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Urea cycle disorders (UCDs) are a group of rare inherited metabolic diseases caused by a deficiency of one of the enzymes or transporters that constitute the urea cycle. Defects in these enzymes lead to acute accumulation (hyperammonemic crises, HAC) or chronically elevated levels (hyperammonemia) of ammonia in the blood and/or various tissues including the brain, which can cause persistent neurological deficits, irreversible brain damage, coma, and death. Ongoing treatment of UCDs include the use of nitrogen-scavenging agents, such as sodium phenylbutyrate (salt of 4-phenylbutyric acid; NaPBA) or glycerol phenylbutyrate (GPB). These treatments provide an alternative pathway for nitrogen disposal through the urinary excretion of phenylacetylglutamine. ACER-001 is a novel formulation of NaPBA with polymer coated pellets in suspension, which is designed to briefly mask the unpleasant bitter taste of NaPBA and is being developed as a treatment option for patients with UCDs. Four Phase 1 studies were conducted to characterize the bioavailability (BA) and/or bioequivalence (BE) of ACER-001 (in healthy volunteers) and taste assessment relative to NaPBA powder (in taste panelists). ACER-001 was shown to be bioequivalent to NaPBA powder under both fed and fasting conditions. Lower systemic exposure of phenylacetate (PAA) and phenylbutyrate (PBA) was observed when ACER-001 was administered with a high-fat meal relative to a fasting state suggesting that the lower doses of PBA administered under fasting conditions may yield similar efficacy with potentially fewer dose dependent adverse effects relative to higher doses with a meal. ACER-001 appeared to be adequately taste-masked, staying below the aversive taste threshold for the first 3 min after the formulation was prepared and remaining palatable when taken within 5 min. [ABSTRACT FROM AUTHOR]

The principal aim of this study was to examine the clinical manifestations, biochemical features, and molecular genetic characteristics of Chinese patients with ornithine transcarbamylase deficiency ( OTCD) at a single medical center. We retrospectively analyzed 24 patients (17 males and 7 females) diagnosed with OTCD between 2006 and 2015. Five male patients had a neonatal presentation; 12 male patients had late onset disease and 7 female patients presented as symptomatic. Patients with a neonatal presentation had the highest peak plasma ammonia and glutamine levels at diagnosis with a high mortality (80% vs 16% in late onset disease). Most of the male late onset disease cases displayed neurologic damage with a mild elevation in plasma ammonia, and a significant increase in serum glutamine, which was commonly misdiagnosed as intracranial infection. In the symptomatic female group, mortality was abnormally high in China with some patients dying at the time of presentation during the first episode of hyperammonemia. Refractory hyperammonemia, serious hepatic function damage, recurrent infection and lethal mutation are the main reasons for poor clinical outcomes of the symptomatic females. Molecular analyses identified 19 different mutations, including 3 novel mutations (c. 103insA, c. 591C>A and c. 805G>A). [ABSTRACT FROM AUTHOR]

Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (HHH syndrome) is a neurometabolic disorder with highly variable clinical severity ranging from mild learning disability to severe encephalopathy. Diagnosis of HHH syndrome can easily be delayed or misdiagnosed due to insidious symptoms and incomplete biochemical findings, in that case, genetic testing should be considered to confirm the diagnosis. HHH syndrome is caused by biallelic mutations of SLC25A15, which is involved in the urea cycle and the ornithine transport into mitochondria. Here we report a boy with spastic paraplegia and asymptomatic younger sister who have compound heterozygous mutations of c.535C>T (p.R179*) and c.116C>A (p.T39K) in the SLC25A15 gene. We identified that p.T39K mutation is a novel pathogenic mutation causing HHH syndrome and that p.R179*, which is prevalent in Japanese and Middle Eastern heritage, is also found in the Korean population. [ABSTRACT FROM AUTHOR]

UCDs are among the most common inherited metabolic diseases in Japan. We investigated the clinical manifestations, treatment, and prognoses of 177 patients with UCDs who were evaluated and treated from January 1999 to March 2009 in Japan, using a questionnaire survey. Among these 177 patients, 42 (seven with carbamoyl phosphate synthetase 1 deficiency, 27 with ornithine transcarbamylase deficiency, seven with argininosuccinate synthetase deficiency, and one with arginase 1 deficiency) underwent living-donor LT. Although this study was retrospective and included limited neurodevelopmental information before and after LT, we evaluated whether LT could improve neurodevelopmental outcomes in patients with UCDs. The neurodevelopmental outcomes of patients with a MAC of <300 μmol/L at the time of onset were not significantly different between the LT and non- LT groups ( P=.222). LT may have prevented further neurodevelopmental complications in children with MAC ≥300 μmol/L ( P=.008) compared with non-transplant management. Therefore, Liver transplant should be considered in patients with UCD with a MAC of ≥300 μmol/L at the time of disease onset. [ABSTRACT FROM AUTHOR]

