Pharmacogenetics of alcohol metabolism and alcoholism.

The pharmacogenetic differences among individuals in their capacity to metabolize ingested alcohol are possibly responsible for the large inter-individual and inter-ethnic variations observed in the outcome of alcohol use and misuse. Based on results of adoption, twin, and family studies it is now widely accepted that the vulnerability to alcoholism is determined by genetic factors as well as by environment. There is a constant search for biological markers and specific genes which could identify individuals genetically predisposed to alcohol abuse and alcoholism. Numerous 'candidate genes' for alcoholism have been suggested including the alcohol metabolizing enzymes, alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). Both ADH and ALDH exhibit genetic heterogeneity. An atypical form of ADH (ADH2), which contains a variant beta 2 subunit instead of the usual beta 1 subunit, differs substantially from the usual form in its kinetic properties and is found more frequently among the Japanese, Chinese and other Mongoloid populations than in Caucasoids and Negroids. A widely prevalent genetic polymorphism has been observed for ALDH; about 50% of Japanese and Chinese livers possess an inactive ALDH (ALDH2 isozyme) whereas none of the Caucasian or Negroid populations show this isozyme abnormality. These metabolic polymorphisms seem to contribute to differences in the in vivo elimination rate of ethanol and acetaldehyde, and may explain differences in alcohol-related behaviour and its disease outcome. Taken together, Orientals who possess an atypical ALDH2 gene are more sensitive to acute responses to alcohol, tend to be discouraged from drinking alcohol, and consequently are at lower risk of developing alcohol-related disorders. However, more work is needed to support these findings. Recent advances in molecular genetics have made it possible to analyze directly the human genome. This may help in a better understanding of the complex genetic and environmental factors in alcohol abuse by providing prospects for identification of gene loci which may be responsible for predisposition to, and protection from, alcoholism.

Population genetic comparisons among eight populations using allele frequency and sequence data from three microsatellite loci.

Eight different population samples (Moroccans, Ovambos, Papuans, Australian aborigines, Germans, Turks, Japanese and Chinese) were studied using the tetranucleotide short tandem repeat systems HumTHO1 (THO1), Hum VWFA31 (VWA) and HumACTBP2 (ACTBP2). Ten alleles were differentiated in THO1, 11 alleles in VWA and 28 alleles in ACTBP2. THO1 showed 1 bp deletions in the repeat region, VWA sequence and structure variations of the 4-bp repeat motif and ACTBP2 sequence, structure and length variations in the repeat array and deletions/insertions (1-6 bp) in the flanking regions. A phylogenetic tree was constructed (UPGMA method) leading to branches which grouped Germans and Turks, Japanese and Chinese, and Papuans and Australian aborigines.

Alkali myosin light chains in man are encoded by a multigene family that includes the adult skeletal muscle, the embryonic or atrial, and nonsarcomeric isoforms.

A set of cDNA clones coding for alkali myosin light chains (AMLC) was isolated from fetal human skeletal muscle. Nucleotide sequence analysis and RNA expression patterns of individual clones revealed related sequences corresponding to (i) fast fiber type MLC1 and MLC3; (ii) the embryonic MLC that is also expressed in fetal ventricle and adult atrium (MLCemb); and (iii) a nonsarcomeric MLC isoform that is found in all nonmuscle cell types and smooth muscle. The AMLC gene family in man comprises unique copies for MLC1, MLC3 and MLCemb, and multiple copies for the nonsarcomeric MLC genes. The gene coding for MLC1 and MLC3 is located on human chromosome 2.

Evidence for a signal peptide at the amino-terminal end of human mitochondrial aldehyde dehydrogenase.

A full-length cDNA clone coding for human mitochondrial aldehyde dehydrogenase (ALDH I) was isolated from a human fetal muscle cDNA library. Sequence analysis revealed structural similarities between the amino-terminal end of ALDH I and other known targeting sequences responsible for protein uptake into the mitochondria.

Hereditary ataxia and the sixth chromosome.

