中島 葉子

新生児マス・スクリーニングにおいてガラクトース(Gal)、ガラクトース-1-リン酸(Gal-1-P)高値により検出される症例には、先天性ガラクトース代謝酵素欠損症以外の疾患も認められるが、その対応については一定の見解は得られていない。今回我々は、Gal、Gal-1-P高値により発見された症例の臨床経過を比較することにより、Galスクリーニングの意義を検討した。対象は2004年1月〜2013年12月の10年間に高ガラクトース血症の精査を目的に当科を受診し、その後の経過を追えた63例について検討した。この結果、エピメラーゼ欠損症(III型)17例、自然軽快例40例、外科的処置を要した門脈体循環シャント6例であった。初診時のGal、Gal-1-P、総胆汁酸値の比較では、III型でGal-1-Pが高値、外科的処置例では総胆汁酸が高い傾向があり、外科的介入の要否は初診時の血液検査結果からは予測困難であった。自然閉鎖しない門脈体循環シャントは外科的介入が必要で、早期発見することで予後の改善が期待できる。新生児マス・スクリーニングではガラクトース代謝酵素欠損症以外も積極的に発見していくことが有用であると思われた。(著者抄録)

先天性代謝異常症の一つであるピリミジン代謝異常症は、ピリミジンヌクレオチドの合成系や分解系における酵素欠損によっておきる疾患の総称である。その臨床症状は無症状から重度発達障害、筋緊張低下、小頭症など様々である。未だ症例数に乏しく発症頻度や遺伝子変異等の詳細は不明であり、さらなる症例の蓄積が必要とされている。ピリミジン代謝異常症のうち、合成系のオロト酸尿症と分解系のdihydropyrimidine dehydrogenase(DPDase)欠損症、dihydropyrimidinase(DHPase)欠損症およびureidopropionase(UPase)欠損症を一斉にスクリーニングする方法として、UPLC-MS/MSを用いた尿中ピリミジン代謝物濃度の定量法を検討した。本法によりDHPase欠損症、UPase欠損症患者の尿中代謝物の定量をおこなったところ、コントロールに対して大過剰の代謝物が排泄されていた。また、DPDase欠損症、DHPase欠損症患者へのフッ化ピリミジン系抗がん剤である5-fluorouracil投与により重篤な副作用が発現したと報告されており、本法の尿を用いた簡便なスクリーニングを応用することで抗がん剤の副作用を未然に防ぐことも可能である。さらに、オロト酸尿症の指標であるorotic acidは、allopurinolなどの薬剤投与によって一過性に上昇する。このため、オロト酸合成の原料となるcarbamyl phosphateが蓄積したornithine transcarbamylase(OTC)欠損症患者へのallopurinol負荷試験ではorotic acidが過剰に上昇する。このためorotic acid定量はOTC欠損症患者およびその保因者の発見にも有用である。このように、UPLC-MS/MSによるピミジン類の定量は、ピリミジン代謝異常症やOTC欠損症のスクリーニングに有用である。(著者抄録)

Glycogen storage disease type Ib (GSDIb) is caused by a deficiency in the glucose-6-phosphate transporter (G6PT), which leads to neutrophil dysfunction. However, the underlying causes of these dysfunctions and their relationship with glucose homeostasis are unclear. Induced pluripotent stem cells (iPSCs) hold a great promise for advances in developmental biology, cell-based therapy and modeling of human disease. Here, we examined the use of iPSCs as a model for GSDIb. In this study, one 2-year-old patient was genetically screened and diagnosed with GSDIb. We established iPSCs and differentiated these cells into hepatocytes and neutrophils, which comprise the main pathological components of GSDIb. Cells that differentiated into hepatocytes exhibited characteristic albumin secretion and indocyanine green uptake. Moreover, iPSC-derived cells generated from patients with GSDIb metabolic abnormalities recapitulated key pathological features of the diseases affecting the patients from whom they were derived, such as glycogen, lactate, pyruvate and lipid accumulation. Cells that were differentiated into neutrophils also showed the GSDIb pathology. In addition to the expression of neutrophil markers, we showed increased superoxide anion production, increased annexin V binding and activation of caspase-3 and caspase-9, consistent with the GSDIb patient's neutrophils. These results indicate valuable tools for the analysis of this pathology and the development of future treatments.

Main indications for liver transplantation in the pediatric population include biliary atresia and inherited metabolic diseases. The present study evaluated whether there are differences between pediatric patients undergoing living-related liver transplantation due to the two diseases in terms of their oxidative and immunological status Pduring their regular outpatient follow-up visits. A clinical outpatient study measuring serum oxidative stress index (calculated as serum oxidant/antioxidant ratio, in the form of serum total hydroperoxide/serum biological antioxidative potential), serum terminal complement component 5a, as an indicator of complement activity and immunological status, and transforming growth factor-β1, as a marker of liver fibrosis, in 16 patients (6 males and 10 females, 2.5-15 years old) who received living-related liver transplantation due to inherited metabolic diseases (n=6 in the form of propionic acidemia [n=1], methylmalonic acidemia [n=1], arginase deficiency [n=1], tyrosinemia [n=2], and glycogen storage disease type 1b [n=1], with an age range of 2.4-14.6 years old) and due to biliary atresia ([n=10], with an age range of 2.9-14.5 years old). Serum oxidative stress index, complement component-5a, and transforming growth factor-β1 were significantly higher in the inherited metabolic diseases group than in the biliary atresia group. In all patients, serum oxidative stress index correlated positively with complement component-5a and transforming growth factor-β1. Patients who receive living-related liver transplantation due to inherited metabolic diseases are prone to higher oxidative stress, complement activity, and serum transforming growth factor-β1.

