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

No association of CYP2E1 genetic polymorphisms with alcohol dependence in Han Taiwanese population

Cytochrome P450 2E1 (CYP2E1) gene is one of the candidate genes for alcohol dependence (AD). Four single nucleotide polymorphisms (SNPs) of CYP2E1 gene (CYP2E1*1D, *5B, *6 and *1B) have been associated with AD previously in other ethnic populations. To date, only CYP2E1*5B and *6 SNPs have been investigated in relation to AD in our population. The objective of the study was to examine the genetic associations of CYP2E1 covering the four above-noted SNPs conjointly with AD in Han Taiwanese population based on single SNP analysis and haplotype-based approach. We enrolled a total of 340 patients fulfilling DSM-IV-TR diagnostic criteria of AD and 319 healthy controls and genotyped them for the above four SNPs of CYP2E1 gene. By comparing the differences of genotype, allele, and pertinent haplotype frequencies, we did not support a genetic association between CYP2E1 and AD in Han Taiwanese either by single allele tests or haplotype-based analyses.

The Pivotal Role of Aldehyde Toxicity in Autism Spectrum Disorder: The Therapeutic Potential of Micronutrient Supplementation

Autism spectrum disorder (ASD) is characterized by social and communication impairments as well as by restricted, repetitive patterns of behavior and interests. Genomic studies have not revealed dominant genetic errors common to all forms of ASD. So ASD is assumed to be a complex disorder due to mutations in hundreds of common variants. Other theories argue that spontaneous DNA mutations and/or environmental factors contribute to as much as 50% of ASD. In reviewing potential genetic linkages between autism and alcoholism, it became apparent that all theories of ASD are consistent with aldehyde toxicity, in which endogenous and exogenous aldehydes accumulate as a consequence of mutations in key enzymes. Aldehyde toxicity is characterized by cell-localized, micronutrient deficiencies in sulfur-containing antioxidants, thiamine (B1), pyridoxine (B6), folate, Zn²⁺, possibly Mg²⁺, and retinoic acid, causing oxidative stress and a cascade of metabolic disturbances. Aldehydes also react with selective cytosolic and membrane proteins in the cell of origin; then some types migrate to damage neighboring cells. Reactive aldehydes also form adducts with DNA, selectively mutating bases and inducing strand breakage. This article reviews the relevant genomic, biochemical, and nutritional literature, which supports the central hypothesis that most ASD symptoms are consistent with symptoms of aldehyde toxicity. The hypothesis represents a paradigm shift in thinking and has profound implications for clinical detection, treatment, and even prevention of ASD. Insight is offered as to which neurologically afflicted children might successfully be treated with micronutrients and which children are unlikely to be helped. The aldehyde toxicity hypothesis likely applies to other neurological disorders.

Present status and perspective of pharmacogenetics in Mexico

Drug costs account for up to 24% of the country's health expenditure and there are 13,000 registered drugs being prescribed. Diabetes is the main cause of death in the country, with over 85% of diabetic patients currently under drug treatment. The importance of knowing interindividual variability in drug metabolism on Mexican populations is thus evident. The purpose of this article is to provide an overlook of the current situation of pharmacogenetic research in Mexico, focusing on drug-metabolizing enzymes, and the possibility of developing a phenotyping cocktail for Mexican populations. So far, 21 pharmacogenetic studies on Mexican population samples (Mestizos and Amerindian) have been published. These have reported interindividual variability through phenotyping and/or genotyping cytochromes: CYP2D6, 2C19, 2C9, 2E1, and phase II enzymes UGT and NAT2. Some cytochromes with important clinical implications have not yet been phenotyped in Mexican populations. The development of a cocktail adapted to them could be a significant contribution to a larger knowledge on drug response variability at a lower price and shorter time. There are validated phenotyping cocktails that present several practical advantages, being valuable, safe, and inexpensive tools in drug metabolism characterization, which require only a single experiment to provide information on several cytochrome activities.

Polymorphisms in drug-metabolizing enzymes and risk to head and neck cancer: evidence for gene-gene and gene-environment interaction

A case-control study involving 750 cases with squamous-cell carcinoma of the head and neck (HNSCC) and an equal number of healthy controls was initiated to investigate the association of polymorphisms in the drug metabolizing genes cytochrome P450 1A1 (CYP1A1), CYP1B1, CYP2E1 and glutathione S-transferase M1 (GSTM1) with the risk of developing cancer. Attempts were also made to identify the role and nature of gene-gene and gene-environment interactions in modifying the susceptibility to HNSCC. Polymorphisms in drug metabolizing CYPs or GSTM1 showed modest associations with cancer risk. However, cases carrying haplotypes with variant alleles of both CYP1A1*2A and *2C or CYP1B1*2 and *3 or CYP2E1*5B and *6 were at significant risk of developing HNSCC. Likewise, cases carrying a combination of variant genotypes of CYPs and GSM1 (null) were at higher risk (up to 5-fold) of developing HNSCC. HNSCC risk also increased several-fold in cases carrying variant genotypes of CYPs who were regular tobacco smokers (8-18-fold), tobacco chewers (3-7-fold), or alcohol users (2-4-fold). Statistical analysis revealed a more than multiplicative interaction between combinations of the variant genotypes of CYPs and GSTM1 (null) and between variant genotypes and tobacco smoking or chewing or alcohol consumption, in both case-control and case-only designs. The data thus suggest that although polymorphisms in carcinogen-metabolizing CYPs may be a modest risk factor for developing HNSCC, gene-gene, and gene-environment interactions play a significant role in modifying the susceptibility to HNSCC.

