Although rates have declined, hysterectomy is still a frequent gynaecological procedure. To date, there has been no systematic quantification of the relationships between early/mid-life exposures and hysterectomy. We performed a systematic review and meta-analyses to quantify the associations between age at menarche, education level, parity and hysterectomy.Eligible studies were identified by searches in PubMed and Embase through March 2015. Study-specific estimates were summarised using random effects meta-analysis. Heterogeneity was explored using sub-group analysis and meta-regression.I2 = 0%); summary odds ratio 0.88 . Low education levels conferred a higher risk of hysterectomy in the lowest versus highest level meta-analysis , summary odds ratio 1.51 ) and dose-response meta-analysis  per each level lower of education). Sub-group analysis showed that the birth cohort category of study participants, the reference category used for level of education, the year the included article was published, quality of the study (as assessed by the authors) and control for the key variables accounted for the high heterogeneity between studies in the education level meta-analyses. In the meta-analyses of studies of parity and hysterectomy the results were not statistically significant.Thirty-two study populations were identified for inclusion in at least one meta-analysis. Each year older at menarche was associated with lower risk of hysterectomy—summary hazard ratio 0.86 (95% confidence interval: 0.78, 0.95; The present meta-analyses suggest that the early life factors of age at menarche and lower education level are associated with hysterectomy, although this evidence should be interpreted with some caution due to variance across the included studies. Hysterectomy continues to be one of the most frequent gynaecological procedures performed in more economically developed countries , 2 and hWith such high prevalence, it is important to understand the exposures that occur in earlier life that might predict the risk of hysterectomy to alert practitioners of the need to proactively monitor these women for the benign indications of hysterectomy and implement appropriate treatment pathways. Lower socio-economic status (SES), particularly lower levels of education, have been associated with a higher risk of hysterectomy, however, this varies by geographic location , 12, ethTo date however, there has been no systematic quantification of the relationships between these early/mid-life exposures and hysterectomy. The aim of our study therefore was to systematically review and quantify the evidence from observational studies, through meta-analysis, on the relationship between SES and reproductive factors and hysterectomy.The systematic review and meta-analyses were done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) Guidelines , 24. An We conducted three separate systematic searches in Embase and PubMed: 1) age at menarche, 2) SES, and 3) adult reproductive factors and hysterectomy. The databases were searched for records from inception until March 2015. Full details of the three search strategies are available online in One investigator (L.W.) did the initial screen of titles and the abstracts of articles identified through the initial screening process. Two investigators (L.W. and G.M.) independently reviewed the full text of potentially relevant articles for final inclusion, with any disagreement resolved through discussions.Articles were eligible for inclusion if they 1) reported measures of association and 95% confidence intervals (CI)  for associations between any SES factor, age at menarche or adult reproductive factor and hysterectomy, and 2) had population-based samples or cohorts. Studies that focused on population sub-groups (e.g. veterans), or used hospital-based controls, were excluded.We also contacted several authors , 20, 25 Study quality was assessed independently by L.W. and G.M. using the Newcastle-Ottawa Scale for cohort studies. The scale includes 9 items under three categories: selection, comparability and outcome. Three of the items were not relevant to assessment of cross-sectional studies . Unique scales were developed for each review as elements of the selection and comparability sections are exposure specific , age group of sample (from which we derived the birth cohort of the sample), prevalence of hysterectomy in sample, outcome/comparator groups, measures of association (for the relevant exposure variables) and the covariates used in the model.For all meta-analyses, measures of association were summarised using a random-effects model due to the variability in characteristics between studies. The majority of studies reported either hazard ratios (HR) or odds ratios (OR). We summarised these two types of measures in separate meta-analyses. When articles reported measures of association with different covariates, the most fully-adjusted model was included in the meta-analysis.We conducted meta-analyses on all eligible studies, and also those that only reported adjusted results. If the reference category in the published study was the lowest education level, the inverse of the HR/OR, and the upper and lower confidence intervals, were calculated for inclusion.Studies were eligible for inclusion if they reported a dose-response association or categorical variable with at least three exposure levels. Dose-response measures of association were calculated for each study assuming