Molecular genetic basis of Gilbert's syndrome

Interpreting elevated liver blood test results through a genetic lens: A genome-wide association study

BACKGROUND AND AIMS

Individuals with genetic polymorphisms in UGT1A1 exhibit bilirubin levels that belie their risk of liver disease (Gilbert's syndrome) but it is not known if this phenomenon extends to other common liver blood tests (LBTs).

METHODS

A genome-wide association analysis of 10 LBTs was conducted using the UK biobank. Polygenic scores (PGS) were created from discordant loci (e.g. loci associated with the LBT but not associated with cirrhosis morbidity risk). Participants were assigned to a low, intermediate or high PGS for each LBT. A high PGS approximates Gilbert's syndrome (i.e. elevated LBT without an analogous increase in disease risk). The prognostic significance of an 'elevated' LBT-and how this differs by PGS-was assessed through competing risk survival analysis.

RESULTS

This study included 157 005 and 166 871 participants for the discovery and validation phases, respectively. Elevated LBTs were more prevalent in the high versus low PGS group, yet the 10-year risk of cirrhosis morbidity was comparable. For example, in the low PGS group, 4.3% had an elevated gamma-glutamyltransferase (GGT) and the 10-year risk of cirrhosis morbidity was .45%. Conversely, in the high PGS group, 21.2% had an elevated GGT and the 10-year risk was .38%. Accordingly, the 10-year risk of cirrhosis morbidity for individuals with an elevated GGT was markedly different in the low vs. high group (4.2% vs. 1.2%; p < .001). Similar results were apparent for Fibrosis-4 index, total bilirubin, and platelet count.

CONCLUSION

Variability in LBTs is influenced by genetic polymorphisms that have a neutral effect on disease risk. These findings have implications for interpreting elevated LBTs in clinical practice.

Drug interaction with UDP-Glucuronosyltransferase (UGT) enzymes is a predictor of drug-induced liver injury

BACKGROUND AND AIMS

DILI frequently contributes to the attrition of new drug candidates and is a common cause for the withdrawal of approved drugs from the market. Although some noncytochrome P450 (non-CYP) metabolism enzymes have been implicated in DILI development, their association with DILI outcomes has not been systematically evaluated.

APPROACH AND RESULTS

In this study, we analyzed a large data set comprising 317 drugs and their interactions in vitro with 42 non-CYP enzymes as substrates, inducers, and/or inhibitors retrieved from historical regulatory documents using multivariate logistic regression. We examined how these in vitro drug-enzyme interactions are correlated with the drugs' potential for DILI concern, as classified in the Liver Toxicity Knowledge Base database. Our study revealed that drugs that inhibit non-CYP enzymes are significantly associated with high DILI concern. Particularly, interaction with UDP-glucuronosyltransferases (UGT) enzymes is an important predictor of DILI outcomes. Further analysis indicated that only pure UGT inhibitors and dual substrate inhibitors, but not pure UGT substrates, are significantly associated with high DILI concern.

CONCLUSIONS

Drug interactions with UGT enzymes may independently predict DILI, and their combined use with the rule-of-two model further improves overall predictive performance. These findings could expand the currently available tools for assessing the potential for DILI in humans.

The potential impact of CYP and UGT drug-metabolizing enzymes on brain target site drug exposure

Drug metabolism is one of the critical determinants of drug disposition throughout the body. While traditionally associated with the liver, recent research has unveiled the presence and functional significance of drug-metabolizing enzymes (DMEs) within the brain. Specifically, cytochrome P-450 enzymes (CYPs) and UDP-glucuronosyltransferases (UGTs) enzymes have emerged as key players in drug biotransformation within the central nervous system (CNS). This comprehensive review explores the cellular and subcellular distribution of CYPs and UGTs within the CNS, emphasizing regional expression and contrasting profiles between the liver and brain, humans and rats. Moreover, we discuss the impact of species and sex differences on CYPs and UGTs within the CNS. This review also provides an overview of methodologies for identifying and quantifying enzyme activities in the brain. Additionally, we present factors influencing CYPs and UGTs activities in the brain, including genetic polymorphisms, physiological variables, pathophysiological conditions, and environmental factors. Examples of CYP- and UGT-mediated drug metabolism within the brain are presented at the end, illustrating the pivotal role of these enzymes in drug therapy and potential toxicity. In conclusion, this review enhances our understanding of drug metabolism's significance in the brain, with a specific focus on CYPs and UGTs. Insights into the expression, activity, and influential factors of these enzymes within the CNS have crucial implications for drug development, the design of safe drug treatment strategies, and the comprehension of drug actions within the CNS. To that end, CNS pharmacokinetic (PK) models can be improved to further advance drug development and personalized therapy.

Incidental Scleral Icterus in an Adolescent Male With Nausea: Clinical Diagnosis of Gilbert Syndrome in the Pediatric Outpatient Setting

Gilbert syndrome is a condition of non-hemolytic hyperbilirubinemia without further sequelae or primary laboratory abnormalities. Gilbert syndrome represents the most common hereditary disorder of bilirubin metabolism and is frequently identified as the etiology of familial jaundice in clinical medicine. This disorder typically manifests as mild unconjugated hyperbilirubinemia of benign nature. The diagnosis of Gilbert syndrome entails clinical assessment corroborated by the laboratory findings above in the absence of hemolysis or other organic liver diseases. We report a case of a 17-year-old boy who presented to a pediatric clinic with dyspepsia for the management of digestive symptoms, with clinical findings of mild scleral icterus and laboratory findings of isolated indirect hyperbilirubinemia. This case is unique in its subtlety of presentation. It highlights to trainees and experienced physicians the importance of the physical examination and targeted laboratory workup to arrive at the diagnosis of Gilbert syndrome.

Effect of bilirubin and Gilbert syndrome on health: cohort analysis of observational, genetic, and Mendelian randomisation associations

Objectives

To compare associations between the Gilbert syndrome genotype in European populations, measured bilirubin concentrations, genetically predicted bilirubin using this genotype, and a wide range of health outcomes in a large cohort.

Design

Cohort study including observational, genetic, and Mendelian randomisation analyses.

Setting

22 centres across England, Scotland, and Wales in UK Biobank (2006-10), with replication in a national Finnish cohort (FinnGen).

Participants

463 060 participants in the UK Biobank were successfully genotyped for a genetic variant (rs887829) that is strongly associated with Gilbert syndrome and 438 056 participants had measured bilirubin concentrations with linked electronic health record data coded using the tenth edition of the International Classification of Diseases. Replication analyses were performed in FinnGen (n=429 209) with linked electronic health record data.

Main outcome measures

Odds ratios for the association between serum bilirubin concentrations, rs887829-T homozygosity (the risk genotype for Gilbert syndrome), genetically predicted bilirubin using rs887829-T allele carriage alone, and a wide range of health outcomes recorded in primary and secondary care.

Results

46 189 participants in UK Biobank (about 10%) were homozygous for rs887829-T defining them as having the genotype characterising Gilbert syndrome. However, only 1701 (3%) of this group had a coded diagnosis of Gilbert syndrome. Variation at this locus explained 37.1% of all variation in measured serum bilirubin. In the observational analyses, higher bilirubin concentrations had strong inverse associations with a wide range of outcomes including overall health status, chronic obstructive pulmonary disease, myocardial infarction, and cholesterol measures. These associations were not identified in people with the Gilbert genotype. We identified associations with genetically predicted bilirubin concentrations and biliary and liver pathology (eg, odds ratio for cholelithiasis 1.16 (95% confidence interval 1.12 to 1.20); P=5.7×10^-16) and a novel association with pityriasis rosea (1.47 (1.27 to 1.69), P=1.28×10^-7).

Conclusions

Only 3% of participants who are homozygous for rs887829-T have a recorded diagnosis of Gilbert syndrome. Carriers of this genotype have modest increases in the odds of developing biliary pathology and pityriasis rosea. Evidence from the analyses of genetic data suggests that bilirubin has no likely causal role in protection from cardiovascular disease, chronic obstructive pulmonary disease, or other key healthcare outcomes and therefore represents a poor target for therapeutic intervention for these outcomes.

The evaluation of liver abnormalities in inflammatory bowel disease patients

PURPOSE OF REVIEW

Develop a clinical presentation-based approach for common liver abnormalities encountered by providers caring for patients with inflammatory bowel disease (IBD). Develop a treatment pathway for those with nonalcoholic fatty liver disease (NAFLD) arising in IBD. Discuss recent studies of prevalence, incidence, risk factors, and prognosis NAFLD in the IBD population.

RECENT FINDINGS

The work-up for liver abnormalities should be approached systematically in IBD patients, similar to the general population, while still appreciating the differing prevalence of underlying liver diagnoses. Although immune mediated liver diseases occur commonly in patients with IBD, NAFLD is still the most common liver disease in patients with IBD paralleling its expanding prevalence in the general population. IBD is also an independent risk factor for NAFLD, developing in many patients with lower degrees of adiposity. Furthermore, the more severe histologic subtype, nonalcoholic steatohepatitis, is both more common and difficult to treat considering the lower effectiveness of weight loss interventions.

