Association between ALDH2 rs671 polymorphism and risk of ischemic stroke: A protocol for systematic review and meta analysis.

In last decades, many scholars have studied the relationship between aldehyde dehydrogenase 2 (ALDH2) rs671 and ischemic stroke (IS), however, the results obtained from these studies were inconclusive. The purpose of this study was to investigate the association between rs671 and the risk of IS by systematically review.Two researchers independently screened relevant published literatures, derived data and estimated the risk of bias of the research in Pubmed, Embase, Ovid, China National Knowledge Infrastructure (CNKI), Cochrane Library and China Biomedical Literature Database throughout March 29, 2020. All statistical analyses were performed with the Stata 12.0 software. The data of the study was analyzed using fixed and random effects models. The results were expressed by odds ratio (OR) and 95% confidence interval (95%CI).A total of 10 articles were included this study. The total number of samples for all studies was 5265, including 2762 cases and 2503 controls. Statistical results indicated statistical differences between ALDH2 rs671 polymorphism and IS under dominant model (AA vs. AG + GG) and allelic model (A vs G), ORs (95% CI) were 1.66 (1.27-2.17) (P = .00) and 1.34 (1.05-1.71) (P = .02), respectively. But there was no statistical difference under recessive model (AA + AG vs GG), OR (95% CI) was 1.40 (0.99-1.97), P = .06.ALDH2 rs671 polymorphism was related to IS risk for Chinese population and the A allele of rs671 may be a risk factor of IS.

Introduction

Globally, stroke is a major influencing factor of long-term disability and death.[ In China, about 1.6 million people die from stroke every year, in other words, there is approximately 157 people killed by stroke in each hundred thousand people, so stroke is the main cause of adult disability and death in Chinese populations.[ Ischemic stroke (IS) is the most common type among all stroke types in China. The most common cause for incident IS was the dearterialization of blood in the human brain. The detailed pathophysiological reasons of IS are still unclear, however, several risk factors such as lifestyle, environmental, immune, inflammatory, and hereditary factors have been reported previously.[ Genome-wide association studies (GWAS) have been applied to investigate the relationship between some genetic variants and IS risk previously.[

Some studies indicated that the risk of cardiovascular disease (CVD) will be increased, when the activity of ALDH2 in human body is deficient.[ALDH2 belongs to the stage I oxidase ALDH superfamily, which is mainly involved in ethanol metabolism as well as biogenic and xenogeneic aldehyde detoxification.[ The ALDH2 gene consists of 13 exons and is located at chromosome 12q24 with 46,031 base pairs. The ALDH2 gene polymorphism has an effect on the concentration of acetaldehyde in blood after alcohol metabolism.[ A previous study on the rs671G > A polymorphism shows that the prevalence rate is about 30% to 50% in Asian population,[ mainly lysine (Glu487Lys) substituted glutamine amino acid substitution.[ Several studies found that loss of functional variability (ALDH2 ∗ 1/ ∗ 2 and ALDH2 ∗ 2/ ∗ 2) is associated with the prognosis of several common diseases, including coronary heart diseases,[ hypertension,[ type 2 diabetes[ and stroke.[ In terms of the association between rs671 and IS susceptibility, some studies suggested that rs671 was a positive,[ but also a negative[ risk factor for IS susceptibility. A recent meta-analysis[ was performed on this topic, however, just 9 studies were included in this study, and this our analysis, a new study[ published in 2018 was added. Because the previous results have been contradictory, and a new study was published. Therefore, the purpose of this study was to investigate the extent of connection between rs671 and the risk of IS by screening all available case-control studies for meta-analysis.

Materials and methods

Determination of association research

To confirm all relevant publications on the risk of IS and ALDH2 gene polymorphisms (rs671 G > A), we conducted a systematic search of related literature through a network database, including Web of Science, Pubmed, Embase, Ovid, China National Knowledge Infrastructure (CNKI), Cochrane Library and the Chinese Biomedical Literature Database. The search date for the literature was until March 29, 2020. These terms were used for retrieval: (“aldehyde dehydrogenase2”or “ALDH2”) AND (“polymorphism” or “polymorphisms” or “variant” or “mutation” or “genotype” or “rs671” or “single nucleotide polymorphisms” or “SNP”) AND (“stroke” or “ischemic stroke” or “cerebral infarction” or “cerebrovascular disease” or “cerebrovascular disorder” or “cerebral ischemia” or “brain ischemia” or “brain infarction”). We have included studies on humans and searched for articles written in Chinese and English. The detailed search strategy for each electronic database was shown in Table 1.

Table 1

Search strategy of each electronic database.

