Thrombosis Research 126 (2010) 498–503

Contents lists available at ScienceDirect

Thrombosis Research

j ourna l homepage: www.e lsev ie r.com/ locate / th romres

Regular Article

PLA2G7 gene polymorphisms and coronary heart disease risk: A meta-analysis

Qianqian Wang, Yongchen Hao, Xingbo Mo, Laiyuan Wang, Xiangfeng Lu, Jianfeng Huang, Jie Cao,Hongfan Li, Dongfeng Gu ⁎Department of Evidence BasedMedicine and Division of Population Genetics, Cardiovascular Institute and FuWai Hospital, Chinese Academy ofMedical Sciences and Peking UnionMedical College,Beijing, China

Abbreviations: CHD, Coronary Heart Disease; CAD,Cardiovascular Disease; MI, Myocardial Infarction; CASVasospastic Angina; MVA, Microvascular Angina; ORInterval; HWE, Hardy-Weinberg Equilibrium; QS, Qualit⁎ Corresponding author. Department of Evidence Ba

Population Genetics, Cardiovascular Institute, Fu WaiMedical Sciences and Peking Union Medical College, 167China. Tel.: +86 10 68331752; fax: +86 10 88363812.

E-mail address: gudf@yahoo.com (D. Gu).

0049-3848/$ – see front matter © 2010 Elsevier Ltd. Aldoi:10.1016/j.thromres.2010.09.009

a b s t r a c t

a r t i c l e i n f o

Article history:

Received 29 April 2010Received in revised form 22 July 2010Accepted 8 September 2010

Keywords:PLA2G7PolymorphismCoronary heart diseaseMeta-analysis

Introduction: Variants of PLA2G7 gene have been reported to be associated with coronary heart disease (CHD)since ten years ago, but the available data on this relationship are inconsistent. A meta-analysis wasconducted to assess the effect of PLA2G7 gene on CHD.Materials and Methods: Association studies were identified from the databases of PubMed, EMbase, ChineseNational Knowledge Infrastructure (CNKI) and Wanfang by two investigators and pooled effects (odds ratio(OR), together with 95% confidence interval (CI)) were calculated.Results: 14 association studies focusing on three polymorphisms (A379V, V279F and R92H) in PLA2G7 geneand risk of CHDwere included in meta-analysis, covering a total of 8,280 cases and 5,656 controls. ConcerningR92H, a significantly increased CHD risk was observed in recessive model, with an OR of 1.31(1.02, 1.68).

Nevertheless, combined analyses of studies of the A379V and V279F variants showed no significant overallassociation with CHD, yielding ORs of 0.99(0.85, 1.15) and 1.09(0.88, 1.35) in allelic analysis, with strongevidence of heterogeneity. Similar results were also obtained in dominant and recessive models.Conclusions: The results indicate 92H allele had probably increased the risk of CHD, while the hypothesizedeffects of A379V and V279F polymorphisms on CHD cannot be confirmed in present data. However, given thelimited number of studies and the potential biases, the influence of these polymorphisms on CHD risk needsfurther investigation.

© 2010 Elsevier Ltd. All rights reserved.

Introduction

Lipoprotein-associated phospholipase A2 (Lp-PLA2), known asplasmaplatelet-activating factor acetylhydrolase (PAF-AH), is producedby inflammatory cells and involved in lipoprotein metabolism andinflammatory pathways. It has been proposed to be an independentpredictor of coronary heart disease (CHD) events [1–3] and a noveltarget for immunomodulation therapy on the basis of the strongevidence from several cohort studies and meta-analyses [4–10]. Inaddition, clinical trials of varespladib (Anthera, one of Lp-PLA2inhibitors) and darapladib (GSK, another Lp-PLA2 inhibitor) are underway as anti-atherosclerotic agents [11,12]. However, the role of Lp-PLA2in thedevelopmentof atherosclerosis has not beenwithout controversy.This enzyme can hydrolyze platelet-activating factor, consistentwith ananti-inflammatory role [13,14]. On the other hand, it hydrolyzes

Coronary Artery Disease; CVD,, Coronary Artery Spam; VSA,, Odds Ratio; CI, Confidencey Sore.sed Medicine and Division ofHospital, Chinese Academy ofBeilishi Road, Beijing, 100037,

l rights reserved.

oxidized phospholipids generating two pro-inflammatory mediators,lysophosphatidylcholine (lyso-PC) and free oxidized fatty acids [15].Study of genetic mechanism may help to identify the dominant role ofLp-PLA2 and suggestwhether further efforts to prevent development ofatherosclerosis and CHD by Lp-PLA2 inhibition are warranted.

Because certain genetic variants, such as the V279F polymorphismin the PLA2G7 gene (coding Lp-PLA2, located on chromosome 6p21-p12), are known to determine the activity of Lp-PLA2, manyassociation studies have reported on PLA2G7 gene polymorphismsand CHD [16–18]. However, these studies yielded conflicting results[19,20]. To clarify the evidence, we conducted a meta-analysis todetect the effects of PLA2G7 gene polymorphisms on CHD risk.

