Glucose-6-phosphate dehydrogenase deficiency, the UDP-glucuronosyl transferase 1A1 gene, and neonatal hyperbilirubinemia

Glucose-6-phosphate dehydrogenase deficiency and neonatal indirect hyperbilirubinemia: a retrospective cohort study among 40,305 consecutively born babies

BACKGROUND AND OBJECTIVE

Glucose-6-phosphate dehydrogenase deficiency (G6PDD) being highly prevalent in the Middle East, the primary objective was to estimate the incidence of neonatal jaundice among G6PD-deficient neonates and to explore its association with various risk factors.

METHODS

This retrospective cohort study includes 7 years data of neonates diagnosed with G6PDD between 1st January 2015, and 30 September 2022, from Al Wakra Hospital, HMC Qatar.

RESULTS

Among the 40,305 total births, 1013 had G6PDD with an incidence of 2.51%. Of all the G6PDD babies, 24.6% (249/1013) received phototherapy and three babies required exchange transfusion. Statistically significant associations were noted between the need for phototherapy and gestational age, gestational age groups, birth weight, and birth weight groups, but logistic regression analysis showed significant association for phototherapy only with the gestational age group.

CONCLUSION

Universal screening and proper follow-up is essential for G6PDD as it plays crucial role in neonatal jaundice.

The Genetics of Glucose-6-Phosphate-Dehydrogenase (G6PD) and Uridine Diphosphate Glucuronosyl Transferase 1A1 (UGT1A1) Promoter Gene Polymorphism in Relation to Quantitative Biochemical G6PD Activity Measurement and Neonatal Hyperbilirubinemia

Glucose-6-phosphate dehydrogenase (G6PD) deficiency and polymorphism in uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) were associated with significant neonatal hyperbilirubinemia (NHB) and increased risk for kernicterus. However, quantitative screening tests for G6PD enzyme activity proved unsatisfactory in estimating the risk for significant NHB, especially in heterozygous females that could present phenotype overlap between normal homozygotes, heterozygotes, and deficient homozygotes, resulting in a continuum of intermediate G6PD activity.

OBJECTIVE

To examine the association of genotype and phenotype in newborns with decreased G6PD activity and its relation to NHB.

STUDY DESIGN

Quantitative G6PD enzyme activities were measured on umbilical cord blood samples. After accepting parental consent, samples were analyzed for G6PD mutations and UGT1A1 gene polymorphisms (number of TA repeats in the UGT1A1 promoter). The associations to quantitative G6PD activity and bilirubin levels were assessed.

RESULTS

28 females and 27 males were studied. The Mediterranean mutation (NM_001360016.2(G6PD): c.563C>T (p.Ser188Phe)) was responsible for most cases of G6PD deficiency (20 hemizygous males, 3 homozygous and 16 heterozygous females). The association between this mutation, decreased G6PD activity and higher bilirubin levels was confirmed. Heterozygosity to 6/7 TA repeats in the UGT1A1 promoter was associated with increased NHB, especially in female newborns with G6PD deficiency. However, it seems that the interaction between G6PD deficiency, UGT1A1 promoter polymorphism, and NHB is more complex, possibly involving other genetic interactions, not yet described. Despite genotyping females with G6PD deficiency, the overlap between the upper range of borderline and the lower range of normal G6PD activity could not be resolved.

CONCLUSIONS

The results of this study highlight the possibility for future implementation of molecular genetic screening to identify infants at risk for significant NHB, especially UGT1A1 polymorphism in heterozygous females with borderline G6PD deficiency. However, further studies are needed before such screening could be applicable to daily practice.

Bilirubin metabolism and UDP-glucuronosyltransferase 1A1 variants in Asians: Pathogenic implications and therapeutic response

In the Asian general population, at least six single-nucleotide variants (SNVs) in the UDP-glucuronosyltransferase (UGT) 1A1 gene have been identified: -3279T>G, -53A(TA)₆ TAA>A(TA)₇ TAA, 211G>A, 686C>A, 1091C>T, and 1456T>G. Each of these six SNVs was observed in at least four ethnic groups of the 12 Asian populations studied. In East Asian populations, the descending frequency of these six SNVs was as follows: -3279G>[-53A(TA)₇ TAA, 211A]>(686A, 1091T)>1456G. Because of the presence of linkage disequilibrium and the expulsion phenomenon, when the SNVs -3279G, -53A(TA)₇ TAA, 211A, and 686A were simultaneously involved, 15 instead of the estimated 81 genotypes were observed. Those carrying 686AA or 1456GG developed Gilbert's syndrome or Crigler-Najjar syndrome type 2. Both -53A(TA)₇ TAA/A(TA)₇ TAA and 211AA are the main causes of Gilbert's syndrome in East Asian populations. In East Asian populations, the 211AA genotype is the main cause of neonatal hyperbilirubinemia, whereas -53A(TA)₇ TAA/A(TA)₇ TAA exerts a protective effect on hyperbilirubinemia development in neonates fed with breast milk. Both 211A and -53A(TA)₇ TAA are significantly associated with adverse drug reactions induced by irinotecan (one of the most widely used anticancer agents) in Asians. However, at least three common SNVs (-3279G, -53A(TA)₇ TAA, and 211A) should be comprehensively analyzed. This study investigated the clinical significance of these six SNVs and demonstrated that examining UGT1A1 variants in Asian populations is considerably challenging.

Risk Factors Predicting the Need for Phototherapy in Glucose 6 Phosphate Dehydrogenase-Deficient Infants in a Large Retrospective Cohort Study

INTRODUCTION

Glucose 6-phosphate dehydrogenase (G6PD) deficiency increases the risk of severe neonatal hyperbilirubinemia. This study evaluates the risk factors predicting the need for phototherapy in G6PD-deficient neonates after 72 h of age and assesses the safety of early discharge.

METHODS

A retrospective cohort study of 681 full-term G6PD-deficient infants with a birth weight ≥2,500 g over 4 years was conducted. We compared the baseline characteristics, bilirubin level on day 4 (after 72 h of life), day of peak bilirubin, G6PD levels, and concomitant ABO incompatibility between the group that required phototherapy (Group A) and those who did not (Group B).

RESULTS

396 infants (58%), predominantly males, required phototherapy in the first week of life. The infants who required phototherapy had a lower median gestational age (38.3 vs. 38.7 weeks, p < 0.01) and had lower G6PD levels (2.3 ± 2.5 vs. 3 ± 3.4 IU, p < 0.05) compared to the controls. The mean day-four total serum bilirubin (TSB) levels were higher (213 ± 32 vs. 151 ± 37 µmol/L, p < 0.01), with bilirubin level peaking earlier (3 vs. 4 days of life, p < 0.01) in group A. Regression analysis identified TSB levels on day 4, Chinese race, lower gestation, and concomitant ABO incompatibility as the significant predictors for the need for phototherapy in the study population. In particular, coexisting ABO blood group incompatibility increased the risk of jaundice requiring phototherapy (OR 4.27, 95% CI: 1.98-121, p < 0.01). Day four TSB values above 180 µmol/L predicted the need for phototherapy with 86% sensitivity and 80% specificity. The findings were similar across both male and female infants with G6PD deficiency.

CONCLUSION

G6PD-deficient infants with day four TSB levels of >180 µmol/L (10.5 mg/dL) and associated ABO blood group incompatibility have a higher risk of requiring phototherapy in the first week of life and should be closely monitored.

Glucose-6-Phosphate Dehydrogenase Deficiency and Neonatal Hyperbilirubinemia: Insights on Pathophysiology, Diagnosis, and Gene Variants in Disease Heterogeneity

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a prevalent condition worldwide and is caused by loss-of-function mutations in the G6PD gene. Individuals with deficiency are more susceptible to oxidative stress which leads to the classical, acute hemolytic anemia (favism). However, G6PD deficiency in newborn infants presents with an increased risk of hyperbilirubinemia, that may rapidly escalate to result in bilirubin induced neurologic dysfunction (BIND). Often with no overt signs of hemolysis, G6PD deficiency in the neonatal period appears to be different in the pathophysiology from favism. This review discusses and compares the mechanistic pathways involved in these two clinical presentations of this enzyme disorder. In contrast to the membrane disruption of red blood cells and Heinz bodies formation in favism, G6PD deficiency causing jaundice is perhaps attributed to the disruption of oxidant-antioxidant balance, impaired recycling of peroxiredoxin 2, thus affecting bilirubin clearance. Screening for G6PD deficiency and close monitoring of affected infants are important aspects in neonatal care to prevent kernicterus, a permanent and devastating neurological damage. WHO recommends screening for G6PD activity of all infants in countries with high prevalence of this deficiency. The traditional fluorescent spot test as a screening tool, although low in cost, misses a significant proportion of cases with moderate deficiency or the partially deficient, heterozygote females. Some newer and emerging laboratory tests and diagnostic methods will be discussed while developments in genomics and proteomics contribute to increasing studies that spatially profile genetic mutations within the protein structure that could predict their functional and structural effects. In this review, several known variants of G6PD are highlighted based on the location of the mutation and amino acid replacement. These could provide insights on why some variants may cause a higher degree of phenotypic severity compared to others. Further studies are needed to elucidate the predisposition of some variants toward certain clinical manifestations, particularly neonatal hyperbilirubinemia, and how some variants increase in severity when co-inherited with other blood- or bilirubin-related genetic disorders.