Nur-related receptor 1 gene polymorphisms and alcohol dependence in Mexican Americans

AIM: To investigate the association of polymorphisms of nur-related receptor 1 (Nurr1) and development of alcohol dependence in Mexican Americans.

METHODS: Peripheral blood samples were collected from 374 alcoholic and 346 nonalcoholic Mexican Americans; these two groups were sex- and age-matched. Sample DNA was extracted and genomic DNA was amplified by polymerase chain reaction. The -2922(C) 2-3 polymerase chain reaction products were digested with Sau96I, alleles of 1345(G/C), and -1198(C/G) in the regulatory region as well as Ex+132 (G/T/A/C) and Ex+715(T/-) in exon 3 were studied by sequencing.

RESULTS: The C2/C2, C2/C3, C3/C3 genotype distribution of -2922(C) 2-3 was 34.4%, 38.2% and 27.5% in the nonalcoholic group compared to 23.3%, 51.2% and 25.4% in the alcoholic group (P = 0.001). The C/C, C/G, G/G genotype distribution of -1198(C/G) was 23.5%, 46.1% and 30.3% in the nonalcoholic group compared to 13.9%, 50.9% and 35.3% in the alcoholic group (P = 0.007). However, the -1345 (G/C), Ex3+132(G/T/A/C) and Ex3+715(T/-) alleles were not polymorphic in Mexican Americans, and all those studied had G/G, G/G and T/T genotype for these three alleles, respectively. The -2922(C) 2-3 did not show allele level difference between alcoholic and nonalcoholic individuals, but -1198 (C/G) showed a significant allele frequency difference between alcoholic (39.3%) and nonalcoholic (46.6%) populations (P = 0.005). Excluding obese individuals, significant differences were found at both genotypic and allelic levels for the -2922(C) 2-3 polymorphism (P = 0.000 and P = 0.049) and the -1198 (C/G) polymorphism (P = 0.008 and P = 0.032) between nonobese alcoholics and nonobese controls. Excluding smokers, a significant difference was found only at the genotypic level for the -2922(C) 2-3 polymorphism (P = 0.037) between nonsmoking alcoholics and nonsmoking controls, but only at the allelic level for the -1198(C/G) polymorphism (P = 0.034).

CONCLUSION: Polymorphisms in the regulatory region of Nurr1 are implicated in pathogenesis of alcohol dependence and the Nurr1/dopamine signaling pathway might be important for this dependence development in Mexican Americans.

Polymorphisms of alcohol metabolizing enzymes in indigenous Mexican population: unusual high frequency of CYP2E1*c2 allele

BACKGROUND

Alcohol abuse represents the major identified etiological factor of cirrhosis in México. ADH1B, ALDH2, and CYP2E1 have been considered candidate genes in alcohol-related diseases. Controversial results probably due to ethnic differences, among other factors, have been reported. Mexican Mestizos (MES) derive from the combination of indigenous, Spaniard, and African genes. Huichols (HUI) constitute an indigenous group from western Mexico with no racial admixture. We determined ADH1B*2, ALDH2*2, and CYP2E1*c2 allele frequencies in healthy HUI and MES from western Mexico. Lipid and hepatic profile were also carried out.

METHODS

One hundred and one HUI and 331 MES subjects were studied. Genotype and allele frequency were assessed through polymerase chain reaction-restriction fragment length polymorphism after DNA isolation from peripheral leukocytes. Commercial kits for lipid and hepatic determinations were used.

RESULTS

Polymorphic allele distribution in HUI was: 0%ADH1B*2, 0.5%ALDH2*2, 51.5%CYP2E1*c2; in MES: 3.4%ADH1B*2, 0%ALDH2*2, 16.1%CYP2E1*c2. Frequency of ADH1B*2 was statistically (p < 0.001) lower in HUI than MES. CYP2E1*c2 polymorphic allele was significantly higher (p < 0.0001) in HUI than MES. Hepatic profile was normal in both groups. HUI showed a better lipid profile than MES independently of genotype.