Materials and Methods

Search strategy

We performed electronic searches of PubMed, EMbase, ChineseNational Knowledge Infrastructure (CNKI) and Wanfang databases toidentify studies that had evaluated the relationship between PLA2G7polymorphisms and CHD using the combined text words related toPLA2G7 genotypes (e.g. PLA2G7, PAF-AH, platelet-activating factor-acetylhydrolase, Lp-PLA2, polymorphism, gene, genetics, mutation)and CHD phenotypes (e.g. coronary disease, coronary heart disease,

8 Articles excluded1 Article excluded which had relevant data but

genotype information could not be obtained from authors

7 Studies potentially had overlapped populations

82 Excluded on basis of title, abstract and fulltext22 Association studies for other diseases23 Non-association studies37 Reviews, letters and editorials

104 Potentially relevant articles

22 Potentially appropriate articles

14 Studies included8 Studies for A379V-CHD analysis 10 Studies for V279F-CHD analysis 4 Studies for R92H-CHD analysis

Fig. 1. Study selection process for the meta-analysis of PLA2G7 polymorphisms andCHD, with specifications of reasons.

499Q. Wang et al. / Thrombosis Research 126 (2010) 498–503

myocardial infarction (MI), coronary artery disease, ischemic heartdisease).

The latest search was undertaken in December 2009, withoutlanguage limits. We also manually screened the reference lists of theretrieved articles to identify other relevant publications. The inclusioncriteria were as follows: (1) independent case-control, cohort orcross-sectional studies reporting on associations between PLA2G7variants and CHD; (2) studies with complete data about genotype andallele frequencies or providing related information. The exclusioncriteria were defined as follows: (1) studies without raw data weneeded; (2) family-based studies of pedigrees design; (3) studiesfocusing on intermediate outcomes (e.g. atherosclerosis). Searchresults were limited to studies carried out in human subjects. Wechose the latest and/or most informative one if any possibleoverlapping studies were found. Authors were contacted if insuffi-cient data were reported.

Data extraction and quality assessment

Two investigators (Wang and Hao) independently did the searchand data extraction. If there were any discrepancies, we resolved bydiscussion. The following data elements were extracted from eachstudy: first author, year of publication, racial descent, definition andtotal number of cases and controls, the average age and thepercentage of men in case group and control group, genotypefrequencies, genotyping method and the P value of Hardy-Weinbergequilibrium (HWE) test in the control population. We also evaluatedthe quality of individual study included in our analysis usingguidelines proposed by the NCI-NHGRIWording Group on Replicationin Association Studies [21]. These guidelines provided a checklist ofimportant issues that an association study should ideally possess, andare presented in the form of 53 conditions related to experimentaldesign, demography, quality control, etc. One score is assigned to eachcondition. If one study met a requirement, it gained 1 score andotherwise, it gained 0. The sum of the score for each study wasdescribed as total quality score. We just considered the first 41objective conditions, because the other 42-53 conditions wererelatively subjective view of the author [22]. Details of the scale arepresented in Supplement Table 1.

Statistical analysis

We conducted meta-analysis for polymorphisms with availabledata from at least 4 independent studies. The strength of associationwas estimated as odds ratio (OR) and corresponding 95% confidenceintervals (CIs). Standard meta-analysis methods were applied.Primary analyses were prespecified to compare allele frequenciesbetween cases and controls, implying an underlying codominantmodel of inheritance. Subsidiary analysis involved recessive (onlyminor homozygous having the effect) and dominant genetic model(assuming heterozygotes have the same increased risk as minorhomozygous). The pooled ORs were calculated first using fixed effectmodel (Mantel-Haenszel method), which assumes that all studiesshare the same common effect. The existence of heterogeneitybetween studies was evaluated using Cochran's Q statistic [23]. Inaddition, inconsistency across studies was quantified by means of theI2 statistic, which describes the percentage of the observed between-study variability attributable to heterogeneity rather than chance. I2

takes values between 0% and 100% and there should be importantheterogeneity when I2N50% [24]. In case of heterogeneity, meta-analysis was performed by applying the random effect model(DerSimonian and Laird method).

In each study, the genotype distribution in control population wastested for departure from HWE using Fisher's exact test. Studiesdeviated from HWE were excluded from meta-analysis to detect thestability of the results. Moreover, we used sensitivity analysis (each

study was excluded one at a time) to examine influence of one studyon the overall summary estimate. Studies were subdivided byethnicity (Caucasian, including Caucasian of European origin; eastAsian, including Chinese, Japanese, Korean; west Asian: Turkish), casedefinition (e.g. MI, CHD or cardiovascular diseases (CVD)) and theaverage age of study population (b60 or≥60 years old), sample size(b1000 or≥1000 participants) and quality score (QS) (QSb

PQS or

QS≥ PQS) for subgroup analysis to investigate the probable source of

heterogeneity.Publication bias was evaluated using inverted funnel plot and

Egger's test [25]. All analyses were carried out using Stata software(version9.0). All statistical evaluations were performed assuming atwo-sided test with significance level of 0.05.

