Polymorphism of alcohol dehydrogenase, alcohol and aldehyde dehydrogenase activities: implication in alcoholic cirrhosis in white patients. The French Group for Research on Alcohol and Liver

Genetic polymorphisms in alcohol dehydrogenase, aldehyde dehydrogenase and alcoholic chronic pancreatitis susceptibility: a meta-analysis

PURPOSE

This study was aimed to determine the relationship of alcohol-metabolizing enzymes ADH2, ADH3, and ALDH2 polymorphisms with the susceptibility to alcoholic chronic pancreatitis (ACP).

METHODS

Meta-analyses that evaluated the association of ADH2, ADH3, and ALDH2 variations with ACP were performed.

RESULTS

Eight case-control studies were selected for analysis. The overall data revealed a significant association of ADH2 polymorphism (OR=1.56, 95% CI=1.42-1.72, P=0.000 for dominant model; OR=1.63, 95% CI=1.55-1.71, P=0.000 for homozygote comparison model; OR=1.11, 95% CI=1.01-1.22, P=0.030 for allelic contrast model), ADH3 polymorphism (OR=0.95, 95% CI=0.86-1.06, P=0.389 for dominant; OR=0.64, 95% CI=0.44-0.93, P=0.020 for homozygote comparison; and OR=0.87, 95% CI=0.77-0.99, P=0.039 for allelic contrast model) and ALDH2 polymorphism (OR=0.57, 95% CI=0.40-0.81, P=0.002 for dominant; OR=0.50, 95% CI=0.23-1.08, P=0.079 for homozygote comparison; and OR=0.58, 95% CI=0.41-0.84, P=0.003 for allelic contrast model) with ACP risk. The subgroup analyses suggested that the variant ADH2*2/*2+*1/*2, ADH2*2/*2 genotype and ADH2*2 allele significantly increased ACP risk among Asian individuals; the variant ADH3*2/*2 genotype and ADH3*2 allele significantly decreased ACP risk among non-Asian individuals; and the variant ALDH2*2/*2+*1/*2 genotype and ALDH2*2 allele significantly decreased ACP risk among Asians.

CONCLUSIONS

ADH2, ADH3 and ALDH2 polymorphisms may be susceptibility facts of ACP, and it may be ethnic and race-dependent.

Further clarification of the contribution of the ADH1C gene to vulnerability of alcoholism and selected liver diseases

The alcohol dehydrogenase 1C (ADH1C) subunit is an important member of the alcohol dehydrogenase family, a set of genes that plays a major role in the catabolism of ethanol. Numerous association studies have provided compelling evidence that ADH1C gene variation (formerly ADH3) is associated with altered genetic susceptibility to alcoholism and alcohol-related liver disease, cirrhosis, or pancreatitis. However, the results have been inconsistent, partially, because each study involved a limited number of subjects, and some were underpowered. Using cumulative data over the past two decades, this meta-analysis (6,796 cases and 6,938 controls) considered samples of Asian, European, African, and Native American origins to examine whether the aggregate genotype provide statistically significant evidence of association. The results showed strong evidence of association between ADH1C Ile350Val (rs698, formerly ADH1C *1/*2) and alcohol dependence (AD) and abuse in the combined studies. The overall allelic (Val vs. Ile or *2 vs. *1) P value was 1 × 10(-8) and odds ratio (OR) was 1.51 (1.31, 1.73). The Asian populations produced stronger evidence of association with an allelic P value of 4 × 10(-33) [OR 2.14 (1.89, 2.43)] with no evidence of heterogeneity, and the dominant and recessive models revealed even stronger effect sizes. The strong evidence remained when stricter criteria and sub-group analyses were applied, while Asians always showed stronger associations than other populations. Our findings support that ADH1C Ile may lower the risk of AD and alcohol abuse as well as alcohol-related cirrhosis in pooled populations, with the strongest and most consistent effects in Asians.

The alcohol dehydrogenase 1C(rs698) genotype and breast cancer: a meta-analysis

Published data regarding the association between alcohol dehydrogenase (ADH) 1C genotypes and breast cancer risk show conflicting results. The authors performed this meta-analysis on 1969 patients and 2244 controls from 4 (including 7 study populations) related case-control studies to estimate the association between ADH1C(rs698) genotyping information and breast cancer risk. According to the 6 eligible populations, the odds ratios (ORs) and 95% confidence intervals (CIs) for breast cancer risk for ADH1C (1-2) versus ADH1C (2-2) , ADH1C (1-1) versus ADH1C (2-2) genotype, and ADH1C (1) versus ADH1C (2) were 1.16 (0.95-1.42), 1.17 (0.95-1.44), and 1.05 (0.96-1.16), respectively. The OR (95% CI) for ADH1C (1-1) + ADH1C (1-2) versus ADH1C (2-2) from the 7 study populations was 1.14 (0.96-1.36). Meanwhile, genotypes of ADH1C (1-1) + ADH1C (1-2) increased the risk of breast cancer in drinkers (OR = 1.35; 95% CI = 1.03-1.76). This meta-analysis suggested that the ADH1C (1) allele might modestly influence the effect of alcohol on breast cancer but is not an independent risk factor for breast cancer. However, more restricted prospective studies are needed.

