Yoshihiro Maruo

Association of Neonatal Hyperbilirubinemia With Bilirubin UDP-Glucuronosyltransferase Polymorphism

Objective. The incidence of nonphysiologic neonatal hyperbilirubinemia is twice as high in East Asians as in whites. We studied whether the condition was associated with mutations in the gene for bilirubin uridine 5′-diphosphate-glucuronosyltransferase (UGT1A1), a key enzyme of bilirubin catabolism. Design. We analyzed the UGT1A1 gene in 25 Japanese neonates who had nonphysiologic hyperbilirubinemia (serum bilirubin >257 μmol/L) with no obvious cause. They had all received phototherapy. The background control population consisted of 50 Japanese neonates whose transcutaneous jaundice index was monitored during the first week of life. We detected mutations by direct sequencing of polymerase chain reaction-amplified fragments of the gene. Results. We found a polymorphism for UGT1A1in exon 1; a G→A transition at nucleotide 211 caused arginine to replace glycine at position 71 of corresponding protein product (G71R). The frequency of the mutated allele in the hyperbilirubinemic group (0.34) was significantly higher (χ2 = 5.56) than in the control group (0.16). In the control group the peak transcutaneous jaundice index of the carriers of G71R was significantly higher than it was in the normal infants. Conclusions. The missense mutation causing G71R is the first reported polymorphism for UGT1A1, and the mutation is a risk factor for nonphysiologic neonatal hyperbilirubinemia. The high incidence of hyperbilirubinemia in the Japanese may be attributable to the high frequency of this missense mutation.

Prolonged unconjugated hyperbilirubinemia associated with breast milk and mutations of the bilirubin uridine diphosphate- glucuronosyltransferase gene.

Objective. Breast milk jaundice is a common problem in nursing infants. It has been ascribed to various breast milk substances, but the component or combination of components that is responsible remains unknown. During our study of defects of the bilirubin uridine diphosphate-glucuronosyltransferase gene (UGT1A1) in patients with hereditary unconjugated hyperbilirubinemia (Crigler-Najjar syndrome and Gilberts syndrome) and neonatal hyperbilirubinemia, we encountered a prolonged case associated with breastfeeding; after cessation of breastfeeding, the infants bilirubin level became normal. Genetic analysis revealed a missense mutation identical to that found in patients with Gilberts syndrome, which usually causes jaundice after puberty. We analyzed the bilirubinUGT1A1 of infants with prolonged unconjugated hyperbilirubinemia associated with breast milk to ascertain whether genetic factors are involved. Patients and Methods. We analyzed 17 breastfed Japanese infants with apparent prolonged jaundice (total serum bilirubin concentrations above 171 μmol/L [10 mg/dL]) 3 weeks to 1 month after their birth. Except for jaundice, the infants were healthy and did not show evidence of hemolytic anemia, liver dysfunction, or hypothyroidism. After cessation of breastfeeding, the serum bilirubin concentration began to decrease in all cases. When breastfeeding was resumed, serum bilirubin concentration again became elevated in some infants, but the concentration fell to within normal by 4 months of age. We analyzed the polymerase chain reaction-amplified exon, promoter, and enhancer regions of UGT1A1 by direct sequencing. Results. Sixteen infants had at least one mutation of theUGT1A1. Seven were homozygous for 211G→A (G71R), which is the most common mutation detected in the East Asian population, and the mutant enzyme had one third of the normal activity. G71R is the most common missense mutation we found in our analyses in Japanese patients with Gilberts syndrome, and it corresponds to aUGT1A1 polymorphism in the Japanese population (the allele frequency is .16). One was heterozygous for 1456T→G (Y486D) and homozygous for 211G→A. Six were heterozygous for 211G→A. One was heterozygous for both 211G→A and a TATA box mutation (A(TA)7TAA). One had a heterozygous mutation in an enhancer region (C→A at −1353). We did not detect a homozygous A(TA)7TAA mutation, which was the most common cause of Gilberts syndrome in European population, in this study of Japanese infants with prolonged hyperbilirubinemia triggered by breast milk. Conclusions. The results indicate that defects ofUGT1A1 are an underlying cause of the prolonged unconjugated hyperbilirubinemia associated with breast milk. One or more components in the milk may trigger the jaundice in infants who have such mutations. The mutations we found were identical to those detected in patients with Gilberts syndrome, a risk factor of neonatal nonphysiologic hyperbilirubinemia and a genetic factor in fasting hyperbilirubinemia.