SUMMARY

Having a standard approach to the most common liver disease presentations and care pathway for NAFLD will improve the quality of care provided and ease the medical decision making complexity for IBD patients. The early identification of these patients should prevent the development of irreversible complications like cirrhosis or hepatocellular carcinoma.

Fetal and neonatal bilirubin metabolism

Human fetal and neonatal bilirubin metabolism is centered on 4Z,15Z-bilirubin IXα (BR) due to the extremely low BR conjugating capacity of the liver. BR is a unique, highly lipophilic substance with physiological and toxic effects in the cell membranes of organs and body tissues. The fetus excretes BR through the placenta to the maternal circulation. After birth, BR is thought to act as an antioxidant against the increase in reactive oxygen species caused by the rapid increase in oxygen concentration during the adaptation process from in amniotic fluid to in air. However, bilirubin encephalopathy is a toxic effect of bilirubin. Due to the lipophilic nature of BR, it must be bound to a carrier to be distributed to various parts of the body by hydrophilic blood. This carrier of BR is human serum albumin (HSA). In humans, BR can be excreted efficiently after undergoing photochemical reactions upon high affinity binding to HSA. HSA also plays an important role in the prevention of bilirubin encephalopathy. This review focuses on the developmental and physiological role of bilirubin metabolism during the fetal and neonatal periods.

Rapid detection of the irinotecan-related UGT1A1*28 polymorphism by asymmetric PCR melting curve analysis using one fluorescent probe

BACKGROUND

Determination of UGT1A1 (TA)_n polymorphism prior to irinotecan therapy is necessary to avoid severe adverse drug effects. Thus, accurate and reliable genotyping methods for (TA)_n polymorphism are highly desired. Here, we present a new method for polymerase chain reaction (PCR) melting curve analysis using one fluorescent probe to discriminate the UGT1A1*1 [(TA)₆ ] and *28 [(TA)₇ ] genotypes.

METHODS

After protocol optimization, this technique was applied for genotyping of 64 patients (including 23 with UGT1A1*1/*1, 22 with *1/*28, and 19 with *28/*28) recruited between 2016 and 2021 in China-Japan Friendship Hospital. The accuracy of the method was evaluated by comparing the results with those of direct sequencing and fragment analysis. The intra- and inter-run precision of the melting temperatures (T_m s) were calculated to assess the reliability, and the limit of detection was examined to assess the sensitivity.

RESULTS

All genotypes were correctly identified with the new method, and its accuracy was higher than that of fragment analysis. The intra- and inter-run coefficients of variation for the T_m s were both ≤0.27%, with standard deviations ≤0.14°C. The limit of detection was 0.2 ng of input genomic DNA.

CONCLUSION

The developed PCR melting curve analysis using one fluorescent probe can provide accurate, reliable, rapid, simple, and low-cost detection of UGT1A1 (TA)_n polymorphism, and its use can be easily generalized in clinical laboratories with a fluorescent PCR platform.

Dependence of blood biochemical parameters on various genotypes of the UGT1A1 gene associated with gilbert's syndrome

Diagnosis of Gilbert's syndrome is based on the detection of homozygous carriage of an additional TA-repeat in the promoter of the UGT1A1 gene, leading to a decrease in the activity of the UGT enzyme. No large studies have been done in the Russian Federation on the prevalence of carriage of Gilbert's syndrome, as well as the biochemical and molecular profile of such patients. The aim of the study is to evaluate biochemical and molecular genetic parameters in patients with Gilbert's syndrome in Russia. The study included 124 healthy volunteers (group 1) and 5650 patients with suspected Gilbert's syndrome (group 2). The number of TA-repeats of the promoter region of the UGT1A1 gene was determined by the method of fragment analysis for all participants. The following biochemical parameters were analyzed for 299 patients from group 2: the level of bilirubin and its fractions, AST, ALT, cholesterol and LDL. In group 1 the prevalence of genotype (TA)6/(TA)6 was 39,52%, (TA)6/(TA)7 - 53,23%, (TA)7/(TA)7 - 7,26%, no rare forms were found. In group 2 the prevalence of genotype (TA)6/(TA)6 was 6,04%, (TA)6/(TA)7 - 20,05%, (TA)7/(TA)7 - 73,7%, rare alleles - 0,2%. Rare alleles included (TA)5/(TA)6, (TA)5/(TA)7, (TA)6/(TA)8 and (TA)7/(TA)8, as well as a new genotype not described in the literature previously - (TA)7/(TA)9. When assessing the level of total bilirubin and its fractions, a difference was revealed between the genotype of Gilbert's syndrome (TA)7/(TA)7 and the reference genotype (TA)6/(TA)6, and between genotypes (TA)7/(TA)7 and (TA)6/(TA)7. A significant increase in total bilirubin was demonstrated in carriers of a larger number of TA-repeats. There was no significant difference in the concentration of ALT, AST, cholesterol or LDL between different genotypes.The number of TA-repeats of the UGT1A1 gene affects the increase of total bilirubin and its indirect fraction, including the cases of rare allelic variants (TA≤5, TA≥8), but not the activity of ALT and AST and the lipid profile.

The role of UGT1A1 (c.-3279 T > G) gene polymorphisms in neonatal hyperbilirubinemia susceptibility

Background

Neonatal hyperbilirubinemia (NNH) is a common disease in newborns. This research study aimed to assess the associations between uridine diphospho-glucuronate-glucuronosyltransferase 1A1 (UGT1A1, c.-3279 T > G) polymorphisms and NNH risk.

Methods

We searched PubMed, the Cochrane Library, and the Embase electronic databases. All published eligible studies before July 1, 2019, were searched for this meta-analysis.

Results

We identified 7 independent studies including 1560 cases. The data showed that in the general population, compared with the GT + GG vs TT and GG vs TT, c.-3279 T > G (rs4124874) was significantly related to a higher NNH risk (GG vs TT: OR = 1.865, 95% CI: 1.031–3.373, P = 0.039; GT + GG vs TT: OR = 1.331, 95% CI: 1.055–1.679, P = 0.016). Although not statistically significant, the data showed that c.3279 T > G had a tendency to be associated with NNH under the allele model and GG vs GT + TT in the overall population (G vs T: OR = 1.288, 95% CI: 0.982–1.689, P = 0.067; GG vs TT + GT: OR = 1.583, 95% CI: 0.947–2.647, P = 0.080).

Conclusion

The UGT1A1 gene c.-3279 T > G (rs4124874) polymorphism increased susceptibility to NNH, especially for the comparison of GT + GG vs TT and GG vs TT. In the future, we can use homozygous state of the UGT1A1 gene c.-3279 T > G (rs4124874) polymorphism for the diagnosis and screening of molecular biomarkers in NNH patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12881-020-01155-2.

Gilbert syndrome with systemic lupus erythematosus presenting with persistent unconjugated hyperbilirubinemia: A case report

Gilbert syndrome (GS) is a hereditary unconjugated hyperbilirubinemia that results from mutations in the bilirubin uridine diphosphate-glucuronosyltransferase (UGT1A1) gene. To the best of our knowledge, there are currently no reports that focus on patients with systemic lupus erythematosus (SLE) coexisting with GS. The present study aimed to evaluate the clinical characteristics and genotype of UGT1A1 in a Chinese patient with SLE and GS. Complete medical records and laboratory data were reviewed for a patient with SLE referred to Ruijin Hospital (Shanghai, China) for treatment between March 2016 and January 2020. Genetic analysis of the UGT1A1 gene was performed by PCR amplification and Sanger sequencing. The serum total bilirubin and unconjugated bilirubin concentrations on admission were 96.2 and 86.8 µmol/l, respectively. The homozygous mutation c.1456T>G (p.Y486D) in exon 5 was detected in this patient. The patient had a good response to phenobarbital orally at a dose of 30 mg/day and a decrease in serum bilirubin was observed. Elevated unconjugated hyperbilirubinemia in SLE needs to be differentiated from other diseases, such as GS, which can be diagnosed by UGT1A1 genetic sequencing.

