ADH single nucleotide polymorphism associations with alcohol metabolism in vivo

Relationship between esophageal squamous cell carcinoma risk and alcohol-related ALDH2 and ADH1B polymorphisms: Evidence from a meta-analysis and Mendelian randomization analysis

BACKGROUND

Previous studies have shown that ALDH2 and ADH1B genes may be associated with alcohol metabolism and the risk of esophageal squamous cell carcinoma (ESCC), with inconsistent results. This meta-analysis aimed at comprehensively assessing the associations between ALDH2 and ADH1B polymorphisms and the risk of ESCC to synthesize and clarify the evidence.

METHODS

We calculated summary estimates of the associations between four genetic variants (rs671 and rs674 in ALDH2, and rs1229984 and rs1042026 in ADH1B) and the ESCC risk across 23 publications in the additive model and allelic model. Venice criteria, Bayesian false discovery probability (BFDP), and false-positive reporting probability (FPRP) were used to assess the strength of epidemiological evidence. Heterogeneity among studies was evaluated by using the Higgin's I2 statistic, and publication bias was assessed by using funnel plots and Begg's test. A Mendelian randomization (MR) analysis was performed to determine the causal association between alcohol intake and esophageal cancer risk. Data from the HaploReg v4.1 and PolyPhen-2 were analyzed for functional annotations.

RESULTS

Of the four genetic variants, rs671 of ALDH2 was associated with a significantly reduced risk of ESCC (OR: 0.60, 95% CI: 0.50-0.73), whereas rs1229984 of ADH1B was associated with a significantly increased risk (2.50, 95% CI: 1.70-3.69) in the additive model. In the allelic model, the variant rs1229984 of ADH1B also increased the risk of ESCC (OR: 1.50; 95% CI: 1.21-1.87). The result for the variant rs671 was considered as strong epidemiological evidence. Functional annotations identified that the four variants were related to the enhancer histone marks and motif changes. The other two variants were not associated with the ESCC risk (rs674 of ALDH2 OR: 1.22, 95% CI: 0.71-2.12; rs1042026 of ADH1B OR: 1.28, 95% CI: 0.52-3.14) in the additive model. The MR analysis did not find a causal effect of alcohol on the esophageal cancer risk.

CONCLUSIONS

The results showed that ADH1B rs1229984 was significantly associated with an increased the risk of ESCC.

The Impact of Alcohol Consumption and Oral Microbiota on Upper Aerodigestive Tract Carcinomas: A Pilot Study

Alcohol consumption is associated with oxidative stress and an increased risk of carcinoma of the upper aero-digestive tract (UADT). Recently, it has been found that some microorganisms in the human oral cavity may locally metabolize ethanol, forming acetaldehyde, a carcinogenic metabolite of alcohol. In a cohort of patients first visited for UADT cancers, we estimated their alcohol consumption by measuring Ethyl Glucuronide/EtG (a long-lasting metabolite of ethanol) in the hair and carbohydrate-deficient transferrin/CDT (short-term index of alcohol intake) in the serum. Moreover, we analyzed, by culture-based methods, the presence of Neisseria subflava, Streptococcus mitis, Candida albicans, and glabrata (microorganisms generating acetaldehyde) in the oral cavity. According to the EtG values, we correlated drinking alcohol with endogenous oxidative stress and the investigated microorganism's presence. We found that 55% of heavy drinkers presented microorganisms generating acetaldehyde locally. Moreover, we found that the presence of oral acetaldehyde-producing bacteria correlates with increased oxidative stress compared to patients without such bacteria. As for the study of alcohol dehydrogenase gene polymorphisms (the enzyme that transforms alcohol to acetaldehyde), we found that only the "CGTCGTCCC" haplotype was more frequent in the general population than in carcinoma patients. This pilot study suggests the importance of estimating alcohol consumption (EtG), the presence of bacteria producing acetaldehyde, and oxidative stress as risk factors for the onset of oral carcinomas.

Signatures of Convergent Evolution and Natural Selection at the Alcohol Dehydrogenase Gene Region are Correlated with Agriculture in Ethnically Diverse Africans

The alcohol dehydrogenase (ADH) family of genes encodes enzymes that catalyze the metabolism of ethanol into acetaldehyde. Nucleotide variation in ADH genes can affect the catalytic properties of these enzymes and is associated with a variety of traits, including alcoholism and cancer. Some ADH variants, including the ADH1B*48His (rs1229984) mutation in the ADH1B gene, reduce the risk of alcoholism and are under positive selection in multiple human populations. The advent of Neolithic agriculture and associated increase in fermented foods and beverages is hypothesized to have been a selective force acting on such variants. However, this hypothesis has not been tested in populations outside of Asia. Here, we use genome-wide selection scans to show that the ADH gene region is enriched for variants showing strong signals of positive selection in multiple Afroasiatic-speaking, agriculturalist populations from Ethiopia, and that this signal is unique among sub-Saharan Africans. We also observe strong selection signals at putatively functional variants in nearby lipid metabolism genes, which may influence evolutionary dynamics at the ADH region. Finally, we show that haplotypes carrying these selected variants were introduced into Northeast Africa from a West-Eurasian source within the last ∼2,000 years and experienced positive selection following admixture. These selection signals are not evident in nearby, genetically similar populations that practice hunting/gathering or pastoralist subsistence lifestyles, supporting the hypothesis that the emergence of agriculture shapes patterns of selection at ADH genes. Together, these results enhance our understanding of how adaptations to diverse environments and diets have influenced the African genomic landscape.

Alcohol-Induced Oxidative Stress and the Role of Antioxidants in Alcohol Use Disorder: A Systematic Review

Alcohol use disorder (AUD) is a highly prevalent, comorbid, and disabling disorder. The underlying mechanism of ethanol neurotoxicity and the involvement of oxidative stress is still not fully elucidated. However, ethanol metabolism has been associated with increased oxidative stress through alcohol dehydrogenase, the microsomal ethanol oxidation system, and catalase metabolic pathways. We searched the PubMed and genome-wide association studies (GWAS) catalog databases to review the literature systematically and summarized the findings focusing on AUD and alcohol abstinence in relation to oxidative stress. In addition, we reviewed the ClinicalTrials.gov resource of the US National Library of Medicine to identify all ongoing and completed clinical trials that include therapeutic interventions based on antioxidants. The retrieved clinical and preclinical studies show that oxidative stress impacts AUD through genetics, alcohol metabolism, inflammation, and neurodegeneration.

An advanced network pharmacology study to explore the novel molecular mechanism of Compound Kushen Injection for treating hepatocellular carcinoma by bioinformatics and experimental verification

Background

Compound Kushen Injection (CKI) is a Chinese patent drug that exerts curative effects in the clinical treatment of hepatocellular carcinoma (HCC). This study aimed to explore the targets and potential pharmacological mechanisms of CKI in the treatment of HCC.

Methods

In this study, network pharmacology was used in combination with molecular biology experiments to predict and verify the molecular mechanism of CKI in the treatment of HCC. The constituents of CKI were identified by UHPLC-MS/MS and literature search. The targets corresponding to these compounds and the targets related to HCC were collected based on public databases. To screen out the potential hub targets of CKI in the treatment of HCC, a compound-HCC target network was constructed. The underlying pharmacological mechanism was explored through the subsequent enrichment analysis. Interactive Gene Expression Profiling Analysis and Kaplan-Meier plotter were used to examine the expression and prognostic value of hub genes. Furthermore, the effects of CKI on HCC were verified through molecular docking simulations and cell experiments in vitro.