The relationship between hyperbilirubinemia and the promoter region and first exon of UGT1A1 gene polymorphisms in Vietnamese newborns

BACKGROUND

To investigate the relationship between unexplained indirect hyperbilirubinemia of Vietnamese newborns and the polymorphism of the promoter TATA box and exon 1 of bilirubin uridine diphosphate glucuronosyltransferase (UGT1A1) gene.

METHODS

A total of 149 neonates were divided into the hyperbilirubinemia group (n = 99) and control group (n = 50). The gene polymorphisms of UGT1A1 gene in the two groups were detected by PCR and direct sequencing, which revealed the relationship between UGT1A1 polymorphism with neonatal hyperbilirubinemia of neonates. The types of UGT1A1 polymorphism in the hyperbilirubinemia group and the peak total serum bilirubin (PSB) levels with different genotypes were observed.

RESULTS

(1) (TA)7 insertion mutation, 211G>A, 189C>T, 190G>A, 378C>T and 686C>A were detected. (2) The allele frequency of 211G>A allele mutation was significantly different between the two groups (p < 0.05). (3) Logistic regression analysis showed that homozygosity and heterozygosity of 211G>A were both significantly associated with neonatal hyperbilirubinemia. (4) In the hyperbilirubinemia group, the peak total serum bilirubin level of 211G>A homozygous neonates was higher than that of the wild-type neonates (p < 0.05).

CONCLUSIONS

We noted that there was an association between neonates with unexplained indirect hyperbilirubinemia in Vietnam and the polymorphism of UGT1A1c.211G>A. In addition, the homozygous 211G>A polymorphism was related to the degree of hyperbilirubinemia.

IMPACT

Our article provided data on UGT1A1 polymorphism distribution in the Vietnamese population, which have not been reported yet. Our findings revealed that mutations in UGT1A1 gene are risk factors for unexplained hyperbilirubinemia in Vietnamese neonates. Our article will strengthen the cognition of neonatal jaundice at the genetic level in the pediatric field in Vietnam.

Combined Effects of UGT1A1 and SLCO1B1 Variants on Chinese Adult Mild Unconjugated Hyperbilirubinemia

The potential for genetic variation to cause adult unconjugated hyperbilirubinemia is increasingly being recognized. However, the cumulative effects of genetic variants have not been fully illuminated. The current study aimed to investigate the effects of uridine diphospho-glucuronosyl transferase 1A1 (UGT1A1) and/or solute carrier organic anion transporter family member 1B (SLCO1B) polymorphic variants and their combined effects on mild unconjugated hyperbilirubinemia in Chinese adults. Fourteen genetic variants in the UGT1A1 or SLCO1B gene were genotyped through sequencing in 148 adults with unconjugated hyperbilirubinemia and 158 healthy controls. Variants c.-3275T > G, (TA)₆>(TA)₇, c.211G > A or c.1091C > T within the UGT1A1 gene as well as c.521T > C within the SLCO1B1 gene appear to be genetic risk factors for inherited unconjugated hyperbilirubinemia. After adjusting for covariates, the results of multivariate logistic regressions revealed that odds ratios (ORs) [(with 95% confidence interval (CI)] of these five variants were 2.35 (95% CI: 1.37–4.01, p = 0.002), 2.38 (95% CI: 1.35–4.20, p = 0.003), 2.99 (95% CI: 1.71–5.21, p < 0.001), 7.60 (95% CI: 1.99–28.96, p = 0.003), and 2.54 (95% CI: 1.27–5.11, p = 0.009), respectively. The OR for unconjugated hyperbilirubinemia is positively correlated with the cumulative number of these five variants in adults. And the greater the number of genetic variations, the higher the total bilirubin level. Adults carrying diplotype 3/4 (homozygous c.-3275T > G and heterozygous (TA)₆>(TA)₇) had higher bilirubin levels than those with diplotypes 1/3 (heterozygous c.-3275T > G and (TA)₆>(TA)₇)) or 1/4 (heterozygous c.-3275T > G) (P < 0.05). Similarly, bilirubin levels in individuals with diplotype 2/4 (heterozygous c.-3275T > G and c.211G > A) were higher than adults carrying diplotypes 1/2 (heterozygous c.211G > A) or 1/4 (P < 0.001). For subjects with heterozygous or homozygous variant c.211G> A, as the number of c.521T > C alleles variation increased, the incidence of unconjugated hyperbilirubinemia increased, but it was not statistically significant. Our results indicate that variants of UGT1A1 and/or SLCO1B1 have combined effects on Chinese adult mild unconjugated hyperbilirubinemia.

SLCO1B1 c.388A > G variant incidence and the severity of hyperbilirubinemia in Indonesian neonates

OBJECTIVE

It has been established that genetic factors play a substantial role in the development of neonatal hyperbilirubinemia. The population of Indonesia and other Southeast Asian countries has similar, yet different genetic makeup compared to the rest of Asia. Aside from UGT1A1, variants of SLCO1B1 have also been known to contribute to the severity of neonatal hyperbilirubinemia in Asian populations. Since there has been no report on SLCO1B1 polymorphism in relation with hyperbilirubinemia in Indonesia, this study aims to explore incidence of SLCO1B1*1B polymorphism in Indonesia based on 3 hospitals from different provinces and population, and their association with hyperbilirubinemia severity.

METHODS

Our study included 88 neonates with mild and moderate-severe hyperbilirubinemia from 3 NICU in hospitals representing homogenous and heterogenous populations: Biak General Hospital Papua, Cipto Mangunkusumo Hospital (Jakarta), and M Yunus Hospital (Bengkulu). We collected samples between November 2016 and September 2017. DNA was obtained from existing samples of the patients from previous studies and were subjected to Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP). We analyzed the *1B variant located in exon 5 of SLCO1B1 with TaqI restriction endonuclease. Clinical, demographic, and laboratory data was also collected from medical records and parents' interviews.

RESULTS

The most dominant variant of SLCO1B1*1B in our population is the homozygous G/G (68.18%), followed by heterozygous A/G (26.14%), and wild type A/A (5.68%). The heterozygous A/G had an Odds Ratio (OR) of 0.73 (95% CI 0.10-5.2) and homozygous G/G with OR of 0.51 (95%CI 0.08-3.27), both were not significant. Genotypic distribution across the different centers were also similar and not significant. The significant risk factors for moderate-severe hyperbilirubinemia were the population the neonate originated from (p = < 0.001) and the delivery location (p = 0.001), while SLCO1B1*1B was not associated with the different severity of hyperbilirubinemia.

CONCLUSIONS

SLCO1B1*1B is not associated with higher bilirubin levels among neonates with hyperbilirubinemia in Indonesia. Further study is needed to find other potentially important genetic polymorphisms in the development of severe hyperbilirubinemia in Indonesia.

Effect of UDP-glucuronosyltransferase 1A1 activity on risk for developing Gilbert's syndrome

Variations at the six nucleotides -3279 (T > G), -53 (A[TA]₆ TAA > A[TA]₇ TAA), 211 (G > A), 686 (C > A), 1091 (C > T), and 1456 (T > G) in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene were determined in 178 Taiwanese patients with Gilbert's syndrome and in 200 healthy adults. Every subject was classified as a genotype depending on variation status of the six nucleotides in the UGT1A1 gene. The UGT1A1 activity for each genotype was calculated and then those genotypes were divided into 10 subgroups (Q1~Q10) according to their UGT1A1 activities, by using 10% as an interval. There were 24 genotypes observed, with UGT1A1 activity ranged 9%~100% of normal. There were two and six subjects with Gilbert's syndrome and none of healthy controls carrying genotypes in the Q1 and Q2 subgroups, respectively. The odds of developing Gilbert's syndrome were significantly higher for subjects carrying genotypes in the Q3, Q4, and Q5 subgroups than for those with genotype in the Q10 subgroup (odds ratios: 240.22, 59.80, and 14.67, respectively, P < .001 for each). Among the 178 patients of Gilbert's syndrome, serum bilirubin value was inversely correlated with UGT1A1 activity (r = -.306, P < .001). The sensitivity was 72.0% and the specificity was 90.5% by using UGT1A1 activity ≦40% of normal as the cut-off point to distinguish between healthy subjects and patients of Gilbert's syndrome. Our results demonstrate that UGT1A1 activity is certainly a determinate for serum bilirubin value and UGT1A1 activity ≦40% of normal is a proper risk factor for the development of Gilbert's syndrome.