Possible linkage of the gene or genes for dominant hereditary ataxia and three genetic markers on the short arm of the sixth chromosome (HLA, properdin factor B [Bf], and glyoxalase I) was investigated in five families. Logarithmic odds (lod scores) were calculated for the linkages and found to be either inconclusive or in favor of nonlinkage. Caution is advised in the summing of lod scores for separate families because of the wide spectrum of clinical and anatomical manifestations of dominant hereditary ataxia. Three families with recessive hereditary ataxia were also studied. Identical haplotypes occurred in affected and unaffected siblings. It did not appear likely that the recessive genes of the parents were transmitted in linkage with the markers on the short arm of the sixth chromosome.

Detoxification of cyclophosphamide by human aldehyde dehydrogenase isozymes.

In in vitro studies, no turnover of aldophosphamide and mafosfamide was observed with the tumor-specific aldehyde dehydrogenase 3 isozyme (ALDH3) isolated from human stomach mucosa as well as from lung (A549) and pharynx (UMSCC2) carcinoma cell lines. Only the human liver cytosolic ALDH preparation (ALDH1) showed any significant oxidation of aldophosphamide and mafosfamide.

Platelet monoamine oxidase and erythrocyte catechol-o-methyltransferase activity in alcoholism and controlled abstinence.

This study substantiates previous reports that low platelet monoamine oxidase (MAO) activity is associated with alcoholism. Catechol-o-methyltransferase (COMT) activity in erythrocytes of alcoholics did not differ from that of controls. In 20 male alcoholics low platelet MAO activity was found during the first 3 days after hospitalization. The MAO activity increased in the next 2 weeks of abstinence and then tended to decrease again.

Studies on the change of electrophoretic mobility and the decay of catalytic activity of brain-type creatine kinase isoenzyme (CK-BB) following incubation at 37 degrees C.

Incubation of CK-BB in serum (1:3, v/v) at 37 degrees C for 3 h caused a change of its electrophoretic mobility and decay of its catalytic activity. Similar effects were observed following incubation in water. Incubation in saline somehow preserved the electrophoretic mobility but not the catalytic activity. No effect was noted when incubated at 4 degrees C for 3 h. Further study on the rate of decay revealed that the decay in albumin solution (1:50, v/v) is quite similar to that in serum. More dramatic decay was noted when incubated in water and less when incubated in saline. It was further shown that the higher the incubation temperature (4 degrees C, 25 degrees C or 37 degrees C) the faster the decay. The rate of decay of CK-MM was much slower in all conditions of incubation. Determination of isoenzyme activities by means of an immunoprecipitation method again demonstrated that CK-BB lost a great deal of its catalytic activity following incubation at 37 degrees C for 1 h, and hence falsification of the isoenzyme pattern.

Isolation of repetitive clones from human muscle cDNA library.

Human fetal muscle cDNA library was screened with a beta-myosin heavy chain gene fragment containing Alu sequences. Two cDNA clones AI and BII with 1.8 and 3 kb inserts respectively were chosen for further characterization by means of RNA and DNA hybridization procedures and sequencing. The clones appeared to contain repetitive sequences as well as single copy regions. They are actively transcribed in different stages of myogenic development but not in the liver. DNA sequence analysis of short stretches from both clones revealed no sequence homology to any other published DNA sequences.

Catechol-O-methyltransferase of erythrocytes in patients with endogenous psychoses.

A significant decrease in catechol-O-methyltransferase (COMT) activity of erythrocytes was found in both male and female schizophrenic patients, as well as in male patients with schizophreniform psychosis. Among control subjects, a sex difference in COMT activity of erythrocytes was found, with males showing significantly higher activity than females. It is suggested that a genetically determined deficiency of catecholamine degradative enzymes in the central nervous system or, alternatively, influences of nongenetic hormonal factors could be implicated in the findings of altered erythrocyte COMT activity reported.

Pharmacogenetics of alcohol sensitivity.

The metabolism of acetaldehyde has received considerable attention in the past few years due to its toxic effects and possible importance in pharmacogenetics. Recent studies have demonstrated rapid progress concerning the multiple molecular forms of ADH and ALDH and their genetic variants. The isozymes of ALDH may play an important role in the biological sensitivity to alcohol in certain ethnic groups and also in the pathogenesis of alcohol related organ damage. A protective effect of ALDH I deficiency against alcoholism seems to exist in Japanese.

Blood ethanol and acetaldehyde levels in Japanese alcoholics and controls.