Results

Network analysis revealed that BCHE, SRD5A2, EPHX2, ADH1C, ADH1A and CDK1 were the key targets of CKI in the treatment of HCC. Among them, only CDK1 was highly expressed in HCC tissues, while the other 5 targets were lowly expressed. Furthermore, the six hub genes were all closely related to the prognosis of HCC patients in survival analysis. Molecular docking revealed that there was an efficient binding potential between the constituents of CKI and BCHE. Experiments in vitro proved that CKI inhibited the proliferation of HepG2 cells and up-regulated SRD5A2 and ADH1A, while down-regulated CDK1 and EPHX2.

Conclusions

This study revealed and verified the targets of CKI on HCC based on network pharmacology and experiments and provided a scientific reference for further mechanism research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03530-3.

Associations of Alcohol Dehydrogenase and Aldehyde Dehydrogenase Polymorphism With Cognitive Impairment Among the Oldest-Old in China

Recent literature suggested that ALDH2 mutation is associated with alcohol metabolism, and ethanol intake might jointly increase the risk of Alzheimer’s disease (AD) in mice. However, it is unclear whether this synergistic effect exists among humans. We examined the associations of four single nucleotide polymorphisms (SNPs) on aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH) genes (i.e., ALDH2 rs671, ADH1B rs1229984, ADH1B rs1042026, and ADH1C rs1693482) and cognitive impairment among the oldest-old. We also investigated whether this association was modified by ethanol intake from alcohol consumption. Data were from the Chinese Longitudinal Healthy Longevity Survey genetic sub-study, including 1,949 participants aged over 90 years. Participants with a Mini-Mental State Examination (MMSE) score of < 18 were considered cognitively impaired. Alcohol consumption was categorized as heavy, moderate, or never drinkers. With the dominant model, carrying A allele on rs671, C allele on rs1229984, and T allele on rs1042026 was associated with 33% (95% confidence interval [CI]: 5%, 69%), 33% (95% CI: 2%, 75%), and 29% (95% CI: 3%, 62%) higher odds of cognitive impairment in the multivariable-adjusted logistic model, respectively. We did not observe a significant interaction between those SNPs and alcohol consumption. Among the oldest-old, carrying ALDH2 rs671 mutation was associated with higher odds of cognitive impairment independent of alcohol consumption.

Maternal and offspring genetic risk score analyses of fetal alcohol exposure and attention-deficit hyperactivity disorder risk in offspring

Background

Studies investigating the effects of prenatal alcohol exposure on childhood attention‐deficit hyperactivity disorder (ADHD) symptoms using conventional observational designs have reported inconsistent findings, which may be affected by unmeasured confounding and maternal and fetal ability to metabolize alcohol. We used genetic variants from the alcohol metabolizing genes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), as proxies for fetal alcohol exposure to investigate their association with risk of offspring ADHD symptoms around age 7–8 years.

Methods

We used data from 3 longitudinal pregnancy cohorts: Avon Longitudinal Study of Parents and Children (ALSPAC), Generation R study (GenR), and the Norwegian Mother, Father and Child Cohort study (MoBa). Genetic risk scores (GRS) for alcohol use and metabolism using 36 single nucleotide polymorphisms (SNPs) from ADH and ALDH genes were calculated for mothers (N_ALSPAC = 8196; N_MOBA = 13,614), fathers (N_MOBA = 13,935), and offspring (N_ALSPAC=8,237; N_MOBA=14,112; N_GENR=2,661). Associations between maternal GRS and offspring risk of ADHD symptoms were tested in the full sample to avoid collider bias. Offspring GRS analyses were stratified by maternal drinking status.

Results

The pooled estimate in maternal GRS analyses adjusted for offspring GRS in ALSPAC and MoBa was OR = 0.99, 95%CI 0.97–1.02. The pooled estimate in offspring GRS analyses stratified by maternal drinking status across all the cohorts was as follows: OR_DRINKING = 0.98, 95% CI 0.94–1.02; OR_{NO DRINKING} = 0.99, 95% CI 0.97–1.02. These findings remained similar after accounting for maternal genotype data in ALSPAC and maternal and paternal genotype data in MoBa.

Conclusions

We did not find evidence for a causal effect of fetal alcohol exposure on risk of ADHD symptoms in offspring. The results may be affected by limited power to detect small effects and outcome assessment.

Association Study of Alcohol Dehydrogenase and Aldehyde Dehydrogenase Polymorphism With Alzheimer Disease in the Taiwanese Population

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) are two major alcohol-metabolizing enzymes. Moderate alcohol intake is a protective modified factor in Alzheimer’s disease (AD) while heavy alcohol intake and abstinence increased dementia risk. The associations between Alzheimer’s disease and alcohol-metabolizing genes are uncertain. This study examined the association of AD with seven ADH/ALDH single-nucleotide polymorphisms (SNPs), ADH1C rs2241894, ADH1B rs1229984, ALDH1B1 rs2073478, ALDH2 rs886205, rs4767944, rs4648328, and rs671. We enrolled 157 AD and 168 age- and sex-matched control subjects in pilot study to examine the association of AD with ADH/ALDH SNPs. Reconstructed ALDH2 haplotypes were performed. We measured plasma level of ADH1C and checked the interaction effect of AD–rs2241894 genotype on plasma ADH1C level. In extension study, we further examined 339 AD and 2,504 healthy control from the Taiwan Biobank. In pilot study, we observed that ADH1C rs2241894 TT genotype was negatively associated with AD in a recessive genetic model (OR = 0.25, 95% CI 0.09–0.75, p < 0.0001) in women. A strong linkage disequilibrium was observed among the four examined SNPs of ALDH2. No haplotype was related to AD. The plasma ADH1C level in AD was higher than that in control. After adjusted by age, sex, hypertension, diabetes mellitus, and alcohol, we found a significant interaction effect of AD–rs2241894 genotype on plasma ADH1C level (p = 0.04). This interaction effect was attributable to the association between AD and plasma ADH1C level (β estimate = 366, 95% CI 92.7∼639.4, p = 0.009). The genetic distribution of ADH1C rs2241894 showed strong ethnic heterogeneity, in which the T allele was the minor allele accounting for 28.5% in our study and 23.6% in East Asians, while it was a major allele in Americans, Europeans, and the global populations. No association was discovered between AD and the five SNPs: rs2241894, rs1229984, rs2073478, rs886205, and rs671 in the extension study. In summary, this study revealed a suggestive association between ADH1C rs2241894 and female AD in the pilot study, but failed to confirm this finding in a population database. Further age-matched and large sample size case-control studies are needed before rs2241894 can be interpreted as a protective genetic factor of AD.

MicroRNA hsa-miR-1301-3p Regulates Human ADH6, ALDH5A1 and ALDH8A1 in the Ethanol-Acetaldehyde-Acetate Metabolic Pathway

Alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases (ALDHs) are vital enzymes involved in the metabolism of a variety of alcohols. Differences in the expression and enzymatic activity of human ADHs and ALDHs correlate with individual variability in metabolizing alcohols and drugs and in the susceptibility to alcoholic liver disease. MicroRNAs (miRNAs) function as epigenetic modulators to regulate the expression of drug-metabolizing enzymes. To characterize miRNAs that target ADHs and ALDHs in human liver cells, we carried out a systematic bioinformatics analysis to analyze free energies of the interaction between miRNAs and their cognate sequences in ADH and ALDH transcripts and then calculated expression correlations between miRNAs and their targeting ADH and ALDH genes using a public data base. Candidate miRNAs were selected to evaluate bioinformatic predictions using a series of biochemical assays. Our results showed that 11 miRNAs have the potential to modulate the expression of two ADH and seven ALDH genes in the human liver. We found that hsa-miR-1301-3p suppressed the expression of ADH6, ALDH5A1, and ALDH8A1 in liver cells and blocked their induction by ethanol. In summary, our results revealed that hsa-miR-1301-3p plays an important role in ethanol metabolism by regulating ADH and ALDH gene expression. SIGNIFICANCE STATEMENT: Systematic bioinformatics analysis showed that 11 microRNAs might play regulatory roles in the expression of two alcohol dehydrogenase (ADH) and seven aldehyde dehydrogenase (ALDH) genes in the human liver. Experimental evidences proved that hsa-miR-1301-3p suppressed the expression of ADH6, ALDH5A1, and ALDH8A1 in liver cells and decreased their inducibility by ethanol.

