Association of gene variants with incident myocardial infarction in the Cardiovascular Health Study

Genetic variants in the KIF6 region and coronary event reduction from statin therapy

A single nucleotide polymorphism (SNP) in KIF6, a member of the KIF9 family of kinesins, is associated with differential coronary event reduction from statin therapy in four randomized controlled trials; this SNP (rs20455) is also associated with the risk for coronary heart disease (CHD) in multiple prospective studies. We investigated whether other common SNPs in the KIF6 region were associated with event reduction from statin therapy. Of the 170 SNPs in the KIF6 region investigated in the Cholesterol and Recurrent Events trial (CARE), 28 were associated with differential event reduction from statin therapy (P_interaction < 0.1 in Caucasians, adjusted for age and sex) and were further investigated in the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis In Myocardial Infarction 22 (PROVE IT-TIMI22) and West of Scotland Coronary Prevention Study (WOSCOPS). These analyses revealed that two SNPs (rs9462535 and rs9471077), in addition to rs20455, were associated with event reduction from statin therapy (P_interaction < 0.1 in each of the three studies). The relative risk reduction ranged from 37 to 50% (P < 0.01) in carriers of the minor alleles of these SNPs and from −4 to 13% (P > 0.4) in non-carriers. These three SNPs are in high linkage disequilibrium with one another (r² > 0.84). Functional studies of these variants may help to understand the role of KIF6 in the pathogenesis of CHD and differential response to statin therapy.

Investigation of KIF6 Trp719Arg in a case-control study of myocardial infarction: a Costa Rican population

Background and Methodology

The 719Arg allele of KIF6 (rs20455) was associated with coronary events in Caucasian participants of five prospective studies. We investigated whether this KIF6 variant was associated with non-fatal myocardial infarction (MI) in a case-control study of an admixed population from the Central Valley of Costa Rica. Genotypes of the KIF6 variant were determined for 4,134 men and women. Cases (1,987) had survived a first MI; controls (2,147) had no history of MI and were matched to cases by age, sex, and area of residence. We tested the association between the KIF6 719Arg allele and non-fatal MI by conditional logistic regression and adjusted for admixture of founder populations.

Principal Findings

Compared with the reference Trp/Trp homozygotes, KIF6 719Arg carriers were not at significantly higher risk for non-fatal MI in this study after adjustment for traditional risk factors or admixture (OR = 1.12; 95%CI, 0.98–1.28). Heterozygotes of the KIF6 Trp719Arg variant were at increased risk of non-fatal MI: the adjusted odds ratio was 1.16 (95% confidence interval, 1.01–1.34), but this association would not be significant after a multiple testing correction.

Conclusions/Significance

We found that carriers of the KIF6 719Arg allele were not at increased risk of non-fatal MI in a case-control study of Costa Ricans living in the Central Valley of Costa Rica.

Vegetable Intake in College-Aged Adults Is Explained by Oral Sensory Phenotypes and TAS2R38 Genotype

Taste and oral sensations vary in humans. Some of this variation has a genetic basis, and two commonly measured phenotypes are the bitterness of propylthiouracil (PROP) and the number of fungiform papillae on the anterior tongue. While the genetic control of fungiform papilla is unclear, PROP bitterness associates with allelic variation in the taste receptor gene, TAS2R38. The two common alleles are AVI and PAV (proline, alanine, valine, and isoleucine); AVI/AVI homozygotes taste PROP as less bitter than heterozygous or homozygous PAV carriers. In this laboratory-based study, we determined whether taste of a bitter probe (quinine) and vegetable intake varied by taste phenotypes and TAS2R38 genotype in healthy adults (mean age=26 years). Vegetable intake was assessed via two validated, complementary methods: food records (Food Pyramid servings standardized to energy intake) and food frequency questionnaire (general intake question and composite vegetable groups). Quinine bitterness varied with phenotypes but not TAS2R38; quinine was more bitter to those who tasted PROP as more bitter or had more papillae. Nontasters by phenotype or genotype reported greater consumption of vegetables, regardless of type (i.e., the effect generalized to all vegetables and was not restricted to those typically thought of as being bitter). Furthermore, nontasters with more papillae reported greater vegetable consumption than nontasters with fewer papillae, suggesting that when bitterness does not predominate, more papillae enhance vegetable liking. These findings suggest that genetic variation in taste, measured by multiple phenotypes or TAS2R38 genotype, can explain differences in overall consumption of vegetables, and this was not restricted to vegetables that are predominantly bitter.