Résumé Les maladies neurométaboliques (MNM) sont un groupe de pathologies nombreuses et complexes. Beaucoup d’entre elles entraînent des anomalies du fonctionnement cérébral, se traduisant par des symptômes neurologiques ou psychiatriques. Nous avons choisi de mettre en valeur sept MNM en lien avec la psychiatrie et bénéficiant d’un traitement médicamenteux. Elles sont parmi les plus fréquentes, et elles sont associées à des signes psychiatriques dans 20 à 70 % des cas. Après avoir abordé les troubles du métabolisme de l’homocystéine du cycle de l’urée, la maladie de Wilson, la xanthomatose cérébrotendineuse, le Niemann-Pick de type C et la porphyrie aiguë, nous discuterons de l’intérêt pour le psychiatre d’enfant et d’adolescent pour l’organicité en général. Enfin, des critères d’atypicité autour des symptômes schizophréniques sont présentés pour aider le psychiatre à chercher ces MNM. Inborn Errors of Metabolism (IEM) are a group of complex diseases. Many of them lead to abnormalities of brain functions, resulting in neurological or psychiatric symptoms. We have chosen to highlight seven IEM related to psychiatry; all of them are treatable. These disorders are among the most common and are frequently associated with psychiatric signs (20 to 70 % of cases). After addressing disorders of homocysteine metabolism, of the urea cycle, Wilson's disease, cerebrotendinous xanthomatosis, Niemann-Pick type C and acute porphyria, we will discuss the interest for psychiatrists for general organicity. Finally, the criteria for atypical features of psychosis are presented to help the psychiatrist to search for these IEM based on clinical psychiatric symptoms. [ABSTRACT FROM AUTHOR]

Urea cycle disorders are commonly seen in the newborn and paediatric population, however presenting cases in adults are uncommon and are usually misdiagnosed before a correct diagnosis is elicited. Several enzymes are involved in the urea cycle, and a defect in any of them can lead to specific laboratory abnormalities and variable clinical presentations. Deficiency of the enzyme ornithine transcarbamylase (OTC) is the most common inherited urea cycle disorder; however, other less common enzyme deficits have been described. In adults, manifestations range from severe encephalopathy to subtle psychiatric manifestations. Prompt diagnosis and recognition are essential to a successful outcome. In this article, we present the case of a 28-year-old female admitted to an A&E department with encephalopathy of unknown aetiology resulting in a diagnosis of carbomoyl synthetase 1 deficiency as well as an unfortunate outcome. [ABSTRACT FROM AUTHOR]

Diagnosis of the urea cycle disorder (USD) carbamoyl-phosphate synthetase 1 (CPS1) deficiency (CPS1D) based on only the measurements of biochemical intermediary metabolites is not sufficient to properly exclude other UCDs with similar symptoms. We report the first Korean CPS1D patient using whole exome sequencing (WES). A four-day-old female neonate presented with respiratory failure due to severe metabolic encephalopathy with hyperammonemia (1,690 µmol/L; reference range, 11.2-48.2 µmol/L). Plasma amino acid analysis revealed markedly elevated levels of alanine (2,923 µmol/L; reference range, 131-710 µmol/L) and glutamine (5,777 µmol/L; reference range, 376-709 µmol/L), whereas that of citrulline was decreased (2 µmol/L; reference range, 10-45 µmol/L). WES revealed compound heterozygous pathogenic variants in the CPS1 gene: one novel nonsense pathogenic variant of c.580C>T (p.Gln194*) and one known pathogenic frameshift pathogenic variant of c.1547delG (p.Gly516Alafs*5), which was previously reported in Japanese patients with CPS1D. We successfully applied WES to molecularly diagnose the first Korean patient with CPS1D in a clinical setting. This result supports the clinical applicability of WES for cost-effective molecular diagnosis of UCDs. [ABSTRACT FROM AUTHOR]

