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Frontiers in Genetics 2023Hereditary orotic aciduria is an extremely rare, autosomal recessive disease caused by deficiency of uridine monophosphate synthase. Untreated, affected individuals may...
Hereditary orotic aciduria is an extremely rare, autosomal recessive disease caused by deficiency of uridine monophosphate synthase. Untreated, affected individuals may develop refractory megaloblastic anemia, neurodevelopmental disabilities, and crystalluria. Newborn screening has the potential to identify and enable treatment of affected individuals before they become significantly ill. Measuring orotic acid as part of expanded newborn screening using flow injection analysis tandem mass spectrometry. Since the addition of orotic acid measurement to the Israeli routine newborn screening program, 1,492,439 neonates have been screened. The screen has identified ten Muslim Arab newborns that remain asymptomatic so far, with DBS orotic acid elevated up to 10 times the upper reference limit. Urine organic acid testing confirmed the presence of orotic aciduria along with homozygous variations in the gene. Newborn screening measuring of orotic acid, now integrated into the routine tandem mass spectrometry panel, is capable of identifying neonates with hereditary orotic aciduria.
PubMed: 36999056
DOI: 10.3389/fgene.2023.1135267 -
Journal of Genetics and Genomics = Yi... May 2015It is timely to consider the many facets of the small molecule orotic acid (OA), which is well-known as an essential intermediate of pyrimidine de novo synthesis. In... (Review)
Review
It is timely to consider the many facets of the small molecule orotic acid (OA), which is well-known as an essential intermediate of pyrimidine de novo synthesis. In addition, it can be taken up by erythrocytes and hepatocytes for conversion into uridine and for use in the pyrimidine recycling pathway. We discuss the link between dietary orotate and fatty liver in rats, and the potential for the alleviation of neonatal hyperbilirubinaemia. We address the development of orotate derivatives for application as anti-pyrimidine drugs, and of complexes with metal ions and organic cations to assist therapies of metabolic syndromes. Recent genetic data link human Miller syndrome to defects in the dihydroorotate dehydrogenase (DHODH) gene, hence to depleted orotate production. Another defect in pyrimidine biosynthesis, the orotic aciduria arising in humans and cattle with a deficiency of UMP synthase (UMPS), has different symptoms. More recent work leads us to conclude that OA may have a role in regulating gene transcription.
Topics: Animals; Central Nervous System; Enzymes; Humans; Milk; Orotic Acid; Pyrimidines
PubMed: 26059769
DOI: 10.1016/j.jgg.2015.04.001 -
Nucleosides, Nucleotides & Nucleic Acids Dec 2016Orotate (OA) is well-known as a precursor in biosynthesis of pyrimidines; in mammals it is released from the mitochondrial dihydroorotate dehydrogenase (DHODH) for... (Review)
Review
Orotate (OA) is well-known as a precursor in biosynthesis of pyrimidines; in mammals it is released from the mitochondrial dihydroorotate dehydrogenase (DHODH) for conversion to UMP by the cytoplasmic UMP synthase enzyme. OA is also a normal part of the diet, being found in milk and dairy products, and it is converted to uridine for use in the pyrimidine salvage pathway predominantly in liver, kidney and erythrocytes. Early research into nutrition identified orotate as "vitamin B13," and its use as a complex with organic cations or metal ions was promulgated in body-building, and in assisting therapies of metabolic syndromes. It has recently been established that the amelioration of gout by dairy products arises from the competition of orotate and urate at the hURAT1 transporter. The orotic aciduria that arises in children with defective UMP synthase can be rescued by oral uridine therapy, since UMP is the end-product and also a feedback inhibitor of the de novo pathway. In contrast, Miller (dysmorphology) syndrome is connected with defects in DHODH, and hence in the supply of OA, and cannot be helped by uridine. Other models of dysmorphisms are connected with enzymes early in the pyrimidine de novo pathway. We conclude that the OA molecule is itself required for the regulation of genes that are important in the development of cells, tissues and organisms.
Topics: Animals; Anticholesteremic Agents; Diet; Humans; Orotic Acid
PubMed: 27906623
DOI: 10.1080/15257770.2016.1147580 -
Journal of Inherited Metabolic Disease May 2017Elevated urinary excretion of orotic acid is associated with treatable disorders of the urea cycle and pyrimidine metabolism. Establishing the correct and timely...
