UDP-glucuronyl Transferase 1A1 Research Articles

Oleanolic acid alleviates ANIT-induced cholestatic liver injury by activating Fxr and Nrf2 pathways to ameliorate disordered bile acids homeostasis

Cholestasis is a clinical syndrome with high incidence and few effective treatments. Oleanolic acid (OA) is a triterpenoid compound with anti-cholestatic effects. Studies using bile duct ligation or lithocholic acid modeling have shown that the alleviating effect of OA on cholerosis is related to the regulation of nuclear factor erythroid 2 related factor (Nrf2) or farnesoid X receptor (Fxr). This study aims to investigate the underlying mechanism of OA against alpha-naphthylisothiocyanate (ANIT)-induced cholestatic liver injury based on Nrf2 and Fxr dual signaling pathways. The ANIT-induced rats model was used with or without OA treatment. Serum biochemical indexes, liver histopathological changes and glutathione level were examined. Bile acids (BAs) targeted metabolomics based on UHPLC-MS/MS were performed. siRNA, RT-qPCR and western blot analysis were used to prove the role of Fxr and Nrf2 pathway in OA's anti-cholestatic liver injury in vivo and in vitro. OA significantly alleviated ANIT-induced liver injury in rats, reduced primary bile acids, accelerated metabolism of BAs and reduced the intrahepatic accumulation of BAs. The expressions of bile salt export pump (Bsep), Na+-taurocholic cotransport polypeptide (Ntcp), UDP-glucuronyl transferase 1a1 (Ugt1a1) and Fxr in rat liver were markedly up-regulated, the activation of Nrf2 was promoted, and the expression of cholesterol 7α-hydroxylase (Cyp7a1) was decreased after OA treatment. Moreover, Fxr or Nrf2 silencing attenuated the regulation of OA on BAs homeostasis related transporters and enzymes in rat primary hepatocytes. OA may regulate BAs-related transporters and metabolic enzymes by activating Fxr and Nrf2 pathways, thus alleviating the cholestatic liver injury induced by ANIT.

In Vitro Validation of miRNA-Mediated Gene Expression Linked to Drug Metabolism.

Pharmacogenomic approaches used to investigate how genes affect drug responses are critical for designing personalized therapies aimed at maximizing efficacy and minimizing adverse effects. Drug efficacy is often dependent on the sequence and expression levels of drug target genes or those involved in the metabolism and transport of the therapeutic agent. Expression of these genes, in turn, is negatively regulated by small noncoding miRNAs. The levels of miRNAs in bodily fluids have been studied extensively as potential diagnostic and prognostic biomarkers. Studies have shown that miRNAs regulate multiple genes and sequence homology is used to predict which genes are subject to regulation by a particular miRNA. Once a gene is identified as a potential target for an miRNA of interest, experiments are undertaken to confirm that the miRNA interacts with the target gene and can alter its level of expression and/or its activity. For example, the differential expression of miRNAs in whole blood obtained from good and poor responders to ketamine has been reported both prior to, and following treatment for complex regional pain syndrome. In this case, hsa-miR-548d-5p was significantly lower in poor responders relative to good responders. This miRNA was predicted to target UDP-glucuronyl transferase 1A1 (UGT1A1), a key drug metabolizing enzyme. Described in this unit are protocols used to confirm miR-548d-5p-mediated UGT1A1 regulation. The approaches described can be employed broadly for the validation of miRNA-mediated negative regulation of any gene. Determining miRNA-mediated regulation of enzymes and transporters affecting drug metabolism is a critical step in designing personalized therapy and for understanding the mechanisms responsible for variations in the responses to therapeutic agents. © 2017 by John Wiley & Sons, Inc.

Spectrum of UGT1A1 Variations in Chinese Patients with Crigler-Najjar Syndrome Type II.

Crigler–Najjar Syndrome type II (CNS-II) is an autosomal recessive hereditary condition of unconjugated hyperbilirubinemia without hemolysis, with bilirubin levels ranging from 102.6 μmol/L to 342 μmol/L. CNS-II is caused by a deficiency of UDP-glucuronyl transferase (UGT), which is encoded by the UDP-glucuronyl transferase 1A1 gene (UGT1A1). In East Asian populations, the compound homozygous UGT1A1 G71R and Y486D variants are frequently observed in cases with bilirubin levels exceeding 200 μmol/L. In this study, we investigated the spectrum of UGT1A1 variations in Chinese CNS-II patients. We sequenced the enhancer, promoter, and coding regions of UGT1A1 in 11 unrelated Chinese CNS-II patients and 80 healthy controls. Nine of these patients carried variations that are here reported for the first time in CNS-II patients, although they have been previously reported for other types of hereditary unconjugated hyperbilirubinemia. These individual variations have less influence on UGT activity than do the compound homozygous variation (combination of homozygous G71R variant and Y486D variant). Therefore, we propose that the spectrum of UGT1A1 variations in CNS-II differs according to the bilirubin levels.