a log-linear relationship between the exposure and hysterectomy. For the education meta-analysis, the lowest education level category had to be equivalent to “high school or less” and the highest education level category equivalent to “university/college degree or higher”. Highest education level was used as the reference category. Where the lowest education level was used as the reference category, the inverse of the calculated dose-response effect estimates and 95% confidence intervals were used. The HR/OR for a one category change in education level was assumed to approximate the HR/OR for one level lower in education.For age at menarche, the HR/OR for a one category increase was assumed to approximate a per year increase in age at menarche; while for parity, this approximated the HR/OR for a per child increase (with no children as the reference category).2 (Cochrane Q) and I2 statistics. We considered I2 values of 25%, 50% and 75% as cut-off points for evidence of low, moderate and high heterogeneity respectively [Between-study heterogeneity was assessed using the chiectively . Meta-reectively . For theA priori study characteristics considered in our analysis of heterogeneity in the education meta-analyses included: year of publication , study design , whether the definition of hysterectomy included, excluded or did not specify women with malignant conditions, the region in which the study population was selected , birth cohort of the study population , broad population cohort), and cut-off for highest education level . Post hoc, on the basis of additional expert input, prevalence of hysterectomy, adjustment for key confounding variables . Characteristics with a p-value of ≤0.2 were included in the multivariable model , 29.Publication bias was assessed when there were at least ten studies included in the meta-analysis. This waAll analyses were conducted in Stata version 12.1.The numbers of identified and included articles and study populations are summarised in The characteristics of the 32 study populations that were included in at least one of the meta-analyses are summarised in Of the identified study populations, five were cohort and 27 were cross-sectional. Study populations were drawn from nine countries—all were more economically developed locations. The United States was the most common study population setting (n = 14). Study population samples ranged from 276 to 180,982 participants, and hysterectomy prevalence from 3% to 56% (average 20%).For each exposure, data on associations were reported for up to 12 study populations but were not included in our meta-analyses because they used a different reference category, exposure variables were categorized in ways that prevented comparison, or there were an insufficient number of categories to enable a dose-response association to be calculated (details of these study populations are available online in I2 = 0.0%) per year older at menarche (I2 = 61%) per year older at menarche  . Thus, there was no evidence of publication bias  . ResultsI2 = 90%) (I2 = 87%). Results of sub-group analysis and univariable meta-regression on the full set of studies are described in P-value = 0.88. Egger’s regression intercept was -0.85 . Thus, there was no evidence of publication bias  . When stI2 = 85%) per each level lower of education . Thus, there was no evidence of publication bias  per child . When only the Japanese study [I2) was 14%, and the association between parity and hysterectomy increased and was statistically significant . Publication bias was not performed as there were insufficient included studies to properly assess a funnel plot or the results of formal assessments.Random effects meta-analysis of the four studies , 19, 21 er child . Three ose study  was omitI2 = 96%)  . In the The results of the quality assessments are available online in Meta-analyses of the above-mentioned population-based studies revealed a 14% and 12% lower risk of hysterectomy for each year older at menarche in studies reporting hazard ratios and odds ratios respectively. Women with the lowest levels of education had a higher risk of hysterectomy when compared with women with the highest education levels; and there was a dose-response relationship with a 17% higher risk of hysterectomy with each level lower of education. In meta-analyses of studies of parity and hysterectomy, the results (hazard ratios and odds ratios) were not statistically significant.Early menarche has been associated with an increased risk of uterine fibroids –48 and eLower levels of education may impact upon general health and health literacy levels, the capacity to navigate the health system and decision-making skills  or impacModerate to high heterogeneity was prevalent in these meta-analyses, in particular, the education level meta-analyses all had high levels of heterogeneity, indicating that the summary results should be interpreted with caution. Sub-group analysis showed that several factors seem to account for this heterogeneity, including the birth cohort category of study participants, the reference category used for level of education, the year the included article was published, quality of the study (as assessed by the authors) and control for the key variables of age and reproductive factors. While most of these explanatory factors relate to the design of the study and measurement of variables, the birth cohort category of study participants as an explanatory factor indicates