Aciduria Research Articles

Conducting an investigator-initiated randomized double-blinded intervention trial in acute decompensation of inborn errors of metabolism: Lessons from the N-Carbamylglutamate Consortium.

Organic acidemias and urea cycle disorders are ultra-rare inborn errors of metabolism characterized by episodic acute decompensation, often associated with hyperammonemia, resulting in brain edema and encephalopathy. Retrospective reports and translational studies suggest that N-carbamylglutamate (NCG) may be effective in reducing ammonia levels during acute decompensation in two organic acidemias, propionic and methylmalonic acidemia (PA and MMA), and in two urea cycle disorders, carbamylphosphate synthetase 1 and ornithine transcarbamylase deficiency (CPSD and OTCD). We established the 9-site N-carbamylglutamate Consortium (NCGC) in order to conduct two randomized double-blind, placebo-controlled trials of NCG in acute hyperammonemia of PA, MMA, CPSD and OTCD. Conducting clinical trials is challenging in any disease, but poses unique barriers and risks in the ultra-rare disorders. As the number of clinical trials in orphan diseases increases, evaluating the successes and opportunities for improvement in such trials is essential. We summarize herein the design, methods, experiences, challenges and lessons from the NCGC-conducted trials.

Mild phenotype of glutaric aciduria type 1 in polish patients \u2013 novel data from a group of 13 cases

Glutaric aciduria type 1 is a neurometabolic disorder, caused by riboflavin-dependent glutaryl-CoA dehydrogenase deficiency. As its consequence, accumulation of the putatively neurotoxic metabolites (glutaric and 3-hydroxyglutaric acids) in body tissues, but especially within the brain, is observed. Estimated incidence of the disease is 1 in 110,000 newborns, The prevalence however may be higher, depending on a specific ethnic group, and result in phenotypic variation as well. In this paper we present clinical data of 13 patients of Polish nationality. They all present a mild phenotype and clinical course of glutaric aciduria type 1. Based on their clinical data, presented herein, we like to pay attention to the phenotypic and neuroimaging features important for the diagnosis of mild form of this disease. Moreover, we present novel molecular data, which may correlate with such a manifestation.

Hydrocephalus in cblC type methylmalonic acidemia.

Methylmalonic acidemia (MMA) is a typical type of organic acidemia caused by defects in methylmalonyl-CoA mutase or adenosyl-cobalamin synthesis. Hydrocephalus (HC), results from an imbalance between production and absorption of cerebrospinal fluid (CSF), causeing enlarged cerebral ventricles and increased intracranial pressure, is a condition that requires urgent clinical decision-making. MMA without treatment could result in brain damage. However, HC in MMA was rarely reported. In this study, 147 MMA were identified from 9117 high risk children by gas chromatography mass spectrometry (GC/MS) for organic acidurias screening in urine samples and liquid chromatography-tandem mass spectrometry (LC-MS/MS) for amino acids detection in blood samples. Totally 10 cases with MMA and HC were determined by brain MRI/CT, as well as gene mutation testing either by high throughput sequencing or Sanger sequencing. Besides, homocysteine was also analyzed for the 10 MMA with HC. Out of them, 9 cases carry out compound heterozygous mutations or homozygous mutation in MMACHC gene, and 1 case has MUTmutation. The mutation c.609G > A in MMACHC was the most common in the cbl type patients. Although MMA has a high incidence in Shandong province of China, especially cblC type. All of the 10 patients were not correctly diagnosed before developing HC. As a result, when a child develops progressive and refractory HC, the screening for inherited metabolic diseases should be immediately conducted.

FGF21 underlies a hormetic response to metabolic stress in methylmalonic acidemia.

