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I Yokota

Publications and source records attributed to I Yokota.

At least 37 records · Page 2Linked to original sources
PubMed1997

Biochemical and molecular analysis of an X-linked case of Leigh syndrome associated with thiamin-responsive pyruvate dehydrogenase deficiency.

We report molecular analysis of thiamin-responsive pyruvate dehydrogenase complex (PDHC) deficiency in a patient with an X-linked form of Leigh syndrome. PDHC activity in cultured lymphoblastoid cells of this patient and his asymptomatic mother were normal in the presence of a high thiamin pyrophosphate (TPP) concentration (0.4 mmol/L). However, in the presence of a low concentration (1 x 10(-4) mmol/L) of TPP, the activity was significantly decreased, indicating that PDHC deficiency in this patient was due to decreased affinity of PDHC for TPP. The patient's older brother also was diagnosed as PDHC deficiency with Leigh syndrome, suggesting that PDHC deficiency in these two brothers was not a de novo mutation. Sequencing of the X-linked PDHC E1 alpha subunit revealed a C-->G point mutation at nucleotide 787, resulting in a substitution of glycine for arginine 263. Restriction enzyme analysis of the E1 alpha gene revealed that the mother was a heterozygote, indicating that thiamin-responsive PDHC deficiency associated with Leigh syndrome due to this mutation is transmitted by X-linked inheritance.

DNA↗
PubMed1997

The molecular basis of medium-chain acyl-CoA dehydrogenase (MCAD) deficiency in compound heterozygous patients: is there correlation between genotype and phenotype?

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most commonly recognized defect of mitochondrial beta-oxidation. It is potentially fatal, but shows a wide clinical spectrum. The aim of the present study was to investigate whether any correlation exists between MCAD genotype and disease phenotype. We determined the prevalence of the 14 known and seven previously unknown non-G985 mutations in 52 families with MCAD deficiency not caused by homozygosity for the prevalent G985 mutation. This showed that none of the non-G985 mutations are prevalent, and led to the identification of both disease-causing mutations in 14 families in whom both mutations had not previously been reported. We then evaluated the severity of the mutations identified in these 14 families. Using expression of mutant MCAD in Escherichia coli with or without co-overexpression of the molecular chaperonins GroESL we showed that five of the missense mutations affect the folding and/or stability of the protein, and that the residual enzyme activity of some of them could be modulated to a different extent depending on the amounts of available chaperonins. Thus, some of the missense mutations may result in relatively high levels of residual enzyme activity, whereas the mutations leading to premature stop codons will result in no residual enzyme activity. By correlating the observed types of mutations identified to the clinical/biochemical data in the 14 patients in whom we identified both disease-causing mutations, we show that a genotype/phenotype correlation in MCAD deficiency is not straightforward. Different mutations may contribute with different susceptibilities for disease precipitation, when the patient is subjected to metabolic stress, but other genetic and environmental factors may play an equally important role.

Acyl-CoA Dehydrogenase↗
PubMed1997

Serum leptin concentration in cord blood: relationship to birth weight and gender.

To investigate the effect of leptin on fetal growth, serum leptin concentrations in venous cord blood were measured in 82 newborns (male = 43, female = 39, gestational age 36-42 weeks, birth weight 2,306-4,128 g). Serum leptin concentrations in cord blood ranged from 2.0 to 84.5 ng/mL (mean 19.9 +/- 17.4 ng/mL). Serum leptin concentrations in males (mean 15.3 +/- 15.6 ng/mL, range 2.0 to 79.3 ng/mL) were significantly (P = 0.011) lower than those in females (mean 25.0 +/- 18.0 ng/mL, range 2.1 to 84.5 ng/mL). Serum leptin concentrations in cord blood were positively correlated with birth weight (r = 0.555, P <0.0001), birth weight SD (r = 0.540, P <0.0001), Kaup index (r = 0.505, P <0.0001) and body weight/body height (r = 0.560, P <0.0001). The serum concentrations of estradiol and testosterone did not differ between males and females and did not correlate with the leptin concentration. It is unlikely that the gender difference in fetal leptin levels is due either to body fat content or distribution or to reproductive hormone status, but may be attributed to genetic differences between males and females.

