Michinori Ito

Mutations in the X-linked pyruvate dehydrogenase (E1) α subunit gene (PDHA1) in patients with a pyruvate dehydrogenase complex deficiency

Defects in the pyruvate dehydrogenase (PDH) complex are an important cause of primary lactic acidosis, a frequent manifestation of metabolic disease in children. Clinical symptoms can vary considerably in patients with PDH complex deficiencies, and almost equal numbers of affected males and females have been identified, suggesting an autosomal recessive mode of inheritance of the disease. However, the great majority of PDH complex deficiencies result from mutations in the X‐linked pyruvate dehydrogenase (E1) α subunit gene (PDHA1). The major factors that contribute to the clinical variation in E1α deficiency and its resemblance to a recessive disease are developmental lethality in some males with severe mutations and the pattern of X‐inactivation in females.

Dynamic Changes in Serum Leptin Concentrations during the Fetal and Neonatal Periods

We investigated the dynamics of the leptin concentration throughout the perinatal period. Serum leptin concentrations in venous cord blood at different gestational ages were measured in 20 preterm and 139 term newborns, as well as in 143 pregnant women and 24 term newborns at approximately 6 d of life. Leptin concentrations in preterm newborns (mean 4.6 ± 6.9 ng/mL) were lower than those in term newborns (mean 19.6 ± 14.3 ng/mL) and tended to increase according to gestational age and birth weight, especially from the late stage of gestation. Leptin concentrations in pregnant women increased from the first trimester and then remained higher than those in non-pregnant women throughout the remainder of pregnancy even after controlling for body mass index. The leptin concentrations of newborns declined rapidly and were extremely low by approximately 6 d of life (mean 1.9 ± 1.1 ng/mL). These results suggest that fetuses might produce a part of circulating leptin in their own adipocytes and that the relatively high leptin concentrations at birth and their rapid decline in the early neonatal period might reflect the dramatic changes of the hormonal and nutritional state during the perinatal period.

Molecular Analysis of Abnormal Pyruvate Dehydrogenase in a Patient with Thiamine-Responsive Congenital Lactic Acidemia

ABSTRACT: 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 E1α 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 parents genomic DNA. In this study, we have obtained the first evidence at the molecular level for a mutation of thiamine-responsive PDHC deficiency.

A Survey of the Newborn Populations in Belgium, Germany, Poland, Czech Republic, Hungary, Bulgaria, Spain, Turkey, and Japan for the G985 Variant Allele with Haplotype Analysis at the Medium Chain Acyl-CoA

Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is an inborn error of fatty acid metabolism. It is one of the most frequent genetic metabolic disorders among Caucasian children. The G985 allele represented 90% of all the variant alleles of the MCAD gene in an extensive series of retrospective studies. To study the distribution of the G985 allele, newborn blood samples from the following countries were tested: 3000 from Germany (1/116), 1000 each from Belgium (1/77), Poland (1/98), Czech Republic(1/240), Hungary (1/168), Bulgaria (1/91), Spain (1/141), Turkey (1/216), and 500 from Japan (none). The frequency is shown in parentheses. The haplotype ofG985 alleles in 1 homozygote and 57 heterozygote samples were then analyzed using two intragenic MCAD gene polymorphisms (TaqI andGT-repeat). The result indicated that only 1 of the 10 known haplotypes was associated with the G985 mutation, suggesting thatG985 was derived originally from a single ancestral source. We made a compilation of the G985 frequencies in these countries and those in nine other European countries studied previously. The G985 distribution was high in the area stretching from Russia to Bulgaria in the east and in all northern countries in western and middle Europe, but low in the southern part of western and middle Europe. The incidence among ethnic Basques appeared to be low. This distribution pattern and the fact that allG985 alleles belong to a single haplotype suggest thatG985 mutation occurred later than the ΔF508 mutation of the CFTR, possibly in the neolithic or in a later period, and was brought into Europe by IndoEuropean-speaking people. The panEuropean distribution of the G985 allele, including Slavic countries from which patients with MCAD deficiency have rarely been detected, indicates the importance of raising the level of awareness of this disease.

