From the Division of Endocrinology, Diabetes and Clinical Nutrition,
Department of Medicine, Oregon Health Sciences University, Portland.
Correspondence to D. Roger Illingworth, MD, PhD, Department of Medicine, L465, Oregon Health Sciences University, 3181 SW Sam Jackson Park Rd, Portland, OR 97201-3098. E-mail bisaccip{at}ohsu.edu
Methods and Results—We determined the ACE genotypes and
incidence of MI or surgical intervention for CHD in 213 adult patients
with heterozygous FH or FDB. The incidence of MI in 35 male patients
who carried the ACE DD genotype was 2.5 times that observed in
male patients with the II or DI genotypes, and the incidence of
CHD in male patients with the DD genotype was 2.2 times higher
than in those who had ACE DI+II. The potential effects of ACE
genotype on CHD could not be directly compared in female
patients because of a disparity in the smoking history of the genotypic
groups. From logistic regression analysis, the estimated odds
ratio associated with the ACE DD genotype was 2.57 for MI and
2.21 for CHD adjusted for age, sex, and smoking history.
Conclusions—The ACE DD genotype is associated with an
increased risk of MI and CHD in patients with heterozygous FH or FDB.
Determination of the ACE genotype in asymptomatic
FH and FDB patients provides an additional means to identify those
patients at greatest risk for the premature development of CHD.
Patients with heterozygous FH or FDB are known to be at substantially
increased risk for premature MI and CHD because of their high
circulating levels of LDL.16 17 18 19 These patients
are particularly prone to the development of lipid-rich plaques in
their coronary arteries19 and may be
particularly susceptible to arterial stenosis
requiring surgical intervention in the presence of ACE DD
genotype–associated intimal-medial thickening or to plaque
rupture in the presence of ACE DD genotype–associated plaque
instability. We hypothesized that patients with heterozygous FH or FDB
who also carry the ACE DD genotype should be at higher risk for
MI and surgical intervention for CHD than patients with the ACE DI+II
genotypes.
Genomic DNA was isolated by standard
methodology,20 and ACE genotypes were
determined by polymerase chain reaction analysis according to
the method of Rigat et al,21 modified by the
inclusion of 5% (vol/vol) dimethyl sulfoxide in the final reaction
mixture to aid in the amplification of the I
allele.22
CHD was defined as a history of MI or surgical intervention for
CHD. Hypertension was defined by a history of having been prescribed
hypotensive medication. No differences were found in the incidence of
CHD or MI between patients with the ID and II genotypes, and
patients from these two genotypic groups have been combined into one
group designated II+DI for statistical analysis and comparison
of the incidence of cardiovascular disease. Statistical
analysis of the data was performed by contingency
testing.23 Odds ratios were computed from a
multivariate logistic regression model to provide an
estimate of the relative risk of MI or CHD. The model tested the
association of the presence or absence of the ACE DD genotype
with MI or CHD risk, with adjustment for the effects of sex and smoking
history. Additional analyses were performed using apo E
genotype, hypertension, Lp(a) concentrations, or untreated LDL
cholesterol levels in those patients in whom complete
information was available. Multivariate logistic
regression analyses were done with a JMP statistical software
package, version 3.15 (SAS Institute Inc).
The 213 patients with heterozygous FH or FDB consisted of 163 unrelated
subjects and 50 patients who were derived from 20 separate families. In
5 of the families, more than one patient had CHD, but only 1 family
included 2 patients with the ACE DD genotype who concurrently
had CHD. Of the patients with heterozygous FH, 2 were of Japanese
ancestry, 1 was of Chinese ancestry, and the remaining 210 were
Caucasian.
The incidence of CHD and previous MI in male and female patients
classified according to their ACE genotypes is shown in Table 2
Multiple logistic regression analysis of the data indicates
that, although male gender and a positive history of cigarette smoking
are each independently associated with an increased risk of MI and CHD
of more than 3-fold, the ACE DD genotype is itself associated
with a 2.57-fold increase in the risk of MI (P=.018) and a
2.21-fold increase in the risk of CHD (P=.021) after
adjustment for the effects of sex and smoking history (Table 3
Although our results did not disclose an increased incidence of MI or
CHD in female patients with heterozygous FH with the ACE DD
genotype compared with female patients with the DI+II
genotypes, the overall incidence of CHD in the female patients
was lower, and the female patients who carried the ACE DD
genotype had a lower incidence of cigarette smoking than ACE
DI+II female patients (Table 1
Received September 12, 1997;
revision received January 5, 1998;
accepted January 9, 1998.
© 1998 American Heart Association, Inc.