Alcohol abuse and related factors in Asia

Alcohol problems are a global issue, and the nature of alcohol abuse is very complicated. The susceptibility to alcohol abuse varies greatly from one individual to another and also from one nation to another, depending on the availability of alcohol, a country's regulation related to alcohol, a country's cultural background, religious tradition and its economics. Alcohol dependence is also a complicated disease process. The prevalence of alcohol dependence also varies greatly from one ethnic group to another. Asia is the world's largest and most populous continent. The natural disasters, religious conflicts as well as political disputes cause people lack of opportunity in many countries. People in this region do not consume more alcohol than the people in the rest of the world. The prevalence of alcohol dependence is not as high as is seen in other regions. In Asia, not only socio-economic factors, but also biological factors influence drinking behaviour. Findings of functional genetic polymorphism of the major alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) have led to the suggestion that this enzyme system may possibly play a diverse but critical role in alcohol dependence and in the alcohol-related disease process in the different ethnic groups. This paper reviews alcohol problems and related factors. Their management and prevention strategy are discussed.

Alcohol-metabolizing enzyme gene polymorphisms and alcohol chronic pancreatitis among Polish individuals

BACKGROUND AND AIMS

Chronic pancreatitis develops in 5-10% of alcohol addicts. In developed societies, alcohol is the cause of chronic pancreatitis in at least 70-80% of cases. The genetic polymorphism of enzymes involved in alcohol metabolism is relevant in the etiopathogenesis of chronic pancreatitis. The aim of the study was to find the ADH, ALDH2 and CYP2E1 alleles and genotypes in the Polish population that are likely to be responsible for higher susceptibility to chronic alcohol pancreatitis.

MATERIAL AND METHODS

We determined the allele and genotype of ADH2, ADH3, ALDH2 and CYP2E1 in 141 subjects: 44 with alcohol chronic pancreatitis (ACP), 43 healthy alcoholics and 54 healthy non-drinkers as the controls. Genotyping was performed using PCR-RELP methods on white cell DNA.

RESULTS

ADH2*1, ADH3*1 alleles and ADH2*1/*1, ADH3*1/*1 genotypes were statistically more frequent among the patients with ACP than among the controls. The ADH3*2/*2 genotype was more frequent among "healthy alcoholics" and in the controls than among those with ACP. In the studied group, only the ALDH2*1 allele was detected, all patients were ALDH2*1/*1 homozygotic. Differences in the CYP2E1 allele and genotype distribution in the examined groups were not significant.

CONCLUSION

In the Polish population examined, ADH3*1 and ADH2*1 alleles may be risk factors for the development of alcoholism. The ADH3*2/*2 genotype may confer protection against ACP. CYP2E1 gene polymorphism is not related to alcoholism and ACP. The Polish population examined is ALDH2*1/*1 homozygotic.

Alcohol dehydrogenase and aldehyde dehydrogenase gene polymorphism in alcohol liver cirrhosis and alcohol chronic pancreatitis among Polish individuals

OBJECTIVE

To investigate the effects of ADH and ALDH gene polymorphism on the development of alcoholism, alcohol liver cirrhosis and alcohol chronic pancreatitis among Polish individuals.

MATERIAL AND METHODS

We determined the allele and genotype of ADH2, ADH3 and ALDH2 in 198 subjects: 57 with alcohol cirrhosis, 44 with alcohol chronic pancreatitis and 43 "healthy alcoholics"; 54 healthy non-drinkers served as controls. Genotyping was performed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method on white cell DNA.

RESULTS

In the population examined the ADH2*1 allele frequency was 97.97%. The tests did not show the ADH2*3 allele. The ADH3*1 allele frequency was 57.07%. The ADH2*1 and the ADH3*1 alleles were statistically more common among patients who abuse alcohol in comparison with the controls. The ADH2*2 allele was not detected in any of the patients with chronic alcohol pancreatitis. The ADH2*1/*1 and the ADH3*1/*1 genotypes were statistically significantly more common among the patients who abuse alcohol than in the control group. All patients were ALDH2*1/*1 homozygotic. Patients with the ADH3*1 allele and the ADH3*1/*1 genotype started to abuse alcohol significantly earlier in comparison to the patients with the ADH3*2 allele and the ADH3*2 /*2 genotype.

CONCLUSIONS

In the Polish population examined, the ADH3*1 allele and the ADH3*1/*1 genotype are conducive to the development of alcoholism, alcohol liver cirrhosis and alcohol chronic pancreatitis. However, the ADH2*2 allele is likely to protect against these conditions. Genetic polymorphism of ALDH2 shows no correlation with alcohol addiction or alcohol cirrhosis and alcohol chronic pancreatitis. The ADH3*1 allele and the ADH3*1/*1 genotype are conducive to alcohol abuse starting at a younger age.