Methylmalonic acidemia (MMA), an organic acidemia characterized by metabolic instability and multiorgan complications, is most frequently caused by mutations in methylmalonyl-CoA mutase (MUT). To define the metabolic adaptations in MMA in acute and chronic settings, we studied a mouse model generated by transgenic expression of Mut in the muscle. Mut-/-;TgINS-MCK-Mut mice accurately replicate the hepatorenal mitochondriopathy and growth failure seen in severely affected patients and were used to characterize the response to fasting. The hepatic transcriptome in MMA mice was characterized by the chronic activation of stress-related pathways and an aberrant fasting response when compared with controls. A key metabolic regulator, Fgf21, emerged as a significantly dysregulated transcript in mice and was subsequently studied in a large patient cohort. The concentration of plasma FGF21 in MMA patients correlated with disease subtype, growth indices, and markers of mitochondrial dysfunction but was not affected by renal disease. Restoration of liver Mut activity, by transgenesis and liver-directed gene therapy in mice or liver transplantation in patients, drastically reduced plasma FGF21 and was associated with improved outcomes. Our studies identify mitocellular hormesis as a hepatic adaptation to metabolic stress in MMA and define FGF21 as a highly predictive disease biomarker.

Laboratory analysis of amino acids, 2018 revision: a technical standard of the American College of Medical Genetics and Genomics (ACMG)

Amino acid abnormalities are observed in a broad spectrum of inheritedmetabolic diseases, such as disorders of amino acid metabolism and transport,organic acidemias, and ureagenesis defects. Comprehensive analysis of physiologicamino acids in blood, urine, and cerebrospinal fluid is typically performed in thefollowing clinical settings: evaluation of symptomatic patients in whom a diagnosisis not known; evaluation of previously diagnosed patients to monitor treatmentefficacy; evaluation of asymptomatic or presymptomatic (at-risk) relatives of knownpatients; follow-up testing for an abnormal newborn screen; and assessment ofdietary protein adequacy or renal function in general patient populations.Currently, the most common analytical method to quantify amino acids is based on ionexchange chromatography using post-column derivatization with ninhydrin andspectrophotometric detection. Newer methodologies are based on liquidchromatographic separation with detection by mass spectrometry or spectrophotometry.Amino acid analysis by nonseparation methods, such as the flow injection–tandem massspectrometric (MS/MS) method used for newborn screening, is considered inadequatefor the diagnosis of at-risk patients. The purpose of this document is to provide atechnical standard for amino acid analysis as applied to the diagnosis andmanagement of inborn errors of metabolism.

Widespread bacterial lysine degradation proceeding via glutarate and L-2-hydroxyglutarate

Lysine degradation has remained elusive in many organisms including Escherichia coli. Here we report catabolism of lysine to succinate in E. coli involving glutarate and L-2-hydroxyglutarate as intermediates. We show that CsiD acts as an α-ketoglutarate-dependent dioxygenase catalysing hydroxylation of glutarate to L-2-hydroxyglutarate. CsiD is found widespread in bacteria. We present crystal structures of CsiD in complex with glutarate, succinate, and the inhibitor N-oxalyl-glycine, demonstrating strong discrimination between the structurally related ligands. We show that L-2-hydroxyglutarate is converted to α-ketoglutarate by LhgO acting as a membrane-bound, ubiquinone-linked dehydrogenase. Lysine enters the pathway via 5-aminovalerate by the promiscuous enzymes GabT and GabD. We demonstrate that repression of the pathway by CsiR is relieved upon glutarate binding. In conclusion, lysine degradation provides an important link in central metabolism. Our results imply the gut microbiome as a potential source of glutarate and L-2-hydroxyglutarate associated with human diseases such as cancer and organic acidurias.

Renal replacement therapy in neonates with an inborn error of metabolism.

Hyperammonemia can be caused by several genetic inborn errors of metabolism including urea cycle defects, organic acidemias, fatty acid oxidation defects, and certain disorders of amino acid metabolism. High levels of ammonia are extremely neurotoxic, leading to astrocyte swelling, brain edema, coma, severe disability, and even death. Thus, emergency treatment for hyperammonemia must be initiated before a precise diagnosis is established. In neonates with hyperammonemia caused by an inborn error of metabolism, a few studies have suggested that peritoneal dialysis, intermittent hemodialysis, and continuous renal replacement therapy (RRT) are effective modalities for decreasing the plasma level of ammonia. In this review, we discuss the current literature related to the use of RRT for treating neonates with hyperammonemia caused by an inborn error of metabolism, including optimal prescriptions, prognosis, and outcomes. We also review the literature on new technologies and instrumentation for RRT in neonates

Difficulties in the dietary management of a girl with two diseases requiring a special diet.

