Single nucleotide polymorphisms of the ALDH2 gene in six Indian populations

Meta-Analysis on the Association of Neuropeptide Y rs16139 Variant With the Risk of Alcoholism

Introduction: The neuropeptide-Y (NPY) is involved in the development of alcoholism through NPY receptors. A T>C mutation causes substitution of leucine to proline at codon 7 (L7P; rs16139) in the signal peptide of neuropeptide Y is known to cause a 42% increase in plasma NPY levels. Studies that analyzed the association between NPY rs16139 and alcoholism risk did not demonstrate conclusive evidence for this relationship. The present study aims to evaluate the association between NPY gene rs16139 variant and alcohol dependence. Method: An electronic search of databases including PubMed and Google Scholar was performed to retrieve studies investigating the association between NPY rs16139 and alcoholism. The pooled odds ratio (OR) with 95% confidence interval (CI) was calculated in allelic and dominant genetic models. Sensitivity analyses and publication bias were assessed in our meta-analysis. The meta-analysis was conducted using the MetaGenyo web tool. Result: Significant heterogeneity was observed across studies (p < 0.001). Our results have shown that there is no significant association between NPY rs16139 variant and the risk of alcoholism in allelic (OR = 0.98, 95% CI 0.70-1.38, p = 0.921) and dominant models (OR = 0.98, 95% CI 0.69-1.40, p = 0.919). Begg's funnel plot and Egger's test have not shown publication bias (p = 0.332). Conclusion: To the best of our knowledge, this is the first meta-analysis that evaluates the relationship between the NPY rs16139 polymorphism and the risk of alcoholism. Our large-scale meta-analysis suggests that NPY rs16139 polymorphism is not associated with alcoholism. However, further studies are needed to increase our understanding of the relationship between NPY variants in alcoholism.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

An integrative bioinformatics pipeline to demonstrate the alteration of the interaction between the ALDH2*2 allele with NAD+ and Disulfiram

Alcohol use disorder (AUD) is a multifactorial psychiatric behavior disorder. Disulfiram is the first approved drug by the Food and Drug Administration for alcohol-dependent patients, which targets the ALDH2 enzyme. Several genes are known to be involved in alcohol metabolism; mutations in any of these genes are known to be associated with AUD. The E504K mutation in the ALDH2 of the precursor protein or the E487K of the mature protein (E504K/E487K; ALDH2*2 allele) is carried by approximately 8% of the world population. In this study, we aimed to test the known inactive allele ALDH2*2, to validate the use of our extensive computational pipeline (in silico tools, molecular modeling, and molecular docking) for testing the interaction between the ALDH2*2 allele, NAD^+, and Disulfiram. In silico predictions showed that the E504K variant of ALDH2 to be pathogenic and destabilizing with the maximum number of prediction in silico tools. Consequently, we studied the effect of this mutation mainly on the interaction between NAD⁺ -E504K and Disulfiram-E504K complexes using molecular docking technique, and molecular dynamics (MD) analysis. From the molecular docking analysis with NAD⁺ , we observed that the interaction affinity of the NAD⁺ decreases with the impact of E504K variant. On the other hand, the drug Disulfiram showed similar interaction in both the native and mutant ALDH2 proteins. Further, the comprehensive MD analysis predicted that the E504K destabilizes the protein and influences the NAD⁺ and Disulfiram interactions. Our findings reveal that the interaction of NAD⁺ to the protein is disturbed by the E504K/E487K variant whereas the drug Disulfiram has a similar effect as both native ALDH2 and ALDH2 bearing E504K/E487K variant. This study provides a platform to understand the effect of E504K/E487K on the molecular interaction with NAD⁺ and Disulfiram.

Genetic Polymorphisms of the Mitochondrial Aldehyde Dehydrogenase ALDH2 Gene in a Large Ethnic Hakka Population in Southern China

Background

Human mitochondrial aldehyde dehydrogenase 2 (ALDH2) plays a critical role in the detoxification of the ethanol metabolite acetaldehyde. The ALDH2*2 (rs671) gene variant is mainly absent among Europeans but is prevalent in populations in East Asia. The aim of this study was to investigate ALDH2*2 mutant alleles and genotype frequencies in the Hakka population of China.

Material/Methods

Between January 2016 and June 2017, 7,966 unrelated individuals were recruited into the study from the Hakka ethnic population residing in the Meizhou area of Guangdong Province, China, who provided venous blood samples. Genotyping of ALDH2 genotypes were determined using a gene chip platform and confirmed by DNA sequencing.

Results

In the 7,966 individuals from the Hakka population of China in this study, the frequencies of the ALDH2 genotypes *1/*1, *1/*2 and *2/*2 were 52.03%, 39.67%, and 8.30%, respectively; 47.97% of the individuals were found to carry the ALDH2*2 genotype, which was associated with a deficiency in the aldehyde dehydrogenase (ALDH2) enzyme activity. The frequency of the ALDH2*2 allele was lower than that previously reported in the Japanese population but higher than that reported in other Oriental populations.