Results

Study characteristics

A total of 22 studies were identified from the databases and thereference lists (Fig. 1). One study [26] for unavailable genotypeinformation was excluded. Of the remaining 21 studies, seven studiespartially overlapped: two studies described in Xu's dissertation[27,28] used the same dataset [29]; five studies [20,30–33] potentiallyhad overlapping cases. Thus, 14 studies [16–19,29,34–42] were finallyincluded in our meta-analysis (Fig. 1). These 14 studies togetherincluded 13,936 individuals and up to 8 polymorphisms includingrs1051931 (A379V), rs16874954 (V279F), rs1805017 (R92H),rs1805018 (I198T), rs1421378 (T-403G), rs10948301 (G-1357A),rs13210554 and rs6935460. Our meta-analysis focused on three SNPs,namely A379V, V279F and R92H, because other SNPs were examinedin very small number of studies. These three polymorphisms are allcommon non-synonymous substitutions and V279F was thought tocause PLA2G7 deficiency. Previous studies have shown completelinkage disequilibrium (LD) between A379V and V279F [35], andpartial LD between the R92H and A379V [26,35]. Among these 14studies, three of them were in Caucasians [17,18,34] and eleven in

500 Q. Wang et al. / Thrombosis Research 126 (2010) 498–503

Asians [16,19,29,35–42]. With the exception of one cohort study [34],other 13 studies were case-control designed. Most studies matchedcontrols to cases by ethnicity and two studies further matchedcontrols to cases by age and gender [17,36]. The cases in eight studieswere angiographically documented CHD and those in the other fourstudies diagnosed based on medical history, electrocardiographicchanges or elevation of serum cardiac enzymes. Ach provocation testwas used for case classification in Mashiba's study [37]. Abuzeid et al.includedmale first MI survivors fromHIFMECH Study [17]. In additionto CHD, a small number of small vascular diseases such as renal arterystenosis, and peripheral arterial disease were included in case groupin Jang's study [42]. The controls in eleven studies were healthyindividuals and those in the other three studies were hospitalpatients. The principal characteristics of the 14 studies are summa-rized in Table 1.

For each of these 14 studies, the QS based on NCI-NHGRI guidelines islisted in Supplement Table 1. The mean of QS was 10.0 (median: 9.5;range: 6-15). Studies with a relatively small sample size (b1000)[19,29,36–38,40,41] which showed more extreme results and widerconfidence intervals trended to have lower QS (mean: 9.0; range: 6-14)than thatwith larger sample size (≥1000) (meanofQS: 11.3, range: 9-15)[16–18,34,35,39,42].

Contrasts for each polymorphism

Association of the A379V polymorphism with CHDEight eligible studies with 6,971 genotyped cases and 4,262

genotyped controls were investigated for the association betweenA379V polymorphism and risk of CHD. Three studies had Caucasiandescent and the other five studies had Asian descent (SupplementTable 2). Among controls, the prevalence of V allele was 0.227 inCausations and 0.163 in Asians. Results for these eight studies aresummarized in Fig. 2. We found no significant effect of the V allele onCHD, compared with the A allele (OR=0.99, 95%CI: 0.85-1.15)(Fig. 2), with statistically significant heterogeneity among studies(I2=77.4%, Pb0.001). Results were similar in recessive and dominantmodels. The results were not significantly affected by the removal ofany study and we failed to find out the source of heterogeneity aftersubgroup analysis where the studies were stratified by studycharacteristics, such as ethnicity, definition of cases, sample size andthe average age of study population (Supplement Table 3).

Table 1Main characteristics of the studies included in meta-analysis.

Study, year Country Ethnicity Study design Outcom

Yamada et al. (1998) Japan East Asian Case-control MIIto et al. (2002) Japan East Asian Case-control CASHohda et al. (2003) Japan East Asian Case-control MIAbuzeid et al. (2003) HIFMECH Caucasian Case-control(age matched) MINinio et al. (2004) Germany Caucasian Case-control CADMashiba et al. (2005) Japan East Asian Case-control VSA,MVLiu et al.(2006) Taiwan East Asian Case-control(gender and age

matched)MI

Sekuri et al. (2006) Turkey West Asian Case-control CADZhang et al. (2006) China East Asian Case-control CHDJang et al. (2006) Korea East Asian Case-control(gender matched) CVDLi et al.(2008) China East Asian Case-control CHDHoffmann et al. (2009) Germany Caucasian Cohort CADHou et al. (2009) China East Asian Case-control CHDXu et al.(2009) China East Asian Case-control CHD

HIFMECH study, Hypercoagulability and Impaired Fibrinolytic function MECHanisms predispLondon (UK), Marseille (France), and San Giovanni Retondo (Italy); MI, Myocardial InfarctDisease; CAS, Coronary Artery Spam; VSA, Vasospastic Angina; MVA, Microvascular AnginaPolymerase Chain Reaction-Single Strand Conformation Polymorphism; PCR-RFLP, Polymer