Urea cycle disorders (UCD) are inborn errors of metabolism that occur due to a loss of function in enzymes and transporters involved in the urea cycle, causing an intoxication by hyperammonemia and accumulation of metabolites. Patients can develop hepatic encephalopathy (HE), severe neurological and motor disabilities, and often death. The mechanisms involved in the pathophysiology of UCD are many and complex, but there are strong indications that oxidative stress and inflammation are present, being responsible for at least part of the cellular damage that occurs in these diseases. The aim of this study was to evaluate oxidative and nitrosative damage and inflammation in UCD, to better understand the pathophysiology mechanisms of these diseases. We evaluated the nitrite and nitrate content, thiobarbituric acid-reactive substances (TBARS), carbonyl protein content and a panel of cytokines in plasma sample of 14 patients. The UCD patients group consisted of individuals affected with ornithine transcarbamylase deficiency (n = 8), carbamoyl phosphate synthetase deficiency (n = 2), argininosuccinate synthetase deficiency (n = 2); arginase 1 deficiency (n = 1) and argininosuccinate lyase deficiency (n = 1). Patients mean age at diagnosis was 5.25 ± 9.86 years-old and mean concentrations were compared with healthy individuals of matched age and gender. We found a significant reduction in nitrogen reactive species in patients when compared to controls. TBARS was increased in patients, indicating lipid peroxidation. To evaluate protein oxidative damage in UCD, the carbonyl content was measured, and the results also demonstrated an increase in this biomarker. Finally, we found that UCD patients have enhanced concentrations of cytokines, with pro-inflammatory interleukins IL-6, IL-8, interferon-γ and TNF-α, and anti-inflammatory IL-10 being increased when compared to the control group. In conclusion, our results demonstrate that oxidative stress and inflammation occurs in UCD and probably contribute to the severe brain damage present in patients. [Display omitted] • UCD patients showed high levels of lipid peroxidation, TBARS and carbonyl content, demonstrating oxidative damage. • UCD patients present high levels of cytokines pro- and anti-inflammatory, demonstrating of pro-inflammatory status. • Oxidative stress and inflammation might play an important role in neurotoxicity present in UCD. [ABSTRACT FROM AUTHOR]

Résumé Les déficits du cycle de l’urée ( urea cycle disorders , UCD) sont des maladies héréditaires du métabolisme dont les signes cliniques sont en majeure partie dus à une intoxication par l’ammoniac. Les UCD peuvent se révéler à tout âge. Les décompensations aiguës associent des signes neuropsychiatriques tels que céphalées, confusion, crises convulsives, ataxie, agitation, délire, et digestifs, notamment des nausées, des vomissements, ou des douleurs abdominales. En l’absence de traitement, les patients peuvent évoluer rapidement vers un coma non réversible. L’étape essentielle est de mettre en évidence une hyperammoniémie en urgence, afin de prescrire un traitement approprié dans les plus brefs délais. Urea cycle disorders (UCDs) are inborn errors of metabolism in which the clinical picture is mostly due to ammonia intoxication. UCD onset may be observed at any age. Acute decompensations of UCDs include neuro-psychiatric symptoms such as headache, confusion, convulsions, ataxia, agitation or delirium, as well as digestive symptoms, namely nausea and vomiting along with abdominal pain. Acute decompensations may lead to an irreversible coma in the absence of specific therapy. The first step is to measure promptly ammonemia in such patients, and start appropriate therapy on an emergency basis. [ABSTRACT FROM AUTHOR]

Urea cycle disorders (UCD) are inborn errors of metabolism caused by deficiency of enzymes required to convert nitrogen from ammonia into urea. Current paradigms of treatment focus on dietary manipulations, ammonia scavenger drugs, and liver transplantation. The aim of this study was to describe the characteristics and indication of liver transplantation in UCD in a tertiary hospital. We performed a retrospective study of children with UCD seen in the period 2000-2021. Data was collected on clinical onset, hyperammonemia severity, evolution and liver transplantation. There were 33 patients in the study period, whose diagnosis were: ornithine transcarbamylase (OTC, n  = 20, 10 females), argininosuccinate synthetase (ASS, n  = 6), carbamylphosphate synthetase 1 (CPS1, n  = 4), argininosuccinate lyase (ASL, n  = 2) and N-acetylglutamate synthetase (NAGS, n  = 1) deficiency. Thirty one were detected because of clinical symptoms (45% with neonatal onset). The other 2 were diagnosed being presymptomatic, by neonatal/family screening. Neonatal forms ( n  = 14) were more severe, all of them presented during the first week of life as severe hyperammonemia (mean peak 1,152 µmol/L). Seven patients died (6 at debut) and all survivors received transplantation. There was no mortality among the late forms. Of the 27 patients who did not die in the neonatal period, 16 (59%) received liver transplantationwith 100% survival, normal protein tolerance and usual need of citrulline supplementation. The transplant's metabolic success was accompanied by neurologic sequelae in 69%, but there was no progression of brain damage. Decision of continuous medical treatment in 11 patients appeared to be related with preserved neurodevelopment and fewer metabolic crises., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2023 García Vega, Andrade, Morais, Frauca, Muñoz Bartolo, Lledín, Bergua and Hierro.)