that education attainment levels may vary over time and may also be a reflection of changing reproductive trends, increased access to alternative treatments for benign hysterectomy indications and changing treatment preferences among different SES groups .Heterogeneity was less of an issue in the age at menarche meta-analyses. There was no heterogeneity in the age at menarche meta-analysis of study populations reporting hazard ratios ; and in the meta-analysis of study populations reporting odds ratios, the summary result was robust even after omitting studies that showed evidence of contributing to heterogeneity. In the parity meta-analysis of study populations reporting hazard ratios (with moderate heterogeneity) omission of either the UK or JapanTo our knowledge, these are the first meta-analyses to quantify the associations between age at menarche, level of education, parity and risk of hysterectomy. These analyses included only population-based studies to increase generalisability.Our meta-analyses have several limitations. First, all of the included studies were observational so the results cannot be considered causal evidence. Second, the majority of included studies were cross-sectional with the attendant limitations of this design. Recall bias may have impacted in particular on the accuracy of the measurement of age at menarche. In all but one study  this wasThe process of review and data extraction also demonstrated the differences in outcome and exposure definition across the studies. For example differences in definition and categories in the exposure variables prevented meta-analysis of a number of the SES and adult reproductive factors and contributed to the heterogeneity in the lowest versus highest education meta-analysis. There was very little consistency in adjusting variables across the studies, which also contributed to variance. We anticipated that region of study could have contributed to heterogeneity. This was not the case, however the majority of studies were located in more economically developed countries. Ethnicity may have been a more appropriate measure to assess cultural and contextual differences, however, there was insufficient information across studies to explore this.In conclusion, our systematic review and meta-analyses indicate that there is a dose-response relationship between younger age at menarche and lower education levels and a higher risk of hysterectomy. As younger age at menarche, lower education levels and hysterectomy are common risk factors for adverse health outcomes such as diabetes and cardiovascular disease , 58–62 aS1 FileThis file provides full details of the three search strategies undertaken in Pubmed and Embase.(PDF)Click here for additional data file.S2 FileThis file includes the Newcastle-Ottawa Quality Assessment Scales used for each meta-analysis.(PDF)Click here for additional data file.S3 FileThis file includes details of the studies that reported data on relevant associations but were not included in the meta-analyses.(PDF)Click here for additional data file.S4 FileThis file includes the funnel plots assessing publication bias.(PDF)Click here for additional data file.S5 FileThis file includes the results of the quality assessments undertaken for each meta-analysis(PDF)Click here for additional data file.S6 File(PDF)Click here for additional data file.


Methylenetetrahydrofolate reductase (MTHFR), a key enzyme in folate metabolism, had significant effects on the homocysteine levels. The common functional MTHFR C677T polymorphism had been extensively researched. Several studies had evaluated the relationship between MTHFR C677T polymorphism and type 2 diabetes mellitus (T2DM), but the results were still controversial in the Chinese Han population. This meta-analysis was conducted to evaluate the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population.We searched the relevant studies in multiple electronic databases, which published up to December 2013. We reviewed and extracted data from all the included studies on the relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The odds ratios (ORs) and their 95% confidence intervals (95%CIs) were used to evaluate the relationship. Fixed-effects and random-effects meta-analysis were used to pool ORs by the heterogeneity. Publication bias and sensitivity analysis were also examined.29 studies were finally included in our meta-analysis, which contained 4656 individuals with T2DM and 2127 healthy controls. There was a significant relationship between MTHFR C677T polymorphism and T2DM under dominant , recessive , homozygous , heterozygous , and additive  genetic model in a random-effects model. Subgroup analysis also reached similar results. Sensitivity analysis indicated that the overall result were dependable.There was a significant relationship between MTHFR C677T polymorphism and T2DM in the Chinese Han population. The results of our meta-analysis suggested that MTHFR 677T allele might be a risk genetic factor of T2DM in the Chinese Han population. Type 2 diabetes mellitus (T2DM) is one of public health problems, seriously affects individual life quality, and increases individual economic burden. WHO estimates the number of people with diabetes will increase by 114% between 2000 and 2030, and China will become the major site of diabetes epidemic. In a systematic review of 22 studies on diabetes prevalence in China from 2000 to 2010, it increased from 2.6% to 9.7% during