Combined test for UGT1A1 -3279T-->G and A(TA)nTAA polymorphisms best predicts Gilbert's syndrome in Italian pediatric patients

Association of gallstone and polymorphisms of UGT1A1*27 and UGT1A1*28 in patients with hepatitis B virus-related liver failure

Genetic variation in UDP-glucuronosyltransferase 1A1 gene (UGT1A1) is a lithogenic risk factor for gallstone formation. This study aimed to assess genotype and allele frequencies of common UGT1A1 variants in patients with gallstone and hepatitis B virus (HBV)-related hepatic failure. This study enrolled 113 healthy individuals (CTRL), 54 patients with HBV infection (HBV), 134 patients with gallstone-free hepatic failure and HBV infection, and 34 patients with gallstone-related hepatic failure and HBV infection (GRHF). Peripheral venous blood samples were collected for genomic DNA isolation. Polymerase chain reaction amplification was carried out for UGT1A1, followed by direct sequencing. Analysis for genotype and allele frequencies of UGT1A1 variants (UGT1A1*6, UGT1A1*27, UGT1A1*28, and UGT1A1*60) was performed. The allele distributions of the four groups did not deviate from Hardy–Weinberg equilibrium. Allele (A) and genotype (CA) frequency distributions of UGT1A1*27 were significantly different between GRHF and CTRL, or between GRHF and HBV. GRHF and CTRL exhibited significant differences in allele (A) and genotype (CA) frequency distributions of UGT1A1*28. Linkage disequilibrium analysis suggested that haplotype G-G-[TA]7-T may be associated with gallstone in HBV-related hepatic failure. Our data reveal that UGT1A1*27 and UGT1A1*28 variants are significantly observed in patients with GRHF compared to healthy individuals.

Association of Neonatal Hyperbilirubinemia with UGT1A1 Gene Polymorphisms: A Meta-Analysis

Background

The results of studies on association between the polymorphisms in the coding region and the promoter of uridine diphosphateglucuronosyl transferase 1A1 (UGT1A1) and neonatal hyperbilirubinemia are controversial. This study aimed to determine whether the UGT1A1 gene polymorphisms of Gly71Arg and TATA promoter were significant risk factors associated with neonatal hyperbilirubinemia.

Material/Methods

The PubMed, Cochrane Library, and Embase databases were searched for papers that describe the association between UGT1A1 polymorphisms and neonatal hyperbilirubinemia. Summary odds ratios and 95% confidence intervals (CI) were estimated based on a fixed-effects model or random-effects model, depending on the absence or presence of significant heterogeneity.

Results

A total of 32 eligible studies and 6520 participants were identified. Among them, 24 studies focused on the association of neonatal hyperbilirubinemia with UGT1A1 Gly71Arg polymorphisms, and a significant difference was found for the comparison of AA vs. AG+GG (OR=3.47, 95% CI=2.29–5.28, P<0.0001). We included 19 studies on the association of neonatal hyperbilirubinemia with UGT1A1 TATA promoter polymorphism, which also found a statistically significant difference between 7/7 and 6/7 + 6/6 (OR=2.24, 95% CI=1.29–3.92, P=0.004).

Conclusions

This meta-analysis demonstrated that UGT1A1 polymorphisms (Gly71Arg and TATA promoter) significantly increase the risk of neonatal hyperbilirubinemia.

UGT1A1 sequence variants associated with risk of adult hyperbilirubinemia: a quantitative analysis

BACKGROUNDS AND AIMS

UDP-glucuronosyltransferase 1 A1 (UGT1A1) is an enzyme that transforms small lipophilic molecules into water-soluble and excretable metabolites. UGT1A1 polymorphisms contribute to hyperbilirubinemia. This study quantitatively associated UGT1A1 variants in patients with hyperbilirubinemia and healthy subjects.

METHODS

A total of 104 individuals with hyperbilirubinemia and 105 healthy controls were enrolled for genotyping and DNA sequencing UGT1A1 sequence variants, including the Phenobarbital Response enhancer module (PBREM) region, the promoter region (TATA box), and the 5 exons for quantitative association with hyperbilirubinemia.

RESULTS

Eleven UGT1A1 variants were revealed in the case and control subjects, four of which were novel coding variants. A variant of PBREM (UGT1A1*60) was found in 47.6% of the patients, a TA repeat motif in the 5-primer promoter region [A(TA)7TAA,UGT1A1*28] was found in 27.9% of the patients, and p.G71R (UGT1A1*6) was in 33.2% of the patients. For the healthy controls, the frequency of UGT1A1*60, UGT1A1*28 and UGT1A1*6 was 26.7%, 9.0% and 15.7%, respectively. Homozygous UGT1A1*28 and homozygous UGT1A1*6 were significantly associated with the risk of adult hyperbilirubinemia, with an odds ratio (OR) of 17.79 (95% CIs, 2.11-133.61) and 14.93 (95% CIs, 1.83-121.88), respectively. Quantitative analysis showed that sense mutation (including UGT1A1*6) and UGT1A1*28/*28, but not UGT1A1*60/*60 or UGT1A1*1/*28, was associated with increased serum total bilirubin (TB) levels. High linkage disequilibrium occurred between UGT1A1*60 and UGT1A1*28 (D'=0.964, r(2)=0.345).