Human variability in isoform-specific UDP-glucuronosyltransferases: markers of acute and chronic exposure, polymorphisms and uncertainty factors

UDP-glucuronosyltransferases (UGTs) are involved in phase II conjugation reactions of xenobiotics and differences in their isoform activities result in interindividual kinetic differences of UGT probe substrates. Here, extensive literature searches were performed to identify probe substrates (14) for various UGT isoforms (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7 and UGT2B15) and frequencies of human polymorphisms. Chemical-specific pharmacokinetic data were collected in a database to quantify interindividual differences in markers of acute (Cmax) and chronic (area under the curve, clearance) exposure. Using this database, UGT-related uncertainty factors were derived and compared to the default factor (i.e. 3.16) allowing for interindividual differences in kinetics. Overall, results show that pharmacokinetic data are predominantly available for Caucasian populations and scarce for other populations of different geographical ancestry. Furthermore, the relationships between UGT polymorphisms and pharmacokinetic parameters are rarely addressed in the included studies. The data show that UGT-related uncertainty factors were mostly below the default toxicokinetic uncertainty factor of 3.16, with the exception of five probe substrates (1-OH-midazolam, ezetimibe, raltegravir, SN38 and trifluoperazine), with three of these substrates being metabolised by the polymorphic isoform 1A1. Data gaps and future work to integrate UGT-related variability distributions with in vitro data to develop quantitative in vitro-in vivo extrapolations in chemical risk assessment are discussed.

A high frequency of Gilbert syndrome (UGT1A1*28/*28) and associated hyperbilirubinemia but not cholelithiasis in adolescent and adult north Indian patients with transfusion-dependent β-thalassemia

Hyperbilirubinemia and pigment gallstones are frequent complications in transfusion-dependent β-thalassemia (TDβT) patients. Bilirubin production and clearance are determined by genetic as well as environmental variables like ineffective erythropoiesis, hemolysis, infection-induced hepatic injury, and drug- or iron-related toxicities. We studied the frequency of the Gilbert syndrome (GS), a common hereditary cause of hyperbilirubinemia in 102 TDβT patients aged 13-43 years (median 26 years). Total and unconjugated hyperbilirubinemia were frequent (81.4% and 84.3% patients respectively). Twenty (19.6%) patients showed total bilirubin > 3.0 mg/dL; 53 (51.9%) had an elevation of either alanine or aspartate aminotransferase, or alkaline phosphatase liver enzymes. Nineteen (18.6% of the 92 tested) were positive for hepatitis B or C, or HIV. The mean total and unconjugated bilirubin levels and AST, ALT, and ALP levels in patients positive for hepatitis B or C were not significantly different from negative cases. Eighteen patients (17.7%) had GS: homozygous (TA)7/7 UGT1A1 promoter motif (the *28/*28 genotype), 48 (47.1%) were heterozygous (TA)6/7. Total + unconjugated bilirubin rose significantly with the (TA)7 allele dose. Fourteen (13.7%) patients had gallstones. There was no significant difference in total/unconjugated bilirubin in patients with/without gallstones and no significant differences in frequencies of gallstones within the three UGT1A1 genotypes. This largest study in Indian TDβT patients suggests that GS should be excluded in TDβT cases where jaundice remains unexplained after treatable causes like infections, chelator toxicity, or transfusion-related hemolysis are excluded. GS was not associated with gallstones, possibly due to a lower incidence of cholelithiasis overall, a younger age cohort, or other environmental factors.

Influence of Uridine Diphosphate Glucuronosyltransferase Family 1 Member A1 and Solute Carrier Organic Anion Transporter Family 1 Member B1 Polymorphisms and Efavirenz on Bilirubin Disposition in Healthy Volunteers

Chronic administration of efavirenz is associated with decreased serum bilirubin levels, probably through induction of UGT1A1 We assessed the impact of efavirenz monotherapy and UGT1A1 phenotypes on total, conjugated, and unconjugated serum bilirubin levels in healthy volunteers. Healthy volunteers were enrolled into a clinical study designed to address efavirenz pharmacokinetics, drug interactions, and pharmacogenetics. Volunteers received multiple oral doses (600 mg/day for 17 days) of efavirenz. Serum bilirubin levels were obtained at study entry and 1 week after completion of the study. DNA genotyping was performed for UGT1A1 [*80 (C>T), *6 (G>A), *28 (TA₇), *36 (TA₅), and *37 (TA₈)] and for SLCO1B1 [*5 (521T>C) and *1b (388A>G] variants. Diplotype predicted phenotypes were classified as normal, intermediate, and slow metabolizers. Compared with bilirubin levels at screening, treatment with efavirenz significantly reduced total, conjugated, and unconjugated bilirubin. After stratification by UGT1A1 phenotypes, there was a significant decrease in total bilirubin among all phenotypes, conjugated bilirubin among intermediate metabolizers, and unconjugated bilirubin among normal and intermediate metabolizers. The data also show that UGT1A1 genotype predicts serum bilirubin levels at baseline, but this relationship is lost after efavirenz treatment. SLCO1B1 genotypes did not predict bilirubin levels at baseline or after efavirenz treatment. Our data suggest that efavirenz may alter bilirubin disposition mainly through induction of UGT1A1 metabolism and efflux through multidrug resistance-associated protein 2. SIGNIFICANCE STATEMENT: Efavirenz likely alters the pharmacokinetics of coadministered drugs, potentially causing lack of efficacy or increased adverse effects, as well as the disposition of endogenous compounds relevant in homeostasis through upregulation of UGT1A1 and multidrug resistance-associated protein 2. Measurement of unconjugated and conjugated bilirubin during new drug development may provide mechanistic understanding regarding enzyme and transporters modulated by the new drug.

UGT1A1*28 gene polymorphism was not associated with the risk of neonatal hyperbilirubinemia: a meta-analysis

Background: This study aimed to evaluate the relationship between UGT1A1*28 gene polymorphism and the risk of neonatal hyperbilirubinemia (NHBI).Methods: The studies meet certain selection condition which was obtained from databases such as PubMed, Embase, and Cochrane Library. Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of included studies. Meta-analysis was performed according to criteria such as country. Hardy-Weinberg's equilibrium (HWE) tests were performed on the control group using chi-square test, while the evaluation index was represented by odds ratio (OR) and 95% confidence interval (CI). Egger's test and sensitivity analysis were used to evaluate the publication bias and reliability, repetitively.Results: Totally, four studies with high overall quality were enrolled in this study. No association was observed between UGT1A1*28 gene polymorphisms and NHBI in allele model (TA7 versus TA6, OR (95% CI) = 2.13 (0.81-5.62), p = .13), codominance models (TA7/6 versus TA6/6, OR (95% CI) = 2.94 (0.90-9.57), p = .07; TA7/7 versus TA6/6, OR (95% CI) = 2.08 (0.37-11.52), p = .40), recessive model (TA7/7 versus TA6/6 + TA7/6, OR (95% CI) = 1.44 (0.41-5.14), p = .57), and dominant model (TA7/7 + TA7/6 versus TA6/6, OR (95% CI) = 2.92 (0.84-10.12), p = .09). Furthermore, there was no publication bias found in current meta-analysis.Conclusions: Gene polymorphism of UGT1A1*28 might not be associated with the risk of NHBI.

Incidence and Risk of Gallstone Disease in Gilbert's Syndrome Patients in Indian Population

BACKGROUND/OBJECTIVES

Individuals with Gilbert's syndrome (GS) harbor mutations in the UGT1A1 gene and are known to have elevated levels of bilirubin, which enhances the risk for gall stone formation. The aim of this study is to screen Indian patients with GS for the incidence of gall stone disease.

METHODS

Individuals with persistently elevated serum bilirubin levels were genotyped for two polymorphisms (rs8175347; rs4148323) in UGT1A1 gene to confirm GS in them. Flanking regions of the above polymorphisms were amplified followed by direct sequencing. Ultrasonography was done to detect gallstone disease. Clinical data, including assessment of liver function, circulating levels of total and direct bilirubin, as well as routine hematological parameters were obtained as per standard procedures (Autoanalyzer).

RESULTS

Of the total 1621 individuals subjected to genotyping, 1191 (1149 males of 29.6 ± 11.3 years with mean BMI of 22.1 ± 3.7 kg/m² and 42 females of 30.8 ± 14.8 years with mean BMI of 20.9 ± 3.7 kg/m²) were confirmed to have GS. Gall bladder abnormalities including cholelithiasis (n = 106/1191; 8.9%), polyps (n = 18/1191; 1.5%) and gallbladder wall thickening (n = 17/1191; 1.4%) were noted. Incidence of gall stone disease was observed in 103 males (out of 1149) and 3 females (out of 42) indicating the risk of the disease to be 9.0% and 7.1% respectively in males and females with GS.

CONCLUSION

Early recognition of GS by genetic analysis is required before these patients with intermittent episodes of jaundice run the risk of unnecessary operations on their bile ducts from the mistaken assumption ascribing the jaundice to a stone which has been left behind.

CYP3A4-mediated effects of rifampicin on the pharmacokinetics of vilaprisan and its UGT1A1-mediated effects on bilirubin glucuronidation in humans

AIMS

The primary aim of the present study was to quantify the effects of rifampicin, a strong cytochrome P450 (CYP) 3A4 inducer, on the pharmacokinetics of the new selective progesterone receptor modulator, vilaprisan. In addition, the effects of rifampicin on the glucuronidation of bilirubin, an endogenous UDP-glucuronosyltransferase family 1 member A1 (UGT1A1) substrate, were explored.