Association between rs1229984 in ADH1B and cancer prevalence in a Japanese population

Alcohol consumption is an established risk factor for cancer, but little is known regarding the effect of genetic polymorphisms in alcohol metabolism genes on alcohol-related cancer risk in the Japanese population. Associations between the ADH1B gene (alcohol dehydrogenase 1B), single nucleotide polymorphism (SNP) rs1229984 and cancer have been extensively studied yet evidence is inconsistent. This population-based case-control study primarily aimed to clarify any association between SNP rs1229984 in both overall and specific cancer risk in a Japanese population. The functional non-synonymous SNP rs1229984 (Arg48His) was genotyped using DNA samples from 1,359 consecutive autopsy cases registered in The Japanese Single Nucleotide Polymorphisms for Geriatric Research database. Medical and pathological record data from this database were used to categorise cases and controls. Results included 1,359 participants, 816 cases and 543 controls. Multinomial logistic regression analyses showed no significant association between rs1229984 presence and overall cancer risk in both dominant and recessive genetic inheritance models [Arg/Arg+Arg/His vs. His/His: Adjusted odds ratio (OR)=0.66 (95% CI=0.39-1.13; P=0.129), Arg/Arg vs. Arg/His+His/His: OR=0.95 (95% CI=0.75-1.20; P=0.657)]. However, results showed those homozygous for rs1229984 (genotype His/His) were at significantly decreased odds of lung cancer than other genotypes [recessive model: OR=0.64 (95% CI=0.44-0.93; P=0.020]. In conclusion, there was no significant association between rs1229984 and odds of overall or specific cancers except in lung cancer where His/His genotype decreased odds. To the best of our knowledge, the association between His/His and decreased odds of lung cancer is a novel finding. These findings require further validation in larger studies.

The causal web of foetal alcohol spectrum disorders: a review and causal diagram

Foetal alcohol spectrum disorders (FASDs) are a leading cause of developmental disability. Prenatal alcohol use is the sole necessary cause of FASD, but it is not always sufficient. Multiple factors influence a child's susceptibility to FASD following prenatal alcohol exposure. Much of the FASD risk factor literature has been limited to discussions of association, rather than causation. While knowledge of predictor variables is important for identifying who is most at risk of FASD and for targeting interventions, causal knowledge is important for identifying effective mechanisms for prevention and intervention programmes. We conducted a systematic search and narrative synthesis of the evidence and used this to create a causal diagram (directed acyclic graph; DAG) to describe the causal pathways to FASD. Our results show that the aetiology of FASD is multifaceted and complex. FASD risk is determined by a range of lifestyle, sociodemographic, maternal, social, gestational, and genetic factors. The causal diagram that we present in this review provides a comprehensive summary of causal risk factors for FASD and can be used as a tool to inform data collection and statistical modelling strategies to minimise bias in future studies of FASD.

Integrated Analysis of DNA Copy Number Changes and Gene Expression Identifies Key Genes in Gastric Cancer

This study was aimed at identifying differentially expressed genes (DEGs) with copy number changes in gastric cancer (GC) pathogenesis. Microarray data GSE33429, including array-based comparative genomic hybridization and gene expression profiles, were obtained. DEGs were screened between GC and adjacent noncancerous tissues. Genes located at Minimum Common Regions (MCRs) were identified, and overlapped genes between DEGs and genes with amplification or deletion were identified. Gene Ontology function and pathway enrichment analysis of DEGs were performed. A protein-protein interaction network for DEGs was built, and significant modules were mined from the network. Functional annotation of genes in modules was also performed. A total of 677 up- and 583 downregulated DEGs were identified, including 37 overexpressed genes located at gained MCRs and 28 downregulated genes located at deleted MCRs. In significant modules, upregulated genes with amplification, including DSN1 (MIS12 kinetochore complex component), MAPRE1 (microtubule-associated protein, RP/EB family, member 1), TPX2 (microtubule-associated), UBE2C (ubiquitin-conjugating enzyme E2C), and MYBL2 (v-myb avian myeloblastosis viral oncogene homolog-like 2), were associated with cell cycle, but downregulated genes with deletion, including UGT2B15 (UDP glucuronosyltransferase 2 family, polypeptide B15), UGT2B17 (UDP glucuronosyltransferase 2 family, polypeptide B17), ADH1B (alcohol dehydrogenase 1B), and ADH1A (alcohol dehydrogenase 1A), were related to metabolism. The identified genes DSN1, MAPRE1, TPX2, UBE2C, and MYBL2 located at gained MCRs and UGT2B15, UGT2B17, ADH1B, and ADH1A located at deleted MCRs may play an important role in GC progression through regulating cell cycle and metabolism.

The association between alcohol metabolism and genetic variants of ADH1A, SRPRB, and PGM1 in Korea

BACKGROUND

Excessive alcohol consumption is a major public health problem in East Asian countries. Alcohol use leads to a cascade of problems including increased chances of risky behavior and a wide range of negative health consequences, from alcoholic liver disease to upper gastric and liver cancer. These alcohol effects are known to be influenced by ethnic variability and genetics.

METHODS

In this study, subjects were administered a single dose of alcohol (0.6 g/kg for men or 0.4 g/kg for women), and blood alcohol and acetaldehyde concentrations were measured eight times over 5 hours. To investigate genetically susceptible factors to alcohol metabolism, we selected single-nucleotide polymorphisms (SNP) of genes identified by prior genetic association studies for alcohol metabolism, alcohol consumption, alcohol dependence, and related traits, and performed genotyping on all subjects (n = 104).

RESULTS

We identified variations in the ADH1A, SRPRB, and PGM1 genes, which are directly associated with blood alcohol or acetaldehyde concentrations. Namely, the T allele of SRPRB rs17376019 and the C allele of PGM1 rs4643 were associated with lower blood alcohol levels, while the ADH1 rs1229976 C allele group exhibited markedly higher blood acetaldehyde levels than those of the ADH1 rs1229976 T allele group.

CONCLUSION

This study demonstrates that genetic variations in ADH1A, SRPRB, and PGM1 are associated with variations in blood alcohol and acetaldehyde concentration after alcohol intake.

Alcohol Intake Interacts with Functional Genetic Polymorphisms of Aldehyde Dehydrogenase (ALDH2) and Alcohol Dehydrogenase (ADH) to Increase Esophageal Squamous Cell Cancer Risk

INTRODUCTION

Studies have reported alcohol consumption and genetic variants as major contributing factors for esophageal squamous cell carcinoma (ESCC). However, the complicated interactions between alcohol and genetic factors involved in alcohol metabolism have not been well elucidated with respect to augmented risk of ESCC.

METHODS

We performed a large population-based case-control study in a Chinese city with a high ESCC incidence by enrolling 1190 case patients and 1883 controls. We integrated candidate single-nucleotide polymorphism data, detailed alcohol consumption records, gene-alcohol interactions, and single-nucleotide polymorphism functional information to untangle the complicated relationship between alcohol, variants of genes encoding alcohol metabolism enzymes, and ESCC risk. The gene-alcohol interaction was tested by including their product term in a multivariable logistic regression model. Synergy index and ratio of ORs were calculated to assess interaction on additive and multiplicative scale, respectively.

