genetic variation in aldehyde dehydrogenase 2 and the effect of alcohol consumption on cholesterol...
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Genetic variation in aldehyde dehydrogenase 2 and the effect ofalcohol consumption on cholesterol levels
Yasuyuki Nakamura a,*, Kenji Amamoto b, Shinji Tamaki a, Tomonori Okamura b,Yasuyuki Tsujita a, Yoshiki Ueno a, Yoshikuni Kita b, Masahiko Kinoshita a,
Hirotsugu Ueshima b
a First Department of Internal Medicine, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu City, Shiga 520-2192, Japanb Department of Health Science, Shiga University of Medical Science, Seta Tsukinowa-cho, Otsu City, Shiga 520-2192, Japan
Received 5 December 2001; received in revised form 30 January 2002; accepted 8 February 2002
Abstract
Moderate drinkers with a defective alcohol dehydrogenase type 3 (ADH3) genotype have higher high-density lipoprotein (HDL)
levels and a decreased risk of coronary artery disease (CAD). We examined the interaction between the aldehyde dehydrogenase
type 2 (ALDH2), alcohol intake, and HDL levels in 826 men and 1295 women in a rural town in Japan. The ALDH2 genotype of
each subject was determined by polymerase chain reaction (PCR) analysis. HDL was adjusted for the alcohol intake, age, body mass
index, smoking status, total cholesterol, triglycerides and HbA1c levels. None of the subjects had a history or ECG suggestive of
CAD. The proportions of ALDH2, *1/*1, *1/*2, and *2/*2 (defective homozygote) were 45.8, 46.0, and 8.2%, respectively, for men.
Drinking more than two drinks daily was associated with lower HDL levels in men with the defective genotypes compared with men
with a normal genotype (55.69/0.9 vs. 51.29/0.9 mg/dl, mean9/S.E., P B/0.0001). Also, drinking more than 0.5 drinks daily was not
associated with beneficial effects on HDL levels in women with defective ALDH2 genotypes. Conclusions: Alcohol intake did not
have beneficial effects on HDL levels in the defective ALDH2 genotype and may not protect against CAD in subjects with defective
ALDH2 genotypes. # 2002 Elsevier Science Ireland Ltd. All rights reserved.
Keywords: Alcohol; Polymorphism; Aldehyde dehydrogenase 2; High-density lipoprotein; Total cholesterol
1. Introduction
Epidemiological studies have consistently shown that
moderate alcohol consumption is associated with a
reduced risk of myocardial infarction [1,2], despite the
fact that alcohol consumption is closely related to the
prevalence of hypertension [3], one of the major
coronary risk factors. Although alcohol may be a
surrogate for favourable socioeconomic or lifestyle
factors associated with a reduction in coronary risk
[4], and anti-inflammatory action of alcohol could
contribute to the link between moderate consumption
and lower cardiovascular mortality [5], most of the
apparent benefit of alcohol consumption on the risk of
myocardial infarction has been attributed to an increase
in high-density lipoprotein (HDL) levels [2,6,7]. Two
enzyme systems, alcohol dehydrogenase (ADH) and
aldehyde dehydrogenase (ALDH), play key roles in
alcohol metabolism [8]. Class I ADH isoenzymes,
encoded by ADH1, ADH2 and ADH3, have low
Michaelis�/Menten constants (Km) for ethanol. ADH2
and ADH3 show polymorphisms that produce isoen-
zymes with distinct kinetic properties [8]. In Caucasian
populations, while variant alleles at the ADH2 locus are
relatively uncommon, but 40�/50% present at the ADH3
locus [9]. Recently, it has been reported in Caucasian
subjects that moderate drinkers with a defective alcohol
dehydrogenase ADH3 genotype have higher HDL
levels, and a decreased risk of myocardial infarction [6].
Acetaldehyde, a metabolite of ethanol by ADH, is
quickly metabolised into acetate by ALDH. Although
there are multiple forms of ALDH in the liver [9,10], the
mitochondrial enzyme encoded by the ALDH2 locus on
* Corresponding author. Tel.: �/81-77-548-2213; fax: �/81-77-543-
5839.