Changes in lipoprotein(a), oxidized phospholipids, and LDL subclasses with a low-fat high-carbohydrate diet

Low-fat diets have been shown to increase plasma concentrations of lipoprotein(a) [Lp(a)], a preferential lipoprotein carrier of oxidized phospholipids (OxPLs) in plasma, as well as small dense LDL particles. We sought to determine whether increases in plasma Lp(a) induced by a low-fat high-carbohydrate (LFHC) diet are related to changes in OxPL and LDL subclasses. We studied 63 healthy subjects after 4 weeks of consuming, in random order, a high-fat low-carbohydrate (HFLC) diet and a LFHC diet. Plasma concentrations of Lp(a) (P < 0.01), OxPL/apolipoprotein (apo)B (P < 0.005), and OxPL-apo(a) (P < 0.05) were significantly higher on the LFHC diet compared with the HFLC diet whereas LDL peak particle size was significantly smaller (P < 0.0001). Diet-induced changes in Lp(a) were strongly correlated with changes in OxPL/apoB (P < 0.0001). The increases in plasma Lp(a) levels after the LFHC diet were also correlated with decreases in medium LDL particles (P < 0.01) and increases in very small LDL particles (P < 0.05). These results demonstrate that induction of increased levels of Lp(a) by an LFHC diet is associated with increases in OxPLs and with changes in LDL subclass distribution that may reflect altered metabolism of Lp(a) particles.

Effect of pravastatin therapy on coronary events in carriers of the KIF6 719Arg allele from the cholesterol and recurrent events trial

A previous genetic analysis of the Cholesterol and Recurrent Events (CARE) trial found that carriers of the 719Arg allele of the kinesin family member 6 gene (KIF6) (rs20455), but not noncarriers, received significant event reduction from pravastatin therapy. However, that previous analysis of CARE included only Caucasian patients and was limited to the myocardial infarction components of the primary end point. Therefore, the aim of this study was to investigate whether pravastatin therapy reduced primary end point events in KIF6 719Arg carriers and noncarriers, separately, in the combined ethnic groups of CARE. The effect of pravastatin therapy on primary end point events (fatal coronary event or nonfatal myocardial infarction) was investigated in Cox regression models that adjusted for population structure using either self-reported ethnicity or the principal components of genetic heterogeneity. After adjustment for age, gender, and self-reported ethnicity, pravastatin therapy reduced events in carriers of KIF6 719Arg (hazard ratio [HR] 0.63, 95% confidence interval [CI] 0.49 to 0.83) but not in noncarriers (HR 1.01, 95% CI 0.69 to 1.45) (p for interaction = 0.049). After adjustment for age, gender, traditional risk factors, and principal components, pravastatin therapy reduced events in carriers of 719Arg (HR 0.64, 95% CI 0.49 to 0.85) but not in noncarriers (HR 0.90, 95% CI 0.62 to 1.32) (p for interaction = 0.14). In conclusion, in an analysis that included CARE patients of all ethnic groups, pravastatin therapy significantly and substantially reduced primary end point events in carriers of the KIF6 719Arg allele but not in noncarriers.

VAMP8/endobrevin is overexpressed in hyperreactive human platelets: suggested role for platelet microRNA

BACKGROUND

Variation in platelet reactivity contributes to disorders of hemostasis and thrombosis, but the molecular mechanisms are not well understood.

OBJECTIVES

To discover associations between interindividual platelet variability and the responsible platelet genes, and to begin to define the molecular mechanisms altering platelet gene expression.

SUBJECTS/METHODS

Two hundred and eighty-eight healthy subjects were phenotyped for platelet responsiveness. Platelet RNA from subjects demonstrating hyperreactivity (n=18) and hyporeactivity (n=11) was used to screen the human transcriptome.

RESULTS

Distinctly different mRNA profiles were observed between subjects with differing platelet reactivity. Increased levels of mRNA for VAMP8/endobrevin, a critical v-SNARE involved in platelet granule secretion, were associated with platelet hyperreactivity (Q=0.0275). Validation studies of microarray results showed 4.8-fold higher mean VAMP8 mRNA levels in hyperreactive than hyporeactive platelets (P=0.0023). VAMP8 protein levels varied 13-fold among platelets from these normal subjects, and were 2.5-fold higher in hyperreactive platelets (P=0.05). Among our cohort of 288 subjects, a VAMP8 single-nucleotide polymorphism (rs1010) was associated with platelet reactivity in an age-dependent manner (P<0.003). MicroRNA-96 was predicted to bind to the 3'-untranslated regionof VAMP8 mRNA and was detected in platelets. Overexpression of microRNA-96 in VAMP8-expressing cell lines caused a dose-dependent decrease in VAMP8 protein and mRNA, suggesting a role in VAMP8 mRNA degradation.