Association between genetic polymorphism of heme oxygenase 1 promoter and neonatal hyperbilirubinemia: a meta-analysis

Objective: The association between a (GT)_n dinucleotide length polymorphism in the promoter region of heme oxygenase 1 (HMOX1) and the risk of neonatal hyperbilirubinemia remains controversial. This meta-analysis was, therefore, performed with aims to examine the correlation between the HMOX1 (GT)_n repeat length polymorphism and neonatal hyperbilirubinemia susceptibility.Materials and methods: We searched the databases including PubMed, Embase, Cochrane Library, China national knowledge infrastructure (CNKI), and Wanfang Data, with all reviewed studies published before 28 June 2018. After the evaluation of quality, we used RevMan to perform the meta-analyses. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the effect of HMOX1 gene promoter polymorphisms on the risk of neonatal hyperbilirubinemia.Results: Seven studies, involving 584 patients with neonatal hyperbilirubinemia and 1655 controls, were included. A statistically significant association was found between the HMOX1 (GT)_n repeat length polymorphism and risk of neonatal hyperbilirubinemia under the allele (allele S vs. allele L: OR = 1.81, 95% CI = 1.22-2.67, p = .003), recessive (genotype SS vs. genotypes LS + LL: OR = 1.38, 95% CI = 1.02-1.86, p = .04), dominant (genotypes SS + LS vs. LL: OR = 1.37, 95% CI = 1.01-1.76, p = .01), and homozygous genetic models (genotype SS vs. genotype LL: OR = 1.47, 95% CI = 1.02-2.11, p = .003), but not under the heterozygous genetic model. Interestingly, subgroup analysis revealed that the cutoffs of the S allele < 25 showed significant associations in any of the five genetic models (allele S vs. allele L: OR = 2.26, 95% CI = 1.68-3.05, p < .00001; genotype SS vs. genotypes LS + LL: OR = 2.56, 95% CI = 1.41-4.65, p = .002; genotypes SS + LS vs. genotype LL: OR = 1.82, 95% CI = 1.28-2.59, p = .0009; genotype SS vs. genotype LL: OR = 3.09, 95% CI = 1.50-6.36, p = .002; genotype LS vs. genotype LL: OR = 1.64, 95% CI = 1.11-2.42, p = .01); however, this association was not observed in the cutoffs of the S allele ≥25.Conclusion: The results of this study indicate that there is a significant association between the HMOX1 (GT)_n repeat length polymorphism and susceptibility to neonatal hyperbilirubinemia. Newborns carrying shorter (GT)_n repeats in the HMOX1 gene promoter may have a higher risk of neonatal hyperbilirubinemia.

Genetically Regulated Bilirubin and Risk of Non-alcoholic Fatty Liver Disease: A Mendelian Randomization Study

Mildly elevated serum bilirubin levels were reported to be associated with decreased risk of non-alcoholic fatty liver disease (NAFLD). Whether this is a causal relationship remains unclear. We tested the hypothesis that genetically elevated plasma bilirubin levels are causally related to reduce risk of NAFLD. A total of 403 eligible participants were enrolled. NAFLD was determined by liver ultrasonography. The uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene variants (UGT1A1^*6 and UGT1A1^*28) were genotyped through sequencing. We applied a Mendelian randomization approach to assess the effects of genetically elevated bilirubin levels on NAFLD. NAFLD was diagnosed in 19% of participants in our study (NAFLD = 76; Non-NAFLD = 327). The variants of UGT1A1^*28 and UGT1A1^*6 were strongly associated with increased total bilirubin (TB), direct bilirubin (DB), and indirect bilirubin (IB) levels (each P < 0.001). These two common variants explain 12.7% (TB), 11.4% (IB), and 10.2% (DB) of the variance in bilirubin levels, respectively. In logistic regression model, after multifactorial adjustment for sex, age, aminotransferase (ALT), white blood count (WBC), and body mass index (BMI), variant UGT1A1^*28 (OR = 1.39; 95%CI: 0.614–3.170; P = 0.43) and UGT1A1^*6 (OR = 1.64, 95%CI, 0.78–3.44; P = 0.19) genotypes were not significantly associated with the risk of NAFLD. Moreover, the plasma bilirubin level (TB, IB, and DB) were not significantly associated with the risk of NAFLD (P > 0.30). A Mendelian randomization analysis of the UGT1A1 variants suggests that bilirubin is unlikely causally related with the risk of NAFLD.

Identification of Genetic Risk Factors for Neonatal Hyperbilirubinemia in Fujian Province, Southeastern China: A Case-Control Study

To date, the genetic risk factors for neonatal hyperbilirubinemia remain unknown in Southeastern China. This case-control study aimed to identify the genetic risk factors for neonatal hyperbilirubinemia in Fujian, Southeastern China. A total of 286 hyperbilirubinemic newborns were enrolled as a case group, and 250 randomly selected newborns without jaundice or with a bilirubin level that was lower than the threshold required for phototherapy served as controls. The serum levels of total bilirubin, unconjugated bilirubin, and direct bilirubin were measured, and the common genetic loci in UGT1A1, OATP1B1, and HO-1 genes were genotyped. Higher incidence of ABO incompatibility and G6PD deficiency was detected in the case group compared to the control group (P < 0.01). There were significant differences in the frequencies of rs4148323 and rs1805173 genotypes between the case and control groups (P < 0.05). At the rs4148323 locus, the frequencies of GA heterozygotes and AA mutant homozygotes were higher in the case group than in the control group (P < 0.05), and at the rs1805173 locus, the frequencies of LS, MS, and SS genotypes were higher in the case group than in the control group (P < 0.05). A higher frequency of rs4148323 A allele and rs1805173 S allele was detected in the case group compared to the control group (P = 0). Additionally, multivariate logistic regression analysis identified that the mutant genotype of rs4148323 in the UGT1A1 gene, ABO incompatibility, G6PD deficiency, and SS genotype at rs1805173 locus of the HO-1 gene were genetic risk factors of neonatal hyperbilirubinemia. Our data demonstrate that G211 mutation in the UGT1A1 gene, ABO incompatibility, G6PD deficiency, and the SS genotype of the repeats in the promoter region of the HO-1 gene are risk factors for neonatal hyperbilirubinemia in Fujian, Southeastern China.

Clinical Significance of UGT1A1 Genetic Analysis in Chinese Neonates with Severe Hyperbilirubinemia

BACKGROUND

Neonatal hyperbilirubinemia is common in Asia, and the importance of genetically determined conditions has been recently recognized. The aim of this study was to assess the clinical utility of genetic testing in Chinese neonates with severe hyperbilirubinemia.

METHODS

Fifty-eight term infants with bilirubin level ≥ 20 mg/dL (342 μmol/L), and 65 controls were enrolled in the study. Variation status of UGT1A1, G6PD, and thalassemia genes in our study cohort was determined by direct sequencing or genotype assays.

RESULTS

Among these case infants, seven were confirmed with G6PD deficiency, four were heterozygous for α- or β-thalassemia, and forty-four were detected with at least one heterozygous UGT1A1 functional variant, including nine homozygous for UGT1A1 variation. As well as the predominant c.211G>A (Gly71Arg) variant, three UGT1A1 coding variants [c.1091C>T (Pro364Leu), c.1352C>T (pro451leu), and c.1456C>T (Tyr486Asp)] were observed in our case neonates. The results of multivariate logistic regressions, adjusted for covariates, revealed odds ratios for neonates who carried heterozygous, homozygous variation at nucleotide 211 of UGT1A1, and G6PD deficiency of 3.47 (1.26-9.55), 12.46 (1.09-142.7) ,and 12.87 (1.32-135.87) compared with those having the wild genotype and normal G6PD activity, respectively.

CONCLUSION

Besides G6PD-deficiency screening, UGT1A1 genetic analysis, and especially the UGT1A1*6(c.211G>A, p.Arg71Gly) polymorphism detection, may be taken into consideration for early diagnosis and treatment of severe hyperbilirubinemic newborns in southern China.

Neonatal jaundice and the immigrant population: A comparison study at a low-risk maternity ward in Norway

The aim of this study was to examine differences in distribution of neonatal jaundice by migration indicators. In this population-based study at the low-risk maternity ward at Baerum Hospital in Norway, 11,516 mother–child pairs were enrolled and divided into 7 groups by regions/country of origin. First registered live birth babies of mothers who gave birth between 1 January 2006 and 31 December 2010 were included. The study found that a total of 769 infants were treated for neonatal jaundice. Compared to Norwegians, infants born to mothers from East, Southeast and Central Asia had an increased risk and African infants had a decreased risk of neonatal jaundice. Jaundiced infants of African origin were more often transferred to neonatal intensive care units. Ethnicity is an important factor affecting the risk of neonatal jaundice requiring hospitalization in our clinic. To reduce this risk, parents should be adequately informed about the signs of neonatal jaundice requiring medical intervention.

