Influence of genetic admixture on polymorphisms of alcohol-metabolizing enzymes: analyses of mutations on the CYP2E1, ADH2, ADH3 and ALDH2 genes in a Mexican-American population living in the Los Angeles area

Spontaneous evolution in bilirubin levels predicts liver-related mortality in patients with alcoholic hepatitis

The accurate prognostic stratification of alcoholic hepatitis (AH) is essential for individualized therapeutic decisions. The aim of this study was to develop a new prognostic model to predict liver-related mortality in Asian AH patients. We conducted a hospital-based, retrospective cohort study using 308 patients with AH between 1999 and 2011 (a derivation cohort) and 106 patients with AH between 2005 and 2012 (a validation cohort). The Cox proportional hazards model was constructed to select significant predictors of liver-related death from the derivation cohort. A new prognostic model was internally validated using a bootstrap sampling method. The discriminative performance of this new model was compared with those of other prognostic models using a concordance index in the validation cohort. Bilirubin, prothrombin time, creatinine, potassium at admission, and a spontaneous change in bilirubin levels from day 0 to day 7 (SCBL) were incorporated into a model for AH to grade the severity in an Asian patient cohort (MAGIC). For risk stratification, four risk groups were identified with cutoff scores of 29, 37, and 46 based on the different survival probabilities (P<0.001). In addition, MAGIC showed better discriminative performance for liver-related mortality than any other scoring system in the validation cohort. MAGIC can accurately predict liver-related mortality in Asian patients hospitalized for AH. Therefore, SCBL may help us decide whether patients with AH urgently require corticosteroid treatment.

Alcoholism and liver disease in Mexico: Genetic and environmental factors

Alcoholism and cirrhosis, which are two of the most serious health problems worldwide, have a broad spectrum of clinical outcomes. Both diseases are influenced by genetic susceptibility and cultural traits that differ globally but are specific for each population. In contrast to other regions around the world, Mexicans present the highest drinking score and a high mortality rate for alcoholic liver disease with an intermediate category level of per capita alcohol consumption. Mexico has a unique history of alcohol consumption that is linked to profound anthropological and social aspects. The Mexican population has an admixture genome inherited from different races, Caucasian, Amerindian and African, with a heterogeneous distribution within the country. Thus, genes related to alcohol addiction, such as dopamine receptor D2 in the brain, or liver alcohol-metabolizing enzymes, such as alcohol dehydrogenase class I polypeptide B, cytochrome P450 2E1 and aldehyde dehydrogenase class 2, may vary from one individual to another. Furthermore, they may be inherited as risk or non-risk haplogroups that confer susceptibility or resistance either to alcohol addiction or abusive alcohol consumption and possibly liver disease. Thus, in this era of genomics, personalized medicine will benefit patients if it is directed according to individual or population-based data. Additional association studies will be required to establish novel strategies for the prevention, care and treatment of liver disease in Mexico and worldwide.

Association between in vivo alcohol metabolism and genetic variation in pathways that metabolize the carbon skeleton of ethanol and NADH reoxidation in the alcohol challenge twin study

BACKGROUND

Variation in alcohol metabolism affects the duration of intoxication and alcohol use. While the majority of genetic association studies investigating variation in alcohol metabolism have focused on polymorphisms in alcohol or aldehyde dehydrogenases, we have now tested for association with genes in alternative metabolic pathways that catalyze the carbon skeleton of ethanol (EtOH) and NADH reoxidation.

METHODS

Nine hundred fifty single nucleotide polymorphisms (SNPs) spanning 14 genes (ACN9, ACSS1, ACSS2, ALDH1A1, CAT, CYP2E1, GOT1, GOT2, MDH1, MDH2, SLC25A10, SLC25A11, SLC25A12, SLC25A13) were genotyped in 352 young adults who participated in an alcohol challenge study. Traits tested were blood alcohol concentration (BAC), breath alcohol concentration (BrAC), peak alcohol concentration, and rates of alcohol absorption and elimination. Allelic association was tested using quantitative univariate and multivariate methods.

RESULTS

A CYP2E1 promoter SNP (rs4838767, minor allele frequency 0.008) exceeded the threshold for study-wide significance (4.01 × 10(-5) ) for 2 early BAC, 8 BrAC measures, and the peak BrAC. For each phenotype, the minor C allele was related to a lower alcohol concentration, most strongly for the fourth BrAC (p = 2.07 × 10(-7) ) explaining ~8% of the phenotypic variance. We also observed suggestive patterns of association with variants in ALDH1A1 and on chromosome 17 near SLC25A11 for aspects of blood and breath alcohol metabolism. An SNP upstream of GOT1 (rs2490286) reached study-wide significance for multivariate BAC metabolism (p = 0.000040).