Screening criteria

All the researches that met these criteria would be deemed to be eligible including:

the articles are complete;

IS was verified via computer tomography (CT) or magnetic resonance imaging (MRI);

the calculation of studies effect sizes base on enough genotypic data;

case–control studies.

All the studies which did not meet the for-mentioned criteria were excluded, including:

the consequence of studies were not from humans;

the publications are repetition or plagiarize, or without the authority;

the studies lacked genotypic data support;

the studies are not case-control study.

This study should follow the relevant requirements of systematic and meta-analysis.[

Data extraction

Data extraction for the enrolled study was independently extracted by 2 researchers using standard data extraction tables. The data collected for each study is as follows:

First author;

Year of publication;

Nationality;

Gender and average age of the case and control;

Diagnostic criteria of IS;

Hardy-Weinberg equilibrium (HWE);

The number of cases and controls;

Genotyping methods;

Sources of control;

Number of each genotypes in case and control.

If the same study was published multiple times, the publication with the largest number of samples was selected for inclusion in the study. The differences between the 2 researchers were determined through discussion. For the remaining disagreements, the dispute shall be settled by the third investigator.

Quality assessment

The 3 authors of the research used the 9-point Newcastle-Ottawa scale (NOS) to evaluate the selected studies separately.[ If the score was equal to 6 or more, the study will be considered a “high quality study.” Confirmation of all ratings is subject to discussion by all authors.

Statistical analysis

HWE for control group of each study was verified by Chi-Squared test. The correlation between ALDH2 rs671 polymorphism and IS susceptibility was estimated by odds ratio (OR) and 95% confidence interval (95% CI). In the overall meta-analysis, the combined OR values of the dominant models (AA + AG vs GG), the recessive models (AA vs AG + GG), and the allelic models (A vs G) were calculated. Heterogeneity was assessed by Q statistic (P < .10) or I2 statistic (greater or equal to 50% as a basis for significant inconsistency). Once Q-test > 0.10 and I2 < 50%, the calculation of the combined OR was performed using a fixed effect model (Mantel-Haenszel method), otherwise the random effect model (DerSimonian-Laird method) was applied to calculate the combined OR. The publication bias of the literature was analyzed using Begg funnel plot. Sensitivity analysis was used to analyze the effect of selected individual study groups on combined OR. This study used Stata 12.0 analysis software (STATA Corporation, College Station, TX, USA) to perform statistical analysis on the collected data.

Results

Overview of selected literatures

The flow chart of the literature search was shown in Figure 1. After completing the initial screening of several major databases, the inclusion of 146 potentially relevant literatures were required further evaluation. Of these, 49 duplicate references were deleted and 97 were further screened and reviewed by title and abstract. The remaining 11 literatures were reviewed in full text. Finally, 10 literatures were included in this analysis. These literature studies were published from 2012 to 2018. A total of 2503 cases and 2762 controls were included in this study. The genotype frequencies in the control of the 9 studies, except 1 study were distributed accordingly to HWE. The characteristics of the articles involved are summarized in Tables 2 and 3.

Figure 1

The flow sheet of identification of eligible studies.

Table 2

Characteristic of studies included in the meta-analysis.

Table 3

The genotype distribution of ALDH2.

Meta-analysis results

Heterogeneity in the genetic model was analyzed by Q test and I squared statistics. As shown in Figure 2 , a more serious heterogeneity was found under the dominant model (P = .000, I2 = 82.0%) and allelic model (P = .000, I2 = 77.4%), therefore we used a random effects model for analysis. No heterogeneity was found under recessive model (P = .830, I2 = 0.0%), therefore we used a fixed effect model for analysis. Statistical results found statistical differences between ALDH2 rs671 polymorphism and IS under dominant model (AA vs AG + GG) and allelic model (A vs G), ORs (95% CI) were 1.66 (1.27–2.17) (P = .00) and 1.34 (1.05–1.71) (P = .02) respectively. But there was no statistical difference under recessive model (AA + AG vs GG), OR (95% CI) was 1.40 (0.99–1.97), P = .06.

Figure 2

Forest plots of the ALDH2 rs671 polymorphism under different genetic models. a is the dominant model of AA + AG vs GG; b is the recessive model of AA vs AG + GG; c is the allelic model of A vs G.

Sensitivity analysis

A sensitivity analysis was performed to assess the influence of each individual study on the pooled OR by sequentially removing each eligible study at a time. The results of the study show that no studies have affected the effects of the combined OR (Fig. 3 ).

Figure 2 (Continued)

Forest plots of the ALDH2 rs671 polymorphism under different genetic models. a is the dominant model of AA + AG vs GG; b is the recessive model of AA vs AG + GG; c is the allelic model of A vs G.

