantify orotic acid in DBS: a stand-alone method and a combined method for analysis of orotic acid, amino acids, and acylcarnitines. Both methods demonstrated orotic acid recovery of 75-85% at multiple levels of enrichment. Precision was also comparable to traditional FIA-MS/MS methods. Analysis of residual presumptively normal NBS specimens demonstrated a 5:1 signal to noise ratio and the average concentration of orotic acid was approximately 1.2 μmol/l. The concentration of amino acids and acylcarnitines as measured by the combined method showed no significant differences when compared to the conventional newborn screening assay. In addition, retrospective analysis of confirmed patients and presumptively normal newborn screening specimens suggests potential for the methods to identify patients with OTC deficiency, as well as other urea cycle defects.
CONCLUSION
The assays described here quantify orotic acid in DBS using a simple extraction and FIA-MS/MS analysis procedures that can be implemented into current NBS protocols.
Topics: Amino Acids; Carnitine; Dried Blood Spot Testing; Female; Flow Injection Analysis; Humans; Infant; Infant, Newborn; Male; Orotic Acid; Reproducibility of Results; Tandem Mass Spectrometry; Time Factors; Urea Cycle Disorders, Inborn
PubMed: 24886687
DOI: 10.1016/j.cca.2014.05.016 -
JIMD Reports Sep 2022N-acetylglutamate synthase (NAGS) deficiency is a rare autosomal recessive disorder, which results in the inability to activate the key urea cycle enzyme,...
N-acetylglutamate synthase (NAGS) deficiency is a rare autosomal recessive disorder, which results in the inability to activate the key urea cycle enzyme, carbamoylphosphate synthetase 1 (CPS1). Patients often suffer life-threatening episodes of hyperammonaemia, both in the neonatal period and also at subsequent times of catabolic stress. Because NAGS generates the cofactor for CPS1, these two disorders are difficult to distinguish biochemically. However, there have now been numerous case reports of 3-methylglutaconic aciduria (3-MGA), a marker seen in mitochondrial disorders, occurring in CPS1 deficiency. Previously, this had not been reported in NAGS deficiency. We report a four-day-old neonate who was noted to have 3-MGA at the time of significant hyperammonaemia and lactic acidosis. Low plasma citrulline and borderline orotic aciduria were additional findings that suggested a proximal urea cycle disorder. Subsequent molecular testing identified bi-allelic pathogenic variants in . The 3-MGA was present at the time of persistent lactic acidosis, but improved with normalization of serum lactate, suggesting that it may reflect secondary mitochondrial dysfunction. NAGS deficiency should therefore also be considered in patients with hyperammonaemia and 3-MGA. Studies in larger numbers of patients are required to determine whether it could be a biomarker for severe decompensations.
PubMed: 36101823
DOI: 10.1002/jmd2.12318 -
Journal of Inherited Metabolic Disease Sep 2014Inborn errors involving enzymes essential for pyrimidine nucleotide metabolism have provided new insights into their fundamental physiological roles as vital...
Inborn errors involving enzymes essential for pyrimidine nucleotide metabolism have provided new insights into their fundamental physiological roles as vital constituents of nucleic acids as well as substrates of lipid and carbohydrate metabolism and in oxidative phosphorylation. Genetic aberrations of pyrimidine pathways lead to diverse clinical manifestations including neurological, immunological, haematological, renal impairments, adverse reactions to analogue therapy and association with malignancies. Maintenance of cellular nucleotides depends on the three aspects of metabolism of pyrimidines: de novo synthesis, catabolism and recycling of these metabolites. Of the ten recognised disorders of pyrimidine metabolism treatment is currently restricted to only two disorders: hereditary orotic aciduria (oral uridine therapy) and mitochondrial neurogastrointestinal encephalomyopathy (MNGIE; allogeneic hematopoetic stem cell transplant and enzyme replacement). The ubiquitous role that pyrimidine metabolism plays in human life highlights the importance of improving diagnostic evaluation in suggestive clinical settings, which will contribute to the elucidation of new defects, future development of novel drugs and therapeutic strategies. Limited awareness of the expanding phenotypic spectrum, with relatively recent descriptions of newer disorders, compounded by considerable genetic heterogeneity has often contributed to the delays in the diagnosis of this group of disorders. The lack of an easily recognisable, easily measurable end product, akin to uric acid in purine metabolism, has contributed to the under-recognition of these disorders.This review describes the currently known inborn errors of pyrimidine metabolism, their variable phenotypic presentations, established diagnostic methodology and recognised treatment options.