Aldehyde dehydrogenase (ALDH) isozyme I deficiency in hair root samples from 105 healthy individuals and 72 alcoholics was determined using isoelectric focusing. From these individuals, 12 male alcoholics (2 with ALDH isozyme I deficiency and 10 normal) and 45 healthy controls (18 with ALDH isozyme I deficiency and 27 normal) were investigated for their blood ethanol and acetaldehyde levels by gas chromatography after an acute dose of alcohol (0.5 g ethanol/kg body wt.). Peak blood ethanol values of about 10 mmol/l were attained after 1 hour both in alcoholics and normal controls irrespective of their ALDH type. There was no significant difference in the blood ethanol level during the 5 hr post-drinking period in both the groups. Peak blood acetaldehyde concentration was significantly higher in healthy controls and alcoholics deficient in ALDH isozyme I after alcohol drinking (about 30 micro-mmol/l) than in individuals with normal ALDH isozyme I (3 micro-mmol/l). However, no significant difference in blood acetaldehyde was observed between alcoholics and controls.

Aldehyde dehydrogenase isozyme variation and alcoholism in Japan.

Aldehyde dehydrogenase (ALDH) isozyme composition in hair roots was determined using isoelectric focusing in 105 healthy individuals, 175 alcoholics, 86 schizophrenics and 47 drug dependents. The incidence of ALDH isozyme I deficiency in healthy populations in Japan was found to be about 40%. Among alcoholics, however, only 2.3% individuals had the isozyme deficiency. There was no difference between normal controls, schizophrenics and drug dependents regarding the incidence of ALDH isozyme I deficiency. These observations indicate a possible protective role of ALDH isozymes against alcoholism. The higher frequency of ALDH isozyme I deficiency in Japanese may explain why alcoholism in Japan has been less frequent than in European and North American countries. ALDH isozyme II was found in most of the tissues and erythrocytes. A higher frequency of individuals possessing lower ALDH activity in hemolysates was observed in alcoholics than that in controls. The activity of acid phosphatase was also reduced in alcoholics. Alcohol abuse might result in disturbed protein synthesis in the erythrocytes.

Comparative study of erythrocyte aldehyde dehydrogenase in alcoholics and control subjects.

Human erythrocyte aldehyde dehydrogenase (ALDH, EC 1.2.1.3) shows a single activity band on starch gel electrophoresis and isoelectric focusing in polyacrylamide gel (pI = 5.0-5.3). The erythrocyte enzyme is identical with the slower migrating, disulfiram-sensitive human liver ALDH isozyme II. Significantly decreased activity of erythrocyte ALDH was observed in chronic alcoholics when compared with healthy controls and non-alcoholic psychiatric and gastrointestinal patients. The measurement of ALDH in erythrocyte lysates may offer yet another sensitive and specific biochemical marker of alcoholism.

Human aldehyde dehydrogenases: their role in alcoholism.

This article surveys the state of our knowledge concerning the biochemical and genetic variations in aldehyde dehydrogenases (ALDHs) in humans and their role in alcohol sensitivity, alcohol drinking habits, and alcoholism. Variations in acetaldehyde metabolism via genetically determined polymorphisms in ALDH enzymes seem to play an important role in individual and racial differences in acute and chronic effects of alcohol drinking as well as towards vulnerability to organ damage after chronic alcohol abuse. Alcohol sensitivity and associated discomfort symptoms accompanying alcohol ingestion may be determinantal for the significantly low incidence of alcoholism among Japanese, Chinese and other Orientals of Mongoloid origin. An abnormal ALDH isozyme has been found to be widely prevalent among individuals of Mongoloid race, and is mainly responsible for the acute sensitivity to alcohol commonly observed in this race. Persons sensitive to alcohol by virtue of their genetically controlled ALDH isozyme deficiency may be discouraged from drinking large amounts of alcohol in their daily life due to the initial adverse reaction experienced after drinking alcohol, and thus are protected against alcoholism.

Aldehyde dehydrogenase polymorphism and alcohol metabolism in alcoholics.