CONCLUSIONS

This study identified four novel UGT1A1 coding variants, some of which were associated with increased serum TB levels. A quantitative approach to evaluate adult hyperbilirubinemia provides a more vigorous framework for better understanding of adult hyperbilirubinemia genetics.

Gilbert syndrome: the UGT1A1*28 promoter polymorphism as a biomarker of multifactorial diseases and drug metabolism

Gilbert syndrome belongs to the group of the most common human metabolic disorders and is characterized by an elevated level of bilirubin in blood serum. A polymorphism of the 5´ end of the UGT1A1 gene promoter, a homozygous insertion of TA pairs (genotype UGT1A1*28/*28), results in a decrease in bilirubin glucuronidation activity and therefore leads to an increase in the level of unconjugated bilirubin (hyperbilirubinemia). Genotyping the UGT1A1 promoter is an important step in the determination of the etiology of free hyperbilirubinemia of unknown origin. Molecular diagnosis enables avoiding invasive diagnostic procedures, such as liver biopsy, in establishing the appropriate diagnosis and prognosis, as well as in establishing the correct therapeutic procedures in a variety of diseases (e.g., chemotherapy or bone marrow transplantation). Moreover, the UGT1A1*28/*28 genotype has emerged as an important element in drug tolerance, as well as in multifactorial diseases, such as cancer. However, the role of this polymorphism is still not completely understood. In this review we have summarized current knowledge and attempted to propose directions for further research.

Impact of UGT1A1 gene variants on total bilirubin levels in Gilbert syndrome patients and in healthy subjects

The Gilbert syndrome is a benign form of unconjugated hyperbilirubinemia, mainly associated with alterations in UGT1A1 gene. This work investigated the effect of UGT1A1 variants on total bilirubin levels in Gilbert patients (n=45) and healthy controls (n=161). Total bilirubin levels were determined using a colorimetric method; molecular analysis of exons 1-5 and two UGT1A1 promoter regions were performed by direct sequencing and automatic analysis of fragments. Five in silico methods predicted the effect of new identified variants. A significant different allelic distribution, in Gilbert patients and in controls, was found for two promoter polymorphisms. Among patients, 82.2% were homozygous and 17.8% heterozygous for the c.-41_-40dupTA allele; in control group, 9.9% were homozygous and 43.5% heterozygous for this promoter variant, while 46.6% (n=75) presented the [A(TA)6TAA]. For the T>G transition at c.-3279 promoter region, in patients, 86.7% were homozygous and 13.3% heterozygous; in control group, 33.5% were homozygous for the wild type allele, 44.1% were heterozygous and 22.4% homozygous for the mutated allele. The two polymorphisms were in Hardy-Weinberg equilibrium in both groups. Sequencing of UGT1A1 coding region identified nine novel variants, five in patients and four in controls. In silico analysis of these amino acids replacements predicted four of them as benign and three as damaging. In conclusion, we demonstrated that total bilirubin levels are mainly determined by the TA duplication in the TATA-box promoter and by the c.-3279T>G variant. Alterations in the UGT1A1 coding region seem to be associated with increased bilirubin levels, and, therefore, with Gilbert syndrome.

Contribution of G71R mutation to Gilbert’s syndrome phenotype in a Greek patient: A case report

Gilbert’s syndrome is characterized by a benign indirect hyperbilirubinemia. It has often been underestimated and undiagnosed because of its mild symptoms; although it is not as rare as was once believed when its frequency was estimated using data originating from biochemical tests. Based on molecular techniques, the occurrence of Gilbert’s syndrome has changed, increasing to 10% in the Caucasian population. This molecular defect was described, by Bosma et al, in 1995, and affects the promoter region of the UGT 1A1 gene. In this case report, our aim is to present a new combination of two molecular defects in a Greek patient with Gilbert’s syndrome. A 13-year-old Greek girl was examined for Gilbert’s syndrome using molecular techniques, and an uncommon genotype was revealed comprising the rare mutation G71R in trans with A(TA)7TAA motif. The G71R mutation according to the literature, as well as our epidemiological data, is rare in Caucasians, while it is common in Asian populations. This is the first case study in the Greek population to report a new genotype for Gilbert’s syndrome manifestation in the Caucasian population.

Hereditary hyperbilirubinemia and its molecular diagnosis

Hereditary hyperbilirubinemia is caused by genetic defects in the enzymes that control bilirubin metabolism. It includes Gilbert syndrome (GS), Crigler-Najjar syndrome (CNS), Lucey-Driscoll syndrome (LDS), Dubin-Johnson syndrome (DJS), Rotor syndrome (RS) and progressive familial intrahepatic cholestasis (PFIC). This literature review covers the molecular basis of and laboratory detection methods for hereditary hyperbilirubinemia.