3-Methylcrotonylglycinuria (3-MCG) is an autosomal recessive inborn error of leucine metabolism caused by the deficiency of 3-methylocrotonyl-CoA carboxylase (3-MCC deficiency). It is the most commonly detected organic aciduria in newborn screening conducted by tandem mass spectrometry (MS/MS) [1, 2]. The clinical phenotype is heterogeneous, ranging from asymptomatic to acute metabolic decompensations [3, 4]. Although at least in severe cases and in acute life threatening episodes limiting natural protein intake (particularly leucine) together with high caloric intake during catabolic periods is required, the need for specific dietary management often seems questionable [2]. In contrast with the 3-MCC deficiency, in diabetes mellitus type 1 (DM1) a diet based on carbohydrate and protein-fat exchangers is beyond dispute. However, as DM1 is quite a common disease, it may occur in a single patient with a rare disease, such as 3-MCC deficiency.

P041 Perioperative management of liver transplantation for organic acidemia, urea cycle disorders and Maple-syrup urine disease

P041 Perioperative management of liver transplantation for organic acidemia, urea cycle disorders and Maple-syrup urine disease

Symmetrical Central Tegmental Tract Hyperintensity on T2-weighted Images in Pediatrics: A Systematic Review

AbstractPurpose: The aim of the present study is to provide a systematic literature review of the current evidence about the Central Tegmental Tract Hyperintensity (CTTH).Methods: The literature search was performed on December 2017 using Medline PubMed, Google Scholar and Cochrane Central databases. Statistical analysis was performed using Kolmogorov-Smirnov, chi-square and the Mann-Whitney U tests.Results: Twenty publications were included. Of these, 11 were retrospective studies and 9 were case reports. In total, CTTH was reported in 226 cases. The age parameter showed a significantly non-Gaussian distribution (KS test; p-value < 0.001). The median age was 1,83 years (range: 7 days – 21 years; P25 = 1.00 year, P75 = 3.00 years; IQR = 2 years). The two most common clinical conditions associated to CTTH were cerebral palsy (51 cases; 22.6%) and glutaric aciduria type 1 (50 cases; 22.10%). CTTH was often found in the absence of other concomitant brain MRI abnormalities (32 cases; 21.8%).Conclusions: CTTH is an uncommon neuroimaging finding that is mainly related to the acquisition\improvement of a physiologicalmotor developmental process. The finding is influenced by hypoxic ischemic and toxic?metabolic factors. Data regarding DWI and follow-up are largely unreported and deserve to be further explored.

Differential response to renal replacement therapy in neonatal-onset inborn errors of metabolism.

Severe urea cycle defects (UCD), organic acidemias (OA) and maple syrup urine disease (MSUD) are life-threatening disorders presenting in the first days of life. Renal replacement therapy (RRT) is an emergency option in affected newborns, mostly performed as ultima ratio. We report our 10-year experience using emergency RRT in newborns with UCD, OA and MSUD. Twelve newborns (eight with UCD, two with methylmalonic acidemia and two with MSUD) underwent emergency RRT. The overall survival rate to RRT was 58.3%. Hyperammonemic newborns required earlier RRT with respect to MSUD patients (75 (65-102) vs 301 (192-410) h of life, P < 0.01). Hyperammonemic neonates surviving (n = 5) and non-surviving (n = 5) the acute neonatal decompensation showed similar birth weight (P = 0.690), duration of intubation (P = 0.917), ammonia at onset (P = 0.916) and at the start of RRT (P = 0.426), age at RRT (P = 0.999) and duration of coma before RRT (P = 0.691). Remarkably, all survivors quickly responded to RRT, with ammonia concentration less than 300 μmol/L after 8 h of treatment. One patient with UCD successfully treated by neonatal RRT died at 4 months of life because of sepsis. All patients with MSUD had normalized leucine levels after 12 h of RRT, surviving the acute neonatal decompenstation. All long-term survivors (five liver transplanted, one waiting for liver transplantation) currently show normal or near-normal neurological development (48 ± 39 months of age). Early response to RRT was associated with survival irrespective of pre-treatment picture. RRT can be considered even in huge neonatal metabolic decompensations. Early liver transplantation may be an option for select patients.

