UDP-glucuronosyltransferase 1A7 polymorphisms are associated with liver cirrhosis. Biochem Biophys Res Commun. 2008;366:643-648. [PMID: 18054330 DOI: 10.1016/j.bbrc.2007.11.125]

UDP-glucuronosyltransferases mediate coffee-associated reduction of liver fibrosis in bile duct ligated humanized transgenic UGT1A mice

BACKGROUND

Coffee consumption has been shown to reduce the risk of liver fibrosis and is capable of inducing human UDP-glucuronosyltransferase (UGT) 1A genes. UGT1A enzymes act as indirect antioxidants catalyzing the elimination of reactive metabolites, which in turn are potent initiators of profibrotic mechanisms. The aim of this study was to analyze the role of UGT1A genes as effectors of the protective properties of coffee in bile duct ligation (BDL) induced liver fibrosis.

METHODS

Fourteen days BDL with and without coffee pre- and co-treatment was performed in htgUGT1A-WT and htgUGT1A-SNP mice. Hepatic UGT1A mRNA expression levels, serum bilirubin and aminotransferase activities were determined. Liver fibrosis was assessed by collagen deposition, computational analysis of Sirius red tissue staining and expression of profibrotic marker genes. Oxidative stress was measured by hepatic peroxidase concentrations and immunofluorescence staining.

RESULTS

UGT1A transcription was differentially activated in the livers of htgUGT1A-WT mice after BDL, in contrast to a reduced or absent induction in the presence of SNPs. Co-treated (coffee + BDL) htgUGT1A-WT-mice showed significantly increased UGT1A expression and protein levels and a considerably higher induction compared to water drinking WT mice (BDL), whereas in co-treated htgUGT1A-SNP mice absolute expression levels remained below those observed in htgUGT1A-WT mice. Collagen deposition, oxidative stress and the expression of profibrotic markers inversely correlated with UGT1A expression levels in htgUGT1A-WT and SNP mice after BDL and coffee + BDL co-treatment.

CONCLUSIONS

Coffee exerts hepatoprotective and antioxidative effects via activation of UGT1A enzymes. Attenuated hepatic fibrosis as a result of coffee-mediated UGT1A induction during cholestasis was detected, while the protective action of coffee was lower in a common low-function UGT1A SNP haplotype present in 10% of the Caucasian population. This study suggests that coffee consumption might constitute a potential strategy to support the conventional treatment of cholestasis-related liver diseases.

Regulation of uridine diphosphate-glucuronosyltransferase 1A expression by miRNA-214-5p and miRNA-486-3p

Aim: This study aimed to identify novel miRNAs (miRs) as regulators of UGT1A gene expression and to evaluate them as potential risk factors for the development of liver fibrosis/cirrhosis. Materials & methods: miRNA target sites in UDP-glucuronosyltransferase 1A (UGT1A) 3'-UTR were predicted and confirmed by luciferase assays, quantitative real-time PCR and western blot using HEK293, HepG2 and Huh7 cells. UGT1A and miRNA expression were analyzed in cirrhotic patients and a mouse model of alcoholic liver fibrosis. Results: miR-214-5p and miR-486-3p overexpression reduced UGT1A mRNA, protein levels and enzyme activity in HepG2 and Huh7 cells. miR-486-3p was upregulated in cirrhotic patients and fibrotic mice livers, whereas UGT1A mRNA levels were reduced. Conclusion: In conclusion, we identified two novel miRNAs capable to repress UGT1A expression in vitro and in vivo. Furthermore, miR-486-3p may represent a potential risk factor for the development or progression of liver fibrosis/cirrhosis by means of a reduced UGT1A-mediated detoxification activity.

A Gilbert syndrome-associated haplotype protects against fatty liver disease in humanized transgenic mice

UDP-glucuronosyltransferases 1 A (UGT1A) enzymes are capable of detoxifying a broad range of endo- and xenobiotic compounds, which contributes to antioxidative effects, modulation of inflammation and cytoprotection. In the presence of low-function genetic UGT1A variants fibrosis development is increased in various diseases. This study aimed to examine the role of common UGT1A polymorphisms in NASH. Therefore, htgUGT1A-WT mice and htgUGT1A-SNP mice (carrying a common human haplotype present in 10% of the white population) were fed a high-fat Paigen diet for 24 weeks. Serum aminotransferase activities, hepatic triglycerides, fibrosis development and UGT1A expression were assessed. Microscopic examination revealed higher hepatic fat deposition and a significant induction of UGT1A gene expression in htgUGT1A-WT mice. In agreement with these observations, lower serum aminotransferase activities and lower expression levels of fibrosis-related genes were measured in htgUGT1A-SNP mice. This was accompanied by reduced PPARα protein levels in htgUGT1A-WT but not in SNP mice. Our data demonstrate a protective effect of a UGT1A SNP haplotype, leading to milder hepatic steatosis and NASH. Higher PPARα protein levels in animals with impaired UGT1A activity are the likely result of reduced glucuronidation of ligands involved in PPARα-mediated fatty acid oxidation and may lead to the observed protection in htgUGT1A-SNP mice.