METHODS

This was an open-label, two-period study in 12 healthy postmenopausal women. Subjects received a single oral dose of vilaprisan 4 mg in each period. In period 2, administration of vilaprisan was preceded and followed by rifampicin 600 mg day^-1 . A subtherapeutic dose of midazolam (1 mg) was coadministered with vilaprisan to monitor CYP3A4 induction. Details of the administration and sampling schedule were optimized by means of a physiologically based pharmacokinetic model. Plasma concentrations of vilaprisan, midazolam, and 1'- hydroxy-midazolam were measured and rifampicin-associated changes in the glucuronidation of bilirubin were determined.

RESULTS

As predicted by our model, the coadministration of rifampicin was associated with a substantial decrease in exposure to vilaprisan and midazolam - indicated by the following point estimates (90% confidence intervals) for the area under the plasma concentration-time curve from zero to the time of the last quantifiable concentration ratio with or without rifampicin: 0.040 (0.0325, 0.0505) for vilaprisan and 0.144 (0.117, 0.178) for midazolam. Further, it was associated with an increase in bilirubin glucuronidation, indicating that UGT1A1 was induced.

CONCLUSIONS

The exposure to vilaprisan was reduced by 96%. Such a reduction is likely to render the drug therapeutically ineffective. Therefore, it is recommended that the use of strong CYP3A4 inducers is avoided when taking vilaprisan.

Bilirubin Is Inversely Associated With Cardiovascular Disease Among HIV-Positive and HIV-Negative Individuals in VACS (Veterans Aging Cohort Study)

Background

Bilirubin may protect against cardiovascular disease (CVD) by reducing oxidative stress. Whether elevated bilirubin reduces the risk of CVD events among HIV⁺ individuals and if this differs from uninfected individuals remain unclear. We assessed whether bilirubin independently predicted the risk of CVD events among HIV⁺ and uninfected participants in VACS (Veterans Aging Cohort Study).

Methods and Results

We conducted a prospective cohort study using VACS participants free of baseline CVD. Total bilirubin was categorized by quartiles. CVD as well as acute myocardial infarction, heart failure, and ischemic stroke events were assessed. Cox regression was used to evaluate hazard ratios of outcomes associated with quartiles of total bilirubin in HIV⁺ and uninfected people after adjusting for multiple risk factors. There were 96 381 participants (30 427 HIV⁺); mean age was 48 years, 48% were black, and 97% were men. There were 6603 total incident CVD events over a mean of 5.7 years. In adjusted models, increasing quartiles of baseline total bilirubin were associated with decreased hazards of all outcomes (hazard ratio, 0.86; 95% confidence interval, 0.80–0.91). Among HIV⁺ participants, results persisted for heart failure, ischemic stroke, and total CVD, but nonsignificant associations were observed for acute myocardial infarction.

Conclusions

VACS participants (regardless of HIV status) with elevated bilirubin levels had a lower risk of incident total CVD, acute myocardial infarction, heart failure, and ischemic stroke events after adjusting for known risk factors. Future studies should investigate how this apparently protective effect of elevated bilirubin could be harnessed to reduce CVD risk or improve risk estimation among HIV⁺ individuals.

"Gilbert's-like" syndrome as part of a spectrum of persistent unconjugated hyperbilirubinemia in post-chronic hepatitis patients

Gilbert’s syndrome (GS) patients present with remittent unconjugated hyperbilirubinemia. In this study, we investigated the correlation between polymorphisms in the gene encoding UDP-glucuronosyltransferase, UGT1A1, and the development of unconjugated hyperbilirubinemia in clinical GS and post-hepatitis hyperbilirubinemia. Blood samples were collected from 285 patients, including 85 patients who were clinically diagnosed with GS, 70 patients who had indirect hyperbilirubinemia during the recovery period of chronic liver diseases, 109 patients with normal hepatic function and 21 chronic active hepatitis patients. All samples were tested for the presence of the *28/*6 UGT1A1 genotype by pyrosequencing. Compared with the GS-control group, a significant difference in variations of the UGT1A1*28/*6 allele gene was found in GS patients. The post-hepatitis group showed a significant difference in the UGT1A1*28/*6 allele gene frequency distribution relative to that in the hepatitis control group. There were no significant differences between the GS group and post-hepatitis group in the distribution of the UGT1A1*28/*6 allele gene frequency and UGT1A1 diplotypes. UGT1A1*28/*6 gene polymorphisms in patients who had indirect hyperbilirubinemia while recovering from chronic liver diseases presented similar patterns as those seen for GS patients. These findings suggest that a “Gilbert’s-like” syndrome might be part of the spectrum of persistent unconjugated hyperbilirubinemia in post-chronic hepatitis patients.

Differences in UGT1A1 gene mutations and pathological liver changes between Chinese patients with Gilbert syndrome and Crigler-Najjar syndrome type II

Diagnosis of Crigler-Najjar syndrome type II (CNS-II) and Gilbert syndrome (GS) based on the serum bilirubin concentration is difficult, because this parameter can fluctuate under certain conditions. The aim of this study was to explore differences in UGT1A1 gene mutations, which cause both CNS and GS, and pathological changes between CNS-II and GS.Ninety-five Chinese patients with hereditary unconjugated hyperbilirubinemia were enrolled in this study. Peripheral blood samples obtained from patients were used to evaluate bilirubin levels and for UGT1A1 gene testing. Percutaneous needle biopsy of the liver and staining of tissue samples with hematoxylin and eosin, Masson trichrome, reticulin, and Perl Prussian blue were performed for 59 patients. The Ishak scoring system was used to assess inflammatory activity and the extent of fibrosis.One hundred ninety-two UGT1A1 mutations at 6 sites were detected in the 95 patients; the most common mutation in GS was c.-3279T>G in the phenobarbital response enhancing motif of the UGT1A1 promoter, whereas the most common mutation in CNS-II was p.G71R. The frequency of heterozygous p.G71R mutations in CNS-II was significantly higher than that in GS (P = .001); however, the frequency of homozygous c.-3279T>G mutations in CNS-II was markedly lower than that in GS (P = .032). Among all patients with multiple mutations, the frequency of p.Y486D was significantly higher in CNS-II than in GS (P = .007). The frequency of compound c.-3279T>G, A(TA)7TAA, and p.G71R mutations in CNS-II was significantly higher than that in GS (P = .001). Among the 59 patients who underwent percutaneous needle biopsy, 20 had iron deposition in the liver. The frequency of hepatic iron deposition in CNS-II was significantly higher than that in GS (P = .002).The linked polymorphic mutations, A(TA)7TAA and c.-3279T>G in UGT1A1, were most strongly associated with GS, whereas mutations in the coding region, especially p.G71R and p.Y486D, were more strongly associated with CNS-II. Iron deposition was more common in liver biopsies from patients with CNS-II than in those with GS.

Do Alpha Thalassemia, Fetal Hemoglobin, and the UGT1A1 Polymorphism have an Influence on Serum Bilirubin Levels and Cholelithiasis in Patients with Sickle Cell Disease?

BACKGROUND

Increased destruction of erythrocytes in patients with sickle cell disease results in chronic hyperbilirubinemia and leads to the formation of gallstones.

OBJECTIVES

The objective of this study was to determine the combined influence of alpha thalassemia, fetal hemoglobin, and the UGT1A1 polymorphism on serum bilirubin levels and cholelithiasis in patients with sickle cell disease.

METHODS

We analyzed 72 patients treated in the outpatient hematology unit of the Clinical Hospital of Porto Alegre. The alpha thalassemia trait was determined by multiplex polymerase chain reaction and the polymorphisms of UGT1A1 by capillary electrophoresis with tagged primers.

RESULTS

Total and indirect bilirubin levels differed significantly between genotypes TA7/TA7 and TA6/TA6 (p < 0.05). Bilirubin levels were influenced by the UGT1A1 polymorphism but not by alpha thalassemia and fetal hemoglobin. There was no association between cholelithiasis and any of the variables studied.

CONCLUSION

These preliminary findings suggest that the UGT1A1 gene can influence serum bilirubin levels in sickle cell anemia and serve as a tool to differentiate an acute hemolytic condition from a pre-existing condition of hyperbilirubinemia.

Association between the Specific UGT1A1 Promoter Sequence Variant (c-3279T>G) and Unconjugated Neonatal Hyperbilirubinemia

We investigated the association between c-3279T>G and unconjugated neonatal hyperbilirubinemia. In all, 141 neonates were recruited; 63 had hyperbilirubinemia necessitating treatment, and 78 with bilirubin < 7 mg/dl served as the control group. The frequency of occurrence of c-3279T > G allele was significantly higher in the hyperbilirubinemic (49.2%) than in the control group (25.6%). The homozygous (p = 0.001, OR = 17.7 and CI = 3.9-79.3) rather than the heterozygous state (p = 0.3, OR = 0.7 and CI = 0.3-1.6) was associated with hyperbilirubinemia. Among the hyperbilirubinemic group, comparison between the three genotypes, homozygous mutation, heterozygous mutation and the normal allele, revealed that the former was associated with significantly higher mean peak total serum bilirubin [mean ±  standard deviation (SD): 33.7 ± 8.2, 26.9 ± 2.8 and 21± 2.7, respectively, p-value = 0.0001], higher bilirubin/albumin ratio (p = 0.000) and a longer duration of hospital stay (p = 0.001). Homozygous c-3279T > G mutation represents an important risk factor for the development of neonatal hyperbilirubinemia.