CONCLUSIONS

These findings support a role for VAMP8/endobrevin in the heterogeneity of platelet reactivity, and suggest a role for microRNA-96 in the regulation of VAMP8 expression.

Comprehensive Analysis of Genomic Variation in the LPA Locus and Its Relationship to Plasma Lipoprotein(a) in South Asians, Chinese, and European Caucasians

Background— Functional copy number variation in the apolipoprotein(a) gene ( LPA ) underlies a variable number of protein kringle domains repeated in tandem in the lipoprotein(a) [Lp(a)] particle. Genomic analysis of LPA , including both single-nucleotide polymorphisms (SNPs) and kringle IV type 2 (KIV-2) copy number, has yet to be performed.

Methods and Results— First, we genotyped 49 SNPs within 100 kb of LPA in a multiethnic sample comprising South Asians (n=330), Chinese (n=304), and European Caucasians (n=272). Second, using quantitative polymerase chain reaction, we estimated the KIV-2 copy number in each sample. European Caucasians had the lowest KIV-2 copy number but displayed the strongest correlation between KIV-2 copy number and plasma Lp(a) concentration ( r s =−0.31, P =4.2�10 −7 ). SNP rs10455872, only prevalent in European Caucasians, was strongly associated with both plasma Lp(a) concentration ( P =4.2�10 −29 ) and KIV-2 copy number ( P =7.2�10 −5 ). LPA SNP rs6415084, within the same haplotype block as the KIV-2 variation, was significantly associated with both Lp(a) concentration and KIV-2 copy number in the same direction in all 3 ethnicities [Lp(a), P =5.3�10 −7 ; KIV-2, P =2.6�10 −4 ]. SNPs and KIV-2 copy number together explain a larger proportion of variation in plasma Lp(a) concentrations in European Caucasians (36%) than in Chinese (27%) or South Asians (21%).

Conclusions— LPA SNPs are in linkage disequilibrium with KIV-2 copy number, but KIV-2 copy number explains an increment in plasma Lp(a) variation over SNPs alone. Thus, both SNPs and KIV-2 copy number should be included in future genetic epidemiology studies of Lp(a).

Lipoprotein(a) and ischemic heart disease--a causal association? A review

The aim of this review is to summarize present evidence of a causal association of lipoprotein(a) with risk of ischemic heart disease (IHD). Evidence for causality includes reproducible associations of a proposed risk factor with risk of disease in epidemiological studies, evidence from in vitro and animal studies in support of pathophysiological effects of the risk factor, and preferably evidence from randomized clinical trials documenting reduced morbidity in response to interventions targeting the risk factor. Elevated and in particular extreme lipoprotein(a) levels have in prospective studies repeatedly been associated with increased risk of IHD, although results from early studies are inconsistent. Data from in vitro and animal studies implicate lipoprotein(a), consisting of a low density lipoprotein particle covalently bound to the plasminogen-like glycoprotein apolipoprotein(a), in both atherosclerosis and thrombosis, including accumulation of lipoprotein(a) in atherosclerotic plaques and attenuation of t-PA mediated plasminogen activation. No randomized clinical trial of the effect of lowering lipoprotein(a) levels on IHD prevention has ever been conducted. Lacking evidence from randomized clinical trials, genetic studies, such as Mendelian randomization studies, can also support claims of causality. Levels of lipoprotein(a) are primarily determined by variation in the LPA gene coding for the apolipoprotein(a) moiety of lipoprotein(a), and genetic epidemiologic studies have documented association of LPA copy number variants, influencing levels of lipoprotein(a), with risk of IHD. In conclusion, results from epidemiologic, in vitro, animal, and genetic epidemiologic studies support a causal association of lipoprotein(a) with risk of IHD, while results from randomized clinical trials are presently lacking.

