Multiple sources of metabolic disturbance in ETHE1-related ethylmalonic encephalopathy (original) (raw)
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Metabolism, 1998
Ethylmalonic encephalopathy (EE), an organic aciduria of unknown etiology characterized by developmental delay, hypotonia, and vascular instability associated with lactic acidemia and urinary excretion of ethylmalonic acid (EMA) and methylsuccinic acid (MSA), has been described in 11 patients. To test the possibility that the underlying biochemical defect involves isoleucine catabolism, we determined the response to oral L-isoleucine (IIe) load (150 mg/kg) in a 5-year-old girl with EE and in three healthy, age- and sex-matched controls. Following IIe load in the patient, there was accumulation of 2-methylbutyrylglycine (2-MBG) and a delayed and lower peak urinary excretion of tiglylglycine (TGL), suggesting a partial defect in 2-methyl-branched chain acylcoenzyme A dehydrogenase (2M-BCAD). In vitro measurements 2M-BCAD activity in cultured skin fibroblasts from patients with EE have been reported to be normal. Our results show that isoleucine is a source for the elevated EMA and MSA in patients with EE, and suggest a functional, possibly secondary, deficiency of activity of 2M-BCAD in vivo.
Siblings with Ethylmalonic Encephalopathy: Case Report
The Journal of Pediatric Research
Deficiency of mitochondrial sulfur dioxygenase (ETHE1) causes a rare inborn error of metabolism, ethylmalonic encephalopathy, which is characterized by early-onset encephalopathy, chronic hemorrhagic diarrhea, recurrent petechiae, orthostatic acrocyanosis, defective cytochrome C oxidase because of hydrogen sulfide accumulation and death in the first years of life. Biochemical hallmarks of the disease are high level of lactate, C4-C5-acylcarnitines in blood and markedly elevated urinary excretion of methylsuccinic and ethylmalonic acids. We report on two siblings who were admitted to a pediatric metabolic unit with acrocyanosis, chronic diarrhea and psychomotor retardation later diagnosed as ethylmalonic encephalopathy. Molecular analyses revealed a homozygous for p.R163Q (c.488 G>A) mutation in ETHE1 gene.
Neurological and Vascular Manifestations of Ethylmalonic Encephalopathy
Iranian Journal of Child Neurology, 2017
Objective Ethylmalonic encephalopathy (EE) is a severe mitochondrial disease of early infancy clinically characterized by a combination of developmental delay, progressive pyramidal signs, and vascular lesions including petechial purpura, orthostatic acrocyanosis, and chronic hemorrhagic diarrhea. Biochemical hallmarks of the disease are persistently high level of lactate, and C4–C5-acylcarnitines in blood, markedly elevated urinary excretion of methylsuccinic and ethylmalonic (EMA) acids. Here we report two patients with EE as a 16-months-old male infant and a 2-yr-old boy referred to Pediatric Neurology Clinic in Children’s Medical Center, Tehran-Iran that in one patient genetic analysis revealed a homozygous mutation of the ETHE1 gene in favor of ethylmalonic acidemia.
Objective Ethylmalonic encephalopathy (EE) is a severe mitochondrial disease of early infancy clinically characterized by a combination of developmental delay, progressive pyramidal signs, and vascular lesions including petechial purpura, orthostatic acrocyanosis, and chronic hemorrhagic diarrhea. Biochemical hallmarks of the disease are persistently high level of lactate, and C4–C5-acylcarnitines in blood, markedly elevated urinary excretion of methylsuccinic and ethylmalonic (EMA) acids. Here we report two patients with EE as a 16-months-old male infant and a 2-yr-old boy referred to Pediatric Neurology Clinic in Children's Medical Center, Tehran-Iran that in one patient genetic analysis revealed a homozygous mutation of the ETHE1 gene in favor of ethylmalonic acidemia.
Nature Medicine, 2009
Ethylmalonic encephalopathy is an autosomal recessive, invariably fatal disorder characterized by early-onset encephalopathy, microangiopathy, chronic diarrhea, defective cytochrome c oxidase (COX) in muscle and brain, high concentrations of C4 and C5 acylcarnitines in blood and high excretion of ethylmalonic acid in urine. ETHE1, a gene encoding a b-lactamase-like, iron-coordinating metalloprotein, is mutated in ethylmalonic encephalopathy. In bacteria, ETHE1-like sequences are in the same operon of, or fused with, orthologs of TST, the gene encoding rhodanese, a sulfurtransferase. In eukaryotes, both ETHE1 and rhodanese are located within the mitochondrial matrix. We created a Ethe1 -/mouse that showed the cardinal features of ethylmalonic encephalopathy. We found that thiosulfate was excreted in massive amounts in urine of both Ethe1 -/mice and humans with ethylmalonic encephalopathy. High thiosulfate and sulfide concentrations were present in Ethe1 -/mouse tissues. Sulfide is a powerful inhibitor of COX and short-chain fatty acid oxidation, with vasoactive and vasotoxic effects that explain the microangiopathy in ethylmalonic encephalopathy patients. Sulfide is detoxified by a mitochondrial pathway that includes a sulfur dioxygenase. Sulfur dioxygenase activity was absent in Ethe1 -/mice, whereas it was markedly increased by ETHE1 overexpression in HeLa cells and Escherichia coli. Therefore, ETHE1 is a mitochondrial sulfur dioxygenase involved in catabolism of sulfide that accumulates to toxic levels in ethylmalonic encephalopathy.