Birth Weight↗
PubMed1997

Comparison of energy metabolism in insulin-dependent and non-insulin-dependent diabetes mellitus.

To compare the metabolic consequences of insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM), glycemic control and energy metabolism were evaluated in 18 children displaying IDDM and 19 NIDDM adult patients. With rising concentrations of fasting blood glucose (FBG), hemoglobin A1C and free fatty acid, the percentage of the ratio of resting energy expenditure (REE) to predicted REE expressed as %REE increased and the respiratory quotient (RQ) decreased. The linear regression between RQ and FBG showed the same gradient in IDDM and NIDDM although the RQ in IDDM was always 0.07 lower than that in NIDDM given various FBG concentrations. Those patients whose RQ values were less than 0.7, indicating ketone body production, included 8 (44%) IDDM and 2 (11%) NIDDM patients. These results may explain the relatively greater manifestation of ketoacidosis in IDDM.

Adult↗
PubMed1997

Two siblings with vitamin B6-nonresponsive cystathionine beta-synthase deficiency and differing blood methionine levels during the neonatal period.

We present two siblings with vitamin B6-nonresponsive homocystinuria due to a deficiency of cystathionine beta-synthase who had different levels of methionine in the blood during the neonatal period, even though they had the same genetic defect. One of them was missed in the screening of newborns for homocystinuria. Special care should be taken in screening neonates for homocystinuria using the blood level of methionine.

Child↗
PubMed1996

Stable restoration of pyruvate dehydrogenase complex in E1-defective human lymphoblastoid cells: evidence that three C-terminal amino acids of E1 alpha are essential for the structural integrity of heterotetrameric E1.

In an attempt to restore pyruvate dehydrogenase complex (PDHC), expression vectors carrying wildtype E1 alpha cDNA (pRAWT) or 1162ins-mutant (pRA1162) were introduced into human lymphoblastoid cells which had a 4-bp insertion after nucleotide 1162 (1162ins) of E1 alpha cDNA, 28% of normal PDHC activity, and undetectable levels of both E1 alpha and E1 beta proteins. The amount of E1 alpha mRNA transcribed from the introduced cDNA was approximately 25 times greater than that transcribed from the endogenous gene. The PDHC activity of pRAWT-transformed cells increased to the normal level whereas this activity increased to 55% of the control in pRA1162-transformed cells. Mitochondria from pRAWT-transformed cells contained normal amounts of both the E1 alpha and the E1 beta subunits. These results suggest that the three C-terminal amino acids of E1 alpha, which were absent from 1162ins-mutant protein, may be important for the structural integrity of E1 and that a large amount of normal subunit, compared to the endogenous mutant enzyme, must be expressed to restore a multienzyme complex.

Cell Line↗
PubMed1996

[Defects of pyruvate metabolism in cultured lymphoblastoid cells of 20 patients with Leigh syndrome].

Lymphoblastoid cells are useful materials for the diagnosis and basic studies of many human genetic disorders. To elucidate the etiology of Leigh syndrome, biochemical analyses and mitochondrial DNA analyses were performed on cultured lymphoblastoid cells from 20 patients with the clinical characteristics of this disorder. In 9 of 20 cases, we were able to define the following defects. Eight patients had biochemical defects, including 3 with pyruvate dehydrogenase complex (PDHC), 3 with cytochrome c oxidase (complex IV), and 2 with NADH-cytochrome c reductase (complex I) deficiencies. Two of 3 patients with PDHC deficiency were diagnosed with thiamine-responsive PDHC deficiency. One patient had a point mutation (T-->G) of mitochondrial DNA at nucleotide position 8993. These results indicate that the underlying defects in Leigh syndrome are heterogeneous and cultured lymphoblastoid cells are very useful materials for diagnosis of the etiology of Leigh syndrome.