Significant differences in the incidence of aldehyde dehydrogenase isozyme I deficiency were observed between healthy controls and alcoholics in Japan. Only about 5% of alcoholics were found deficient as compared to about 42% in the normal healthy population. Blood acetaldehyde level after alcohol drinking was also found significantly higher in deficient subjects than in individuals without deficiency. Among alcoholics, deficient subjects showed relatively less elevated blood acetaldehyde levels. When two districts in Japan were compared, per capita alcohol consumption correlated with the frequency of isozyme deficiency. Higher percentage of aldehyde dehydrogenase isozyme deficiency was associated with lower per capita alcohol consumption. Thus, individuals deficient in aldehyde dehydrogenase isozyme may consume less alcohol.

Human brain aldehyde dehydrogenase: activity with DOPAL and isozyme distribution.

Aldehyde dehydrogenase (ALDH, EC 1.2.1.3), has been shown to be the most important enzyme for DOPAL metabolism in human brain (Agarwal et al.). In the present investigation cerebellum, corpus striatum and pons showed the highest ALDH activity. Most of the enzyme activity was found in the mitochondrial and microsomal fractions. Two activity bands on IEF gels and dual Km values indicate the presence of two distinct isozymes in all the fractions. Two cerebella from alcoholics yielded the same results as the control group regarding their total ALDH activity, subcellular distribution pattern and protein content. The presence of DOPAC (acid metabolite of DOPAL), pargyline, pyrazole or ethanol in the assay mixture did not alter the ALDH activity significantly.

Population genetic and family studies on aldehyde dehydrogenase deficiency and alcohol sensitivity.

Population genetic studies on the prevalence of aldehyde dehydrogenase isozyme I (ALDH I) deficiency in various Caucasian, Oriental, African, and American Indian subjects were carried out using hair roots as peripheral source of the enzyme activity. While a very high percentage of Orientals with Mongoloid origin were found deficient in ALDH I activity, no deficiency was detected in Caucasian and African populations. Native American Indians showed a relatively low incidence of ALDH I deficiency. A genetic model based on the phenotype determination using antisera against purified human liver ALDH I is proposed. Pedigree analysis of Japanese families suggests an autosomal codominant mode of inheritance.

Quantitative and qualitative biochemical parameters for alcohol abuse.

Blood from alcoholics, non-alcoholic patients and healthy controls were analyzed for various biochemical markers. Follow-up measurements were made during about 3 months of abstention. While a gradual increase in aldehyde dehydrogenase activity (ALDH) in red cell was noted in alcoholic patients serum alpha 1-acid glycoprotein (AAG) values returned to normal range within 8 weeks during abstinence. An additional minor band for alpha 1-antitrypsin (AAT) was observed after isoelectric focusing of sera from alcoholics; this band disappeared after 3 weeks of abstinence. However, no such unusual AAT band was found in non-alcoholic patients with liver disorders.

Basis of aldehyde dehydrogenase deficiency in Orientals: immunochemical studies.

While most Caucasians have two main isozymes of liver aldehyde dehydrogenase, in about 50% of Orientals the ALDH I isozyme is missing. This isozyme, which has a faster electrophoretic mobility, is predominantly present in mitochondria and has a relatively low Km for acetaldehyde. The inherent deficiency of ALDH I is responsible for the impaired acetaldehyde oxidation leading to facial flushing and other cardiovascular symptoms of alcohol sensitivity commonly observed in Japanese and Chinese. Antibodies raised against apparently homogeneous liver ALDH I and ALDH II isozymes did not show an immunological similarity between the two isozymes which do not share common subunits. While erythrocyte ALDH II is also immunologically distinct from hepatic ALDH I, it showed an immunological similarity with hepatic ALDH II. On isoelectric focusing in agarose gel followed by immunoelectrophoresis, at least 4 components with an anti-ALDH I antibody were detected in extracts from Caucasian and Oriental livers. In Japanese livers deficient in ALDH I activity, the prominent ALDH component was missing. Apparently, more than one gene is responsible for the synthesis of ALDH isozymes reacting with an antibody against ALDH I. A deletion in one of the genes may be responsible for the loss of ALDH I enzyme activity and altered antigenic properties. However, at this stage, a point mutation in a structural gene coding for ALDH I resulting in a defective protein with altered electrophoretic and enzymatic properties is not ruled out.