Forty-three loci associated with plasma lipoprotein size, concentration, and cholesterol content in genome-wide analysis

While conventional LDL-C, HDL-C, and triglyceride measurements reflect aggregate properties of plasma lipoprotein fractions, NMR-based measurements more accurately reflect lipoprotein particle concentrations according to class (LDL, HDL, and VLDL) and particle size (small, medium, and large). The concentrations of these lipoprotein sub-fractions may be related to risk of cardiovascular disease and related metabolic disorders. We performed a genome-wide association study of 17 lipoprotein measures determined by NMR together with LDL-C, HDL-C, triglycerides, ApoA1, and ApoB in 17,296 women from the Women's Genome Health Study (WGHS). Among 36 loci with genome-wide significance (P<5×10⁻⁸) in primary and secondary analysis, ten (PCCB/STAG1 (3q22.3), GMPR/MYLIP (6p22.3), BTNL2 (6p21.32), KLF14 (7q32.2), 8p23.1, JMJD1C (10q21.3), SBF2 (11p15.4), 12q23.2, CCDC92/DNAH10/ZNF664 (12q24.31.B), and WIPI1 (17q24.2)) have not been reported in prior genome-wide association studies for plasma lipid concentration. Associations with mean lipoprotein particle size but not cholesterol content were found for LDL at four loci (7q11.23, LPL (8p21.3), 12q24.31.B, and LIPG (18q21.1)) and for HDL at one locus (GCKR (2p23.3)). In addition, genetic determinants of total IDL and total VLDL concentration were found at many loci, most strongly at LIPC (15q22.1) and APOC-APOE complex (19q13.32), respectively. Associations at seven more loci previously known for effects on conventional plasma lipid measures reveal additional genetic influences on lipoprotein profiles and bring the total number of loci to 43. Thus, genome-wide associations identified novel loci involved with lipoprotein metabolism—including loci that affect the NMR-based measures of concentration or size of LDL, HDL, and VLDL particles—all characteristics of lipoprotein profiles that may impact disease risk but are not available by conventional assay.

Genome-wide association studies (GWAS) of plasma lipoprotein fractions hold great promise for understanding lipid metabolism and its central role in cardiovascular disease and related disorders. Conventional assays for lipoprotein status determine total cholesterol content of low- or high-density lipoprotein particles (LDL-C or HDL-C, respectively) or total plasma triglyceride content (as an estimate of very-low density lipoprotein particle concentration [VLDL]). All three measures have been targets for recent GWAS. However, a more precise target for GWAS of lipoprotein metabolism would be the concentration of the individual lipoprotein particles according to class (LDL, HDL, VLDL) and size (small, medium, and large), all of which can be measured by NMR-based methods. In a population of 17,296 women of European ancestry from the Women's Genome Health Study, we have performed a GWAS for 22 lipoprotein measures derived from NMR-based and conventional assays. We find 43 genetic loci involved in lipoprotein metabolism, including 10 novel loci. The results offer a clearer picture of common genetic influences on lipoprotein metabolism than available previously, including genetic effects on the distribution of LDL, HDL, and VLDL particle size, as well as on IDL and VLDL particle concentration, neither of which can be assessed by conventional measures.

Genetic determinants of response to statins

In developed countries, cardiovascular disease is one of the leading causes of death. Statins are abundantly prescribed to reduce the risk of coronary artery disease by lowering cholesterol. Genetic factors are thought to be partly responsible for the interindividual variation in the response to statins. This article reviews the most important studies conducted on pharmacogenetics of statins. Currently, there is no evidence to advocate pharmacogenetic testing before initiating therapy.

Genomic view of factors leading to plaque instability

The manifestations of coronary artery disease are varied. They all arise as a consequence of the deposition of atherosclerotic plaque within the vessel wall. The most feared sequela of coronary artery disease is sudden and unexpected death in the ostensibly healthy patient. Plaque rupture of hemodynamically insignificant atherosclerotic plaques and ensuing thrombosis is likely responsible for a large proportion of such deaths. Identifying populations at increased risk for sudden death would represent a major advance. Such screening is contingent upon identification of DNA sequence variants that predispose individuals to plaque rupture. Phenotyping is not sufficiently nuanced to detect such variants on a large scale, so we are limited to end points that are crude surrogates for plaque rupture. As imaging modalities are refined and our ability to recruit large numbers of appropriate patients is facilitated by the formation of alliances, our ability to probe this conundrum via a genome-wide approach will improve.