Overview of the role of alcohol dehydrogenase and aldehyde dehydrogenase and their variants in the genesis of alcohol-related pathology

Alcohol dehydrogenase (ADH) and mitochondrial aldehyde dehydrogenase (ALDH2) are responsible for metabolizing the bulk of ethanol consumed as part of the diet and their activities contribute to the rate of ethanol elimination from the blood. They are expressed at highest levels in liver, but at lower levels in many tissues. This pathway probably evolved as a detoxification mechanism for environmental alcohols. However, with the consumption of large amounts of ethanol, the oxidation of ethanol can become a major energy source and, particularly in the liver, interferes with the metabolism of other nutrients. Polymorphic variants of the genes for these enzymes encode enzymes with altered kinetic properties. The pathophysiological effects of these variants may be mediated by accumulation of acetaldehyde; high-activity ADH variants are predicted to increase the rate of acetaldehyde generation, while the low-activity ALDH2 variant is associated with an inability to metabolize this compound. The effects of acetaldehyde may be expressed either in the cells generating it, or by delivery of acetaldehyde to various tissues by the bloodstream or even saliva. Inheritance of the high-activity ADH β2, encoded by theADH2*2gene, and the inactiveALDH2*2gene product have been conclusively associated with reduced risk of alcoholism. This association is influenced by gene–environment interactions, such as religion and national origin. The variants have also been studied for association with alcoholic liver disease, cancer, fetal alcohol syndrome, CVD, gout, asthma and clearance of xenobiotics. The strongest correlations found to date have been those between theALDH2*2allele and cancers of the oro-pharynx and oesophagus. It will be important to replicate other interesting associations between these variants and other cancers and heart disease, and to determine the biochemical mechanisms underlying the associations.

-238 G>A polymorphism of tumor necrosis factor alpha gene (TNFA) is associated with alcoholic liver cirrhosis in alcoholic Spanish men

BACKGROUND

The tumor necrosis factor alpha gene (TNFA) has been recently associated to alcoholic steatohepatitis. We have analyzed the distribution of genotypes and alleles of two polymorphisms at positions -238 and -308 in the promoter region of the TNFA gene in a Spanish male population of alcoholics with and without alcoholic liver cirrhosis.

METHODS

149 male alcoholics (84 without alcoholic liver disease, and 65 with alcoholic liver cirrhosis) and 90 control subjects were included. Genotyping was done by polymerase chain reaction and digestion with restriction enzymes.

RESULTS

No significant differences in the distribution of genotypes and alleles of the -308 TNFA gene polymorphism were observed between alcoholics and non-alcoholics, or between alcoholics with liver cirrhosis and those without liver disease. However, we found an association between the -238 TNFA polymorphism and alcoholic liver cirrhosis; the frequency of the heterozygous genotype being significantly higher in alcoholics with cirrhosis than in those without liver damage.

CONCLUSION

The -238 TNFA-A allele is associated with a higher risk to develop alcoholic liver cirrhosis. This polymorphism could be considered as a genetic factors that confer predisposition to suffer liver cirrhosis in the alcoholic population of Castile and León.

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

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

INTERLEUKIN-1 GENE CLUSTER POLYMORPHISMS AND ALCOHOLISM IN SPANISH MEN

AIMS

In an attempt to explain differences in susceptibility to alcoholism and alcohol liver disease (ALD), different genes have been analysed, among them those encoding inflammatory cytokines. Thus, it has been reported recently that both the interleukin 1 receptor antagonist (IL1RN) and the IL1beta (IL1B) genes may influence the risk of ALD in Japanese alcoholics. We analysed the distribution of single nucleotide polymorphisms (SNPs) located in the IL1A, IL1B, IL1R1 and IL1RN genes in alcoholic and non-alcoholic Spanish subjects.

METHODS

DNA samples were obtained from 139 male alcoholics, 78 of whom were diagnosed as alcohol dependent (32 patients with liver cirrhosis and 46 without ALD) and 61 as alcohol abusers (25 with liver cirrhosis and 36 without ALD). As a control, we studied 81 age- and sex-matched healthy volunteers.

RESULTS

Alleles -511 IL1B*1 and IL1RN*1 were represented more in alcoholic patients than in the control group. We did not find any association of alcoholism or ALD with polymorphisms in the IL1A and IL1R1 genes.

CONCLUSIONS

We conclude that the proteins encoded by the IL1RN and IL1B genes may be involved in susceptibility to alcoholism in Spanish men, probably through a different pathway from that involved in the regulation of the inflammatory response.

Metabolism of alcohol

Most tissues of the body contain enzymes capable of ethanol oxidation or nonoxidative metabolism, but significant activity occurs only in the liver and, to a lesser extent, in the stomach. Hence, medical consequences are predominant in these organs. In the liver, ethanol oxidation generates an excess of reducing equivalents, primarily as NADH, causing hepatotoxicity. An additional system, containing cytochromes P-450 inducible by chronic alcohol feeding, was demonstrated in liver microsomes and found to be a major cause of hepatotoxicity.

Genetic polymorphisms of ADH2, ADH3, CYP4502E1 Dra-I and Pst-I, and ALDH2 in Spanish men: lack of association with alcoholism and alcoholic liver disease

BACKGROUND/AIMS

The relationship between polymorphisms at the alcohol dehydrogenase 2 (ADH(2)), ADH(3), CYP(450)2E1 and aldehyde dehydrogenase 2 (ALDH(2)) loci and the individual predisposition to alcoholism and alcoholic liver disease in Caucasians is controversial.

