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2160
The catecholamines, epinephrine, norepinephrine, dopa- mine, and catechol estrogen play a critical role in car- diovascular, sympathetic, and endocrine pathways. Variation
in the levels of these signaling molecules is implicated in a
broad spectrum of disorders, including cardiovascular condi- tions (ie, acute coronary syndrome,1
stress cardiomyopathy,2
hyperhomocysteinemia,3
and preeclampsia).4
The enzyme
catechol-O-methyltransferase (COMT) modulates the func- tion of catecholamines. We wanted to confirm preliminary
evidence that genetic variation in COMT might affect suscepti- bly to cardiovascular disease (CVD).1,5–7 Aspirin is commonly
prescribed for CVD prevention. It is not known whether any
potential association of genetic variation in COMT with inci- dent CVD might be modified by aspirin treatment.
COMT degrades catecholamines by catalyzing the transfer
of a methyl group donated by S-adenosyl methionine onto
catechol moieties, resulting in their deactivation. The COMT
genetic variant rs4680 (val158met) is an extensively studied
© 2014 American Heart Association, Inc.
Arterioscler Thromb Vasc Biol is available at http://atvb.ahajournals.org DOI: 10.1161/ATVBAHA.114.303845
Objective—Catechol-O-methyltransferase (COMT), a key enzyme in catecholamine metabolism, is implicated in
cardiovascular, sympathetic, and endocrine pathways. This study aimed to confirm preliminary association of COMT
genetic variation with incident cardiovascular disease (CVD). It further aimed to evaluate whether aspirin, a commonly
used CVD prevention agent, modified the potential association of COMT with incident CVD.
Approach and Results—We examined COMT polymorphism rs4680 (MAF [minor allele frequency], 0.47), encoding a
nonsynonymous methionine-to-valine substitution, in the Women’s Genome Health Study (WGHS), a large population- based cohort of women with randomized allocation to aspirin or vitamin E when compared with placebo and 10-year
follow-up. Rs4680 effects were confirmed with COMT polymorphism rs4818 and also examined in Coronary ARtery
DIsease Genome-wide Replication and Meta-analysis/The Coronary Artery Disease Genetics Consortium, consortia for
genome-wide association studies of coronary artery disease. Among WGHS women allocated to placebo (135 events/
n=5811), the rs4680 valine allele was protective against incident CVD relative to the methionine (hazard ratio [HR;
95% confidence interval {CI}], 0.66 [0.51–0.84]; P=0.0007); an association also observed in Coronary ARtery DIsease
Genome-wide Replication and Meta-analysis and The Coronary Artery Disease Genetics Consortium (combined
P=2.4×10−5). In the WGHS, the rs4680 association was abolished by randomized allocation to aspirin, such that valine/
valine women experienced higher CVD rates with aspirin allocation when compared with placebo (HR [95% CI], 1.85
[1.05–3.25]; P=0.033), whereas methionine/methionine women experienced lower rates (HR [95% CI], 0.60 [0.39–0.93];
P=0.023). Allocation to vitamin E also conferred higher but nonsignificant CVD rates on valine/valine (HR [95% CI],
1.50 [0.83–2.70]; P=0.180) when compared with significantly lower rates on methionine/methionine (HR [95% CI], 0.53
[0.34–0.84]; P=0.006) women. Rs4818 results were similar.
Conclusions—Common COMT polymorphisms were associated with incident CVD, and this association was modified by
randomized allocation to aspirin or vitamin E. Replication of these findings is required. (Arterioscler Thromb Vasc Biol.
2014;34:2160-2167.)
Key Words: aspirin ◼ catecholamines ◼ vitamin E
Received on: April 20, 2014; final version accepted on: June 25, 2014.
From the Program in Placebo Studies, Division of General Medicine and Primary Care, Department of Medicine, Beth Israel Deaconess Medical
Center (K.T.H., R.B.D., I.K., T.J.K.), Division of Preventative Medicine, Brigham and Women’s Hospital (J.E.B., P.M.R., D.I.C.), and Department of
Medicine, Brigham and Women’s Hospital (J.L.), Harvard Medical School, Boston, MA (K.T.H., R.B.D., I.K., T.J.K, J.E.B., P.M.R., D.I.C, J.L., M.A.M.);
Department of Cardiovascular Sciences, Clinical Research Centre, Glenfield General Hospital, University of Leicester, Leicester, United Kingdom (C.P.N.,
N.J.S.); Department of Psychology, Plymouth University, Plymouth, United Kingdom (I.K.); and Cardiovascular Epidemiology Research Unit, Division of
Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School and Harvard School of Public Health Boston, MA (M.A.M.).