The role of tandem mass spectrometry in the diagnosis of inherited metabolic diseases

This paper reviews the clinical applications of tandem mass spectrometry in diagnosis and screening for inherited metabolic diseases. The broad-spectrum of diseases covered, specificity, ease of sample preparation, and high throughput provided by the MS/MS technology has led to the development of multi-disorder newborn screening programs in many countries for amino acid disorders, organic acidurias, and fatty acid oxidation defects. The application of MS/MS in selective screening has revolutionized the field and made a major impact on the detection of certain disease classes such as the fatty acid oxidation defects. New specific and rapid tandem mass spectrometry (MS/MS) and high performance liquid chromatography–MS/MS methods are supplementing or replacing some of the classical gas chromatography– MS/MS methods for a multitude of metabolites and disorders. In the near future, we should expect the emergence of new promising methods for diagnosing not only individual nosologic forms, but also entire groups of inherited metabolic diseases.

Two novel L2HGDH mutations identified in a rare Chinese family with L-2-hydroxyglutaric aciduria

BackgroundL-2-Hydroxyglutaric aciduria (L-2-HGA) is a rare organic aciduria neurometabolic disease that is inherited as an autosomal recessive mode and have a variety of symptoms, such as psychomotor developmental retardation, epilepsy, cerebral symptoms as well as increased concentrations of 2-hydroxyglutarate (2-HG) in the plasma, urine and cerebrospinal fluid. The causative gene of L-2-HGA is L-2-hydroxyglutarate dehydrogenase gene (L2HGDH), which consists of 10 exons.Case presentationWe presented a rare patient primary diagnosis of L-2-HGA based on the clinical symptoms, magnetic resonance imaging (MRI), and gas chromatography-mass spectrometry (GC-MS) results. Mutational analysis of the L2HGDH gene was performed on the L-2-HGA patient and his parents, which revealed two novel mutations in exon 3: a homozygous missense mutation (c.407 A > G, p.K136R) in both the maternal and paternal allele, and a heterozygous frameshift mutation [c.407 A > G, c.408 del G], (p.K136SfsX3) in the paternal allele. The mutation site p.K136R of the protein was located in the pocket of the FAD/NAD(P)-binding domain and predicted to be pathogenic.ConclusionWe predicted the homozygous missense mutation (c.407 A > G, p.K136R) was considered as the pathogenic mutation of the patient. The study highlights the power of pedigree analysis in order to interpret novel mutations.

MODERN POSSIBILITIES OF HEREDITARY DISEASES TREATMENT IN CHILDREN

In recent decades, the progressive development of medical genetics has led to significant advances in the diagnosis and therapy of hereditary pathology. As a result, the attitude of clinicians to hereditary diseases as to fatal and incurable, is gradually changing. Early dietary therapy of phenylketonuria and a number of other diseases provides full medical and social habilitation of children. Cofactor therapy, including a special vitamin therapy, is crucial in the treatment of enzymopathiessuch as: lack of biotinidase, homocystinuria, etc. Levocarnitine therapy shows high efficiency in a number of organic acidemias. A breakthrough in the treatment of lysosomal diseases should be considered the development of enzyme-substituting and substrate-reducing drugs. Further improvement of the effectiveness of hereditary diseases treatment seems to be associated with the introduction of gene therapy methods.

Molecular genetic study of glutaric aciduria, type I: Identification of a novel mutation

Glutaric acidemia type I (GA-1) is an inborn error of metabolism due to deficiency of glutaryl-CoA dehydrogenase (GCDH), which catalyzes the conversion of glutaryl-CoA to crotonyl-CoA. GA-1 occurs in about 1 in 100 000 infants worldwide. The GCDH gene is on human chromosome 19p13.2, spans about 7 kb and comprises 11 exons and 10 introns. Tandem mass spectrometry (MS/MS) was used for clinical diagnosis in a proband from Iran with GA-1. Sanger sequencing was performed using primers specific for coding exons and exon-intron flanking regions of the GCDH gene in the proband. Cosegregation analysis and in silico assessment were performed to confirm the pathogenicity of the candidate variant. A novel homozygous missense variant c.1147C > A (p.Arg383Ser) in exon 11 of GCDH was identified. Examination of variant through in silico software tools determines its deleterious effect on protein in terms of function and stability. The variant cosegregates with the disease in family. In this study, the clinical and molecular aspects of GA-1 were investigated, which showed one novel mutation in the GCDH gene in an Iranian patient. The variant is categorized as pathogenic according to the the guideline of the American College of Medical Genetics and Genomics (ACMG) for variant interpretation. This mutation c.1147C > A (p.Arg383Ser) may also be prevalent among Iranian populations.