this decade Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme involved in folate metabolism, which converts 5, 10- methylene tetrahydrofolate to 5-methyl tetrahydrofolate. Mice deficient in MTHFR have reduced S-adenosylmethionine and increased S-adenosylhomocysteine, show hyperhomocysteinemia and global DNA hypomethylation In recent years, numerous studies had demonstrated an association between MTHFR C677T polymorphism and T2DM. However, the results were not consistent A search strategy was carried out in multiple electronic databases , CBM , and Wanfang databases) before December 2013. The following subject terms were used for searching by ‘methylenetetrahydrofolate reductase or MTHFR’, ‘gene or polymorphism or genetic polymorphism’, ‘Chinese or China’, and ‘diabetes or mellitus or diabetes mellitus or T2DM’. The papers were limited on humans and published in English or Chinese. In order to further identify any additional relevant data, we carefully searched the references in the selected studies.The data from all included studies were independently extracted by two authors (BZ and XW) according to a standard protocol. The third author (LL) resolved the disagreement between two authors. We excluded the studies that did not follow the inclusion criteria, that lacked of sufficient data, or that considered duplicated articles. If we found the same data in different studies, we used the data only one time. The following items were extracted from all included studies: the first author's name, year of publication, region (province), total number of study, gender, genotypic distribution, allele frequencies.We set the inclusion criteria according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) StatementSTATA 11.0 software  was used to perform the meta-analysis. We used five genetic models, which included dominant (TT+CT vs. CC), recessive (TT vs. CC+CT), homozygous (TT vs. CC), heterozygous (CT vs. CC), and additive (T vs. C) models. The odds ratios (ORs) and their 95% confidence intervals (95%CIs) were used to evaluate the association between MTHFR C677T polymorphism and T2DM. We used Chi-square-based Q-tests to assess the heterogeneity between the individual studies 2 test in each included study. The significance set at the P<0.05 in all analyses.We also conducted meta-regression and subgroup analysis to explore the sources of heterogeneity. To assess the reliability of the outcomes in the meta-analysis, a sensitivity analysis was performed by excluding one study at a time. Publication bias was assessed using the Egger's test There was a significant heterogeneity in each genetic model . we usedIn the subgroup analysis based on region, we divided the included studies into two major group, the northern and the southern As shown in This current study, to our knowledge, was the first to use a meta-analysis to evaluate the association between MTHFR C677T polymorphism and T2DM specifically in China. There was a significant relationship between MTHFR C677T polymorphism and T2DM in each genetic model. The prevalence of MTHFR C677T polymorphism varies in the different regions in China As an essential intermediate, homocysteine plays an important role between floate and activated methyl cycle, which is involved in the transfer of activated methyl groups from tetrahydrofolate to S-adenosylmethionine The variation of MTHFR A1298C polymorphism, which was an A to C transition at base pair 1298 resulting in the amino acid transition from Glu to Ala, could also decrease enzyme activity, and lead to hyperhomocysteinemia. The A1298C variation was located in the C-terminal regulatory domain of the MTHFR gene, while the C677T variation was located in the gene catalytic domain In 2013, Khalid et al. found that there was a significant association between MTHFR C677T polymorphism and T2DM in Arab population There are several limitations in our meta-analysis. First of all, the subjects in the included studies were too small, so more large-scale studies were needed to assess the association between MTHFR C677T polymorphism and T2DM. And due to lack of necessary personal information in the included studies, we were unable to further perform subgroup analysis for the relevant influential factors . Second, all included studies were cross-sectional design and all the subjects came from hospitals, their results were not adjusted by the relevant influential factors. They could not infer cause-effect relationship. Third, the development of T2DM was affected by the multiple genes, and our meta-analysis only focuses on MTHFR C677T polymorphism, so the influence of MTHFR C677T polymorphism on T2DM may be affected with other gene polymorphism. Some studies had suggested that ACE insertion/deletion (I/D) polymorphism may act synergistically with MTHFR C677T polymorphism to increase the risk of T2DM In conclusion, our meta-analysis suggested there was a significant association between MTHFR C677T polymorphism and T2DM in the Chinese Han population, and indicated that MTHFR 677T allele might be a risk genetic factor in developing T2DM. Because of the limitations in our study, more large-scale studies need consider the relevant influential factors and other gene polymorphism to verify the results of our study.Checklist S1PRISMA Checklist of this systematic review.(DOC)Click here for additional data file.Checklist S2Meta-analysis on Genetic Association Studies Checklist.(DOCX)Click here for additional data file.