Background: The efficacy and safety of intra-venous (i.v.) sodium benzoate for treating acute episodes of hyperammonemia in urea cycle enzyme disorders (UCD) is well known. However, published data do not provide a clear picture of the benefits and risks of this drug. We report a retrospective multicentre study on the use of i.v. sodium benzoate in patients treated for UCD between 2000 and 2010 in the 6 French reference centres for metabolic diseases. Results: Sixty-one patients with UCDs - 22 ornithine transcarbamylase (20 confirmed, 2 suspected), 18 arginino-succinate synthetase, 15 carbamoyl phosphate synthetase, 3 arginosuccinate lyase, 1 arginase deficiency, 1 N-acetylglutamate synthetase, 1 HHH syndrome - required i.v. sodium benzoate over the course of 95 acute episodes (NH3 > 100 µmol/L or high-risk situations, i.e., gastroenteritis, surgery). Forty out of 61 patients experienced only one episode of decompensation (neonatal coma, 68.6%). The most frequent cause of late decompensation was infection (55.5%). A loading dose of i.v. sodium benzoate (median 250 mg/kg over 2 h) was administered for 41/95 acute episodes. The median maintenance dose was 246.1 mg/kg/day, administered via peripheral venous infusion in all cases except one via a central line. The total median duration of i.v. sodium benzoate treatment per episode was 2 days (0-13 days). The median durations of hospitalization in intensive care and metabolic units were 4 days (0-17 days) and 10 days (0-70 days), respectively. Eight patients died during the neonatal coma (n = 6) or surgery (n = 2). The median plasma ammonium level before treatment was 245.5 µmol/L (20.0-2274. 0 µmol/L); it decreased to 40.0 µmol/L in patients who were alive (13.0-181.0 µmol/L) at the end of treatment with i.v. sodium benzoate. A decrease in ammonium level to ≤ 100 µmol/L was obtained in 92.8% of episodes (64/69 of the episodes recorded for the 53 surviving patients). Five patients required another treatment for hyperammonemia (sodium phenylacetate + sodium benzoate, haemofiltration). Eighteen side effects were reported related to the i.v. infusion (local diffusion, oedema). Conclusion: This 10-year retrospective study shows that i.v. sodium benzoate associated with an emergency regimen is an effective and safe treatment for acute episodes of UCD. [ABSTRACT FROM AUTHOR]

Background: Urea cycle disorders (UCDs) are rare inherited metabolic defects of ammonia detoxification. In about half of patients presenting with a UCD, the first symptoms appear within a few days after birth. These neonatal onset patients generally have a severe defect of urea cycle function and their survival and outcome prognoses are often limited. To understand better the current situation of neonatal onset in UCDs, we have performed a multicentre, retrospective, non-interventional case series study focussing on the most severe UCDs, namely defects of carbamoyl phosphate synthetase 1 (CPS1), ornithine transcarbamylase (OTC), and argininosuccinate synthetase (ASS).Methods and Results: Data of 63 patients were collected (27 patients with ASS deficiency, 23 patients with OTC deficiency, and 12 patients with CPS1 deficiency, one patient definite diagnosis not documented). The majority of patients (43/63, 68 %) had an initial ammonia concentration exceeding 500 μmol/L (normal < 100), of which most (26/43, 60.5 %) were also encephalopathic and were treated with hemodialysis. In patients surviving the initial crisis, recurrence of hyperammonemic events within the first 1.5 years of life occurred frequently (mean 3.6 events, range 0-20). Of all patients, 16 (25.4 %) died during or immediately after the neonatal period.Conclusion: We observed in this cohort of neonatal onset UCD patients a high rate of initial life-threatening hyperammonemia and a high risk of recurrence of severe hyperammonemic crises. These corresponded to a high mortality rate during the entire study period (30.2 %) despite the fact that patients were treated in leading European metabolic centers. This underlines the need to critically re-evaluate the current treatment strategies in these patients. [ABSTRACT FROM AUTHOR]