Association of the V279F polymorphism with CHDTen studies with 3,611 genotyped cases and 3,602 genotyped

controls were included in V279F-CHD analysis. V279F polymorphismonly exists in Asians and the prevalence of the F allele was 0.114among controls. No significant association was found between CHDand the F allele as compared with the V allele (OR=1.09, 95%CI: 0.88-1.35) (Fig. 3). No other contrasts yielded statistically significantassociations with CHD, with strong evidence of heterogeneity acrossstudies. Since V279F was not found in the control group of Sekuri'sstudy, we added 0.5 to each genotype count for meta-analysis.Genotype frequencies among three control groups were significantlydeviated from HWE. Furthermore, in Mashiba's study, the cases weredefined as VSA (vasospasic angina) and MVA (microvascular angina),which was different from other studies (Supplement Table 2). Theresults didn't change materially after sensitivity analysis or excludingthe four studies deviated from HWE (results not shown) and thepooled OR listed in Fig. 3 were calculated from all of the ten studies forV279F. However, the between-study heterogeneity was partlyexplained by different case definition and F allele was shown as arisk factor for MI in dominant model (Supplement Table 3).

Association of the R92H polymorphism with CHDThere were only four studies with 4,911 cases and 2,336 controls

on R92H analysis. Among controls, the observed frequencies of the Hallele were more prevalent in controls in Caucasians (0.244) than inAsians (0.157). No association was observed between the H allele andCHD (H allele vs. R allele: OR=1.19, 95%CI: 0.99-1.43) (Fig. 4).However, we found that the 92H allele was weakly associated with anincreased risk for CHD in a recessive model. The pooled OR was 1.31(95%CI: 1.02-1.68) by the fixed effect model, without between-studyheterogeneity (I2=0.0%, P=0.431). But in the dominant model, nostatistically significant association between R92H and CHD wasdetected, nor when the analysis was stratified by ethnicity (Supple-ment Table 3).

For publication bias estimating, we did not observe visual orstatistically significant asymmetry according to inverted funnel plotand Egger's test (Table 2).

Discussion

PLA2G7 gene polymorphisms were first identified as an indepen-dent risk factor for CHD in Japanese population [16]. However,

e Eligiblesubjects

Age years Percentage ofmen (%)

Genotyping method QS

Cases Controls Cases Controls Cases Controls

454 602 58.1 57.5 82.2 75.1 PCR 9214 212 61.4 61.1 49.0 48.6 PCR 9136 235 58.9 37.3 84.0 68.1 PCR 6533 575 51.9 51.5 100.0 100.0 PCR 11

1314 485 61.7 60.0 74.7 72.6 PCR-SSCP 10A 223 61 60.2 59.7 58.0 50.8 PCR-RFLP 8

200 200 40.2 41.3 84.0 83.0 PCR 9

115 128 47.1 46.2 73.0 74.2 PCR 8124 103 64.0 57.1 82.3 53.4 Allele-Specific PCR 9532 670 54.7 49.8 100.0 100.0 SBE 10806 482 61.5 61.6 77.3 54.5 TaqMan 12

2541 693 63.8 58.8 74.8 51.9 PCR 12827 947 54.5 52.0 78.6 73.7 PCR-RFLP 15261 263 61.8 61.1 79.7 74.5 PCR-ShineRoar probes 14

osing to myocardial infarction (MI) study, involving 4 countries: Stockholm (Sweden),ion; CAD, Coronary Artery Disease; CVD, Cardiovascular Disease; CHD, Coronary Heart; PCR, Polymerase Chain Reaction; SBE, Single Base Primer Extension Assay; PCR-SSCP,ase Chain Reaction–Restriction Fragment Length Polymorphism; QS, Quality Score.

NOTE: Weights are from random effects analysis

Overall (I-squared = 74.5%, p = 0.000)

Li et al

Study

Ninio et al

Hou et al

Jang et al

Liu et al

Hoffmann et al

Abuzeid et al

Xu et al

2008

Year

2004

2009

2006

2006

2009

2003

2009

16.3%/18.0%

frequency

(case/control)

19.5%/24.2%

16.6%/15.9%

15.5%/14.6%

32.5%/21.0%

21.4%/20.9%

21.9%/23.5%

379V allele

12.5%/15.4%

0.99 (0.85, 1.15)

0.88 (0.72, 1.09)

OR (95% CI)

0.76 (0.63, 0.90)

1.06 (0.88, 1.27)

1.08 (0.86, 1.35)

1.81 (1.32, 2.49)

1.03 (0.89, 1.19)

0.91 (0.75, 1.12)

0.78 (0.55, 1.11)

100.00

12.92

%

Weight

14.04

13.86

12.47

9.65

14.99

13.26

8.80

0.99 (0.85, 1.15)

0.88 (0.72, 1.09)

OR (95% CI)

0.76 (0.63, 0.90)

1.06 (0.88, 1.27)

1.08 (0.86, 1.35)

1.81 (1.32, 2.49)

1.03 (0.89, 1.19)

0.91 (0.75, 1.12)

0.78 (0.55, 1.11)

100.00

12.92

%

Weight

14.04

13.86

12.47

9.65

14.99

13.26

8.80

Decreased risk Increased risk 1.2 .5 2 5

Fig. 2. Meta-analysis for the relationship between A379V polymorphism and CHD risk in allelic analysis (V allele vs. A allele). Year represents publish year. The solid squaresrepresent odds ratios (ORs) from individual studies; the diamonds are shown as overall effect, calculated by means of a random effect model.