Genetic susceptibility to Gilbert's syndrome in a valencian population; efficacy of the fasting test

OBJECTIVE

To describe the populational distribution of the UGT1A1*28 variant (genetic variant code rs8175347) located in the promotor of the UGT gene and correlate its genotypes with the results of the fasting test, as well as its relationship with the biochemical disorder of Gilbert's syndrome (GS) in a Valencian population.

PATIENTS AND METHODS

We studied the prevalence of the genotypes (TA)_6/6 (TA)_6/7 and (TA)_7/7 of the deleterious variant rs8175347 in 144 patients with hyperbilirubinemia, 38 of whom had previously undergone the fasting test to diagnose GS, and in 150 control patients. By analysing the genomic region of the TATA box of the UGT1A1 gene promotor using Sanger sequencing, we established the correlation between the rs8175347 genotypes and the fasting test results and with the patients' biochemical disorders.

RESULTS

The rate of heterozygosity of allele (TA)₇ in the control population was 32% and increased to 87.59% among the patients with suspected GS. The rate of genotype TA_7/7 was 81.94% among the patients with hyperbilirubinemia, compared with 11.33% in the control patients. The fasting test showed a 15.79% rate of false negatives and a 5.26% rate of false positives.

CONCLUSIONS

The high frequency of allele (TA)₇ among the Valencian control population, almost double the 5% reported for European control patients, confirms the high rate of GS reported in the Spanish population, without observing significant differences between the geographical ends of the country. The efficacy and reliability of the fasting test for the diagnosis of GS is questionable.

BILIRUBIN CONCENTRATIONS IN CLINICALLY HEALTHY AND DISEASED CAPTIVE WATERBUCK (KOBUS ELLIPSIPRYMNUS) AT THE SAN DIEGO ZOO SAFARI PARK

Captive waterbuck ( Kobus ellipsiprymnus ) that appear clinically healthy have been noted to have high serum bilirubin concentrations compared with other ruminants; however, questions remain about the physiologic factors affecting bilirubin concentration and its potential association with underlying disease and icteric serum or mucous membranes. Serum bilirubin concentrations of healthy and diseased waterbuck housed at the San Diego Zoo Safari Park from 1989 to 2012 were retrospectively analyzed to determine any link between icteric serum, total bilirubin concentration (tBili), and disease entities in this species. Total bilirubin and direct (dBili) bilirubin concentrations and the prevalence of icteric serum were compared by subspecies, age group, and health status; associations with complete blood count and biochemical results and clinical diagnosis were assessed. No significant differences were found in tBili or dBili between Ellipsen (n = 32) and Defassa (n = 29) subspecies or in juveniles (n = 22) versus adults (n = 39). Clinically healthy waterbuck (n = 40) had significantly higher tBili (mean ± 2SD, 7.9 ± 1.2 mg/dl; P < 0.001) and dBili (3.7 ± 1.0 mg/dl; P < 0.001) than did diseased waterbuck (n = 21; tBili: 4.9 ± 2.56 mg/dl; dBili: 2.2 ± 0.8 mg/dl). No waterbuck had icteric tissues on physical examination. Twelve (19.7%) waterbuck (six healthy, six diseased) had icteric serum. Few minor correlations were seen between tBili or dBili and clinical, laboratory, or necropsy evidence of disease, though an inverse correlation between dBili and blood glucose was noted. Of the 40 healthy animals, reference intervals were calculated for tBili (5.5-10.3 mg/dl), dBili (1.7-5.7 mg/dl), and indirect bilirubin (2.2-6.2 mg/dl). These results suggest healthy waterbuck have relatively high tBili and dBili compared with related species. Icteric serum may be seen in up to 15% of healthy animals in the absence of icteric tissues.

Genetic Predictors of Response to Different Medical Therapies in Acromegaly

In the era of predictive medicine, management of diseases is evolving into a more personal and individualized approach, as more data are available regarding clinical, biochemical, radiological, molecular, histopathological, and genetic aspects. In the particular setting of acromegaly, which is a rare, chronic, debilitating, and disfiguring disease, an optimized approach deems even more necessary, especially because of an associated increased morbidity and mortality, the impact on patients' quality of life, and the increased cost of frequently necessary life-long treatments. In this paper, we review the available studies that address potential genetic influences on acromegaly, their role in the outcome, and response to treatments, as well as their contribution to the risk of developing side effects. We focus mainly on pharmacogenetic factors involved during treatment with dopamine agonists, somatostatin analogs, and pegvisomant. Specifically, mutations in dopamine receptors, somatostatin receptors, growth hormone receptors, and metabolic pathways involved in growth hormone action; polymorphisms in the insulin-like growth factor and the insulin-like growth factor binding proteins; and polymorphisms in other genes that may determine differences in the frequency of developing adverse events.

Genotype of UGT1A1 and phenotype correlation between Crigler-Najjar syndrome type II and Gilbert syndrome

BACKGROUND AND AIMS

Hereditary unconjugated hyperbilirubinemias, Crigler-Najjar syndrome type I, Crigler-Najjar syndrome type II (CN-2), and Gilbert syndrome (GS) all result from mutations of the bilirubin uridine 5'-diphosphate (UDP)-glucuronosyltransferase gene (UGT1A1). Often, to distinguish between CN-2 and GS is difficult because the borderline of the two syndromes is unclear. We analyzed the genotypes and phenotypes of 163 Japanese patients with CN-2 or GS.

METHODS

Japanese patients (99 males and 64 females) with unconjugated hyperbilirubinemia were analyzed. Their serum bilirubin concentrations varied from 1.2 to 22.2 mg/dL (20 to 379 μM). Genetic analysis of UGT1A1 was performed by PCR-amplified direct sequencing. Association between serum bilirubin concentrations and genotypes group (typical CN-2, intermediate group, and typical GS) was studied.

RESULTS

Most patients had biallelic mutations of UGT1A1. Moreover, many of them (78.5%) had multiple mutations. The mutation in typical CN-2 was a homozygous double missense mutation of p.[G71R:Y486D]. In typical GS group, four prevalent genotypes were detected: homozygous UGT1A1*28, UGT1A1*6/UGT1A1*28, and homozygous UGT1A1*6, and UGT1A1*27/UGT1A1*28. In the intermediate group, three genotypes, p.[G71R:Y486D]/UGT1A1*7, p.[G71R:Y486D]/UGT1A1*6, and homozygous UGT1A1*7, were detected. Serum bilirubin concentrations of typical CN-2, intermediate group, and typical GS are respectively 12.9 ± 5.1, 5.2 ± 2.2, and 2.8 ± 1.1 mg/dL. Serum bilirubin concentration among the three groups is statistically different (P < 0.0001).

CONCLUSIONS

The serum bilirubin concentration varied continuously from GS to CN-2 depending on genotypes. Because of the combination of the mutations and polymorphisms, many patients showed intermediate serum bilirubin concentration between two syndromes. Clinically, it is difficult to distinguish clearly between the two syndromes.

Role of extrahepatic UDP-glucuronosyltransferase 1A1: Advances in understanding breast milk-induced neonatal hyperbilirubinemia

Newborns commonly develop physiological hyperbilirubinemia (also known as jaundice). With increased bilirubin levels being observed in breast-fed infants, breast-feeding has been recognized as a contributing factor for the development of neonatal hyperbilirubinemia. Bilirubin undergoes selective metabolism by UDP-glucuronosyltransferase (UGT) 1A1 and becomes a water soluble glucuronide. Although several factors such as gestational age, dehydration and weight loss, and increased enterohepatic circulation have been associated with breast milk-induced jaundice (BMJ), deficiency in UGT1A1 expression is a known cause of BMJ. It is currently believed that unconjugated bilirubin is metabolized mainly in the liver. However, recent findings support the concept that extrahepatic tissues, such as small intestine and skin, contribute to bilirubin glucuronidation during the neonatal period. We will review the recent advances made towards understanding biological and molecular events impacting BMJ, especially regarding the role of extrahepatic UGT1A1 expression.

Restriction fragment length polymorphism effectively identifies exon 1 mutation of UGT1A1 gene in patients with Gilbert's Syndrome

BACKGROUND & AIMS

Gilbert's syndrome causes pharmacological variation in drug glucuronidation and unexpected toxicity from therapeutic agents. The two common genotypes of Gilbert's syndrome are a dinucleotide polymorphism (TA)7 in TATA-Box as well as the 211G>A mutation in the coding exon 1, particularly in Asians, of human UGT1A1 gene. In this study, we aimed to establish an effective method to detect the 211G>A mutation.