Conclusions

The findings of this study have provided new information on the ALDH2 gene polymorphisms in the Hakka ethnic population residing in the Meizhou area of Guangdong Province, China, including an understanding of the origin of the atypical ALDH2*2 allele. Also, the study findings may be relevant to the primary care of patients in China.

Genetic Association and Gene-Gene Interaction Reveal Genetic Variations in ADH1B, GSTM1 and MnSOD Independently Confer Risk to Alcoholic Liver Diseases in India

Genetic susceptibility is an important modifier of clinical outcome and natural history of progression in Alcoholic liver disease (ALD). While the significance of ethnicity in this evolution is very clear, subtle inter-individual genetic variant(s) might be important and thus we investigated those in an Indian population. Fourteen markers were genotyped within two alcohol metabolism genes [Alcohol dehydrogenase (ADH) gene clusters (ADH1B and ADH1C) and Aldehyde dehydrogenase (ALDH2)], one microsomal ethanol oxidizing enzyme cytochrome p450 (CYP2E1) and three oxidative stress response (OSR) genes (MnSOD, GSTT1 and GSTM1) among 490 Bengali individuals (322 ALD and 168 control) from Eastern and North-Eastern India and validation was performed in a new cohort of 150 Bengali patients including 100 ALD and 50 advanced non-alcoholic steatohepatitis (NASH). Out of 14 genetic variants, carriage of 5 genotypes (rs2066701CC in ADH1B, rs1693425TT in ADH1C, rs4880TT in MnSOD and GSTT1/GSTM1 null, p-value <0.05) were noted significantly higher among ALD patients while inter or intra group gene-gene interaction analysis revealed that addition of risk genotype of any OSR gene enhanced the possibility of ALD synergistically. Multiple logistic regression analysis showed independent association of rs2066701CC, rs4880TT and GSTM1 null genotype with ALD while lower frequencies of those genotypes in advanced NASH patients further confirmed their causal relation to ALD. Thus these findings suggest that the three variants of ADH1C, MnSOD and GSTM1 can be used to identify individuals who are at high risk to develop ALD and may be helpful in proper management of Indian alcoholics.

Polymorphism of Alcohol Metabolizing Gene ADH3 Predisposes to Development of Alcoholic Pancreatitis in North Indian Population

Background and aim: Genetic factors regulating alcohol metabolism could predispose in developing alcoholic pancreatitis (ACP). Studies revealed that alcohol could be metabolized by both ways, oxidative and non-oxidative. The main oxidative pathway includes alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH), and cytochrome P450 enzyme. We investigated the association of polymorphisms in these enzymes with the alcoholic pancreatitis in the north Indian population.

Method: Patients with alcoholic pancreatitis (ACP; n = 72), tropical calcific pancreatitis (TCP; n = 75), alcoholic controls (AC; n = 40), and healthy controls (HC; n = 100) were included in the study. Blood samples were collected from the subjects in EDTA coated vials. DNA was extracted and genotyping for ADH3, ALDH2, and CYP2E1 was done by PCR-RFLP (polymerase chain reaction—restriction fragment length polymorphism). The products were analyzed by gel electrophoresis.

Result: The frequency distribution of ADH3^*1/^*1 genotype was significantly higher in ACP group (59.7%) compared with TCP (38.7%), HC (42%), and AC (37.5%) and was found to be associated with increased risk of alcoholic pancreatitis. There was no statistically significant difference between the frequency distribution of ADH3^*1/^*1, ADH3^*1/^*2, and ADH3^*2/^*2 genotypes between TCP and HC or healthy alcoholics. ALDH2 gene was monomorphic in our population, and the frequencies for CYP2E1 intron 6 Dra I polymorphism were comparable in all the four groups.

Conclusion: This study shows that carriers of ADH3^*1/^*1 individuals consuming alcohol are at higher risk for alcoholic pancreatitis than those with other genotypes such as ADH3^*1/^*2 and ADH3^*2/^*2.

Genetic variants of TNFα, IL10, IL1β, CTLA4 and TGFβ1 modulate the indices of alcohol-induced liver injury in East Indian population