501Q. Wang et al. / Thrombosis Research 126 (2010) 498–503

subsequent studies yielded controversial findings. In the absence ofvery large individual studies, we have conducted an updated meta-analysis for addressing the association between PLA2G7 polymorph-isms and CHD. In the present study, A379V variant yielded nosignificant overall associations with CHD, with strong evidence ofheterogeneity across studies. Nevertheless, the possibility of arelationship between A379V and CHD cannot be fully explained bythe means of a meta-analysis, considering we did not adjusttraditional risk factors of CHD or potential confounders. The same istrue for V279F variant. While the combined results from three studieswith MI cases showed a positive association about V279F in dominantmodel, which was consistent with the results observed in Japanesepopulation. V279F, which just exists in Asians, is one of the mostinteresting variant in the PLA2G7 gene because this nucleotide changeresults in a Val/Phe substitution at amino acid residue 279 of themature protein and is responsible for the loss of catalytic activity. In

NOTE: Weights are from random effects analysis

Overall (I-squared = 69.7%, p = 0.001)

Ito et al

Study

Hou et al

Mashiba et al

Jang et al

Zhang et al

Li et al

Sekuri et al

Liu et al

Yamada et al

Hohda et al

2002

Year

2009

2005

2006

2006

2008

2006

2006

1998

2003

15.2%/15.6%

(case/control)

5.0%/5.6%

15.4%/19.7%

10.2%/14.0%

279F allele

12.1%/4.9%

6.9%/4.9%

1.3%/0.0%

16.5%/17.3%

frequency

17.6%/13.6%

37.5%/32.8%

Decreased ris

.2 .5

Fig. 3.Meta-analysis for the relationship between V279F polymorphism and CHD risk in alleliodds ratios (ORs) from individual studies; the diamonds are shown as overall effect, calcul

principle, identification of gene–serum activity and gene–CHDassociations should help to quantify any causal role of serum Lp-PLA2 activity. Although available studies of V279F polymorphism andserum Lp-PLA2 activity suggest that V279F exhibited markedlyreduced Lp-PLA2 activity, its overall association with CHD remainsuncertain in the present analysis, which might be due to variousresidual biases. Since the V279F mutation has not been found inCaucasians, the results of V279F from this meta-analysis could not beapplicable for Caucasians. Regarding the R92H mutation, meta-analysis carried out under a fixed effect model showed that the Hallele was significantly associated with CHD in the recessive geneticmodel, whichwas consistentwith the findings fromKruse's study thatthe R92H variant decreased the substrate affinities of PAF andtherefore leaded to prolonged activities of this potent inflammatoryprotein [43]. Although Sutton's study, which was removed from theanalysis of R92H because of unavailability of genotype information,

1.09 (0.88, 1.35)

0.97 (0.67, 1.41)

OR (95% CI)

0.89 (0.66, 1.20)

0.75 (0.43, 1.28)

0.70 (0.54, 0.90)

2.70 (1.29, 5.66)

1.45 (1.02, 2.06)

3.38 (0.53, 21.64)

0.95 (0.65, 1.37)

1.36 (1.07, 1.72)

1.23 (0.90, 1.68)

100.00

11.00

Weight

12.42

8.13

13.36

5.61

11.41

1.26

11.04

%

13.62

12.15

1.09 (0.88, 1.35)

0.97 (0.67, 1.41)

OR (95% CI)

0.89 (0.66, 1.20)

0.75 (0.43, 1.28)

0.70 (0.54, 0.90)

2.70 (1.29, 5.66)

1.45 (1.02, 2.06)

3.38 (0.53, 21.64)

0.95 (0.65, 1.37)

1.36 (1.07, 1.72)

1.23 (0.90, 1.68)

100.00

11.00

Weight

12.42

8.13

13.36

5.61

11.41

1.26

11.04

%

13.62

12.15

k Increased risk

1 2 5

c analysis (F allele vs. V allele). Year represents publish year. The solid squares representated by means of a random effect model.

NOTE: Weights are from random effects analysis

Overall (I-squared = 72.3%, p = 0.013)

Xu et al

Hoffmann et al

Hou et al

Ninio et al

Study

2009

2009

2009

2004

Year

17.2%/10.6%

26.0%/25.8%

frequency

18.2%/17.2%

92H allele

27.1%/22.4%

(case/control)

1.19 (0.99, 1.43)

1.75 (1.22, 2.50)

1.01 (0.88, 1.16)

1.07 (0.90, 1.28)

1.29 (1.08, 1.53)

OR (95% CI)

100.00

15.07

30.36

%

27.19

27.37

Weight

1.19 (0.99, 1.43)

1.75 (1.22, 2.50)

1.01 (0.88, 1.16)

1.07 (0.90, 1.28)

1.29 (1.08, 1.53)

OR (95% CI)

100.00

15.07

30.36

%

27.19

27.37

Weight

Decreased risk Increased risk

1.2 .5 2 5

Fig. 4.Meta-analysis for the relationship between R92H polymorphism and CHD risk in allelic analysis (H allele vs. R allele). Year represents publish year. The solid squares representodds ratios (ORs) from individual studies; the diamonds are shown as overall effect, calculated by means of a fixed effect model.