The online-only Data Supplement is available with this article at http://atvb.ahajournals.org/lookup/suppl/doi:10.1161/ATVBAHA.114.303845/-/DC1.
Correspondence to Kathryn T. Hall, PhD, MPH, Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, 1309 Beacon
St, Brookline, MA 02446. E-mail kthall@bidmc.harvard.edu
Polymorphisms in Catechol-O-Methyltransferase
Modify Treatment Effects of Aspirin on Risk
of Cardiovascular Disease
Kathryn T. Hall, Christopher P. Nelson, Roger B. Davis, Julie E. Buring, Irving Kirsch,
Murray A. Mittleman, Joseph Loscalzo, Nilesh J. Samani, Paul M Ridker, Ted J. Kaptchuk,
Daniel I. Chasman
Clinical and Population Studies
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Hall et al COMT Modifies Aspirin Cardiovascular Disease Effects 2161
single nucleotide polymorphism (SNP) that encodes a valine
(G)-to-methionine (A) substitution at amino acid 158 in the
membrane form and 108 in the secreted form of the enzyme.8
This functional polymorphism results in the methionine vari- ant having a 3- to 4-fold lower enzymatic activity than the
valine variant, and is, therefore, inversely correlated with
endogenous levels of dopamine9
and other COMT substrates,
both at rest and with exercise10 or at cardiac surgery-induced
stress.11 In addition, several small population-based stud- ies have found genetic variation in COMT to be associated
with coronary heart disease1
and hypertension in men.5–7 A
second COMT SNP, rs4818, is a C- to G-transversion in the
same exon as rs4680. Rs4818, in partial linkage disequilib- rium with rs4680, has been associated with differential stabil- ity of COMT mRNA secondary structure,12 as well as a series
of clinical outcomes some of which are shared with rs4680.13
Aspirin is the gold standard for antiplatelet therapy and is
widely prescribed because it is considered a safe treatment
for CVD prevention. Despite demonstrated benefit of aspirin
in primary and secondary CVD prevention,14,15 particularly
among men,16 the Women’s Health Study (WHS), a large pla- cebo-controlled trial (n=39876) of aspirin in primary preven- tion among initially healthy, middle-aged women found only
a 9% nonsignificant reduction of major CVD events when
compared with placebo ≥10 years of follow-up.17 Given that
aspirin like catecholamines18 interacts with multiple pathways
to affect CVD (eg, platelet activation), we hypothesized that
genetic variation in COMT might also affect response to aspi- rin treatment for prevention of major CVD. In the Women’s
Genome Health Study (WGHS),17,19,20 a subset of the WHS for
genome-wide genetic analysis, we therefore, performed a can- didate association study of COMT SNPs rs4680 and rs4818
for association with incident CVD and potential interaction
with randomized allocation to placebo or aspirin. The 2×2
factorial design of the WHS also allowed exploration of the
association of COMT and incident CVD in women randomly
allocated to vitamin E.
Materials and Methods
Materials and Methods are available in the online-only Supplement.
Results
The primary population for the study is the WGHS, a large pro- spective cohort for genetics of CVD derived from the WHS, a
randomized trial of aspirin and vitamin E when compared with
placebo in a balanced 2×2 factorial design. Random allocation
to aspirin or vitamin E in the WHS allowed exploration of the
association of genetic variation in COMT with incident CVD
in the 4 treatment arms: placebo plus placebo (n=5811), aspi- rin plus placebo (n=5810), vitamin E plus placebo (n=5856),
and aspirin plus vitamin E (n=5796; Methods in the online- only Data Supplement).
Demographics and baseline characteristics in this study
did not differ by treatment arm as expected by randomization
(Table I in the online-only Data Supplement). COMT SNPs
rs4680 (val158met) and rs4818 were found to be in Hardy
Weinberg equilibrium, and minor allele frequencies of rs4680
(G or valine) and rs4818 (G) were 0.47 and 0.39, respectively.
In the WGHS, the linkage disequilibrium between these SNPs
was moderate (r2
=0.70; D′=1.00).
