Biochemistry of Alzheimer's dementia.
Explore the source record for details and available documents.
Acetylcholine↗
SEARCH · Search PubMed
Results for “Pyruvate Dehydrogenase Complex Deficiency Disease”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
An amino acid substitution in the pyruvate dehydrogenase E1 alpha gene, affecting mitochondrial import of the precursor protein.
A mutation in the mitochondrial targeting sequence was characterized in a male patient with X chromosome-linked pyruvate dehydrogenase E1 alpha deficiency. The mutation was a base substitution of G by C at nucleotide 134 in the mitochondrial targeting sequence of the PDHA1 gene, resulting in an arginine-to-proline substitution at codon 10 (R10P). Pyruvate dehydrogenase activity in cultured skin fibroblasts was 28% of the control value, and immunoblot analysis revealed a decreased level of pyruvate dehydrogenase E1 alpha immunoreactivity. Chimeric constructs in which the normal and mutant pyruvate dehydrogenase E1 alpha targeting sequences were attached to the mitochondrial matrix protein ornithine transcarbamylase were synthesized in a cell free translation system, and mitochondrial import of normal and mutant proteins was compared in vitro. The results show that ornithine transcarbamylase targeted by the mutant pyruvate dehydrogenase E1 alpha sequence was translocated into the mitochondrial matrix at a reduced rate, suggesting that defective import is responsible for the reduced pyruvate dehydrogenase level in mitochondria. The mutation was also present in an affected brother and the mildly affected mother. The clinical presentations of this X chromosome-linked disorder in affected family members are discussed. To our knowledge, this is the first report of an amino acid substitution in a mitochondrial targeting sequence resulting in a human genetic disease.
Amino Acids↗
Thiamine dependency in a patient with congenital lacticacidaemia due to pyruvate dehydrogenase deficiency.
A patient with congenital lactic acidosis, muscular hypotonia and severe ataxia is reported. The aetiology of his disease was found to be a deficiency of pyruvate dehydrogenase (E.C. 4.1.1.1.). Thiamine treatment (1.8 g/day) was successful in correcting biochemical and clinical symptoms. The mechanism of its action is probably based on activation of pyruvate dehydrogenase through interference in the physiologic regulation.
Alanine↗
[Respiratory chain and pyruvate metabolism deficiencies in pediatric patients: evaluation of biochemical tests for selective screening].
INTRODUCTION: The correct selection of pediatric patients with clinical suspicion of mitochondrial diseases is the first step to achieve a definitive diagnosis. MATERIAL AND METHODS: The results of the initial biochemical tests obtained in 35 children diagnosed of respiratory chain or pyruvate metabolism defects were reviewed. The efficiency of basal determinations (lactate, pyruvate, ketone bodies, amino and organic acids and carnitine), cerebrospinal fluid (CSF) analysis, and dynamic tests (exercise, glucose loading and glucose oxidation by lymphocytes) was discussed. RESULTS: Plasma lactate and alanine, and CSF metabolites were the most informative measurements in basal status. Urine organic acids were very useful to confirm the initial suspicion. Glucose loading was the most informative and reliable challenge test for pediatric population, while exercise test was especially useful for older children with fatigability or peripheral nervous system involvement. CONCLUSIONS: Glucose oxidation by lymphocytes might be applied when the other dynamic tests can not be performed or are not informative.
Alanine↗
[Diagnostic strategy for mitochondrial diseases].