502 Q. Wang et al. / Thrombosis Research 126 (2010) 498–503

showed that the H allele was associated with a reduced risk ofcoronary artery disease (CAD) [26], we must highlight that the studywas of a relative small sample size compared with our research andthe population was selected from different races.

CHD has a complex etiology generated by combined effect ofgenetic and environmental risk factors, which were not adequatelyevaluated in our analysis. There was evidence of significant hetero-geneity among these studies. In addition to the presence of differentclassification criteria used for cases and controls or differentcharacteristics of samples, the true genetic diversity across differentpopulations probably accounts for a significant part of the heteroge-neity found. Besides, the results might be distorted by potentialweakness and biases of genetic association studies, such as genotyp-ing error, phenotype misclassification, population stratification, gene-gene or gene-environment interactive effect, and selective reportingbiases [44,45]. Although no statistically significant publication biaswas found from Egger's test, we must stress that exclusion ofunpublished studies may affect the validity of the analysis.

In conclusion, the results indicated H allele of R92H variant hadsignificantly increased the risk of CHD in recessive model, while thehypothesized effect of A379V and V279F on CHD cannot be confirmed

Table 2The main results of the meta-analysis.

Allele contrasts in different genetic Models OR (95%CI) P value for Z test

A379VV allele vs. A allele 0.99(0.85,1.15) 0.894Dominant model 0.98(0.83,1.16) 0.791Recessive model 0.98(0.70,1.36) 0.880

V279FF allele vs. V allele 1.09(0.88,1.35) 0.445Dominant model 1.12(0.86,1.46) 0.400Recessive model 1.05(0.71,1.56) 0.808

R92HH allele vs. R allele 1.19(0.99,1.43) 0.058Domiant model 1.20(0.97,1.49) 0.086Recessive model 1.31(1.02,1.68) 0.032⁎

⁎ Pb0.05.

in the present data. Well-conducted cohort studies are warranted toreplicate the results as well as elucidate the biological mechanismunderlying the association of the PLA2G7 gene polymorphisms withCHD.

Conflict of interest statement

The authors have no conflict of interest to declare.

Acknowledgement

This work was supported by National Basic Research Program ofChina (Grant No. 2006CB503805), National High Technology Researchand Development Program of China (Grant No. 2006AA02Z170).

Appendix A. Supplementary data

Supplementary data to this article can be found online atdoi:10.1016/j.thromres.2010.09.009.

I2 for heterogeneity (%) P value for heterogeneity P value for Egger's Test

74.5 b0.001⁎ 0.54272.3 0.001⁎ 0.69254.5 0.031⁎ 0.910

69.7 0.001⁎ 0.35173.1 b0.001⁎ 0.3300.0 0.974 0.694

72.3 0.013⁎ 0.13071.7 0.014⁎ 0.0940.0 0.431 0.342

503Q. Wang et al. / Thrombosis Research 126 (2010) 498–503

References

[1] Packard CJ, O'Reilly DS, Caslake MJ, McMahon AD, Ford I, Cooney J, et al.Lipoprotein-associated phospholipase A2 as an independent predictor of coronaryheart disease. West of Scotland Coronary Prevention Study Group. N Engl J Med2000;343:1148–55.

[2] Koenig W, Khuseyinova N, Lowel H, Trischler G, Meisinger C. Lipoprotein-associated phospholipase A2 adds to risk prediction of incident coronary events byC-reactive protein in apparently healthy middle-aged men from the generalpopulation: results from the 14-year follow-up of a large cohort from southernGermany. Circulation 2004;110:1903–8.

[3] May HT, Horne BD, Anderson JL, Wolfert RL, Muhlestein JB, Renlund DG, et al.Lipoprotein-associated phospholipase A2 independently predicts the angiograph-ic diagnosis of coronary artery disease and coronary death. Am Heart J 2006;152:997–1003.

[4] Koenig W, Twardella D, Brenner H, Rothenbacher D. Lipoprotein-associatedphospholipase A2 predicts future cardiovascular events in patients with coronaryheart disease independently of traditional risk factors, markers of inflammation,renal function, and hemodynamic stress. Arterioscler Thromb Vasc Biol 2006;26:1586–93.

[5] Oei HH, van der Meer IM, Hofman A, Koudstaal PJ, Stijnen T, Breteler MM, et al.Lipoprotein-associated phospholipase A2 activity is associated with risk ofcoronary heart disease and ischemic stroke: the Rotterdam Study. Circulation2005;111:570–5.

[6] Brilakis ES, McConnell JP, Lennon RJ, Elesber AA, Meyer JG, Berger PB. Associationof lipoprotein-associated phospholipase A2 levels with coronary artery diseaserisk factors, angiographic coronary artery disease, and major adverse events atfollow-up. Eur Heart J 2005;26:137–44.

[7] Ballantyne CM, Hoogeveen RC, Bang H, Coresh J, Folsom AR, Heiss G, et al.Lipoprotein-associated phospholipase A2, high-sensitivity C-reactive protein,and risk for incident coronary heart disease in middle-aged men and women inthe Atherosclerosis Risk in Communities (ARIC) study. Circulation 2004;109:837–42.

