Apparent monomorphism of ALDH2 in seven American Indian populations

A personalized medicine approach for Asian Americans with the aldehyde dehydrogenase 2*2 variant

Asian Americans are one of the fastest-growing populations in the United States. A relatively large subset of this population carries a unique loss-of-function point mutation in aldehyde dehydrogenase 2 (ALDH2), ALDH2*2. Found in approximately 560 million people of East Asian descent, ALDH2*2 reduces enzymatic activity by approximately 60% to 80% in heterozygotes. Furthermore, this variant is associated with a higher risk for several diseases affecting many organ systems, including a particularly high incidence relative to the general population of esophageal cancer, myocardial infarction, and osteoporosis. In this review, we discuss the pathophysiology associated with the ALDH2*2 variant, describe why this variant needs to be considered when selecting drug treatments, and suggest a personalized medicine approach for Asian American carriers of this variant. We also discuss future clinical and translational perspectives regarding ALDH2*2 research.

Association of ALDH2 polymorphism with sensitivity to acetaldehyde-induced micronuclei and facial flushing after alcohol intake

To investigate whether sensitivity to the induction of micronuclei by acetaldehyde is associated with genetic polymorphisms of the aldehyde dehydrogenase-2 (ALDH2) gene, cytokinesis-block micronucleus (CBMN) assays were performed on peripheral lymphocytes from 47 healthy human subjects exposed to acetaldehyde in vitro. Facial flushing following alcohol intake was analyzed to determine if it was correlated with ALDH2 gene polymorphisms. The frequencies of the ALDH2 genotypes ALDH2(1)/ALDH2(1), ALDH2(1)/ALDH2(2), and ALDH2(2)/ALDH2(2) were 66.0, 27.7, and 6.4%, respectively, in the 47 subjects. Therefore, 34% of the studied subjects carried the mutant allele ALDH2(2), which is associated with the lack of enzyme activity. The frequency of micronuclei induced by acetaldehyde increased in a dose-dependent manner with the largest increase seen in subjects that were homozygous for the ALDH2(2) allele. A significant association was observed between the ALDH2 genotype and alcohol-induced facial flushing. Average alcohol consumption of the study subjects was also associated with the ALDH2 genotype. The frequency of heavy drinking was significantly higher among subjects with the ALDH2(1)/ALDH2(1) genotype than among subjects with the ALDH2(2) allele (ALDH2(1)/ALDH2(2) and ALDH2(2)/ALDH2(2) genotypes). Alcohol-induced facial flushing was also associated with an increased frequency of micronuclei in lymphocytes treated with acetaldehyde. The results suggest that the ALDH2 genotype is significantly associated with acetaldehyde-induced micronuclei and alcohol-induced facial flushing.

Transcultural issues

Pharmacogenetics as a field of research is increasing the basis of knowledge on the use of psychotropics in different ethnic patient populations. This chapter summarizes current knowledge on the metabolism of anxiolytic agents with emphasis on pharmacogenetics and ethnic variations in drug responses.

Electroencephalographic responses to alcohol challenge in Native American Mission Indians

BACKGROUND

Native Americans have some of the highest rates of alcohol abuse and dependence, yet potential central nervous system risk factors responsible for the problem drinking seen in some tribes remain relatively unknown.

METHODS

Background electroencephalographic (EEG) variants and response to alcohol were investigated in 48 Native American Mission Indian men between 18 and 25 years old.

RESULTS

Subjects with 50% or greater Native American heritage had a significantly higher proportion of low-voltage EEG variants. Within this sample of Mission Indian men, however, a family history of alcohol dependence was associated with a greater incidence of high voltage alpha EEGs. Mission Indian men also evidenced a "less depressant, more stimulating" response to alcohol as quantified by less alcohol-induced reductions in alpha, greater EEG stability, and increased alcohol-induced beta activity.

CONCLUSIONS

These findings demonstrate that certain genetically regulated EEG variants that have been previously associated with risk for alcoholism in Caucasians may also be more common in these Mission Indian men. Additionally, EEG measures of response to alcohol do not provide support for the commonly held idea that Indians are more sensitive to the depressant effects of alcohol.