OBJECTIVE: The variability of both phenotypic and genotypic expression in mitochondrial diseases makes clinical diagnosis difficult, which is essential to establish therapy, aid in genetic counselling or for performing prenatal diagnosis. We have therefore proposed a strategy to help determine correct diagnosis of these alterations, in an attempt to rationalize the number of tests and, whenever possible, avoid tissue biopsy and minimize the size of the biopsy when indicated. DEVELOPMENT: Based on mitochondrial metabolism and molecular bases, as well as their alterations, a preliminary metabolic examination is carried out including at least one study of cytoplasmatic (lactate/pyruvate) and mitochondrial oxide reduction (hydroxibutirate/acetoacetate) in basal conditions or, if required, following glucose overload or an effort test. Metabolic study, in addition to clinical exploration, are the screening tests used to determine the need for tissue biopsy in which biochemical (pyruvate dehydrogenase, free and total carnitine, beta oxidation enzymes and respiratory chain complexes), genetic (mitochondrial DNA or nuclear alterations) and histologic tests are carried out to confirm diagnosis. CONCLUSIONS: a) Metabolic exploration may discard mitochondrial disease and many cases, avoid the use of an invasive procedure such as tissue biopsy. b) Biochemical study of tissue biopsy is the only useful key in the confirming of the diagnosis when no mitochondrial and/or nuclear DNA are observed.
Biopsy↗
Cell culture studies on patients with mitochondrial diseases: molecular defects in pyruvate dehydrogenase.
There is a group of inborn errors of metabolism that result in the condition of chronic lacticacidemia of childhood. Nearly all of the defects that can be identified occur in mitochondrial proteins, and can be demonstrated in cultured skin fibroblasts from the patients concerned. One approach to the diagnosis of these defects involves a simple incubation of the fibroblast culture with glucose-containing medium followed by the measurement of accumulated lactate and pyruvate. The total amounts of lactate and pyruvate and the ratio between them is different in cells from patients with defects in the pyruvate dehydrogenase complex or the respiratory chain. Measurement of 1-14C-pyruvate oxidation to 14CO2 can also reveal defective oxidative metabolism. Localization of the defects can be achieved using individual assays for the enzymes concerned. The clinical sequelae of the different defects is discussed.
Cells, Cultured↗
Inherited metabolic diseases and pathogenesis of mental retardation.
Continuing progress has been made in the exploration of the biochemical causes of mental illness. Recent research has indicated that selected abnormalities of specific isoenzymes play an important role in the pathogenesis of heritable metabolic disorders such as phenylketonuria and Niemann-Pick disease. The roles of "animal lectins" and glycosidic enzymes in brain development and synaptogenesis appear to have received important substantiation within the past year. In additions, it has been shown that the blood-brain barrier can be temporarily altered so that exogenous enzymes can enter the central nervous system, and imperative consideration for enzyme replacement therapy in mental disorders. Less satisfactory progress has been made concerining potential anabolic disorders of lipids affecting the nervous system. Finally, novel experimental directions concerning energy metabolism by the brain offer considerable hope for the elucidation of some of the causes of mental retardation.
Amino Acid Metabolism, Inborn Errors↗
Nuclear complementation restores mtDNA levels in cultured cells from a patient with mtDNA depletion.
We have studied cultured skin fibroblasts from a patient with a fatal mitochondrial disease manifesting soon after birth. These fibroblasts were found to grow only in the presence of pyruvate and uridine, a characteristic of cells lacking mtDNA (rho0 cells). Southern blot and PCR analyses confirmed that the patient's fibroblasts contained less than 2% of control levels of mtDNA. Biochemical analyses indicated that the activities of all the respiratory-chain enzymes were severely decreased in mitochondria isolated from these fibroblasts. In order to elucidate the underlying molecular defect, cell fusions were performed between enucleated fibroblasts from this patient and a human-derived rho0 cell line (rho0 A549.B2). The resulting cybrids were plated in medium lacking pyruvate and uridine, to select for the restoration of respiratory-chain function. Complementation was observed between the nuclear genome of the rho0 A549.B2 cells and the mtDNA of the patient's cells, restoring mtDNA levels and respiratory-chain function in the cybrid cells. These results indicate that mtDNA depletion in our patient is under the control of the nuclear genome.
Cell Fusion↗
Mechanisms of expression of pyruvate dehydrogenase deficiency caused by an E1alpha subunit mutation.