Brain Research, 2009
Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is an inherited metabolic disorder of fatty acid oxidation in which the affected patients predominantly present high levels of octanoic (OA) and decanoic (DA) acids and their glycine and carnitine by-products in tissues and body fluids. It is clinically characterized by episodic encephalopathic crises with coma and seizures, as well as by progressive neurological involvement, whose pathophysiology is poorly known. In the present work, we investigated the in vitro effects of OA and DA on various parameters of energy homeostasis in mitochondrial preparations from brain of young rats. We found that OA and DA markedly increased state 4 respiration and diminished state 3 respiration as well as the respiratory control ratio, the mitochondrial membrane potential and the matrix NAD(P)H levels. In addition, DA-elicited increase in oxygen consumption in state 4 respiration was partially prevented by atractyloside, indicating the involvement of the adenine nucleotide translocator. OA and DA also reduced ADP/O ratio, CCCP-stimulated respiration and the activities of respiratory chain complexes. The data indicate that the major accumulating fatty acids in MCADD act as uncouplers of oxidative phosphorylation and as metabolic inhibitors. Furthermore, DA, but not OA, provoked a marked mitochondrial swelling and cytochrome c release from mitochondria, reflecting a permeabilization of the inner mitochondrial membrane. Taken Keywords: MCAD deficiency Octanoic acid Decanoic acid Mitochondrial function Rat brain B R A I N R E S E A R C H 1 2 9 6 ( 2 0 0 9 ) 1 1 7 -1 2 6 acid]; MCAD, medium-chain acyl-CoA dehydrogenase; MCADD, medium-chain acyl-CoA dehydrogenase deficiency; MCFA, medium-chain fatty acids; MOPS, 3-[N-morpholino]propanesulfonic acid; OA, octanoic acid; RCR, respiratory control ratio; ΔΨm, mitochondrial membrane potential 0006-8993/$see front matter a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m w w w . e l s e v i e r . c o m / l o c a t e / b r a i n r e s
Effect of In Vivo Administration of Ethylmalonic Acid on Energy Metabolism in Rat Tissues
Metabolic Brain Disease, 2006
High concentrations of ethylmalonic acid (EMA) occur in tissues and biological fluids of patients affected by deficiency of short-chain acyl-CoA dehydrogenase activity, as well as in other illnesses characterized by neurological and muscular symptoms. Considering that the pathophysiological mechanisms responsible for the clinical manifestations of these diseases are virtually unknown, in the present work we developed a chemical in vivo model of ethylmalonic acidemia in young Wistar rats for neurochemical and behavioral studies through subcutaneous administration of EMA to young rats. The doses of EMA administered subcutaneously varied according to the age of the animals, being injected 3, 4, and 6 µmol g −1 of body weight in rats of 7, 14, and 21 days, respectively. The concentrations of the acid were measured in blood and brain at regular intervals after a single injection (30-120 min) and reached the highest concentrations (3.0 mM and 0.5 µmol g −1 , ∼0.5 mM), respectively, after 30 and 60 min of EMA injection. Next, we investigated the effects of acute EMA administration on the activities of complexes I-III, II, II-III, and IV of the respiratory chain in cerebral cortex and skeletal muscle, as well as on the activity of creatine kinase in cerebral cortex, striatum, skeletal muscle, and cardiac muscle of rats of 14 days of life. Control rats were treated with saline in the same volumes. We verified EMA administration did not change these enzymatic activities in all tissues studied. Although transient high concentrations of
The American Journal of Human Genetics, 2011
Lipoic acid is an essential prosthetic group of four mitochondrial enzymes involved in the oxidative decarboxylation of pyruvate, a-ketoglutarate, and branched chain amino acids and in the glycine cleavage. Lipoic acid is synthesized stepwise within mitochondria through a process that includes lipoic acid synthetase. We identified the homozygous mutation c.746G>A (p.Arg249His) in LIAS in an individual with neonatal-onset epilepsy, muscular hypotonia, lactic acidosis, and elevated glycine concentration in plasma and urine. Investigation of the mitochondrial energy metabolism showed reduced oxidation of pyruvate and decreased pyruvate dehydrogenase complex activity. A pronounced reduction of the prosthetic group lipoamide was found in lipoylated proteins.
American Journal of Human Genetics, 2004
Ethylmalonic encephalopathy (EE) is a devastating infantile metabolic disorder affecting the brain, gastrointestinal tract, and peripheral vessels. High levels of ethylmalonic acid are detected in the body fluids, and cytochrome c oxidase activity is decreased in skeletal muscle. By use of a combination of homozygosity mapping, integration of physical and functional genomic data sets, and mutational screening, we identified GenBank D83198 as the gene responsible for EE. We also demonstrated that the D83198 protein product is targeted to mitochondria and internalized into the matrix after energy-dependent cleavage of a short leader peptide. The gene had previously been known as "HSCO" (for hepatoma subtracted clone one). However, given its role in EE, the name of the gene has been changed to "ETHE1." The severe consequences of its malfunctioning indicate an important role of the ETHE1 gene product in mitochondrial homeostasis and energy metabolism.