Alcohol induced liver disease or alcoholic liver disease (ALD), a complex trait, encompasses a gamut of pathophysiological alterations in the liver due to continuous exposure to a toxic amount of alcohol (more than 80 g per day). Of all chronic heavy drinkers, only 15-20% develops hepatitis or cirrhosis concomitantly or in succession. Several studies revealed that inter-individual as well as inter-ethnic genetic variation is one of the major factors that predispose to ALD. The role of genetic factors in ALD has long been sought for in ethnically distinct population groups. ALD is fast emerging as an important cause of chronic liver disease in India; even in populations such as "Bengalis" who were "culturally immune" earlier. While the genetic involvement in the pathogenesis of ALD is being sought for in different races, the complex pathophysiology of ALD as well as the knowledge of population level diversity of the relevant alcohol metabolizing and inflammatory pathways mandates the need for well designed studies of genetic factors in ethnically distinct population groups. An array of cytokines plays a critical role as mediators of injury, inflammation, fibrosis and cirrhosis in ALD. We, therefore, studied the association of polymorphisms in five relevant cytokine genes with "clinically significant" ALD in an ethnic "Bengali" population in Eastern India. Compared with "alcoholic" controls without liver disease (n=110), TNFα -238AA genotype, IL1β -511CC genotype, TGFβ1 -509CC genotype and IL10 -592AA genotype were significantly overrepresented in ALD patients (n=181; OR=2.4 and 95% CI 1.2-5.5, P(genotype)=0.042, P(allelic)=0.008; OR=2.7 and 95% CI 1.2-5.9, P(genotype)=0.018, P(allelic)=0.023; OR=4.7 and 95% CI 1.7-13.1, P(genotype)=0.003, P(allelic)=0.014; and OR=2.2 and 95% CI 1.1-4.8, P(genotype)=0.04, P(allelic)=0.039 respectively). Moreover a cumulative genetic risk analysis revealed a significant trend for developing ALD with an increase in the number of risk alleles on IL10 and TGFβ1 loci among alcoholics. The risk genotype of IL1β and TGFβ1 also influences the total bilirubin, albumin and alanine aminotransferase levels among alcoholic "Bengalis". The present study is the first case-control study from Eastern India that comprehensively identified polymorphic markers in TNFα, IL10, IL1β and TGFβ1 genes to be associated with ALD in the Bengali population, accentuating the significance of genetic factors in clinical expressions of ALD.

Substance use and addiction research in India

Substance use patterns are notorious for their ability to change over time. Both licit and illicit substance use cause serious public health problems and evidence for the same is now available in our country. National level prevalence has been calculated for many substances of abuse, but regional variations are quite evident. Rapid assessment surveys have facilitated the understanding of changing patterns of use. Substance use among women and children are increasing causes of concern. Preliminary neurobiological research has focused on identifying individuals at high risk for alcohol dependence. Clinical research in the area has focused primarily on alcohol and substance related comorbidity. There is disappointingly little research on pharmacological and psychosocial interventions. Course and outcome studies emphasize the need for better follow-up in this group. While lack of a comprehensive policy has been repeatedly highlighted and various suggestions made to address the range of problems caused by substance use, much remains to be done on the ground to prevent and address these problems. It is anticipated that substance related research publications in the Indian Journal of Psychiatry will increase following the journal having acquired an 'indexed' status.

Association of ADH1B and ALDH2 gene polymorphisms with alcohol dependence: a pilot study from India

Functional polymorphism in the genes encoding alcohol dehydrogenase (ADH) 1B and aldehyde dehydrogenase (ALDH) 2 are considered most important among several genetic determinants of alcohol dependence, a complex disorder. There is no report on the widely studied Arg47His and Glu487Lys polymorphisms from Indian alcohol-dependent populations. In this paper, we report, for the first time, allelic and genotypic frequencies of Arg47His and Glu487Lys single nucleotide polymorphisms (SNPs) in North Indian alcohol-dependent subjects. A total of 174 alcohol-dependent males, recruited using DSM IV criteria (American Psychiatric Association, 1994), were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. The results obtained from genetic analysis were correlated with clinical parameters using Student's t-test or Mann Whitney's U test. The highlight of the study findings was the uniquely high frequency of the ALDH2*2/*2 genotype (among alcohol-dependent subjects) being a risk-conferring factor for alcohol dependence.

Origin and dispersal of atypical aldehyde dehydrogenase ALDH2487Lys

The East Asian respond with a marked facial flushing and mild to moderate symptoms of intoxication after drinking the amounts of alcohol that has no detectable effect on European. The alcohol sensitivity in Orientals is due to a delayed oxidation of acetaldehyde by an atypical aldehyde dehydrogenase ALDH2487Lys, which is resulted from a structural mutation in gene ALDH2. The atypical ALDH2487Lys allele has been associated with various phenotypic statuses, such as protective against alcohol dependence and the risk of alcohol-related digestive tract cancers. Here, we have examined this SNP, adjacent four non-coding SNPs, and one downstream STRP on ALDH2 gene, in total of 1072 unrelated healthy individuals from 14 Chinese populations and 130 Indian individuals. Five major haplotypes based on five SNPs across the ALDH2 gene 40 kb were found in all East Asian populations. The frequencies of the ancestral haplotype GCCTG and the East Asian special haplotype GCCTA containing the atypical ALDH2487Lys allele were 44.8% and 14.9%, respectively. The frequency of the atypical ALDH2487Lys allele or the East Asian specific haplotype GCCTA is high in Yunnan, South coastal, east coastal of China, and decreased gradually toward inland China, West, Northwest and North China. Combined with demographic history in East Asian, our results showed that the presence of ALDH2487Lys allele in peripheral regions of China might be the results of historical migration events from China to these regions. The origin of ALDH2487Lys could be possibly traced back to ancient Pai-Yuei tribe in South China.