OBJECTIVE: To characterize the biochemical mechanisms of expression of the pyruvate dehydrogenase (PDH) E1alpha subunit exon 10 R302C missense mutation. BACKGROUND: Mutations in the X-linked E1alpha subunit gene are responsible for most cases of PDH deficiency, an important cause of neurodevelopmental defects and neurodegeneration with primary lactic acidemia. Although the disease shows extreme allelic heterogeneity, the R302C mutation has been defined in several unrelated cases. METHODS: Cell lines expressing selectively either the mutant or wild-type E1alpha alleles against identical genetic backgrounds were generated from the fibroblasts of a female heterozygous for the R302C mutation. Enzyme activity, mRNA, polypeptide expression, and turnover were studied in each. RESULTS: The residual PDH activity was below measurable levels in the cell line (B5) expressing only the mutant allele and normal in the wild-type polypeptide expressing (A10) cell line, confirming that the R302C mutation alone is sufficient to cause a severe PDH deficiency. The mutant polypeptide was less stable than the wild-type polypeptide, but the steady-state level of the mutant E1alpha protein was reduced only two- to threefold. CONCLUSIONS: The primary mechanism of expression of the R302C mutation must be limitation of catalytic efficiency. We speculate that catalysis may be inhibited in the mutant polypeptide because conformational changes are induced near serine 300, a residue that is particularly important as a regulatory phosphorylation site in the wild-type polypeptide.
Base Sequence↗
Mutation analysis of the pyruvate dehydrogenase E1 alpha gene in eight patients with a pyruvate dehydrogenase complex deficiency.
Most of the mutations causing deficiency of the pyruvate dehydrogenase (PDH) complex are in the X-linked E1 alpha gene. We have developed a rapid screening method for the detection of mutations in this gene using reverse transcription of total RNA, polymerase chain reaction amplification of the whole coding region of the gene and single-strand conformation polymorphism (SSCP) analysis. With this method, we studied eight patients with a PDH complex deficiency, using cultured fibroblasts. In all patients, aberrant SSCP patterns were found and, after sequencing of the corresponding fragments, we were able to identify six new mutations and two mutations already described previously. The mutations are point mutations leading to amino acid substitutions (5) and direct repeat insertions (3). The presence of the mutations was confirmed in genomic fibroblast DNA. The 4 female patients were shown to carry both a normal and a mutated E1 alpha gene.
Base Sequence↗
Sensitive and fast mutation detection by solid phase chemical cleavage.
We have developed a solid phase chemical cleavage method (SpCCM) for screening large DNA fragments for mutations. All reactions can be carried out in microtiterwells from the first amplification of the patient (or test) DNA through the search for mutations. The reaction time is significantly reduced compared to the conventional chemical cleavage method (CCM), and even by using a uniformly labelled probe, the exact position and nature of the mutation can be revealed. The SpCCM is suitable for automatization using a workstation to carry out the reactions and a fluorescent detection-based DNA sequencing system to analyze the cleaved fragments.
Bacterial Proteins↗
Arginine 302 mutations in the pyruvate dehydrogenase E1alpha subunit gene: identification of further patients and in vitro demonstration of pathogenicity.
Three further patients with mutations in the codon for arginine 302 of the E1alpha subunit of the pyruvate dehydrogenase complex have been identified. Mutations in this codon have now been found in nine patients with pyruvate dehydrogenase deficiency in seven unrelated families, in sharp contrast to the great majority of other PDH E1alpha mutations which have been described in single individuals only. Because of the relatively high frequency of this mutation and because very few PDH E1alpha mutations have been demonstrated to be causative, we have established a system for analysing the consequences of defined mutations using transfection of normal and mutant PDH E1alpha cDNA into transformed human fibroblasts which have no endogenous E1alpha mRNA or protein. Using this test system, we have demonstrated that the R302C mutation results in the production of PDH E1alpha protein which is devoid of enzymic activity.
Arginine↗
Deficiency of pyruvate dehydrogenase caused by novel and known mutations in the E1alpha subunit.
