Angiotensin-converting enzyme insertion/deletion polymorphism and susceptibility to Kawasaki disease: a meta-analysis

Background The angiotensin-converting enzyme (ACE) I/D polymorphism has been reported to be associated with Kawasaki disease (KD), but studies to date present conflicting results. Objectives The aim of this study is to derive a more precise estimation of the association between the ACE I/D polymorphism and KD risk. Methods PubMed, EMBASE, CNKI and Wangfang databases were retrievaled to identify for relevant studies from inception to May 2017. Pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated using Stata 12.0 software. Results A total of 6 case-control studies comprising 634 patients and 458 controls were included in the meta-analysis, and we found a significant association between the ACE I/D polymorphism and KD risk (D vs I:OR = 0.81, 95%CI = 0.31–2.11;DD vs II: OR = 1.03, 95%CI = 0.42–2.54; DI vs II: OR = 1.44, 95%CI = 1.09–1.90; dominant model: OR = 1.43, 95%CI = 1.11–1.85; recessive model: OR = 1.21, 95%CI = 0.44–3.29 ). When stratified by sample size>200, this polymorphism is associated with an increased the risk of KD. Conclusion The I/D polymorphism in the ACE gene may be associated with susceptibility to KD.


Introduction
Kawasaki disease(KD) is an self-limited vasculitis that mainly affects young children 1 . Although KD was first described in 1967 2 , its etiology is still not fully understood.The clinical manifestations of KD include persistent fever, non-purulent conjunctivitis, diffuse muco-sal inflammation, polymorphous skin rashes, indurative angioedema of the hands and feet, and non-suppurative cervical lymphadenopathy 3 . In about 20% of patients vasculitis will lead to coronary artery lesions as detected by echocardiography, showing this to be the principal cause of acquired heart disease of children 4 . Recent studies suggest that gene polymorphisms maybe associated with KD, such as the FCGR2A gene rs1801274 polymorphism 5 . The renin-angiotensin system (RAS) has been implicated in modulating blood pressure and homeostasis of the cardiovascular system 6 . Angiotensin-converting enzyme (ACE) is an crucial circulating enzyme of the RAS.It catalyzes the conversion of angiotensin I to angiotensin II and mediates bradykinin degradation 7 . In addition,angiotensin II is a potent pro-inflammatory modulator that augments and perpetuates immune responses. The human ACE gene is located on chromosome 17q23 and a large number of polymorphisms have been identified.
African Health Sciences Vol 17 Issue 4, December, 2017 One intron 16 insertion/deletion (I/D,rs4646994) polymorphism of this gene is characterized by the presence or absence of a 287bp Alu repetitive sequence 9 . Homozygotes for the D allele have the highest plasma ACE levels, heterozygotes (ID) have intermediate levels, and homozygotes for the I allele have the lowest levels 10 . Many studies have investigated the relationship between ACE I/D polymorphism and KD. The inconsistency of these results may have resulted from inadequate statistical power owing to small sample size and eco-geographical differences.Meta-analysis may overcome these limitations of individual research 11 . We performed this meta-analysis to arrive at a more accurate estimation of the association of ACE I/D polymorphism with KD risk.

Materials and methods Literature search strategy
Computer searches of PubMed,EMBASE,CNKI and Wangfang databases were performed via the following key words:"ACE gene","Kawasaki disease/KD", "I/D", "single nucleotide polymorphism" and "genetic polymorphism". Only human studies were selected. Additional articles were identified by a manual searching of the references of in the related original studies.

Study selection
Articles included in the meta-analysis met the following inclusion criteria:1) relevant case-control studies of KD cases and healthy controls; 2) articles on the relation of the ACE I/D polymorphism and susceptibility to KD and 3) studies that included sufficient genotype information for extraction.Exclusion criteria were as follows: 1) not case-control studies; 2) case reports, reviews, or meta-analysis; 3) studies that were based on incomplete raw data.