Biomarkers↗
PubMed1995

DNA diagnosis of pyruvate dehydrogenase deficiency in female patients with congenital lactic acidaemia.

The diagnosis of pyruvate dehydrogenase (PDH) E1 alpha deficiency, which is an X-linked inborn error of metabolism, is usually established by the measurement of PDH complex activity in cultured cells. However, heterozygous female patients with PDH E1 alpha deficiency may be misdiagnosed when the normal X chromosome is predominantly expressed in the cultured cells. Therefore, in female patients with convincing clinical presentations of PDH E1 alpha deficiency and the normal enzyme activity, the X-inactivation pattern should be analysed and the PDH E1 alpha gene screened for mutations. For this screening, we applied the method of single-strand conformational polymorphism (SSCP) and DNA sequencing and examined 11 female patients with congenital lactic acidaemia whose PDH complex activity was normal in cultured cells. In 2 of the 11 female patients, we found distinct pathogenic missense mutations in the PDH E1 alpha gene (G89S and G291R). Both affected patients showed a similar clinical presentation and had been diagnosed as West syndrome. In 3 of the 11 patients, we found a polymorphic base-pair substitution in exon 9 of the PDH E1 alpha gene which resulted in a changed amino acid residue (M282L). We conclude that PCR-SSCP analysis of the PDH E1 alpha gene, followed by DNA sequencing, is a useful method to screen for mutations of the PDH E1 alpha gene in female patients with congenital lactic acidaemia who have normal enzyme activities in available samples, normal ratio of lactate to pyruvate, and predominantly raised lactate concentration in cerebrospinal fluid.

Base Sequence↗
PubMed1995

Molecular genetic analysis of a female patient with pyruvate dehydrogenase deficiency: detection of a new mutation and differential expression of mutant gene product in cultured cells.

A new 18 bp insertion mutation in the gene for the alpha subunit of pyruvate dehydrogenase (E1 alpha) was found in a female patient with congenital lactic acidaemia. Cultured skin fibroblasts and Epstein-Barr virus-transformed lymphoblastoid cells from this patient showed decreased and normal pyruvate dehydrogenase complex (PDHC) activity, respectively. This 18 bp insertion was a de novo mutation, because it was not present in her parents. Although this female patient was heterozygous for the normal and the mutant alleles, 97% of cultured skin fibroblasts expressed the mutant allele, while 100% of cultured lymphoblastoid cells, 94% of peripheral blood lymphocytes and 98% of IL-2-activated T-cells expressed the normal allele. These results suggest that in this patient the X chromosome containing the normal allele was predominantly inactivated in fibroblasts and the X chromosome containing the mutant allele was predominantly inactivated in lymphocytes. The diagnosis of E1 alpha deficiency is usually established by measurement of PDHC activity and the level of immunoreactive proteins. However, these methods are not sufficient to diagnose the disorder in female patients with E1 alpha deficiency due to differential inactivation of the X chromosome. Therefore, it is necessary to develop a new method to firmly establish the diagnosis of E1 alpha deficiency.

Alleles↗
PubMed1994

Vitamin D-dependent rickets type II: regulation of human osteocalcin gene expression in cells with defective vitamin D receptors by 1,25-dihydroxyvitamin D-3, retinoic acid, and triiodothyronine.