E-mail address: [email protected] (Y. Nakamura).
Atherosclerosis 164 (2002) 171�/177
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PII: S 0 0 2 1 - 9 1 5 0 ( 0 2 ) 0 0 0 5 9 - X
chromosome 12 has a very low Km for acetaldehyde. The
gene for ALDH2 is located on the long arm of
chromosome 12, and the low metabolic function of
this isozyme is due to a point mutation at position 1510with a G to A transition in exon 12, which changes the
codon GAA encoding glutamic acid (Glu) at position
487 into a lysine codon (AAA) [11]. Harada and co-
workers found a polymorphism at �/357 with a G to A
substitution in the promoter region of the ALDH2 gene,
and reported that the ALDH2*2 allele was linked to the
G promoter allele and the ALDH2*1 allele was linked to
the A promoter allele [12]. Nearly half of the Asianpopulation lacks this enzyme, resulting in high acetal-
dehyde concentrations after drinking, as well as flushing
and other symptoms [11,13]. ALDH2 deficiency in-
cludes the heterozygote ALDH2*1/*2 and the atypical
homozygote ALDH2*2/*2. Although ALDH2 defi-
ciency can protect against alcoholism and alcohol liver
disease [11,14], the effects of moderate drinking on HDL
levels among ALDH2-deficient subjects are not known.Thus, we examined the interaction between the ALDH2
genotype, the level of alcohol intake, and HDL and total
cholesterol (TC) levels in 2121 Japanese men and
women.
2. Subjects and methods
2.1. Subjects
Of 2892 local residents who underwent a mass
medical examination in 1999 at S town (population of
about 15 000), a mountain farming community in
Western Japan, a total of 2395 subjects consisting of
917 men (mean age 589/15.7) and 1478 women (mean
age 56.39/15.6) from whom informed consent was
obtained after a full explanation of this genetic studywere enrolled. Of these, 274 were excluded because the
genotype was not determined (46 men, 44 women) or
they were taking lipid-lowering medications (45 men,
139 women). None of the subjects had a history or ECG
suggestive of coronary artery disease. This study was
approved by the Institutional Review Board of Shiga
University of Medical Science (No. 11�/15, 1999).
2.2. Genetic analysis
DNA was extracted from the buffy coat of whole
blood. ALDH2 genotypes were determined by the
polymerase chain reaction-the restriction fragment
length polymorphism (PCR-RFLP) method developed
by Takeshita and co-workers. [15]. Briefly, CAAATTA-
CAGGGTCAACTGCT and CCACACTCA-CAGTTTTCTCTT were used as 5? and 3? primers,
respectively. The corresponding DNA segment of
ALDH2 was amplified by the PCR on a Gene Amp
PCR System 9700 (Perkin�/Elmer, USA). After initial
denaturation at 94 8C for 60 s, annealing at 52 8C for
30 s, and extension at 72 8C for 30 s, samples were
incubated at 72 8C for 60 s. The amplified DNAfragment was cleaved by the restriction endonuclease
KSP6321, electrophoresed on a 3.5% Nusieve Agarose
gel (Biowhittaker Molecular Applications, USA), and
observed for a 112-bp fragment (ALDH2*2/*2 geno-
type), a 23-bp fragment (ALD2*1/*1 genotype), and
both 112-bp and 23-bp fragments (ALDH2*1/*2 geno-
type). Genotypes, determined by the PCR-RFLP
method on a total of 75 random samples consisting of25 PCR products of each genotype, were confirmed by
direct sequencing. Briefly, after fractionation of PCR-
RFLP products on 1% agarose gels, the desired DNA
bands were cut out, and the DNA was purified using a
QIAquick Gel Extraction Kit (QIAGEN, USA) and was
amplified with the above 5? primer, followed by analysis
on a ABI PRISM 310 Genetic Analyser (Perkin�/Elmer).