Surveying food and beverage liking: a tool for epidemiological studies to connect chemosensation with health outcomes

Genetics, environmental exposures, and aging interact to produce variations in the perception or liking of taste, olfaction, and somatosensory sensations (i.e., chemosensation). Chemosensory variation can affect disease risk by influencing what people like and choose to eat from abundant supplies of desirable high-fat, sweet, and salty foods and alcoholic beverages at the expense of less-available or less-liked vegetables. We contend that assessing dietary preference via liking-disliking surveys holds promise for linking chemosensation with dietary intake and health outcomes in population-based studies. Typical intake measures (e.g., frequency surveys, dietary records) are difficult to complete and interpret. Because of memory issues and dietary restraint, individuals under- or overreport intakes, leading to inaccurate conclusions about diet-disease relationships. Surveying food and beverage liking is a time-efficient, simple task that minimizes the cognitive limitations of intake measures. In the present study, women in a worksite health risk appraisal completed brief food frequency and liking surveys and reported their height and weight, and blood pressure was measured. While liking and intake measures for high-fat and high-fiber foods were correlated, only liking was associated with disease risk. In multiple regression models, women reporting greater liking for high-fat foods and less liking for spicy foods had greater adiposity and/or blood pressure, controlling for age. These data, along with previous laboratory and community-based studies, support that reported liking of high-fat foods explains variability in adiposity and adiposity-related outcomes. Hedonic measures appear to capture habitual intake of foods and beverages, are easy to implement in the field, and thus may increase understanding of how chemosensory variation modifies disease risk.

Variations of specific non-candidate genes and risk of myocardial infarction: a replication study

BACKGROUND

A recent survey of 11,053 single nucleotide polymorphisms from 6891 genes suggested that the risk of myocardial infarction was related to specific genes so far not linked with atherosclerotic diseases. The genes encode the cytoskeletal protein palladin (PALLD), a receptor tyrosine kinase (ROS1), a taste receptor (TAS2R50), an olfactory receptor (OR13G1), and a zinc finger protein (ZNF627).

METHODS

We examined the polymorphisms rs12510359 (PALLD), rs619203 (ROS1), rs1376251 (TAS2R50), rs1151640 (OR13G1), and rs4804611 (ZNF627) which were found to be associated with myocardial infarction in the original report. The present study sample consisted of 3657 patients with myocardial infarction (885 women and 2772 men) and 1211 control individuals (598 women and 613 men).

RESULTS

The frequencies of genotypes and alleles were not significantly different between the group with myocardial infarction and the control group (p ≥ 0.25). In addition, genotype distributions were not substantially different between the women in the group with myocardial infarction and the control group (p ≥ 0.30) and between the men in the two groups (p ≥ 0.27). Finally, no risk genotypes were ascertained in multiple logistic regression analyses that included conventional risk factors of atherosclerosis as covariates (p≥0.26).

CONCLUSIONS

The results obtained in this study argue against associations of specific single nucleotide polymorphisms in the PALLD, ROS1, TAS2R50, OR13G1, and ZNF627 genes with myocardial infarction.

Creating a genetic risk score for coronary artery disease

Coronary artery disease (CAD) and its sequelae represent a significant health burden. Over the past two decades, numerous studies have attempted to link DNA sequence variation with the risk of CAD and related phenotypes. There has been significant evolution in technology from the early linkage studies within kindreds, and now we are able to use high-density genotyping to facilitate large-scale genome-wide association studies. The first novel genetic risk factor for CAD, 9p21.3, has been confirmed, and other loci are awaiting replication studies. The relative importance of each locus from a global standpoint and the incremental information conferred by testing for genetic variants remain to be determined.

Factor V Leiden and thrombosis in patients with systemic lupus erythematosus: a meta-analysis

To perform a meta-analysis of the association between the factor V Leiden polymorphism (FVL) and thrombosis among patients with SLE and/or antiphospholipid antibody (aPL) positivity. Included studies recruited patients based on SLE or aPL positive status, confirmed subjects' SLE diagnosis as defined by the American College of Rheumatology, and documented thrombotic events. Excluded studies were non-English or considered only arterial thrombosis. Individual patient data, available from five studies, together with unpublished data from 1210 European-American SLE patients from the UCSF Lupus Genetics Collection genotyped for FVL, were further analyzed. Seventeen studies (n=2090 subjects) were included in the initial meta-analysis. Unadjusted odds ratios (OR) were calculated to assess association of FVL with thrombosis. The OR for association of thrombosis with FVL was 2.88 (95% C.I. 1.98-4.20). In the secondary analysis with our individual patient dataset (n=1447 European-derived individuals), SLE subjects with the FVL polymorphism still had more than two times the odds of thrombosis compared to subjects without this polymorphism, even when adjusting for covariates such as gender, age, and aPL status. SLE and/or aPL positive patients with the FVL variant have more than two times the odds of thrombosis compared to those without this polymorphism.