RESULTS

We confirmed two ESCC susceptibility loci, rs671 in aldehyde dehydrogenase 2 family member gene (ALDH2) and rs1042026 in alcohol dehydrogenase 1B (class I), beta polypeptide gene (ADH1B), that significantly altered alcohol consumption behavior and subsequently modified the association between alcohol consumption and ESCC risk. The rs671(A) allele was associated with ESCC risk in alcohol drinkers (adjusted odds ratio =1.98, 95% confidence interval [CI]: 1.51-2.60) but not in nondrinkers. Healthy individuals who carry different ALDH2 and ADH1B genotypes exhibit diversified drinking behavior, with the proportion of drinkers varying between 23.7% and 54.3%. Among individuals with a fast ethanol oxidization rate, we observed a strong interaction between heavy alcohol consumption and ethanal oxidization rate on both the additive scale (synergy index 4.80 [95% CI: 1.82-12.68]) and the multiplicative scale (ratio of ORs 2.93, 95% CI: 1.39-6.35).

CONCLUSIONS

Our observation highlights the need for preventing excessive use of alcohol, especially in individuals harboring active alcohol dehyrogenase and inactive ALDH2 variants.

Alcohol Dehydrogenases, Aldehyde Dehydrogenases, and Alcohol Use Disorders: A Critical Review

Alcohol use disorders (AUDs) are complex traits, meaning that variations in many genes contribute to the risk, as does the environment. Although the total genetic contribution to risk is substantial, most individual variations make only very small contributions. By far the strongest contributors are functional variations in 2 genes involved in alcohol (ethanol [EtOH]) metabolism. A functional variant in alcohol dehydrogenase 1B (ADH1B) is protective in people of European and Asian descent, and a different functional variant in the same gene is protective in those of African descent. A strongly protective variant in aldehyde dehydrogenase 2 (ALDH2) is essentially only found in Asians. This highlights the need to study a wide range of populations. The likely mechanism of protection against heavy drinking and AUDs in both cases is alteration in the rate of metabolism of EtOH that at least transiently elevates acetaldehyde. Other ADH and ALDH variants, including functional variations in ADH1C, have also been implicated in affecting drinking behavior and risk for alcoholism. The pattern of linkage disequilibrium in the ADH region and the differences among populations complicate analyses, particularly of regulatory variants. This critical review focuses upon the ADH and ALDH genes as they affect AUDs.

Using Mendelian Randomization to Decipher Mechanisms of Bone Disease

PURPOSE OF REVIEW

This review summarizes the basic principles of Mendelian randomization (MR) and provides evidence for the causal effect of multiple modifiable factors on bone outcomes.

RECENT FINDINGS

Several studies using MR approach have provided support for the causal effect of obesity on bone mineral density (BMD). Strikingly, studies have failed to prove a causal association between elevated 25(OH) D concentrations and higher BMD in community-dwelling individuals. The MR approach has been successfully used to evaluate multiple factors related to bone mineral density variation and/or fracture risk. The MR approach avoids some of the classical observational study limitations and provides more robust causal evidence, ensuring bigger success of the clinical trials. The selection of interventions based on genetic evidence could have a substantial impact on clinical practice.

Effect of alcohol dehydrogenase-1B and -7 polymorphisms on blood ethanol and acetaldehyde concentrations in healthy subjects with a history of moderate alcohol consumption

This study aims to evaluate the effect of ADH1B and ADH7 genotypes on blood acetaldehyde and ethanol levels after alcohol ingestion, and to measure the genotoxic effect of smoking and ethanol on the buccal cells, also controlling for ADH variants. We recruited healthy Italian subjects with at least a moderate history of alcohol consumption. All subjects were given an alcoholic drink of 0.4 g ethanol /kg of body weight. Blood venous samples were collected at baseline, and 30, 60, 90, and 120 minutes after ingestion. Buccal cells were collected before ethanol ingestion. Sixty subjects were enrolled in the study. Individuals with the ADH1B GG genotype had median ethanol levels of 5.0mM (IQR 3.4-7.2), and those with the ADH1B GT/TT genotype had 4.7mM (IQR 4.2-4.8). Corresponding acetaldehyde levels were 1.5μM (IQR 0.7-2.6) for ADH1B GG genotype and 1.6μM (IQR 1.5-1.7) for ADH1B CG/GG genotype. Individuals with the ADH7 CC genotype had median ethanol levels of 5.0mM (IQR 3.3-7.2), while 5.0mM (IQR 4.7-5.6) was in those with the ADH7 CG/GG genotype. Corresponding acetaldehyde levels were 1.5 μM (IQR 0.7-2.6) for ADH7 CC genotype and 1.5 μM (IQR 1.4-1.6) for ADH7 CG/GG genotypes. A non-significant increase in the frequency of karyolitic and pyknotic cells was found in the group of heavy drinkers and current smokers, when compared to the moderate drinkers and the non-smokers. Our study does not support the hypothesis that ADH1B and ADH7 genotypes affect blood ethanol and acetaldehyde concentration.

Genetic variants associated with Fabry disease progression despite enzyme replacement therapy

Enzyme replacement therapy (ERT) has been widely used for the treatment of Fabry disease, a rare X-linked recessive disorder due to absent or reduced activity of lysosomal enzyme α-galactosidase A. It is still unclear why some patients under ERT show disease progression typically with renal, cardiovascular and cerebrovascular dysfunctions. Here, we investigated the involvement of drug absorption, distribution, metabolism, and excretion gene variants in response variability to ERT, genotyping 37 patients with the Affymetrix Drug Metabolizing Enzyme and Transporters (DMET) Plus microarray. We found three single nucleotide polymorphisms in human alcohol dehydrogenase (ADH)4 gene (rs1126670, rs1126671, rs2032349) and one in ADH5 gene (rs2602836) associated with disease progression (p < 0.05). Our data provide a basic tool for identification of patient with ERT non-response risk that may represent a framework for personalized treatment of this rare disease.

A Systems Genetics Approach Identified GPD1L and its Molecular Mechanism for Obesity in Human Adipose Tissue

To explore novel molecular mechanisms underlying obesity, we applied a systems genetics framework to integrate risk genetic loci from the largest body mass index (BMI) genome-wide association studies (GWAS) meta-analysis with mRNA and microRNA profiling in adipose tissue from 200 subjects. One module was identified to be most significantly associated with obesity and other metabolic traits. We identified eight hub genes which likely play important roles in obesity metabolism and identified microRNAs that significantly negatively correlated with hub genes. This module was preserved in other three test gene expression datasets, and all hub genes were consistently downregulated in obese subjects through the meta-analysis. Gene GPD1L had the highest connectivity and was identified a key causal regulator in the module. Gene GPD1L was significantly negatively correlated with the expression of miR-210, which was experimentally validated that miR-210 regulated GPD1L protein level through direct interaction with its mRNA three prime untranslated region (3'-UTR). GPD1L was found to be upregulated during weight loss and weight maintenance induced by low calorie diet (LCD), while downregulated during weight gain induced by high-fat diet (HFD). The results indicated that increased GPD1L in adipose tissue may have a significant therapeutic potential in reducing obesity and insulin resistance.

