Holly R. Thomasson

Alcohol and aldehyde dehydrogenase polymorphisms and alcoholism

The alcohol-flush reaction occurs in Asians who inherit the mutantALDH2*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 dehydrogenaseADH2 andALDH2 genotypes were determined. We also correlatedADH2, ADH3, andALDH2 genotypes with drinking behavior in 100 Chinese men. We discovered thatADH2*2 andADH3*1, alleles that encode the high activity forms of alcohol dehydrogenase, as well as the mutantALDH2*2 allele were less frequent in alcoholics than in controls. The presence ofALDH2*2 was associated with slower alcohol metabolism and the most intense flushing. In those homozygous forALDH2*1, the presence of twoADH2*2 alleles correlated with slightly faster alcohol metabolism and more intense flushing, although a great deal of variability in the latter was noted.

Alcohol Metabolism in Asian-American Men with Genetic Polymorphisms of Aldehyde Dehydrogenase

Epidemiologic studies have found that rates of alcohol use and alcoholism in persons of Asian descent are lower than rates in other ethnic groups. One possible reason is that about half of certain Asians, including Chinese, Japanese, and Korean persons, have a deficiency of the low-Km mitochondrial aldehyde dehydrogenase (ALDH2) isoenzyme, which is responsible for metabolizing acetaldehyde. A deficiency of ALDH2 results from inheritance of the mutant ALDH2*2 allele, a dominant mutation that exerts its effect both by reducing enzyme activity and increasing the turnover of this activity [1, 2]. After ingestion of alcohol, the faces of Asians with one or both alleles of ALDH2*2 become visibly flushed. Asians who are homozygous for ALDH2*1 generally lack visible alcohol-induced flushing or experience only a mild flush response. The dominance of the ALDH2 mutation, however, does not seem to be complete; phenotypic differences are associated with the three ALDH2 genotypes. Asians who are homozygous for ALDH2*2 drink very little alcohol [3], and no studies have found alcoholic persons with this genotype [4-8]. Asians who are heterozygous for ALDH2*2 drink less alcohol and are also less likely to be alcoholic compared with Asians with ALDH2*1 alleles, but they are not fully protected from alcoholism. Approximately 12% of alcoholic Asians have the ALDH2*1/2*2 genotype [5]. In the context of alcoholism or lower alcohol intake, Asian persons who are heterozygous for ALDH2*2 may be more vulnerable to alcohol-associated conditions, including liver disease [6-9], asthma [9], and esophageal cancer [10]. The three ALDH2 genotypes are also associated with variability in response to alcohol [11]. Asians who are homozygous for ALDH2*2 are very sensitive to alcohol and have tachycardia, hypotension, and vomiting after ingesting a moderate amount of alcohol. Asians who are heterozygous for ALDH2*2 are more sensitive to alcohol than Asians with ALDH2*1 alleles, although the response of the former is not necessarily aversive. Among Asians with an ALDH2 deficiency, differences in sensitivity to alcohol may be mediated by differences in alcohol metabolism, slower elimination of alcohol, or accumulation of acetaldehyde in the blood [12]. Some studies [13-17] have measured blood levels of alcohol or acetaldehyde after ingestion of alcohol in Asians who were known to have ALDH2 genotypes, but these studies had an inadequate sample size, did not include a placebo control, or did not control for use of alcohol and cigarettes (which can alter alcohol metabolism). We measured blood levels of alcohol and acetaldehyde after ingestion of alcoholic or placebo beverages in Asian-American men who underwent genotyping at the ALDH2 locus. Particular attention was given to matching the groups for age, height, weight, history of alcohol use, and history of smoking. Methods Asian-American men 21 to 25 years of age were recruited from advertisements in university newspapers for our randomized, double-blind, crossover study. They completed a questionnaire that solicited information on demographic characteristics; patterns of and problems with alcohol and drug use; and family history of alcohol, drug, and psychiatric problems. We excluded persons who completely abstained from alcohol, persons who had consumed more than 60 standard alcoholic drinks per month during the previous 6 months, and persons who reported that either biological parent was not of Chinese, Japanese, or Korean descent. Thirty-five men who did not have a personal or family history of alcohol dependence and who had no evidence of other substance dependence, major psychiatric disorders, or medical disorders gave informed consent to participate in two test sessions. The study was approved by the institutional review board at the Scripps Clinic and Research Foundation. Participants were asked to refrain from using alcohol, cigarettes, and other drugs (including aspirin, nonsteroidal anti-inflammatory agents, and anti-histamines) that might alter alcohol metabolism for 3 days before testing. On test days, each participant arrived at the clinic at 7:30 a.m. after an overnight fast. He then ate a low-fat breakfast (two slices of dry toast and juice), and an indwelling heparin lock was inserted for drawing blood. At the first session, blood was drawn and genotyping at the ALDH2 locus was done by using polymerase chain reaction of DNA and allele-specific oligonucleotide probes [1]. At 9:00 a.m., each participant was given a