Genetic variation in taste and its influence on food selection

Abstract Taste perception plays a key role in determining individual food preferences and dietary habits. Individual differences in bitter, sweet, umami, sour, or salty taste perception may influence dietary habits, affecting nutritional status and nutrition-related chronic disease risk. In addition to these traditional taste modalities there is growing evidence that "fat taste" may represent a sixth modality. Several taste receptors have been identified within taste cell membranes on the surface of the tongue, and they include the T2R family of bitter taste receptors, the T1R receptors associated with sweet and umami taste perception, the ion channels PKD1L3 and PKD2L1 linked to sour taste, and the integral membrane protein CD36, which is a putative "fat taste" receptor. Additionally, epithelial sodium channels and a vanilloid receptor, TRPV1, may account for salty taste perception. Common polymorphisms in genes involved in taste perception may account for some of the interindividual differences in food preferences and dietary habits within and between populations. This variability could affect food choices and dietary habits, which may influence nutritional and health status and the risk of chronic disease. This review will summarize the present state of knowledge of the genetic variation in taste, and how such variation might influence food intake behaviors.

F9 Malmö, factor IX and deep vein thrombosis

BACKGROUND

We recently reported the association between the Malmö sequence variant in F9 (rs6048) and deep vein thrombosis.

DESIGN AND METHODS

We aimed to study whether the association between F9 Malmö and deep vein thrombosis is explained by linkage disequilibrium with nearby single-nucleotide polymorphisms, and whether the association is explained biologically by F9 Malmö affecting factor IX antigen levels or activation of factor IX. We investigated the association of F9 Malmö and 28 nearby single-nucleotide polymorphisms with deep vein thrombosis in men from two case-control studies, LETS (n=380) and MEGA (n=1,469). We assessed the association of F9 Malmö with factor IX antigen level in male control subjects from LETS (n=191) and two subsets of MEGA (n=823 and n=484) and the association with endogenous thrombin potential in LETS control men. We studied the association between F9 Malmö and factor IX activation peptide in 1,199 healthy middle-aged men from the NPHS-II cohort.

RESULTS

In the combined LETS and MEGA studies, the odds ratio (95% confidence interval) for the G allele of F9 Malmö, compared with the A allele, was 0.80 (0.69-0.93). One single-nucleotide polymorphism in F9, rs422187, was strongly linked to F9 Malmö (r(2)=0.94) and was similarly associated with deep vein thrombosis. No other single-nucleotide polymorphism or haplotype tested was more strongly associated. Factor IX antigen level, factor IX activation peptide levels and endogenous thrombin potential did not differ between F9 Malmö genotypes.

CONCLUSIONS

The F9 Malmö sequence variant was the most strongly associated with deep vein thrombosis among common single-nucleotide polymorphisms in the region. However, the biological mechanism by which F9 Malmö affects risk remains unknown.

Gene variants associated with ischemic stroke: the cardiovascular health study

BACKGROUND AND PURPOSE

The purpose of this study was to determine whether 74 single nucleotide polymorphisms (SNPs), which had been associated with coronary heart disease, are associated with incident ischemic stroke.

METHODS

Based on antecedent studies of coronary heart disease, we prespecified the risk allele for each of the 74 SNPs. We used Cox proportional hazards models that adjusted for traditional risk factors to estimate the associations of these SNPs with incident ischemic stroke during 14 years of follow-up in a population-based study of older adults: the Cardiovascular Health Study (CHS).

RESULTS

In white CHS participants, the prespecified risk alleles of 7 of the 74 SNPs (in HPS1, ITGAE, ABCG2, MYH15, FSTL4, CALM1, and BAT2) were nominally associated with increased risk of stroke (one-sided P<0.05, false discovery rate=0.42). In black participants, the prespecified risk alleles of 5 SNPs (in KRT4, LY6G5B, EDG1, DMXL2, and ABCG2) were nominally associated with stroke (one-sided P<0.05, false discovery rate=0.55). The Val12Met SNP in ABCG2 was associated with stroke in both white (hazard ratio, 1.46; 90% CI, 1.05 to 2.03) and black (hazard ratio, 3.59; 90% CI, 1.11 to 11.6) participants of CHS. Kaplan-Meier estimates of the 10-year cumulative incidence of stroke were greater among Val allele homozygotes than among Met allele carriers in both white (10% versus 6%) and black (12% versus 3%) participants of CHS.

CONCLUSIONS

The Val12Met SNP in ABCG2 (encoding a transporter of sterols and xenobiotics) was associated with incident ischemic stroke in white and black participants of CHS.