[8] Winkler K, Winkelmann BR, Scharnagl H, Hoffmann MM, Grawitz AB, Nauck M,et al. Platelet-activating factor acetylhydrolase activity indicates angiographiccoronary artery disease independently of systemic inflammation and other riskfactors: the Ludwigshafen Risk and Cardiovascular Health Study. Circulation2005;111:980–7.

[9] Garza CA, Montori VM, McConnell JP, Somers VK, Kullo IJ, Lopez-Jimenez F.Association between lipoprotein-associated phospholipase A2 and cardiovasculardisease: a systematic review. Mayo Clin Proc 2007;82:159–65.

[10] Koenig W, Khuseyinova N. Lipoprotein-associated and secretory phospholipaseA2 in cardiovascular disease: the epidemiological evidence. Cardiovasc Drugs Ther2009;23:85–92.

[11] Rosenson RS, Hislop C, McConnell D, Elliott M, Stasiv Y, Wang N, et al. Effects of 1-H-indole-3-glyoxamide (A-002) on concentration of secretory phospholipase A2(PLASMA study): a phase II double-blind, randomised, placebo-controlled trial.Lancet 2009;373:649–58.

[12] Mohler III ER, Ballantyne CM, Davidson MH, Hanefeld M, Ruilope LM, Johnson JL,et al. The effect of darapladib on plasma lipoprotein-associated phospholipase A2activity and cardiovascular biomarkers in patients with stable coronary heartdisease or coronary heart disease risk equivalent: the results of a multicenter,randomized, double-blind, placebo-controlled study. J Am Coll Cardiol 2008;51:1632–41.

[13] Theilmeier G, De Geest B, Van Veldhoven PP, Stengel D, Michiels C, Lox M, et al.HDL-associated PAF-AH reduces endothelial adhesiveness in apoE-/- mice. FASEB J2000;14:2032–9.

[14] Quarck R, De Geest B, Stengel D, Mertens A, LoxM, Theilmeier G, et al. Adenovirus-mediated gene transfer of human platelet-activating factor-acetylhydrolaseprevents injury-induced neointima formation and reduces spontaneous athero-sclerosis in apolipoprotein E-deficient mice. Circulation 2001;103:2495–500.

[15] Hakkinen T, Luoma JS, Hiltunen MO, Macphee CH, Milliner KJ, Patel L, et al.Lipoprotein-associated phospholipase A(2), platelet-activating factor acetylhy-drolase, is expressed by macrophages in human and rabbit atherosclerotic lesions.Arterioscler Thromb Vasc Biol 1999;19:2909–17.

[16] Yamada Y, Ichihara S, Fujimura T, Yokota M. Identification of the G994–NTmissense in exon 9 of the plasma platelet-activating factor acetylhydrolase geneas an independent risk factor for coronary artery disease in Japanese men. Metab,Clin Exp 1998;47:177–81.

[17] Abuzeid AM, Hawe E, Humphries SE, Talmud PJ. Association between theAla379Val variant of the lipoprotein associated phospholipase A2 and risk ofmyocardial infarction in the north and south of Europe. Atherosclerosis 2003;168:283–8.

[18] Ninio E, Tregouet D, Carrier JL, Stengel D, Bickel C, Perret C, et al. Platelet-activatingfactor-acetylhydrolase and PAF-receptor gene haplotypes in relation to futurecardiovascular event in patients with coronary artery disease. Hum Mol Genet2004;13:1341–51.

[19] Ito T, Yasue H, Yoshimura M, Nakamura S, Nakayama M, Shimasaki Y, et al.Paraoxonase gene Gln192Arg (Q192R) polymorphism is associated with coronaryartery spasm. Hum Genet 2002;110:89–94.

[20] Liu PY, Chung HC, Chen JY, Lee CH, Chan SH, Li YH, et al. Platelet-activating factor-acetylhydrolase (PLA2G7) A379V (exon 11) gene polymorphism is functionallyassociated with coronary artery disease severity but not the onset of acutecoronary syndrome. Acta Cardiol Sin 2006;22:212–20.

[21] Chanock SJ, Manolio T, Boehnke M, Boerwinkle E, Hunter DJ, Thomas G, et al.Replicating genotype-phenotype associations. Nature 2007;447:655–60.

[22] Lluis-Ganella C, Lucas G, Subirana I, Escurriol V, TomasM, Senti M, et al. Qualitativeassessment of previous evidence and an updated meta-analysis confirms lack ofassociation between the ESR1 rs2234693 (PvuII) variant and coronary heartdisease in men and women. Atherosclerosis 2009;207:480–6.

[23] DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials 1986;7:177–88.

[24] Higgins JP, Thompson SG, Deeks JJ, Altman DG. Measuring inconsistency in meta-analyses. BMJ 2003;327:557–60.

[25] Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected bya simple, graphical test. BMJ 1997;315:629–34.