METHODS

The coding exon 1 sequence of human UGT1A1 gene was analysed by Vector NTI software. The 211G>A mutation in the coding exon 1 of UGT1A1 gene was determined by restriction fragment length polymorphism (RFLP) method. Serum total bilirubin level was measured as well.

RESULTS

A newly identified BsmBI site was located in the coding exon 1 of UGT1A1 gene. The 211G>A mutation in the coding exon 1 of UGT1A1 gene was determined by DNA RFLP. Furthermore, we reported our present work on genetic analysis of mutations of UGT1A1 gene, and the correlation of UGT1A1 mutations with serum total bilirubin levels in Taiwanese population. The results showed that 15 subjects carried 211G>A mutation in 23 subjects related with Gilbert's syndrome. The homozygous 211G>A mutant as well as simultaneously heterozygous mutants both in TATA-Box and 211G>A significantly increased the risk of Gilbert's syndrome similar to subjects carrying homozygous TATA-Box mutant.

CONCLUSIONS

BsmBI RFLP is an effective method to detect 211G>A mutation in the coding exon 1 of UGT1A1 gene. The common 211G>A mutation is one of the causes of Gilbert's syndrome in Taiwanese population.

Biotransformation of xenobiotics in the human colon and rectum and its association with colorectal cancer

In humans, the liver is generally considered to be the major organ contributing to drug metabolism, but studies during the last years have suggested an important role of the extra-hepatic drug metabolism. The gastrointestinal tract (GI-tract) is the major path of entry for a wide variety of compounds including food, and orally administered drugs, but also compounds - with neither nutrient nor other functional value - such as carcinogens. These compounds are metabolized by a large number of enzymes, including the cytochrome P450 (CYP), the glutathione S-transferase (GST) family, the uridine 5'-diphospho- glucuronosyltransferase (UDP-glucuronosyltransferase - UGT) superfamily, alcohol-metabolizing enzymes, sulfotransferases, etc. These enzymes can either inactivate carcinogens or, in some cases, generate reactive species with higher reactivity compared to the original compound. Most data in this field of research originate from animal or in vitro studies, wherein human studies are limited. Here, we review the human studies, in particular the studies on the phenotypic expression of these enzymes in the colon and rectum to get an impression of the actual enzyme levels in this primary organ of exposure. The aim of this review is to give a summary of currently available data on the relation between the CYP, the GST and the UGT biotransformation system and colorectal cancer obtained from clinical and epidemiological studies in humans.

Inherited disorders of bilirubin transport and conjugation: new insights into molecular mechanisms and consequences

Inherited disorders of bilirubin metabolism might reduce bilirubin uptake by hepatocytes, bilirubin conjugation, or secretion of bilirubin into bile. Reductions in uptake could increase levels of unconjugated or conjugated bilirubin (Rotor syndrome). Defects in bilirubin conjugation could increase levels of unconjugated bilirubin; the effects can be benign and frequent (Gilbert syndrome) or rare but severe, increasing the risk of bilirubin encephalopathy (Crigler-Najjar syndrome). Impairment of bilirubin secretion leads to accumulation of conjugated bilirubin (Dubin-Johnson syndrome). We review the genetic causes and pathophysiology of disorders of bilirubin transport and conjugation as well as clinical and therapeutic aspects. We also discuss the possible mechanisms by which hyperbilirubinemia protects against cardiovascular disease and the metabolic syndrome and the effects of specific genetic variants on drug metabolism and cancer development.

New insights in bilirubin metabolism and their clinical implications

Bilirubin, a major end product of heme breakdown, is an important constituent of bile, responsible for its characteristic colour. Over recent decades, our understanding of bilirubin metabolism has expanded along with the processes of elimination of other endogenous and exogenous anionic substrates, mediated by the action of multiple transport systems at the sinusoidal and canalicular membrane of hepatocytes. Several inherited disorders characterised by impaired bilirubin conjugation (Crigler-Najjar syndrome type I and type II, Gilbert syndrome) or transport (Dubin-Johnson and Rotor syndrome) result in various degrees of hyperbilirubinemia of either the predominantly unconjugated or predominantly conjugated type. Moreover, disrupted regulation of hepatobiliary transport systems can explain jaundice in many acquired liver disorders. In this review, we discuss the recent data on liver bilirubin handling based on the discovery of the molecular basis of Rotor syndrome. The data show that a substantial fraction of bilirubin conjugates is primarily secreted by MRP3 at the sinusoidal membrane into the blood, from where they are subsequently reuptaken by sinusoidal membrane-bound organic anion transporting polypeptides OATP1B1 and OATP1B3. OATP1B proteins are also responsible for liver clearance of bilirubin conjugated in splanchnic organs, such as the intestine and kidney, and for a number of endogenous compounds, xenobiotics and drugs. Absence of one or both OATP1B proteins thus may have serious impact on toxicity of commonly used drugs cleared by this system such as statins, sartans, methotrexate or rifampicin. The liver-blood cycling of conjugated bilirubin is impaired in cholestatic and parenchymal liver diseases and this impairment most likely contributes to jaundice accompanying these disorders.

The effects of antipsychotics on behavioral abnormalities of the Gunn rat (unconjugated hyperbilirubinemia rat), a rat model of schizophrenia

BACKGROUND

There have been reports of a positive relationship between schizophrenia and hyperbilirubinemia. Patients with schizophrenia show a significantly higher frequency of hyperbilirubinemia than patients suffering from other psychiatric disorders and when compared to the general population. Previously we observed that patients suffering from schizophrenia frequently present an elevated unconjugated bilirubin plasma concentration, when admitted to the hospital. In addition it was recently reported that unconjugated bilirubin exhibited neurotoxicity in the developing nervous system. We also reported that Gunn rats, which tend to show a high frequency of hyperbilirubinemia, may be used as an animal model of schizophrenia. In the present study, we assessed the effects of antipsychotics on Gunn rat behavioral abnormalities.

METHODS

We examined the behavior of Gunn rats after treatment with risperidone (0.1mg/kg), haloperidol (0.2mg/kg), or aripiprazole (0.4mg/kg) using an open-field test, social interaction test and a prepulse inhibition (PPI) test.

RESULTS

The administration of antipsychotics alleviated behavioral abnormalities, mimicking some positive and negative symptoms and cognitive defects of schizophrenia. The pharmacological reaction of Gunn rats to antipsychotics echoes the pharmacological response of humans to such antipsychotics.

CONCLUSIONS

Our study suggested that the Gunn rat may be useful as a preclinical model of schizophrenia with which to evaluate the pharmacological properties of antipsychotics. The results obtained to date have been encouraging and warrant further research.

Short communication: UGT1A1*28 variant allele is a predictor of severe hyperbilirubinemia in HIV-infected patients on HAART in southern Brazil

Highly active antiretroviral therapy (HAART) has increased the survival of HIV-infected patients. However, adverse effects play a major role in adherence to HAART. Some protease inhibitors (mainly atazanavir and indinavir) act as inhibitors of uridine diphosphate-glucuronosyltransferase (UGT1A1), the enzyme responsible for hepatic conjugation of bilirubin. Variations in the promoter region of the UGT1A1 gene (UGT1A1*28, rs8175347) can influence bilirubin plasma levels, modulating the susceptibility to hyperbilirubinemia. Aiming to analyze the association between UGT1A1*28 allele and hyperbilirubinemia in individuals exposed to HAART, we evaluated 375 HIV-positive individuals on antiretroviral therapy. Individuals carrying the UGT1A1*28 allele had a higher risk of developing severe hyperbilirubinemia [prevalence ratio (PR)=2.43, 95% confidence interval (CI) 1.08-5.45, p=0.032] as well as atazanavir users (PR=7.72, 95% CI=3.14-18.98, p<0.001). This is the first description of such an association in Brazilian HIV patients, which shows that in African-American and Euroamerican HAART users, the UGT1A1*28 allele also predisposes to severe hyperbilirubinemia, especially in those exposed to atazanavir.

