Genetic polymorphisms of cytochrome p4502E1 and susceptibility to alcoholic liver disease and hepatocellular carcinoma in a white population: a study and literature review, including meta-analysis

Genetic polymorphism of the drug-metabolizing enzyme Cytochrome P4502E1 (CYP2E1) in a healthy Saudi population

Objectives

Cytochrome P450 2E1 (CYP2E1) is one of the major enzymes involved in the metabolism and detoxification of various drugs and xenobiotics. Polymorphisms in the CYP2E1 gene exhibit high inter-individual variations associated with alterations in CYP2E1 gene expression and enzyme function. This study aimed to determine the genotype distributions and allele frequencies of CYP2E1*1B, *5B, and *6 polymorphisms among Saudis in western Saudi Arabia.

Methods

In total, 140 healthy Saudis attending King Abdulaziz University Hospital between February and April 2021 were included in the study. CYP2E1 gene polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism analysis.

Results

The genotype frequencies of CYP2E1*1B A2A2, A2A1, and A1A1 were 54.29%, 40%, and 8%, respectively. The frequencies of CYP2E1*5B c1c1 and c1c2 genotypes were approximately 99.93% and 0.07%, respectively. The frequencies of the CYP2E1*6 DD, DC, and CC genotypes were 91.43%, 7.85%, and 0.72%, respectively. The genotype distributions for these polymorphisms were consistent with the expected distribution based on Hardy-Weinberg equilibrium. The allele frequencies were 74.29% A2 and 25.71% A1 for CYP2E1*1B, 99.64% c1 and 0.36% c2 for CYP2E1*5B, and 95.36% D and 4.65% C for CYP2E1*6.

Conclusion

The genotype distribution of CYP2E1*1B polymorphism was higher in the western Saudi population, whereas the CYP2E1*5B and *6 polymorphisms were lower than the global average. Knowledge of the prevalence of CYP2E1 polymorphisms among our population will provide a better understanding of whether individual patients might benefit from their medication or whether they might develop adverse effects.

Genetic Variants of Alcohol Metabolizing Enzymes and Alcohol-Related Liver Cirrhosis Risk

Alcohol-related liver disease (ARLD) is a major public health issue caused by excessive alcohol consumption. ARLD encompasses a wide range of chronic liver lesions, alcohol-related liver cirrhosis being the most severe and harmful state. Variations in the genes encoding the enzymes, which play an active role in ethanol metabolism, might influence alcohol exposure and hence be considered as risk factors of developing cirrhosis. We conducted a case-control study in which 164 alcohol-related liver cirrhosis patients and 272 healthy controls were genotyped for the following functional single nucleotide variations (SNVs): ADH1B gene, rs1229984, rs1041969, rs6413413, and rs2066702; ADH1C gene, rs35385902, rs283413, rs34195308, rs1693482, and rs35719513; CYP2E1 gene, rs3813867. Furthermore, copy number variations (CNVs) for ADH1A, ADH1B, ADH1C, and CYP2E1 genes were analyzed. A significant protective association with the risk of developing alcohol-related liver cirrhosis was observed between the mutant alleles of SNVs ADH1B rs1229984 (P_c value = 0.037) and ADH1C rs283413 (P_c value = 0.037). We identified CNVs in all genes studied, ADH1A gene deletions being more common in alcohol-related liver cirrhosis patients than in control subjects, although the association lost statistical significance after multivariate analyses. Our findings support that susceptibility to alcohol-related liver cirrhosis is related to variations in alcohol metabolism genes.

Genetic variants of ALDH2-rs671 and CYP2E1-rs2031920 contributed to risk of hepatocellular carcinoma susceptibility in a Chinese population

Objective

Acetaldehyde dehydrogenase 2 (ALDH2) and cytochrome P450 2E1 (CYP2E1) have been associated with hepatocellular carcinoma (HCC) susceptibility and prognosis. The polymorphisms ALDH2 rs671 and CYP2E1 rs2031920 are reportedly correlated with the prevalence of HCC in other countries. The aim of this study was to investigate associations between ALDH2 and CYP2E1, and HCC susceptibility in a population of Guangxi, southern China, an area with a high incidence of HCC.

Patients and methods

The study cohort included 300 HCC cases, 292 healthy controls for HCC susceptibility analysis, and another 20 HCC cases and 10 healthy controls for ascertainment. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism method.

Results

The study results demonstrated that mutant genotypes of ALDH2 (G/A and A/A) led to significant differences in HCC susceptibility, as compared with the wild genotype (G/G) with the same C1/C1 genotype in non-drinking individuals (adjusted P=0.010, OR=0.20, 95% CI=0.06–0.68). The mutant genotypes of CYP2E1 (C1/C2 and C2/C2) brought about significant differences in HCC susceptibility, as compared with the wild genotype (C1/C1) and the same G/G genotype (adjusted P=0.025, OR=0.42, 95% CI=0.20–0.90). Drinking plays a role in HCC susceptibility in the same G/G genotype individuals (adjusted P=0.004, OR=0.32, 95% CI=0.15–0.69), but had no impact when combined with CYP2E1 for analysis (all P>0.05).

Conclusion

These results suggest that the mutant genotypes of ALDH2 and CYP2E1 may be protective factors for HCC susceptibility in Guangxi province, China.

Myrtle berries seeds aqueous extract abrogates chronic alcohol consumption-induced erythrocytes osmotic stability disturbance, haematological and biochemical toxicity

BACKGROUND

This study examined the effects of chronic alcohol consumption in the rat erythrocytes membrane as well as the involvement of reactive oxygen species and proinflammatory cytokines in its pathogenicity in rats and evaluated the ameliorating effects of myrtle berries seeds aqueous extract (MBSAE).

METHODS

Fifty adult male Wistar rats were equally divided into five groups and treated daily for two months as follows: control, ethanol (3 g kg^- 1 b.w., p.o.), and ethanol + MBSAE (25, 50 and 100 mg kg^- 1, b.w., p.o.).

RESULTS

Exposure of rats to alcohol caused significant changes of some haematological parameters, enhanced erythrocytes hemolysis as well as an overproduction of reactive oxygen species such as H₂O₂, OH^• radical and superoxide anion, hence the increase of lipoperoxidation and the depletion of antioxidant enzymes activity as well as non-enzymatic antioxidant (-SH groups and GSH) levels. On the other hand, ethanol intoxication caused the increase of serum TNFα, IL-8, IL-6 and 1Lβ, markers of tissue inflammation. However, treatment with MBSAE alleviated all the deleterious effects of alcohol consumption.

CONCLUSIONS

MBSAE possess active compounds, which exert marked protective effects in chronic alcohol intoxication, possibly by regulating the erythrocytes osmotic stability as well as antioxidant and inflammatory mediators.

Alcohol-Derived Acetaldehyde Exposure in the Oral Cavity

Alcohol is classified by the International Agency for Research on Cancer (IARC) as a human carcinogen and its consumption has been associated to an increased risk of liver, breast, colorectum, and upper aerodigestive tract (UADT) cancers. Its mechanisms of carcinogenicity remain unclear and various hypotheses have been formulated depending on the target organ considered. In the case of UADT cancers, alcohol's major metabolite acetaldehyde seems to play a crucial role. Acetaldehyde reacts with DNA inducing modifications, which, if not repaired, can result in mutations and lead to cancer development. Despite alcohol being mainly metabolized in the liver, several studies performed in humans found higher levels of acetaldehyde in saliva compared to those found in blood immediately after alcohol consumption. These results suggest that alcohol-derived acetaldehyde exposure may occur in the oral cavity independently from liver metabolism. This hypothesis is supported by our recent results showing the presence of acetaldehyde-related DNA modifications in oral cells of monkeys and humans exposed to alcohol, overall suggesting that the alcohol metabolism in the oral cavity is an independent cancer risk factor. This review article will focus on illustrating the factors modulating alcohol-derived acetaldehyde exposure and effects in the oral cavity.

Meta-analysis of CYP2E1 polymorphisms in liver carcinogenesis

BACKGROUND

The CYP2E1 protein is a monooxygenase with certain polymorphisms linked to liver cancer. However, results from individual studies remain controversial.

AIMS

To evaluate CYP2E1 polymorphisms in liver carcinogenesis through meta-analysis.

METHODS

All studies about CYP2E1 polymorphisms and liver cancer were retrieved from seven major databases. Original data from each study were pooled and re-analyzed.