Histidine-rich Glycoprotein (HRG) has previously been shown to have an impact on implantation and fertility. The aim of this study was to investigate if there is an association between the HRG A1042G single nucleotide polymorphism (SNP) and recurrent miscarriage.The study was designed as a case-control study and the women were included at University Hospitals in Sweden. 186 cases with recurrent miscarriage were compared with 380 pregnant controls with no history of miscarriage. Each woman was genotyped for the HRG A1042G SNP.vs 26.3%; p < 0.05). In a bivariate regression analysis, a negative association was found between recurrent miscarriage and heterozygous A/G carriers both in the entire study population  as well as in a subgroup of women with primary recurrent miscarriage . These results remained even after adjustment for known confounders such as age, BMI and thyroid disease .The results indicated that the frequency of heterozygous HRG A1042G carriers was higher among controls compared to cases (34.7% Women who are heterozygous carriers of the HRG A1042G SNP suffer from recurrent miscarriage more seldom than homozygous carriers. Thus, analysis of the HRG A1042G SNP might be of importance for individual counseling regarding miscarriage. Recurrent miscarriage was defined as three or more consecutive pregnancy losses before 20 weeks of gestation . Since tIt affects approximately 1-5% of fertile couples  and the Angiogenesis, which refers to the formation of new blood vessels from preexisting ones, is required during embryonic development as well as in implantation and placentation. Based on this hypothesis several studies have been performed examining the potential contribution of genetic polymorphisms encoding angiogenic mediators  ,11. One HRG might be involved in several of the processes of importance for a pregnancy to occur but the exact role of HRG in fertility is not yet fully described. We have previously shown that HRG exists in the reproductive system as well as in the embryo  and it iIn another SNP of the gene, named HRG A1042G, an adenine (A) nucleotide is replaced by a guanine (G), which results in a change from histidine to arginine at amino acid position 340 in the protein. HRG A1042G is localized in the histidine/proline (His/Pro) rich region, which is known to mainly regulate the anti-angiogenic capacity of HRG . No studThe study was designed as a case-control study. Cases (n = 186) were recruited from the Department of Obstetrics and Gynaecology at Uppsala University Hospital, Karolinska University Hospital, Huddinge University Hospital and Danderyd University Hospital, Sweden. Eligible cases with a diagnosis of recurrent miscarriage, defined as three or more verified consecutive miscarriages in the first or second trimester of pregnancy (5-21 completed weeks of gestation), were identified in the out-patient registers of the participating clinics and invited to participate in the study. The women were included between April 29, 2009 and June 30, 2010 sometimes years after the initial incidence. Women with known risk factors for recurrent miscarriage, such as systemic lupus erythematosus, diabetes mellitus type 1, severe thrombophilia and major chromosomal aberrations were not included in the study.The control subjects (n = 380) were randomly chosen from the Uppsala University Hospital biobank of pregnant women. Since May 31, 2007, all women aged 18 and older attending the second trimester (16-19 weeks of gestation) routine ultrasound scan at Uppsala University Hospital have been approached for inclusion in this biobank, and inclusion to our study was ongoing until June 30, 2010. All control subjects were followed until delivery and only term pregnancies fulfilled the inclusion criteria. In the control group, no woman had a history of miscarriage or was treated with anti-thrombophilic medication (such as Low Molecular Weight Heparin or Aspirin) and 75% had at least two spontaneous pregnancies, including the ongoing pregnancy, resulting in a term (≥37 weeks) birth of a live infant. Thirty-two percent of our cases had already a child before recruitment. Cases and controls differed only in their obstetric record but had otherwise similar inclusion and exclusion criteria.Both cases and controls attended a brief health examination including measurements of weight and height and answered standardized questions on reproductive history. Furthermore, we reviewed the medical records to obtain relevant information on pregnancy outcomes, health problems and medication. According to routine clinical procedures, TSH-levels were analysed in all women when diagnosed with recurrent miscarriage. Among cases hypothyroidism was defined as TSH above the current defined upper limit of the reference range at the different hospitals. Pregnant controls at high risk for thyroid disease were subjected to selected TSH screening according to local guidelines based on international recommendations. This case-finding procedure was applied in first or early second trimester of pregnancy, before routine ultrasound scan and inclusion in the study. Since ethnicity affects genetic variation, the population distribution was then investigated on our study group. It was found that 94.6% (176/186) of cases and 95.5% (363/380) of controls were of Caucasian origin and the frequency did not differ statistically between the two groups (p = 0.89). All the analyses that follow are performed in an ethnically mixed