Quantification of Hepatic UDP glucuronosyltransferase 1A splice variant expression and correlation of UDP glucuronosyltransferase 1A1 variant expression with glucuronidation activity

The UDP glucuronosyltransferase (UGT) 1A gene cluster encodes nine UGT1A family members via splicing of individual first exons to common exons 2 through 5. Each of these nine UGT1As can also undergo alternative splicing at their 3' ends by using an alternate exon 5, resulting in 27 different UGT1A mRNA species with each UGT1A gene encoding three different combinations of 5A and 5B UGT1A exons. To examine the importance of UGT1A exon 5 splice variants on overall UGT1A activity, a nested quantitative polymerase chain reaction assay was developed to accurately assess the combined expression of exon 5 splice variants (termed v2/v3) versus the expression of wild-type (termed v1) for each specific UGT1A. v1 expression was 16-, 17-, 57- and 29-fold higher than that observed for the levels of v2/v3 for UGTs 1A1, 1A4, 1A6, and 1A9, respectively, in normal human liver specimens. In a series of 58 normal human liver specimens, the expression of both UGT1A1 v1 and v2/v3 mRNAs was positively correlated with raloxifene glucuronidation activity in corresponding microsomes prepared from the same specimens (p < 0.0001, r² = 0.720; p = 0.0002, r² = 0.241, respectively), with expression of both variants lower in individuals homozygous for the UGT1A1*28 allele (42% for v1, p = 0.041; 53% for v2/v3, p = 0.0075). The expression of UGT1A1 v2/v3 was 1.6-fold higher than v1 (p = 0.03) in HepG2 cells, and short interfering RNA knockdown of HepG2 v2/v3 increased raloxifene glucuronidation activity by 83%. Together, these data suggest that hepatic UGT1A v2/v3 mRNA species are minor form variants in human livers from most individuals.

Coexistence of Gilbert syndrome with hereditary haemolytic anaemias

Background

Gilbert syndrome is an inherited disease characterised by mild unconjugated hyperbilirubinaemia caused by mutations in UGT1A1 gene which lead to decreased activity of UDP-glucuronosyltransferase 1A1. The most frequent genetic defect is a homozygous TA dinucleotide insertion in the regulatory TATA box in the UGT1A1 gene promoter.

Methods and results

182 Polish healthy individuals and 256 patients with different types of hereditary haemolytic anaemias were examined for the A(TA)nTAA motif. PCR was performed using sense primer labelled by 6-Fam and capillary electrophoresis was carried out in an ABI 3730 DNA analyser. The frequency of the (TA)7/(TA)7 genotype in the control group was estimated at 18.13%, (TA)6/(TA)7 at 45.05% and (TA)6/(TA)6 at 36.26%. There was a statistically significant difference in the (TA)6/(TA)6 genotype distribution between healthy individuals and patients with glucose-6-phosphate dehydrogenase deficiency (p=0.041). Additionally, uncommon genotypes, (TA)5/(TA)6, (TA)5/(TA)7 and (TA)7/(TA)8 of the promoter polymorphism, were discovered.

Conclusion

Genotyping of the UGT1A1 gene showed distinct distribution of the common A(TA)nTAA polymorphism relative to other European populations. Because of a greater risk of hyperbilirubinaemia due to hereditary haemolytic anaemia, the diagnosis of Gilbert syndrome in this group of patients is very important.

Relationship between baseline hepatic status and outcome, and effect of sorafenib on liver function: SHARP trial subanalyses

BACKGROUND & AIMS

Hepatic markers are utilized in many classification systems of patients with hepatocellular carcinoma and, by measuring organ damage and tumor stage, can influence treatment. Moreover, elevated serum concentrations of aminotransferases and alpha-fetoprotein are indicators of poor prognosis in patients with hepatocellular carcinoma. We examined the effects of sorafenib on hepatic markers by performing exploratory subset analyses of the Sorafenib HCC Assessment Randomized Protocol (SHARP) trial in patients categorized by baseline concentrations of alanine aminotransferase/aspartate aminotransferase, alpha-fetoprotein, and bilirubin; and by evaluating the effects of sorafenib on bilirubin concentrations during treatment.

METHODS

Patients (n=602) were grouped by baseline concentrations of alanine aminotransferase/aspartate aminotransferase (not significantly elevated, mildly elevated, or moderately elevated), alpha-fetoprotein (normal or elevated), and bilirubin (normal or elevated). Bilirubin was measured at baseline and on day 1 of each cycle.

RESULTS

Patients with elevated baseline concentrations of alanine aminotransferase/aspartate aminotransferase, alpha-fetoprotein, or bilirubin had shorter overall survival (OS) than those with normal baseline concentrations, irrespective of treatment group. No notable differences in safety profiles were observed between patients with normal vs. elevated alanine aminotransferase/aspartate aminotransferase, alpha-fetoprotein, or bilirubin. Median changes from baseline in bilirubin concentration at the last cycle of treatment were +0.17 and +0.19 mg/dl in the sorafenib and placebo groups, respectively.

CONCLUSIONS

These subset analyses suggest that sorafenib is safe and effective for hepatocellular carcinoma, irrespective of baseline alanine aminotransferase/aspartate aminotransferase, alpha-fetoprotein, or bilirubin concentration and that hepatic function remains stable over the course of sorafenib therapy.

Cigarette smoking and serum bilirubin subtypes in healthy Korean men: the Korea Medical Institute study

OBJECTIVES

Cigarette smoking is a modifiable risk factor for cardiovascular disease. Bilirubin is a potent antioxidant and its concentration decreases in smokers. However, studies about the association between cigarette smoking and bilirubin are scarce and most are limited to total bilirubin. Additionally, bilirubin is highly related to hemoglobin. Therefore, this study evaluates the association between bilirubin subtypes and cigarette smoking in healthy Korean men independently of hemoglobin.

METHODS

This study included 48 040 Korean men aged 30 to 87 years who visited the Korea Medical Institute for routine health examinations from January to December, 2007. The association of smoking with total, direct, and indirect bilirubin was assessed by logistic regression analysis taking into consideration differences in subjects and smoking characteristics.

RESULTS

Current smokers had lower bilirubin concentrations than never-smokers and ex-smokers. Smoking amount and duration were inversely significantly associated with total, direct, and indirect bilirubin. In a multivariable adjusted model, compared to never-smokers, the odds ratios (ORs) and 95% confidence intervals (CIs) of current smokers with the highest number of pack-years were 1.7 (1.6 to 1.9) for total, 1.5 (1.4 to 1.6) for direct, and 1.7 (1.6 to 1.9) for indirect bilirubin. After further adjustment for hemoglobin, this association became stronger (OR [95% CI], 2.1 [1.9 to 2.2] for total; 1.9 [1.8 to 2.0] for direct; 2.0 [1.9 to 2.2] for indirect bilirubin).

CONCLUSIONS

In this study, bilirubin subtypes are inversely associated with smoking status, smoking amount, and smoking duration in healthy Korean men independently of hemoglobin. Further studies are needed to investigate this association in healthy Korean women.

Total, direct, and indirect serum bilirubin concentrations and metabolic syndrome among the Korean population

Total bilirubin, not direct or indirect bilirubin, has been reported to associate inversely with metabolic syndrome. Therefore, we aimed to evaluate the association between bilirubin subtypes and metabolic syndrome among the Korean population. This study included 5,231 Koreans (3,008 men, 2,223 women) aged 30-87 years, who visited the Health promotion centers in Seoul from April, 2006 to June, 2007. The associations of direct, indirect, and total bilirubin classified in quartiles with metabolic syndrome were measured by logistic regression analyses in men and women. Odds ratios (95% confidence intervals) of the lowest, 2nd and 3rd quartiles of direct serum bilirubin compared with the highest quartile (reference) were 2.3 (1.6-3.2), 1.8 (1.3-2.4), and 1.8 (1.4-2.4) among men, and 5.5 (2.6-11.5), 3.1 (1.5-6.7), and 1.9 (0.9-4.3) among women, respectively. In a multivariable adjusted model, however, the significance of inverse associations with total and indirect bilirubin became attenuated. The relation was consistent particularly with direct bilirubin in subgroups of metabolic syndrome components such as central obesity, hypertriglyceridemia, hyperglycemia, and low HDL-cholesterol in both men and women. Of the three subtypes of serum bilirubin, the inverse association of metabolic syndrome was significantly apparent and consistent with direct bilirubin.

Advances of molecular clinical pharmacology in gastroenterology and hepatology

During developmental age, differences in pharmacodynamic reactions to several drugs may reflect polymorphisms of genes encoding drug-transporting proteins, receptors, drug targets, and gene products, whose disturbed activity sometimes plays an important role in certain diseases. Administration of drugs with a narrow therapeutic index may quite easily be associated with changes in pharmacokinetics and development of adverse drug reactions, which occasionally may cause fatalities. In such cases, polypragmasy and resulting drug interactions may enhance effects of changes in drug-metabolizing enzymes' activities. Phenotyping and genotyping of patients slowly are finding their place in some therapeutic regimens used in clinical gastroenterology and hepatology. At present, some assays to measure, for example, thiopurine S-methyltransferase activity are already commercially available. Polymorphisms of CYP450 enzymes, interleukins, and altered gene expression play an important role in some patients' various gastrointestinal tract and liver diseases. Herbal drugs also affect proinflammatory and antiinflammatory cytokine and nitric oxide balance in the body. Therapeutic use of recombined proteins, such as infliximab, natalizumab, onercept, humanized antibody to integrin α-4 β-7, or IFN-β in some large-bowel diseases increased therapeutic efficacy. IFN-α used in the patients with chronic hepatitis C improved cellular immunity in these subjects and exerted antiviral activity. Practical application of progress in pharmacogenetics, pharmacokinetics, pharmacodynamics, and use of bioproducts in novel therapeutic regimens has opened therapeutic frontiers and increased clinical safety.