RESULTS

Total of 16 articles with 4862 cases were selected, including 1820 cases of liver cancer and 3042 cases of controls. The c1 allelic frequency in the cases and controls was 83.3% and 85.3%, respectively. Five genetic variations were compared: dominant c1c2/c2c2 vs. c1/c1 (OR=0.987 (0.853, 1.141)), homozygous c2c2 vs. c1c1 (OR=0.767 (0.526, 1.119)), heterozygous c1c2 vs. c1c1 (OR=1.005 (0.854, 1.182)), recessive c2c2 vs. c1c2/c2c2 (OR=0.771 (0.530, 1.122)), and different alleles c2 vs. c1 (OR=0.947 (0.828, 1.082)). Pooled data were further analyzed based on ethnicity, control sources, and HWE (Hardy-Weinberg equilibrium). These results from stratified groups were similar to that of nonstratified groups.

CONCLUSIONS

Our meta-analysis results suggest that there is no evidence for a major role of CYP2E1 polymorphism in liver carcinogenesis, but do not rule out the possibility in certain cases.

Alcoholic Liver Disease in Asia, Europe, and North America

Alcoholic liver diseases comprise a spectrum of clinical disorders and changes in liver tissue that can be detected by pathology analysis. These range from steatosis to more severe signs and symptoms of liver disease associated with inflammation, such as those observed in patients with alcoholic hepatitis or cirrhosis. Although the relationship between alcohol consumption and liver disease is well established, severe alcohol-related morbidities develop in only a minority of people who consume alcohol in excess. Inter-individual differences in susceptibility to the toxic effects of alcohol have been studied extensively-they include pattern of alcohol consumption, sex, environmental factors (such as diet), and genetic factors, which vary widely among different parts of the world. Alcoholic liver disease is becoming more common in many parts of Asia, but is decreasing in Western Europe. Treatment approaches, including availability of medications, models of care, and approach to transplantation, differ among regions.

The effect of CYP, GST, and SULT polymorphisms and their interaction with smoking on the risk of hepatocellular carcinoma

Aim. The aim of our study was to assess whether selected single nucleotide polymorphisms of CYP1A1 and 2E1, GSTM1, GSTT1, and SULT1A1 influence susceptibility towards HCC, considering their interaction with cigarette smoking. Methods. We recruited HCC cases and controls among patients admitted to the hospital "Agostino Gemelli," from January 2005 until July 2010. Odds ratios (OR) of HCC were derived from unconditional multiple logistic regression. Gene-gene and gene-smoking interaction were quantified by computing the attributable proportion (AP) due to biological interaction. Results. The presence of any CYP2E1 (*) 5B variant allele (OR: 0.23; 95% CI: 0.06-0.71) and CYP2E1 (*) 6 variant allele (OR: 0.08; 95% CI: 0.01-0.33) was inversely related to HCC. There was a borderline increased risk among carriers of combined CYP1A1 (*) 2A and SULT1A1 variant alleles (OR: 1.67; 95% CI: 0.97-3.24). A significant biological interaction was observed between GSTT1 and smoking (AP = 0.48; 95% CI: 0.001-0.815), with an OR of 3.13 (95% CI: 1.69-5.82), and borderline significant interaction was observed for SULT1A1 and smoking (AP = 0.36; 95% CI: -0.021-0.747), with an OR of 3.05 (95% CI: 1.73-5.40). Conclusion. CYP2E1 (*) 5B and CYP2E1 (*) 6 polymorphisms have a favourable effect on the development of HCC, while polymorphisms of GSTT1 and SULT1A1 might play role in increasing the susceptibility among smokers.

Systematic review with meta-analysis: the I148M variant of patatin-like phospholipase domain-containing 3 gene (PNPLA3) is significantly associated with alcoholic liver cirrhosis

BACKGROUND

Several studies have reported an association between alcoholic liver cirrhosis (ALC) or other forms of alcoholic liver disease (ALD) and the genetic variant rs738409 (C>G) in adiponutrin/patatin-like phospholipase domain-containing 3 gene (PNPLA3).

AIM

To evaluate the influence of this variant on ALC and other forms of ALD.

METHODS

We performed a systematic review of previous studies on the relationship between rs738409 of PNPLA3 and ALD and meta-analysis was conducted in a random-effects model. Calculations of the odds ratios (ORs) and their confidence intervals (CIs), tests for heterogeneity and sensitivity analyses were performed.

RESULTS

Database search identified 11 previous studies available for inclusion with a total of 3495 patients with ALD (2087 with ALC) and 5038 controls (4007 healthy subjects and 1031 alcoholics without ALD). Patients with ALC compared to controls had a significantly higher prevalence of the G allele when comparing GG vs. CC (OR 4.30, 95% CI 3.25-5.69; P < 0.00001) or GC vs. CC genotypes (GC vs. CC: OR 1.91, 95% CI 1.67-2.17) or under a recessive or dominant model. Similar results were found when comparing separately patients with ALC vs. alcoholics without ALD or healthy subjects. An association of the G allele with ALD emerged when comparing ALD patients vs. alcoholics without ALD and/or healthy subjects although moderate to large heterogeneity was observed. Our data suggested an additive genetic model for this variant in ALD.

CONCLUSION

Our meta-analysis shows that the rs738409 variant of PNPLA3 is clearly associated with alcoholic liver cirrhosis.

Roles of cytochrome P4502E1 gene polymorphisms and the risks of alcoholic liver disease: a meta-analysis

Background

Previous studies investigating the association between cytochrome P4502E1 (CYP2E1) polymorphisms and the risk of alcoholic liver diseases (ALD) have yielded conflicting results. Thus, a meta-analysis was performed to clarify the association between CYP2E1 polymorphisms and the risks of ALD.

Methods

A comprehensive literature search was conducted to identify the relevant studies. The fixed or random effect model was selected based on the heterogeneity test among studies. Publication bias was estimated using Begg’s funnel plots and Egger’s regression test.

Results

A total of 27 and 9 studies were finally included for the association between the CYP2E1 Pst I/Rsa I or Dra I polymorphisms and the risks of ALD, respectively. Overall, the combined results showed that homozygous genotype c2c2 was significantly associated with increase risk of ALD in worldwide populations (c2c2 vs. c1c1: OR = 3.12, 95%CI 1.91–5.11) when ALD patients were compared with alcoholics without ALD. Significant associations between CYP2E1 Pst I/Rsa I polymorphism and ALD risk were also observed in Asians (c2c2 vs. c1c1: OR = 4.11, 95%CI 2.32–7.29) and in Caucasians (c2c2/c1c2 vs. c1c1: OR = 1.58, 95%CI 1.04–2.42) when ALD patients were compared with alcoholics without ALD. However, subgroup analysis stratified by ALD types showed that CYP2E1 Pst I/Rsa I polymorphism was not significantly associated with the risks of alcoholic cirrhosis (ALC). No significant association was observed between CYP2E1 Dra I polymorphism and ALD risks.

Conclusion

This meta-analysis suggested that CYP2E1 Pst I/Rsa I polymorphism might be not significantly associated with advanced form of ALD (ALC), but might be significantly associated with other form of ALD such as steatosis, hepatisis, fibrosis. Furthermore, CYP2E1 Dra I polymorphism might be not significantly associated with the ALD risks. Since potential confounders could not be ruled out completely, further studies were needed to confirm these results.

CYP2E1 PstI/RsaI polymorphism and interaction with alcohol consumption in hepatocellular carcinoma susceptibility: evidence from 1,661 cases and 2,317 controls

Many studies have suggested that cytochrome P450 2E1 (CYP2E1) gene might be involved in the development of hepatocellular carcinoma (HCC). However, the results have been inconsistent. In this study, the authors performed a meta-analysis to clarify the association between Pst I/Rsa polymorphism in the CYP2E1 gene and HCC risk. PubMed and China National Knowledge Infrastructure were searched for eligible publications. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using fixed- or random-effects model. Fifteen studies (1,661 HCC cases and 2,317 controls) were identified for the data analysis. The overall result showed that there was no statistically significant association between CYP2E1 Pst I/Rsa polymorphism and HCC risk (c2/c2 vs. c1/c1, OR = 0.73, 95% CI 0.50-1.06; c1/c2 vs. c1/c1, OR = 1.00, 95% CI 0.76-1.33; c2/c2+ c1/c2 vs. c1/c1, OR = 0.99, 95% CI 0.77-1.26; c2/c2 vs. c1/c2+ c1/c1, OR = 0.73, 95% CI 0.50-1.06). Further stratified analyses indicated that the habitual alcohol drinkers with c2 alleles were more likely to develop HCC (OR = 1.73, 95% CI 1.19-2.51), compared with the non-habitual drinkers with c1 homozygote. The meta-analysis indicated that CYP2E1 Pst I/Rsa polymorphism was not associated with HCC risk, while the interaction between Pst I/Rsa polymorphism and alcohol consumption increased the risk of HCC.