Toe Walking Caused by Congenital Metabolic Diseases following a Specific Case

DOI: 10.26650/experimed.2018.431791 Parmak ucunda yurume ve noral tup defektleri, genellikle norolojik ve ortopedik olgu sunumlari olarak yayinlarda sunulmaktadir. Alti yillik poliklinik tecrubemiz nedeniyle parmak ucunda yurumede Metilen Tetra Hidro Folat Reduktaz (MTHFR) polimorfizmlerine dikkat cekmek icin bu olgu secildi. On yasindaki kiz hasta parmak ucunda yurume ve hafif norolojik gerilikle basvurdu. Aile oykusunde anneannede inme disinda onemli bulgu yoktu. One cikan klinik bulgulari obezite, sakral gamze ve parmak ucunda yurumeydi. Laboratuvar degerlendirmesinde orta derecede lipid yuksekligi, MTHFR A1298C heterozigot mutasyonu gorulmekteydi. Spinal manyetik rezonans goruntuleme (MRI) ile incelemede hipoplazik disk, spondilolistezis ve filar lipom tespit edildi. Klinik hasta izlemimiz sirasinda 8000 hastanin 11 kiz 9 erkek cinsiyette olan toplam 20 hastada parmak ucunda yurume tespit edildi. Bunlarin hastaliklara gore dagilimi 3 gec tani fenilketonuri (PKU), 2 metakromatik lokodistrofi (MLD), 1 L (OH) glutarik asiduri, 3 yag aside oksidasyon bozuklugu (FAO), 1 mitokondriyal hastalik ve 10 MTHFR seklindeydi. FAO grubunda agrili kas kramp ataklari ve kas enzim artislari sirasinda parmak ucunda yurume gozlenmisti. PKU ve MLD’li hastalarda kalici norolojik sorunlarla parmak ucunda yurume iliskisi gorulmekteydi. Kisa Asil tendonu L2 (OH) Glutarik asiduri hastasi parmakucunda yurume nedeniydi. MTHFR’li hastalarda noral tup defektleri on plandaydi (1 sirengomiyeli, 1 filar lipom, 2 spondilolistezis ve 1 gergin kord). Erken doneminde parmak ucunda yurume tanimlanan otizm etiolojisinde MTHFR de yer almaktadir. Hastalarimizdan birinde otizm tanisi vardi. Parmak ucunda yurume sadece Asil tendon ameliyati ile duzeltilebilecek kadar basit bir sorun degildir. Altta yatan sorunun arastirilmasi gerekir.

Quantitation of plasma and urine 3-hydroxyglutaric acid, after separation from 2-hydroxyglutaric acid and other compounds of similar ion transition, by liquid chromatography-tandem mass spectrometry for the confirmation of glutaric aciduria type 1

BackgroundGlutaric aciduria type 1, a deficiency of glutaryl-CoA dehydrogenase, causes an accumulation of neurotoxic metabolites glutaric acid and 3-hydroxyglutaric acid (3-HGA). Testing of these analytes is routinely done by GC–MS but seldom account for interference from isomers or compounds with similar ion transitions. We developed a liquid chromatography tandem mass spectrometry method that accurately measures 3-HGA in urine and plasma specimens, while utilizing similar reagents and instrumentation used for the routine performance of amino acid and acylcarnitine analysis in determining the diagnosis of several metabolic disorders. MethodPlasma and urine samples were added aliquots of the deuterated 3-HGA internal standard and acetonitrile. The protein-free supernatant was brought to dryness, and the residue derivatized using 3 M HCL in 1-butanol with heating. The dried derivative was then reconstituted in 50% methanol-water solution and aliquot transferred to an HPLC vial for analysis by LC-MS/MS. Separation was performed using a C8 HPLC column under flow gradient conditions of 0.2% formic acid in water and methanol, respectively. Ionization was by ESI and detection of selected precursor-product ion transitions by multiple reaction monitoring (MRM) in positive mode. ResultsThe butyl-ester derivative of 3-HGA eluted at 7.82 min while 2-hydroxyglutaric acid (2-HGA) eluted at 8.21 min. This was equivalent to a separation factor of 1.05 and a resolution of 1.03, respectively. The 3-HGA calibration curve was linear over the range 6.20–319 ng mL−1 (r2 = 0.9996), and the reportable range determined by the linearity was found to be 1.54–384 ng mL−1. The calculated limits of detection and quantitation were 0.348 and 1.56 ng mL−1, respectively. Intra- and Inter-assay %CVs for quality control plasma and urine samples ranged from 2 to 18%, with recoveries of 66–115%. The method correlated to the gold standard GC–MS method for both serum (r2 ≥ 0.996) and urine analysis (r2 ≥ 0.949). The concentration of 3-HGA in normal, non-GA1 individuals was ≤25.2 ng mL−1 (in plasma) and ≤ 35.0 μmol mmol−1 of creatinine (in urine). ConclusionsThis LC-MS/MS method accurately quantified plasma and urine 3-HGA concentration after successful resolution from 2-HGA and other compounds with similar ion transitions. This method is suitable for confirmatory testing of 3-HGA, as a follow-up to an abnormal newborn screen test result, with concern for GA type 1.