Risk of Ischemic Stroke and Decreased Serum Bilirubin Levels

Bilirubin, often thought to be a toxic end product of heme, is a potent antioxidant compound in vivo.1,2 As shown in the schematic Figure, degraded red blood cells release heme, which is broken down by heme oxygenase to biliverdin, which is reduced by biliverdin reductase into the hydrophobic compound bilirubin. Unconjugated bilirubin is a lipid-soluble molecule that must be made water soluble to be excreted. Unconjugated bilirubin is carried by albumin to the liver, where it is conjugated into a water-soluble form by hepatic glucuronyl transferase. The hepatic enzyme UDP-glucuronyl transferase 1A1 (UGT1A1) converts bilirubin to a soluble (conjugated) form suitable for renal and biliary elimination.1,2 Importantly, in healthy European populations, common genetic variation of the UGT1A1 promoter region explains ≈50% of the variability in serum total (TB) and conjugated bilirubin levels.3 UGT1A1 is also responsible for the glucuronidation of many other small lipophilic molecules, such as steroid hormones and drugs that affect the vasculature.1,2 Figure. Schematic representation of the bilirubin metabolism and the putative biological mechanisms by which higher levels of serum bilirubin might exert vasoprotective effects on the development of silent brain infarcts and other cardiovascular complications. HO-1 indicates heme oxygenase-1. See accompanying article on page 946 Currently, ample evidence suggests that lower levels of TB are associated with increased risk of cardiovascular disease (CVD), independently of traditional risk factors.4–9 In 2012, further evidence for a possible beneficial role of bilirubin protecting against CVD was provided from a large UK primary care database (n=130 052 patients) with the measurement of TB levels recorded 3 months before first statin treatment. After a median of …

Pharmacokinetics and Pharmacogenomics of Once-Daily Raltegravir and Atazanavir in Healthy Volunteers

Atazanavir inhibits UDP-glucuronyl-transferase-1A1 (UGT1A1), which metabolizes raltegravir, but the magnitude of steady-state inhibition and role of the UGT1A1 genotype are unknown. Sufficient inhibition could lead to reduced-dose and -cost raltegravir regimens. Nineteen healthy volunteers, age 24 to 51 years, took raltegravir 400 mg twice daily (arm A) and 400 mg plus atazanavir 400 mg once daily (arm B), separated by ≥3 days, in a crossover design. After 1 week on each regimen, raltegravir and raltegravir-glucuronide plasma and urine concentrations were measured by liquid chromatography-tandem mass spectrometry in multiple samples obtained over 12 h (arm A) or 24 h (arm B) and analyzed by noncompartmental methods. UGT1A1 promoter variants were detected with a commercially available kit and published primers. The primary outcome was the ratio of plasma raltegravir C(tau), or concentration at the end of the dosing interval, for arm B (24 h) versus arm A (12 h). The arm B-to-arm A geometric mean ratios (95% confidence interval, P value) for plasma raltegravir C(tau), area under the concentration-time curve from 0 to 12 h (AUC(0-12)), and raltegravir-glucuronide/raltegravir AUC(0-12) were 0.38 (0.22 to 0.65, 0.001), 1.32 (0.62 to 2.81, 0.45), and 0.47 (0.38 to 0.59, <0.001), respectively. Nine volunteers were heterozygous and one was homozygous for a UGT1A1 reduction-of-function allele, but these were not associated with metabolite formation. Although atazanavir significantly reduced the formation of the glucuronide metabolite, its steady-state boosting of plasma raltegravir did not render the C(tau) with a once-daily raltegravir dose of 400 mg similar to the C(tau) with the standard twice-daily dose. UGT1A1 promoter variants did not significantly influence this interaction.

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.

Hereditary Spherocytosis in 3 Children Coexisting With UDP-glucuronyl Transferase 1A1 Deficiency

Simultaneous presence of hemolytic anemia and bilirubin UDP-glucuronosyltransferase deficiency is a possible cause of misdiagnosis. Seven-year-old and 17-year-old brothers and a 15-year-old sister consecutively suffered from aplastic crises. Although few spherocytes were present, the siblings and their mother had diagnoses of hereditary spherocytosis with flow cytometric analysis of eosin-5'-maleimide-labeled red blood cells in addition to osmotic fragility test. However, inappropriately high values of bilirubin compared with mild hemolysis persisted. Further analysis of UDP-glucuronyltransferase 1A1 revealed all 3 siblings were heterozygous for A(TA)7TAA-P229Q. We report here the importance of careful evaluation of mild hereditary spherocytosis masking UDP-glucuronyltransferase 1A1 deficiency.

Life-Threatening Dextromethorphan Intoxication Associated with Interaction with Amitriptyline in a Poor CYP2D6 Metabolizer: A Single Case Re-Exposure Study

We report a case of life-threatening intoxication and a controlled re-exposure study to dextromethorphan. A 60-year-old man developed postsurgical neuropathic cervical pain treated by hydromorphone, gabapentin, clonazepam, and amitriptyline. He received a dextromethorphan preparation for a catarrhal syndrome. Two days later, he was admitted into an emergency department in a profound coma. Thirty-six hours later, after withdrawal of all drugs, the situation normalized. A genotyping for UDP-glucuronyltransferase 1A1 and CYP2D6 was followed by a re-exposure study. During the three days, vital parameters and side effects of drugs were prospectively recorded. The second day, dextromethorphan was introduced. No significant impairment in parameters nor influence on analgesic efficacy were noted. Dextromethorphan concentrations suggested an accumulation without reaching any steady state. Somnolence was noted for plasma concentrations around 100 ng/mL. The CYP2D6*4 variant leading to a poor metabolizer phenotype was found. Moreover, this phenotype was potentially aggravated by amitriptyline intake. This study allowed the identification and the confirmation of the cause of the coma. In conclusion, it is probably wise to recommend avoiding dextromethorphan in patients taking tricyclic antidepressants or another inhibitor of CYP2D6. Drug–drug interactions are probably underdiagnosed and underreported, and drugs considered as safe may induce serious complications.