Genetic polymorphisms of bilirubin uridine diphosphate‐glucuronosyltransferase gene in Japanese patients with Crigler–Najjar syndrome or Gilbert's syndrome as well as in healthy Japanese subjects

Background and Aim:  Numerous mutations of bilirubin uridine diphosphate‐glucuronosyltransferase gene (UGT1A1) have been reported in patients with familial unconjugated hyperbilirubinemia. The UGT1A1 mutation appears to be considerably different among ethnic groups. To clarify the incidence of this gene mutation in the Japanese population, the presence of UGT1A1 mutation was investigated in a group of Japanese patients with Crigler–Najjar syndrome type 2 (CNS2) and Gilberts syndrome (GS), as well as in healthy anicteric subjects.

Transient Congenital Hypothyroidism Caused by Biallelic Mutations of the Dual Oxidase 2 Gene in Japanese Patients Detected by a Neonatal Screening Program

CONTEXT Mutations in dual oxidase (DUOX2) have been proposed as a cause of congenital hypothyroidism. Previous reports suggest that biallelic mutations of DUOX2 cause permanent congenital hypothyroidism and that monoallelic mutations cause transient congenital hypothyroidism. OBJECTIVE To clarify the inheritance of hypothyroidism, we looked at the DUOX2 gene in patients with transient congenital hypothyroidism. DESIGN DUOX2, thyroid peroxidase, Na+/I- symporter and dual oxidase maturation factor 2 genes were analyzed in eight patients with transient congenital hypothyroidism, using the PCR-amplified direct sequencing method. PATIENTS The eight patients were found by a neonatal screening program. Six of these patients belonged to two independent families; the other two were unrelated. Their serum TSH values varied from 24.8-233.0 mU/liter. Six of the eight patients had a low serum freeT4 level (0.19-0.84 ng/dl). Seven of the eight patients were treated with thyroid hormone replacement therapy, which ceased to be necessary by 9 yr of age. RESULTS Eight novel mutations were detected in the DUOX2 gene. Four patients in one family were compound heterozygous for p.L479SfsX2 and p.K628RfsX10. Two patients in a second family were compound heterozygous for p.K530X and p.[E876K;L1067S]. The two remaining unrelated patients were also compound heterozygous, for p.H678R/p.L1067S and p.A649E/p.R885Q, respectively. CONCLUSION All eight patients had biallelic mutations in the DUOX2 gene. We find that loss of DUOX2 activity results in transient congenital hypothyroidism and that transient congenital hypothyroidism caused by DUOX2 mutations is inherited as an autosomal recessive trait.

Two linked polymorphic mutations (A(TA)7TAA and T-3279G) of UGT1A1 as the principal cause of Gilbert syndrome

Gilbert syndrome is a mild hereditary unconjugated hyperbilirubinemia caused by mutations in the bilirubin UDP-glucuronosyltransferase gene (UGT1A1). The mutation, A(TA)7TAA, is thought to be the sole cause of the syndrome in Caucasians, but an enhancer polymorphism (T-3279G) that lowers transcriptional activity has recently been reported. We have tested the linkage of the two mutations in 11 Caucasians and 12 Japanese patients who were homozygous for A(TA)7TAA. All 23 patients were also homozygous for T-3279G, indicating that T-3279G and A(TA)7TAA were linked. The decrease in transcription caused by both mutations together may be essential to the syndrome.

Six novel UDP-glucuronosyltransferase (UGT1A3) polymorphisms with varying activity

AbstractHuman UDP-glucuronosyltransferase (UGT) is a part of a major excretion pathway for endobiotics and xenobiotics. The UGT family of genes is highly polymorphic, and our aim is to describe novel polymorphisms at the UGT1A3 locus and determine how they alter substrate metabolism and drug reactions. One hundred healthy Japanese adults volunteered for the present study. We sequenced PCR-amplified fragments of the gene directly, and calculated the frequency of the genetic variations detected. To measure variant enzyme activity, we constructed five expression models and used estrone as the substrate in the assays. We identified six novel single nucleotide polymorphisms (SNPs). Of these, four caused amino acid substitutions (17A→G: Q6R, 31T→C: W11R, 133C→T: R45W, and 140T→C: V47A) and the remaining two were silent (81G→A: E27E and 447A→G: A159A). We found five types of alleles having differing SNP combinations: wild type (frequency=0.61), W11R-E27E-A159A (0.10), Q6A-W11R-E27E-A159A (0.055), W11R-E27E-V47A-A159A (0.125), and R45W (0.11). Expression studies found that the variants changed the enzyme efficiencies (Km/Vmax) to 121% of the wild type for W11R, 86% for Q6R-W11R, 369% for W11R-V47A, and 70% for R45W. Several UGT 1A3 polymorphisms exist in the Japanese population, having different levels of activity. These polymorphisms are capable of affecting the steady state levels of estrogens, and may increase sensitivity to adverse drug effects.