METHODS

We determined the genotypes of ADH(2), ADH(3), CYP(450)2E1 (Pst-I and Dra-I) and ALDH(2) in 519 male Spaniards: 264 alcoholic subjects (47 without liver disease, 118 with non-cirrhotic liver disease and 99 with cirrhosis) and 255 non-alcoholic subjects (64 healthy controls, 110 with non-cirrhotic non-alcoholic liver disease and 81 with cirrhosis unrelated to alcohol). Genotyping was performed using PCR-RFLP methods on white cell DNA.

RESULTS

The distribution of the allelic variants (allele *1 and allele *2) in the whole subjects analyzed was: ADH(2) 93.1% and 6.9%; ADH(3) 55.7 and 44.3%; CYP(450)2E1 Dra-I 11.2 and 88.8%; CYP(450)2E1 Pst-I 96.2 and 3.8% and ALDH2 100 and 0%, respectively. No differences were observed in the allelic distributions of the alcoholic and non-alcoholic subjects for the loci examined. Allele distribution in alcoholics with no liver disease, with alcoholic steatosis or hepatitis, and with cirrhosis was also similar.

CONCLUSIONS

ADH(2), ADH(3), and CYP(450)2E1 Pst-I and Dra-I genetic variations are not related to alcoholism or susceptibility to alcoholic liver disease in our male population. ALDH(2) locus is monomorphic.

A global perspective on genetic variation at the ADH genes reveals unusual patterns of linkage disequilibrium and diversity

Variants of different Class I alcohol dehydrogenase (ADH) genes have been shown to be associated with an effect that is protective against alcoholism. Previous work from our laboratory has shown that the two sites showing the association are in linkage disequilibrium and has identified the ADH1B Arg47His site as causative, with the ADH1C Ile349Val site showing association only because of the disequilibrium. Here, we describe an initial study of the nature of linkage disequilibrium and genetic variation, in population samples from different regions of the world, in a larger segment of the ADH cluster (including the three Class I ADH genes and ADH7). Linkage disequilibrium across approximately 40 kb of the Class I ADH cluster is moderate to strong in all population samples that we studied. We observed nominally significant pairwise linkage disequilibrium, in some populations, between the ADH7 site and some Class I ADH sites, at moderate values and at a molecular distance as great as 100 kb. Our data indicate (1) that most ADH-alcoholism association studies have failed to consider many sites in the ADH cluster that may harbor etiologically significant alleles and (2) that the relevance of the various ADH sites will be population dependent. Some individual sites in the Class I ADH cluster show Fst values that are among the highest seen among several dozen unlinked sites that were studied in the same subset of populations. The high Fst values can be attributed to the discrepant frequencies of specific alleles in eastern Asia relative to those in other regions of the world. These alleles are part of a single haplotype that exists at high (>65%) frequency only in the eastern-Asian samples. It seems unlikely that this haplotype, which is rare or unobserved in other populations, reached such high frequency because of random genetic drift alone.

ALCOHOL: its metabolism and interaction with nutrients

In the past, alcoholic liver disease was attributed exclusively to dietary deficiencies, but experimental and judicious clinical studies have now established alcohol's hepatotoxicity. Despite an adequate diet, it can contribute to the entire spectrum of liver diseases, mainly by generating oxidative stress through its microsomal metabolism via cytochrome P4502E1 (CYP2E1). It also interferes with nutrient activation, resulting in changes in nutritional requirements. This is exemplified by methionine, one of the essential amino acids for humans, which needs to be activated to S-adenosylmethionine (SAMe), a process impaired by liver disease. Thus, SAMe rather than methionine is the compound that must be supplemented in the presence of significant liver disease. In baboons, SAMe attenuated mitochondrial lesions and replenished glutathione; it also significantly reduced mortality in patients with Child A or B cirrhosis. Similarly, decreased phosphatidylethanolamine methyltransferase activity is associated with alcoholic liver disease, resulting in phosphatidylcholine depletion and serious consequences for the integrity of membranes. This can be offset by polyenylphosphatidylcholine (PPC), a mixture of polyunsaturated phosphatidylcholines comprising dilinoleoylphosphatidylcholine (DLPC), which has high bioavailability. PPC (and DLPC) opposes major toxic effects of alcohol, with down-regulation of CYP2E1 and reduction of oxidative stress, deactivation of hepatic stellate cells, and increased collagenase activity, which in baboons, results in prevention of ethanol-induced septal fibrosis and cirrhosis. Corresponding clinical trials are ongoing.

Risk factors for alcoholic liver disease

Abstract Alcoholic liver disease (ALD) is still a frequent disorder, even though its incidence appears to be decreasing. In spite of intense investigation, the precise mechanisms leading to ALD are still imprecisely known. This is due in part to the lack of a reliable animal model; in part to the difficulty of obtaining clinical data of adequate sample size and derived from unblased populations and finally from the lack of uniformity of the criteria used to define ALD. This paper will review what is known of the various pieces of this puzzle, with particular emphasis not only on the total amount of alcohol consumed, but also on drinking patterns and type of alcoholic beverage ingested. The other potential factors such as age, gender, genetic background, nutritional status, occupational hazards and viral diseases (especially HCV infection) will be touched upon.