Alcohol consumption and prostate cancer incidence and progression: A Mendelian randomisation study

Prostate cancer is the most common cancer in men in developed countries, and is a target for risk reduction strategies. The effects of alcohol consumption on prostate cancer incidence and survival remain unclear, potentially due to methodological limitations of observational studies. In this study, we investigated the associations of genetic variants in alcohol-metabolising genes with prostate cancer incidence and survival. We analysed data from 23,868 men with prostate cancer and 23,051 controls from 25 studies within the international PRACTICAL Consortium. Study-specific associations of 68 single nucleotide polymorphisms (SNPs) in 8 alcohol-metabolising genes (Alcohol Dehydrogenases (ADHs) and Aldehyde Dehydrogenases (ALDHs)) with prostate cancer diagnosis and prostate cancer-specific mortality, by grade, were assessed using logistic and Cox regression models, respectively. The data across the 25 studies were meta-analysed using fixed-effect and random-effects models. We found little evidence that variants in alcohol metabolising genes were associated with prostate cancer diagnosis. Four variants in two genes exceeded the multiple testing threshold for associations with prostate cancer mortality in fixed-effect meta-analyses. SNPs within ALDH1A2 associated with prostate cancer mortality were rs1441817 (fixed effects hazard ratio, HRfixed  = 0.78; 95% confidence interval (95%CI):0.66,0.91; p values = 0.002); rs12910509, HRfixed  = 0.76; 95%CI:0.64,0.91; p values = 0.003); and rs8041922 (HRfixed  = 0.76; 95%CI:0.64,0.91; p values = 0.002). These SNPs were in linkage disequilibrium with each other. In ALDH1B1, rs10973794 (HRfixed  = 1.43; 95%CI:1.14,1.79; p values = 0.002) was associated with prostate cancer mortality in men with low-grade prostate cancer. These results suggest that alcohol consumption is unlikely to affect prostate cancer incidence, but it may influence disease progression.

Exploration of a Polygenic Risk Score for Alcohol Consumption: A Longitudinal Analysis from the ALSPAC Cohort

BACKGROUND

Uncertainty remains about the true extent by which alcohol consumption causes a number of health outcomes. Genetic variants, or combinations of variants built into a polygenic risk score (PGRS), can be used in an instrumental variable framework to assess causality between a phenotype and disease outcome of interest, a method known as Mendelian randomisation (MR). We aimed to identify genetic variants involved in the aetiology of alcohol consumption, and develop a PGRS for alcohol.

METHODS

Repeated measures of alcohol consumption from mothers and their offspring were collected as part of the Avon Longitudinal Study of Parents and Children. We tested the association between 89 SNPs (identified from either published GWAS data or from functional literature) and repeated measures of alcohol consumption, separately in mothers (from ages 28-48) and offspring (from ages 15-21) who had ever reported drinking. We modelled log units of alcohol using a linear mixed model and calculated beta coefficients for each SNP separately. Cross-validation was used to determine an allelic score for alcohol consumption, and the AVENGEME algorithm employed to estimate variance of the trait explained.

RESULTS

Following correction for multiple testing, one SNP (rs1229984) showed evidence for association with alcohol consumption (β = -0.177, SE = 0.042, p = <0.0001) in the mothers. No SNPs showed evidence for association in the offspring after correcting for multiple testing. The optimal allelic score was generated using p-value cut offs of 0.5 and 0.05 for the mothers and offspring respectively. These scores explained 0.3% and 0.7% of the variance.

CONCLUSION

Our PGRS explains a modest amount of the variance in alcohol consumption and larger sample sizes would be required to use our PGRS in an MR framework.

Genetics of alcoholism

Multiple lines of evidence strongly indicate that genetic factors contribute to the risk for alcohol use disorders (AUD). There is substantial heterogeneity in AUD, which complicates studies seeking to identify specific genetic factors. To identify these genetic effects, several different alcohol-related phenotypes have been analyzed, including diagnosis and quantitative measures related to AUDs. Study designs have used candidate gene analyses, genetic linkage studies, genomewide association studies (GWAS), and analyses of rare variants. Two genes that encode enzymes of alcohol metabolism have the strongest effect on AUD: aldehyde dehydrogenase 2 and alcohol dehydrogenase 1B each has strongly protective variants that reduce risk, with odds ratios approximately 0.2-0.4. A number of other genes important in AUD have been identified and replicated, including GABRA2 and alcohol dehydrogenases 1B and 4. GWAS have identified additional candidates. Rare variants are likely also to play a role; studies of these are just beginning. A multifaceted approach to gene identification, targeting both rare and common variations and assembling much larger datasets for meta-analyses, is critical for identifying the key genes and pathways important in AUD.

Pharmacogenomics and the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is a clinically and biologically heterogeneous malignancy that is primarily treated with combinations of cytarabine and anthracyclines. Although this scheme remains effective in most of the patients, variability of outcomes in patients has been partly related with their genetic variability. Several pharmacogenetic studies have analyzed the impact of polymorphisms in genes encoding transporters, metabolizers or molecular targets of chemotherapy agents. A systematic review on all eligible studies was carried out in order to estimate the effect of polymorphisms of anthracyclines and cytarabine pathways on efficacy and toxicity of AML treatment. Other emerging genes recently studied in AML, such as DNA repair genes, genes potentially related to chemotherapy response or AML prognosis, have also been included.

Moderate alcohol drinking in pregnancy increases risk for children's persistent conduct problems: causal effects in a Mendelian randomisation study

BACKGROUND

Heavy alcohol use during pregnancy can cause considerable developmental problems for children, but effects of light-moderate drinking are uncertain. This study examined possible effects of moderate drinking in pregnancy on children's conduct problems using a Mendelian randomisation design to improve causal inference.

METHODS

A prospective cohort study (ALSPAC) followed children from their mother's pregnancy to age 13 years. Analyses were based on 3,544 children whose mothers self-reported either not drinking alcohol during pregnancy or drinking up to six units per week without binge drinking. Children's conduct problem trajectories were classified as low risk, childhood-limited, adolescence-onset or early-onset-persistent, using six repeated measures of the Strengths and Difficulties Questionnaire between ages 4-13 years. Variants of alcohol-metabolising genes in children were used to create an instrumental variable for Mendelian randomisation analysis.

RESULTS

Children's genotype scores were associated with early-onset-persistent conduct problems (OR = 1.29, 95% CI = 1.04-1.60, p = .020) if mothers drank moderately in pregnancy, but not if mothers abstained from drinking (OR = 0.94, CI = 0.72-1.25, p = .688). Children's genotype scores did not predict childhood-limited or adolescence-onset conduct problems.

CONCLUSIONS

This quasi-experimental study suggests that moderate alcohol drinking in pregnancy contributes to increased risk for children's early-onset-persistent conduct problems, but not childhood-limited or adolescence-onset conduct problems.

Drosophila and Caenorhabditis elegans as Discovery Platforms for Genes Involved in Human Alcohol Use Disorder

BACKGROUND

Despite the profound clinical significance and strong heritability of alcohol use disorder (AUD), we do not yet have a comprehensive understanding of the naturally occurring genetic variance within the human genome that drives its development. This lack of understanding is likely to be due in part to the large phenotypic and genetic heterogeneities that underlie human AUD. As a complement to genetic studies in humans, many laboratories are using the invertebrate model organisms (iMOs) Drosophila melanogaster (fruit fly) and Caenorhabditis elegans (nematode worm) to identify genetic mechanisms that influence the effects of alcohol (ethanol) on behavior. While these extremely powerful models have identified many genes that influence the behavioral responses to alcohol, in most cases it has remained unclear whether results from behavioral-genetic studies in iMOs are directly applicable to understanding the genetic basis of human AUD.

METHODS

In this review, we critically evaluate the utility of the fly and worm models for identifying genes that influence AUD in humans.

RESULTS

Based on results published through early 2015, studies in flies and worms have identified 91 and 50 genes, respectively, that influence 1 or more aspects of behavioral responses to alcohol. Collectively, these fly and worm genes correspond to 293 orthologous genes in humans. Intriguingly, 51 of these 293 human genes have been implicated in AUD by at least 1 study in human populations.