Association between G6PD deficiency and hyperbilirubinemia in neonates: a meta-analysis

Hyperbilirubinemia is prevalent in newborns and multiple factors are responsible for the occurrence of neonatal hyperbilirubinemia. G6PD (Glucose-6-Phosphate Dehydrogenase) deficiency is recognized as one of the risk factors. However, many pediatricians did not take into account the probable effect of G6PD-deficiency when severe neonatal hyperbilirubinemia occurred. The aim of the present study was to perform a meta-analysis to investigate whether G6PD-deficiency increases the risk of hyperbilirubinemia and phototherapy in newborn. We searched PubMed and Embase databases for eligible articles according to explicit study inclusion and exclusion criteria. Risk ratios (RRs) and 95% confidence interval (CI) were selected as the evaluation indexes. Cochrane Q and I(2) test were utilized to assess the heterogeneity among studies. A total of five cohort studies were included in this meta-analysis. There were 21,585 participants enrolled in these studies including 877 newborns with hyperbilirubinemia and 261 newborns receiving phototherapy. Comparison of the incidence of hyperbilirubinemia in newborns with G6PD-deficiency to the ones with normal G6PD in each study yielded a pooled RR of 3.92 (95% CI, 2.13-7.20; P <.0001). The pooled RR of receiving phototherapy in G6PD-deficiency neonates is 3.01 (95% CI, 2.20-4.12; P <.0001) when compared to G6PD normal neonates. This study revealed a significant correlation between G6PD-deficiency and neonatal hyperbilirubinemia, as well as G6PD-deficiency and phototherapy. G6PD-deficient newborns have higher risk of hyperbilirubinemia and phototherapy than the ones with normal G6PD. Monitoring the level of G6PD in newborns is important for predicting the occurrence of hyperbilirubinemia.

Neonatal hemolysis and risk of bilirubin-induced neurologic dysfunction

The pathologic phenotype of severe hyperbilirubinemia in the newborn infant is primarily due to excessive bilirubin production and/or impaired conjugation, resulting in an increased bilirubin load. This may, in turn, increase an infant's risk for the development of bilirubin-induced neurologic dysfunction (BIND). The highest-risk infants are those with increased bilirubin production rates due to hemolysis. Several immune and non-immune conditions have been found to cause severe hemolysis, and these are often exacerbated in those infants with perinatal sepsis and genetic predispositions. Therefore, identification of these infants, with novel technologies, is paramount in reducing the incidence of BIND and the long-term neurologic sequelae for these at-risk infants.

Hyperbilirubinemia, hemolysis, and increased bilirubin neurotoxicity

Increased hemolysis in the presence of severe neonatal hyperbilirubinemia appears to augment the risk of bilirubin neurotoxicity. The mechanism of this intensifying effect is uncertain. In direct antiglobulin titer (DAT) positive, isoimmune hemolytic disease, the bilirubin threshold at which neurotoxicity occurs appears to be lower than in DAT-negative hyperbilirubinemia. In other hemolytic conditions, the hemolysis may simply facilitate the development of extremely high serum bilirubin levels. Whether the hemolytic process per se exerts an independent effect or whether a very rapid rise in serum bilirubin might lead to greater penetration of the blood-brain barrier is unclear. In this review, we survey the synergistic role of hemolysis associated with severe hyperbilirubinemia in the potentiation of bilirubin-induced neurotoxicity and suggest methods of identifying at-risk babies with increased hemolysis to allow for their increased surveillance.

Crigler-Najjar syndrome type II in a Chinese boy resulting from three mutations in the bilirubin uridine 5'-diphosphate-glucuronosyltransferase (UGT1A1) gene and a family genetic analysis

Background

The UGT1A1 gene encodes a responsible enzyme, UDP-glucuronosyltransferase1A1 (UGT1A1), for bilirubin metabolism. Many mutations have already been identified in patients with inherited disorders with unconjugated hyperbilirubinemia, such as Crigler-Najjar syndromes and Gilbert’s syndrome.

Case presentation

In this report, we presented a boy with intermittent unconjugated hyperbilirubinemia, whose genetic analysis showed a new compound heterozygote determined by three mutations, c.211G > A (p.G71R), c.508_510delTTC (p.F170-) and c.1456 T > G (p.Y486D) in the hotspot regions of the UGT1A1 gene (exons 1 and 5) in Asian populations, presenting a genotype compatible with clinical picture of CNS-II. The family genetic analysis confirmed the origin of these mutations.

Conclusion

UGT1A1 gene analysis should be performed in all cases with unexplained unconjugated hyperbilirubinemia. The description of patients with peculiar genotypes especially including family analysis could help explain the relationship between the genotype and phenotype,it is helpful for clinicians to predict the outcome of the patients.

Multiple variants in UGT1A1 gene are factors to develop indirect hyper-bilirubinemia

Most Taiwanese patients with hyper-bilirubinemia have genetic abnormalities in the uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene beyond the variants in the TATA box upstream of UGT1A1 associated with Gilbert's syndrome. To investigate the role of UGT1A1 in the pathogenesis of indirect hyper-bilirubinemia, we prospectively studied 97 consecutive patients with indirect hyper-bilirubinemia for genotypes of promoter [(TA)6TAA6, (TA)7TAA7] and coding region [nucleotide (nt)-211, nt-686, nt-1,091 and nt-1,456] of UGT1A1. Thirty-six of the patients (45.6%) were found to have Gilbert's syndrome with 7/7 genotype; among them, 14 also carried variants at nt-686. Forty-two patients (43.3%) had the 6/7 genotype; among them, 36 patients were found to have one or more variants in the coding region. Patients with higher serum total bilirubin are associated with higher likelihood of carrying Gilbert's syndrome genotype: 60.0% (P=0.007) patients with serum total bilirubin level ≥2.5 mg/dL carried the Gilbert's syndrome genotype, while only 23.9% of patients with serum total bilirubin level <2.5 mg/dL carry the same genotype (P=0.0006). Forty-one of the 61 non-Gilbert's patients had one homogenous variants or two or more heterozygous variants in UGT1A1. Further studies are necessary to confirm the role of one homo-zygous variant or two or more hetero-zygous variants in UGT1A1 gene as factors for indirect hyper-bilirubinemia.

Identifying term breast-fed infants at risk of significant hyperbilirubinemia

BACKGROUND

The aim of this study was to establish a model to identify term breast-fed infants who are at risk of developing significant neonatal hyperbilirubinemia.

METHODS

A prospective study was designed to investigate the effects of birth weight, mode of delivery, cephalohematoma, glucose-6-phosphate dehydrogenase (G6PD) deficiency, predischarge total serum bilirubin, variant uridine 5'diphospho-glucuronosyltransferase 1A1 (UGT1A1) gene, and hepatic solute carrier organic anion transporter 1B1 (SLCO1B1) gene on significant hyperbilirubinemia in term breast-fed neonates. Significant hyperbilirubinemia was defined as a bilirubin level exceeding the hour-specific phototherapy treatment threshold recommended by the American Academy of Pediatrics in 2004.

RESULTS

Of 240 exclusively breast-fed term neonates, 26 (10.8%) had significant hyperbilirubinemia. The predischarge total serum bilirubin on the third day (odds ratio (OR) = 2.63; 95% confidence interval (CI): 1.87-3.70; P < 0.001) and the variant UGT1A1 gene at nucleotide 211 (OR = 5.00; 95% CI: 1.08-23.03; P < 0.05) were significant risk factors. The area under the receiver operating characteristic (ROC) curve of the predictive probability was 0.964 (95% CI: 0.932-0.984; P < 0.0001).

CONCLUSION

Combining the total serum bilirubin on the third day and the variant UGT1A1 gene at nucleotide 211 can predict hyperbilirubinemia well in term breast-fed infants.

Hyperbilirubinemia in healthy newborns born to immigrant mothers from southeastern Asia compared to Italian ones

OBJECTIVE

To compare the characteristics of jaundice and hyperbilirubinemia in the newborn population of both immigrant and Italian mothers.

METHODS

The authors studied a group of 1,680 infants born at "A. Gemelli" hospital during 1 y. All were with appropriate weight for gestational age, weighting more than 2,500 g, born to low-risk pregnancy. Maternal ethnicity, clinically evident jaundice (that is total serum bilirubin (TSB) > 7 mg/dL), hyperbilirubinemia (TSB > 12 mg/dL), the duration of hospital stay and their need of phototherapy were evaluated.

RESULTS

In infants born to Asian mothers, hyperbilirubinemia was significantly more frequent (48.8 % vs. 26.5 %, p = 0.003) and they reached mean TSB peak significantly later (86.5 ± 38.5 vs. 74.5 ± 20.6 h, P = 0.0001) compared with Italian infants. The average length of hospitalization of infants of Asian and Latin American mothers is significantly longer compared to Italian newborns (4.5 ± 1.9 vs. 3.6 ± 1.1, p <0.0001 and 4.2 ± 1.6 vs. 3.6 ± 1.1, p = 0.0004). With regard to the use of phototherapy, and to its duration, there are no significant differences between the populations studied.

CONCLUSIONS

Having studied all infants at low risk, the greater length of hospitalization is due to later peak and the higher frequency of jaundice in newborns of immigrant mother, especially in Asia. Therefore, as it happens to the Italian newborns, it would be desirable to build forecasting nomograms in these populations, to reduce the length of hospitalization and facilitate protected discharge.

Risk of hyperbilirubinemia in breast-fed infants

OBJECTIVE

To investigate the risk factors for hyperbilirubinemia in infants who are exclusively breast-fed.