GOSR2 Lys67Arg is associated with hypertension in whites

BACKGROUND

Hypertension is a risk factor for coronary heart disease (CHD), but the causes of hypertension remain largely unknown. Genetic variation is thought to contribute to the etiology of hypertension. We tested a single-nucleotide polymorphism (SNP) (Lys67Arg, rs197922) in the Golgi SNAP Receptor Complex Member 2 (GOSR2) gene for association with hypertension and blood pressure (BP). We chose this SNP because it was nominally associated with CHD in earlier studies. Further, GOSR2 is located in a linkage region for hypertension and BP in human and animal studies.

METHODS

We used logistic and linear regression to test associations of the GOSR2 SNP with hypertension and BP among 3,528 blacks and 9,861 whites from the Atherosclerosis Risk in Communities (ARIC) study. Race-specific regression models of hypertension were adjusted for age and gender. Regression models of BP were further adjusted for antihypertensive medication use.

RESULTS

The GOSR2 Lys67 allele was associated with hypertension in whites (odds ratio (OR) = 1.09, P = 0.01) but not blacks (OR = 0.96, P = 0.47). The Lys67 allele was associated with increased systolic BP (SBP) in both races (0.87 mm Hg, P < 0.001 among whites and 1.05 mm Hg, P = 0.05 among blacks). A similar association in whites was observed for the GOSR2 SNP and SBP in the Women's Genome Health Study (WGHS) (OR = 1.03, P = 0.04). The OR remained unchanged after adjustment for antihypertensive medication use (OR = 1.03, P = 0.11), though it was no longer statistically significant.

CONCLUSIONS

We found evidence that a SNP in GOSR2 is modestly associated with hypertension in whites from the ARIC study and the WGHS.

Cardiovascular disease risk prediction with and without knowledge of genetic variation at chromosome 9p21.3

BACKGROUND

Although genetic variation at chromosome 9p21.3 is associated with incident cardiovascular disease, it is unclear whether screening for this polymorphism improves risk prediction.

OBJECTIVE

To determine whether knowledge of variation at chromosome 9p21.3 provides predictive information beyond that from other readily available risk factors.

DESIGN

Prospective cohort study.

SETTING

United States.

PATIENTS

22 129 female white health professionals participating in the Women's Genome Health Study, initially without any major chronic disease, who were prospectively followed over a median of 10.2 years for incident cardiovascular disease.

MEASUREMENTS

Polymorphism at rs10757274 in chromosome 9p21.3 and additional cardiovascular disease risk factors (blood pressure, smoking status, diabetes, blood levels of cholesterol, high-sensitivity C-reactive protein, and family history of premature myocardial infarction).

RESULTS

Polymorphism at rs10757274 was associated with an adjusted hazard ratio for incident cardiovascular disease of 1.25 (95% CI, 1.04 to 1.51) for the AG genotype and 1.32 (CI, 1.07 to 1.63) for the GG genotype. However, the addition of the genotype to a prediction model based on traditional risk factors, high-sensitivity C-reactive protein, and family history of premature myocardial infarction had no effect on model discrimination as measured by the c-index (0.807 to 0.809) and did not improve the Net Reclassification Improvement score (-0.2%; P = 0.59) or the Integrated Discrimination Improvement score (0.0; P = 0.18).

LIMITATION

Study participants were all white women.

CONCLUSION

In this large prospective cohort of white women, genetic variation in chromosome 9p21.3 was associated with incident cardiovascular disease but did not improve on the discrimination or classification of predicted risk achieved with traditional risk factors, high-sensitivity C-reactive protein, and family history of premature myocardial infarction.

The platelet release reaction: just when you thought platelet secretion was simple

PURPOSE OF REVIEW

In response to agonists produced at vascular lesions, platelets release a host of components from their three granules: dense core, alpha, and lysosome. This releasate activates other platelets, promotes wound repair, and initiates inflammatory responses. Although widely accepted, the specific mechanisms underlying platelet secretion are only now coming to light. This review focuses on the core machinery required for platelet secretion.

RECENT FINDINGS

Proteomic analyses have provided a catalog of the components released from activated platelets. Experiments using a combination of in-vitro secretion assays and knockout mice have led to assignments of both vesicle-soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptor (v-SNARE) and target membrane SNARE to each of the three secretion events. SNARE knockout mice are also proving to be useful models for probing the role of platelet exocytosis in vivo. Other studies are beginning to identify SNARE regulators, which control when and where SNAREs interact during platelet activation.