BACKGROUND
Elevated urinary excretion of orotic acid is associated with treatable disorders of the urea cycle and pyrimidine metabolism. Establishing the correct and timely diagnosis in a patient with orotic aciduria is key to effective treatment. Uridine monophosphate synthase is involved in de novo pyrimidine synthesis. Uridine monophosphate synthase deficiency (or hereditary orotic aciduria), due to biallelic mutations in UMPS, is a rare condition presenting with megaloblastic anemia in the first months of life. If not treated with the pyrimidine precursor uridine, neutropenia, failure to thrive, growth retardation, developmental delay, and intellectual disability may ensue.
METHODS AND RESULTS
We identified mild and isolated orotic aciduria in 11 unrelated individuals with diverse clinical signs and symptoms, the most common denominator being intellectual disability/developmental delay. Of note, none had blood count abnormalities, relevant hyperammonemia or altered plasma amino acid profile. All individuals were found to have heterozygous alterations in UMPS. Four of these variants were predicted to be null alleles with complete loss of function. The remaining variants were missense changes and predicted to be damaging to the normal encoded protein. Interestingly, family screening revealed heterozygous UMPS variants in combination with mild orotic aciduria in 19 clinically asymptomatic family members.
CONCLUSIONS
We therefore conclude that heterozygous UMPS-mutations can lead to mild and isolated orotic aciduria without clinical consequence. Partial UMPS-deficiency should be included in the differential diagnosis of mild orotic aciduria. The discovery of heterozygotes manifesting clinical symptoms such as hypotonia and developmental delay are likely due to ascertainment bias.
Topics: Anemia, Megaloblastic; Child; Child, Preschool; Female; Heterozygote; Humans; Infant; Intellectual Disability; Male; Multienzyme Complexes; Mutation; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase; Purine-Pyrimidine Metabolism, Inborn Errors; Pyrimidines; Urea Cycle Disorders, Inborn; Uridine
PubMed: 28205048
DOI: 10.1007/s10545-017-0015-9 -
Neuropediatrics Dec 2016Orotic aciduria and deficiency of uridine monophosphate synthetase have been observed in a patient, studied over 10 years, who had no megaloblastic anemia. Excretion...
Orotic aciduria and deficiency of uridine monophosphate synthetase have been observed in a patient, studied over 10 years, who had no megaloblastic anemia. Excretion of orotic acid and orotidine were 8.24 and 0.52 mmol/mol of creatinine. The ratio of 15.85 differed appreciably from that of 6 patients reported with no megaloblastic anemia. The analysis of orotidine by gas chromotography mass spectrometry was conducted. Patients with orotic aciduria with and without megaloblastic anemia cannot be distinguished by ratio of orotic acid to orotidine.
Topics: Child; Female; Humans; Orotate Phosphoribosyltransferase; Orotic Acid; Orotidine-5'-Phosphate Decarboxylase; Purine-Pyrimidine Metabolism, Inborn Errors; Uridine; Young Adult
PubMed: 27574833
DOI: 10.1055/s-0036-1587594 -
European Journal of Medicinal Chemistry Dec 2020Uracil is one of the most notable pharmacophores in medicinal chemistry as the pyrimidine nucleobase forms an integral part of many commercial drugs. Though the name... (Review)
Review
Uracil is one of the most notable pharmacophores in medicinal chemistry as the pyrimidine nucleobase forms an integral part of many commercial drugs. Though the name uracil is usually associated with cancer drugs, there are many uracil-based compounds which can treat different diseases when they are employed. So far, there has been no in-depth review concerning uracil drugs in the market, or in the different stages of clinical trials, including those approved or discontinued. The current work focuses on the importance of uracil and its derivatives in treating different diseases. The use of uracil compounds in treating viral infections, cancer, diabetic, thyroid and autosomal recessive disorders are discussed in the review. The mechanism of action of each uracil drug with emphasis on their structure and properties are discussed in detail. The targeted action of these drugs on sites or on the different stages of a disorder/pathogenic life cycle are also discussed. This review encompasses uracil drugs approved as well as those in development from the 1950's onwards. The utility of uracil in drug discovery and its association with a wide range of diseases is brought forth within this review to demonstrate its potential to a wider audience.
Topics: Animals; Antineoplastic Agents; Antiviral Agents; Humans; Hypoglycemic Agents; Uracil
PubMed: 32927231
DOI: 10.1016/j.ejmech.2020.112801 -
International Journal of Developmental... Dec 2022Urea cycle disorders (UCD) are a group of genetic diseases caused by deficiencies in the enzymes and transporters involved in the urea cycle. The impairment of the cycle...