group.A post hoc power calculation, where a Chi-square test with an alpha-value of 0.05 was used, gave a post hoc power of 0.97.The study was approved by the Regional Ethical Review Boards in Uppsala and Stockholm, Sweden. Informed consent was obtained from all women included in the study. No reimbursement was given to participating patients.g for 10 min. Plasma and buffy coat were separated, transferred to new tubes and stored at -20°C.Blood samples were collected in EDTA-containing tubes and centrifuged at 1500 Genomic DNA was extracted from buffy coat using QIamp DNA Blood Maxi kits . The samples were genotyped for the HRG A1042G (rs2228243), using the TaqMan SNP Genotypning Assay . Briefly, polymerase chain reactions were performed in a 96-well plate in total volume of 25 μl for each well. Each reaction consisted of 1xTaqMan Universal PCR Master Mix , 1× SNP Genotyping Assay  and 10 ng of genomic DNA. Cycling conditions were initiated for 10 min at 95°C followed by 40 cycles of 15 s at 92°C and 1 min at 60°C. Real-time fluorescence detection was performed. Sequence Detection system Software (Applied Biosystems) was used to plot fluorescence (Rn) values based on the signals from each well. The plotted fluorescence signals indicated which alleles were present in each sample.2) defined as BMI recorded at inclusion (cases) or BMI at first antenatal visit (controls) , smoking during pregnancy (yes/no) defined as smoker during ≥ 1 pregnancy ending with miscarriage (cases) or smoker at first visit to the prenatal center in gestational week 10 (controls), and genotype . A p-value < 0.05 was considered as significant. All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) 20.0 for Windows software pack .Demographic and clinical characteristics were compared between cases and controls or genotype groups using Student’s t-test, Mann-Whitney U test, Chi square test and Kruskal-Wallis test. At first, a logistic regression analysis was performed examining the association between HRG A1042G SNPs and recurrent miscarriage. Secondly, in a subgroup analysis where only women with primary recurrent miscarriage were included (defined as recurrent miscarriage and no known children either before or after diagnosis), a comparison with controls was performed using Student’s t-test and Chi-square test. A logistic regression model was composed. A number of possible confounders were considered for inclusion in the regression model; age, pre-pregnancy smoking, BMI, thyroid disease and genotype. Only variables with a possible association with exposure and outcome  were entered into the final model. Adjusted odds ratios (AOR) for recurrent miscarriage were calculated in logistic regression analyses including the following variables: maternal age as completed years at the first pregnancy or first miscarriage , body mass index , and as expected, hypothyroidism was more common in women with recurrent miscarriage . All women were genotyped according to the HRG A1042G SNP and the frequency of heterozygous (A/G) carriers was significantly higher among controls compared to cases  and controls (n = 380) are shown in Table 86 and coAmong all the 566 women genotyped for HRG A1042G SNP, 359 (63.4%) of them were homozygous for adenine (A/A), 181 (32%) were heterozygous (A/G) and 26 (4.6%) were homozygous for guanine (G/G) .vs 16.3%, p < 0.05). To further investigate the impact of the HRG A1042G SNP on recurrent miscarriage a logistic regression analysis was performed on this subgroup of women. A significant association between women carrying the heterozygous HRG A1042G SNP and recurrent miscarriage was identified, with a decreased risk of recurrent miscarriage among these women . As expected, hypothyroidism was associated positively with recurrent miscarriage . Other known confounders such as age, smoking and BMI were not associated with recurrent miscarriage  ,21, and In the present study, a possible association between the HRG A1042G SNP and recurrent miscarriage has been investigated. We found that among women with recurrent miscarriage there was a decreased occurrence of heterozygous HRG A1042G SNP carriers and the association was even stronger in the group with primary recurrent miscarriage. Previous computational studies have shown that the amino acid shift in position 340 related to that specific SNP is predicted to be benign or tolerated according to Polyphen-2 and SIFT respectively (position-specific independent count score 0.227 and tolerance index 0.34) . AlthougThe establishment of a pregnancy requires adequate regulation of angiogenesis, coagulation, as well as regulation of immunological pathways . Developin vitro fertilization [We have previously shown that HRG might be of importance in early pregnancy and this is supported by our prior results indicating an association between the presence of HRG in placenta and risk of preeclampsia during pregnancy , as welllization .2+- dependent inhibitory effect on vessel formation both in vitro and in vivo. HRG 330-364 attached to heparin/heparan sulfate with equal capacity as full-length HRG. Peptides corresponding to other regions than the His/Pro-rich region of HRG-downstream of HRG 330-364 -lacked this inhibitory effect on endothelial cell migration and displayed a notably reduced heparin-binding capacity. The importance of this region in HRG was furthermore confirmed by Lee et al. [The HRG A1042G SNP studied in this manuscript, which corresponds to a mutation in the His/Pro