Clinical Investigation and Reports
Angiotensin-Converting Enzyme DD Genotype and Cardiovascular Disease in Heterozygous Familial Hypercholesterolemia
Abstract
Top
Abstract
Introduction
Methods
Results
Discussion
References
Background—Controversy exists as to
whether the deletion/deletion genotype (DD) of the ACE gene
polymorphism increases the risk of myocardial infarction (MI).
Studies have suggested that the ACE DD genotype is associated
with increased plaque instability. We hypothesized that the ACE DD
genotype may increase the risk of myocardial infarction and
coronary heart disease (CHD) in patients with heterozygous
familial hypercholesterolemia (FH) or familial
defective apolipoprotein B-100 (FDB) who, as a group, are at high risk
of having lipid-rich plaques in their coronary arteries.
Key Words: angiotensin • myocardial infarction • hypercholesterolemia • coronary disease
Introduction
Top
Abstract
Introduction
Methods
Results
Discussion
References
The ACE I/D
polymorphism was identified in 1990 and has been shown to be
strongly associated with variations in the levels of ACE in plasma,
with 47% of the observed phenotypic variation being attributable to
the segregation of the ACE I/D alleles.1 The
ACE DD genotype has been shown to be associated with increased
plasma concentrations of circulating ACE, which results in the enhanced
conversion of angiotensin I to II1 ;
angiotensin II has been shown to increase the influx of
125I-labeled LDL into the arterial
wall of rabbits.2 Interest in the effects of the
ACE polymorphism on cardiovascular disease was
stimulated by results of a large multicenter case-control study in
which the presence of the ACE DD genotype was associated with
an overall 1.3-fold increased risk of MI, with an odds ratio of 3.2 in
a subset of men considered at low risk for CHD.3
Although some subsequent studies confirmed the higher frequencies of
the ACE DD genotype in patients with MI or
CHD,4 5 6 the finding has not been
consistently observed,7 8 9 and the
inconsistency has led to confusion.10
The ACE DD genotype has been shown to be associated with
intimal-medial thickening in the carotid
artery,11 12 and a 2-fold-higher adjusted odds
ratio for restenosis after intracoronary stent
implantation.13 In a recent meta-analysis
of 15 studies involving 3394 MI patients and 5479 control subjects, the
odds ratio for MI in patients with the DD genotype versus the
DI+II genotypes was 1.26.14 It has been
proposed that plaque instability may be increased in patients with the
ACE DD genotype,15 thereby putting these
patients at increased risk for plaque rupture, unstable angina, and
MI.
Methods
Top
Abstract
Introduction
Methods
Results
Discussion
References
Blood samples were obtained from patients with heterozygous FH
or FDB (96 men and 117 women; age, 
40 years) attending the Lipid
Disorders Clinic at Oregon Health Sciences University. Patients were
diagnosed to have heterozygous FH or FDB on the basis of persistent
primary hypercholesterolemia with elevated
concentrations of LDL cholesterol, an inheritance pattern
consistent with autosomal dominant, and the presence of tendon
xanthomas in the index patient or in a first-degree relative.
Heterozygous FH and FDB are both autosomal-dominant genetic disorders
that are distinguishable at the molecular level but result in a uniform
phenotype of highly elevated plasma concentrations of
LDL.18 All patients underwent a comprehensive
history and physical examination and blood samples were obtained for Lp
analysis and the exclusion of secondary causes of
hyperlipidemia. Clinical characteristics of the
patients, including previous MI or history of angioplasty or
coronary artery bypass graft surgery, were based on patient
history and examination and review of medical records. Patients
whose medical records disclosed a history of diabetes mellitus were
excluded from this study.
Results
Top
Abstract
Introduction
Methods
Results
Discussion
References
The frequencies of the ACE II, DI, and DD genotypes in the
213 patients with heterozygous FH or FDB (21%, 46%, and 33%,
respectively) were similar to those predicted for Hardy Weinberg
equilibrium (19%, 49%, and 32%, respectively), indicating that we
had not received a disproportionate referral of patients enriched or
depleted in one genotypic group. The distribution of known
cardiovascular risk factors and Lp values in male and
female patients with the ACE II+DI and DD genotypes is shown in
Table 1
; with the exception of smoking in
women, the groups are comparable.