Pharmacogenomics of cisplatin-based chemotherapy in ovarian cancer patients of different ethnic origins

AIM

There is a substantial difference between Asians and Caucasians in their reaction to platinum drugs. To determine whether population-related genomics contribute to differences in patient outcomes, pharmacogenomic relevance of polymorphisms in some genes, the protein activities of which may affect aspects of cisplatin metabolism, were evaluated.

PATIENTS & METHODS

Nineteen polymorphisms in ten genes were tested for correlations with the efficacy and toxicity of a cisplatin-cyclophosphamide regimen in Yakut and Russian patients with ovarian cancer.

RESULTS

The CYP2E1 7632T>A polymorphism was associated with progression-free survival (p = 0.015) in Yakuts. In Russians, progression-free survival was correlated with the GSTP1 Ile105Val polymorphism (p = 0.004). Yakut patients with the GSTT1-null genotype had a higher risk for nephrotoxicity. By contrast, in the Russian group, nephrotoxicity was more frequent among patients with heterozygous ERCC1 genotypes. Severe emesis in Yakuts was independently associated with two polymorphisms in the CYP2E1 gene but in Russians, it was more common in patients with the GSTT1-null genotype. Differences in genotypic correlations with anemia were also observed.

CONCLUSION

Significant differences in genotype distribution between Russian and Yakut women were observed for ten of the 19 polymorphisms, but none of them seemed to be a clear casual candidate and further studies involving more markers are required.

Meta-analysis: glutathione-S-transferase allelic variants are associated with alcoholic liver disease

BACKGROUND

Only a minority of alcoholics develop alcoholic liver disease (ALD) and allelic variants within genes encoding glutathione-S-transferases (GST) have been associated with ALD vulnerability with controversial results.

AIM

To assess the effects of GST polymorphisms on ALD by means of a genetic association study and meta-analysis.

METHODS

We retrieved published studies on the relationship between allelic variants within GST genes and ALD by means of electronic database search. A meta-analysis was conducted in a fixed or random effects model. Calculations of odds ratios (OR) and their confidence intervals (CI), tests for heterogeneity of the results and sensitivity analysis, have been performed. A genetic association study comparing GSTM1, GSTT1 and GSTP1 genotype distribution among 279 alcoholics with or without ALD and 144 controls was also performed. Results  Fifteen previous studies were identified analysing the association of ALD with polymorphisms within GST genes. After meta-analysis, we found a significant association between the possession of the GSTM1 null allele and the presence of ALD (OR=1.43; 95% CI: 1.14, 1.78; P=0.002) among alcoholic patients. A significant association was also found for the possession of the GSTP1 Val/Val genotype and the presence of ALD (OR=2.04; 95% CI: 1.09, 3.80; P=0.03).

CONCLUSIONS

Our results suggest that, among alcoholics, carriers of GSTM1 null genetic variant or Val/Val genotype of Ile/Val GSTP1 polymorphism have an increased risk to suffer from alcoholic liver disease. The role of glutathione-S-transferase as a potential therapeutic target in alcoholic liver disease is reinforced.

Warfarin and acetaminophen interaction: a summary of the evidence and biologic plausibility

Ms TS is a 66-year-old woman who receives warfarin for prevention of systemic embolization in the setting of hypertension, diabetes, and atrial fibrillation. She had a transient ischemic attack about 4 years ago when she was receiving aspirin. Her INR control was excellent; however, over the past few months it has become erratic, and her average dose required to maintain an INR of 2.0 to 3.0 appears to have decreased. She has had back pain over this same period and has been taking acetaminophen at doses at large as 650 mg four times daily, with her dose varying based on her symptoms. You recall a potential interaction and wonder if (1) her acetaminophen use is contributing to her loss of INR control, and (2) does this interaction place her at increased risk of warfarin-related complications?

Genetic polymorphisms of genes coding to alcohol-metabolizing enzymes in western Mexicans: association of CYP2E1*c2/CYP2E1*5B allele with cirrhosis and liver function

BACKGROUND

Alcoholic cirrhosis constitutes a major public health problem in the world where ADH1B, ALDH2, and CYP2E1 polymorphisms could be playing an important role. We determined ADH1B*2, ALDH2*2, and CYP2E1*c2 allele frequencies in healthy control individuals (C) and patients with alcoholic cirrhosis (AC) from western Mexico.

METHODS

Ninety C and 41 patients with AC were studied. Genotype and allele frequency were determined through polymerase chain reaction-restriction fragment length polymorphisms.

RESULTS

Polymorphic allele distribution in AC was 1.6%ADH1B*2, 0.0%ALDH2*2, and 19.5%CYP2E1*c2; in C: 6.1%ADH1B*2, 0%ALDH2*2, and 10.6%CYP2E1*c2. CYP2E1*c2 polymorphic allele and c1/c2 genotype frequency were significantly higher (p < 0.05 and p < 0.01, respectively) in patients with AC when compared to C. Patients with AC, carrying the CYP2E1*c2 allele, exhibited more decompensated liver functioning evaluated by total bilirubin and prothrombin time, than c1 allele carrying patients (p < 0.05). Cirrhosis severity, assessed by Child's Pugh score and mortality, was higher in patients carrying the c2 allele, although not statistically significant.

CONCLUSIONS

In this study, CYP2E1*c2 allele was associated with susceptibility to AC; meanwhile, ADH1B*2 and ALDH2*2 alleles were not. CYP2E1*c2 allele was associated with AC severity, which could probably be attributed to the oxidative stress promoted by this polymorphic form. Further studies to clearly establish CYP2E1*c2 clinical relevance in the development of alcohol-induced liver damage and its usefulness as a probable prognostic marker, should be performed. Also, increasing the number of patients and including a control group conformed by alcoholic patients free of liver damage may render more conclusive results. These findings contribute to the understanding of the influence of gene variations in AC development among populations, alcohol metabolism, and pharmacogenetics.

The impact of genetic variability on liver disease in the Hispanic/Latin-American population

Liver cirrhosis is within the top 10 causes of death in Latin-American countries and recent evidence suggests that Hispanics in the USA have a more aggressive course of many types of liver disease and show lower response to treatment of hepatitis C compared with other ethnic groups. Although environmental factors are very important, they do not appear to fully account for the observed ethnic differences in the incidence of cirrhosis and progression rates. Genome-wide association studies have been a powerful tool to identify genetic variants that directly confer susceptibility to liver disease. Here, we review the current knowledge on genetic variants associated with the most common types of liver disease that may contribute to ancestry-related differences in disease progression and mortality.

The impact of CYP2E1 genetic variability on risk assessment of VOC mixtures

Humans are simultaneously exposed to multiple chemicals in the environment. Many of the chemicals use the same enzymes in their metabolic pathways. Competitive inhibition may occur as one of the possible interactions between the xenobiotics in human body. For example, many volatile organic compounds (VOCs) are metabolized using P450 enzymes, specifically CYP2E1. Inheritable gene alterations may result in changes of function of the enzymes in different human subpopulations. Variations in quantity and/or quality of particular isoenzymes may cause differences in the metabolism of VOCs. These variations may cause higher sensitivity in certain populations. Using examples of three different mixtures, this review paper outlines the variances in CYP2E1 isoenzymes, effect of exposure to such mixtures on sensitive populations, and approaches to mixtures risk assessment.

Genetic polymorphisms of drug-metabolizing phase I enzymes CYP2E1, CYP2A6 and CYP3A5 in South Indian population

CYP2E1, CYP2A6 and CYP3A5 enzymes belong to phase I group of drug-metabolizing enzymes, which are involved in the metabolism of various compounds and xenobiotics. Presence of polymorphisms in the genes coding for these enzymes results in interindividual variations in drug metabolism, therapeutic response and susceptibility towards various diseases. The frequencies of these variants in genes differ considerably between ethnic groups. This study was carried out to estimate the allele and genotype frequencies of common variants in CYP2E1, CYP2A6 and CYP3A5 in South Indian population. Six hundred and fifty-two unrelated healthy volunteers of South Indian origin (Andhra Pradesh, Karnataka, Kerala and Tamil Nadu) were included in this study. Polymerase chain reaction-restriction fragment length polymorphism, allele-specific PCR, real-time PCR, SNaPshot and gene sequencing methods were used for the identification of gene polymorphisms. The frequencies of CYP2E1*1B, CYP2E1*5B and CYP2E1*6 alleles in South Indian population were 14.3, 1.3 and 22.4%, respectively. The frequencies of CYP2A6*2, CYP2A6*4A and CYP2A6*5 alleles were found to be 1, 8.9 and 0.7%, respectively. The distribution of CYP3A5*3 allele was 63.5%. There were no variant alleles of CYP3A5*2, CYP3A5*4 and CYP3A5*6 in South Indian population. The frequencies of CYP2E1, CYP2A6 and CYP3A5 in the South Indian population are distinct from Caucasians, Chinese, Japanese, African Americans and other compared populations. This is the first study conducted in the South Indian population with a larger sample size. The findings of our study provide the basic genetic information for further pharmacogenomic investigations in the population.