STUDY DESIGN

A prospective study was conducted to investigate the effects of birth body weight, sex, mode of delivery, glucose-6-phosphate dehydrogenase (G6PD) deficiency, variant UDP-glucuronosyltransferase 1A1 (UGT1A1) gene, and hepatic solute carrier organic anion transporter 1B1 (SLCO1B1) gene on hyperbilirubinemia in neonates who were breast-fed. Hyperbilirubinemia was diagnosed when a full term neonate had a bilirubin level ≧15.0 mg/dL (256.5 μM) in serum at 3 days old. The polymerase chain reaction-restriction fragment length polymorphism method was used as a means of detecting the known variant sites in the UGT1A1 and SLCO1B1 gene.

RESULTS

Of 252 infants born at term who were exclusively breast-fed, 59 (23.4%) had hyperbilirubinemia. The significant risk factors were a variant nucleotide 211 in UGT1A1 (2.48; 95% CI, 1.29 to 4.76; P = .006), G6PD deficiency (12.24; 95% CI, 1.08 to 138.62; P < .05), and vaginal delivery (3.55; 95% CI, 1.64 to 7.66; P < .001).

CONCLUSION

Breast-fed neonates who are 211 variants in the UGT1A1, G6PD deficiency, and vaginal delivery are at high-risk for hyperbilirubinemia.

211 G to a variation of UDP-glucuronosyl transferase 1A1 gene and neonatal breastfeeding jaundice

Breastfeeding jaundice is a common problem in neonates who were exclusively breastfed, but its pathogenesis is still unclear. The uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) gene polymorphism was shown to contribute to the development of neonatal hyperbilirubinemia. We hypothesize that the variation of UGT1A1 gene may contribute to neonatal breastfeeding jaundice. We prospectively enrolled 688 near-term and term infants who were exclusively breastfed (BF group) or were supplemented by infant formula partially (SF group) before onset of hyperbilirubinemia. Genotyping of the promoter and exon1 of UGT1A1 was performed in all neonates. Neonates in BF group had a significantly higher maximal body weight loss ratio, peak bilirubin level, and a greater incidence of hyperbilirubinemia than those in SF group. Neonates with nucleotide 211 GA or AA variation in UGT1A1 genotypes had higher peak serum bilirubin levels and higher incidence of hyperbilirubinemia than WTs (GG). This phenomenon was only seen in BF group but not in SF group when subset analysis was performed. This suggests that neonates who carry the nucleotide 211 GA or AA variation within coding region in UGT1A1 gene are more susceptible to develop early-onset neonatal breastfeeding jaundice.

Glucose-6-phosphate dehydrogenase deficiency and severe neonatal hyperbilirubinemia: a complexity of interactions between genes and environment

Glucose-6-phosphate dehydrogenase deficiency is a commonly occurring genetic condition, likely to be encountered today in virtually any corner of the globe. Sudden episodes of hemolysis associated with the condition may result in exponential increases in serum total bilirubin concentrations to levels at which bilirubin-induced neurologic damage may occur. The hyperbilirubinemia is the result of complex interactions between genes and environment. Neonatal screening programs coupled with parental and medical caretaker education may be successful in limiting the severity of disease.

A polymorphic mutation, c.-3279T>G, in the UGT1A1 promoter is a risk factor for neonatal jaundice in the Malay population

The uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene encodes the enzyme responsible for bilirubin glucuronidation. To evaluate the contribution of UGT1A1 promoter mutations to neonatal jaundice, we determined the genotypes of c.-3279T>G, c.-3156G>A, and A(TA)7TAA in Malay infants with neonatal jaundice (patients) and in infants without neonatal jaundice (controls). In our population study, only c.-3279T>G was associated with neonatal jaundice. The genotype distributions between both groups were significantly different (p = 0.003): the frequency of homozygosity for c.-3279G was much higher in patients than those in controls. Allele frequency of c.-3279G was significantly higher in patients than those in controls (p = 0.006). We then investigated changes in transcriptional activity because of c.-3279T>G. Luciferase reporter assay in HepG2 cells demonstrated that transcriptional activity of the c.-3279G allele was significantly lower than that of the c.-3279T allele in both the absence and presence of bilirubin. Luciferase reporter assay in COS-7 cells elucidated that c.-3279T>G modified the synergistic effects of the nuclear factors associated with transcriptional machinery. In conclusion, the c.-3279T>G mutation in the UGT1A1 promoter is a genetic risk factor for neonatal jaundice.

Prolonged unconjugated hyperbiliriubinemia in breast-fed male infants with a mutation of uridine diphosphate-glucuronosyl transferase

OBJECTIVE

To test the hypothesis that a mutation in uridine diphosphate-glucuronosyl transferase 1A1 (UGT1A1) gene of breast-fed infants is a contributory factor to prolonged unconjugated hyperbilirubinemia.

STUDY DESIGN

Of 125 breast-fed term infants, 35 infants had prolonged unconjugated hyperbilirubinemia; another 90 breast-fed neonates without prolonged jaundice were control infants. The polymerase chain reaction-restriction fragment length polymorphism method was used to detect the known variant sites (promoter area, nucleotides 211, 686, 1091, and 1456) of the UGT1A1 gene.

RESULTS

Of 35 breast-fed infants with prolonged unconjugated hyperbilirubinemia, 29 had at least 1 mutation of the UGT1A1 gene. Variation at nucleotide 211 was most common. The percentages of the neonates carrying the variant nucleotide 211 were significantly different between the prolonged hyperbilirubinemia group and control neonates. Male breast-fed infants had a higher risk than female infants for prolonged hyperbilirubinemia.

CONCLUSIONS

Male breast-fed neonates with a variant nucleotide 211 in UGT1A1 have a high risk for developing prolonged hyperbilirubinemia.

Variants in the UGT1A1 gene and the risk of pediatric nonalcoholic fatty liver disease

OBJECTIVE

Oxidative stress is increased in nonalcoholic fatty liver disease (NAFLD). Variants in the UGT1A1 gene contribute to increased bilirubin levels, and bilirubin can act as an antioxidant. We hypothesize that variant UGT1A1 genotypes reduce the risk for NAFLD development.

METHODS

Two hundred thirty-four obese children 6 to 13 years of age were recruited. NAFLD was determined through liver ultrasonography. The UGT1A1 genotypes UGT1A1*6 and UGT1A1*28 were detected. We assessed the effects of UGT1A1 genotypes on pediatric NAFLD.

RESULTS

In total, 12% of the obese children had NAFLD. The subjects with NAFLD had lower serum total bilirubin levels (0.25 +/- 0.30 mg/dL) than did those without NAFLD (0.36 +/- 0.38 mg/dL; P = .021). With conditioning on the effects of age- and gender-adjusted BMI, waist/hip ratio, and adiponectin levels, variant UGT1A1*6 genotypes were a protecting factor for NAFLD, with an estimated adjusted odds ratio of 0.31 (95% confidence interval: 0.11-0.91; P = .033), but variant UGT1A1*28 genotypes were not significantly associated with the occurrence of NAFLD.

CONCLUSIONS

Variant UGT1A1*6 genotypes are associated with a lower risk of NAFLD in obese Taiwanese children. The UGT1A1 genotype is a new risk factor for pediatric NAFLD.

Complex multifactorial nature of significant hyperbilirubinemia in neonates

OBJECTIVE

To determine whether glucose-6-phosphate dehydrogenase (G6PD), uridine-diphosphoglucuronosyltransferase 1A1 (UGT1A1), and hepatic solute carrier organic anion transporter 1B1 (SLCO1B1) gene variants occur at greater frequency in neonates with significant hyperbilirubinemia.

METHODS

Infants with gestational ages of >or=37 weeks and ages of <7 days were studied. Case subjects had >or=1 bilirubin level above the 95th percentile (high-risk zone), whereas control subjects had bilirubin levels of <40th percentile (low-risk zone) at study entry.

RESULTS

A total of 153 case subjects (median bilirubin level: 15.7 mg/dL) and 299 control subjects (median bilirubin level: 4.6 mg/dL) were evaluated. There were no statistical differences in the frequencies of G6PD, UGT1A1, and SCLO1B1 gene variants between case and control subjects (G6PD: 5.2% vs 3.3%; UGT1A1: 14.4% vs 9.4%; SLCO1B1: 73.2% vs 73.6%). However, coexpression of the G6PD African A- mutation with UGT1A1 and/or SLCO1B1 variants was seen more frequently for case subjects. Case subjects more often demonstrated >or=2 factors contributing to hyperbilirubinemia, including ABO blood group heterospecificity in which the mother had blood group O (47.7% vs 11.4%), positive direct Coombs test results (33.3% vs 4%), sibling treated with phototherapy (16.3% vs 5.4%), maternal circulating blood group antibodies (10.5 vs 0.7%), maternal diabetes mellitus (13.1% vs 6.4%), and maternal East Asian ethnicity (6.5% vs 1.3%).

CONCLUSIONS

Clinical contributors to hyperbilirubinemia were identified more frequently for case subjects but individually G6PD, UGT1A1, and SLCO1B1 variants were not. Coexpression of the G6PD African A- mutation with UGT1A1 and SLCO1B1 variants was seen more often for case subjects.