Urea cycle disorders (UCD) are a group of genetic diseases caused by deficiencies in the enzymes and transporters involved in the urea cycle. The impairment of the cycle results in ammonia accumulation, leading to neurological dysfunctions and poor outcomes to affected patients. The aim of this study is to investigate and describe UCD patients' principal clinical and biochemical presentations to support professionals on urgent diagnosis and quick management, aiming better outcomes for patients. We explored medical records of 30 patients diagnosed in a referral center from Brazil to delineate UCD clinical and biochemical profile. Patients demonstrated a range of signs and symptoms, such as altered levels of consciousness, acute encephalopathy, seizures, progressive loss of appetite, vomiting, coma, and respiratory distress, in most cases combined with high levels of ammonia, which is an immediate biomarker, leading to a UCD suspicion. The most prevalent UCD detected were ornithine transcarbamylase deficiency, followed by citrullinemia type 1, hyperargininemia, carbamoyl phosphate synthase 1 deficiency, and argininosuccinic aciduria. Clinical symptoms were highly severe, being the majority developmental and neurological disabilities, with 20% of death rate. Laboratory analysis revealed high levels of ammonia (mean ± SD: 860 ± 470 μmol/L; reference value: ≤80 μmol/L), hypoglycemia, metabolic acidosis, and high excretion of orotic acid in the urine (except in carbamoyl phosphate synthetase 1 [CPS1] deficiency). We emphasize the need of urgent identification of UCD clinical and biochemical conditions, and immediate measurement of ammonia, to enable the correct diagnosis and increase the chances of patients' survival, minimizing neurological and psychomotor damage caused by hepatic encephalopathy.
Topics: Humans; Hyperammonemia; Hepatic Encephalopathy; Ammonia; Urea Cycle Disorders, Inborn; Ornithine Carbamoyltransferase Deficiency Disease
PubMed: 36129623
DOI: 10.1002/jdn.10229 -
Molecular Genetics and Metabolism Aug 2018Carbamoyl phosphate synthetase 1 (CPS1) is a urea cycle enzyme that forms carbamoyl phosphate from bicarbonate, ammonia and ATP. Bi-allelic mutations of the CPS1 gene...
Conditional disruption of hepatic carbamoyl phosphate synthetase 1 in mice results in hyperammonemia without orotic aciduria and can be corrected by liver-directed gene therapy.
Carbamoyl phosphate synthetase 1 (CPS1) is a urea cycle enzyme that forms carbamoyl phosphate from bicarbonate, ammonia and ATP. Bi-allelic mutations of the CPS1 gene result in a urea cycle disorder presenting with hyperammonemia, often with reduced citrulline, and without orotic aciduria. CPS1 deficiency is particularly challenging to treat and lack of early recognition typically results in early neonatal death. Therapeutic interventions have limited efficacy and most patients develop long-term neurologic sequelae. Using transgenic techniques, we generated a conditional Cps1 knockout mouse. By loxP/Cre recombinase technology, deletion of the Cps1 locus was achieved in adult transgenic animals using a Cre recombinase-expressing adeno-associated viral vector. Within four weeks from vector injection, all animals developed hyperammonemia without orotic aciduria and died. Minimal CPS1 protein was detectable in livers. To investigate the efficacy of gene therapy for CPS deficiency following knock-down of hepatic endogenous CPS1 expression, we injected these mice with a helper-dependent adenoviral vector (HDAd) expressing the large murine CPS1 cDNA under control of the phosphoenolpyruvate carboxykinase promoter. Liver-directed HDAd-mediated gene therapy resulted in survival, normalization of plasma ammonia and glutamine, and 13% of normal Cps1 expression. A gender difference in survival suggests that female mice may require higher hepatic CPS1 expression. We conclude that this conditional murine model recapitulates the clinical and biochemical phenotype detected in human patients with CPS1 deficiency and will be useful to investigate ammonia-mediated neurotoxicity and for the development of cell- and gene-based therapeutic approaches.
Topics: Ammonia; Animals; Carbamoyl-Phosphate Synthase (Ammonia); Carbamoyl-Phosphate Synthase I Deficiency Disease; Carbamyl Phosphate; Female; Gene Expression Regulation, Enzymologic; Genetic Therapy; Glutamine; Humans; Hyperammonemia; Liver; Male; Mice; Mice, Knockout; Mutation; Orotate Phosphoribosyltransferase; Orotidine-5'-Phosphate Decarboxylase; Purine-Pyrimidine Metabolism, Inborn Errors
PubMed: 29801986
DOI: 10.1016/j.ymgme.2018.04.001 -
Human Gene Therapy Sep 2023Realization of the immense therapeutic potential of epigenetic editing requires development of clinically predictive model systems that faithfully recapitulate relevant...