Objective: The urea cycle disorders (UCD) are inherited deficiencies of the enzymes or transport molecules involved in the cellular excretion of excess ammonia produced during protein metabolism. The aim of this study was to evaluate the clinical characteristics and long-term outcome of pediatric patients with UCD seen during childhood. Methods: Clinical characteristics in 13 patients with classical UCD (carbamoyl phosphate synthetase I deficiency (n=4), argininosuccinate lyase deficiency (n=4), argininosuccinate synthetase deficiency (n=3), arginase deficiency (n=1), and ornithine transcarbamylase deficiency (n=1)) were defined. The term Â"neonatal-onsetÂ" UCD was used if symptoms occurred within 28 days of life, and Â"late-onsetÂ" if symptoms started after that period. Results: The majority of patients (n=9) presented with acute metabolic crisis during newborn period. Core clinical phenotype in neonatal-onset UCD included sepsis-like neonatal crisis revealed in patients within 28 days after birth, whereas mental retardation was predominant peculiarity in late-onset UCD emerging more than 28 days after birth. Vomiting and hypotonia were frequently reported in neonatalonset UCD, and epilepsy with/without movement disorder was found in late-onset UCD patients. For patients with neonatal-onset UCD hyperammonemia was more severe at first diagnosis of the disease, and remained near upper limits of normal during the follow-up period. However, hyperammonemia and metabolic crisis have been reported lomber spinal stenoz frequently in symptomatic patients. A cardinal principal of UCD in acute and long-term management of UCD. Despite these evolving treatment opportunities, still higher mortality rates were found in neonatal-onset UCD (44% (4/9)). Conclusion: Neonatal-onset UCD were generally presents itself as acute onset hyperammonemia during the newborn period. However, neurological manifestations were reportedly more diagnostic in the lateonset UCD. It has been concluded that the basic principles of diagnosis and treatment need to be reorganized to improve recognition and outcome in these diseases. [ABSTRACT FROM AUTHOR]

Inborn errors of metabolism (IEM) comprise a heterogeneous group of more than 1000 diseases with extreme clinical variability and severity of manifestation. These disorders often present themselves mainly in childhood. However, a number of less severe and lateronset forms often with a varied psychiatric manifestation (PM) has been described lately. Since the diseases are rare, clinical experience with particular disorder is usually diminutive. The aim of this work is to shed light upon the issue of PM in patients with IEM, to outline the principles of the pathophysiology of IEM and to raise awareness of this group of disorders upon examples of selected diseases case reports. Cautionary signs of PM of IEM can be familial occurence and early onset of the disease, conspicious fluctuation of clinical signs, cognitive deterioration, visual hallucinations, presence of catatonia, resistance to common treatment, higher frequency of adverse events of the therapy or even worsening of PM after its commencement. Typical examples of such disorders are urea cycle defects, disorders of sulfur amino acids metabolism, acute porphyrias, Niemann-Pick disease type C, Tay-Sachs disease, adult form of metachromatic leukodystrophy, X-linked adrenoleukodystrophy, Wilson disease and mitochondrial diseases. The diagnostics is intricate and ought to be conducted in cooperation with a specialised centre. Its importance is emphasized by the availability of effective therapy for a number of these disorders. [ABSTRACT FROM AUTHOR]

Objectives Biallelic mutations in the ARG1 gene result in an uncommon autosomal recessive inborn defect of the urea cycle known as hyperargininemia (OMIM # 207800 ). ARG1 splicing mutations are not reported often, and they are probably related to a more severe phenotype than missense mutations. In this article, we describe the results of molecular studies in a young hyperargininemia patient carrying a novel splicing mutation in ARG1 . Design and methods Molecular analyses included PCR amplification and direct nucleotide sequencing of the ARG1 gene. RT-PCR analysis was performed to investigate the effect of the mutation in mRNA splicing and in the expression of ARG1 isoforms. Results Mutational analysis identified a novel homozygous ARG1 IVS4-1G > C point mutation in the patient's DNA. Blood leukocyte mRNA was analyzed to demonstrate the splicing defect caused by this mutation. Sequencing of ARG1 RT-PCR products allowed the characterization of a mutated transcript retaining 51-bp from intron 4. In addition, two new, alternatively spliced ARG1 transcripts lacking either exon 4 or exons 4 and 5 were identified in mRNA from the patient and from controls. Conclusions Our results expand the mutational spectrum in hyperargininemia patients and indicate that the novel splicing mutation results in an aberrant transcript retaining intronic sequences. Two novel alternatively spliced ARG1 transcripts were also recognized. [ABSTRACT FROM AUTHOR]

Several studies have shown that a large percentage of inborn errors of metabolism is present in adolescent patients. Individually, each diagnosis in this category of diseases is rare; therefore, there is often a significant delay in determining the etiology of a patient's complaints. These disorders can have a wide variety of multisystemic presentations, several of which overlap with more common disorders of adolescence. This review highlights the red-flag findings on history and physical examination indicating a possible inborn error of metabolism. In addition, a systematic approach for evaluating and categorizing these disorders is introduced and demonstrated through case examples. Primary care physicians play a crucial role in the early detection and prompt treatment of patients with late-onset inborn errors of metabolism. [ABSTRACT FROM AUTHOR]