CONCLUSIONS

Our analyses strongly suggest that the Drosophila and C. elegans models have considerable utility for identifying orthologs of genes that influence human AUD.

Delayed ethanol elimination and enhanced susceptibility to ethanol-induced hepatosteatosis after liver resection

AIM: To investigate ethanol-induced hepatic steatosis after liver resection and the mechanisms behind it.

METHODS: First, the preliminary examination was performed on 6 sham-operated (Sham) and 30 partial hepatectomy (PH) male Wistar rats (8-wk-old) to evaluate the recovery of the liver weight and liver function after liver resection. PH rats were sacrificed at the indicated time points (4, 8, and 12 h; 1, 3, and 7 d) after PH. Second, the time point for the beginning of the chronic ethanol exposure (1 wk after sham- or PH-operation) was determined based on the results of the preliminary examination. Finally, pair-feeding was performed with a controlled diet or with a 5-g/dL ethanol liquid diet for 28 d in another 35 age-matched male Wistar rats with a one-week recovery after undergoing a sham- (n = 15) or PH-operation (n = 20) to evaluate the ethanol-induced liver injury after liver resection. Hepatic steatosis, liver function, fatty acid synthase (Fas) gene expression level, the expression of lipid metabolism-associated enzyme regulator genes [sterol regulatory element binding protein (Srebp)-1 and peroxisome proliferator-activated receptor (Ppar)-α], the mediators that alter lipid metabolism [plasminogen activator (Pai)-1 gene expression level and tumor necrosis factor (Tnf)-α production], and hepatic class-1 alcohol dehydrogenase (Adh1)-associated ethanol elimination were investigated in the 4 groups based on histological, immunohistochemical, biochemical, Western blotting, reverse transcriptase chain reaction, and blood ethanol concentration analyses. The relevant gene expression levels, liver weight, and liver function were assessed before and 1 wk after surgery to determine the subject’s recovery from the liver resection using the rats that had been subjected to the preliminary examination.

RESULTS: In the PH rats, ethanol induced marked hepatic steatosis with impaired liver functioning, as evidenced by the accumulation of fatty droplets within the hepatocytes, the higher increases in their hepatic triglyceride and blood alanine aminotransferase and blood aspartate aminotransferase levels after the 28-d pair-feeding period. The Sham-ethanol rats, not the PH-ethanol rats, demonstrated the up-regulation of Srebp-1 and the down-regulation of Ppar-α mRNA expression levels after the 28-d pair-feeding period. The 28-d ethanol administration induced the up-regulation of Pai-1 gene expression level and an overproduction of TNF-α in the Sham and the PH rats; however, the effect was more significant in the PH rats. The PH-ethanol rats (n = 4) showed higher residual blood ethanol concentrations than did the Sham-ethanol rats (n = 6) after a 5-h fast (0.66 ± 0.4 mg/mL vs 0.2 ± 0.1 mg/mL, P < 0.05); these effects manifested without up-regulation of Adh1 gene expression, which was present in the Sham-ethanol group after the 28-d pair-feeding period. One week after the liver resection, the liver weight, function, the gene expression levels of Fas, Srebp-1, Ppar-α, Pai-1 and Tnf-α recovered; however, the Adh1 gene expression did not recover in rats.

CONCLUSION: Desensitization to post-hepatectomy ethanol treatment and slow recovery from PH in Adh1 gene expression enhanced the susceptibility to ethanol-induced hepatic steatosis after PH in rats.

Simultaneous genotyping of single-nucleotide polymorphisms in alcoholism-related genes using duplex and triplex allele-specific PCR with two-step thermal cycles

We developed a time- and cost-effective multiplex allele-specific polymerase chain reaction (AS-PCR) method based on the two-step PCR thermal cycles for genotyping single-nucleotide polymorphisms in three alcoholism-related genes: alcohol dehydrogenase 1B, aldehyde dehydrogenase 2 and μ-opioid receptor. Applying MightyAmp(®) DNA polymerase with optimized AS-primers and PCR conditions enabled us to achieve effective and selective amplification of the target alleles from alkaline lysates of a human hair root, and simultaneously to determine the genotypes within less than 1.5 h using minimal lab equipment.

An enhancer-blocking element regulates the cell-specific expression of alcohol dehydrogenase 7

The class IV alcohol dehydrogenase gene ADH7 encodes an enzyme that is involved in ethanol and retinol metabolism. ADH7 is expressed mainly in the upper gastrointestinal tract and not in the liver, the major site of expression of the other closely related ADHs. We identified an intergenic sequence (iA1C), located between ADH7 and ADH1C, that has enhancer-blocking activity in liver-derived HepG2 cells that do not express their endogenous ADH7. This enhancer blocking function was cell- and position-dependent, with no activity seen in CP-A esophageal cells that express ADH7 endogenously. iA1C function was not specific to the ADH enhancers; it had a similar cell-specific effect on the SV40 enhancer. The CCCTC-binding factor (CTCF), an insulator binding protein, bound iA1C in HepG2 cells but not in CP-A cells. Our results suggest that in liver-derived cells, iA1C blocks the effects of ADH enhancers and thereby contributes to the cell specificity of ADH7 expression.

Alcohol consumption and lifetime change in cognitive ability: a gene × environment interaction study

Studies of the effect of alcohol consumption on cognitive ability are often confounded. One approach to avoid confounding is the Mendelian randomization design. Here, we used such a design to test the hypothesis that a genetic score for alcohol processing capacity moderates the association between alcohol consumption and lifetime change in cognitive ability. Members of the Lothian Birth Cohort 1936 completed the same test of intelligence at age 11 and 70 years. They were assessed for recent alcohol consumption in later life and genotyped for a set of four single-nucleotide polymorphisms in three alcohol dehydrogenase genes. These variants were unrelated to late-life cognition or to socioeconomic status. We found a significant gene × alcohol consumption interaction on lifetime cognitive change (p = 0.007). Individuals with higher genetic ability to process alcohol showed relative improvements in cognitive ability with more consumption, whereas those with low processing capacity showed a negative relationship between cognitive change and alcohol consumption with more consumption. The effect of alcohol consumption on cognitive change may thus depend on genetic differences in the ability to metabolize alcohol.

Genetics and genomics of alcohol sensitivity

Alcohol abuse and alcoholism incur a heavy socioeconomic cost in many countries. Both genetic and environmental factors contribute to variation in the inebriating effects of alcohol and alcohol addiction among individuals within and across populations. From a genetics perspective, alcohol sensitivity is a quantitative trait determined by the cumulative effects of multiple segregating genes and their interactions with the environment. This review summarizes insights from model organisms as well as human populations that represent our current understanding of the genetic and genomic underpinnings that govern alcohol metabolism and the sedative and addictive effects of alcohol on the nervous system.

Alcoholic liver disease: a synopsis of the Charles Lieber's Memorial Symposia 2009-2012

This paper is based upon the 'Charles Lieber Satellite Symposia' organized by Manuela G. Neuman at each of the 2009-2012 Research Society on Alcoholism (RSA) Annual Meetings. The presentations represent a broad spectrum dealing with alcoholic liver disease (ALD). In addition, a literature search (2008-2013) in the discussed area was performed in order to obtain updated data. The presentations are focused on genetic polymorphisms of ethanol metabolizing enzymes and the role of cytochrome P4502E1 (CYP2E1) in ALD. In addition, alcohol-mediated hepatocarcinogenesis, immune response to alcohol and fibrogenesis in alcoholic hepatitis as well as its co-morbidities with chronic viral hepatitis infections in the presence or absence of human deficiency virus are discussed. Finally, emphasis was led on alcohol and drug interactions as well as liver transplantation for end-stage ALD.