Enzymologic Studies and Therapy of Leigh's Disease Associated with Pyruvate Decarboxylase Deficiency

Summary: An 11-month-old boy with muscle hypotonia and neurologic deteriorations had lactic acidosis, pyruvic acidemia and alaninemia due to deficiency of the pyruvate dehydrogenase complex in his platelets and of pyruvate decarboxylase in his muscle. When placed on a low carbohydrate-high fat diet for 6 months, his blood levels of lactate and pyruvate became nearly normal, but his cerebrospinal fluid levels of lactate and pyruvate remained high. Despite this dietary therapy, neurologic deterioration progressed slowly. He died of pneumonia after artificial respiration for 3 wk. At autopsy, extensive symmetric necrotic lesions were found in the brain including proliferation of capillaries and gliosis in the brain stem and diffuse demyelination in the white matter. These lesions were consistent with those observed in Leighs disease. The activities of the pyruvate dehydrogenase complex and pyruvate decarboxylase in various tissues obtained at autopsy were less than 10% of control values; however, the activities of pyruvate carboxylase and α-ketoglutarate decarboxylase were within the normal limits. This patient with Leighs disease had an isolated deficiency of pyruvate decarboxylase in various tissues.Speculation: Deficiency of pyruvate decarboxylase in brain may be one cause of clinical and pathologic features of Leighs disease. The absence of pyruvate decarboxylase in the cerebellum, cerebrum, kidney, liver, muscle and platelets of the patient supports the hypothesis that there is only one form of pyruvate decarboxylase in humans.

Comparison of GAD and ICA512/IA-2 Antibodies at and After the Onset of IDDM

OBJECTIVE Longitudinal changes in GAD antibody (Ab) and ICA512/IA-2 (ICA512) Ab were examined in relation to age at the onset of diabetes and autoimmunity against the thyroid gland. RESEARCH DESIGN AND METHODS GADAb, ICA512Ab, and antithyroid autoantibody were examined at onset in 40 juvenile-onset IDDM patients (17 males, 23 females, age at onset 9.4 ± 4.1 years, range 1.7−20). To assess the changes in antibody levels, 29 patients were followed up with sequential serum samples for up to 5 years. RESULTS At onset, GADAb, ICA512Ab, and antithyroid autoantibody (thyroglobulinAb or thyroid peroxidaseAb) were found in 70, 58, and 25% of the 40 patients, respectively. Prepubertal patients (n = 21) had a significantly higher prevalence and index of ICA512Ab compared with pubertal patients (n = 19) (76 vs. 37%, P = 0.012, and 2.43 ± 2.36 vs. 0.66 ± 1.23, P = 0.011), while GADAb was more prevalent in pubertal patients (57 vs. 84%, P = 0.09). A longitudinal analysis of GADAb and ICA512Ab showed that GADAb levels declined more slowly than those of ICA512Ab (P = 0.008). Patients with continuous extremely high levels of GADAb also had high levels of antithyroid autoantibody. CONCLUSIONS The measurement of ICA512Ab is useful in prepubertal patients, who often show rapid progression of the disease. The presence of autoimmunity against thyroid gland seems to influence the GADAb level but not the ICA512Ab level.

Treatment of chronic congenital lactic acidosis by oral administration of dichloroacetate

Sodium dichloroacetate (DCA) was administered orally at a dose of 50 mg per kg body weight twice or three times per day to a newborn infant with lactic acidosis of unknown cause (patient 1) and to a 15-year-old boy with mitochondrial encephalomyopathy associated with lactic acidosis (patient 2). In patient 1, during treatment with DCA, DCA accumulated in the blood judging from the findings that the urinary excretion of DCA increased cumulatively and the blood lactate level rapidly decreased to the normal range. In patient 2, the blood DCA level gradually increased during treatment to a concentration of 250 µgml−1 and the blood lactate level decreased and was maintained within the normal range. DCA was detected in the brain (25 µg g tissue−1) and the liver, kidney and muscle (33.8, 33.8 and 26.3 µg g tissue−1, respectively) obtained at autopsy of patient 1, and in the cerebrospinal fluid of patient 2 at a concentration of 125 µg ml−1 when the blood concentration was 250 µg ml−1. The lactate levels in the cerebrospinal fluid decreased from 7 and 4mmoll−1 to 2.4 and 2.6 mmoll−1 in patients 1 and 2, respectively. Thus DCA may be useful in clinical treatment of chronic congenital lactic acidosis because it seems to cross the blood-brain barrier. However, it must be given at non-toxic doses, determined by monitoring the concentrations of lactate and DCA in the blood, because orally administered DCA tends to accumulate in tissues.