Topics: Humans; Purine-Pyrimidine Metabolism, Inborn Errors; Pyrimidines
PubMed: 25030255
DOI: 10.1007/s10545-014-9742-3 -
The Medical Letter on Drugs and... Mar 2016
Topics: Acetates; Administration, Oral; Biomarkers; Drug Costs; Humans; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase; Purine-Pyrimidine Metabolism, Inborn Errors; Treatment Outcome; Uridine
PubMed: 27027693
DOI: No ID Found -
Journal of Human Genetics Sep 2015Ornithine transcarbamylase (OTC) deficiency is an X-linked inborn error of the urea cycle that leads to the accumulation of ammonia, resulting in neurological deficits....
Ornithine transcarbamylase (OTC) deficiency is an X-linked inborn error of the urea cycle that leads to the accumulation of ammonia, resulting in neurological deficits. This study was performed to describe the clinical outcomes, biochemical features and molecular spectra of patients with OTC deficiency. A total of 49 patients from 47 unrelated Korean pedigrees were included who were diagnosed with OTC deficiency based on biochemical findings and molecular analyses. Patient clinical features,biochemical findings and molecular data were analyzed retrospectively. Males with neonatal-onset phenotype presented with seizure or altered mentality (n=20). Biochemical findings showed high blood ammonia (1132.5±851.6 μmol l (− 1)) and urineorotic acid (1840.7±1731.3 mmol mol(− 1) Cr) levels. There were also five males with late-onset disease who presented with vomiting, irritability and seizure at age 8.2±9.4 years old (range, 0.6–20 years). Symptomatic females presented with vomiting,seizure, and altered mentality at age 3.5±3.5 years (range, 0.2–12.8 years; n=24). More males with the late-onset form and symptomatic females displayed mild hyperammonemia and orotic aciduria compared with those showing a neonatal phenotype (P<0.05). Molecular analysis identified 37 different mutations (22 missense, 5 large deletions, 4 small deletions, 1 insertion,3 nonsense and 2 splice sites) from all 49 patients; the mutations were dispersed throughout all coding exons. In Korean patients with OTC deficiency, mutations in OTC are genetically heterogeneous. Male patients with the neonatal-onset phenotype showed poor outcomes because of severe hyperammonemia. Early diagnosis and interventions for hyperammonemia can provide more favorable prognosis.
Topics: Adolescent; Adult; Child; Child, Preschool; DNA Mutational Analysis; Female; Humans; Infant; Infant, Newborn; Male; Ornithine Carbamoyltransferase; Ornithine Carbamoyltransferase Deficiency Disease; Prognosis; Republic of Korea; Retrospective Studies; Young Adult
PubMed: 25994866
DOI: 10.1038/jhg.2015.54 -
Clinica Chimica Acta; International... Jan 2017Clinical management of inherited or acquired hyperammonemia depends mainly on the plasma ammonia level which is not a reliable indicator of urea cycle function as its...
BACKGROUND
Clinical management of inherited or acquired hyperammonemia depends mainly on the plasma ammonia level which is not a reliable indicator of urea cycle function as its concentrations largely fluctuate. The gold standard to assess ureagenesis in vivo is the use of stable isotopes.
METHODS
Here we developed and validated a simplified in vivo method with [N]ammonium chloride ([N]HCl) as a tracer. Non-labeled and [N]urea were quantified by GC-MS after extraction and silylation.
