fumarates and Metabolism--Inborn-Errors

Fumaric aciduria is a rare metabolic disease, with 40 cases reported so far. Fumarase deficiency leads mainly to brain abnormalities, developmental delay, and great accumulation of fumaric acid in urine. This work presents the first case of fumaric aciduria described in Brazil, which presented with some interesting clinical and biochemical findings such as colpocephaly, hepatic alterations, and marked metabolic acidosis since birth. Common findings were ventriculomegaly, hypotonia, and microcephaly. Biochemically, besides the high urinary fumaric acid excretion, atypical elevation of plasma citrulline, tyrosine and methionine levels were also observed. In order to show all features and variants of fumaric aciduria, literature data of 40 patients was reviewed and compared with the case reported here. Findings in all these patients demonstrate that this disorder does not yet have its phenotype completely defined; it is important that more patients be described.

Topics: Brazil; Family Health; Female; Fumarate Hydratase; Fumarates; Humans; Infant; Metabolism, Inborn Errors

The succinate dehydrogenase consists of only four subunits, all nuclearly encoded, and is part of both the respiratory chain and the Krebs cycle. Mutations in the four genes encoding the subunits of the mitochondrial respiratory chain succinate dehydrogenase have been recently reported in human and shown to be associated with a wide spectrum of clinical presentations. Although a comparatively rare deficiency in human, molecularly defined succinate dehydrogenase deficiency has already been found to cause encephalomyopathy in childhood, optic atrophy or tumor in adulthood. Because none of the typical housekeeping genes encoding this respiratory chain complex is known to present tissue-specific isoforms, the tissue-specific involvement represents a quite intriguing question, which is mostly addressed in this review. A differential impairment of electron flow through the respiratory chain, handling of oxygen, and/or metabolic blockade possibly associated with defects in the different subunits that can be advocated to account for tissue-specific involvement is discussed.

Topics: Citric Acid Cycle; Electron Transport Complex II; Flavoproteins; Fumarates; Humans; Metabolism, Inborn Errors; Mitochondrial Diseases; Models, Chemical; Multienzyme Complexes; Mutation; Oxidoreductases; Succinate Dehydrogenase; Succinic Acid

Topics: Citric Acid Cycle; Fumarate Hydratase; Fumarates; Humans; Isoenzymes; Maleates; Metabolism, Inborn Errors; Mitochondria; Substrate Specificity

Topics: Atrophy; Biomarkers; Brain; Cytoplasm; Diagnosis, Differential; Fumarate Hydratase; Fumarates; Humans; Metabolism, Inborn Errors; Mitochondria; Mutation; Prognosis

The tricarboxylic acid (TCA) cycle is a central metabolic hub in most cells. Virulence functions of bacterial pathogens such as facultative intracellular

Topics: Carbon; Citric Acid Cycle; Fumarate Hydratase; Fumarates; Glycolysis; Host-Pathogen Interactions; Locomotion; Macrophages; Metabolic Flux Analysis; Metabolism, Inborn Errors; Metabolome; Muscle Hypotonia; Pentose Phosphate Pathway; Phagocytosis; Proteome; Psychomotor Disorders; Salmonella typhimurium; Virulence

In this issue of Cell Chemical Biology, Ruecker et al. (2017) show that fumarase depletion in Mycobacterium tuberculosis leads to fumarate, a TCA cycle intermediate, accumulation, causing succination of a range of thiol-containing metabolites and proteins. Fumarate is bactericidal to the pathogen, and its accumulation may enhance the bactericidal effector mechanisms of other TCA cycle intermediates that accumulate due to activation of infected macrophages.

Topics: Fumarate Hydratase; Fumarates; Metabolism, Inborn Errors; Muscle Hypotonia; Mycobacterium tuberculosis; Oxidation-Reduction; Psychomotor Disorders

Methylmalonic aciduria (MMA) is a common inherited autosomal recessive disorder resulting from defects in the enzyme methylmalonyl CoA mutase (MCM, mut complementation group) or in the synthesis of the MCM cofactor adenosylcobalamin (cbl complementation groups). The defects in the mut complementation group accounts for the largest number of patients with isolated MMA. At least 200 mutations in the MUT gene on chromosome 6p12 have been identified in MMA patients until now. This study aimed to investigate the clinical characteristics of MMA and genomic variations in the MUT gene of Chinese patients. Genomic DNA was extracted from 18 patients who were diagnosed as having isolated MMA by gas chromatography/mass spectrometry (GC-MS), and from some of their parents as well. Amplification and direct sequencing of the MUT coding regions (exon 2-13) and their adjacent intronic consensus splice sites were performed in order to identify the disease causing mutations. In this group, six novel mutations in the MUT gene, c.424A>G (p.T142A), c.786T>G (p.S262R), c.808G>C (p.G270R), c.1323_1324insA, c.1445-1G>A and c.1676+77A>C were identified. p.T142A and p.G270R were respectively detected at a heterozygous level in one patient. Two previously reported mutations, c.682C>T (p.R228X) and c.323G>A (p.R108H) were also found in this study. In addition, six previously described single nucleotide polymorphism (SNP), c.636A>G (p.K212K), c.1495G>A (p.A499T), c.1595A>G (p.H532R), c.1992G>A (p.A664A), c.2011G>A (p.V671I) and c.1677-53A>G were identified. In this study, we updated the spectrum of MUT mutations and identified the main MMA-causing mutations in Chinese MMA patients.