Thiamine-responsive lactic acidaemia: role of pyruvate dehydrogenase complex

Abstract Lactic acidaemia is sometimes associated with a defect of the pyruvate dehydrogenase complex (PDHC), catalysing the thiamine-dependent decarboxylation of pyruvate. The activity of PDHC for different thiamine pyrophosphate (TPP) concentrations was determined in 13 patients with lactic acidaemia, clinically responsive to thiamine treatment in order to assess the role of PDHC in the aetiology of thiamine-responsive lactic acidaemia. Culture of lymphoblastoid cells and skin fibroblasts and muscle biopsies were performed in these 13 patients. The activity of PDHC to sodium dichloroacetate (DCA), known as the activator of PDHC, was also examined. Three groups were identified according to PDHC activity. Group 1 (two patients) displayed very low PDHC activity, which was not increased by DCA. This PDHC activity increased at high TPP concentrations. Group 2 (five patients) displayed below normal PDHC activity at low TPP concentrations, increased by DCA. This PDHC activity became normal at high TPP concentrations. PDHC deficiency in these patients of groups 1 and 2 was due to a decreased affinity of PDHC for TPP. Group 3 included six patients with normal PDHC activity at low as well as high TPP concentrations. This PDHC activity was increased by DCA. Conclusion High concentrations of TPP may be required for maximal activity of PDHC in some patients with lactic acidaemia. The assay of PDHC activity, performed at a low concentration of TPP (1 × 10−4 mM) allows selection of patients with thiamine-responsive lactic acidaemia.

Effects of Dichloroacetate on Pyruvate Metabolism in Rat Brain in Vivo

Summary: The effects of dichloroacetate (DCA) on the activity of the pyruvate dehydrogenase (PDH) complex and associated changes in the lactate and glucose levels in rat brain were investigated in vivo. The average activities of the active form of the PDH complex in the brain, liver and muscle of starved rats were respectively 0.40 ± 0.04, 0.07 ± 0.04, and 0.17 ± 0.11 μmol/min/g tissue, and amounted to 21, 11, and 16% of the total activity of the complex. Intraperitoneal injection of DCA (125 mg/kg) increased the percentage of the active form of the PDH complex in the brain, liver, and muscle to 107, 40, and 84%, respectively. DCA significantly lowered the lactate and glucose concentrations of the brain and blood. A lower dose of DCA (12.5 mg/kg) also caused significant increase in activity of the PDH complex in the brain, but did not significantly change the lactate or glucose concentration of the brain. These results suggest that DCA crosses the blood-brain barrier reasonably well.

Type II citrullinaemia (citrin deficiency) in a neonate with hypergalactosaemia detected by mass screening

Type II citrullinaemia (CTLN2) is an adult- or late childhood-onset liver disease characterized by a liver-specific defect in argininosuccinate synthetase protein. The enzyme abnormality is caused by deficiency of the protein citrin, which is encoded by the SLC25A13 gene. Until now, however, few cases with SLC25A13 mutations have been reported in children with liver disease. We describe an infant who presented with neonatal hepatitis in association with hypergalactosaemia detected by neonatal mass screening. DNA analysis of SLC25A13 revealed that the patient was homozygous for a IVS11+1G>A mutation. This case suggests that SLC25A13 mutant should be suspected in neonatal patients with hypergalactosaemia of unknown cause.