View this table:
[in a new window]
Table 1. Cardiovascular Risk Factors of
Heterozygous FH and FDB Patients by ACE Genotype . Male patients with heterozygous FH or
FDB were 2.5 times more likely to have suffered an MI if they carried
the ACE DD genotype than similar patients with the ACE DI+II
genotypes (40% versus 16% incidence, respectively;
P<.02). The frequency of documented CHD (defined by
previous coronary artery bypass surgery, angioplasty, or MI)
was also found to be 2.2 times higher in male patients with the ACE DD
genotype (71% incidence in ACE DD males) compared with male
patients with the ACE DI+II genotype, in whom the overall
incidence was 33% (P<.001). In contrast to the findings in
male patients with heterozygous FH or FDB, we observed no significant
differences in the incidence of either MI or CHD in female patients
with the ACE DD genotype compared with female patients with the
DI+II genotypes (Table 2). However, the incidence of MI and CHD
was significantly lower than in their male counterparts (Table 2), and
a prior history of cigarette smoking was significantly less common in
female patients with the ACE DD genotype than in the other
genotypic groups (Table 1
).
View this table:
[in a new window]
Table 2. Effect of ACE Genotype on the Incidence of
CHD in Patients With Heterozygous FH and FDB ). Similar analyses were run on
subsets of the FH and FDB patients testing for the effect of apo E
genotype, Lp(a) concentrations, hypertension, untreated LDL
cholesterol levels, and the age at which hypolipidemic
therapy was started. In each case, the tests were run on all patients
for whom the additional information was available [n=197, 176, 205,
and 205 for apo E genotype, Lp(a), hypertension, and the age at
start of hypolipidemic therapy, respectively]. No significant
association was observed between any of these variables and the
risk of MI and CHD in these patients. The ACE DD
genotype–associated odds ratios for MI and CHD were unaffected
by adjustment for these variables. Information on untreated LDL
cholesterol levels was not available in 12 patients with a
history of a previous MI, and of these, 7 carried the ACE DD
genotype. The effects of this variable could not be tested
by multiple logistic regression analysis; however, untreated
LDL cholesterol levels did not differ significantly between
ACE genotypic groups in the 177 patients for whom this information was
available (Table 1), making it unlikely that the increased incidence of
MI and CHD observed in the FH and FDB patients who carry the ACE DD
genotype was due to differences in the baseline concentrations
of LDL cholesterol.
View this table:
[in a new window]
Table 3. Adjusted Odds Ratios for
Cardiovascular Risk Factors in Patients With
Heterozygous FH and FDB
Discussion
Top
Abstract
Introduction
Methods
Results
Discussion
References
We found that the presence of the ACE DD genotype is
associated with a significant increase in the risk of patients with
heterozygous FH or FDB suffering a MI or requiring surgical
intervention for coronary artery disease. The adjusted odds
ratio for the ACE DD genotype associated risk of MI (2.5) is
higher than the mean value reported in a recent meta-analysis
of 15 previous studies (none of which focused on patients with primary
hypercholesterolemia), in which the odds ratio
for MI in patients with the DD genotype versus those with a
DI+II genotype was 1.26.14 Our results
are consistent with the hypothesis that the presence of the ACE
DD genotype may accelerate the risk of suffering a
cardiovascular event caused by plaque rupture in those
patients who are at high risk of having unstable lipid-rich plaques in
their coronary arteries.19 24 Potential
mechanisms by which the presence of the ACE DD genotype may
increase the risk of plaque rupture in patients with heterozygous FH
include accelerating the rate of influx of LDL particles into the
arterial wall with a resultant increase in plaque lipid
content,19 promoting an increase in local shear
forces on the arterial wall,24 and
promoting endothelial dysfunction and vascular smooth
muscle cell proliferation.13 25 ) and consequently had a decreased risk
of developing coronary disease. The adjusted odds ratios
estimate that the ACE DD genotype is associated with a
2.57-fold increased risk of MI and a 2.21-fold increased risk of CHD
after adjustment for the effect of gender and smoking history. Our
results indicate that the determination of ACE genotypes in
patients with heterozygous FH or FDB may be useful as an additional
discriminator of cardiovascular risk in
asymptomatic patients. More aggressive treatment would seem
appropriate for those patients with the ACE DD genotype; these
recommendations parallel those previously suggested for patients with
heterozygous FH who have concurrently increased plasma concentrations
of Lp(a).17
Selected Abbreviations and Acronyms
Apo
=
apolipoprotein
CHD
=
coronary heart disease
D
=
deletion
FDB
=
familial defective apolipoprotein B-100
FH
=
familial hypercholesterolemia
I
=
insertion
Lp
=
lipoprotein
MI
=
myocardial infarction
Acknowledgments
This study was supported in part by grants from the General
Clinical Research Centers, National Institutes of Health (RR-334) and
from the Oregon Affiliate of the American Heart Association. We are
grateful to Dr Gary Sexton for statistical analysis of the
data.
References
Top
Abstract
Introduction
Methods
Results
Discussion
References
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