Genetic polymorphisms of interleukin-1beta in association with the development of alcoholic liver disease in Japanese patients

OBJECTIVE

Cytokine interleukin-1beta plays a central role in the inflammation process. Serum levels of IL-1beta are elevated in patients with alcoholic liver disease (ALD), especially in those with cirrhosis and alcoholic hepatitis. Recently, the presence of genetic polymorphisms of this cytokine was confirmed. The aim of this study was to determine whether IL-1beta polymorphisms are associated with the development of ALD.

METHODS

We examined the frequency of two polymorphisms in the IL-1beta gene located in promoter -511 and exon 5 +3953 locus by restriction fragment length polymorphisms in 142 male patients with ALD, 30 heavy drinkers without ALD, and 218 healthy controls.

RESULTS

The carriers of -511 IL-1beta allele 2 were present significantly more often in patients with alcoholic cirrhosis than in those with noncirrhotic ALD (p = 0.026), heavy drinkers without ALD (p = 0.001), and healthy controls (p = 0.032). The frequencies of allele 2 and heterozygotes of +3953 polymorphism were both significantly higher in heavy drinkers without ALD than in patients with ALD (allele, p = 0.030; genotype, p = 0.027) and healthy controls (allele, p = 0.047; genotype, p = 0.043). The haplotype, IL-1beta -511 allele 2/+3953 allele 1 was associated with the development of alcoholic cirrhosis (p < 0.05).

CONCLUSIONS

These results suggest that IL-1beta polymorphisms may be related to the development of ALD in Japanese alcoholics.

Genetic polymorphism of alcohol dehydrogenase in europeans: the ADH2*2 allele decreases the risk for alcoholism and is associated with ADH3*1

Polymorphism at the ADH2 and ADH3 loci of alcohol dehydrogenase (ADH) has been shown to have an effect on the predisposition to alcoholism in Asian individuals. However, the results are not conclusive for white individuals. We have analyzed the ADH genotype of 876 white individuals from Spain (n = 251), France (n = 160), Germany (n = 184), Sweden (n = 88), and Poland (n = 193). Peripheral blood samples from healthy controls and groups of patients with viral cirrhosis and alcohol-induced cirrhosis, as well as alcoholics with no liver disease, were collected on filter paper. Genotyping of the ADH2 and ADH3 loci was performed using polymerase chain reaction-restriction fragment length polymorphism methods on white cell DNA. In healthy controls, ADH2*2 frequencies ranged from 0% (France) to 5.4% (Spain), whereas ADH3*1 frequencies ranged from 47. 6% (Germany) to 62.5% (Sweden). Statistically significant differences were not found, however, between controls from different countries, nor between patients with alcoholism and/or liver disease. When all individuals were grouped in nonalcoholics (n = 451) and alcoholics (n = 425), ADH2*2 frequency was higher in nonalcoholics (3.8%) than in alcoholics (1.3%) (P =.0016), whereas the ADH3 alleles did not show differences. Linkage disequilibrium was found between ADH2 and ADH3, resulting in an association of the alleles ADH2*2 and ADH3*1, both coding for the most active enzymatic forms. In conclusion, the ADH2*2 allele decreases the risk for alcoholism, whereas the ADH2*2 and ADH3*1 alleles are found to be associated in the European population.

Association of polymorphism in the alcohol dehydrogenase 2 gene with alcohol-related organ injuries, especially liver cirrhosis

The class I hepatic alcohol dehydrogenases (ADHs) are primarily responsible for ethanol metabolism in humans. Genetic polymorphism at the ADH2 locus results in the inheritance of isozymes of strikingly different catalytic properties. In European and Caucasian American populations, β1, which is encoded by ADH2(1) , is the most common form of the enzyme, while β2, encoded by the ADH2(2) allele, is found primarily in Orientals. The β2β2 enzyme encoded by ADH2(2) /ADH2(2) is approximately 20 times more active in ethanol oxidation than the β1β1 enzyme. In vivo the kinetic differences of ADH2 isozymes may influence individual risk for the effects of ethanol. This article will review the role of polymorphisms at the ADH2 loci in genetic predisposition to alcoholism and alcohol-related organ injury, especially alcoholic cirrhosis.

Metabolism of ethanol and some associated adverse effects on the liver and the stomach

Current knowledge of alcohol oxidation and its effects on hepatic metabolism and its toxicity are summarized. This includes an evaluation of the relationship of the level of consumption to its interaction with nutrients (especially retinoids, carotenoids, and folate) and the development of various stages of liver disease. Ethanol metabolism in the stomach and its link to pathology and Helicobacter pylori is reviewed. Promising therapeutic approaches evolving from newly gained insight in the pathogenesis of medical complications of alcoholism are outlined. At present, the established approach for the prevention and treatment of alcoholism are outlined. At present, the established approach for the prevention and treatment of alcoholic liver injury is to control alcohol abuse, with the judicial application of selective antioxidant therapy, instituted at early stages, prior to the social or medical disintegration of the patient, and associated with antiinflammatory agents at the acute phase of alcoholic hepatitis. In addition, effective antifibrotic therapy may soon become available.