Polymorphism of UDP-Glucuronosyltransferase and Drug Metabolism

UDP-glucuronosyltransferase is a group of catabolic enzymes involved in the detoxification and excretion of many xenobiotic and endogeneous substances in intrahepatic and extrahepatic tissues. The group consists of two subfamilies, UGT1 and UGT2. UGT1 consists of 5 exons and has a unique gene structure. There are thirteen exon 1s from UGT1A1 to UGT1A13P, and exon 2 to exon 5 are used in common for all mRNAs expressed from the gene. Each isoform of UGT1 results from differential splicing of exon1s to common exon 2-5, and has an unique spectrum of substrate specificity. In contrast, the genes of the UGT2 family consist of 6 exons, and all the enzymes have an individual set of exon 1 to exon 6. In UGT1 there are no reports of polymorphism in the common exons, although a number of polymorphisms have been reported for exon 1s. The mutations of UGT1A1 cause hereditary unconjugated hyperbilirubinemias: Crigler-Najjar syndrome type I, type II and Gilbert syndrome. UGT1A1 has two major polymorphisms--a missense mutation of G71R and an insertion mutation of TATA box. Prevalence of Gilbert syndrome is attributed to these polymorphisms. Since UGT1A1 metabolizes not only bilirubin but also hormones and drugs, the mutations could be involved in carcinogenesis and adverse drug reactions. Recent studies also revealed a widespread presence of diverse polymorphisms in other isoforms of UGT1 as well as the UGT2 family, including UGT1A6, UGTG1A7, UGT1A8, UGT1A10, UGT2B4, UGT2B7 and UGT2B15. The incidences and types of the polymorphisms for these enzymes are quite different in region and ethnic groups. Understanding of these polymorphisms is essential for the prevention of adverse effects of a considerable number of drugs and to predict cancer risks.

Comprehensive molecular analysis of Japanese patients with pediatric-onset MODY-type diabetes mellitus

Yorifuji T, Fujimaru R, Hosokawa Y, Tamagawa N, Shiozaki M, Aizu K, Jinno K, Maruo Y, Nagasaka H, Tajima T, Kobayashi K, Urakami T. Comprehensive molecular analysis of Japanese patients with pediatric‐onset MODY‐type diabetes mellitus.

Gilbert syndrome caused by a homozygousmissense mutation (Tyr486Asp) of bilirubinUDP-glucuronosyltransferase gene

We report a case of Gilbert syndrome caused by a homozygous missense mutation (Tyr486Asp) of the bilirubin UDP-glucuronosyltransferase gene. Homozygous missense mutations of the gene have previously been recognized as responsible for Crigler-Najjar syndrome type II. We conclude that Gilbert syndrome in some patients results from homozygous missense mutations of the UDP-glucuronosyltransferase gene.

Seizure Susceptibility Due to Antihistamines in Febrile Seizures

The aim of this study was to determine whether seizure susceptibility due to antihistamines is provoked in patients with febrile seizures. The study population comprised 14 patients with simple febrile seizures and 35 patients with complex febrile seizures. Detailed clinical manifestations were compared between patients with and without administration of antihistamine. The time from fever detection to the seizure onset was significantly shorter in the antihistamine group than that in the nonantihistamine group, and the duration of seizures was significantly longer in the antihistamine group than that in nonantihistamine group. Interleukin-1beta is thought to be associated with causing febrile seizures via its dual role as a pyrogen and convulsant substance. Moreover, interleukin-1beta may activate the turnover of hypothalamic neural histamine. These considerations, along with the present results, suggest that the depletion of hypothalamic neuronal histamine induced by antihistamines may increase neuronal excitability, thereby increasing seizure susceptibility in patients with febrile seizures.