The investigation into CYP2E1 in relation to the level of response to alcohol through a combination of linkage and association analysis

BACKGROUND

A low level of response to alcohol during an individual's early experience with alcohol is associated with an increase risk of alcoholism. A family-based genome-wide linkage analysis using sibling pairs that underwent an alcohol challenge where the level of response to alcohol was measured with the Subjective High Assessment Scale (SHAS) implicated the 10q terminal (10qter) region. CYP2E1, a gene known for its involvement with ethanol metabolism, maps to this region.

METHODS

Variance component multipoint linkage analysis was performed on a combined map of single-nucleotide polymorphism (SNP) and microsatellite data. To account for the heterogeneity evident in the dataset, a calculation assuming locus heterogeneity was made using the Heterogeneity Log of Odds (HLOD) score. Association between SNP marker allele counts and copy number and SHAS scores were evaluated using a logistic regression model.

RESULTS

Linkage analysis detected significant linkage to CYP2E1, which was diminished because of apparent locus heterogeneity traced to a single family with extreme phenotypes. In retrospect, circumstances recorded during testing for this family suggest that their phenotype data are likely to be unreliable. Significant allelic associations were detected for several CYP2E1 polymorphisms and the SHAS score. DNA sequencing from families that contributed the greatest evidence for linkage did not detect any changes directly affecting the primary amino acid sequence. With the removal of a single family, combined evidence from microsatellites and SNPs offers significant linkage between the level of response to alcohol and the region on the end of chromosome 10.

CONCLUSION

Combined linkage and association indicate that sequence changes in or near CYP2E1 affect the level of response to alcohol providing a predictor of risk of alcoholism. The absence of coding sequence changes indicates that regulatory sequences are responsible. Implicating CYP2E1 in the level of response to alcohol allows inferences to be made about how the brain perceives alcohol.

Risk of HCC: genetic heterogeneity and complex genetics

Hepatocellular carcinoma (HCC) is a common form of cancer that arises from hepatocytes and whose risk may be affected by several known environmental factors, including hepatitis viruses, alcohol, cigarette smoking, and others. Rare monogenic syndromes, such as alpha1-antitrypsin deficiency, glycogen storage disease type I, hemochromatosis, acute intermittent and cutanea tarda porphyria, as well as hereditary tyrosinemia type I are associated with a high risk of HCC. Several common conditions or diseases inherited as polygenic traits e.g. autoimmune hepatitis, type 2 diabetes, a family history of HCC, hypothyroidism, and non-alcoholic steatohepatitis also show an increased risk of HCC compared to the general population. Overall, the genetic susceptibility to HCC is characterized by a genetic heterogeneity; a high individual risk of HCC may thus be caused by several unlinked single gene defects, whose carriers are rare in the general population, or by more common conditions inherited by complex genetics.

Tumor necrosis factor polymorphisms and alcoholic liver disease: a HuGE review and meta-analysis

The association between alcoholic liver disease (ALD) and tumor necrosis factor-alpha gene (TNFA) polymorphisms has been analyzed in several studies, but results have been conflicting. The main purpose of this study was to integrate previous findings and explore whether these polymorphisms are associated with susceptibility to ALD. The authors surveyed studies on the relation between TNFA gene polymorphisms and ALD by means of an electronic database search. A meta-analysis was conducted in a random-effects model. The association between ALD and the -238G>A or -308G>A polymorphism of the TNFA gene has been analyzed in 11 studies. Concerning the -238G>A polymorphism, the authors found a significant association between possession of the A allele and risk of alcoholic liver cirrhosis (odds ratio = 1.47, 95% confidence interval: 1.05, 2.07). Meta-analysis of the relation between the -308G>A polymorphism and ALD did not show any significant association. Given the limited number of studies and the potential biases, more data are needed to confirm the association described for the -238A allele.

Genetic polymorphisms and the efficacy and toxicity of cisplatin-based chemotherapy in ovarian cancer patients

Platinum drugs are among the most active and widely used agents in the treatment of different cancers. However, the great individual variability in both outcome and toxicity of platinum chemotherapy requires the identification of genetic markers that can be used to screen patients before treatment. In this study, 21 polymorphisms in 10 genes, the protein activities of which may be addressed in different aspects of cisplatin metabolism, were tested for correlations with efficacy and toxicity of cisplatin-cyclophosphamide regimen in 104 ovarian cancer patients. The glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism was strongly associated with progression-free survival (chi(2)=12.12, P=0.002). The allelic status of the GSTA1 -69 C>T polymorphism correlated with the overall survival: patients with T/T genotype survived longer than C/C carriers (P=0.044). Thrombocytopenia, anemia and neuropathy were less frequent among patients with the GSTM1-null or GSTM3 intron 6 AGG/AGG genotypes. Severe neutropenia was associated with the TP53 72 Pro/Pro, XPD 312 Asp/Asn and XRCC1 399 Arg/Arg genotypes. A higher risk of nephrotoxicity was noted for patients with the heterozygous ERCC1 19007 T/C and 8092 C/A genotypes. No correlations were found between genotypes and complete tumor responses.

A novel polymorphism rs1329149 of CYP2E1 and a known polymorphism rs671 of ALDH2 of alcohol metabolizing enzymes are associated with colorectal cancer in a southwestern Chinese population

BACKGROUND

To screen for tagging single nucleotide polymorphisms (tagSNP) in the major alcohol metabolizing enzymes: ADH1B, ALDH2, and CYP2E1, and to evaluate the association between these tagSNPs and colorectal cancer (CRC) in a southwestern Chinese population.

METHODS

A hospital-based case-control study of 440 CRC patients and 800 cancer-free controls was conducted. Personal information was collected by a Semi-Quantitative Food Frequency Questionnaire. The tagSNPs were screened in the HapMap with Haploview by setting the minor allele frequency at 0.03 with the highest score of r(2) form each block. Genotypes were identified by using the SNPLex System. Both crude and adjusted odds ratio (OR) and 95% confidence interval (CI) were used to evaluate the risk of each SNP.

RESULTS

Sixteen tagSNPs were selected, and 13 were successfully genotyped. A novel CYP2E1 locus rs1329149 and a known ALDH2 locus rs671 were found to be significantly associated with CRC risk. The adjusted OR was 1.86 (95% CI, 1.12-3.09) for the rs671 A/A genotype and 4.04 for the rs1329149 T/T genotype (95% CI, 2.44-6.70), compared with their common homozygous genotypes. Interaction was found between alcohol consumption and gene polymorphisms on CRC, the adjusted OR was 7.17 (95% CI, 2.01-25.53) for drinking habits combined with rs671 A/A or rs1329149 T/T genotype.

CONCLUSION

The results of this study suggest that rs671 A/A and the first reported locus rs1329149 T/T genotypes increase the susceptibility to CRC, and gene-environmental interaction between the two loci and alcohol use existed for CRC in Southwestern Chinese. Larger studies are warranted to verify our findings.

Genetic variation of genes for xenobiotic-metabolizing enzymes and risk of bronchial asthma: the importance of gene-gene and gene-environment interactions for disease susceptibility

The aim of our pilot study was to evaluate the contribution of genes for xenobiotic-metabolizing enzymes (XMEs) for the development of bronchial asthma. We have genotyped 25 polymorphic variants of 18 key XME genes in 429 Russians, including 215 asthmatics and 214 healthy controls by a polymerase chain reaction, followed by restriction fragment length polymorphism analyses. We found for the first time significant associations of CYP1B1 V432L (P=0.045), PON1 Q192R (P=0.039) and UGT1A6 T181A (P=0.025) gene polymorphisms with asthma susceptibility. Significant P-values were evaluated through Monte-Carlo simulations. The multifactor-dimensionality reduction method has obtained the best three-locus model for gene-gene interactions between three loci, EPHX1 Y113H, CYP1B1 V432L and CYP2D6 G1934A, in asthma at a maximum cross-validation consistency of 100% (P=0.05) and a minimum prediction error of 37.8%. We revealed statistically significant gene-environment interactions (XME genotypes-smoking interactions) responsible for asthma susceptibility for seven XME genes. A specific pattern of gametic correlations between alleles of XME genes was found in asthmatics in comparison with healthy individuals. The study results point to the potential relevance of toxicogenomic mechanisms of bronchial asthma in the modern world, and may thereby provide a novel direction in the genetic research of the respiratory disease in the future.