Fatty acid ethyl esters: short-term and long-term serum markers of ethanol intake

This review includes a description of short-term and long-term markers of ethanol intake and their clinical utility. The major portion of this report is a summary of studies on fatty acid ethyl ester, a new marker for monitoring both acute and chronic ethanol intake. With the markers described in the review, algorithms to assess recent ethanol intake, chronic ethanol intake, and end organ damage are included to provide a practical approach to the evaluation of the patient.

Polymorphism in the cytochrome P450 2E1 gene and the risk of alcoholic liver disease

BACKGROUND/AIMS

To study the genetic susceptibility to alcoholic liver disease, we investigated the association between genetic polymorphism in the cytochrome P450 2E1 gene and the occurrence of alcoholic liver disease.

METHODS

Four previously described restriction fragment length polymorphisms (RFLPs) in the cytochrome P 450 2E1 gene were analyzed by restriction endonuclease (Dra I, Msp I, Pst I and Rsa I) digestion of polymerase chain reaction amplified DNA segments. Polymorphisms in these loci were compared to the occurrence of fatty liver, alcoholic hepatitis and liver fibrosis in 319 males comprising total abstainers, moderate alcohol consumers and chronic alcoholics.

RESULTS

The allelic frequencies for each RFLP in this series were: 0.89 and 0.11 (Dra I), 0.98 and 0.02 (Msp I) and 0.99 and 0.01 (Pst I and Rsa I). The distribution of the alleles did not vary significantly between the different consumption groups. The allelic frequencies among patients with fatty liver, alcoholic hepatitis or liver fibrosis were not significantly different from the allelic frequencies among patients with normal liver histology. Comparison of different genotypes among moderate alcohol consumers (n = 43) or chronic alcoholics (n = 243) with or without liver disease showed no statistically significant associations. However, the rare polymorphic (d2) allele in the Dra I RFLP was found slightly more often among moderate consumers as well as alcoholics with alcoholic liver disease.

CONCLUSIONS

These results indicate that the Msp I, Pst I and Rsa I RFLPs were very rare in the Finnish population, suggesting at most minor contribution to the inherited susceptibility to alcoholic liver disease. Polymorphism in the Dra I locus was more common in this study population, but showed no statistically significant association with alcoholic liver disease.

Polymorphism in the cytochrome P450 2E1 gene and alcohol-induced disorders of human spermatogenesis

The association between alcohol-induced disorders of human spermatogenesis and four restriction fragment polymorphisms (DraI, MspI, PstI and RsaI) of the cytochrome P450 2E1 gene was investigated in an autopsy study on 254 men. Acquaintances were interviewed and the mean daily alcohol consumption of the subjects was calculated on the basis of the interviews. Spermatogenesis score and testicular morphology were assessed by light-microscopy, and cytochrome 2E1 polymorphic genotypes were determined using the polymerase chain reaction. Of the 204 heavy-drinking men, 42 (20.6%) men had normal spermatogenesis (p < 0.001, compared to moderate drinkers). Partial spermatogenic arrest was observed in 76 (37.3%) men and complete spermatogenic arrest in 79 (38.7%) men (p < 0.001, compared to moderate drinkers), whereas seven men (3.4%) had Sertoli cell only syndrome. The overall allelic frequencies for the common and rare polymorphic alleles were 0.98 and 0.02 (MspI) and 0.99 and 0.01 (PstI and RsaI), respectively. No associations between heterozygosity in the MspI, PstI or RsaI loci, or the allelic frequencies of common and rare alleles, and disorders of spermatogenesis were observed. The allelic frequencies for the common and rare polymorphic alleles in the DraI locus were 0.90 and 0.10, respectively. No significant difference was observed, either among moderate or heavy drinkers, in the frequency of the rare allele between men with disorders of spermatogenesis and those with normal spermatogenesis in the respective group, although men with disorders of spermatogenesis in general had a slightly lower frequency of the rare allele when compared to those with normal spermatogenesis. In conclusion, we were unable to demonstrate a significant association between any polymorphisms in the CYP2E1 gene and disorders of spermatogenesis. RsaI, MspI and PstI polymorphisms were extremely rare in our population and could thus possibly be excluded as reasons for genetic susceptibility to disorders of spermatogenesis in our series.