β-Ureidopropionase is the third enzyme of the pyrimidine degradation pathway and it catalyzes the conversion of N-carbamyl-β-alanine and N-carbamyl-β-aminoisobutyric acid to β-alanine and β-aminoisobutyric acid, respectively, and ammonia and CO2. To date, only 16 genetically confirmed patients with a complete ß-ureidopropionase deficiency have been reported. Here, we report the clinical, biochemical, and molecular analysis of a newly identified patient with β-ureidopropionase deficiency. Mutation analysis of the UPB1 gene showed that the patient was compound heterozygous for a novel synonymous mutation c.93C &gt T (p.Gly31Gly) in exon 1 and a previously described missense mutation c.977G &gt A (p.Arg326Gln) in exon 9. The in silico predicted effect of the synonymous mutation p.Gly31Gly on pre-mRNA splicing was investigated using a minigene approach. Wild-type and the mutated minigene constructs, containing the entire exon 1, intron 1, and exon 2 of UPB1, yielded different splicing products after expression in HEK293 cells. The c.93C &gt T (p.Gly31Gly) mutation resulted in altered pre-mRNA splicing of the UPB1 minigene construct and a deletion of the last 13 nucleotides of exon 1. This deletion (r.92-104delGCAAGGAACTCAG) results in a frame shift and the generation of a premature stop codon (p.Lys32SerfsX31). Using a minigene approach, we have thus identified the first synonymous mutation in the UPB1 gene, creating a cryptic splice-donor site affecting pre-mRNA splicing. © 2013 Copyright Taylor and Francis Group, LLC.

Background: Valproate (VPA) is a simple fatty acid and a substrate for the fatty acid beta-oxidation pathway. Previous data suggested that the toxicity of VPA may be provoked by carnitine deficiency and the inhibition of mitochondrial beta-oxidation. Objective: The aim of the present study was to elucidate the effect of VPA treatment on carnitine and isomer-differentiated acylcarnitine disposition, and determined the relationships between acylcarnitines and blood VPA levels in long-term treated patients with VPA and/or other antiepileptic drugs. Methods: Serum samples were obtained from children aged 1-15 years old treated for at least 6 months with VPA alone (n = 28) or VPA combined with other anticonvulsants (a = 23) and untreated controls (a = 23). Serum acylcarnitines were separated from their isomers and quantified using high-performance liquid chromatography tandem mass spectrometry. Results: We found higher 3-hydroxyisovalerylcarnitine levels and trace amounts of valproylcarnitine in both VPA monotherapy and polytherapy patients. Other acylcarnitines, hexanoylcarnitine, C12, C14:1-carnitines and the ratio of long-chain acylcarnitine to free carnitine were also higher in VPA polytherapy individuals than in controls. VPA monotherapy does not result in decreases in free carnitine or in the accumulation of long-chain acylcarnitines. Blood VPA concentrations correlated positively with hexanoylcarnitine, C12, C14:1, C16:1, C18:1-carnitines in all VPA-treated children (a = 51). Conclusion: Long-term VPA treatment in pediatric patients could affect some specific acylcarnitines, which is enhanced by the concomitant use of other anticonvulsants, and the formation of valproylcarnitine alone seems insufficient to develop severe carnitine deficiency at therapeutic doses of VPA. (C) 2010 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Urea cycle disorders are congenital metabolic disorders that often cause episodic hyperammonemia. Neuroimaging in episodic hyperammonemia demonstrates several patterns of brain injuries, including focal lesions in the lentiform nucleus, insula, cingulate gyrus, and perirolandic fissure, as well as diffuse cerebral edema. In cases with neonatal onset of hyperammonemia, similar lesions have also been reported. We herein report a boy with severe neonatal hyperammonemia caused by ornithine transcarbamylase deficiency. He presented with parieto-occipital encephalomalacia, which resembles severe neonatal hypoglycemia on magnetic resonance imaging. This radiological finding may indicate parieto-occipital vulnerability not only to hypoglycemia but also to hyperammonemia. (C) 2009 Elsevier B.V. All rights reserved.

Some oral antibiotics contain a pivalate ester, because molecules with a pivalate entity show enhanced absorption in the intestine. Upon absorption, such a "prodrug" is broken down into the active form of a given antibiotic and a pivalate molecule, the latter of which is converted to pivaloylcarnitine through pivaloyl-CoA and is excreted in the urine. Long-term administration of drugs containing pivalate decreases blood carnitine level and causes defects in fatty acid oxidation. Here, we used liquid chromatography tandem mass spectrometry to measure carnitine and pivaloylcarnitine levels in two patients (Patient 1: 16-month-old boy and Patient 2: 18-month-old boy) with secondary carnitine deficiency and hypoglycemic convulsions caused by pivalate-containing antibiotics. Both patients were administered excessive doses of pivalate for the long-term treatment of recurrent infection, and consequently, the serum free carnitine levels were very low (Patient 1: 1.0 mu mol/L and Patient 2: 0.4 mu mol/L), compared to normal range of 33.3-43.0 mu mol/L, while the serum pivaloylcarnitine levels were elevated from normally undetectable level (Patient 1: 3.7 mu mol/L and Patient 2: 1.6 mu mol/L). Patient 1 recovered immediately after the glucose infusion, whereas Patient 2 remained symptomatic even after blood glucose level was normalized and fully recovered after carnitine supplementation. The urine pivaloylcarnitine level in Patient 2 was increased during carnitine supplementation (from 821.4 to 12,200 mu mol/g creatinine) even after discontinuing the antibiotics, indicating that a considerable amount of pivalate was accumulated in the tissues. In conclusion, long-term administration of pivalate-containing antibiotics should be avoided particularly in children.