2.3. Measurements of serum cholesterol
Non-fasting blood was drawn and serum TC and
HDL levels were determined in one laboratory (Medic,
Shiga). The measurement precision and accuracy of
these serum lipids were certificated through a lipid
standardisation program by Osaka Medical Center for
Cancer and Cardiovascular Diseases, which is a member
of Cholesterol Reference Method Laboratory Network(CRMLN) controlled by the Centers for Disease Con-
trol and Prevention (Atlanta) [16].
2.4. Information on alcohol intake
Using a questionnaire, a well-trained public health
nurse obtained information on alcohol intake from each
subject. The frequency of drinking during an averageweek and the alcohol intake on each occasion were
determined, and the alcohol intake per week was
calculated, which was then divided by 7 to give the
alcohol intake per day. Two drink units were defined as
one GO (180 ml) of sake (23 g of ethanol), two bottles
(350�/2 ml) of beer, two single whiskeys, or two glasses
(180 ml) of wine.
2.5. Statistics
SAS version 6.12 on UNIX was used throughout the
study. The t -test was used to compare the means of
continuous variables in two groups and the chi-square
test was used to compare dichotomous variables. To
compare means among the three genotype groups, one-
way analysis of variance (ANOVA) was used. To assesswhether the ALDH2 genotype affected the relation
between the level of alcohol intake and HDL and TC
levels, we performed an analysis of covariance by
Y. Nakamura et al. / Atherosclerosis 164 (2002) 171�/177172
adjusting for confounding factors: age, amount of
alcohol intake, BMI, and triglyceride levels (plus TC
levels in case of analysis for HDL), HbA1c value and
current smoking status. Since the average levels ofalcohol intake were lower among women than among
men, the categories of alcohol intake were dichotomised
at two drinks per day for men and at 0.5 drinks per day
for women.
Due to higher incidence of cholestryl ester transfer
protein (CETP) deficiency among subjects with high
HDL levels [17,18], separate analyses on the interaction
between the ALDH2 genotype, amount of alcoholintake, and HDL levels were performed after excluding
the subjects with HDL levels more than 80 mg/dl. There
were 136 subjects (29 men and 107 women) whose HDL
levels more than 80 mg/dl.
All P values were two-tailed, and P B/0.05 was
considered significant.
3. Results
3.1. Direct sequencing
Direct sequencing of 25 randomly selected samples of
each ALDH2 genotype identified by the PCR-RFLP
method did not show any discrepancy between the PCR-RFLP-determined genotypes in exon 12 of ALDH2 and
the 1510G/A sequence variations. In addition, no
sequence variations were found other than the 1510G/
A variations in exon 12 of ALDH2 [12]. Other reported
variations such as 1464G/A and 1486G/A were not
observed in the present study [19].
3.2. Characteristics of the subjects
Table 1 shows the characteristics of the subjects. Age,
height, weight, triglycerides, variables related to alcohol
consumption and the incidence of smoking were higher
in men, whereas TC and HDL levels were higher in
women. There were no difference in BMI and HbA1c.
Table 2 presents the variables in Table 1 grouped by
gender and the ALDH2 genotype. The frequencies ofthe ALDH2*1/*1, *1/*2 and *2/*2 genotypes were 45.8,
46.0 and 8.2% in men, and 50.6, 42.0 and 7.4% in
women, respectively, which indicated there were no
significant gender differences in the distribution. In
men, a comparison of ALDH2 genotypes showed
significant differences in weight, BMI, triglycerides,
and drinking-related variables. In comparison with
other genotypes, the subjects with the ALDH2*1/*1genotype consumed more alcohol on average and more
subjects had a habit of drinking. In addition, body
weight, BMI, and triglycerides were higher in this
subgroup. Age, height, TC and HDL levels, HbA1c
and the incidence of smoking were not different among
the three genotypes in men.
In women, subjects with the ALDH2*2/*2 genotype
were slightly older than those in the other groups. TClevels were lower in the ALDH2*1/*1 genotype.