Characterizing key nucleotide polymorphisms of hepatitis C virus-disease associations via mass-spectrometric genotyping

As more than 80% of hepatocellular carcinoma patients in Japan also suffer from hepatitis C virus infections some time in their medical history, identifying genetic aberrations associated to hepatitis C virulence in these individuals remains a high priority in the diagnosis and treatment of hepatocellular carcinoma. From the BioBank Japan Project, we acquired 480 subjects of hepatocellular carcinoma, chronic hepatitis and liver cirrhosis, and genotyped 131 clinically relevant host single nucleotide polymorphisms to survey the potential association between certain risk alleles and genes to a patient's predisposition to hepatitis C and liver cancer. Among those polymorphisms, we found 12 candidates with statistical significance to support association with hepatitis C virus susceptibility and genetic predisposition to hepatocellular carcinoma. SNPs in genes such as XPC, FANCA, KDR and BRCA2 also suggested likely connections between hepatitis C virus susceptibility and the contraction of liver diseases. Single nucleotide polymorphisms reported here provided suggestions for genes as biomarkers and elucidated insights briefing the linkage of hepatitis C virulence to the alteration of healthy liver genomic landscape as well as liver disease progression.

Molecular changes in hepatic metabolism and transport in cirrhosis and their functional importance

Liver cirrhosis is the common endpoint of many hepatic diseases and represents a relevant risk for liver failure and hepatocellular carcinoma. The progress of liver fibrosis and cirrhosis is accompanied by deteriorating liver function. This review summarizes the regulatory and functional changes in phase I and phase II metabolic enzymes as well as transport proteins and provides an overview regarding lipid and glucose metabolism in cirrhotic patients. Interestingly, phase I enzymes are generally downregulated transcriptionally, while phase II enzymes are mostly preserved transcriptionally but are reduced in their function. Transport proteins are regulated in a specific way that resembles the molecular changes observed in obstructive cholestasis. Lipid and glucose metabolism are characterized by insulin resistance and catabolism, leading to the disturbance of energy expenditure and wasting. Possible non-invasive tests, especially breath tests, for components of liver metabolism are discussed. The heterogeneity and complexity of changes in hepatic metabolism complicate the assessment of liver function in individual patients. Additionally, studies in humans are rare, and species differences preclude the transferability of data from rodents to humans. In clinical practice, some established global scores or criteria form the basis for the functional evaluation of patients with liver cirrhosis, but difficult treatment decisions such as selection for transplantation or resection require further research regarding the application of existing non-invasive tests and the development of more specific tests.

Changes in portal blood flow and liver functions in cirrhotics during Ramadan fasting in the summer; a pilot study

AIM

Assessment of short term changes in portal blood flow and long term changes in liver functions in cirrhotic patients who chose to fast during the month of Ramadan in summer.

BACKGROUND

During Ramadan, healthy Muslims obligated to fast from predawn to sunset.

PATIENTS AND METHODS

Forty cirrhotic patients intended to fast during the month of Ramadan in the year 2014, were examined by Congestion index (CI) as a non-invasive indicator of short term changes in the portal blood flow, while liver function tests were determined as an indicator of long term changes in liver functions.

RESULTS

A total of 38 patients completed the whole month fasting and two patients discontinued fasting due to variceal bleeding. The complicated patients were 7. CI showed a statistically significant increase from fasting to postprandial status (P<0.001), with statistically significant increases from fasting to postprandial status in Child class A (P<0.001), and B (P<0.001). We did not find a statistical significance between patients with complications and those without complications (P=0.6). There was a statistically significant rise in the serum bilirubin after Ramadan. Deterioration noticed as advanced Child classes, development of lower limb edema, increasing ascites, increasing jaundice and overt encephalopathy.

CONCLUSION

Cirrhotic patients showed significant short-term changes in the portal blood flow. However, these changes are not linked to complications or deterioration of liver functions and accommodated especially in patients with Child class A and B. Child class C patients should not fast.