Alcohol Exposure In Utero and Child Academic Achievement

We examine the effect of alcohol exposure in utero on child academic achievement. As well as studying the effect of any alcohol exposure, we investigate the effect of the dose, pattern, and duration of exposure. We use a genetic variant in the maternal alcohol-metabolism gene ADH1B as an instrument for alcohol exposure, whilst controlling for the child's genotype on the same variant. We show that the instrument is unrelated to an extensive range of maternal and paternal characteristics and behaviours. OLS regressions suggest an ambiguous association between alcohol exposure in utero and children's academic attainment, but there is a strong social gradient in maternal drinking, with mothers in higher socio-economic groups more likely to drink. In stark contrast to the OLS, the IV estimates show negative effects of prenatal alcohol exposure on child educational attainment. These results are very robust to an extensive set of model specifications. In addition, we show that that the effects are solely driven by the maternal genotype, with no impact of the child's genotype.

Single-nucleotide polymorphisms interact to affect ADH7 transcription

BACKGROUND

The class IV alcohol dehydrogenase (ADH7, μ-ADH, σ-ADH) is important in the metabolism of ethanol and retinol. ADH7 is the only ADH not expressed in liver, instead being expressed mainly in the upper gastrointestinal tract. Genome-wide studies have identified significant associations between single-nucleotide polymorphisms in ADH7 and alcoholism and cancer, but the causative variants have not been identified.

METHODS

In vitro studies of gene expression by transient transfection into cell lines that express endogenous ADH7 (CP-A cells) and that do not (HepG2 cells).

RESULTS

We have identified transcriptional regulatory elements of ADH7 and observed differences in the effects of variants on gene expression in CP-A cells and HepG2 cells. Two haplotypes of the proximal promoter that differ in a single nucleotide at rs2851028, A7P-G and A7P-A, have different transcriptional activities. There is an interaction between variants farther upstream and these proximal variants: Upstream regulatory sequences generally showed a greater increase or smaller reduction in activity when combined with the A7P-A promoter than with the A7P-G promoter. A sequence located 12.5-kb upstream (7P10) can function as an enhancer. In CP-A cells, both haplotypes of 7P10 increased A7P-A activity by 2.5-fold while having only 1.2-fold effect on A7P-G. In HepG2 cells, the 7P10-TTT haplotype had no effect on the A7P-A promoter but decreased A7P-G promoter activity by 50%, whereas the CTT haplotype increased A7P-A activity by 50%, but had no effect on A7P-G.

CONCLUSIONS

These complex interactions indicate that the effects of variants in the ADH7 regulatory elements depend on both sequence and cellular context and should be considered in interpretation of the association of variants with alcoholism and cancer.

Prenatal alcohol exposure and childhood atopic disease: a Mendelian randomization approach

BACKGROUND

Alcohol consumption in western pregnant women is not uncommon and could be a risk factor for childhood atopic disease. However, reported alcohol intake may be unreliable, and associations are likely to be confounded.

OBJECTIVE

We aimed to study the relation between prenatal alcohol exposure and atopic phenotypes in a large population-based birth cohort with the use of a Mendelian randomization approach to minimize bias and confounding.

METHODS

In white mothers and children in the Avon Longitudinal Study of Parents and Children (ALSPAC) we first analyzed associations between reported maternal alcohol consumption during pregnancy and atopic outcomes in the offspring measured at 7 years of age (asthma, wheezing, hay fever, eczema, atopy, and total IgE). We then analyzed the relation of maternal alcohol dehydrogenase (ADH)1B genotype (rs1229984) with these outcomes (the A allele is associated with faster metabolism and reduced alcohol consumption and, among drinkers, would be expected to reduce fetal exposure to ethanol).

RESULTS

After controlling for confounders, reported maternal drinking in late pregnancy was negatively associated with childhood asthma and hay fever (adjusted odds ratio [OR] per category increase in intake: 0.91 [95% CI, 0.82-1.01] and 0.87 [95% CI, 0.78-0.98], respectively). However, maternal ADH1B genotype was not associated with asthma comparing carriers of A allele with persons homozygous for G allele (OR, 0.98 [95% CI, 0.66-1.47]) or hay fever (OR, 1.11 [95% CI, 0.71-1.72]), nor with any other atopic outcome.

CONCLUSION

We have found no evidence to suggest that prenatal alcohol exposure increases the risk of asthma or atopy in childhood.

Is ADH1C genotype relevant for the cardioprotective effect of alcohol?

The cardioprotective effect of ethanol has been suggested to be linked to one of the ethanol metabolizing enzymes (ADH1C), which constitutes a high V(max) and a low V(max) variant. This has been demonstrated in some studies, while others have not been able to replicate the findings. The aim of the present study was to investigate the relation between the different ADH1C genotypes, death from coronary heart disease (CHD) and alcohol in a material larger than the previously published studies. Eight hundred CHD deaths as well as 1303 controls were genotyped for the high V(max) (γ1) and the low V(max) (γ2) ADH1C variant. Information of alcohol use was available for all subjects. Multiple logistic regression analyses was used to study if the decreased risk of death from CHD in alcohol consuming subjects was more pronounced in subjects homozygous for the γ2 allele (γ2γ2 subjects) compared to γ1γ1 and γ1γ2 subjects. The odds ratio (OR) for death from CHD in alcohol consumers compared to abstainers was similar in the genotype groups, i.e., 0.62 (95% CI: 0.43-0.88) in γ1γ1 subjects and 0.62 (95% CI: 0.42-0.91) in γ2γ2 subjects. Also when stratifying the results by gender and when dividing alcohol consumers into different alcohol consumption groups, there was no difference in the OR between the different genotype groups. This study, which included the largest study group published so far, failed to find any link between the ADH1C genotype and the cardioprotective effects of alcohol.

Wege in die Abhängigkeit

Hintergrund: Riskanter Alkoholkonsum und Alkoholabhängigkeit treten in Industrieländern häufig auf und manifestieren sich oft bereits im jungen Erwachsenenalter. Wir prüfen in dieser Studie den Einfluss dysfunktionaler Lernmechanismen und deren Modulation durch verschiedene Stressoren, wie z. B. die Menge des Alkoholkonsums, auf die Entstehung, den Verlauf und ggf. die Aufrechterhaltung der Abhängigkeitserkrankung. Zielsetzung: Bisher bekannte ätiologische Faktoren, die im Zusammenhang mit der Entwicklung einer Alkoholabhängigkeit stehen, betreffen sowohl genetische (z. B. die genetisch bedingte geringe Sensitivität gegenüber der akuten Alkoholwirkung oder eine positive Familiengeschichte bezüglich Alkoholabhängigkeit) als auch umweltbedingten Faktoren (z. B. Stress, Trauma, dysfunktionale familiäre Strukturen und der Einfluss der Peers). Belohnungsabhängige Lernmechanismen könnten mit dem veränderten Alkoholkonsum in Adoleszenz und jungem Erwachsenenalter assoziiert sein und somit ebenfalls zu den prädisponierenden Faktoren für die Entwicklung einer Alkoholabhängigkeit zählen. Unser Wissen über diese Mechanismen ist bisher jedoch begrenzt. Im Rahmen der Studie „Learning in Alcohol Dependence“ (LeAD) sollen Lernmechanismen und ihre Bedeutung für die Entstehung exzessiven Alkoholkonsums untersucht werden. Zudem wird im Längsschnitt erfasst, wie sich der Alkoholkonsum selbst wieder auf diese Lernmechanismen auswirkt. Methodik: Eine Kohorte 18-jähriger Männer mit hohem versus niedrigem Risiko an einer Alkoholabhängigkeit zu erkranken, wird im Längsschnitt untersucht, wobei unter anderem bereits bekannte Risikofaktoren erfasst werden. Lernmechanismen werden mithilfe verschiedener Paradigmen (dem Pavlow’schen und instrumentellen Lernen, Habituierung und Devaluation sowie Risikoverhalten) behavioral und mittels funktioneller Bildgebung untersucht. Schlussfolgerungen: Bisher existieren keine Untersuchungen beim Menschen, in denen spezifische Veränderungen des Lernverhaltens mit prädisponierenden Faktoren für die Entwicklung einer Alkoholabhängigkeit in Zusammenhang gebracht werden. Durch die LeAD-Studie sollen diese Faktoren weiter aufgeklärt werden, wodurch eine zielgerichtete Prävention besser möglich werden könnte. Dadurch ließen sich speziell in dieser Altersgruppe Prävalenz und Schwere der Alkoholabhängigkeit beeinflussen.