Although the frequency and the average amount of
alcohol consumed were lower in women than in men,
women with the ALDH2*1/*1 genotype consumed more
alcohol on average and more had a habit of drinking. In
contrast to the results in men, significantly more women
with the ALDH2*2/*2 genotype were smokers com-
pared with women of the other genotypes. Althoughweight, BMI, and triglycerides were higher in men with
the ALDH2*1/*1 genotype, there were no similar
differences among the three genotypes in women.
3.3. HDL and TC levels adjusted for confounding factors
Among men who consumed less than two drinks per
day, the mean adjusted HDL levels were not signifi-
cantly different among the three ALDH2 genotypes.
However, among men who consumed at least two drinks
per day, the mean adjusted HDL levels were higher
Table 1
Characteristics of the subjects, grouped by gender
Variable gender Men Women P
N (Total�/2121) 826 1295
Age (year) 57.99/15.7 55.49/15.8 B/0.001
Height (cm) 165.79/6.7 152.89/7.0 B/0.001
Weight (kg) 62.29/9.7 52.49/8.4 B/0.001
BMI (m2) 22.69/3.0 22.49/3.2 0.19
TC 184.09/33.3 196.49/34.7 B/0.001
HDL 52.89/14.1 60.79/14.0 B/0.001
TG 147.49/102.5 114.59/66.4 B/0.001
HbA1c 5.19/0.8 5.19/0.7 0.23
EtOH intake (drinks per day) 1.99/1.9 0.39/0.6 B/0.001
Number of drinkers at �/0.5 drinks per week 593 (71.8%) 289 (22.3%) B/0.001
Number of drinkers at ]/two drinks per day 426 (51.6%) 63 (4.9%) B/0.001
Smokers 421 (51.0%) 97 (7.5%) B/0.001
Y. Nakamura et al. / Atherosclerosis 164 (2002) 171�/177 173
among those with the ALDH2*1/*1 genotype than those
with the ALDH2*1/*2 genotype (55.69/0.9 vs. 51.29/0.9
mg/dl, mean9/S.E., P B/0.0001). In the ALDH2*1/*1
genotype A, men who consumed at least two drinks per
day showed higher mean adjusted HDL levels than men
who consumed less than two drinks per day (B/two
drinks per day: 52.69/1.1 vs. ]/two drinks per day:
55.69/0.9 mg/dl, P B/0.05) (Fig. 1A). These differences
were not seen in the defective ALDH2 genotypes.Among men who consumed less than two drinks per
day, the mean adjusted TC levels in the ALDH2*1/*1
genotype were lower than those in the ALDH2*2/*2
genotype (180.79/2.5 vs. 195.39/3.5 mg/dl, P�/0.001).
Among men who consumed at least two drinks per day,
the mean adjusted TC levels in the ALDH2*1/*1
genotype were lower than those in the ALDH2*1/*2
genotype (180.89/1.8 vs. 187.29/3.3 mg/dl, P�/0.031). A
comparison of mean adjusted TC levels in the ALDH2
genotype did not show any significant differences in all
the three subgroups (Fig. 1B).
Among women who consumed less than 0.5 drinks
per day, the mean adjusted HDL levels in the
ALDH2*1/*1 genotype were higher than those in the
ALDH2*1/*2 genotype (59.99/0.9 vs. 58.39/0.8 mg/dl,
P�/0.04) (Fig. 2A). Among women who consumed less
than 0.5 drinks per day, the mean adjusted TC levels in
the ALDH2*1/*1 genotype were lower than those in the
other genotypes (193.69/2.2 vs. 199.49/2.1 vs. 201.89/
3.3 mg/dl, P�/0.003 and 0.01, respectively) (Fig. 2B). Acomparison within the ALDH2 genotype showed sig-
nificant differences in the mean adjusted HDL and TC
levels in the ALDH2*1/*2, (HDL in ALDH2*1/*2: B/
0.5 drinks per day: 58.39/0.8 vs. ]/0.5 drinks per day:
63.39/1.6 mg/dl, P B/0.05; TC in ALDH2*1/*1: B/0.5
drinks per day: 199.49/2.1 vs. ]/0.5 drinks per day:
185.29/4.0 mg/dl, P B/0.05) (Fig. 2A and B).