Homozygous variant of UGT1A1 gene mutation and severe neonatal hyperbilirubinemia

BACKGROUND

The aim of the present study was to compare, in a case-control study, the prevalence of nucleotide 211 guanine to adenine (G-->A) mutation of uridine diphosphoglucuronosyl transferase (UGT1A1) gene in Malaysian Chinese newborns with and without severe hyperbilirubinemia (total serum bilirubin >250 micromol/L during first 48 h of life or > or =300 micromol/L thereafter), and to determine whether this mutation was a significant risk factor associated with severe hyperbilirubinemia.

METHODS

Seventy-four term infants of Chinese descent admitted with severe hyperbilirubinemia were recruited. Infants without severe hyperbilirubinemia (n = 125) were randomly selected from among healthy Chinese term infants. UGT1A1 nucleotide 211 polymorphism was assayed using the Taqman single nucleotide polymorphism genotyping method. Using gestational age, types of feeds, G6PD mutation, G6PD enzyme levels, and UGT1A1 gene mutation status as independent variables, logistic regression analysis was carried out to determine the significant risk factors associated with severe hyperbilirubinemia.

RESULTS

UGT1A1 gene mutation was significantly more common among hyperbilirubinemic infants (39.2%) than controls (25.6%; P = 0.04). Gestational age (adjusted odds ratio [OR], 0.7; 95% confidence intervals [CI]: 0.5-0.9; P = 0.01), G6PD mutation (adjusted OR, 7.2; 95%CI: 2.7-19.0; P < 0.0001), exclusive breast-feeding (adjusted OR, 11.7; 95%CI: 2.7-49.9; P = 0.001), and homozygous variant of UGT1A1 gene mutation (adjusted OR, 32.2; 95%CI: 3.8-273.2; P = 0.001) were significant risk factors. Heterozygous variant of UGT1A1 gene mutation, actual levels of G6PD enzyme, and mixed feeding were not.

CONCLUSION

Homozygous variant of nucleotide 211 G-->A mutation of UGT1A1 gene is a significant risk factor associated with severe hyperbilirubinemia among Malaysian Chinese newborns.

Genetic polymorphisms in Thai neonates with hyperbilirubinemia

AIM

Polymorphisms of the UGT1A1 gene, SLCO1B1 gene and GST gene have been associated with significant hyperbilirubinemia. We would like to determine whether the variation of UGT1A1 gene, SLCO1B1 gene and GST gene may play a significant role in neonatal hyperbilirubinemia in Thai infants.

METHODS

Ninety-one study subjects (hyperbilirubinemic group) and 86 control subjects were studied.

RESULTS

The cause of neonatal hyperbilirubinemia could not be identified in 64 infants (70.3%), ABO blood group incompatibility in 14.3% and Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency in 8.8%. In the hyperbilirubinemic group, 23 of 91 (25.3%) infants demonstrated variant of UGT1A1 at nucleotides (nt) 211 as compared to 6 of 86 (7%) in the control group (p = 0.001). There were no significant differences between groups in the variants UGT1A1 at nt 686, SLCO1B1 gene at nt 388, 463 and the GST gene. Male infants with G-6-PD deficiency were associated with hyperbilirubinemia (21.2% vs. 4.8% in the control group) with an odds ratio (OR) of 5.37 (p = 0.02). The relationship between G-6-PD and variant in UGT1A1 gene at nt 211 could not be determined.

CONCLUSION

Thai infants with variant in the UGT1A1 at nt 211 or with G-6-PD deficiency are at higher risk for developing neonatal hyperbilirubinemia.

Identification of neonates at risk for hazardous hyperbilirubinemia: emerging clinical insights

Hyperbilirubinemia is the most common condition requiring evaluation and treatment in neonates. Identifying among all newborns those few at risk to develop marked hyperbilirubinemia is a clinical challenge. Clinical, epidemiologic, and genetic risk factors associated with severe hyperbilirubinemia include late preterm gestational age, exclusive breastfeeding, glucose-6-phosphate dehydrogenase deficiency, ABO hemolytic disease, East Asian ethnicity, jaundice observed in the first 24 hours of life, cephalohematoma or significant bruising, and history of a previous sibling treated with phototherapy. It is increasingly apparent that the etiopathogenesis of severe hyperbilirubinemia is often multifactorial, and emerging evidence suggests that combining risk factor assessment with measurement of predischarge total serum or transcutaneous bilirubin levels will improve hyperbilirubinemia risk prediction.

Coexpression of gene polymorphisms involved in bilirubin production and metabolism

OBJECTIVE

The potential for genetically determined conditions to modulate the risk for developing neonatal hyperbilirubinemia is increasingly being recognized. The aims of this investigation were to (1) develop genotyping assays for an expanded panel of mutations and polymorphisms across 3 genes that are involved in bilirubin production and metabolism (glucose-6-phosphate dehydrogenase [G6PD], uridine diphosphate glucuronosyl transferase 1A1 [UGT1A1], and organic anion transporter polypeptide 1B1 [OATP1B1]) and (2) determine their allele frequencies in 450 anonymous DNA samples of US residents with ancestry from all of the major regions of the world.

METHODS

Genotyping assays were developed on the basis of allele-specific hybridization and melting peak analysis of the probe set and the match or mismatch template. Allele frequencies and the complexity of coinheritance of multiple genetic variants across G6PD, UGT1A1, and OATP1B1 genes in DNA samples from the DNA Polymorphism Discovery Resource of the National Human Genome Research Institute were determined by using this expanded panel.

RESULTS

Genetic polymorphisms of the UGT1A1 promoter, specifically the T-3279G phenobarbital responsive enhancer module and the (thymidine-adenine)(7) dinucleotide repeat TATAA box variants, were common. Similarly, OATP1B1 coding sequence gene variants were frequently observed. Moreover, in more than three quarters of the samples, >or=2 variants were detected, reflecting a high degree of polymorphism coexpression across these genes, including those who carried the African A(-) G6PD mutation.

CONCLUSIONS

We conclude that this expanded panel of mutations and polymorphisms can serve as an effective instrument to study the genetic architecture of hyperbilirubinemia and speculate an important role for genetic polymorphism coinheritance in determining hyperbilirubinemia risk in newborns.

Higher infection of dengue virus serotype 2 in human monocytes of patients with G6PD deficiency

The prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency is high in Asia. An ex vivo study was conducted to elucidate the association of G6PD deficiency and dengue virus (DENV) infection when many Asian countries are hyper-endemic. Human monocytes from peripheral mononuclear cells collected from 12 G6PD-deficient patients and 24 age-matched controls were infected with one of two DENV serotype 2 (DENV-2) strains-the New Guinea C strain (from a case of dengue fever) or the 16681 strain (from a case of dengue hemorrhagic fever) with a multiplicity of infection of 0.1. The infectivity of DENV-2 in human monocytes was analyzed by flow cytometry. Experimental results indicated that the monocytes of G6PD-deficient patients exhibited a greater levels of infection with DENV-2 New Guinea C strain than did those in healthy controls [mean+/-SD:33.6%+/-3.5 (27.2% approximately 39.2%) vs 20.3%+/-6.2 (8.0% approximately 30.4%), P<0.01]. Similar observations were made of infection with the DENV-2 16681 strain [40.9%+/-3.9 (35.1% approximately 48.9%) vs 27.4%+/-7.1 (12.3% approximately 37.1%), P<0.01]. To our knowledge, this study demonstrates for the first time higher infection of human monocytes in G6PD patients with the dengue virus, which may be important in increasing epidemiological transmission and perhaps with the potential to develop more severe cases pathogenically.

Cord blood bilirubin level in relation to bilirubin UDP-glucuronosyltransferase gene missense allele in Chinese neonates

AIM

To investigate bilirubin UDP-glucuronosyltransferase (UGT1A1) gene allele in healthy Chinese neonates, their cord bilirubin level and the subsequent hyperbilirubinemia to determine relationships among them.

METHODS

Cord blood of 48 neonates was obtained to determine the exon 1 of UGT1A1 gene, total serum bilirubin, albumin, glutamic-pyruvic transaminase (GPT), glutamic-oxalacetic transaminase (GOT) and haemoglobin (Hb) concentration. Neonatal jaundice was assessed by measurement of transcutaneous bilirubin (TCB) and serum bilirubin. Neonates were divided into two groups according to mutant or normal allele to compare the variables.

RESULTS

Nineteen infants had the nucleotide 211 G-->A allele, 3 had the heterozygous variation (686C-->A, 845 A-->T, 231G-->A). In the 211 A allele group, cord bilirubin was significantly higher than in the 211 G allele group (p = 0.034), but there were no differences in albumin (p = 0.678), GPT (p = 0.460), GOT (p = 0.440) and Hb (p = 0.886). The TCB (at 48, 96 h), the frequency of the hyperbilirubinemia and prolonged jaundice were also significantly higher in the 211 A allele group.

CONCLUSIONS

The UGT1A1 gene codon G71R allele is a risk factor for neonatal hyperbilirubinemia in the Chinese population. Its effect on bilirubin metabolism may present early on, as well as late in foetal life.