SUMMARY

A complex set of protein-protein interactions control the membrane fusion events required for the platelet release reaction. SNARE proteins are the core elements but the proteins that control SNARE interactions represent key points at which platelet signaling cascades could affect secretion and thrombosis.

Molecular genetics of myocardial infarction

Myocardial infarction (MI) is an important clinical problem because of its large contribution to mortality. The main causal and treatable risk factors for MI include hypertension, hypercholesterolemia or dyslipidemia, diabetes mellitus, and smoking. In addition to these risk factors, recent studies have shown the importance of genetic factors and interactions between multiple genes and environmental factors. Disease prevention is an important strategy for reducing the overall burden of MI, with the identification of markers for disease risk being key both for risk prediction and for potential intervention to lower the chance of future events. Although genetic linkage analyses of families and sib-pairs as well as candidate gene and genome-wide association studies have implicated several loci and candidate genes in predisposition to coronary heart disease (CHD) or MI, the genes that contribute to genetic susceptibility to these conditions remain to be identified definitively. In this review, we summarize both candidate loci for CHD or MI identified by linkage analyses and candidate genes examined by association studies. We also review in more detail studies that have revealed the association with MI or CHD of polymorphisms in MTHFR, LPL, and APOE by the candidate gene approach and those in LTA and at chromosomal region 9p21.3 by genome-wide scans. Such studies may provide insight into the function of implicated genes as well as into the role of genetic factors in the development of CHD and MI.

Analysis of 17,576 potentially functional SNPs in three case-control studies of myocardial infarction

Myocardial infarction (MI) is a common complex disease with a genetic component. While several single nucleotide polymorphisms (SNPs) have been reported to be associated with risk of MI, they do not fully explain the observed genetic component of MI. We have been investigating the association between MI and SNPs that are located in genes and have the potential to affect gene function or expression. We have previously published studies that tested about 12,000 SNPs for association with risk of MI, early-onset MI, or coronary stenosis. In the current study we tested 17,576 SNPs that could affect gene function or expression. In order to use genotyping resources efficiently, we staged the testing of these SNPs in three case-control studies of MI. In the first study (762 cases, 857 controls) we tested 17,576 SNPs and found 1,949 SNPs that were associated with MI (P<0.05). We tested these 1,949 SNPs in a second study (579 cases and 1159 controls) and found that 24 SNPs were associated with MI (1-sided P<0.05) and had the same risk alleles in the first and second study. Finally, we tested these 24 SNPs in a third study (475 cases and 619 controls) and found that 5 SNPs in 4 genes (ENO1, FXN (2 SNPs), HLA-DPB2, and LPA) were associated with MI in the third study (1-sided P<0.05), and had the same risk alleles in all three studies. The false discovery rate for this group of 5 SNPs was 0.23. Thus, we have identified 5 SNPs that merit further examination for their potential association with MI. One of these SNPs (in LPA), has been previously shown to be associated with risk of cardiovascular disease in other studies.

Polymorphism in the apolipoprotein(a) gene, plasma lipoprotein(a), cardiovascular disease, and low-dose aspirin therapy

OBJECTIVE

A minor allele variant (rs3798220) of apolipoprotein(a) has been reported to be associated with elevated plasma lipoprotein(a) [Lp(a)] and increased cardiovascular risk. We investigated whether this allele was associated with elevated Lp(a) and cardiovascular risk in the Women's Health Study, a randomized trial of low-dose aspirin, and whether aspirin reduced cardiovascular risk in minor allele carriers.

METHODS AND RESULTS

Genotypes of rs3798220 were determined for 25,131 initially healthy Caucasian participants. Median Lp(a) levels at baseline were 10.0, 79.5, and 153.9mg/dL for major allele homozygotes, heterozygotes, and minor allele homozygotes, respectively (P<0.0001). During the 9.9 years of follow-up, minor allele carriers (3.7%) in the placebo group had twofold higher risk of major cardiovascular events than non-carriers (age-adjusted hazard ratio (HR)=2.21, 95% CI: 1.39-3.52). Among carriers, risk was reduced more than twofold by aspirin: for aspirin compared with placebo the age-adjusted HR was 0.44 (95% CI: 0.20-0.94); risk was not significantly reduced among non-carriers (age-adjusted HR=0.91, 95% CI: 0.77-1.08). This interaction between carrier status and aspirin allocation was significant (P=0.048).

CONCLUSIONS

In the Women's Health Study, carriers of an apolipoprotein(a) variant had elevated Lp(a), doubled cardiovascular risk, and appeared to benefit more from aspirin than non-carriers.