Separate analyses on the interaction between theALDH2 genotypes, amount of alcohol consumption,
and HDL levels after excluding the subjects with HDL
levels more than 80 mg/dl did not cause any significant
differences in the results (data not shown).
4. Discussion
The present study showed that the beneficial effects of
moderate alcohol consumption on HDL levels, namely
an increase in HDL levels, were most prominent among
men with the ALDH2*1/*1 genotype. This finding is instriking contrast to the results of a study on the
interaction between moderate alcohol consumption
and the ADH3 genotype with regard to HDL choles-
Table 2
ALDH2 Genotype and characteristics of the subjects
Variable genotype *1/*1 *1/*2 *2/*2 P
Men
N (Subtotal�/826) 378 (45.8%) 380 (46%) 68 (8.2%)
Age (year) 57.89/15.5 58.69/15.4 53.89/17.7 0.07
Height (cm) 165.89/6.7 165.79/6.7 165.99/6.8 0.98
Weight (kg) 63.19/10.0 61.79/9.5 60.49/8.8 0.03
BMI (m2) 22.99/3.0 22.49/2.9 21.99/2.6 0.008
TC 183.79/35.3 183.69/31.6 188.39/31.7 0.54
HDL 53.99/14.1 52.19/14.1 50.49/13.4 0.07
TG 159.39/118.2 139.29/88.0 127.49/72.9 0.006
HbA1c 5.29/1.0 5.19/0.7 5.19/0.5 0.09
EtOH intake (drinks per day) 2.49/1.7 1.79/2.0 0.19/0.4 B/0.001
Number of drinkers at �/0.5 drinks per week 317 (83.9%) 270 (71.1%) 6 (8.8%) B/0.001
Number of drinkers at ]/two drinks per day 257 (68.0%) 167 (44.0%) 2 (3.0%) B/0.001
Smokers 192 (50.8%) 192 (50.7%) 36 (53.7%) 0.89
Women
N (Subtotal�/1295) 655 (50.6%) 544 (42.0%) 96 (0.7%)
Age (year) 55.29/16.1 55.09/15.6 59.29/13.9 0.04
Height (cm) 152.99/72.0 152.99/68.6 151.99/66.6 0.38
Weight (kg) 52.59/8.2 52.49/8.6 51.99/7.9 0.79
BMI (m2) 22.49/3.1 22.49/3.3 22.59/3.2 0.96
TC 193.89/34.8 197.99/34.7 205.89/32.9 0.003
HDL 61.29/13.7 60.09/14.0 61.09/16.3 0.35
TG 114.39/69.2 114.39/63.0 116.59/66.9 0.95
HbA1c 5.19/0.7 5.09/0.7 5.19/0.6 0.37
EtOH intake (drinks per day) 0.49/0.7 0.29/0.4 0.09/0.2 B/0.001
Number of drinkers at �/0.5 drinks per week 218 (33.3%) 69 (12.7%) 2 (2.1%) B/0.001
Number of drinkers at ]/two drinks per day 49 (7.5%) 13 (2.4%) 1 (1.0%) B/0.001
Smokers 38 (5.8%) 46 (8.5%) 12 (12.5%) 0.028
Y. Nakamura et al. / Atherosclerosis 164 (2002) 171�/177174
terol levels and the risk of myocardial infarction
conducted by Hines and co-workers [9]. They found
that moderate drinkers who were homozygous for the
slow-oxidising ADH3 allele had higher HDL levels and
a substantially decreased risk of myocardial infarction.
Although we were not able to examine the effect of
alcohol consumption on the risk of myocardial infarc-
tion in the present study, alcohol intake may not protect
against myocardial infarction in subjects with defective
ALDH2 genotypes, as was the case in subjects with
defective ADH3 genotypes.