CONCLUSIONS

Overall, we did not find strong evidence that variation in genes coding for proteins that further metabolize the carbon backbone of acetaldehyde, or contribute to mechanisms for regenerating NAD from NADH, affects alcohol metabolism in our European-descent subjects. However, based on the breath alcohol data, variation in the promoter of CYP2E1 may play a role in preabsorptive or early hepatic alcohol metabolism, but more samples are required to validate this finding.

The amount of alcohol consumption negatively impacts short-term mortality in Mexican patients with alcoholic hepatitis

OBJECTIVES

Mexicans have an increased rate of alcohol abuse and alcoholic liver disease. Factors influencing the severity of alcoholic hepatitis (AH) in Mexicans are unknown. The aims of the present study were to identify the prognostic factors of short-term mortality in Mexican patients with AH and to validate the existing prognostic models.

METHODS

One hundred seventy-five consecutive patients with AH were recruited from four hospital centers in Mexico. Demographic, clinical, and biochemical parameters were obtained at admission. Univariate and multivariate logistic regression analyses were used for the identification of prognostic factors. The accuracy of different models was evaluated by their area under the receiver operating characteristic (AUROC) curve and comparative risk analysis was performed using the Kaplan-Meier method.

RESULTS

Age, serum creatinine, serum bilirubin, leukocyte count, and alcohol consumption >120 g/day were independently associated with short-term mortality. The impact of alcohol consumption was significant among patients with severe AH (48 vs. 72% risk of death, P=0.03). The AUROC (95% confidence interval) curves for the different scores were Maddrey's discriminant function 0.79 (0.72-0.86); model for end-stage liver disease (MELD) 0.83 (0.75-0.89); Glasgow AH score 0.77 (0.70-0.84); and age-bilirubin-international normalized ratio-creatinine (ABIC) score 0.82 (0.75-0.88). The ABIC score allowed an accurate stratification into three different risk subgroups with 13%, 50%, and 81% mortality rate at 90 days (P<0.001).

CONCLUSIONS

The amount of alcohol consumption has a negative impact on short-term mortality among Mexicans with AH. The ABIC score is useful and comparable with MELD score for the prognostic stratification of these patients.

Association between a serotonin transporter gene variant and hopelessness among men in the Heart and Soul Study

BACKGROUND

Hopelessness is associated with mortality in patients with cardiac disease even after accounting for severity of depression. We sought to determine whether a polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) is associated with increased hopelessness, and whether this effect is modified by sex, age, antidepressant use or depression in patients with coronary heart disease.

METHODS

We conducted a cross-sectional study of 870 patients with stable coronary heart disease. Our primary outcomes were hopelessness score (range 0-8) and hopeless category (low, moderate and high) as measured by the Everson hopelessness scale. Analysis of covariance and ordinal logistic regression were used to examine the independent association of genotype with hopelessness.

RESULTS

Compared to patients with l/l genotype, adjusted odds of a higher hopeless category increased by 35% for the l/s genotype and 80% for s/s genotype (p-value for trend = 0.004). Analysis of covariance demonstrated that the effect of 5-HTTLPR genotype on hopelessness was modified by sex (.04), but not by racial group (p = 0.63). Among men, odds of higher hopeless category increased by 40% for the l/s genotype and by 2.3-fold for s/s genotype (p-value p < 0.001), compared to no effect in the smaller female sample (p = 0.42). Results stratified by race demonstrated a similar dose-response effect of the s allele on hopelessness across racial groups.

CONCLUSIONS

We found that the 5-HTTLPR is independently associated with hopelessness among men with cardiovascular disease.

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.

Genetics of alcohol dependence

Alcohol dependence (AD), a genetically influenced phenotype, is extremely costly to individuals and to society in the United States and throughout the world, contributing to morbidity and mortality and a host of economic, interpersonal, and societal problems. Although until recently the only genes established to affect risk for AD were those encoding several alcohol metabolizing enzymes, there are now several other genes that can be regarded as confirmed risk loci, discovered through linkage and candidate gene association studies. While the mechanism of action of the effects of alcohol-metabolizing enzymes on AD risk is thought to be well understood, we are still in the early stages of understanding the physiology of other risk loci. Further, it is clear that only a small number of the many genes that influence risk for AD have been identified. Newer methodologies (e.g., genomewide association, study of copy number variation, and deep sequencing of candidate loci to identify rare risk variants) that have improved our understanding of other complex traits hold the promise of identifying a greater set of AD susceptibility loci.