Diffusion Tensor Imaging Parameters in Children with Acute Hyperammonemic Encephalopathy due to Urea Cycle Enzyme Defects and Organic Acidemia

Diffusion Tensor Imaging Parameters in Children with Acute Hyperammonemic Encephalopathy due to Urea Cycle Enzyme Defects and Organic Acidemia

Development and Validation of GC-MS Bioanalytical Method to Detect Organic Acidemia in Neonatal/Pediatric Urine Samples

This work was aimed at developing an analytical tool for the simultaneous quantification of methylmalonic acid, glutaric acid, succinyl acetone, homogentisic acid, and pipecolic acid in pediatric urine samples. Organic acids were isolated from urine by liquid-liquid extraction. The extracted samples were then derivatized by using BSTFA + 1% TMCS solution, which resulted in the formation of trimethylsilyl ester derivatives. These analytes were quantified by GC-MS, and this bioanalytical method was validated according to the USFDA guidelines. The proposed method was applied to several clinically suspected organic acidemia samples. The linearity range is within 5 – 100 �g/mL for methylmalonic acid and glutaric acid, 20 – 100 �g/mL for succinyl acetone and homogentisic acid, and 10 – 100 �g/mL for pipecolic acid. Mean % recovery of QC samples of methylmalonic acid, glutaric acid, succinyl acetone, homogentisic acid, and pipecolic acid was found to be 92.06, 92.21, 90.92, 93.17, 90.71%, respectively, and that of tropic acid was 96.57%. All organic acids were stable at room temperature for 8 h. The stability of succinyl acetone, homogentisic acid, and pipecolic acid stored for 30 days at 8°C was found to be lower. The proposed method was applied to the analysis of samples obtained from 23 patients.

Liver Transplantation for Propionic Acidemia and Methylmalonic Acidemia: Perioperative Management and Clinical Outcomes.

Propionic acidemia (PA) and methylmalonic acidemia (MMA) comprise the most common organic acidemias and account for profound morbidity in affected individuals. Although liver transplantation (LT) has emerged as a bulk enzyme-replacement strategy to stabilize metabolically fragile patients, it is not a metabolic cure because patients remain at risk for disease-related complications. We retrospectively studied LT and/or liver-kidney transplant in 9 patients with PA or MMA with additional focus on the optimization of metabolic control and management in the perioperative period. Metabolic crises were common before transplant. By implementing a strategy of carbohydrate minimization with gradual but early lipid and protein introduction, lactate levels significantly improved over the perioperative period (P < 0.001). Posttransplant metabolic improvement is demonstrated by improvements in serum glycine levels (for PA; P < 0.001 × 10-14 ), methylmalonic acid levels (for MMA; P < 0.001), and ammonia levels (for PA and MMA; P < 0.001). Dietary restriction remained after transplant. However, no further metabolic crises have occurred. Other disease-specific comorbidities such as renal dysfunction and cardiomyopathy stabilized and improved. In conclusion, transplant can provide a strategy for altering the natural history of PA and MMA providing stability to a rare but metabolically brittle population. Nutritional management is critical to optimize patient outcomes.