Association between alcohol consumption and an
increase in HDL levels has been well documented [20].
However, the mechanism by which alcohol increases
HDL is controversial. Studies in alcohol abusers whoconsume on average 80�/177 g/day of alcohol have
suggested that reductions in the plasma cholesteryl ester
transfer protein (CETP) concentration and activity were
responsible for the increase in the HDL levels by alcohol
Fig. 1. Adjusted High-Density Lipoprotein (HDL) and Total Choles-
terol (TC) levels according to the level of alcohol intake and the
ALDH2 genotype in the male subjects. Among men who consumed
less than two drinks per day, the mean adjusted HDL levels were not
significantly different among the three ALDH2 genotypes. However,
among men who consumed at least two drinks per day, the mean
adjusted HDL levels were higher among those with the ALDH2*1/*1
genotype than those with the ALDH2*1/*2 genotype (55.69/0.9 vs.
51.29/0.9 mg/dl, mean9/S.E., P B/0.0001). A comparison of mean
adjusted HDL levels in the ALDH2 genotype showed a significant
difference in the ALDH2*1/*1 genotype (B/two drinks per day: 52.69/
1.1 vs. ]/two drinks per day: 55.69/0.9 mg/dl, P B/0.05) (A). Among
men who consumed less than two drinks per day, the mean adjusted
TC levels in the ALDH2*1/*1 genotype were lower than those in the
ALDH2*2/*2 genotype (180.79/2.5 vs. 195.39/3.5 mg/dl, P�/0.001).
Among men who consumed at least two drinks per day, the mean
adjusted TC levels in the ALDH2*1/*1 genotype were lower than those
in the ALDH2*1/*2 genotype (180.89/1.8 vs. 187.29/3.3 mg/dl, P�/
0.031). A comparison of mean adjusted TC levels in the ALDH2
genotype did not show any significant differences in all the three
subgroups (B). Numeric P values are for the comparison with the
values in men who were in the ALDH2*1/*1 genotype in each category
of alcohol consumption. * denotes P B/0.05 and # denotes not
significant for the comparison between the values in men who
consumed less than two drinks daily versus the values in men who
consumed at least two drinks daily in each ALDH2 genotype.
Fig. 2. Adjusted High-Density Lipoprotein (HDL) and Total Choles-
terol (TC) levels according to the level of alcohol intake and the
ALDH2 genotype in the female subjects. Among women who
consumed less than 0.5 drinks per day, the mean adjusted HDL levels
in the ALDH2*1/*1 genotype were higher than those in the
ALDH2*1/*2 genotype (59.99/0.9 vs. 58.39/0.8 mg/dl, P�/0.04) (A).
Among women who consumed less than 0.5 drinks per day, the mean
adjusted TC levels in the ALDH2*1/*1 genotype were lower than those
in the other genotypes (193.69/2.2 vs. 199.49/2.1 vs. 201.89/3.3 mg/dl,
P�/0.003 and 0.01, respectively) (B). A comparison within the
ALDH2 genotype showed significant differences in the mean adjusted
HDL and TC levels in the ALDH2*1/*2, (HDL in ALDH2*1/*2: B/
0.5 drinks per day: 58.39/0.8 vs. ]/0.5 drinks per day: 63.39/1.6 mg/dl,
P B/0.05; TC in ALDH2*1/*1: B/0.5 drinks per day: 199.49/2.1 vs. ]/
0.5 drinks per day: 185.29/4.0 mg/dl, P B/0.05) (A and B). Numeric P
values are for the comparison with the values in women who were in
the ALDH2*1/*1 genotype in each category of alcohol consumption. *
denotes P B/0.05 and # denotes not significant for the comparison
between the values in women who consumed less than 0.5 drinks daily
versus the values in women who consumed at least 0.5 drinks daily in
each ALDH2 genotype.