CONCLUSIONS

Huichols exhibited the highest CYP2E1*c2 allele frequency of the world documented up to this date; meanwhile, ADH1B*2 and ALDH2*2 were practically absent. This feature could be useful in the understanding of Mexican population gene composition, alcohol metabolism, and alcoholic liver disease development. However, further association studies are necessary. The heterogeneity of Mexican population was evidenced by the significantly different distribution of CYP2E1*c2 allele observed among different regions of the country. Lipid and hepatic values were not associated to genotype. This report constitutes the first study dealing with gene polymorphisms of alcohol metabolizing enzymes conducted in HUI.

The interaction of reward genes with environmental factors in contribution to alcoholism in mexican americans

BACKGROUND

Alcoholism is a polygenic disorder resulting from reward deficiency; polymorphisms in reward genes including serotonin transporter (5-HTT)-linked polymorphic region (5-HTTLPR), A118G in opioid receptor mu1 (OPRM1), and -141C Insertion/Deletion (Ins/Del) in dopamine receptor D2 (DRD2) as well as environmental factors (education and marital status) might affect the risk of alcoholism. Objective of the current study was to examine the main and interacting effect of these 3 polymorphisms and 2 environmental factors in contribution to alcoholism in Mexican Americans.

METHODS

Genotyping of 5-HTTLPR, OPRM1 A118G, and DRD2-141C Ins/Del was performed in 365 alcoholics and 338 nonalcoholic controls of Mexican Americans who were gender- and age-matched. Alcoholics were stratified according to tertiles of MAXDRINKS, which denotes the largest number of drinks consumed in one 24-hour period. Data analysis was done in the entire data set and in each alcoholic stratum. Multinomial logistic regression was conducted to explore the main effect of 3 polymorphisms and 2 environmental factors (education and marital status); classification tree, generalized multifactor dimensionality reduction (GMDR) analysis, and polymorphism interaction analysis version 2.0 (PIA 2) program were used to study factor interaction.

RESULTS

Main effect of education, OPRM1, and DRD2 was detected in alcoholic stratum of moderate and/or largest MAXDRINKS with education < or =12 years, OPRM1 118 A/A, and DRD2 -141C Ins/Ins being risk factors. Classification tree analysis, GMDR analysis, and PIA 2 program all supported education*OPRM1 interaction in alcoholics of largest MAXDRINKS with education < or =12 years coupled with OPRM1 A/A being a high risk factor; dendrogram showed synergistic interaction between these 2 factors; dosage-effect response was also observed for education*OPRM1 interaction. No definite effect of marital status and 5-HTTLPR in pathogenesis of alcoholism was observed.

CONCLUSIONS

Our results suggest main effect of education background, OPRM1 A118G, and DRD2 -141C Ins/Del as well as education*OPRM1 interaction in contribution to moderate and/or severe alcoholism in Mexican Americans. Functional relevance of these findings still needs to be explored.

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.

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.

Racial variations in the incidence of severe alcohol withdrawal

The use of race as a risk assessment tool and pharmacologic target has garnered recent attention and debate. It is currently unclear if a relationship between race and the development of severe alcohol withdrawal exists. We explored this potential relationship using several study groups.

METHODS

A simultaneous prospective enrollment of patients and retrospective chart review of severe alcohol withdrawal in two separate settings was performed comparing both the incidence of withdrawal and alcoholism based on race. These two study groups were then compared to an "at risk" group of alcoholics and the general ED population to determine differences in the distribution of race.

RESULTS

Individuals of white race in both study groups were at increased odds [OR 1.93 (CI 1.11-3.39) and 2.19 (CI 1.41-3.40)] of having severe alcohol withdrawal when compared to non-White "at risk" alcoholics. Blacks in both study groups however, appear to have lower odds [OR 0.23 (CI 0.11-0.47) and 0.11 (CI 0.05-0.23)] of having severe alcohol withdrawal when compared to non-Black "at risk" alcoholics.

CONCLUSIONS

Despite the controversial use of race in medical research and targeting therapies, there appears to be a difference in the odds of severe alcohol withdrawal based on race. The reasons for this finding are currently unclear.

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.

Alcohol and the liver

PURPOSE OF REVIEW

To update the reader with advances in epidemiology, genetics, detection, pathogenesis and therapy of alcohol-related liver disease.

RECENT FINDINGS

Ill-health due to alcohol abuse is improving in some nations but deteriorating in others. Oxidative and nitrosative stress are key to the pathogenesis of alcoholic liver disease, and there is now greater emphasis than previously on their development and role of cytochrome P450 2E1, on mitochondrial stress and disruption, (including elucidation of mitochondrial protection mechanisms) disturbance of signaling pathways and involvement of extrahepatic mediators like adiponectin. Treatment of alcoholic liver disease has stagnated, but transplantation is still favored and debated for end-stage cirrhosis.

SUMMARY

Basic and clinical research into the mechanisms of alcoholic liver disease is making headway, but has yet to produce safe and effective therapies for alcoholic hepatitis and for reversing cirrhosis.