Divergence of ethanol and acetaldehyde kinetics and of the disulfiram-alcohol reaction between subjects with and without alcoholic liver disease

Despite standardization, marked interindividual variation in the severity of the disulfiram-alcohol reaction (DAR) has been observed. We studied the DAR in 51 consecutive alcoholics with (n = 16) and without (n = 35) significant alcoholic liver disease. Clinical signs of the DAR were much weaker in the patients with compared with those patients without liver disease. Because acetaldehyde is thought to be the main cause of the DAR, we studied ethanol and acetaldehyde kinetics in 13 patients (6 females, 7 males) with alcoholic liver disease (documented by biopsy, clinical and/or radiological findings, and by quantitative liver function) [galactose elimination capacity (GEC) 4.2 +/- SD 1.0 mg/min/kg; aminopyrine breath test (ABT) 0.14 +/- 0.10% dose x kg/mmol CO2] and 13 age- and sex-matched controls (alcoholics without significant liver disease, GEC 7.1 +/- 0.7; ABT 0.81 +/- 0.35). Clinical signs of acetaldehyde toxicity during the DAR (flush, nausea, tachycardia, and blood pressure drop) were absent in alcoholic liver disease, but clearly evident in controls. Blood ethanol kinetics were similar in both groups, Cmax and area under the concentration-time curve (AUC) being 6.27 +/- 1.82 and 368.9 +/- 72.9 mmol x min/liter in alcoholic liver disease, and 6.62 +/- 1.71 and 377.6 +/- 124.5 in controls, respectively. In contrast, there was a strong (p < 0.001) difference in Cmax and AUC of acetaldehyde, respective values being 33.46 +/- 21.52 and 1463.8 +/- 762.5 mumol x min/liter in alcoholic liver disease, and 110.87 +/- 56.00 and 4162.0 +/- 2424.6 in controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular biological aspects of alcohol-induced liver disease

Molecular biological investigations have become a predominant methodology applied to the study of alcohol-induced liver disease. The enzymatic pathways responsible for ethanol metabolism, and their genetic as well as environmental control, have become the focus of detailed investigation. More recently, the significance of cytokines in the pathogenesis of alcohol-induced liver disease has also become a major area of speculation. This review focuses on the advances made in studies of two important enzymes responsible for alcohol metabolism, alcohol dehydrogenase and aldehyde dehydrogenase, as well as the investigation of the proinflammatory and profibrogenic cytokines involved in the process of hepatic fibrogenesis. The quality and quantity of new discoveries made in the field of alcohol-induced liver disease is impressive, especially when one realizes that molecular biological approaches have been employed in this area for only 15 years. However, in most cases the studies have been predominantly descriptive, with little direct relevance to the therapeutics of alcoholism and alcohol-induced organ injury. Because the groundwork has been laid, one hopes that the next 15 years will rectify this failure.

Genetic aspects and risk factors in alcoholism and alcoholic liver disease

There is a great deal of evidence for genetic predisposition to alcoholism; considerably less is known regarding predisposition to alcoholic liver disease. The specific genes involved in either disorder are not well understood, although the enzymes of alcohol metabolism appear to play some role. It will be interesting to determine whether genetic factors that alter the expression of these enzymes, in addition to altering the kinetics of the enzymes, could modify responses to drinking. Work in the next few years will include determination of which responses to alcohol are indeed genetically influenced in twin studies, testing additional candidate genes for alcohol-related traits in populations and families, as well as the application of genomic mapping methodologies to alcoholic pedigrees. The latter strategy will be integrated into the larger number of studies that will grow from the Human Genome Project. Animal studies with selectively bred lines of rodents that differ in voluntary alcohol consumption will lead the way to define the neuronal and behavioral substrates responsible for differences in alcohol-drinking behavior. The use of the quantitative trait locus (QTL) mapping approach in F2 intercross between two inbred strains of rodents with opposite alcohol-response characteristics and in recombinant inbred strains derived from F2 intercross already has and will continue to help identify chromosomal locations of genes relevant to voluntary alcohol consumption. Perhaps in the future selective breeding of rodents and QTL mapping strategies can also be used to determine the biology and genetics of alcohol-induced liver injury.

Alcohol and the liver: 1994 update

This article reviews current concepts on the pathogenesis and treatment of alcoholic liver disease. It has been known that the hepatotoxicity of ethanol results from alcohol dehydrogenase-mediated excessive generation of hepatic nicotinamide adenine dinucleotide, reduced form, and acetaldehyde. It is now recognized that acetaldehyde is also produced by an accessory (but inducible) microsomal pathway that additionally generates oxygen radicals and activates many xenobiotics to toxic metabolites, thereby explaining the increased vulnerability of heavy drinkers to industrial solvents, anesthetics, commonly used drugs, over-the-counter medications, and carcinogens. The contribution of gastric alcohol dehydrogenase to the first-pass metabolism of ethanol and alcohol-drug interactions is discussed. Roles for hepatitis C, cytokines, sex, genetics, and age are now emerging. Alcohol also alters the degradation of key nutrients, thereby promoting deficiencies as well as toxic interactions with vitamin A and beta carotene. Conversely, nutritional deficits may affect the toxicity of ethanol and acetaldehyde, as illustrated by the depletion in glutathione, ameliorated by S-adenosyl-L-methionine. Other "supernutrients" include polyunsaturated lecithin, shown to correct the alcohol-induced hepatic phosphatidylcholine depletion and to prevent alcoholic cirrhosis in nonhuman primates. Thus, a better understanding of the pathology induced by ethanol is now generating improved prospects for therapy.