Comparison of intestinal absorption and disposition of structurally similar bioactive flavones in Radix Scutellariae

Radix Scutellariae is a commonly used herbal medicine. Baicalein, wogonin, and oroxylin A are three major bioactive flavones in Radix Scutellariae and share similar chemical structures. The intestinal absorption and disposition of baicalein have been systematically investigated by our group before. In this study, the intestinal absorption and disposition of wogonin and oroxylin A were further explored and compared with the profiles of baicalein to find potential structure-activity relationship. Absorptive models including Caco-2 cell monolayer model and rat in situ single-pass intestinal perfusion model as well as in vitro enzymatic kinetic study were employed in the current study. The absorption of baicalein, wogonin, and oroxylin A were favorable with wogonin showing the highest permeability based on two absorptive models. However, three flavones underwent a fast and extensive phase II metabolism. The intestinal metabolism of three flavones exhibited species difference between human and rat. Oroxylin A demonstrated the highest intrinsic clearance of glucuronidation among three flavones. The multidrug resistance proteins might be involved in the efflux of their intracellularly formed conjugated metabolites. The pathway of intestinal absorption and disposition of B, W, and OA was similar. However, the extent of permeability and metabolism was different among three flavones which might be due to the number and position of the hydroxyl group.

Genetic polymorphism in metabolism and host defense enzymes: implications for human health risk assessment

Genetic polymorphisms in xenobiotic metabolizing enzymes can have profound influence on enzyme function, with implications for chemical clearance and internal dose. The effects of polymorphisms have been evaluated for certain therapeutic drugs but there has been relatively little investigation with environmental toxicants. Polymorphisms can also affect the function of host defense mechanisms and thus modify the pharmacodynamic response. This review and analysis explores the feasibility of using polymorphism data in human health risk assessment for four enzymes, two involved in conjugation (uridine diphosphoglucuronosyltransferases [UGTs], sulfotransferases [SULTs]), and two involved in detoxification (microsomal epoxide hydrolase [EPHX1], NADPH quinone oxidoreductase I [NQO1]). This set of evaluations complements our previous analyses with oxidative and conjugating enzymes. Of the numerous UGT and SULT enzymes, the greatest likelihood for polymorphism effect on conjugation function are for SULT1A1 (*2 polymorphism), UGT1A1 (*6, *7, *28 polymorphisms), UGT1A7 (*3 polymorphism), UGT2B15 (*2 polymorphism), and UGT2B17 (null polymorphism). The null polymorphism in NQO1 has the potential to impair host defense. These highlighted polymorphisms are of sufficient frequency to be prioritized for consideration in chemical risk assessments. In contrast, SNPs in EPHX1 are not sufficiently influential or defined for inclusion in risk models. The current analysis is an important first step in bringing the highlighted polymorphisms into a physiologically based pharmacokinetic (PBPK) modeling framework.

Hepatocellular carcinoma displays distinct DNA methylation signatures with potential as clinical predictors

BACKGROUND

Hepatocellular carcinoma (HCC) is characterized by late detection and fast progression, and it is believed that epigenetic disruption may be the cause of its molecular and clinicopathological heterogeneity. A better understanding of the global deregulation of methylation states and how they correlate with disease progression will aid in the design of strategies for earlier detection and better therapeutic decisions.

METHODS AND FINDINGS

We characterized the changes in promoter methylation in a series of 30 HCC tumors and their respective surrounding tissue and identified methylation signatures associated with major risk factors and clinical correlates. A wide panel of cancer-related gene promoters was analyzed using Illumina bead array technology, and CpG sites were then selected according to their ability to classify clinicopathological parameters. An independent series of HCC tumors and matched surrounding tissue was used for validation of the signatures. We were able to develop and validate a signature of methylation in HCC. This signature distinguished HCC from surrounding tissue and from other tumor types, and was independent of risk factors. However, aberrant methylation of an independent subset of promoters was associated with tumor progression and etiological risk factors (HBV or HCV infection and alcohol consumption). Interestingly, distinct methylation of an independent panel of gene promoters was strongly correlated with survival after cancer therapy.

CONCLUSION

Our study shows that HCC tumors exhibit specific DNA methylation signatures associated with major risk factors and tumor progression stage, with potential clinical applications in diagnosis and prognosis.

Variability and function of family 1 uridine-5'-diphosphate glucuronosyltransferases (UGT1A)

The substrate spectrum of human UDP-glucuronosyltransferase 1A (UGT1A) proteins includes the glucuronidation of non-steroidal anti-inflammatory drugs, anticonvulsants, chemotherapeutics, steroid hormones, bile acids, and bilirubin. The unique genetic organization of the human UGT1A gene locus, and an increasing number of functionally relevant genetic variants define tissue specificity as well as a broad range of interindividual variabilities of glucuronidation. Genetic UGT1A variability has been conserved throughout the protein's evolution and shows ethnic diversity. It is the biochemical and genetic basis for clinical phenotypes such as Gilbert's syndrome and Crigler-Najjar's disease as well as for the potential for severe, unwanted drug side effects such as in irinotecan treatment. UGT1A variants influence the metabolic effects of xenobiotic exposure and therefore have been linked to cancer risk. Detailed knowledge of the organization, function, and pharmacogenetics of the human UGT1A gene locus is likely to significantly contribute to the improvement of drug safety and efficacy as well as to the provision of steps toward the goal of individualized drug therapy and disease risk prediction.