Among WGHS participants allocated exclusively to pla- cebo (n=5811), there was a 34% lower age-adjusted incidence
rate of the primary outcome, major CVD, associated with
each additional valine allele in the COMT rs4680 (val158met)
polymorphism (hazard ratio [HR; 95% confidence interval
{CI}], 0.66 [0.51–0.84]; P=0.0007; Table 1; Figure 1). The
valine allele was also associated with a decreased rate of age- adjusted secondary outcomes of total CVD (HR [95% CI],
0.77 [0.63–0.93]; P=0.0075) and myocardial infarction (HR
[95% CI], 0.60 [0.41–0.90]; P=0.0130) but not of stroke (HR
[95% CI], 0.76 [0.53–1.09]; P=0.14) or coronary heart disease
(HR [95% CI], 0.81 [0.63–1.04]; P=0.103; Table 1; Figure 1).
The incident cardiovascular event rates associated with the
rs4818 minor allele among women allocated to the placebo
arm were similar to the rs4680 valine allele (Table 1; Figure I
in the online-only Data Supplement). Results were essentially
equivalent when Cox models were adjusted for standard risk
factors (age, systolic blood pressure, diastolic pressure, low- density lipoprotein-cholesterol, high-density lipoprotein-cho- lesterol, triglycerides, family history of myocardial infarction,
family history of diabetes mellitus, smoking history, and the
use of hormone replacement therapy; Table 1).
In Coronary ARtery DIsease Genome-wide Replication and
Meta-analysis (CARDIoGRAM),21 a large-scale meta-analy- sis of 13 studies consisting of 22 233 cases of coronary artery
disease (CAD), a composite including myocardial infarction,
revascularization, angina, and angiographic stenosis cases,
and 64762 controls, the rs4680 valine allele, was associated
with a decreased rate of CAD (odds ratio [95% CI], 0.960
[0.935–0.988]; P=0.0047; Table 2). Among the additional
and independent 34 CAD sample collections of The Coronary
Artery Disease Genetics Consortium (C4D),22 comprising
41513 cases and 65 919 controls of European or South Asian
ancestry, the association was also significant, with the valine
allele again conferring protection (odds ratio [95% CI], 0.964
[0.943–0.986]; P=0.0017). Overlapping CIs of the effect esti- mates in the sex stratified cohort suggested that there was
no significant difference between men and women (Table II
in the online-only Data Supplement). In a meta-analysis of
CARDIoGRAM plus C4D, the significance of the associa- tion was P=5.2×10−5. Despite the consistency of the risk allele
across all 3 studies, the evident heterogeneity in the COMT
SNP effect (ie, HR, 0.66 in WGHS [Table 1]; odds ratio, 0.96
Nonstandard Abbreviations and Acronyms
C4D The Coronary Artery Disease Genetics Consortium
CAD coronary artery disease
CARDIoGRAM Coronary ARtery DIsease Genome-wide Replication and
Meta-analysis
COMT catechol-O-methyltransferase
CVD cardiovascular disease
HR hazard ratio
SNP single nucleotide polymorphism
WGHS Women’s Genome Health Study
WHS Women’s Health Study
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2162 Arterioscler Thromb Vasc Biol September 2014
CARDiOGRAM; odds ratio, 0.96 C4D [Table 2]) precluded
the possibility of meta-analysis.
In the whole WGHS cohort, univariate analyses of rs4680
and 14 cardiovascular biomarkers measured at baseline23
revealed significant associations after correction for multiple
hypothesis testing (P≤0.004 [=0.05/14 risk factors]). At base- line, (log) triglycerides (β [SE], −0.018 [0.005]; P=0.0004)
and systolic blood pressure (β [SE], −0.367 [0.127] mmHg;
P=0.004) were significantly associated with the valine allele,
consistent with less cardiovascular risk for both risk factors
(Table III in the online-only Data Supplement). Similarly,
the minor allele of rs4818 was significant for (log) triglycer- ides (β [SE], −0.018 [0.005]; P=0.0004) and nominally sig- nificant for systolic blood pressure (β [SE], −0.335 [0.130]
mmHg; P=0.01), as well as apolipoprotein B (β [SE], −0.631
[0.282] μmol/L; P=0.025) and soluble intracellular adhe- sion molecule 1 (β [SE], −1.707 [0.837] μmol/L; P=0.041).