Acute reactions to alcohol

Where the experience of alcohol is unpleasant because of adverse reactions to small amounts, alcohol consumption is likely to be low and alcohol dependence rare. This is shown by many studies of Asian subjects who experience the alcohol flush reaction (AFR) due to inherited aldehyde dehydrogenase (ALDH) deficiency. Alcohol reactions are less common and on average less severe in non-Asian subjects, but they do occur and can affect alcohol consumption. Information about alcohol reactions and their consequences in Europeans is reviewed, and such reactions are compared with those caused by mitochondrial ALDH deficiency in Asians.

Alcohol elimination in Native American Mission Indians: an investigation of interindividual variation

The high prevalence of alcohol abuse and alcohol dependence among Native Americans may be mediated by unique environmental and genetic factors in this population. One factor that may influence the development of alcoholism is variability in alcohol metabolism. To determine factors that contribute to differences in alcohol elimination rates within a Native American population, this study evaluated healthy southern California Mission Indian men between the ages of 18 and 25 years. Each man drank a dose of alcohol, 0.56 g/kg of body weight as a 20% by volume solution, at approximately 9:00 AM after eating a low-fat breakfast and having fasted overnight. The drink was consumed within 7 min, and the concentrations of alcohol in blood were determined before and at 15, 30, 60, 90, 120, and 150 min after beverage ingestion. Rates of alcohol elimination were calculated from the pseudolinear slope of the blood alcohol versus time curve. The influences of estimated body water, recent drinking history, recent smoking history, polymorphism at the ADH2 and ADH3 loci, family history of alcoholism, and percentage Native American heritage on alcohol elimination rate were determined using multiple regression analyses. Estimated body water accounted for a significant proportion of the variance in alcohol elimination rate. There was also a nonsignificant trend for subjects with an ADH2*3 allele (n = 6) to have faster rates of alcohol elimination than those with ADH2*1 alleles only (n = 33). Given the high prevalence of alcoholism and alcohol-related health problems among Native Americans, the results from this study suggest that evaluation of alcohol metabolism and genotypes of the alcohol-metabolizing enzymes in Native American populations merits further study.

Mitochondrial aldehyde dehydrogenase polymorphism in Asian and American Indian populations: detection of new ALDH2 alleles

Genetic deficiency of the mitochondrial aldehyde dehydrogenase (ALDH2) is frequent in Asian peoples where it is an important factor negatively regulating drinking behavior. To obtain additional information on gene geography of known ALDH2 alleles, and look for new variants, ALDH2 genes were evaluated in a Chinese population from Taiwan, a Yakut population of Siberia, and in five North American Indian populations. A novel approach based on a single-strand conformation polymorphism assay, and polymerase chain reaction-directed mutagenesis was developed for genotyping. In the Taiwan Chinese population, the ALDH2(2) allele frequency was 0.319 +/- 0.025, and this allele was not detected in the Yakut population nor in the five North American Indian populations. However, a new allele, ALDH2(3), was detected in Pima Indians at a frequency of 0.044 +/- 0.022, and this allele was also observed in 1 of 49 Pueblo samples. ALDH2(3) is a silent transition 1464 G-->A, and it possibly has a wide distribution among North American Indians. A new subtype of the ALDH2(2) allele, designated as ALDH2(2Taiwan), was found in 1 of 174 Chinese from Taiwan. ALDH2(2Taiwan) is characterized by two G-->A transitions at bases 1486 and 1510, resulting in Glu-->Lys substitutions at both the 479 and 487 positions. Thus, this second nonconservative ALDH2 substitution occurs within the sequence of the already inactive ALDH2(2) allele.

Detection of aldehyde dehydrogenase deficiency in Chachi Indians, Ecuador

The activity of mitochondrial aldehyde dehydrogenase (ALDH2) was tested by isoelectric focusing of hair root extracts from 50 Chachi Indians (Ecuador). Quality of extracts and the intactness of cytoplasmic and mitochondrial enzymes were ascertained by assaying of phosphoglucomutase (PGM) and malate dehydrogenase (MDH) in the same extracts. Three of the 39 successfully assayed Chachi Indian samples showed virtual absence of the ALDH2 band on the isoelectropherogram, and the control enzymes were stained normally in these subjects. These data confirm the existence of a mitochondrial ALDH deficiency among South American Indians. The molecular origin of the ALDH2 deficiency in this population is unknown.