Cytochrome P450 2E1 and head and neck cancer: interaction with genetic and environmental risk factors

The present case-control study investigates the association of polymorphisms in cytochrome P450 2E1 (CYP2E1), involved in the metabolism of tobacco carcinogens and alcohol, with Head and Neck Squamous Cell Carcinoma (HNSCC). In addition, the interaction of CYP2E1 (CYP2E1*5B and CYP2E1*6) with other genetic factors (null genotype of glutathione-S-Transferase M1, GSTM1, X-Ray Repair Cross Complementing Group I, XRCC1 (Arg194Trp), and environmental risk factors such as alcohol and tobacco in modifying HNSCC risk were investigated. Genotypes were determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a total of 350 male cases of HNSCC and an equal number of healthy male controls. Statistical analysis showed a significant increase in HNSCC risk in cases with variant genotypes of CYP2E1*5B (RsaI) (O.R. 3.44; 95% C.I. 1.45-8.14) and CYP2E1*6 (DraI) (O.R. 1.76; 95% C.I. 1.28-2.41). Haplotype analysis revealed that haplotype T-A was associated with a greater than 10-fold increase in risk for HNSCC. Our data also revealed a several fold increase in HNSCC risk in cases carrying a combination of variant genotypes of CYP2E1 with the null genotype of GSTM1 or XRCC1 variant genotypes. Alcohol or tobacco use (both smoking and chewing) were also found to interact with variant genotypes of CYP2E1 in significantly enhancing HNSCC risk. This increase in risk associated with an interaction of CYP2E1 genotypes with GSTM1 or XRCC1 or with tobacco and alcohol use demonstrates the importance of gene-gene and gene-environment interactions in the development of HNSCC.

CYP1A2*1C, CYP2E1*5B, and GSTM1 polymorphisms are predictors of risk and poor outcome in head and neck squamous cell carcinoma patients

Head and neck squamous cell carcinoma (HNSCC) is associated with environmental factors, especially tobacco and alcohol consumption. Most of the carcinogens present in tobacco smoke are converted into DNA-reactive metabolites by cytochrome P450 (CYPs) enzymes and detoxification of these substances is performed by glutathione S-transferases (GSTs). It has been suggested that genetic alterations, such as polymorphisms, play an important role in tumorigenesis and HNSCC progression. The aim of this study was to investigate CYP1A1, CYP1A2, CYP2E1, GSTM1, and GSTT1 polymorphisms as risk factors in HNSCC and their association with clinicopathologic data. The patients comprised 153 individuals with HNSCC (cases) and 145 with no current or previous diagnosis of cancer (controls). Genotyping of the single nucleotide polymorphisms (SNPs) of the CYP1A1, CYP1A2, and CYP2E1 genes was performed by PCR-RFLP and the GSTM1 and GSTT1 copy number polymorphisms (CNPs) were analyzed by PCR-multiplex. As expected, a significant difference was detected for tobacco and alcohol consumption between cases and controls (P<0.001). It was observed that the CYP1A2*1D (OR=16.24) variant and GSTM1 null alleles (OR=0.02) confer increased risk of HNSCC development (P<0.001). In addition, head and neck cancer alcohol consumers were more frequently associated with the CYP2E1*5B variant allele than control alcohol users (P<0.0001, OR=190.6). The CYP1A2*1C polymorphism was associated with tumor recurrence (log-rank test, P=0.0161). The CYP2E1*5B and GSTM1 null alleles were significantly associated with advanced clinical stages (T3+T4; P=0.022 and P=0.028, respectively). Overall, the findings suggested that the genetic polymorphisms studied are predictors of risk and are also associated with tumor recurrence, since they are important for determining the parameters associated with tumor progression and poor outcomes in HNSCC.

Polymorphism in cytochrome P450 2E1 and interaction with other genetic risk factors and susceptibility to alcoholic liver cirrhosis

The association of polymorphism in cytochrome P450 2E1 (CYP2E1), the major microsomal ethanol metabolizing enzyme and its interaction with genes, involved in detoxification of reactive oxygen species, such as glutathione-S-transferases M1 (GSTM1) and alcohol intake, gamma-aminobutyric acid receptor gamma2 (GABRG2) was studied with the risk to alcoholic cirrhosis in a case-control study. A total of 160 alcoholic cirrhotic and 125 non-alcoholic cirrhotic cases, visiting the OPD facility of Gastroenterology Department of Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGI), Lucknow, India and 250 non-alcoholic and 100 alcoholic controls having no evidence of liver disease were included in the study. PCR-based RFLP methodology was followed for genotyping studies. Our data revealed that the variant genotypes of CYP2E1 5B exhibited significant association with the alcoholic liver cirrhosis when compared to non-alcoholic controls (OR: 4.3; 95%CI: 1.5-12.4; p: 0.003) or non-alcoholic cirrhosis patients (OR: 5.4; 95%CI: 1.2-24.5; p: 0.01) or alcoholic controls (OR: 4.3; 95%CI: 0.95-19.62; p: 0.04). Haplotype approach revealed that haplotype T-A-T was found to be associated with more than 5-fold increase in risk for alcoholic cirrhosis. Likewise, combination of variant genotype of CYP2E1 5B with null genotype of GSTM1, a phase II detoxification enzyme, resulted in several fold increase in risk in alcoholic cirrhotic patients when compared with non-alcoholic controls or non-alcoholic cirrhotic patients. Further, the combination of variant genotype of CYP2E1 5B with GABRG2, significantly increased the risk upto 6.5-fold in alcoholic cirrhotic patients when compared with non-alcoholic controls thereby suggesting the role of gene-gene interaction in alcoholic cirrhosis.

Polymorphism in glutathione-S-transferases: a risk factor in alcoholic liver cirrhosis

In a case-control study, association of polymorphism in glutathione-S-transferases (GSTM1, GSTT1, GSTP1), involved in detoxification of reactive oxygen species (ROS), was studied with alcoholic liver cirrhosis. The study included 175 alcoholic cirrhotic patients (ACPs), 140 non-alcoholic cirrhotic patients (NACPs), visiting Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGI), Lucknow, India, 255 non-alcoholic controls and 140 alcoholic controls. The data showed an increase in risk to alcoholic cirrhosis in ACPs with GSTM1 (null) genotype when compared with non-alcoholic controls (OR: 1.7; 95% CI: 1.15-2.56) or alcoholic controls (OR: 1.7; 95% CI: 1.07-2.73). Significant increase in risk was also observed in ACPs with variant genotype of GSTP1 when compared with non-alcoholic controls (OR: 1.65; 95% CI: 1.12-2.43). A much higher risk to alcoholic liver cirrhosis was observed in patients carrying combination of null genotypes of GSTM1 and GSTT1 (OR: 2.8; 95% CI: 1.3-6.06) or variant genotype of GSTP1 and null genotype of GSTM1 (OR: 2.8; 95% CI: 1.58-4.90) or GSTT1 (OR: 2.16; 95% CI: 1.08-4.28). Likewise, greater risk for alcoholic cirrhosis was observed in patients carrying combination of GSTM1, GSTT1 (null) and variant genotype of GSTP1 (OR: 5.8; 95% CI: 2.17-15.80). Our data further showed that interaction of GSTs with variant genotype of manganese superoxide dismutase (MnSOD), which detoxifies free radicals, or cytochrome P450 2E1, which generates free radicals, resulted in several fold increase in risk to alcoholic liver cirrhosis in ACPs when compared with non-alcoholic controls thus demonstrating the role of gene-gene interactions in modulating the risk to alcoholic liver cirrhosis.