[26] Sutton BS, Crosslin DR, Shah SH, Nelson SC, Bassil A, Hale AB, et al. Comprehensivegenetic analysis of the platelet activating factor acetylhydrolase (PLA2G7) geneand cardiovascular disease in case-control and family datasets. Hum Mol Genet2008;17:1318–28.

[27] Xu M, Sun J, Luo G, Bai J, Liu Y, Ke H. Association between lipoprotein-associatedphospholipase A2 gene R92H polymorphism and coronary heart disease in HanChinese. Chin J Arterioscler 2008;16:965–8.

[28] Xu M, Sun J, Lou G, Bai J, Ke H, Liu Y. Connecting research to lipoprotein-associatedphosphofipaseA2 gene polymorphisms of the patients with coronary heartdisease. J Clin Intern Med 2009;26:18–20.

[29] Xu M. Connecting Research to LP-PLA2 Gene Polymorphisms R92H and A379V ofthe Patients with Coronary Heart Disease. Dissertation, Suzhou University, 2009.

[30] Yamada Y, Yoshida H, Ichihara S, Imaizumi T, Satoh K, Yokota M. Correlationsbetween plasma platelet-activating factor acetylhydrolase (PAF-AH) activity andPAF-AH genotype, age, and atherosclerosis in a Japanese population. Atheroscle-rosis 2000;150:209–16.

[31] Shimokata K, Yamada Y, Kondo T, Ichihara S, Izawa H, Nagata K, et al. Associationof gene polymorphisms with coronary artery disease in individuals with orwithout nonfamilial hypercholesterolemia. Atherosclerosis 2004;172:167–73.

[32] Hou L. Associations of two inflammation genes-PLA2G7 and TNF with coronaryheart disease in a Chinese Han population. Dissertation, Peking Union MedicalCollege, 2009.

[33] Hirashiki A, Yamada Y, Murase Y, Suzuki Y, Kataoka H, Morimoto Y, et al.Association of gene polymorphisms with coronary artery disease in low- or high-risk subjects defined by conventional risk factors. J Am Coll Cardiol 2003;42:1429–37.

[34] Hoffmann MM, Winkler K, Renner W, Winkelmann BR, Seelhorst U, Wellnitz B,et al. Genetic variants and haplotypes of lipoprotein associated phospholipase A2and their influence on cardiovascular disease (The Ludwigshafen Risk andCardiovascular Health Study). J Thromb Haemost 2009;7:41–8.

[35] Hou L, Chen S, Yu H, Lu X, Chen J, Wang L, et al. Associations of PLA2G7 genepolymorphisms with plasma lipoprotein-associated phospholipase A2 activityand coronary heart disease in a Chinese Han population: The Beijing atheroscle-rosis study. Hum Genet 2009;125:11–20.

[36] Liu PY, Li YH, Wu HL, Chao TH, Tsai LM, Lin LJ, et al. Platelet-activating factor-acetylhydrolase A379V (exon 11) gene polymorphism is an independent andfunctional risk factor for premature myocardial infarction. J Thromb Haemost2006;4:1023–8.

[37] Mashiba J, Koike G, Kamiunten H, Ikeda M, Sunagawa K. Vasospastic angina andmicrovascular angina are differentially influenced by PON1 A632G polymorphismin the Japanese. Circ J 2005;69:1466–71.

[38] Sekuri C, Cam FS, Tengiz I, Ercan E, Bayturan O, Berdeli A. Association of platelet-activating factor acetylhydrolase gene polymorphism with premature coronaryartery disease in Turkish patients. Anadolu Kardiyol Derg 2006;6:132–4.

[39] Li L. Association of Lipoprotein-Associated Phospholipase A2 ( Lp-PLA2) Gene andCoronary heart disease. Dissertation, Peking Union Medical College, 2008.

[40] Zhang H, Sun F, Wang S, He Q, Ji F, Xu F. Associationg between gegetic variation inPAF-AH V279F and coronary heart disease. Chin J Geriatr 2006;25:895–9.

[41] Hohda S, Kimura A, Sasaoka T, Hayashi T, Ueda K, Yasunami M, et al. Associationstudy of CD14 polymorphism with myocardial infarction in a Japanese population.Jpn Heart J 2003;44:613–22.

[42] Jang Y, Kim OY, Koh SJ, Chae JS, Ko YG, Kim JY, et al. The Val279Phe variant of thelipoprotein-associated phospholipase A2 gene is associated with catalyticactivities and cardiovascular disease in Korean men. J Clin Endocrinol Metab2006;91:3521–7.

[43] Kruse S, Mao XQ, Heinzmann A, Blattmann S, Roberts MH, Braun S, et al. TheIle198Thr and Ala379Val variants of plasmatic PAF-acetylhydrolase impaircatalytical activities and are associated with atopy and asthma. Am J Hum Genet2000;66:1522–30.

[44] Daly AK, Day CP. Candidate gene case-control association studies: advantages andpotential pitfalls. Br J Clin Pharmacol 2001;52:489–99.

[45] Ioannidis JP, Boffetta P, Little J, O'Brien TR, Uitterlinden AG, Vineis P, et al.Assessment of cumulative evidence on genetic associations: interim guidelines.Int J Epidemiol 2008;37:120–32.