Despite these associations, rs4680 and rs4818 associations
with incident major CVD were essentially unaffected in Cox
models further adjusted by these risk factors (Table 1, fully
adjusted models and data not shown). COMT rs4680 associa- tions with triglycerides (P=0.028) and systolic blood pressure
(P=0.0059) were confirmed in published results from the
Global Lipids Genetics Consortium24 and the International
Consortium for Blood Pressure Genome-Wide Association
Studies,25 respectively.
The 2×2 design of the WGHS allowed us to evaluate how
random allocation to aspirin or vitamin E might influence the
association of COMT with incident CVD. Among WGHS
participants randomly allocated exclusively to aspirin, the
protective rs4680 valine allele association was not observed
(HR [95% CI], 1.13 [0.88–1.45]; P=0.34; Table 3; Figure 2A).
Comparison of these aspirin-allocated participants with those
randomly allocated exclusively to placebo revealed a signifi- cant interaction between rs4680 and aspirin (Pint=0.0022).
Similarly, random allocation exclusively to vitamin E also
abolished the association of rs4680 with incident CVD (HR
[95% CI], 1.08 [0.84–1.38]; P=0.52), revealing a significant
interaction of rs4680 with vitamin E allocation when com- pared with placebo-only allocation (Pint=0.004; Table 3;
Figure 2B). Results for rs4818 were similar (Table 3; Figure II
in the online-only Data Supplement).
The consequences of the aspirin and vitamin E alloca- tion on risk differed by rs4680 genotype. For COMT rs4680
methionine allele homozygotes, exclusive allocation to aspirin
or vitamin E compared with placebo resulted in age-adjusted
lower rates of incident CVD of 40% (95% CI, −7% to −61%;
P=0.023) and 47% (95% CI, −16% to −68%; P=0.006;
Table 4), respectively. In contrast, valine allele homozygotes
had higher CVD rates of 85% (95% CI, 5% to 325%; P=0.033)
and 50% (95% CI, −17% to 170%; P=0.18), respectively,
although only the aspirin allocation increase was significant.
Among heterozygotes, allocation to either aspirin or vitamin E
did not affect the incidence rate. For methionine allele homo- zygotes allocated to both aspirin and vitamin E, the difference
in rates compared with those allocated to placebo was not sig- nificant, implying a further interaction for allocation to both
agents compared with either alone. This further interaction was
Table 1. HR for Major CVD, Total CVD, CHD, Stroke, and MI by COMT SNPs rs4680
(val158met) and rs4818 Among Women Exclusively Allocated to Placebo
End Point* Events
HR [95% CI]; P Value
rs4680† rs4818†
Age-adjusted models n=5811 n=5795
Major CVD 135 0.66 [0.51–0.84]; 0.0007 0.67 [0.51–0.86]; 0.0022
Total CVD 204 0.77 [0.63–0.93]; 0.0075 0.70 [0.57–0.87]; 0.0010
CHD 126 0.81 [0.63–1.04]; 0.1030 0.69 [0.53–0.90]; 0.0068
Stroke 59 0.76 [0.53–1.09]; 0.1400 0·80 [0.55–1.17]; 0.2580
MI 53 0.60 [0.41–0.90]; 0.0130 0·59 [0.39–0.91]; 0.0162
Fully adjusted models‡ n=5136 n=5120
Major CVD 116 0.65 [0.50–0.85]; 0.0016 0.69 [0.52–0.91]; 0.0095
Total CVD 174 0.73 [0.59–0.91]; 0.0042 0.69 [0.55–0.87]; 0.0016
CHD 108 0.73 [0.56–0.96]; 0.0248 0.65 [0.38–0.87]; 0.0038
Stroke 50 0.76 [0.51–1.12]; 0.1669 0.79 [0.52–1.20]; 0.2764
MI 47 0.53 [0.35–0.82]; 0.0047 0.58 [0.37–0.91]; 0.0168
CI indicates confidence interval; CHD, coronary heart disease; CVD, cardiovascular disease; HR, hazard ratio;
and MI, myocardial infarction.
*Major CVD, the primary Women’s Health Study outcome is a composite of MI, stroke, or death from
cardiovascular causes. Total CVD, is a composite of revascularization procedures (percutaneous transluminal
coronary angioplasty and coronary bypass graft) in addition to events in the primary outcome. CHD is a composite
of nonfatal MI or fatal CHD plus revascularization procedures.
†rs4680 coded allele=G(val), reference allele=A(met); rs4818 coded allele=G, reference allele=C.