Genetic instrumental variable studies of effects of prenatal risk factors

Identifying the effects of maternal risk factors during pregnancy on infant and child health is an area of tremendous research interest. However, policymakers are primarily interested in unraveling the causal effects of prenatal risk factors, not their associations with child health, which may be confounded by several unobserved factors. In this article, we evaluate the utility of genetic variants in three genes that have unequivocal evidence of being related to three major risk factors-CHRNA3 for smoking, ADH1B for alcohol use, and FTO for obesity-as instrumental variables for identifying the causal effects of such factors during pregnancy. Using two independent datasets, we find that these variants are overall predictive of the risk factors and are not systematically related to observed confounders, suggesting that they may be useful instruments. We also find some suggestive evidence that genetic effects are stronger during than before pregnancy. We provide an empirical example illustrating the use of these genetic variants as instruments to evaluate the effects of risk factors on birth weight. Finally, we offer suggestions for researchers contemplating the use of these variants as instruments.

Association of alcohol dehydrogenase polymorphisms and life-style factors with excessive alcohol intake within the Spanish population (EPIC-Spain)

AIMS

To analyse associations between alcohol dehydrogenase (ADH) polymorphisms and alcohol intake in Spanish men and women.

DESIGN AND SETTINGS

We analysed the relationship between 21 genetic variants in ADH genes and excessive alcohol intake in both men and women. Single nucleotide polymorphisms (SNPs) were genotyped using a customized array and a sex-stratified analysis was performed.

MEASUREMENTS

Ethanol intake was calculated using a validated dietary history questionnaire.

PARTICIPANTS

Heavy consumers of alcohol (≥70 g/day in men, ≥42 g/day in women) (653 cases) and very low or non-consumers (<2 g/day) (880 controls) from the Spanish cohort of the European Prospective Investigation into Cancer (EPIC).

FINDINGS

We found statistically significant associations between alcohol intake and known life-style factors; namely, smoking and food energy intake (meat and fruit/seeds) in both men and women, as well as with physical activity in women and educational level in men. Additionally, we found that a non-synonymous coding SNP in ADH1B (rs1229984) is associated inversely with excessive alcohol intake in men [odds ratio (OR) = 0.19, 95% confidence interval (CI) = 0.11-0.33; P = 4.77E(-10) ) and women (OR = 0.48, 95% CI = 0.27-0.83; P = 0.0067). Furthermore, ADH6 rs3857224 was found associated with heavy alcohol intake in women (OR = 1.61, 95% CI = 1.21-2.14; P = 1.01E(-3) ), but not in men.

CONCLUSIONS

In the Spanish population, the single nucleotide polymorphism of alcohol dehydrogenase ADH1B, rs1229984, is associated inversely with alcohol intake in both men and women. Another polymorphism of ADH6, rs3857224, is associated with heavy alcohol intake in women.

Fetal alcohol exposure and IQ at age 8: evidence from a population-based birth-cohort study

Background

Observational studies have generated conflicting evidence on the effects of moderate maternal alcohol consumption during pregnancy on offspring cognition mainly reflecting problems of confounding. Among mothers who drink during pregnancy fetal alcohol exposure is influenced not only by mother’s intake but also by genetic variants carried by both the mother and the fetus. Associations between children’s cognitive function and both maternal and child genotype at these loci can shed light on the effects of maternal alcohol consumption on offspring cognitive development.

Methods

We used a large population based study of women recruited during pregnancy to determine whether genetic variants in alcohol metabolising genes in this cohort of women and their children were related to the child’s cognitive score (measured by the Weschler Intelligence Scale) at age 8.

Findings

We found that four genetic variants in alcohol metabolising genes in 4167 children were strongly related to lower IQ at age 8, as was a risk allele score based on these 4 variants. This effect was only seen amongst the offspring of mothers who were moderate drinkers (1–6 units alcohol per week during pregnancy (per allele effect estimates were −1.80 (95% CI = −2.63 to −0.97) p = 0.00002, with no effect among children whose mothers abstained during pregnancy (0.16 (95%CI = −1.05 to 1.36) p = 0.80), p-value for interaction  = 0.009). A further genetic variant associated with alcohol metabolism in mothers was associated with their child’s IQ, but again only among mothers who drank during pregnancy.

The genetics of substance dependence

A large segment of the population suffers from addiction to alcohol, smoking, or illicit drugs. Not only do substance abuse and addiction pose a threat to health, but the consequences of addiction also impose a social and economic burden on families, communities, and nations. Genome-wide linkage and association studies have been used for addiction research with varying degrees of success. The most well-established genetic factors associated with alcohol dependence are in the genes encoding alcohol dehydrogenase (ADH), which oxidizes alcohol to acetaldehyde, and aldehyde dehydrogenase (ALDH2), which oxidizes acetaldehyde to acetate. Recently emerging genetic studies have linked variants in the genes encoding the α3, α5, and β4 nicotinic acetylcholine receptor subunits to smoking risk. However, the influence of these well-established genetic variants accounts for only a small portion of the heritability of alcohol and nicotine addiction, and it is likely that there are both common and rare risk variants yet to be identified. Newly developed DNA sequencing technologies could potentially advance the detection of rare variants with a larger impact on addiction risk.

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 genetic basis of alcoholism: multiple phenotypes, many genes, complex networks

Alcoholism is a significant public health problem. A picture of the genetic architecture underlying alcohol-related phenotypes is emerging from genome-wide association studies and work on genetically tractable model organisms.

Genome-wide significant association between alcohol dependence and a variant in the ADH gene cluster

Alcohol dependence (AD) is an important contributory factor to the global burden of disease. The etiology of AD involves both environmental and genetic factors, and the disorder has a heritability of around 50%. The aim of the present study was to identify susceptibility genes for AD by performing a genome-wide association study (GWAS). The sample comprised 1333 male in-patients with severe AD according to the Diagnostic and Statistical Manual of Mental Disorders, 4th edition, and 2168 controls. These included 487 patients and 1358 controls from a previous GWAS study by our group. All individuals were of German descent. Single-marker tests and a polygenic score-based analysis to assess the combined contribution of multiple markers with small effects were performed. The single nucleotide polymorphism (SNP) rs1789891, which is located between the ADH1B and ADH1C genes, achieved genome-wide significance [P = 1.27E-8, odds ratio (OR) = 1.46]. Other markers from this region were also associated with AD, and conditional analyses indicated that these made a partially independent contribution. The SNP rs1789891 is in complete linkage disequilibrium with the functional Arg272Gln variant (P = 1.24E-7, OR = 1.31) of the ADH1C gene, which has been reported to modify the rate of ethanol oxidation to acetaldehyde in vitro. A polygenic score-based approach produced a significant result (P = 9.66E-9). This is the first GWAS of AD to provide genome-wide significant support for the role of the ADH gene cluster and to suggest a polygenic component to the etiology of AD. The latter result may indicate that many more AD susceptibility genes still await identification.