Background: Hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a rare autosomal recessive disorder of the urea cycle. HHH has a panethnic distribution, with a major prevalence in Canada, Italy and Japan. Acute clinical signs include intermittent episodes of vomiting, confusion or coma and hepatitis-like attacks. Alternatively, patients show a chronic course with aversion for protein rich foods, developmental delay/intellectual disability, myoclonic seizures, ataxia and pyramidal dysfunction. HHH syndrome is caused by impaired ornithine transport across the inner mitochondrial membrane due to mutations in SLC25A15 gene, which encodes for the mitochondrial ornithine carrier ORC1. The diagnosis relies on clinical signs and the peculiar metabolic triad of hyperammonemia, hyperornithinemia, and urinary excretion of homocitrulline. HHH syndrome enters in the differential diagnosis with other inherited or acquired conditions presenting with hyperammonemia. Methods: A systematic review of publications reporting patients with HHH syndrome was performed. Results: We retrospectively evaluated the clinical, biochemical and genetic profile of 111 HHH syndrome patients, 109 reported in 61 published articles, and two unpublished cases. Lethargy and coma are frequent at disease onset, whereas pyramidal dysfunction and cognitive/behavioural abnormalities represent the most common clinical features in late-onset cases or during the disease course. Two common mutations, F188del and R179* account respectively for about 30% and 15% of patients with the HHH syndrome. Interestingly, the majority of mutations are located in residues that have side chains protruding into the internal pore of ORC1, suggesting their possible interference with substrate translocation. Acute and chronic management consists in the control of hyperammonemia with protein-restricted diet supplemented with citrulline/arginine and ammonia scavengers. Prognosis of HHH syndrome is variable, ranging from a severe course with disabling manifestations to milder variants compatible with an almost normal life. Conclusions: This paper provides detailed information on the clinical, metabolic and genetic profiles of all HHH syndrome patients published to date. The clinical phenotype is extremely variable and its severity does not correlate with the genotype or with recorded ammonium/ornithine plasma levels. Early intervention allows almost normal life span but the prognosis is variable, suggesting the need for a better understanding of the still unsolved pathophysiology of the disease. [ABSTRACT FROM AUTHOR]

Glutamine metabolism is generally regarded as proceeding via glutaminase-catalyzed hydrolysis to glutamate and ammonia, followed by conversion of glutamate to α-ketoglutarate catalyzed by glutamate dehydrogenase or by a glutamate-linked aminotransferase (transaminase). However, another pathway exists for the conversion of glutamine to α-ketoglutarate that is often overlooked, but is widely distributed in nature. This pathway, referred to as the glutaminase II pathway, consists of a glutamine transaminase coupled to ω-amidase. Transamination of glutamine results in formation of the corresponding α-keto acid, namely, α-ketoglutaramate (KGM). KGM is hydrolyzed by ω-amidase to α-ketoglutarate and ammonia. The net glutaminase II reaction is: L - Glutamine + α - keto acid + HO → α - ketoglutarate + L - amino acid + ammonia. In this mini-review the biochemical importance of the glutaminase II pathway is summarized, with emphasis on the key component KGM. Forty years ago it was noted that the concentration of KGM is increased in the cerebrospinal fluid (CSF) of patients with hepatic encephalopathy (HE) and that the level of KGM in the CSF correlates well with the degree of encephalopathy. In more recent work, we have shown that KGM is markedly elevated in the urine of patients with inborn errors of the urea cycle. It is suggested that KGM may be a useful biomarker for many hyperammonemic diseases including hepatic encephalopathy, inborn errors of the urea cycle, citrin deficiency and lysinuric protein intolerance. [ABSTRACT FROM AUTHOR]

Background: Advances in the diagnosis and treatment of urea cycle disorders (UCDs) have led to a higher survival rate. The purpose of this study is to describe the characteristics of patients with urea cycle disorders in Spain. Methods: Observational, cross-sectional and multicenter study. Clinical, biochemical and genetic data were collected from patients with UCDs, treated in the metabolic diseases centers in Spain between February 2012 and February 2013, covering the entire Spanish population. Heterozygous mothers of patients with OTC deficiency were only included if they were on treatment due to being symptomatic or having biochemistry abnormalities. Results: 104 patients from 98 families were included. Ornithine transcarbamylase deficiency was the most frequent condition (64.4%) (61.2% female) followed by type 1 citrullinemia (21.1%) and argininosuccinic aciduria (9.6%). Only 13 patients (12.5%) were diagnosed in a pre-symptomatic state. 63% of the cases presented with type intoxication encephalopathy. The median ammonia level at onset was 298 μmol/L (169-615). The genotype of 75 patients is known, with 18 new mutations having been described. During the data collection period four patients died, three of them in the early days of life. The median current age is 9.96 years (5.29-18), with 25 patients over 18 years of age. Anthropometric data, expressed as median and z-score for the Spanish population is shown. 52.5% of the cases present neurological sequelae, which have been linked to the type of disease, neonatal onset, hepatic failure at diagnosis and ammonia values at diagnosis. 93 patients are following a protein restrictive diet, 0.84 g/kg/day (0.67-1.10), 50 are receiving essential amino acid supplements, 0.25 g/kg/day (0.20-0.45), 58 arginine, 156 mg/kg/day (109-305) and 45 citrulline, 150 mg/kg/day (105-199). 65 patients are being treated with drugs: 4 with sodium benzoate, 50 with sodium phenylbutyrate, 10 with both drugs and 1 with carglumic acid. Conclusions: Studies like this make it possible to analyze the frequency, natural history and clinical practices in the area of rare diseases, with the purpose of knowing the needs of the patients and thus planning their care. [ABSTRACT FROM AUTHOR]