‡Fully adjusted Cox models were adjusted for standard cardiovascular risk factors: age, systolic blood pressure,
diastolic pressure, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglycerides, family
history of myocardial infarction, family history of diabetes mellitus, smoking, and the use of hormone replacement
therapy. Observations with incomplete data were not included in the analysis.
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Hall et al COMT Modifies Aspirin Cardiovascular Disease Effects 2163
significant (P=0.006; Table 4). Fully adjusted models revealed
similar effects except for diminished significance of the effect
of aspirin on methionine allele homozygotes (P=0.1, data not
shown). Results for rs4818 were similar (Table 4; Figure II in
the online-only Data Supplement).
Discussion
This is the first study to show a significant association of the
COMT rs4680 (val158met) polymorphism with incident CVD
in a population-based sample of women. The COMT valine
allele conferred a lower rate of events in the prospective setting
of the WGHS when compared with the methionine allele. The
association was significantly replicated in 2 additional stud- ies, CARDIoGRAM21 and C4D,26 and was also demonstrated
for the first time in any study with the COMT rs4818, a SNP
in partial linkage disequilibrium with rs4680. Furthermore,
we found that randomized allocation to aspirin eliminated the
COMT valine allele protective association with CVD, result- ing in an 85% increase in the rate of incident CVD for rs4680
valine allele homozygotes allocated to aspirin when compared
with placebo. Conversely, a 40% decrease in the rate of inci- dent CVD was observed for the methionine allele homozy- gotes allocated to aspirin when compared with that allocated
Figure 1. Kaplan–Meier estimates of the cumulative incidence of Women’s Genome Health Study women in the placebo arm (n=5811)
according to COMT rs4680 genotype with a first ever A, major cardiovascular disease (CVD), (B) total CVD, (C) myocardial infarction,
(D) ischemic stroke, (E) and coronary heart disease (CHD) event. Legends indicate genotype strata and number of cases/total number in
each stratum. met indicates methionine; and val, valine.
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2164 Arterioscler Thromb Vasc Biol September 2014
to placebo. Randomized allocation to vitamin E also modified
the COMT CVD association as a nonsignificant increase in
the rate of incident CVD in valine allele homozygotes when
compared with placebo and a significant 47% rate reduction
for the methionine allele homozygotes. Similar COMT effect
modification by both aspirin and vitamin E was observed for
another COMT SNP, rs4818.
The treatment effects described here resulting in a reduc- tion in the rate of incident CVD for the 28% of the WGHS
population that was homozygous for the methionine allele are
modest. Yet, over the ≈10 years of follow-up in the WGHS,
they translated into number-needed-to-treat estimates of 91
for aspirin or 74 for vitamin E as compared with 582 or 647,
respectively, for the population as a whole. Conversely, for
the 23% of the WGHS population that was homozygous for
the valine allele, where the drug effects were deleterious, the
number-needed-to-harm estimates were 91 for aspirin and 189
for vitamin E, although the effect of vitamin E was not sig- nificant. Our findings of differential CVD risk, thus, may be
interpreted in the context of personalized medicine in which
a subpopulation defined by COMT genotype would be identi- fied for potential benefit or harm by either of these treatments.
Several plausible catecholamine-mediated cardiovascular
functions could account for the cardiovascular protection we
observed in association with the high activity COMT valine
allele. COMT is present in platelets27 and in endothelial and
vascular smooth muscle cells,28 where the attenuated COMT
activity of methionine allele homozygotes could increase cat- echolamine flux and oxidant stress, thus lowering the threshold
for platelet activation and endothelial dysfunction. At the same
time, our findings that baseline biomarkers of cardiovascular
risk, including triglycerides, systolic blood pressure, soluble
intracellular adhesion molecule 1, and apolipoprotein B, were
associated with COMT SNPs suggest a potential pleiotropy
Table 2. Meta-Analysis of COMT-Associated CAD Protection in CARDIoGRAM, C4D, and CARDIoGRAM+C4D
SNP*
Stage 1†, CARDIoGRAM Stage 2‡, C4D Stage 3§, CARDIoGRAM+C4D
n OR [SE]; P Value n OR [SE]; P Value Fisher P Value P Value‖
rs4680 13 0.96 [0.014]; 0.0047 34 0.96 [0.012]; 0.0017 5.2×10−5 2.4×10−5
rs4818 9 0.96 [0.016]; 0.0081 NA NA NA NA
C4D indicates The Coronary Artery Disease Genetics Consortium; CAD, cardiovascular disease; CARDIoGRAM, Coronary ARtery DIsease
Genome-wide Replication and Meta-analysis; NA, not applicable; OR, odds ratio; and SNP, single nucleotide polymorphism.