rich domain of HRG, was of interest based on previous knowledge indicating that this domain of HRG is important for the regulation of angiogenesis. Van Wildemeersch et al.  has prese et al. . The late et al.  which isThe exact pathway by which HRG exhibits its anti-angiogenic effect is not yet fully described; it seems nevertheless to be carried out through simultaneous multifactorial interaction. The His/Pro-rich region of HRG has been proposed to act through binding of cells at sites of tissue injury and thereby regulating the activity of degradative enzymes such as the plasminogen/plasmin system . However2+ concentration can induce a conformational change of the His/Pro rich domain and hence promote its binding to endothelial cells via heparan sulfate [Another factor that stimulates the anti-angiogenic effect of HRG has been described to be blood platelets in an activated state. Activated maternal platelets were found in the lumen of the spiral arteries after histological examination of human placental tissue . In an a sulfate ,20.Despite the latter, one should always be cautious in interpreting genetic associations since there is always a possibility that the reported results represent a chance finding. It should however be noted that the background to the current hypothesis is based on a robust and widely accepted association between recurrent miscarriage and impaired implantation/placentation, due to inadequate angiogenesis . One of In conclusion, our results indicate an important role for HRG A1042G SNP in early pregnancy. It is shown that women who are heterozygous carriers of the HRG A1042G SNP suffer from recurrent miscarriage more seldom than homozygous carriers. Thus, analysis of the HRG A1042G SNP might be of importance for individual counseling regarding miscarriage.ACOG: American college of Obstetricians and Gynecologists; ASRM: American society for reproductive medicine; ESHRE: European society of human reproduction and embryology; HRG: Histidine rich glycoprotein; NVOG: Dutch society of Obstetrics and Gynaecology; RCOG: Royal college of Obstetricians and Gynaecologists; SNP: Single nucleotide polymorphism; VEGF: Vascular endothelial growth factor.The authors declare that they have no competing interests.EE performed the statistical analysis and interpretation of results, drafted, edited and reviewed the manuscript. KEL assisted in data analysis and in drafting the manuscript. HK, FH, KB, BML and LSS participated in the design of the study and acquisition of data. ASE participated in the design of the study, acquisition of data and in drafting the manuscript. AS assisted in data analysis, interpretation of data and in drafting the manuscript. ISP supervised the study, assisted in data analysis, interpretation of data and in drafting the manuscript. HÅ conceived of the study, participated in its design, assisted in the statistical analysis and interpretation of data, drafted, edited and reviewed the manuscript. All authors read and approved the final manuscript.


Although previous studies found that cigarette smoking is associated with risk of rheumatoid arthritis (RA), the dose-response relationship remains unclear. This meta-analysis quantitatively summarizes accumulated evidence regarding the association of lifelong exposure to cigarette smoking assessed as pack-years with the risk of RA.Relevant studies were identified by a search of MEDLINE and EMBASE from 1966 to October 2013, with no restrictions. Reference lists from retrieved articles were also reviewed. Studies that reported relative risks (RR) or odds ratio (OR) estimates with 95% confidence intervals (CIs) for the association between pack-years of cigarette smoking and rheumatoid arthritis were included in a dose-response random-effects meta-regression analysis.Pheterogeneity = 0.32) and publication bias did not affect the results. Compared to never smokers, the risk of developing RA increased by 26%  among those who smoked 1 to 10 pack-years and doubled among those with more than 20 pack-years . The risk of RA was not increasing further for higher exposure levels . The risk of RA was statistically significantly higher among rheumatoid factor (RF)-positive RA cases  compared to RF-negative  when comparing the highest versus lowest category of pack-years for the individual studies.We included 3 prospective cohorts and 7 case-control studies in the meta-analysis. They included a total of 4,552 RA cases. There was no indication of heterogeneity (Lifelong cigarette smoking was positively associated with the risk of RA even among smokers with a low lifelong exposure. The risk of RA did not further increase with an exposure higher than 20 pack-years. Cigarette smoking is considered an established risk factor for the development of rheumatoid arthritis (RA), an autoimmune inflammatory disease. This was confirmed by a published meta-analysis on smoking and risk of RA that showed a 40% higher risk among ever smokers compared to never smokers . HoweverThe aim of the present study was to quantitatively summarize the accumulated evidence on the relation between lifelong exposure to cigarette smoking and risk of developing rheumatoid arthritis by performing a dose-response meta-analysis. As a measure of lifelong exposure we used pack-years of smoking., “smoking”, “cigarette smoking” or “pack-years”, with no restrictions. Studies were excluded if they did not meet the selection criteria: use of an observational design (cohort