Background In recent decades, considerable progress in diagnosis and treatment of patients with intoxication-type inborn errors of metabolism (IT-IEM) such as urea cycle disorders (UCD), organic acidurias (OA), maple syrup urine disease (MSUD), or tyrosinemia type 1 (TYR 1) has resulted in a growing group of long-term survivors. However, IT-IEM still require intense patient and caregiver effort in terms of strict dietetic and pharmacological treatment, and the threat of metabolic crises is always present. Furthermore, crises can affect the central nervous system (CNS), leading to cognitive, behavioural and psychiatric sequelae. Consequently, the well-being of the patients warrants consideration from both a medical and a psychosocial viewpoint by assessing health-related quality of life (HrQoL), psychological adjustment, and adaptive functioning. To date, an overview of findings on these topics for IT-IEM is lacking. We therefore aimed to systematically review the research on HrQoL, psychological adjustment, and adaptive functioning in patients with IT-IEM. Methods Relevant databases were searched with predefined keywords. Study selection was conducted in two steps based on predefined criteria. Two independent reviewers completed the selection and data extraction. Results Eleven articles met the inclusion criteria. Studies were of varying methodological quality and used different assessment measures. Findings on HrQoL were inconsistent, with some showing lower and others showing higher or equal HrQoL for IT-IEM patients compared to norms. Findings on psychological adjustment and adaptive functioning were more consistent, showing mostly either no difference or worse adjustment of IT-IEM patients compared to norms. Single medical risk factors for HrQoL, psychological adjustment, or adaptive functioning have been addressed, while psychosocial risk factors have not been addressed. Conclusion Data on HrQoL, psychological adjustment, and adaptive functioning for IT-IEM are sparse. Studies are inconsistent in their methodological approaches, assessment instruments and norm populations. A disease-specific standard assessment procedure for HrQoL is not available. Psychosocial risk factors for HrQoL, psychological adjustment, or adaptive functioning have not been investigated. Considering psychosocial variables and their corresponding risk factors for IT-IEM would allow evaluation of outcomes and treatments as well as the planning of effective social and psychological interventions to enhance the patients' HrQoL. [ABSTRACT FROM AUTHOR]

Background : Urea cycle disorders are caused by dysfunction in any of the six enzymes and two transport proteins involved in urea biosynthesis. Our study focuses on ornithine transcarbamylase deficiency (OTCD), an X-linked disorder that results in a dysfunctional mitochondrial enzyme, which prevents the synthesis of citrulline from carbamoyl phosphate and ornithine. This enzyme deficiency can lead to hyperammonemic episodes and severe cerebral edema. The objective of this study was to use a cognitive battery to expose the cognitive deficits in asymptomatic carriers of OTCD. Materials and methods : In total, 81 participants were recruited as part of a larger urea cycle disorder imaging consortium study. There were 25 symptomatic participants (18 female, 7 male, 25.6 years ± 12.72 years), 20 asymptomatic participants (20 female, 0 male, 37.6 years ± 15.19 years), and 36 healthy control participants (21 female, 15 male, 29.8 years ± 13.39 years). All participants gave informed consent to participate and were then given neurocognitive batteries with standard scores and T scores recorded. Results : When stratified by symptomatic participant, asymptomatic carrier, and control, the results showed significant differences in measures of executive function (e.g. CTMT and Stroop) and motor ability (Purdue Assembly) between all groups tested. Simple attention, academic measures, language and non-verbal motor abilities showed no significant differences between asymptomatic carriers and control participants, however, there were significant differences between symptomatic and control participant performance in these measures. Conclusions : In our study, asymptomatic carriers of OTCD showed no significant differences in cognitive function compared to control participants until they were cognitively challenged with fine motor tasks, measures of executive function, and measures of cognitive flexibility. This suggests that cognitive dysfunction is best measurable in asymptomatic carriers after they are cognitively challenged. [ABSTRACT FROM AUTHOR]