Polymorphic variants of UGT1A1 in neonatal jaundice in southern Brazil

Alterations in the hepatic conjugation of bilirubin due to uridyl-diphosphate-glucuronosyltransferase 1A1 (UGT1A1) polymorphisms have been proposed as risk factors to neonatal jaundice. Herein, we estimated the frequency of genotypes of the promoter region of UGT1A1 gene in newborns and evaluated its association with severe hyperbilirubinemia. Prospective study of cases and controls including all newborns admitted for phototherapy at HCPA, Brazil, during 9 months; 490 babies were enrolled and PCR was performed. Polymorphic genotypes were detected in 16% of the patients and 7 of the 10 possible genotypes were identified with higher prevalence of polymorphisms in Afro-descendants. In this sample, the variants of UGT1A1 were not associated to severe hyperbilirubinemia; other genic factors should be sought in this high miscegenation area of Brazil.

The clinical application of UGT1A1 pharmacogenetic testing: gene-environment interactions

Over the past decade, the number of pharmacogenetic tests has increased considerably, allowing for the development of our knowledge of their clinical application. The uridine diphosphate glucuronosyltransferase 1A1 gene (UGT1A1) assay is an example of a pharmacogenetic test. Numerous variants have been found in UGT1A1, the main conjugating enzyme of bilirubin and drugs such as the anticancer drug irinotecan. Recently, the US Food and Drug Administration (FDA) recommended testing for the presence of UGT1A1*28, an allele correlated with decreased transcriptional activity, to predict patients at risk of irinotecan toxicity. The administration of other drugs -- such as inhibitors of the UGT1A1 enzyme -- can clinically mimic the *28 phenotype, whereas inducers of UGT1A1 can increase the glucuronidation rate of the enzyme. The *28 polymorphism is not present in all ethnicities at a similar frequency, which suggests that it is important to study different populations to determine the clinical relevance of testing for UGT1A1*28 and to identify other clinically relevant UGT1A1 variants. Environmental factors such as lifestyle can also affect UGT1A1 activity. This review is a critical analysis of studies on drugs that can be affected by the presence of UGT1A1*28, the distribution of this polymorphism around the globe, distinct variants that may be clinically significant in African and Asian populations and how lifestyle can affect treatment outcomes that depend on UGT1A1 activity.

Pegvisomant-induced liver injury is related to the UGT1A1*28 polymorphism of Gilbert's syndrome

CONTEXT

Pegvisomant (PEG) therapy has been associated with drug-induced liver dysfunction in acromegalic patients. The mechanism of its toxicity remains unknown.

OBJECTIVE

The primary objective was to determine whether or not the UGT1A1*28 polymorphism associated with Gilbert's syndrome influences the development of liver dysfunction during PEG treatment.

DESIGN AND SETTING

A cross-sectional study was conducted in four Spanish university hospitals.

PATIENTS

Thirty-six acromegalic patients with active disease, resistant to somatostatin analogs, participated.

RESULTS

The prevalence of the UGT1A1*28 homozygous and heterozygous genotypes in acromegalic patients was 14 and 44%, respectively. Ten patients (28%) developed liver function test (LFT) abnormalities. There was a tendency for more frequent liver function abnormalities in males (70% males vs. 30% females, P = 0.058). Carriers of the UGT1A1*28 polymorphism had a higher incidence of LFT abnormalities than the UGT1A1 wild type (43% carriers vs. 7% wild type, P = 0.024). This difference persisted when adjusted in an all-factors multiple regression analysis [coefficient of determination (R(2)) = 0.463; P = 0.008] for age, gender, alcohol consumption, and UGT1A1*28 polymorphism. A stepwise multivariate likelihood binary logistic regression analysis (R(2) = 0.40; P = 0.003) identified male gender (beta = 7.21; P = 0.033) and UGT1A1*28 polymorphism (beta = 14.1; P = 0.028) as the only significant predictors for the development of LFT abnormalities.

CONCLUSIONS

The UGT1A1*28 genotype and male gender predict an increased incidence of LFT abnormalities during PEG therapy in acromegaly.

Developmental hyperbilirubinemia and CNS toxicity in mice humanized with the UDP glucuronosyltransferase 1 (UGT1) locus

High levels of unconjugated bilirubin (UCB) in newborn children is associated with a reduction in hepatic UDP glucuronosyltransferase (UGT) 1A1 activity that can lead to CNS toxicity, brain damage, and even death. Little is known regarding those events that lead to UCB accumulation in brain tissue, and therefore, we sought to duplicate this condition in mice. The human UGT1 locus, encoding all 9-UGT1A genes including UGT1A1, was expressed in Ugt1(-/-) mice. Because the most common clinical condition associated with jaundice in adults is Gilbert's syndrome, which is characterized by an allelic polymorphism in the UGT1A1 promoter, hyperbilirubinemia was monitored in humanized UGT1 mice that expressed either the Gilbert's UGT1A1*28 allele [Tg(UGT1(A1*28))Ugt1(-/-) mice] or the normal UGT1A1*1 allele [Tg(UGT1(A1*1))Ugt1(-/-) mice]. Adult Tg(UGT1(A1*28))Ugt1(-/-) mice expressed elevated levels of total bilirubin (TB) compared with Tg(UGT1(A1*1))Ugt1(-/-) mice, confirming that the promoter polymorphism associated with the UGT1A1*28 allele contributes to hyperbilirubinemia in mice. However, TB accumulated to near toxic levels during neonatal development, a finding that is independent of the Gilbert's UGT1A1*28 promoter polymorphism. Whereas serum TB levels eventually returned to adult levels, TB clearance in neonatal mice was not associated with hepatic UGT1A1 expression. In approximately 10% of the humanized UGT1 mice, peak TB levels culminated in seizures followed by death. UCB deposition in brain tissue and the ensuing seizures were associated with developmental milestones and can be prevented by enhancing regulation of the UGT1A1 gene in neonatal mice.

Correction of venlafaxine- and duloxetine-induced transaminase elevations with desvenlafaxine in a patient with Gilbert's syndrome

Recent reviews have questioned whether the serotonin-norepinephrine reuptake inhibitor (SNRI) desvenlafaxine succinate offers any practical clinical advantages over existing SNRIs. The following case is one instance where it appears that this SNRI offers unique safety and benefit. Presented is a case report of a patient with Gilbert's syndrome, longstanding social phobia, and more recent depressive disorder not otherwise specified, who was found to have elevated liver transaminases when prescribed both duloxetine and venlafaxine. The patient subsequently responded to desvenlafaxine but without liver abnormalities. In this patient with Gilbert's Syndrome, desvenlafaxine's lack of metabolism through the cytochrome P450 (CYP) 2D6 pathway may explain the avoidance of these abnormalities and thus suggests a possible therapeutic role for this SNRI in similarly susceptible patients.

UDP-glucuronosyltransferase 1A10: activity against the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol, and a potential role for a novel UGT1A10 promoter deletion polymorphism in cancer susceptibility

The extrahepatic UDP-glucuronosyltransferase 1A10 (UGT1A10) is a phase II metabolizing enzyme that is active against a number of potent carcinogens. In the present study, UGT1A10 was examined for activity against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), the major procarcinogenic metabolite of the potent tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, and the promoter region of UGT1A10 was examined for variants that could lead to altered UGT1A10 expression. UGT1A10-overexpressing cell homogenates exhibited high O-glucuronidation activity against NNAL (K(M) = 5.95 mM). A 2000-base pair (bp) product corresponding to the UGT1A10 proximal promoter region was polymerase chain reaction (PCR)-amplified using genomic DNA from 97 white subjects, and 42 of these were sequenced. In addition to a previously reported C/G single-nucleotide polymorphism at -1271 bp (rs2741032), a novel 1664-bp deletion located between nucleotides -190 to -1856 relative to the UGT1A10 translation start site was identified. Using real-time multiplex PCR, this deletion exhibited a prevalence of 0.022 in whites (n = 156) and 0.056 in blacks (n = 133). To determine whether either polymorphism altered gene expression, in vitro assays were performed using luciferase constructs containing up to 2000 bp of the proximal UGT1A10 promoter. Constructs containing the 1664-bp deletion exhibited a significant (p = 0.009) 3-fold increase in luciferase activity compared with constructs containing the wild-type UGT1A10 promoter. No effect on luciferase activity was observed for the UGT1A10(-1271G) promoter variant. These data are consistent with previous studies that indicate the presence of a transcriptional repressor element within the newly identified deletion and that this deletion polymorphism may contribute to altered UGT1A10 expression and altered carcinogen detoxification between individuals.