Cytochrome P450 2E1 gene polymorphisms/haplotypes and Parkinson's disease in a Swedish population

Cytochrome P450 2E1 (CYP2E1), which inter alia is located in dopamine containing neurons in the substantia nigra, has been hypothesized to be of importance for the pathophysiology of Parkinson's disease (PD), either by its production of reactive oxygen species (ROS) or by its capability to detoxify putative neurotoxins. Numerous polymorphisms in the coding and non-coding regions of the gene for this enzyme have been reported. Different variants may account for inter-individual differences in the activity of the enzyme or production of ROS. In this study, the CYP2E1 gene was examined in a control population (n = 272) and a population with PD (n = 347), using a tag-single nucleotide polymorphism (tSNP) approach founded on HapMap Data. Six tSNPs were used in the analysis and haplotype block data were obtained. In case of significance, the SNP was further examined regarding early/late age of disease onset and presence of relatives with PD. We found an association between allele and genotype frequencies of the C/G polymorphism at intron 7 (rs2070676) of this gene and PD (P value of 0.026 and 0.027, respectively). Furthermore, analysis of the rs2070676 polymorphism in subgroups of patients with age of disease onset higher than 50 years and those not having a relative with PD also demonstrated a significant difference with controls. This was seen in both genotype (corresponding to P value = 0.039 and 0.032) and allele (P = 0.027 and 0.017 respectively) frequency. As a representative of many polymorphisms or in possible linkage disequilibrium with other functional variants, it is possible that rs2070676 could influence the regulation of the enzyme. In conclusion, our results display an association between the rs2070676 polymorphism and PD. Additional investigations are needed to elucidate the importance of this polymorphism for the activity of CYP2E1 and PD susceptibility.

Global patterns of variation in allele and haplotype frequencies and linkage disequilibrium across the CYP2E1 gene

Cytochrome P450 2E1, gene symbol CYP2E1, is one of a family of enzymes with a central role in activating and detoxifying xenobiotics and endogenous compounds. Genetic variation at this gene has been reported in different human populations, and some association studies have reported increased risk for cancers and other diseases. To the best of our knowledge, multi-single-nucleotide polymorphism haplotypes and linkage disequilibrium (LD) have not been systematically studied for CYP2E1 in multiple populations. Haplotypes can greatly increase the power both to identify patterns of genetic variation relevant for gene expression as well as to detect disease-related susceptibility mutations. We present frequency and LD data and analyses for 11 polymorphisms and their haplotypes that we have studied on over 2600 individuals from 50 human population samples representing the major geographical regions of the world. The diverse patterns of haplotype variation found in the different populations we have studied show that ethnicity may be an important variable helping to explain inconsistencies that have been reported by association studies. More studies clearly are needed of the variants we have studied, especially those in the 5' region, such as the variable number of tandem repeats, as well as studies of additional polymorphisms known for this gene to establish evidence relating any systematic differences in gene expression that exist to the haplotypes at this gene.

A haplotype analysis of CYP2E1 polymorphisms in relation to alcoholic phenotypes in Mexican Americans

BACKGROUND

Studies regarding the association between the 4 polymorphisms of CYP2E1 (CYP2E1*1D, *5B, *6, and *1B) and alcoholism are inconsistent and inconclusive. The purpose of the present study was to clarify previously discordant studies by haplotype analysis in the Mexican American population.

METHODS

The 4 polymorphisms of CYP2E1 were studied in 334 alcoholics and 365 controls. Genotype, allele, and haplotype frequency comparisons between alcoholics and controls were assessed. Patterns of linkage disequilibrium (LD) at CYP2E1 were determined. Reconstructed haplotypes were tested for associations with clinical phenotypes (age onset of drinking, Maxdrinks, and smoking status).

RESULTS

No significant associations between the 4 polymorphisms of CYP2E1 and alcoholism were revealed by single allele tests. High LD was found between the CYP2E1 c2 and C alleles in Mexican Americans. Eleven haplotypes were present in the 699 participants. The 6 main haplotypes with frequencies higher than 1% made up 97% of the total halpotypes. The frequency of subjects carrying H6 (1C-c2-C-A2) was significantly higher in alcoholics than in controls (p = 0.0001). In contrast, the frequencies of H7 (1C-c2-C-A1) and H10 (1C-c2-D-A1) were significantly lower in alcoholics than in controls (p = 0.0072 for H7 and p = 0.0407 for H10). The frequency of H6 was significantly higher in alcoholics who had late onset of drinking than in nonalcoholic controls. Furthermore, the frequencies of H6 haplotype were also consistently higher in groups who had high number of maximum drinks (9 to 32 drinks) than in controls. When smokers are excluded, the frequencies of H6, H7, and H9 (1C-c2-D-A2) showed statistically significant differences between alcoholics and controls (p < 0.05). Moreover, the association between H6 and alcoholism become more robust when smokers are excluded. Furthermore, the frequency of H1 (1C-c1-D-A2) in alcoholic-smokers was much higher than in alcoholic-nonsmokers (p = 0.0028). In contrast, alcoholic-smokers carried less H2 (1C-c1-D-A1) in comparison with alcoholic-nonsmokers (p = 0.0417). The H3 (1D-c2-C-A2) frequency in alcoholic-smokers was much lower than in alcoholic-nonsmokers (p = 0.0042) and control-smokers (p = 0.0363).

CONCLUSIONS

Our data demonstrate that carrying haplotype H6 might enhance susceptibility to developing alcoholism, but possessing the H7 or H10 haplotype appears to decrease this susceptibility. The H6, H7, and H9 haplotypes may play certain roles in different clinical phenotypes in Mexican American alcoholics. In addition, our data suggest that the H1, H2, and H3 haplotypes are associated with alcohol drinking and smoking. These results support that haplotype analysis is much more informative than single allele analysis. Our findings clearly indicate the importance of H6 haplotype in alcohol drinking in Mexican Americans.

Molecular mechanisms of alcohol-mediated carcinogenesis

Approximately 3.6% of cancers worldwide derive from chronic alcohol drinking, including those of the upper aerodigestive tract, the liver, the colorectum and the breast. Although the mechanisms for alcohol-associated carcinogenesis are not completely understood, most recent research has focused on acetaldehyde, the first and most toxic ethanol metabolite, as a cancer-causing agent. Ethanol may also stimulate carcinogenesis by inhibiting DNA methylation and by interacting with retinoid metabolism. Alcohol-related carcinogenesis may interact with other factors such as smoking, diet and comorbidities, and depends on genetic susceptibility.

Association of CYP2E1 and NAT2 gene polymorphisms with chronic obstructive pulmonary disease

BACKGROUND

Detoxification genes are potential candidates in the susceptibility of patients with chronic obstructive pulmonary disease. Polymorphisms in these genes alter the metabolism of xenobiotics such as present in cigarette smoke.

METHODS

We conducted a case-control study to investigate total 9 polymorphisms of CYP2E1, CYP2D6 and NAT2 genes by PCR-RFLP.

RESULTS

The -1053C/T and -1293G/C promoter polymorphisms of CYP2E1 were found to be in complete linkage disequilibrium (LD) (D'=1.00, r(2)=1.0, p<0.0001), whereas -1293G/C and 7632T/A polymorphisms of the same gene were also in significant LD (D'=0.5183, r(2)=1.0, p=0.01) in patients. The patients over-represented the -1293GC+CC genotypes of -1293G/C polymorphism of CYP2E1 (p=0.03) and NAT2*4/7, NAT2()5/6, NAT2*5/7, NAT2*6/6 and NAT2*6/7 genotypes of NAT2 (p=0.01, p=0.039, p=0.01, p=0.032, p=0.006, respectively), resulting in to higher frequency of -1293C (OR=7.02, 95% CI=1.63-30.15, p=0.002), NAT2*6 (OR=1.90, 95% CI=1.27-2.83, p=0.001) and NAT2*7 (OR=2.91, 95% CI=1.65-5.12, p=0.0001) alleles. The 7632T/A and 9893C/G polymorphisms of CYP2E1 and 1934G/A polymorphism of CYP2D6 did not associate with the disease (p>0.05). The haplotypes -1293G:9893C and -1293G:7632T:9893C were under-represented (p<0.001), whereas haplotypes -1293C:7632T, -1293C:9893C, -1293C:9893G and -1293C:7632T:9893C of the 4 CYP2E1 polymorphisms were over-represented in patients (p<0.05).

CONCLUSION

The CYP2E1 and NAT2 variants associated with COPD.

Polymorphisms of alcohol-metabolizing enzymes and the risk for alcoholism and alcoholic liver disease in Caucasian Spanish women

BACKGROUND

The relationship of polymorphisms of the genes that encode for alcohol-metabolizing enzymes and individual vulnerability to alcoholism and alcoholic liver disease (ALD) in women is unclear. We determined the genotypes of ADH1B, ADH1C, CYP2E1 (Dra-I and Pst-I) and ALDH2 in a group of Caucasian Spanish women.