Glycerol phenylbutyrate (GPB) is a new generation ammonia scavenger drug that was recently approved by the US FDA for chronic management in patients with urea cycle defect disorders after multicenter clinical trials. GPB is composed of three molecules of phenylbutyrate (PB) that are esterified to a glycerol backbone. The active agent, phenylacetate, is generated through multiple metabolic steps including hydrolysis in the small intestine by pancreatic triglyceride lipases. Its pharmacokinetic pattern is characterized by a slower release of the active metabolite than unconjugated PB, which contributes to superior ammonia control and fewer episodes of hyperammonemia. GPB is well tolerated with fewer gastrointestinal complications compared with sodium benzoate or PB. These unique features suggest that it may enhance adherence and, potentially, in improved outcomes in urea cycle disorder patients. GPB may have therapeutic potential in additional conditions such as chronic hepatic encephalopathy or other inherited metabolic disorders. [ABSTRACT FROM AUTHOR]

The urea cycle is the primary nitrogen-disposal pathway in humans. It requires the coordinated function of six enzymes and twomitochondrial transporters to catalyze the conversion of amolecule of ammonia, the α-nitrogen of aspartate, and bicarbonate into urea. Whereas ammonia is toxic, urea is relatively inert, soluble in water, and readily excreted by the kidney in the urine. Accumulation of ammonia and other toxic intermediates of the cycle lead to predominantly neurologic sequelae. The disorders may present at any age from the neonatal period to adulthood, with the more severely affected patients presenting earlier in life. Patients are at risk for metabolic decompensation throughout life, often triggered by illness, fasting, surgery and postoperative states, peripartum, stress, and increased exogenous protein load. Here the authors address neurologic presentations of ornithine transcarbamylase deficiency in detail, the most common of the urea cycle disorders, neuropathology, neurophysiology, and our studies in neuroimaging. Special attention to late-onset presentations is given. [ABSTRACT FROM AUTHOR]

Abstract: Objective: To evaluate glycerol phenylbutyrate (GPB) in the treatment of pediatric patients with urea cycle disorders (UCDs). Study design: UCD patients (n=26) ages 2months through 17years were treated with GPB and sodium phenylbutyrate (NaPBA) in two short-term, open-label crossover studies, which compared 24-hour ammonia exposure (AUC0–24) and glutamine levels during equivalent steady-state dosing of GPB and sodium phenylbutyrate (NaPBA). These 26 patients plus an additional 23 patients also received GPB in one of three 12-month, open label extension studies, which assessed long-term ammonia control, hyperammonemic (HA) crises, amino acid levels, and patient growth. Results: Mean ammonia exposure on GPB was non-inferior to NaPBA in each of the individual crossover studies. In the pooled analyses, it was significantly lower on GPB vs. NaPBA (mean [SD] AUC0–24: 627 [302] vs. 872 [516] μmol/L; p=0.008) with significantly fewer abnormal values (15% on GPB vs. 35% on NaPBA; p=0.02). Mean ammonia levels remained within the normal range during 12months of GPB dosing and, when compared with the 12months preceding enrollment, a smaller percentage of patients (24.5% vs. 42.9%) experienced fewer (17 vs. 38) HA crises. Glutamine levels tended to be lower with GPB than with NaPBA during short-term dosing (mean [SD]: 660.8 [164.4] vs. 710.0 [158.7] μmol/L; p=0.114) and mean glutamine and branched chain amino acid levels, as well as other essential amino acids, remained within the normal range during 12months of GPB dosing. Mean height and weight Z-scores were within normal range at baseline and did not change significantly during 12months of GPB treatment. Conclusions: Dosing with GPB was associated with 24-hour ammonia exposure that was non-inferior to that during dosing with NaPBA in individual studies and significantly lower in the pooled analysis. Long-term GPB dosing was associated with normal levels of glutamine and essential amino acids, including branched chain amino acids, age-appropriate growth and fewer HA crises as compared with the 12month period preceding enrollment. [Copyright &y& Elsevier]

Argininemia is a rare inherited disorder of the urea cycle because of a deficiency of the enzyme arginase I causing an increase of arginine and guanidino compounds in the blood, urine, and cerebrospinal fluid. The clinical picture is characterized by a mild cognitive dysfunction, progressive asymmetrical paraparesis, and seizures. Here, we describe two cases of argininemia where either epilepsia partialis continua (EPC) or nonconvulsive status epilepticus (NCSE) were the presentingmanifestations of epilepsy. This is the first report of EPC in an urea cycle disorder. In both the cases, status epilepticus resolved with anticonvulsive drugs. EPC was successfully treated with levetiracetam, and NCSE with valproic acid. No side effects were observed. Because hyperammonemia and NCSE may have the same features of stupor, a neurophysiological approach might prove useful in differentiating these two conditions. Overall, our results strongly indicate that a correct NCSE diagnosis is mandatory to prevent further deterioration in these patients. [ABSTRACT FROM AUTHOR]