*rs4680 coded allele=G(val), reference allele=A(met); rs4818 coded allele=G, reference allele=C; rs4818 was not available in Stage 2.
†Stage 1: CARDIoGRAM data set consisted of 22 233 CAD cases and 64 762 controls. CAD is a composite of myocardial infarction,
revascularization, angina, and angiographic stenosis.
‡Stage 2: Analysis of 34 additional CAD sample collections of European or South Asian descent (41 513 cases and 65 919 controls).
§Stage 3: Meta-analysis of CARDIoGRAM+C4D database.
‖Inverse variance P value.
Table 3. Age-Adjusted Cox Models Relating COMT rs4680 val Allele (met Allele as Reference)
and rs4818 G Allele Associations (C Allele as Reference) to Incident Major CVD and total CVD,
Stratified by Randomized Treatment Assignment
SNP* Outcome† Treatment Arm HR [95% CI]; P Value‡ Gene–drug Int. P Value§
rs4680 Major CVD Placebo‖ 0.66 [0.51–0.84]; 0.0007 ...
Aspirin only 1.13 [0.88–1.45]; 0.34 0.002
Vitamin E only 1.08 [0.84–1.38]; 0.52 0.004
Total CVD Placebo 0.77 [0.63–0.93]; 0.0075 ...
Aspirin only 1.10 [0.90–1.40]; 0.23 0.011
Vitamin E only 1.09 [0.90–1.32]; 0.38 0.011
rs4818 Major CVD Placebo 0.67 [0.51–0.86]; 0.0022 ...
Aspirin only 1.22 [0.95–1.56]; 0.11 0.0009
Vitamin E only 1.03 [0.80–1.32]; 0.80 0.016
Total CVD Placebo 0.70 [0.57–0.87]; 0.001 ...
Aspirin only 1.14 [0.93–1.40]; 0.20 0.001
Vitamin E only 1.06 [0.87–1.29]; 0.57 0.005
CI indicates confidence interval; CVD, cardiovascular disease; HR, hazard ratio; and SNP, single nucleotide polymorphism.
*rs4680 coded allele=G(val), reference allele=A(met); rs4818 coded allele=G, reference allele=C.
†Major CVD, the primary Women’s Health Study outcome is a composite of myocardial infarction, stroke, or death from
cardiovascular causes. Total CVD is a composite of revascularization procedures (percutaneous transluminal coronary
angioplasty and coronary bypass graft), in addition to events in the primary outcome.
‡HRs refer to SNP associations with incident CVD in designated treatment arms.
§Gene–drug interaction P value refers to the significance of the difference between the SNP association among placebo
allocated Women’s Genome Health Study participants and participants allocated to the designated treatment arm.
‖Placebo results are also reported in Table 1.
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Hall et al COMT Modifies Aspirin Cardiovascular Disease Effects 2165
of COMT effects in the pathophysiology underlying its asso- ciation with incident CVD. In addition to these associated
mechanisms, COMT activity may be modified by plasma
homocysteine concentrations, thereby potentiating the adverse
effects of hyperhomocysteinemia by decreasing catecholamine
O-methylation and inactivation: elevated levels of homocyste- ine lead to an increase in S-adenosylhomocysteine, which is a
noncompetitive inhibitor of COMT.3
Evidence for the effects
of this theoretical interaction between COMT activity and
homocysteine levels was demonstrated in the Kuopio Ischemic
Heart Disease Risk Factor Study,1
as well as studies of venous
thrombosis risk29 and preeclampsia.30 Interestingly, a recent
trial that examined the effect of aspirin on hyperhomocystein- emia also reported effect modification of aspirin inhibition of
platelet aggregation by homocysteine level.31
How aspirin modifies CVD protection associated with
COMT is not known, but candidate mechanisms include
effects on platelet function or homocysteine levels and may
support the hypothesis that differential response to aspirin
therapy in a variety of settings is a heritable trait.32,33 Such
genetic effects on aspirin response have precedent in our pre- vious finding that carriers of an apolipoprotein(a) gene variant
had a doubling of incident CVD rate and seemed to benefit
more from aspirin therapy than noncarriers.34
In principle, the lack of an overall effect of vitamin E on
CVD risk in the original WHS report19 does not preclude
the possibility that subgroups defined on the basis of genetic
strata experience benefit or harm, such as implied by the novel
associations reported here. The underlying mechanisms of
the COMT–drug interactions are yet to be elucidated. Recent
data showing platelet COMT-mediated methylation-dependent
inactivation of the common dietary antioxidant, quercetin,35
may be indicative of a potential mechanism by which vitamin
E effects may also depend on COMT genotype and activity.