placebo beverage (3 mL of 95% alcohol in a reservoir on top of noncaffeinated, sugar-free soda) or 0.75 mL of 95% alcohol (0.56 g/kg of body weight) as a 20%-by-volume solution in the same mixer. The alcohol and placebo were ingested over 7 minutes through a placebo alcohol apparatus [18]. Blood was drawn to determine levels of alcohol and acetaldehyde before beverage ingestion and 15, 30, 45, 60, 90, 120, and 150 minutes after beverage ingestion. Blood alcohol concentrations were determined by using a modified alcohol dehydrogenase assay [19]. The rate of alcohol elimination (mg/kg per hour) was calculated from the slope of the pseudolinear decline of the blood alcohol concentration-time curve (usually from the 90-, 120-, and 150- minute samples) by using linear least-squares regression. Blood acetaldehyde levels were determined by using a modified fluorigenic high-performance liquid chromatographic assay [20] that had a detection sensitivity in the picomole range and intra-assay and interassay precisions of 2.4% and 3.7%, respectively. Statistical analyses, done by using SYSTAT software (SYSTAT, Inc., Evanston, Illinois), focused on differences between participants with ALDH2*1/2*1 and those with ALDH2*1/2*2. Demographic information, data on recent alcohol and cigarette use, peak blood alcohol concentration, time to peak blood alcohol concentration, volume of distribution, and rate of alcohol elimination were analyzed by using one-way analysis of variance; ALDH2 genotype was a between-participant variable. Data on blood alcohol concentration and acetaldehyde level were analyzed by using separate 2 8 analysis of variance for alcohol and placebo sessions; ALDH2 genotype was a between-participant variable, and time was a repeated measurement. Significant interactions were then analyzed by using post hoc comparisons with contrast matrices. The Bonferroni correction was used to limit the familywise error rate to 0.05 for comparisons among the placebo session time points and among the alcohol session time points. Results Genotyping for ALDH2 revealed 20 participants who had ALDH2*1/2*1 genotype, 13 who had ALDH2*1/2*2 genotype, and 2 who had ALDH2*2/2*2 genotype. Three participants (1 with ALDH2*1/2*2 genotype and the 2 with ALDH2*2/2*2 genotype) became ill after ingesting alcohol and were excluded from analyses because of missing data. One participant with ALDH2*1/2*2 genotype whose acetaldehyde levels exceeded 4 SDs from the mean (most likely as a result of instrumentation error) was also excluded from data analyses. The Table 1 shows demographic information and patterns of recent alcohol and cigarette use for the remaining 31 men. The ALDH2 genotype groups did not differ significantly for any of these variables; this reflects participant selection. Table 1. Demographic Information and Recent Patterns of Alcohol and Cigarette Use in 20 Asian-American Men with ALDH2*1/2*1 Genotype and 11 Asian-American Men with ALDH2*1/2*2 Genotype* Mean peak blood alcohol concentration SD was 81.3 12.48 mg/dL; the peak occurred 43.1 15.85 minutes after ingestion of alcohol. Mean volume of distribution was 0.718 0.1124 L/kg of body weight, and the mean rate of alcohol elimination was 97.8 33.97 mg/kg per hour. The ALDH2 genotype groups did not differ significantly for any of these variables. Mean blood alcohol concentrations for the alcohol session and mean acetaldehyde levels for the placebo and alcohol sessions, measured over time according to ALDH2 genotype, are shown in the (Figure 1). Figure 1. Mean (SD) blood levels of alcohol and acetaldehyde before and after ingestion of a placebo beverage containing 3 mL of 95% alcohol and an alcoholic beverage (0. n n P Analysis of variance revealed that the main effects for ALDH2 genotype and the interaction between ALDH2 genotype and time were not significant for the data on blood alcohol concentration from the alcohol session. Analysis of variance also revealed that the main effects for ALDH2 genotype and the interaction between ALDH2 genotype and time were significant for the data on acetaldehyde levels from the placebo sessions (ALDH2 genotype, P < 0.005; interaction between ALDH2 genotype and time, P < 0.013) and the alcohol sessions (ALDH2 genotype, P < 0.002; interaction between ALDH2 genotype and time, P < 0.001). Post hoc analyses with Bonferroni corrections revealed significant group differences 30, 45, and 60 minutes after placebo ingestion and 60, 90, 120, and 150 minutes after alcohol ingestion. Discussion We found that Asian-American men who were heterozygous for the ALDH2*2 allele did not differ from carefully matched men who were homozygous for the ALDH2*1 allele in measures of blood alcohol concentration overall or at any time after alcohol ingestion. These findings are consistent with the results of one study [14] but differ from those of other studies [15-17] in which persons with ALDH2*2 alleles had significantly slower rates of alcohol elimination than did persons with ALDH2*1 alleles. These discrepancies may result from group differences on important variables, especially history of alcohol use, that we controlled for. We also found that, despite equivalent blood alcohol concentrations, participants with ALDH2*1/2*2 genotype had significantly higher blood acetaldehyde levels after ingesting the alcohol beverage than did participants with ALDH2*1/2*1 genotype. These findings suggest that blood acetaldehyde levels rather than bloo