The vitamin D receptor (VDR) is a nuclear transcription factor which binds to the vitamin D response element (VDRE) of the human osteocalcin gene and regulates its expression. Humans with VDR gene mutations, ever among those with the same point mutation in their VDR gene, demonstrate clinical heterogeneity. In addition, in some patients with these mutations, rickets has not recurred following cessation of therapy during follow-up ranging from 6 to 24 years. While important, it is likely that the VDR protein is not the sole factor in the development of rickets. To try to understand these clinical findings, the complex formed between the VDRE and one or more proteins in the nuclear extracts of cultured skin fibroblasts treated with 1,25-dihydroxyvitamin D-3 (1,25(OH)2D3), retinoic acid (RA), and/or triiodothyronine (T3) was investigated since such complexes are likely to precede the transcription of the VDR gene. Complex formation in the control cells with an intact VDR was increased by treatment with either 0.1 nM, 1 nM, 10 nM 1,25(OH)2D3, 100 nM RA, or 100 nM T3; however, combinations of these compounds did not produce an additive effect. In cells of affected patients, 1,25(OH)2D3, RA, or T3 increased complex formation, while no combination had an additive effect. These results indicate that 1,25(OH)2D3, RA, and T3 play a role in the regulation of bone remodeling through modulating the formation of protein complexes on the VDRE. Therefore, the clinical observations in patients with a VDR mutation might be explained at least in part by the overlapping control of osteocalcin expression by 1,25(OH)2D3, RA and T3.

Base Sequence↗
PubMed1994

Molecular analysis of abnormal pyruvate dehydrogenase in a patient with thiamine-responsive congenital lactic acidemia.

A patient who responded to thiamine therapy with reduction of lactate in the blood and cerebrospinal fluid and clinical improvement was studied. Cultured lymphoblastoid cells of this patient were found to show reduced activities of pyruvate dehydrogenase complex (PDHC) and pyruvate dehydrogenase, decreased affinity of PDHC for thiamine pyrophosphate, and defective activation of PDHC by pyruvate dehydrogenase phosphatase. PDHC deficiency in fibroblasts and biopsied muscle of this patient was also due to the decreased affinity of PDHC for thiamine pyrophosphate. A mutation in the E1 alpha subunit containing the thiamine binding site and serine phosphorylation site regulating the activation/inactivation of PDHC was characterized by the polymerase chain reaction and DNA sequencing. A single A-->G transition was identified at position 131, resulting in the substitution of Arg-44 for His-44. This mutation must be a de novo mutation because it was not found in either parent's genomic DNA. In this study, we have obtained the first evidence at the molecular level for a mutation of thiamine-responsive PDHC deficiency.

Acidosis, Lactic↗
PubMed1993

[Studies on the quality of enzyme preparations (XII)--lysozyme preparations].

This paper was described the results of the weight variation test and the assay for the potency of the commercially available lysozyme preparations (samples: 13 kinds of granules, in which 10 kinds are granules (folded)) collected for the legal sampling inspection in 1992. The potencies of 10 samples were found to be within the range of permissible content, when the all samples extracted with phosphate buffer were determined by the method described in Japanese Standards of Pharmaceutical Ingredients. However, the potencies of 3 samples were not more than 65% of the labeled potencies. These low potency samples showed the potencies of 98-106%, when 0.4M sodium chloride solution or 0.1N hydrochloric acid was used instead of phosphate buffer for enzyme extraction. The weight variation test showed all preparations to be within the permissible JP XII deviation range (10%) for "granules (folded)".

Dosage Forms↗
PubMed1993

Detection of postural cerebral hypoperfusion with technetium-99m-HMPAO brain SPECT in patients with cerebrovascular disease.

Seventeen of 19 patients (67 +/- 8 yr, 17 males and 2 females) had more than 75% unilateral stenosis or occlusion of the internal carotid or middle cerebral artery and two patients had carotid endarterectomy that previously had 90% stenosis of the internal carotid artery. They were studied during upright 99mTc-HMPAO brain SPECT. HMPA was injected immediately after arising from a supine position. Patients were classified into Group A (n = 10) with occlusion of the internal carotid or the middle cerebral artery or Group B (n = 9) with more than 75% unilateral stenosis of the internal carotid or the middle cerebral artery and with carotid endarterectomy. Additional cerebral blood flow perfusion abnormalities between upright and supine 99mTc-HMPAO brain SPECT were detected in seven patients in Group A and in only one patient in Group B. Semiquantitative analysis showed that the asymmetric ratios between upright and supine positions changed significantly in Group A from 0.82 +/- 0.15 to 0.89 +/- 0.10 (p < 0.01), but not in Group B, from 0.89 +/- 0.11 to 0.92 +/- 0.12 (ns). Additional perfusion abnormalities were relevant to occlusion of the internal carotid or middle cerebral artery indicated postural cerebral hypoperfusion. We conclude that upright 99mTc-HMPAO brain SPECT visualizes postural cerebral hypoperfusion possibly related to silent cerebral ischemia.