Polymorphism of alcohol and aldehyde dehydrogenase genes and alcoholic cirrhosis in Chinese patients

Liver alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH), the principal enzymes responsible for the oxidation of ethanol, are polymorphic at the ADH2, ADH3 and ALDH2 loci in human beings. Our previous studies have shown that, compared with nonalcoholic individuals, Chinese alcoholic patients without liver disease had significantly lower frequencies of the ADH2*2 and ADH3*1 alleles, which encode high maximum velocity beta 2- and gamma 1-ADH subunits, respectively, as well as a lower frequency of the ALDH2*2 allele, which encodes an enzymatically inactive subunit. The data strongly suggest that genetic variation in both ADH and ALDH may influence drinking behavior and the risk of alcoholism developing through acetaldehyde formation. To further investigate the possible role of acetaldehyde in the pathogenesis of alcoholic liver disease, we determined the ADH and ALDH genotype frequencies in patients with alcohol-related cirrhosis (n = 27), viral hepatitis-related cirrhosis (n = 29) and gastric and duodenal ulcer without relevance to alcohol (n = 30). We developed a new restriction fragment length polymorphism method to genotype the mutant and normal ALDH2 alleles by using polymerase chain reaction-directed mutagenesis, which proved to be simpler and faster than the conventional detection methods that use hybridization with allele-specific oligonucleotide probes. We found that the frequencies of the alleles ADH2*2 (57%), ADH3*1 (78%) and ALDH2*2 (9%) in the alcoholic cirrhotic patients were significantly lower than those in the healthy controls and in the patients with cirrhosis from viral hepatitis and with gastric and duodenal ulcer.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of caloric restriction on rodent drug and carcinogen metabolizing enzymes: implications for mutagenesis and cancer

Caloric restriction in rodents results in increased longevity and a decreased rate of spontaneous and chemically induced neoplasia. The low rates of spontaneous neoplasia and other pathologies have made calorically restricted rodents attractive for use in chronic bioassays. However, caloric restriction also alters hepatic drug metabolizing enzyme (DME) expression and so may also alter the biotransformation rates of test chemicals. These alterations in DME expression may be divided into two types: (1) those that are the direct result of caloric restriction itself and are detectable from shortly after the restriction is initiated; (2) those which are the result of pathological conditions that are delayed by caloric restriction. These latter alterations do not usually become apparent until late in the life of the organism. In rats, the largest direct effect of caloric restriction on liver DMEs is an apparent de-differentiation of sex-specific enzyme expression. This includes a 40-70% decrease in cytochrome P450 2C11 (CYP2C11) expression in males and a 20-30% reduction of corticosterone sulfotransferase activity in females. Changes in DME activities that occur late in life in calorically restricted rats include a stimulation of CYP2E1-dependent 4-nitrophenol hydroxylase activity and a delay in the disappearance of male-specific enzyme activities in senescent males. It is probable that altered DME expression is associated with altered metabolic activation of chemical carcinogens. For example the relative expression of hepatic CYP2C11 in ad libitum-fed or calorically restricted rats of different ages is closely correlated with the amount of genetic damage in 2-acetylaminofluorene- or aflatoxin B1-pretreated hepatocytes isolated from rats of the same age and caloric intake. This suggests that altered hepatic drug and carcinogen metabolism in calorically restricted rats can influence the carcinogenicity of test chemicals.

Chronic ethanol administration enhances retinoic acid and triiodothyronine receptor expression in mouse liver

Chronic alcoholism induces perturbations of storage and metabolization of retinol and related compounds. After 6 months of ethanol consumption we have observed in mouse liver an increased expression of Tri-iodothyronine receptors (TR) while the expression of retinoic acid (RA) receptors (RAR) was unaffected. After 10 months of alcoholization the TR expression was strongly increased and the RAR expression was also increased. At this time the activity of aldehyde dehydrogenase and that of alcohol dehydrogenase, two enzymes involved in biosynthesis of RA from retinol, were similar in the liver of alcoholized and pair-fed mice. Thus it can be hypothesized that (i) the change of RAR expression was, at least in part, the result of a change of TR expression (result in agreement with previous data), (ii) the increased expression of RAR could induce apoptosis and subsequently liver necrosis.

Alcohol and aldehyde dehydrogenase polymorphisms and alcoholism

The alcohol-flush reaction occurs in Asians who inherit the mutant ALDH2*2 allele that produces an inactive aldehyde dehydrogenase enzyme. In these individuals, high blood acetaldehyde levels are believed to be the cause of the unpleasant symptoms that follow drinking. We measured the alcohol elimination rates and intensity of flushing in Chinese subjects in whom the alcohol dehydrogenase ADH2 and ALDH2 genotypes were determined. We also correlated ADH2, ADH3, and ALDH2 genotypes with drinking behavior in 100 Chinese men. We discovered that ADH2*2 and ADH3*1, alleles that encode the high activity forms of alcohol dehydrogenase, as well as the mutant ALDH2*2 allele were less frequent in alcoholics than in controls. The presence of ALDH2*2 was associated with slower alcohol metabolism and the most intense flushing. In those homozygous for ALDH2*1, the presence of two ADH2*2 alleles correlated with slightly faster alcohol metabolism and more intense flushing, although a great deal of variability in the latter was noted.