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.

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.

Haplotypes in the UGT1A1 gene and their role as genetic determinants of bilirubin concentration in healthy German volunteers

BACKGROUND

Genetic variations of UDP-glucuronyltransferase 1A1 (UGT1A1) influence the concentration of serum bilirubin. We investigated the association of four common polymorphisms including UGT1A1-53(TA)(n), and common haplotypes of the UGT1A1 gene with bilirubin levels in 218 Caucasian volunteers.

METHODS

Total bilirubin was measured in serum of 218 healthy Caucasian volunteers. Genotyping of four genetic variants was performed: UGT1A1-53(TA)(6/7), UGT1A1c.-3279T>G, UGT1A1c.-3156G>A, and UGT1A1c.211G>A. The association between polymorphisms/haplotypes and bilirubin levels were determined.

RESULTS

Minor allele frequencies were 0.36 for UGT1A1-53(TA)(7), 0.47 for c.-3279G, 0.33 for c.-3156A and 0.006 for c.211A. The three promoter polymorphisms were in close linkage disequilibrium. Common haplotypes were: -53(TA)(6)/c.-3279T/c.211G (frequency 0.530), -53(TA)(7)/c.-3279G/c.211G (frequency 0.365), and -53(TA)(6)/c.-3279G/c.211G (frequency 0.099). Male sex, UGT1A1-53(TA)(6/7) and the c.-3279GG variant were significantly associated with higher bilirubin concentrations.

CONCLUSIONS

Two UGT1A1 promoter polymorphisms (-53(TA)(6/7) and c.-3279T>G) and a common haplotype of the UGT1A1 gene are associated with serum bilirubin concentrations in Caucasians.

Variations in the UDP-glucuronosyltransferase 1A1 gene for the development of unconjugated hyperbilirubinemia in Taiwanese

INTRODUCTION

Results of several studies have indicated that the variation of c.-3279T>G in the UDP-glucuronosyltransferase (UGT)1A1 gene could be a further factor for the development of hyperbilirubinemia. However, this variant has not been reported in the Taiwanese population.

MATERIALS & METHODS

PCR-restriction fragment length polymorphism was utilized to determine variants at nucleotides -3279 (*60), -53 (*28) and 211 (*6) in the UGT1A1 gene for 178 Taiwanese hyperbilirubinemic patients and 200 controls.

RESULTS

A total of ten and nine diplotypes were observed in the hyperbilirubinemic patients and controls, respectively. Subjects possessing diplotypes of compound haplotypes (*60/*28, *60/*6, *1/*60 plus *1/*28 plus *1/*6); *60/*60; *60/*60 plus 1/*28 and *6/*6 were significantly related to hyperbilirubinemia development, with an odds ratio of 7.83-188.00 (p = 0.012 approximately <0.001). A subgroup possessing diplotypes of *60/*60 plus *28/*28 were only found in hyperbilirubinemic patients, not in the controls. Bilirubin concentration amongst these patients carrying a diplotype of *60/*60 plus *28/*28 (mean [SD]: 39.2 [10.77] micromol/l) was significantly higher than that in the diplotype subgroups of *60/*60 plus *1/*28 (30.4 [4.10] micromol/l) and *6/*6 (30.3 [3.08] micromol/l) (p = 0.046 and 0.034, respectively).

CONCLUSIONS

The c.-3279T>G variant is a further factor for the development of hyperbilirubinemia. Our results also demonstrate that possessing the *60/*60 plus *28/*28 diplotype in the UGT1A1 gene is a determinant of relatively higher bilirubin values amongst hyperbilirubinemic patients.

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.

UGT1A1 promoter polymorphism increases risk of nilotinib-induced hyperbilirubinemia

Nilotinib is a novel BCR-ABL inhibitor with significantly improved potency and selectivity over imatinib. In Phase I and Phase II clinical studies of nilotinib in patients with a variety of leukemias, infrequent instances of reversible, benign elevation of bilirubin were observed. Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) glucuronidates bilirubin in humans, and a polymorphism in the promoter of the gene that encodes it has been associated with hyperbilirubinemia during treatment with a number of drugs. Pharmacogenetic analysis of that TA-repeat polymorphism found an association between the (TA)7/(TA)7 genotype and risk of hyperbilirubinemia in Phase I patients with imatinib-resistant/intolerant chronic myeloid leukemia (CML) or relapsed/refractory Ph+ acute lymphoblastic leukemia (ALL); this result was replicated in two separate analyses of the chronic phase (CP) and accelerated phase (AP) CML arms of a Phase II study. As nilotinib is not known to be glucuronidated by UGT1A1, the combined impact of inhibition of UGT1A1 activity by nilotinib and genetic polymorphism is the most likely cause of the increased rate of hyperbilirubinemia.