Pyruvate dehydrogenase (PDH)-complex deficiency (OMIM 312170) is a clinically heterogeneous disorder, with phenotypes ranging from fatal lactic acidosis (LA) in the newborn to chronic neurological dysfunction. To date, over 80 different mutations have been identified in the PDHA1 gene in patients with PDH complex deficiency, which are thus thought to contribute to the PDH deficient phenotype. We have identified 14 additional patients with total PDH complex deficiency, all of whom were found to contain mutations within the PDHA1 gene (E(1)alpha subunit). The mutations include both missense mutations and duplications. Eight of these patients had novel mutations, and the remaining had mutations that have been identified previously in PDH complex deficient patients, with residual fibroblast activity ranging from 2.4 to 69% of control values. The nature of these mutations illustrates the variability in phenotype for a given gene defect, with intermittent ataxia being the mildest presentation, Leigh syndrome being the most common and severe neonatal LA the most severe.
Adult↗
Clinical and genetic spectrum of pyruvate dehydrogenase deficiency: dihydrolipoamide acetyltransferase (E2) deficiency.
Pyruvate dehydrogenase deficiency is a major cause of primary lactic acidosis and neurological dysfunction in infancy and early childhood. Most cases are caused by mutations in the X-linked gene for the E1alpha subunit of the complex. Mutations in DLAT, the gene encoding dihydrolipoamide acetyltransferase, the E2 core component of the complex, have not been described previously. We report two unrelated patients with pyruvate dehydrogenase deficiency caused by defects in the E2 subunit. Both patients are less severely affected than typical patients with E1alpha mutations and both have survived well into childhood. Episodic dystonia was the major neurological manifestation, with other more common features of pyruvate dehydrogenase deficiency, such as hypotonia and ataxia, being less prominent. The patients had neuroradiological evidence of discrete lesions restricted to the globus pallidus, and both are homozygous for different mutations in the DLAT gene. The clinical presentation and neuroradiological findings are not typical of pyruvate dehydrogenase deficiency and extend the clinical and mutational spectrum of this condition.
Autoantigens↗
Pyruvate dehydrogenase deficiency: molecular basis for intrafamilial heterogeneity.
Two half-brothers and their mother had symptomatic pyruvate dehydrogenase complex deficiency. The infants had severe congenital lactic acidosis, seizures, and apneic spells and died at the ages 3 and 4 months. The mother was less symptomatic with mental retardation, truncal ataxia, and dysarthria. The residual pyruvate dehydrogenase activities in cultured skin fibroblasts from the 2 infants and their mother were 7, 15, and 10% of control values. Immunoblot analysis showed negligible amounts of E1 alpha and E1 beta subunits of the complex. Northern blot analysis for the E1 alpha subunit showed normal results. In the 2 sons, complementary DNA sequence analysis revealed a cytosine to thymine mutation in exon 4, resulting in a change of arginine 127 to tryptophan in the E1 alpha subunit. Restriction enzyme analysis of the polymerase chain reaction product representing exon 4 of the E1 alpha gene revealed that the mother was a heterozygotes. Complementary DNA restriction analysis and methylation analysis of the X chromosome DXS255 loci revealed skewed activation of the mutant allele, consistent with the deficient pyruvate dehydrogenase activity in the mother's fibroblasts. The milder maternal phenotype is consistent with variable X-inactivation patterns in different organs of female heterozygotes.
Base Sequence↗
Mutations and polymorphisms in the pyruvate dehydrogenase E1 alpha gene.
We present an update on mutations and polymorphisms in the human X chromosome located pyruvate dehydrogenase E1 alpha gene. A total of 20 different mutations are tabulated. The mutations include deletions, insertions, and point mutations. Certain sequences seem particularly prone to mutation. Most of the mutations are found in exons 10 and 11. Furthermore, four of the mutations are seen in unrelated patients. Little is known about how the mutations affect the structure or function of the pyruvate dehydrogenase complex.
Amino Acid Sequence↗
Pyruvate dehydrogenase deficiency in a male caused by a point mutation (F205L) in the E1 alpha subunit.
Explore the source record for details and available documents.
Amino Acid Sequence↗
A novel mutation (P316L) in a female with pyruvate dehydrogenase E1 alpha deficiency.
Explore the source record for details and available documents.
Female↗