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.

Biological research on drug abuse and addiction in Hispanics: current status and future directions

Impressive progress has been made in the understanding of biological contributions to drug abuse and addiction. An area that has only recently begun to receive attention is potential ethnic and racial differences in biological systems that contribute to, or protect from, problem drug use. This article reviews recent research on drug abuse and addiction in Hispanics in which biological questions have been addressed, including work on genes, gene products (proteins), physiology and pharmacotherapy. Taken together, work to date suggests that there are both similarities and differences between Hispanics and other ethnic groups in biological factors related to drug abuse and addiction. Although the results are intriguing, relatively few studies have been done, and those that have been done have often been inconclusive due to low numbers of Hispanic subjects. Moreover, studies have often failed to recognize the complexity and heterogeneity of Hispanic populations in the United States and around the world. After reviewing the current status of the field, recommendations are given for future research in both humans and relevant animal models that will lead to a better understanding of drug abuse and addiction in Hispanics.

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.

Alcohol intake, drinking patterns, and risk of nonfatal acute myocardial infarction in Costa Rica

BACKGROUND

Moderate alcohol consumption is associated with a lower risk of myocardial infarction (MI). Whether alcohol is truly protective or whether the amount, type, or pattern of intake is the most important is still under debate.

OBJECTIVE

The purpose of this study was to determine whether alcohol intake and drinking patterns are associated with plasma lipids and the risk of MI in Costa Ricans, a population with a low intake of wine.

DESIGN

We conducted a study of 2090 cases of a first nonfatal acute MI and 2090 population-based controls matched by age, sex, and residence in Costa Rica, a country with diet and lifestyles different from those of Western countries. Alcohol and dietary intakes were assessed by using validated questionnaires.

RESULTS

In a multivariate conditional regression model that controlled for other cardiovascular disease risk factors, the lowest risk of MI [odds ratio (OR) = 0.44; 95% CI: 0.31, 0.61] was observed for those who drank on average 3 drinks/wk (compared with lifelong abstainers). When we looked at the frequency of consumption, we found that the risk of MI among daily drinkers (OR = 0.64; 95% CI: 0.41, 1.01) was not significantly different (P = 0.23) from that of weekend drinkers (OR = 0.76; 95% CI: 0.59, 0.98) regardless of the amount consumed. HDL cholesterol increased with the amount and frequency of alcohol intake. Similar to a few other populations, apparent protection was observed at very low alcohol intakes.

CONCLUSION

Low to moderate consumption of alcohol 1-2 d/wk is independently associated with a reduced risk of MI.

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.

Polymorphisms of the dopamine D2 receptor, serotonin transporter, and GABA(A) receptor beta(3) subunit genes and alcoholism in Mexican-Americans

The etiology of alcohol dependence is a complex interaction of psychosocial and biologic factors. To study the impact of genetic factors that play an important role in an individual's vulnerability to alcohol abuse and dependence, we examined the genetic variations of the major neurotransmitter genes, including the dopamine D2 receptor (DRD2) TaqI A, B, and -141C insertion/deletion (Ins/Del) polymorphisms, the serotonin transporter-linked polymorphic region (5-HTTLPR), and the gamma-aminobutyric acid A (GABA(A)) receptor beta(3) subunit gene (GABRbeta3), for 130 Mexican-American alcoholic men and 251 nonalcoholic control subjects (105 men and 146 women). The genotype frequency for the DRD2 -141C Ins/Del allele was significantly different between alcoholic and control subjects (P=.007). The frequency of the 5-HTTLPR short (S) allele was significantly higher in alcoholic individuals (61.5%) than in nonalcoholic control subjects (52.8%; P=.021). When smokers were excluded from both control and alcoholic groups, the association between the DRD2 -141C Ins allele, as well as between the 5-HTTLPR S allele, and alcoholism became significant at both genotypic and allelic levels. No positive association was found between alcoholism and the DRD2 TaqI A or B, or the GABRbeta3, genotype. Our findings indicate that the DRD2 -141C Ins allele and the 5-HTTLPR S allele are genetic risk factors for alcoholism in Mexican-Americans, and that smoking modulates the association between genetic risk factors and alcoholism.