G6PD deficiency: the genotype-phenotype association

Deficiency of glucose-6-phosphate dehydrogenase is a very common X-linked genetic disorder though most deficient people are asymptomatic. A number of different G6PD variants have reached polymorphic frequencies in different parts of the world due to the relative protection they confer against malaria infection. People, usually males, with deficient alleles are susceptible to neonatal jaundice, and acute hemolytic anemia, usually during infection, after treatment with certain drugs or after eating fava beans. Very rarely de novo mutations can arise causing the more severe condition of chronic nonspherocytic hemolytic anemia. Altogether 160 different mutations have been described. The majority of mutations cause red cell enzyme deficiency by decreasing enzyme stability. The polymorphic mutations affect amino acid residues throughout the enzyme and decrease the stability of the enzyme in the red cell, possibly by disturbing protein folding. The severe mutations mostly affect residues at the dimer interface or those that interact with a structural NADP molecule that stabilizes the enzyme.

(TA)n UGT 1A1 promoter polymorphism: a crucial factor in the pathophysiology of jaundice in G-6-PD deficient neonates

Increased heme catabolism has been reported in glucose-6-phosphate dehydrogenase (G-6-PD)-normal neonates who were also homozygous for (TA)7/(TA)7 (UGT1A1*28) uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT) promoter polymorphism (Gilbert syndrome). As G-6-PD deficiency is associated with increased hemolysis, we hypothesized that in G-6-PD-deficient neonates who also have the (TA)7/(TA)7 UGT promoter genotype, steady-state hemolysis would be even further increased. Male G-6-PD-deficient neonates were sampled for plasma total bilirubin (PTB), blood carboxyhemoglobin corrected for inhaled carbon monoxide in ambient air (COHbc) (an index of heme catabolism), and UGT (TA)n promoter genotype determination and compared with previously published G-6-PD-normal neonates. Although COHbc values were higher in the G-6-PD-deficient than in the G-6-PD-normal cohorts (0.97 +/- 0.32% of total Hb (tHb) versus 0.76 +/- 0.19% of tHb, p < 0.001), PTB values were similar (9.2 +/- 3.4 mg/dL versus 8.9 +/- 3.0 mg/dL, respectively, p = 0.3). Within the G-6-PD-deficient group, although COHbc values were alike between the three UGT promoter genotypes, PTB was higher in the (TA)7/(TA)7 homozygotes (11.1 +/- 4.0 mg/dL) compared with (TA)6/(TA)7 heterozygotes (9.1 +/- 3.2 mg/dL, p = 0.03) and wild-type (TA)6/(TA)6 homozygotes (8.8 +/- 3.4 mg/dL, p = 0.02). In the steady state, similar rates of hemolysis, but increased PTB in the G-6-PD- deficient, (TA)7/(TA)7 homozygotes, imply that (TA)7/(TA)7, homozygosity is central to increased PTB.

Glucose-6-phosphate dehydrogenase deficiency in triplets of African-American descent

Despite the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in African Americans, the disorder maybe often overlooked as a diagnosis in the absence of overt signs of hemolysis in neonates with hyperbilirubinemia. We present a case report of anemia and prolonged hyperbilirubinemia due to G6PD deficiency in the absence of hemolysis in dichorionic, triamniotic, preterm triplets of African-American descent.

Taiwan experience suggests that RhD typing for blood transfusion is unnecessary in southeast Asian populations

BACKGROUND

The high frequency of RhD (D) antigen among Taiwanese persons (99.67%) often imposes unnecessary risks of under-transfusion on D- patients awaiting D- blood. Also because of the rare occurrence of anti-D among Taiwanese persons, routine pretransfusion D typing has been discontinued in the Mackay Memorial Hospital since 1988. This report is the retrospective evaluation of the outcome of abolishing RhD typing for Taiwanese.

STUDY DESIGN AND METHODS

More than 10 years of alloantibody data at Mackay Memorial Hospital Blood Bank were reviewed. The cases with anti-D were further used to analyze the potency of D antigen and to observe whether there were differences in the incidence of anti-D before and after discontinuation of routine D typing among Taiwanese individuals.

RESULTS

The incidence of anti-D before and after discontinuation of routine pretransfusion D typing has remained unchanged. The immunogenicity of D and "Mi(a)" in Taiwanese persons is found to be similar. In terms of opportunity for immunization, however, the "Mi(a)" antigen (phenotype frequency 7.3% in Taiwanese persons) has become the most important blood group antigen in Taiwan.

CONCLUSION

The results strongly support the exclusion of D typing from routine compatibility testing for individuals of Taiwanese origin. Because the low incidence of D- and relatively high incidence of "Mi(a)"+ phenotypes are common findings throughout southeast Asia, and because a population genetic study revealed that the Taiwanese people are genetically related to southern Asian populations, it is suggested that RhD typing for blood transfusion is unnecessary among southeast Asian populations.

Comparative genomics analysis of human sequence variation in the UGT1A gene cluster

Common polymorphisms within the human UGT1A gene locus are associated with irinotecan and tranilast toxicity. To uncover additional functional variation across this gene cluster, cross-species sequence comparisons were performed. Evolutionarily conserved segments (a total of 47.1 kb) were re-sequenced in 24 African-American, 24 European-American, and 24 Asian individuals, and 381 segregating sites (including 123 singletons) were identified. Highly conserved coding sites were less likely to be polymorphic than diverged sites (P<0.0001) but this pattern was not observed at non-coding sites (P=0.1025). Among coding variants, the distribution of those computationally predicted to affect function was skewed toward low frequencies. Some alleles occurred at similar frequencies in each population; others had wide disparities. Although strong linkage disequilibrium was detected among the hepatically expressed genes, the degree of linkage disequilibrium varied among populations. These results suggest that rare functional gene variants and inter-population variability must be considered in the interpretation of association studies between UGT1A and drug metabolism/toxicity phenotypes.

Effects of variant UDP-glucuronosyltransferase 1A1 gene, glucose-6-phosphate dehydrogenase deficiency and thalassemia on cholelithiasis

AIM: To test the hypothesis that the variant UDP-glucuronosyltransferase 1A1 (UGT1A1) gene, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and thalassemia influence bilirubin metabolism and play a role in the development of cholelithiasis.

METHODS: A total of 372 Taiwan Chinese with cholelithiasis who had undergone cholecystectomy and 293 healthy individuals were divided into case and control groups, respectively. PCR and restriction fragment length polymorphism were used to analyze the promoter area and nucleotides 211, 686, 1 091, and 1 456 of the UGT1A1 gene for all subjects and the gene variants for thalassemia and G6PD deficiency.

RESULTS: Variation frequencies for the cholelithiasis patients were 16.1%, 25.8%, 5.4%, and 4.3% for A(TA)6 TAA/A(TA)7TAA (6/7), heterozygosity within the coding region, compound heterozygosity, and homozygosity of the UGT1A1 gene, respectively. Comparing the case and control groups, a statistically significant difference in frequency was demonstrated for the homozygous variation of the UGT1A1 gene (P = 0.012, χ² test), but not for the other variations. Further, no difference was demonstrated in a between-group comparison of the incidence of G6PD deficiency and thalassemia (2.7% vs 2.4% and 5.1% vs 5.1%, respectively). The bilirubin levels for the cholelithiasis patients with the homozygous variant-UGT1A1 gene were significantly different from the control analog (18.0 ± 6.5 and 12.7 ± 2.9 μmol/L, respectively; P<0.001, Student’s t test).

CONCLUSION: Our results show that the homozygous variation in the UGT1A1 gene is a risk factor for the development of cholelithiasis in Taiwan Chinese.

Genetic factors related to unconjugated hyperbilirubinemia amongst adults

Some variations in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene are involved in the development of unconjugated hyperbilirubinemia. We hypothesize that other genetic factors may also be associated with this disease. A total of 227 adults with normal routine haematology and liver function (apart from bilirubin testing for which they revealed bilirubin > or = 25.7 micromol/l and unconjugated bilirubin/total bilirubin > or = 80%), and 235 sex- and age-matched controls, were recruited. All subjects were analysed for UGT1A1, glucose-6-phosphate dehydrogenase (G6PD) and organic anion transporter polypeptide 2 (OATP2) genotypes using polymerase chain reaction-restriction fragment length polymorphism. The results indicated that G6PD deficiency, variant UGT1A1 gene and variant OATP2 gene were risk factors for hyperbilirubinemia. The odds ratios (OR) (with 95% confidence interval) were 220.83 (34.68-1406.30), 73.61 (17.01-318.63), 45.15 (11.19-182.22), 15.46 (4.35-54.99) and 6.51 (1.83-23.09), respectively, for individuals featuring the common UGT1A1/OATP2 haplotypes homozygous/heterozygous, compound heterozygous/heterozygous, compound heterozygous/wild-type, heterozygous/heterozygous and heterozygous/wild-type variations amongst subjects with normal G6PD activity. Amongst the subjects with G6PD deficiency, the OR was 159.00 (24.57-1028.94) for individuals carrying variations in both UGT1A1 and OATP2 genes. The UGT1A1/OATP2 haplotypes homozygous/wild-type, homozygous/compound heterozygous and homozygous/homozygous for G6PD normal and variant/wild-type for G6PD deficient individuals were only observed in the case group, and not in the control group. Amongst hyperbilirubinemic adults, bilirubin values tended to parallel variation status of their haplotypes. Adults featuring certain haplotypes in UGT1A1, OATP2 and G6PD genes face a high risk of developing unconjugated hyperbilirubinemia.