METHODS

We performed a cross-sectional case-control study. The study group was made of 220 women. Of these, 85 were alcoholic (27 without liver disease and 58 with alcoholic liver disease) and 135 were non-alcoholic (42 healthy controls and 93 with liver disease unrelated to alcohol). Genotyping of alcohol-metabolizing enzymes was performed using PCR-RFLP methods.

RESULTS

The distribution of the allelic variants (alleles 1 and 2) in the whole subjects analyzed was: ADH1B 91.6% and 8.4%; ADH1C 58.4% and 41.6%; CYP2E1 Dra-I 15% and 85%; CYP2E1 Pst-I 96.8% and 3.2%; and ALDH2 100% and 0%, respectively. Carriage of genotypes containing the ADH1B*2 mutant allele significantly protected against alcoholism [odds-ratio (OR)=0.00; 95% confidence interval (95% CI): 0.00-0.94; p=0.02] but was associated with an increased risk for alcoholic liver disease among alcohol-dependent women [OR=0.43; 95% CI: 0.18-0.41; p=0.004]. Analysis of the remaining loci showed no significant associations.

CONCLUSIONS

In Caucasian Spanish women the ADH1B*2 allele modulates the risk for alcohol dependence and for alcoholic liver disease. Given the small number of alcoholic women analyzed here, these data need further validation in larger cohorts.

Association of alcohol-metabolizing genes with alcoholism in a Mexican Indian (Otomi) population

Association studies provide a powerful approach to link DNA variants and genetic predisposition to complex diseases. In this study, we determined the genotype and allelic frequencies of genes encoding enzymes involved in alcohol metabolism in alcoholic and nonalcoholic subjects of related ethnicity. A total of 118 individuals of Otomi Mexican Indian ancestry were included. Fifty-nine were chronic alcoholics according to WHO criteria and alcohol dependents according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM IV) criteria. They were compared to 59 teetotalers or alcohol consumers of <10 g per day. The restriction fragment length polymorphisms analyzed were ADH1B/MaeIII, ALDH2/MboII, CYP2E1/DraI, CYP2E1/RsaI, and CYP2E1/TaqI. Of the studied polymorphisms, a significant difference between alcoholic and nonalcoholic Otomies was observed only in the CYP2E1/TaqI. The common genotype in alcoholics was A1/A2 (54%), and in nonalcoholics the homozygous A2/A2 (63%) (odds ratio [OR]: 0.28; 95% confidence interval [CI]: 0.13-0.60; P=.002). The frequency of the mutant allele A1 was significantly higher in alcoholics than in nonalcoholics (41 vs. 21%; OR: 2.4; 95% CI: 1.3-4.3; P=.003). This documents the presence of a polymorphism of CYP2E1 that is overexpressed in alcoholic Otomies, in which the variant allele (A1 of CYP2E1/TaqI) is associated with increased susceptibility to alcoholism. The appreciation that this finding may be an additional factor contributing to the high frequency of liver cirrhosis in Otomies requires further investigation.

CYP2E1 genotype and isoniazid-induced hepatotoxicity in patients treated for latent tuberculosis

OBJECTIVE

To determine whether pharmacogenetic tests such as N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) genotyping are useful in identifying patients prone to antituberculosis drug-induced hepatotoxicity in a cosmopolite population.

METHODS

In a prospective study we genotyped 89 patients treated with isoniazid (INH) for latent tuberculosis. INH-induced hepatitis (INH-H) or elevated liver enzymes including hepatitis (INH-ELE) was diagnosed based on the clinical diagnostic scale (CDS) designed for routine clinical practice. NAT2 genotypes were assessed by fluorescence resonance energy transfer probe after PCR analysis, and CYP2E1 genotypes were determined by PCR with restriction fragment length polymorphism analysis.

RESULTS

Twenty-six patients (29%) had INH-ELE, while eight (9%) presented with INH-H leading to INH treatment interruption. We report no significant influence of NAT2 polymorphism, but we did find a significant association between the CYP2E1 *1A/*1A genotype and INH-ELE (OR: 3.4; 95% CI:1.1-12; p = 0.02) and a non significant trend for INH-H (OR: 5.9; 95% CI: 0.69-270; p = 0.13) compared with other CYP2E1 genotypes. This test for predicting INH-ELE had a positive predictive value (PPV) of 39% (95% CI: 26-54%) and a negative predictive value (NPV) of 84% (95% CI: 69-94%).

CONCLUSION

The genotyping of CYP2E1 polymorphisms may be a useful predictive tool in the common setting of a highly heterogeneous population for predicting isoniazid-induced hepatic toxicity. Larger prospective randomized trials are needed to confirm these results.

Alcohol and cancer

A causal association has been established between alcohol consumption and cancers of the oral cavity, pharynx, larynx, oesophagus, liver, colon, rectum, and, in women, breast; an association is suspected for cancers of the pancreas and lung. Evidence suggests that the effect of alcohol is modulated by polymorphisms in genes encoding enzymes for ethanol metabolism (eg, alcohol dehydrogenases, aldehyde dehydrogenases, and cytochrome P450 2E1), folate metabolism, and DNA repair. The mechanisms by which alcohol consumption exerts its carcinogenic effect have not been defined fully, although plausible events include: a genotoxic effect of acetaldehyde, the main metabolite of ethanol; increased oestrogen concentration, which is important for breast carcinogenesis; a role as solvent for tobacco carcinogens; production of reactive oxygen species and nitrogen species; and changes in folate metabolism. Alcohol consumption is increasing in many countries and is an important cause of cancer worldwide.

The role of genetic polymorphisms in alcoholic liver disease

Chronic alcohol consumption is a major cause of liver cirrhosis which, however, develops in only a minority of heavy drinkers. Evidence from twin studies indicates that genetic factors account for at least 50% of individual susceptibility. The contribution of genetic factors to the development of diseases may be investigated either by means of animal experiments, through linkage studies in families of affected patients, or population based case-control studies. With regard to the latter, single nucleotide polymorphisms of genes involved in the degradation of alcohol, antioxidant defense, necroinflammation, and formation and degradation of extracellular matrix are attractive candidates for studying genotype-phenotype associations. However, many associations in early studies were found to be spurious and could not be confirmed in stringently designed investigations. Therefore, future genotype-phenotype studies in alcoholic liver disease should meet certain requirements in order to avoid pure chance observations due to a lack of power, false functional interpretation, and insufficient statistical evaluation.

Do alcohol-metabolizing enzyme gene polymorphisms increase the risk of alcoholism and alcoholic liver disease?

Case-control studies that have investigated the association between alcoholism and alcohol-induced liver damage and the ADH2, ADH3, CYP2E1, and ADLH2 polymorphisms have reported controversial or inconclusive results. Thus, we conducted a meta-analysis of 50 association studies of the above polymorphisms. We explored potential sources of heterogeneity and bias, performed subgroup analyses by racial background and sex, performed sensitivity analyses for studies not in Hardy-Weinberg equilibrium, and performed a subgroup analysis for cases that met strict criteria for alcoholism. The present meta-analysis underscores significant associations of ADH2*1, ADH3*2, and ALDH2*1 alleles and the risk of alcoholism (OR = 1.89 [95% CI 1.56-2.28], 1.32 [95% CI 1.12-1.57], and 4.35 [95% CI 3.04-6.23], respectively). The subsequent subgroup analyses showed association for ADH2*1 and ADH3*2 only in East Asians (OR = 2.23 [95% CI 1.81-2.74] and 1.91 [95% CI 1.45-2.53], respectively) and East Asian males (OR = 2.21 [95% CI 1.57-3.10], 1.69 [95% CI 1.10-2.59], respectively). In East Asian males, the OR for ALDH2*1 was 3.66 (95% CI 1.68-7.96). In Caucasians, sensitivity analysis revealed an association for ADH2*1 in alcoholism (OR = 1.62 [95% CI 1.22-1.89]). When strict criteria were imposed, the pattern of results remained unaltered. For liver disease, there were no significant associations for ADH2*1, ADH3*2, or ALDH2*1 in all subpopulations. The CYP2E1 polymorphism showed no association whatsoever. There is evidence that alleles are mainly dominant. In conclusion, there was heterogeneity between studies in alcoholism for ADH2, ADH3, and ALDH2, and lack of bias in all polymorphisms. The above findings reinforce the need for more rigorous studies, and for regular synthesis of studies' results.