Y. Nakamura et al. / Atherosclerosis 164 (2002) 171�/177 175
[21]. However, in another study that examined the effect
of moderate alcohol loading (0.5 g/kg body weight per
day) for 4 weeks after 3 weeks of abstinence, CETP
activity did not change, while HDL levels increased
significantly [22]. This study suggested that an increase
in lipoprotein lipase activity contributed the most to the
alcohol-induced rise in HDL levels. Thus, CETP may
not play an important role in alcohol-induced HDL
elevation in subjects who drink moderately. Whatever it
may be, the mechanism appears to work differently
when the acetaldehyde concentration is elevated in
subjects with the ALDH2-deficient genotype. More
recent studies indicated that alcohol increases HDL by
increasing the transport rate of apolipoprotein A-I
[23,24].
Plasma CETP deficiency was reported as a prevalent
genetic cause of elevated HDL levels in Japanese
subjects. Heterozygote frequencies of two common
mutation, intron 14G(1�/)-to-A (intron 14A) transition
and Asp442-to-Gly (D442G) missense mutation in exon
15, were 2 and 7%, respectively, in the Kanazawa area in
Japan [18]. Furthermore, the missense mutation was
found in Chinese population at a frequency of 4�/6%
[25]. Controversies exist as to the association between
the CETP deficiency and the coronary risk. Some
studies reported an increased risk of MI in the subjects
with CETP gene defects [26], the other studies reported
contrary [17,18,27]. Possible role of CETP deficiencies
was ruled out in the present study by the separate
analyses after excluding subjects with HDL levels more
than 80 mg/dl. However, studying an interaction be-
tween ALDH2 and CETP gene polymorphism is inter-
esting, and should be carried out.
A high percentage of the Asian population has a
defect in the ALDH2 genotype [11,13]. Subjects with a
defective ALDH2 genotype have a higher acetaldehyde
concentration after drinking alcohol, and show flushing
or other symptoms. It has also been suggested ALDH2
deficiency protects against alcoholism and alcohol-
induced liver damage because subjects with ALDH2
deficiency cannot tolerate large amount of alcohol
[17,20]. In our study, however, 44% of men with the
ALDH2*1/*2 genotype reported drinking more than
two drinks daily.
As seen in other studies, the women in the present
study consumed significantly less alcohol and signifi-
cantly fewer had a habit of drinking in comparison with
the men [9]. Therefore, a cut-off level of 0.5 drinks daily
was used for women, instead of two drinks daily, for the
analyses. The findings in the women were slightly
different from those in the men. Nevertheless, the
beneficial effects of alcohol intake were not at all
prominent in the ALDH2-deficient genotypes as in
men and women with ADH3 genotypes in the previous
study [9].
Problems in the self-reporting of drinking may
potentially limit the value of the present study, since
such a system may underestimate or overestimate the
true intake, especially in men who actually consumelarge amounts of alcohol [28,29]. However, the self-
reporting system has been shown to be useful [29], and
studies using such a system have provided important
information [2,9].
None of the subjects in our study had a history or
ECG suggestive of coronary artery disease. Therefore,
there is no direct evidence that alcohol intake protects
against coronary artery disease. These subjects need tobe followed-up for a longer period.
The polymorphism of other alcohol-metabolising
enzymes needs to be investigated. ADH2 polymorph-
isms are known to exist in Japanese. However, it has
been shown that 85% of Japanese possess an ADH
isozyme encoded by the ADH2*2 allele [30]. Therefore,
it is expected that most of the subjects in the present
study possessed the same ADH2 allele.Alcohol intake had quite different effects on HDL
levels in Japanese with a defective ALDH2 genotype in
comparison with a defective ADH3 genotype in Cauca-
sians. Unlike with the ADH3 genotype, alcohol intake
may not protect against MI in subjects with a defective
ALDH2 genotype.
Acknowledgements
This study was supported in part by a contract from
the Japanese Ministry of Education (Grant-in-aid for
Scientific Research on Priority Areas (C): 12204059,
Grant-in-aid for Scientific Research (B): 02454211,
Grant-in-aid for Scientific Research (C): 06670414).
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