Data extraction
The collected data included the first author's surname, publication date, country of origin, ethnicity,the number of cases and controls, the genotype frequency of ACE I/D polymorphism and deviation from Hardy-Weinberg Equilibrium (HWE) of the control group.

Statistical analysis
Fisher's exact test was used to test HWE for distributions of genotypes among controls.The strength of the correlation between ACE I/D polymorphism and susceptibility to KD was estimated by odds ratio (OR) and 95% confidence interval (95%CI) as follows:D vs I, a homozygote comparison (DD vs II), a heterozygote comparison (DI vs II), a dominant model (DD+DI vs II) and a recessive model (II+DI vs DD) between groups.The heterogeneity among these articles was checked via the I2 test.When I2 > 50% indicated heterogeneity across studies,the random effects model was used,otherwise the fixed effects model was performed. The sensitivity analysis was performed by used via omitting each individual article, and an individual article was suspected of excessive sensitivity if the point estimate of its omitted analysis was outside the 95% CI of the pooled analysis.To assess the potential publication bias, Begg's and Egger's tests were performed.All statistical tests were performed with STATA (version 12.0; Stata Corporation, College Station, TX).

Study characteristics
The database search yielded 137 publications, of which both of the reviewers considered 10 to be potentially eligible.We excluded 4 of the articles during the second phase of the inclusion process.The remaining 6 articles were included in the combined analysis 12-17. A The flow chart summarizing the study selection process is shown in Figure 1. Included studies were all performed in China,Japan or Korea. All studies were in agreement with HWE except Shim et al,Wan et al and Xie et al [15][16][17] .The principle characteristics of eligible studies are summarized in Table 1.

Quantitative synthesis
A summary of the meta-analysis findings of the association between ACE I/D polymorphism and KD risk is shown in  To evaluate the effect of a single article on the final result, we used a sensitivity analysis via removing one study at a time. Ultimately the pooled results hardly changed after removal of each study, suggesting that our results were robust ( Figure 3).

Publication bias
Begg's and Egger's tests were used to assess the publication bias for ACE I/D polymorphism.The shape of the funnel plot did not reveal any evidence of obvious asymmetry, suggesting no evidence of publication bias for ACE I/D polymorphism (Figure 4 and Figure 5).

Discussion
Although the morbidity is highest in Asians, KD is a major cause of acquired heart disease throughout the world 18 . After much investigation,the pathogenesis of KD is still not yet well understood.ACE not only increases vascular smooth muscle cell contraction, but also affects smooth muscle proliferation, monocyte adhesion, platelet adhesion, and aggregation 19,20 . To date,many studies have attempted to analyze the association between ACE I/D polymorphism and KD susceptibility, but the results have been are inconsistent. The aim of this meta-analysis was to investigate the possible association between ACE I/D polymorphism and KD risk based on relevant studies.
In this meta-analysis, we addressed the association between ACE I/D polymorphism and susceptibility to KD. Our results indicated that the ACE I/D polymorphism was significantly associated with the risk of KD. Nevertheless, considering that other potential factors might influence the final result, we conducted sub-group analysis.In a stratified analysis by sample size,pooled results showed significant association with sample size>200 but not with sample size≤200, suggesting that there was no small-study bias in this meta-analysis. The results of our study differ from a previous meta-analysis 21  Several limitations should be acknowledged of the current study. First, in the pooled analysis, we found that the ACE I/D polymorphism was significantly associated with the risk of KD in studies with PHWE<0.05. The data indicated that selection bias or genotyping error may have affected the merged results. Second, only the ACE I/D polymorphism was analyzed in this meta-analysis. Further analysis should clarify the association of other polymorphisms in the RAS genes, such as the AGT M235T and T174M polymorphisms. Third, we were unable to include unpublished studies, which might affect the publication bias. Additionally, there is a lack of infor-mation for the other population outside Asia. Therefore, the results of the current study are not comprehensive.

Conclusion
Our pooled data showed a significant association between the ACE I/D polymorphism and the risk of KD. Due to the defect limitations of the included research, future large-scale investigations with appropriate design are required to confirm association.