Recapitulation of Skewed X-Inactivation in Female Ornithine Transcarbamylase-Deficient Primary Human Hepatocytes in the FRG Mouse: A Novel System for Developing Epigenetic Therapies.
Realization of the immense therapeutic potential of epigenetic editing requires development of clinically predictive model systems that faithfully recapitulate relevant aspects of the target disease pathophysiology. In female patients with ornithine transcarbamylase (OTC) deficiency, an X-linked condition, skewed inactivation of the X chromosome carrying the wild-type OTC allele is associated with increased disease severity. The majority of affected female patients can be managed medically, but a proportion require liver transplantation. With rapid development of epigenetic editing technology, reactivation of silenced wild-type OTC alleles is becoming an increasingly plausible therapeutic approach. Toward this end, privileged access to explanted diseased livers from two affected female infants provided the opportunity to explore whether engraftment and expansion of dissociated patient-derived hepatocytes in the FRG mouse might produce a relevant model for evaluation of epigenetic interventions. Hepatocytes from both infants were successfully used to generate chimeric mouse-human livers, in which clusters of primary human hepatocytes were either OTC positive or negative by immunohistochemistry (IHC), consistent with clonal expansion from individual hepatocytes in which the mutant or wild-type OTC allele was inactivated, respectively. Enumeration of the proportion of OTC-positive or -negative human hepatocyte clusters was consistent with dramatic skewing in one infant and minimal to modest skewing in the other. Importantly, IHC and fluorescence-activated cell sorting analysis of intact and dissociated liver samples from both infants showed qualitatively similar patterns, confirming that the chimeric mouse-human liver model recapitulated the native state in each infant. Also of importance was the induction of a treatable metabolic phenotype, orotic aciduria, in mice, which correlated with the presence of clonally expanded OTC-negative primary human hepatocytes. We are currently using this unique model to explore CRISPR-dCas9-based epigenetic targeting strategies in combination with efficient adeno-associated virus (AAV) gene delivery to reactivate the silenced functional OTC gene on the inactive X chromosome.
Topics: Infant; Humans; Mice; Female; Animals; Ornithine Carbamoyltransferase; X Chromosome Inactivation; Hepatocytes; Liver; Ornithine Carbamoyltransferase Deficiency Disease
PubMed: 37350098
DOI: 10.1089/hum.2023.011 -
Toxicological Sciences : An Official... Apr 2015Orotic acid (OA) is an intermediate of pyrimidine nucleotide biosynthesis. Hereditary deficiencies in some enzymes associated with pyrimidine synthesis or the urea cycle...
Orotic acid (OA) is an intermediate of pyrimidine nucleotide biosynthesis. Hereditary deficiencies in some enzymes associated with pyrimidine synthesis or the urea cycle induce OA accumulation, resulting in orotic aciduria. A link between patients with orotic aciduria and hypertension has been reported; however, the molecular mechanisms remain elusive. In this study, to elucidate the role of OA in vascular insulin resistance, we investigated whether OA induced endothelial dysfunction and hypertension. OA inhibited insulin- or metformin-stimulated nitric oxide (NO) production and endothelial NO synthase (eNOS) phosphorylation in human umbilical vein endothelial cells. A decreased insulin response by OA was mediated by impairment of the insulin-stimulated phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB/Akt) signaling pathway in cells overexpressing the p110-PI3K catalytic subunit. Impaired effects of metformin on eNOS phosphorylation and NO production were reversed in cells transfected with constitutively active AMP-activated protein kinase. Moreover, experimental induction of orotic aciduria in rats caused insulin resistance, measured as a 125% increase in the homeostasis model assessment, and hypertension, measured as a 25% increase in systolic blood pressure. OA increased the plasma concentration of endothelin-1 by 201% and significantly inhibited insulin- or metformin-induced vasodilation. A compromised insulin or metformin response on the Akt/eNOS and AMP-activated protein kinase/eNOS pathway was observed in aortic rings of OA-fed rats. Taken together, we showed that OA induces endothelial dysfunction by contributing to vascular and systemic insulin resistance that affects insulin- or metformin-induced NO production, leading to the development of hypertension.
Topics: Human Umbilical Vein Endothelial Cells; Humans; Hypertension; Insulin; Metformin; Nitric Oxide; Nitric Oxide Synthase Type III; Orotic Acid; Phosphorylation
PubMed: 25601987
DOI: 10.1093/toxsci/kfv003