Evaluation in vinyl chloride monomer (VCM)-exposed workers and the relationship between liver lesions and gene polymorphisms of metabolic enzymes

AIM: The permissible exposure limit (PEL) of vinyl chloride monomer (VCM) in developed country was 1 p/m (2.79 mg/m3); and threshold limit value-short term exposure limit (TLV-STEL) in China was 11 times higher [11 p/m (30 mg/m3)] than it, till 2002. The mechanism of vinyl chloride monomer (VCM)-related carcinogenesis remains unclear. We aimed to analyze occupational health hazards exposure to doses lower than the Chinese occupational health standard in a selected VC polymerization plant in China, and also to elucidate the relationship between genetic polymorphisms and genetic susceptibility on liver lesions of workers exposed to VCM.

METHODS: In order to explore the mechanism of VCM-related health effects, we used a case-control design to investigate the association between the genetic polymorphisms of metabolic enzymes and liver lesions in workers occupationally exposed to VCM. Genotypes of CYP2E1, GSTT1, GSTM1, ALDH2 and ADH2 were identified using PCR and PCR-RFLP.

RESULTS: Even when the concentration of VCM was lower than the current Chinese occupational health standard, neurasthenia, pharyngeal irritation, liver ultrasonography abnormalities and hemoglobin disorders were significantly higher in exposure subjects compared to non-exposure subjects, and the relative risks (RR and 95% CI) were 1.74 (1.06-2.85), 1.97 (1.56-2.48), 10.69 (4.38-26.12), and 2.07 (1.20-3.57). CYP2E1 c1c2/c2c2 genotype was significantly associated with liver damages (OR 3.29, 95% CI 1.51-7.20, P < 0.01).

CONCLUSION: The incidences of neurasthenia and liver ultrasonography abnormalities significantly increase when the cumulative exposure dose increases. The genotypes of metabolic enzymes (CYP2E1 c1c2/c2c2, null GSTT1 and ADH2 1-1) play important roles in VCM metabolism. Polymorphisms of CYP 2E1, GSTT1 and ADH2 may be a major reason of genetic susceptibility in VCM-induced hepatic damage.

Cytochrome p450 2E1 polymorphisms and the risk of gastric cardia cancer

AIM: Genetic polymorphisms of drug-metabolizing enzymes have recently been shown to affect susceptibility to chemical carcinogenesis. Cytochrome P450 2E1 (CYP2E1) enzyme catalyzes the metabolism of many procarcinogens, such as N-nitrosamines and related compounds. The gene coding for this enzyme is polymorphic and thus may play a role in gastric cardia cancer (GCC) etiology. In this hospital-based case-control study, we evaluate the relationship between genetic polymorphisms of CYP2E1 and the risk of GCC.

METHODS: The study subjects comprised 159 histologically confirmed GCC cases identified via hospital cancer registry and surgical records at five hospitals in Fuzhou, Fujian Province, China, between April and November 2001. Controls were 192 patients admitted to the same hospitals for nonmalignant conditions. The genotypes of CYP2E1 were detected by a PCR-based RFLP assay. The odds ratios were estimated by logistic regression analyses and were adjusted for potential confounding factors.

RESULTS: The distribution of three genotypes of CYP2E1 in GCC cases and controls was significantly different (χ² = 16.04, P<0.01). The frequency of the CYP2E1 (c1/c1) genotype in GCC cases and controls was 60.4% and 40.1%, respectively. The CYP2E1 (c1/c1) genotype was associated with an increased risk for GCC (the adjusted (OR) was 2.37, 95% confidence interval (CI): 1.52-3.70). Subjects who carried the CYP2E1 (c1/c1) genotype and were habitual smokers were at a significantly higher risk of developing GCC (OR = 4.68, 95%CI: 2.19-10.04) compared with those who had the CYP2E1 (c1/c2 or c2/c2) genotype and did not smoke.

CONCLUSION: These results suggest that the CYP2E1 genotype may influence individual susceptibility to development of GCC, and that the risk increases significantly in smokers.

ADH1B*1, ADH1C*2, DRD2 (-141C Ins), and 5-HTTLPR are associated with alcoholism in Mexican American men living in Los Angeles

BACKGROUND

The aim of the present study was to use a candidate gene approach to identify the genetic risk factors for alcoholism in Mexican Americans residing in the Los Angeles area. The genes selected include alcohol metabolizing genes and neurotransmitter genes, which have been shown in the literature to be associated with alcoholism in other ethnic groups.

METHODS

Thirteen allelic variants from seven genes were evaluated for their role in alcoholism using alcoholic (n = 200) and nonalcoholic (n = 251) Mexican Americans. Those polymorphic sites include alcohol dehydrogenase (ADH1B, ADH1C), aldehyde dehydrogenase (ALDH2), cytochrome P-450 2E1 (CYP2E1) TaqI, DraI, RsaI, dopamine D2 receptor (DRD2) TaqI A, B, intron 6, exon 7, -141C Ins/Del, serotonin transporter (5-HTTLPR), and GABAA receptor beta3 subunit (GABRbeta3).

RESULTS

The results demonstrate that Mexican Americans have extremely low allele frequency for both ALDH2*2 and ADH1B*2 and a relatively high frequency of ADH1C*2 and CYP2E1 c2 alleles. ADH1B*1, ADH1C*2, DRD2 (-141C Ins), and 5-HTTLPR were associated with alcoholism in Mexican Americans (p < 0.05). DRD2 Ins was associated with alcoholism in those alcoholics who carried the ADH1B*2 or ADH1C*1 protective alleles (p = 0.032 in genotype level and p = 0.015 in allele level). DRD2 TaqI A and B alleles were associated with early age of onset for drinking (p = 0.016 for TaqI A1 and p = 0.049 for TaqI B1 allele).

CONCLUSIONS

Together, the data reveal unique genetic patterns in Mexican Americans that may be in part responsible for the heightened risk for alcoholism and alcohol-associated health problems in this population.

Association of cytochrome P450 2E1 polymorphisms and head and neck squamous cell cancer

The development of head and neck squamous cell cancer (HNSCC) is known to be strongly associated with tobacco use. One of the main enzymes for bioactivation of tobacco-related substances is the cytochrome 450 (CYP)2E1, of which different genetic variants are described. Analyzing a correlation between certain neoplasia and alteration of the CYP2E1 gene, most studies focus on the polymorphisms -1053C>T and 7632T>A, but recently another polymorphism, named -71G>T, with enhanced transcriptional activity, has been identified. In the current case-control study we investigate the putative association of the mentioned CYP2E1 polymorphisms on the risk of HNSCC. Comparing 312 German individuals with HNSCC to 299 controls we found a significantly enhanced risk for the development of that neoplasia in smoking carriers of -71G>T heterozygosity, while in -1053C>T and 7632T>A polymorphisms a corresponding correlation was absent. Since a coincidence of an aberrant p53 gene and CYP2E1 mutations has been described, we choose a subgroup of 140 patients with HNSCC for analyzing an association of mutations in these two genes. However, no such association could be found in either of the mentioned polymorphisms. Further studies have to focus on the -71G>T polymorphism and its possible linkage to cancers, in which smoking is a known risk-factor, as well as its functional relevance concerning the bioactivation of tobacco-related substances.

Expression of cytochrome P4502E1 gene in hepatocellular carcinoma

AIM: To investigate cytpchrome P4502E1 (CYP2E1) gene expression in occurrence and progression of hepatocellular carcinoma (HCC).

METHODS: The human liver arrayed library was spotted onto the nylon membranes to make cDNA array. Hybridization of cDNA array was performed with labeled probes synthesized from RNA isolated from HCC and adjacent liver tissues. Sprague-Dawley rats were administrated diethylnitrosamine (DENA) to induce HCC. CYP2E1 expression was detected by the method of RT-PCR and Northern blot analysis.

RESULTS: CYP2E1 was found by cDNA array hybridization to express differently between HCC and liver tissues. CYP2E1 only expressed in liver, but did not express in HCC tissues and expressed lowly in cirrhotic tissues. In the progression of cirrhosis and HCC, the expression level of CYP2E1 was gradually decreased and hardly detected until the late stage of HCC.

CONCLUSION: Using arrayed library to make cDNA arrays is an effective method to find differential expression genes. CYP2E1 is a unique gene expressing in liver but did not express in HCC. CYP2E1 expression descended along with the initiation and progression of HCC, which is noteworthy further investigations in its significance in the development of HCC.