The COMT interaction with vitamin E is hypothesis generat- ing and may potentially offer some insight into the conflicting
observations between animal and in vitro studies36 that sup- port a role for vitamin E in minimizing cardiovascular risk and
overall null findings in CVD trials.19 Thus, mechanistic studies
that could account for this differential aspirin and vitamin E
treatment effect by genotype are warranted and may include
analyses of platelet and vascular cell prostanoid and eicosanoid
metabolism, oxidant stress, nitric oxide signaling, and plate- let and endothelial function assessment over a wider range of
doses. Moreover, the results suggest that any future studies
Table 4. Age-Adjusted Cox Models of Major CVD* Stratified by COMT SNP Genotype Within the 3 Drug
Treatment Arms Compared With the Placebo Allocated Arm (Reference)
Treatment Arm (HR [95% CI]; P Value)†
Genotype Stratum Placebo Aspirin Only Vitamin E Only Aspirin+Vitamin E Drug Int. P Value‡
rs4680
met/met ref. 0.60 [0.39–0.93], 0.02 0.53 [0.34–0.84], 0.006 0.80 [0.53–1.21], 0.30 0.006
val/met ref. 0.89 [0.63–1.27], 0.52 1.06 [0.76–1.49], 0.73 0.91 [0.64–1.29], 0.58 0.85
val/val ref. 1.85 [1.05–3.25], 0.03 1.50 [0.83–2.70], 0.18 1.54 [0.87–2.74], 0.14 0.15
rs4818
C/C ref. 0.69 [0.47–1.00], 0.05 0.67 [0.46–0.98], 0.04 0.77 [0.53–1.12], 0.17 0.08
G/C ref. 0.81 [0.56–1.18], 0.28 1.04 [0.73–1.47], 0.85 1.02 [0.72–1.46], 0.89 0.44
G/G ref. 2.98 [1.45–6.09], 0.003 1.81 [0.84–3.93], 0.13 1.67 [0.77–3.63], 0.19 0.02
CI indicates confidence interval; CVD, cardiovascular disease; HR, hazard ratio; met, methionine; SNP, single nucleotide polymorphism; and
val, valine.
*Major CVD, the primary Women’s Health Study outcome is a composite of myocardial infarction, stroke, or death from cardiovascular causes.
†HR [95% CI] and P value for each genotype by drug strata relative to placebo in age-adjusted models.
‡Drug interaction P value for interaction of aspirin and vitamin E across all three drug allocations within each SNP genotype stratum relative
to placebo.
Figure 2. Kaplan–Meier estimates of the cumulative incidence
of Women’s Genome Health Study women according to COMT
rs4680 genotype with a first ever major cardiovascular disease
(CVD) event in the (A) aspirin vs placebo arms, and (B) vitamin E
vs placebo arms. P values are for the whole model and interac- tion P values are for the drug by genotype interaction terms.
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2166 Arterioscler Thromb Vasc Biol September 2014
exploring aspirin or vitamin E treatment in disease prevention
or therapy should be mindful of COMT genotype and other
genetic variation in the catecholamine metabolic pathway.
More broadly, the results illustrate how gene–drug interactions
may influence the interpretation of a major clinical trial.