Publication bias

The publication bias of the literature was analyzed using Begg funnel plot. The results of the study showed that there was no publication bias in the 3 genetic models, all P values were more than .05, which means that the examination did not reveal any significant asymmetry in any of the funnel plots (AA + AG vs GG: P = .466; AA vs AG + GG: P = .466; A vs G: P = .107) (Fig. 4 ).

Figure 3

Sensitivity analysis examining the association between the ALDH2 rs671 polymorphism and risk of IS under dominant model (AA + AG vs GG), recessive model (AA vs AG + GG) and allelic model (A vs G).

Begg funnel plot for publication bias analysis. a is the dominant model (AA + AG vs GG), b is the recessive model (AA vs AG + GG) and c is the allelic model (A vs G) the dominant model (AA + AG vs GG), recessive model (AA vs AG + GG) and allelic model (A vs G).

Begg funnel plot for publication bias analysis. a is the dominant model (AA + AG vs GG), b is the recessive model (AA vs AG + GG) and c is the allelic model (A vs G) the dominant model (AA + AG vs GG), recessive model (AA vs AG + GG) and allelic model (A vs G).

Discussion

There was a great heterogeneity in stroke, and its pathogenesis showed differentiation among individuals. Many genes closely related to CI have been studied by scholars widely, such as interleukin- 4,[ angiotensin IL-1 receptor,[ but the results obtained from these previous studies are still controversial, and the exact mechanism remains to be further studied. As a new biochemical marker of cerebrovascular diseases, ALDH2 has aroused the attention of scholars wildly. ALDH2 belongs to acetaldehyde dehydrogenase family, which is an important member of a family with a high genetic polymorphism. ALDH2 gene is located on chromosome 12q24 and consists of 13 exons. Its coding enzyme protein and peptide chain are composed of 500 amino acid residues.[ At present, a total of 84 SNPs loci have been found in human ALDH2 gene, and the rs671G> A is a mutation site in exon 12, and base substitution occurs: G-A, which causes codon change and the loss of catalytic activity.[ One study on the rs671G> A polymorphism shows that the prevalence rate in Asian population is about 30% to 50%.[ Previously, many scholars have studied the association between ALDH2 rs671 polymorphism and IS, but these studies concluded the contradictory results.[ A recent meta-analysis[ has been performed on this topic, however, just 9 studies were included in this study, and this our analysis, a new study[ published in 2018 for Chinese populations was added. This meta-analysis suggested that the ALDH2 rs671 G>A polymorphism may play an important role in the incident IS by reducing the activity of ALDH2 and interfering with the metabolic processes involving acetaldehyde. The recently published article also indicated that the A allele of ALDH2 gene was an important risk factor for cerebral infarction (CI) incidence. Li et al[ indicated that the ALDH2∗2 allele may be an important negative risk factor for CI in Chinese women. However, the negative effects of ALDH2∗2 allele on CI were not significant, because of the concealing by other risk factors. Sun et al[ randomly selected 6 marker candidate SNPs, including rs671, in a study for the Han population, but they did not find a statistical association between rs671 and IS susceptibility. Another study for the Taiwanese population[ showed that ALDH2 ∗ 2/ ∗ 2 was a possible risk factor for IS in males, but not in females. Wang et al[ also suggested that the rs671 polymorphism of ALDH2 gene was associated with high risk of CI. The rs671 polymorphism of human ALDH2 gene is related to the stability of carotid artery atherosclerotic plaque in the patients with CI.[ Wang et al[ also suggested that ALDH2 gene polymorphism is an independent risk factor for acute CI in the Han population of Heilongjiang province.

Some limitations for the current study should be addressed. Firstly, the number of enrolled studies was not particularly large, all the enrolled subjects were the Chinese population, and some articles were published in Chinese magazines, further replication studies in different population are warranted to confirm our findings. Secondly, the pathogenic mechanisms of IS were extremely complex, too many factors could significantly influence the susceptibility to IS.

In conclusion, our study indicates that rs671 polymorphism may serve as genetic biomarkers of IS, while rs671 polymorphism may contribute to the higher IS susceptibility. Further research should be conducted in different populations to verify our results, such as different races in Asian, European and American populations, and future investigations also need to explore the possible roles of ALDH2 gene- gene or gene- environment interactions on IS susceptibility.

Acknowledgments

We appreciate the cooperation of the families and individuals who cooperated in this study.

Author contributions

Y Jiang and HY Liu searched literature, extracted data, evaluated study quality, and performed statistical analysis. Y Jiang and JT He drafted the manuscript. ZX Xu and Y Jiang designed the study, interpreted the results, and revised and approved the final manuscript.