Topics: Asian People; Base Sequence; Child, Preschool; DNA Mutational Analysis; Female; Fumarates; Genotype; Humans; Infant; Infant, Newborn; Male; Maleates; Metabolism, Inborn Errors; Methylmalonyl-CoA Mutase; Molecular Sequence Data; Mutation; Polymorphism, Genetic

Fumarase (FH) deficiency is a rare autosomal recessive disease of the Krebs cycle causing severe neurological impairment in early childhood, characterized by encephalopathy with seizures and muscular hypotonia. Only a handful of patients with various recessive mutations in the FH gene have been described so far. Interestingly, autosomal dominant mutations in the same gene are associated with hereditary leiomyomatosis and renal cell cancer (HLRCC). We investigated a boy with developmental and growth delay, microcephaly, and muscular hypotonia recognized at the age of 3 months. No leiomyomatosis or renal cancer is known in the parents. Investigation of the patient's urine revealed massive fumarate excretion. FH activity was severely reduced in muscle and fibroblasts. Respirometric investigation of fibroblasts showed only modest changes indicating that fumarate mediated inhibition of enzymatic pathways other than oxidative phosphorylation might be more relevant in pathophysiology of FH deficiency. Molecular analysis revealed a known 435insK mutation on the paternal allele and a novel H275L mutation due to an A to T transversion of nucleotide 824 on the maternal allele. This mutation affects the same codon as a C to T transition of nucleotide 823, resulting in a H275Y mutation that was found in two families with HLRCC.

Topics: Amino Acid Substitution; Cell Respiration; Child, Preschool; Fatal Outcome; Fumarate Hydratase; Fumarates; Heterozygote; Humans; Infant; Infant, Newborn; Lysine; Male; Metabolism, Inborn Errors; Mitochondria; Models, Molecular; Muscle Hypotonia; Muscle, Skeletal; Mutation; Psychomotor Disorders

The patients affected by vitamin B12-unresponsive methylmalonic acidemia (MMA) on the long run develop chronic renal disease with interstitial nephropathy and progressive renal insufficiency. The mechanism of nephrotoxicity in vitamin B12-unresponsive MMA is not yet known. Chronic hyporeninemic hypoaldosteronism has been found in many cases of methylmalonic acidemia, hyperkalemia and renal tubular acidosis type 4. We report 2 patients affected by B12-unresponsive methylmalonic acidemia diagnosed at the age of 23 months and 5 years, respectively, with normal glomerular filtration and function. They showed hyporeninemic hypoaldosteronism and significant hyperkalemia requiring sodium potassium exchange resin (Kayexalate) therapy after an episode of metabolic decompensation leading to diagnosis of MMA. In both children, hyporeninemic hypoaldosteronism and hyperkalemia disappeared after 6 months of good metabolic control.

Topics: Child, Preschool; Female; Fumarates; Humans; Hyperkalemia; Hypoaldosteronism; Infant; Kidney; Male; Maleates; Metabolism, Inborn Errors; Vitamin B 12

A fumarase-deficient patient expressed a novel phenotype of congenital cerebral ventricular dilatation and periventricular cysts. The patient was a compound heterozygote for two mutations that are the only ones among the 12 published mutations that have been found in multiple, unrelated, fumarase-deficient patients.

Topics: Brain; Cysts; DNA Mutational Analysis; DNA, Complementary; Electroencephalography; Fatal Outcome; Female; Fumarate Hydratase; Fumarates; Heterozygote; Histidine; Humans; Infant, Newborn; Ketoglutaric Acids; Leukomalacia, Periventricular; Lysine; Metabolism, Inborn Errors; Methylmalonic Acid; Mutation; Phenotype; Pyruvic Acid; Ultrasonography

A gas chromatography tandem mass spectrometry method using an ion trap GC/MS system was developed to quickly screen urine samples for 14 organic acids associated with multiple organic acidemias. The following organic acids are used as diagnostic markers: methylmalonic acid, glutaric acid, 2-ketoisocaproic acid, succinylacetone, 3-methylcrotonylglycine, tiglylglycine, isovalerylglycine, fumaric acid, butyrylglycine, propionylglycine, hexanoylglycine, adipic acid, suberic acid, and sebacic acid. 2-ketocaproic acid is used as an internal standard. The samples are prepared using a solid-phase extraction and converted to trimethylsilyl derivatives. The extraction efficiency for the 14 compounds is between 57 and 106%. A derivatized standard mixture of the 14 markers is run prior to the patient samples to determine the accurate absolute and relative retention times. The samples are then injected and the product ion spectra monitored. For data analysis, one characteristic product ion plot is extracted for each of the 14 marker compounds, and the presence of a peak with the expected retention time is determined. The areas of the product ion peaks are compared with the reference range determined from 30 normal controls. Ten samples of patients with known organic acidemias were measured. For all patients, diagnostic peaks at the expected retention times of at least five times the upper limit of the reference range were detected. The method, with its relatively fast sample preparation, short 10.0 min run time and simple data analysis, is suitable for use as a quick metabolic screen of very sick patients in whom there is concern regarding the possibility of a treatable inborn error.

Topics: Acids; Adipates; Automation; Biomarkers; Caprylates; Decanoic Acids; Dicarboxylic Acids; Fumarates; Gas Chromatography-Mass Spectrometry; Glutarates; Humans; Keto Acids; Mass Screening; Metabolism, Inborn Errors; Methylmalonic Acid; Reference Values; Sensitivity and Specificity; Urinalysis

A 5-year-old girl with a previous diagnosis of cerebral palsy, nonprogressive psychomotor retardation, and hypotonia was found to excrete excessive fumaric acid in urine. Fumarate hydratase activity in skin fibroblasts was 10% of the control value. This case underscores the clinical heterogeneity of neurometabolic disorders and the importance of organic acid analysis in the diagnosis of static encephalopathy.

Topics: Cerebral Palsy; Child, Preschool; Diagnostic Errors; Female; Fumarate Hydratase; Fumarates; Humans; Intellectual Disability; Metabolism, Inborn Errors; Muscle Hypotonia; Succinates; Succinic Acid