Link between colorectal cancer and polymorphisms in the uridine-diphosphoglucuronosyltransferase 1A7 and 1A1 genes

AIM: To investigate the relationship between single nucleotide polymorphisms in the uridine-diphosphoglucurono-syltransferase (UGT) UGT1A7 and UGT1A1 genes and patients suffering from colorectal cancer (CRC).

METHODS: A case-control study was designed in order to investigate the genotypes of the UGT1A7 and UGT1A1 genes, which were identified by the polymerase chain reaction-restriction fragment length polymorphism (RFLP) method, for 268 CRC patients and 441 healthy controls.

RESULTS: The results of simple logistical regressions revealed odds ratios (ORs) of 1.97 (P<0.001), 1.91 (P<0.001), and 2.03 (P<0.001) for patients who carried the UGT1A7*1/*3 genotype, UGT1A7*3 allele, and variant-211 UGT1A1 allele. The interaction of UGT1A7*3 allele and variant-211 UGT1A1 allele produced an additive effect on the risk for the development of CRC [observed OR (2.34) greater than expected OR (1.59)]. For the 268 patients, the results of simple logistical regressions indicated that the OR of developing metastases was 4.90 (P<0.001) and 4.89 (P<0.001) for the individuals possessing UGT1A7*3 allele and variant-211 UGT1A1 allele, respectively. The results of multivariate logistical regressions confirmed these findings (OR = 2.51, P = 0.01; and OR = 2.71, P = 0.01, respectively). The interaction of these two variants resulted in an additive effect on the risk for metastases amongst patients [observed OR (6.83) greater than expected OR (4.56)].

CONCLUSION: In conclusion, carriage of the UGT1A7*3 allele, as well as variant-211 UGT1A1 allele represents a risk factor for the development of, and a determinant for, metastases associated with CRC patients.

Vigintiphobia revisited

In this review the historical tenets and evidence-based clinical research in support of a bilirubin exchange threshold of >20 mg/dL for the healthy term neonate are revisited. In addition, a hypothesis is ventured that recent cases of kernicterus are related in part to changes in population factors coupled with genetic predispositions that have unmasked an unappreciated potential for marked neonatal hyperbilirubinemia.

Molecular genetics of unconjugated hyperbilirubinemia in Taiwanese

In bilirubin metabolism, increased destruction of erythrocytes, defect in the function of organic anion transporter polypeptide 2 (OATP2) or UDP-glucuronosyltransferase 1A1 (UGT1A1) may result in unconjugated hyperbilirubinemia. Although glucose-6-phosphate dehydrogenase (G6PD) deficiency is known to be associated with the development of neonatal hyperbilirubinemia, it was observed that in neonates severe hyperbilirubinemia caused by G6PD deficiency, without associated polymorphisms in the UGT1A1 or the OATP2 gene, was preventable. Variations at the nucleotide (nt) 388 of OATP2 gene and nt-211 of UGT1A1 gene, were found to be a risk factor for severe hyperbilirubinemia amongst Taiwanese neonates, respectively. G6PD deficiency, variations at nts 388 and 521 of OATP2 gene, and variations at nt-211 and in the promoter area of UGT1A1 gene were reported to be the risk factors for the occurrence of mild hyperbilirubinemia amongst Taiwanese adults. The status of the haplotypes of G6PD, OATP2, and UGT1A1 genes affected the odds ratio and the bilirubin levels in the hyperbilirubinemic subjects. Moreover, carriage of the variant-211 UGT1A1 allele, as well as UGT1A7*3 allele, was demonstrated to represent a risk factor for the development of, and a determinant for, metastases associated with Taiwanese colorectal-cancer patients. Further investigation is warranted to evaluate this phenomenon.

Polymorphisms of uridine-diphosphoglucuronosyltransferase 1A7 gene in Taiwan Chinese

AIM: Single nucleotide polymorphisms (SNPs) of uridine-diphosphoglucuro-nosyltransferase 1A7 (UGT1A7) gene are associated with the development of orolaryngeal cancer, hepatocellular carcinoma, and colorectal cancer. We performed this research to establish the techniques for determining UGT1A7 gene and basic data of this gene for Taiwan Chinese.

METHODS: We collected blood samples from 112 healthy adults and 505 subjects carrying different genotypes of UGT1A1, and determined the promoter area and the entire sequence of UGT1A7 exon 1 by polymerase chain reaction. We designed appropriate primers and restriction enzymes to detect variant UGT1A7 genotypes found in the study subjects.

RESULTS: Six SNPs at nucleotides 33, 387, 391, 392, 622, and 756 within the coding region of UGT1A7 exon 1 were found. The incidence of UGT1A7 *1/*2 (N129R131W208/ K129K131W208) was predominant (35.7%) while that of UGT1A7 *3/*3 (K129K131R208/K129K131R208) was the least (2.7%). The allele frequency of UGT1A7*3, which exists in a considerable proportion of Caucasians (0.361) and Japanese (0.255), was identified only to be 0.152 in our study subjects. A novel variation at nucleotide -57 in the upstream was found, which was associated with SNPs at nucleotides 33, 387, 391, 392, and 622 in one of the variant haplotypes. The nucleotide changes at positions 387, 391, 392 and 756 were in linkage in another variant haplotype. The allele frequency of UGT1A7*3 was 0.018, 0.158, 0.242, 0.433, and 0.920 in subjects carrying wild, A(TA)₆TAA/A(TA)₇TAA, A(TA)₇TAA/A(TA)₇TAA, 211G/211A, and 211A/211A variants of UGT1A1 gene, respectively. By using natural or mutagenesis primers, we successfully detected the variations at nucleotides -57, 33, 387, and 622 with the restriction enzymes HpyCH4 IV, Taq I, Afl II, and Rsa I, respectively.

CONCLUSION: The results indicate that the allele frequencies of UGT1A7 gene in Taiwan Chinese are different from those in Caucasians and Japanese. Carriage of the nucleotide 211- variant UGT1A gene is highly associated with UGT1A7*3. The restriction-enzyme-digestion method for the determination of nucleotides -57 (or 33, or 622) and 387 can rapidly identify genotypes of UGT1A7 in an individual.

Risk factors for severe hyperbilirubinemia in neonates

The incidence of severe neonatal hyperbilirubinemia is higher in Asians than in whites. A case-control study was designed to investigate the effects of eight known risk factors [breast feeding, ABO incompatibility, premature birth, infection, cephalohematoma, asphyxia, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and variant UDP-glucuronosyltransferase 1A1 (UGT1A1) gene] and a suspicious analog [organic anion transporter 2 (OATP 2) gene] on severe hyperbilirubinemia in Taiwanese neonates. The 72 study subjects and 100 hospital control subjects consisted of neonates with peak serum bilirubin levels > or =342 microM and <256.5 microM, respectively. The PCR-restriction fragment length polymorphism method was applied to detect the UGT1A1, OATP 2, and G6PD genes. The results of multivariate logistic regressions, adjusted for covariates, revealed odds ratios (ORs) of 4.64 [95% confidence interval (CI): 2.25-9.57; p < 0.001], 3.36 (95% CI: 1.54-7.35; p=0.002), and 3.02 (95% CI: 1.30-6.99; p=0.010) for neonates who were fed with breast milk, and carry the variant UGT1A1 gene at nucleotide 211 and the variant OATP 2 gene at nucleotide 388, respectively. The ORs, adjusted for covariates, for the other six risk factors were not statistically significant. The ORs in neonates who had one, two, and three significant risk factors were 8.46 (95% CI: 2.75-34.48; p < 0.001), 22.0 (95% CI: 5.50-88.0; p < 0.001), and 88.0 (95% CI: 12.50-642.50; p < 0.001), respectively. In conclusion, neonates who carry the 211 and 388 variants in the UGT1A1 and OATP 2 genes, respectively, as well as feed with breast milk are at high risk to develop severe hyperbilirubinemia.

Glucose-6-phosphate dehydrogenase deficiency: a hidden risk for kernicterus

Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, a commonly occurring enzymatic defect, is an important risk factor in the pathogenesis of severe neonatal hyperbilirubinemia. Many of the recently reported cases of kernicterus, even in countries with a low overall incidence of the G-6-PD deficiency such as the United States and Canada, have been found to be enzyme deficient. In many cases the hyperbilirubinemia may be due to acute hemolysis precipitated by exposure to an identifiable chemical trigger, or to infection. In other cases the hemolysis may be mild, the hyperbilirubinemia being due to diminished bilirubin conjugation. An interaction between G-6-PD deficiency and promoter polymorphism for the gene encoding the bilirubin conjugating enzyme, UDP-glucuronosyltranferase 1A1, associated with Gilbert syndrome, has been implicated in the pathogenesis of hyperbilirubinemia. Neonates whose families originated in areas at high risk for G-6-PD deficiency should be vigilantly observed for jaundice. Phototherapy is the mainstay of treatment, with exchange transfusion being performed in those unresponsive to phototherapy. A high degree of physician awareness is essential in the identification and follow-up of these high-risk neonates.