Effect of potent CYP2D6 inhibition by paroxetine on atomoxetine pharmacokinetics.

The purpose of this study was to characterize the effect of potent CYP2D6 inhibition by paroxetine on atomoxetine disposition in extensive metabolizers. This was a single‐blind, two‐period, sequential study in 22 healthy individuals. In period 1, 20 mg atomoxetine bid was administered to steady state. In period 2, 20 mg paroxetine was administered qd for 17 days. On days 12 through 17, 20 mg atomoxetine bid were coadministered. Plasma pharmacokinetics of atomoxetine, 4‐hydroxyatomoxetine, and N‐desmethylatomoxetine was determined at steady state in each treatment period. Plasma pharmacokinetics of paroxetine were determined after the 11th and 17th doses. Paroxetine increased Css,max, AUC0–12, and t1/2 of atomoxetine by approximately 3.5‐, 6.5‐, and 2.5‐fold, respectively. After coadministration with paroxetine, increases in N‐desmethylatomoxetine and decreases in 4‐hydroxyatomoxetine concentrations were observed. No changes in paroxetine pharmacokinetics were observed after coadministration with atomoxetine. It was concluded that inhibition of CYP2D6 by paroxetine markedly affected atomoxetine disposition, resulting in pharmacokinetics similar to poor metabolizers of CYP2D6 substrates.

Gender Differences in Alcohol Metabolism

A gender difference in alcohol pharmacokinetics has been suggested to explain why women are more vulnerable to ethanols toxic effects. The results of animal experiments suggest that females exhibit higher alcohol metabolic rates than males as a result of hormonal differences. Experimental results examining gender differences in human alcohol metabolism have been inconsistent; the diversity of experimental protocols and variety of pharmacokinetic parameters reported have made comparisons of these studies very difficult. Variability in alcohol metabolic rate between individuals of the same sex is often significant, preventing an assessment of gender differences in some studies. This chapter attempts to summarize the findings of studies from the last decade that examined the role of gender and sex hormone differences on ethanol metabolism in men and women. The role of body composition, genetic factors, gastric and hepatic alcohol dehydrogenase, and gastric absorption in creating gender differences in alcohol metabolism is discussed. Suggestions are offered that may result in better cross-study comparisons and more consistent experimental results.

Cloning and expression of a human stomach alcohol dehydrogenase isozyme

In humans, there is a family of NAD+- and zinc-dependent alcohol dehydrogenases (E.C. 1.1.1.1) that exhibit broad substrate specificity toward aliphatic alcohols (Vallee and Bazzone, 1983, Smith, 1986, and Bosron et al., 1993). The various isozyme subunits are encoded by at least 6 different gene loci (ADH1 through ADH6). Most recently, a new isozyme called σ-ADH or μ-ADH has been isolated from human stomach tissue that has a high K m (about 30 mM) and relatively high catalytic efficiency for ethanol (k c /K m ∼ 52 min-1mM-1)(Wang et al., 1990, Stone et al, 1993, Moreno and Pares, 1991). One or more isozymes with similar electrophoretic mobility are found in the esophagus (Yin et al., 1990).