RESULTS
Different matrices were evaluated for suitability of analysis. Ureagenesis was assessed in ornithine transcarbamylase (OTC)-deficient spf mice with compromised urea cycle function during fasted and non-fasted feeding states, and after rAAV2/8-vector delivery expressing the murine OTC-cDNA in liver. Blood (5μL) was collected through tail vein puncture before and after [N]HCl intraperitoneal injections over a two hour period. The tested matrices, blood, plasma and dried blood spots, can be used to quantify ureagenesis. Upon [N]HCl challenge, urea production in spf mice was reduced compared to wild-type and normalized following rAAV2/8-mediated gene therapeutic correction. The most significant difference in ureagenesis was at 30min after injection in untreated spf mice under fasting conditions (19% of wild-type). Five consecutive injections over a period of five weeks had no effect on body weight or ureagenesis.
CONCLUSION
This method is simple, robust and with no apparent risk, offering a sensitive, minimal-invasive, and fast measurement of ureagenesis capacity using dried blood spots. The stable isotope-based quantification of ureagenesis can be applied for the efficacy-testing of novel molecular therapies.
Topics: Animals; Dried Blood Spot Testing; Fasting; Gas Chromatography-Mass Spectrometry; Isotopes; Male; Mice; Ornithine Carbamoyltransferase; Urea
PubMed: 27923571
DOI: 10.1016/j.cca.2016.11.038 -
Journal of Cellular and Molecular... Apr 2021Urea cycle disorders (UCDs) are a group of rare metabolic conditions characterized by hyperammonemia and a broad spectrum of phenotypic severity. They are caused by the...
Urea cycle disorders (UCDs) are a group of rare metabolic conditions characterized by hyperammonemia and a broad spectrum of phenotypic severity. They are caused by the congenital deficiency in the eight biomolecules involved in urea cycle. In the present study, five cases of UCD were recruited and submitted to a series of clinical, biochemical, and genetic analysis with a combination of high throughput techniques. Moreover, in silico analysis was conducted on the identified missense genetic variants. Various clinical and biochemical indications (including profiles of amino acids and urinary orotic acids) of UCD were manifested by the five probands. Sequence analysis revealed nine diagnostic variants, including three novel ones, which caused Argininosuccinic aciduria (ASA) in one case, Carbamoyl phosphate synthetase 1deficiency (CPS1D) in two cases, Ornithine transcarbamylase deficiency (OTCD) in one case, and Citrin deficiency in 1case. Results of in silico biophysical analysis strongly suggested the pathogenicity of each the five missense variants and provided insight into their intramolecular impacts. In conclusion, this study expanded the genetic variation spectrum of UCD, gave solid evidence for counselling to the affected families, and should facilitate the functional study on the proteins in urea cycle.
Topics: Computer Simulation; DNA Mutational Analysis; Female; Humans; Infant; Infant, Newborn; Male; Mutation, Missense; Ornithine Carbamoyltransferase; Pedigree; Prognosis; Urea Cycle Disorders, Inborn
PubMed: 33611823
DOI: 10.1111/jcmm.16379 -
World Journal of Hepatology May 2015The clinical manifestations of hyperammonemia are usually easily identifiable to the clinician when associated with liver disease and lead to prompt diagnosis and...
The clinical manifestations of hyperammonemia are usually easily identifiable to the clinician when associated with liver disease and lead to prompt diagnosis and treatment. However, hyperammonemia-induced encephalopathy is rare in adults in the absence of overt liver disease, thus diagnosis is often delayed or missed leading to potentially life threatening complications. Without proper treatment, such patients can decompensate rapidly with poor outcomes including seizures, coma, and death. Early assessment of plasma ammonia levels in patients with normal hepatic function and characteristic symptoms of encephalopathy can lead to early intervention while investigating the underlying etiology. We describe a patient who presented with a 2-year progression of waxing and waning acute mental status changes after a Roux-en-Y gastric bypass surgery. He was found to have elevated ammonia level as well as orotic aciduria; results consistent with a urea cycle disorder. After consulting neurology as well as toxicology, he ultimately improved after dietary protein restriction, sodium benzoate and lactulose therapy. While rare, clinicians should have a high index of suspicion for late onset urea cycle disorders in symptomatic patients presenting with encephalopathy secondary to hyperammonemia.
PubMed: 25954483
DOI: 10.4254/wjh.v7.i7.1007