The strengths of our study are the prospective and homo- geneous nature of the WGHS cohort, the validation of cardio- vascular end points by physician review of medical records,
the randomized allocation of WGHS participants to aspi- rin or vitamin E, and the replication of the COMT rs4680
association with CVD rate in CARDIoGRAM and C4D. In
addition, our inclusion of another directly genotyped SNP,
rs4818, provided a mutually confirmatory safeguard against
artifacts caused by genotyping errors. Despite the epidemio- logical strengths of the WGHS in support of the association
with rs4680, the effect in CARDIoGRAM was weaker than
expected given its much larger number of cases, and under- standing this discrepancy may be revealing for the mechanism
of COMT action. In this regard, it may be relevant to note
differences between the WGHS and CARDIoGRAM/C4D in
CVD end point definitions and population composition. There
were a variety of CVD end points in the studies contributing to
the CARDIoGRAM/C4D meta-analysis that focused on cases
of CAD, a composite including myocardial infarction, revas- cularization, angina, and angiographic stenosis, but variously
recruited with or without additional criteria related to age and
family history.37 The studies in C4D similarly included cases
recruited for a variety of CAD definitions, including angina,
and also recruited from both South Asian and European popu- lations,22 a strategy that may have introduced subtle hetero- geneity (eg, from environmental interactions) and that could
have degraded power of already weak associations. In con- trast, the primary end point in the WGHS was major CVD,
a composite of nonfatal myocardial infarction or stroke, or
cardiovascular death, and the population had homogeneous
European ancestry. A secondary end point in the WGHS, cor- onary heart disease, defined as myocardial infarction or coro- nary revascularization but not angina, is somewhat closer to
the CAD used by CARDIoGRAM/C4D and had a less strong
association with rs4680 in the WGHS than the primary major
CVD outcome. The differences appear not to reflect a sex-spe- cific effect because, although CARDIoGRAM included both
men and women (in contrast to the all-female composition
of the WGHS), there was no evidence for rs4680 differential
effects according to sex. Moreover, the association between
rs4680 and CVD is consistent with results from the Kuopio
Ischemic Heart Disease Study, where there was a significant
association of methionine homozygotes when compared with
valine carriers among 69 acute coronary events in a popula- tion of 792 men.1
Another possible explanation might be
related to the interactions we observed with aspirin and vita- min E. Exposures to these common drugs and others that may
abrogate the COMT rs4680 association with CAD were not
recorded in CARDIoGRAM/C4D but may have nevertheless
contributed to the weaker association observed in this study.
Genetic analysis offers 1 route to a deeper understanding
of the underlying pathophysiology of CVD. Our findings of
a robust association between COMT variation and incident
CVD add to a range of other clinical outcomes influenced by
the catecholamine pathway. Finally, the modulation of CVD
risk conferred by COMT through random allocation to aspirin
and vitamin E may have implications for personalized medi- cine and development of strategies in attenuating CVD risk.
Acknowledgments
We thank Valerie Stone, Christina Wee, Karin Jansen, Dale Abel, and
James Meigs for helpful discussions.
Sources of Funding
The Women's Genome Health Study is supported by HL043851 and
HL080467 from the National Heart, Lung, and Blood Institute and CA
047988 from the National Cancer Institute, and the Donald W. Reynolds
Foundation, with collaborative scientific support and funding for geno- typing provided by Amgen. Drs Hall and Kaptchuk are supported by
National Center for Complementary and Alternative Medicine-National
Institutes of Health (NIH) grants T32AT000051, R01AT004662,
K24AT004095, R21AT002860, and 3R01AT004662-02S1. Drs Davis
and Mittleman are supported by Harvard Catalyst through NIH award
UL1 RR 025758 and financial contributions from Harvard University
and its affiliated academic healthcare centers. The content is solely the
responsibility of the authors and does not necessarily represent the offi- cial views of Harvard Catalyst, Harvard University and its affiliated aca- demic healthcare centers, the National Center for Research Resources,
or the NIH. No funding sources contributed to the design and conduct
of the study; collection, management, analysis, and interpretation of the
data and preparation, review, or approval of the article.
Disclosures
Drs Hall and Kaptchuk are scientific advisors to Biometheus, LLC.
The other authprs report no conflicts.
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Preliminary evidence suggests that genetic variation in the gene encoding catechol-O-methyltransferase (COMT) is associated with cardio- vascular disease (CVD). It is not known whether potential association of genetic variation in COMT with incident CVD is further modified by
aspirin. In the Women’s Genome Health Study (N=23 294), a large population-based prospective cohort of women with randomized alloca- tion to aspirin or vitamin E compared with placebo, we reinforce preliminary evidence for COMT association with incident CVD ≥10 years of
follow-up. We further demonstrate modification of this association by randomization to aspirin and vitamin E, such that individuals with some
COMT genotypes had significantly higher rates of incident CVD by allocation to drug. Given that aspirin is widely prescribed and that the COMT
target genetic variant described here is common (MAF [minor allele frequency], 47%), this study underscores the importance of adapting
a pharmacogenetic approach to understanding and treating underlying CVD pathophysiology. These results also illustrate how gene–drug
interactions can influence interpretation of major clinical trials.
Significance
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