Aged↗
PubMed1993

[Vitamin D dependency and vitamin D resistance].

Vitamin D dependency is classified into two clinical disorders which are caused by genetic defect of vitamin D metabolism. Vitamin D dependent rickets type I and type II are the deficiency of 25-hydroxyvitamin D-1 alpha-hydroxylase and the defect of receptor for 1 alpha,25-dihydroxyvitamin D, respectively. In contrast, vitamin D resistance shows hypophosphatemia derived from disorder(s) of phosphate transport system in renal brush border membrane. There are three clinical entities such as hereditary hypophosphatemic rickets with hypercalciuria, familial hypophosphatemic rickets and oncogenic hypophosphatemic osteomalacia. However, the real pathogenesis of these disorders have not well been understood at present.

Humans↗
PubMed1992

Impaired tetramer assembly of variant medium-chain acyl-coenzyme A dehydrogenase with a glutamate or aspartate substitution for lysine 304 causing instability of the protein.

Ninety percent of variant medium-chain acyl-CoA dehydrogenase (MCAD) alleles in patients with MCAD deficiency carry a 985 A-->G transition which causes glutamate substitution for lysine 329 in precursor (p) MCAD (K-304 in mature MCAD). We have used site-directed mutagenesis to produce three variant cDNAs encoding variant pMCAD with glutamate (Kp329E2), aspartate (Kp329D), or arginine (Kp329R) substitution for Kp329. We carried out in vitro expression of cDNAs, and incubated the translation products with isolated rat liver mitochondria. Kp329E was imported into mitochondria and processed into the mature subunit as efficiently as wild-type. Gel filtration analysis of the mitochondria revealed that at 10 min after import, markedly more K304E eluted as a monomer than did wild-type, and the amount of K304E tetramer formed was distinctly less than wild-type at any point up to 60 min after import, indicating that the assembly of K304E is defective. After further incubation, K304E decayed more rapidly than did wild-type, indicating a reduced stability. In similar studies, K304R behaved like the wild-type, while K304D closely resembled K304E, indicating that the presence of a basic residue at 304 is essential for tetramer formation and intramitochondrial stability of mature MCAD.

Acyl-CoA Dehydrogenase↗
PubMed1992

Mutations in the medium chain acyl-CoA dehydrogenase (MCAD) gene.

Medium chain acyl-CoA dehydrogenase (MCAD) catalyzes the first reaction of the beta-oxidation cycle for 4-10-carbon fatty acids. MCAD deficiency is one of the most frequent inborn metabolic disorders in populations of northwestern European origin. In the compilation of data from a worldwide study of 172 unrelated patients each representing an independent pedigree, a total of 8 different mutations have been identified. Among them, a single prevalent mutation, 985A-->G, was found in 90% of 344 variant alleles. 985A-->G causes glutamate substitution for lysine-304 in the mature MCAD subunit, which causes impairment of tetramer assembly and instability of the protein. Three of 7 rarer mutations have been identified in a few unrelated patients, while the remaining 4 have each been found in only a single pedigree. In addition to tabulating the mutations, the acyl-CoA dehydrogenase gene family, the structure of the MCAD gene and the evolution of 985A-->G mutation are briefly discussed.

Acyl-CoA Dehydrogenase↗