or case-control design), examination of smoking as the main exposure and RA as the main outcome, reporting relative risks or odds ratios of RA for categories of pack-years . In case of multiple publications from the same study, we selected the publication with estimates on the entire study cohort [We searched MEDLINE and EMBASE databases for relevant studies published from 1966 through October 2013 using the search terms “rheumatoid arthritis” or “RA” combined with “smoke”y cohort , insteady cohort  or anticy cohort .From each study we extracted information regarding publication data , number of RA cases, cohort size or number of controls, follow-up period for cohorts and study period for case-control studies, exposure specific relative risk or odds ratio estimates with their corresponding 95% confidence intervals (CIs), and variables controlled for in the multivariable model Table . From eaThe study quality was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOQAS) for cohort and case-control studies, with which each study was judged based on the selection of the study groups, the comparability of the groups, and the ascertainment of exposure and outcome . The scoet al. [P = 0.078). However, the restricted cubic spline model resulted in the best fitting model in terms of the Akaike Information Criterion (AIC) when comparing it against a linear model .We conducted a two-stage dose-response random-effects meta-regression analysis ,12, and et al.  to calcuet al. , we combet al. . The midet al. , which rWe additionally performed a random-effects meta-analysis comparing the highest versus the lowest category of pack-years within each specific study. For this analysis the approach developed by DerSimonian and Laird was used . We cond2 statistic [P-values are two-sided. All statistical analyses were carried out with Stata, version 12.1 .In all meta-regression models, statistical heterogeneity between studies was evaluated with the Cochran’s Q-test and the Itatistic , which atatistic . All repOf the 29 studies that reported an estimate of the association between cigarette smoking and rheumatoid arthritis, only 3 cohort studies ,5,20 andIn a dose-response analysis, we modeled the relationship between pack-years of cigarette smoking and RA risk using a restricted cubic splines model. The non-linear dose-response trend Figure  showed aPheterogeneity = 0.32). There was no evidence of publication bias .The comparison of the highest vs. the lowest categories of pack-years of smoking from the individual studies was in line with the results from the dose-response analysis showing a two-fold increase of RA risk . A sensitivity analysis excluding one study at a time showed that the overall RRs ranged between 1.92 and 2.10. Q test for heterogeneity of the results between specific studies was not statistically significant  among cohort studies and 2.19  among case-control studies  among women and 2.22  among men. Four studies reported estimates for RF-positive RA [Pheterogeneity = 0.88), while it was 1.58  among RF-negative cases. These estimates were statistically significantly different .We conducted stratified analyses by study design, gender and rheumatoid factor type. The RR comparing the highest vs. the lowest category of pack-years of smoking was 1.83 . Moreover, the pooled estimate from this meta-analysis could have been affected by a potential residual confounding from each study. In particular, the numbers of confounders taken into account by the case-control studies included in this meta-analysis were in general limited. This could explain the difference between the pooled OR from case-control studies and the pooled RR from prospective cohort studies. Moreover, this difference could also be explained by the different study populations: prospective cohort studies analyzed only women while all case-control studies except one  includedHLA-DR SE genes in triggering and persuading immunity against citrullinated proteins, and that this immunity is specific for RA [The biological effect of smoking in the development of rheumatoid arthritis is still unclear. However, it is known that certain cigarette smoke components, such as nicotine, hydrocarbons and carbon monoxide, may enhance immune reactions, and it has been found that in certain inbred strains of rodents these components cause arthritis without contributions from other agents -27. Morec for RA ,28. The c for RA  than RF-Our study showed some evidence of a non-linear dose-response relationship between lifelong smoking and risk of RA. The risk increased at a relatively low level of lifelong exposure to smoking (≤10 pack/years) and stabilized to approximately a double risk for a smoking exposure higher than 20 pack-years.ACPA: anticitrullinated protein antibody; AIC: Akaike Information Criterion; CI: Confidence interval; NOQAS: Newcastle-Ottawa Quality Assessment Scale; OR: Odds ratio; RA: Rheumatoid arthritis; RF: Rheumatoid factor; RR: Relative risk.The authors declare that they have no competing interests.DDG, AD, NO and AW participated in the study design and in writing the manuscript. DDG, AD and NO participated in the data collection. DDG analyzed the data and wrote the manuscript under the supervision of AW. DDG, AD, NO and AW interpreted the data and critically reviewed the paper. All authors read and approved the final manuscript.


RIT2) polymorphism, rs12456492, with Parkinson’s disease (PD) are controversial. We performed a meta-analysis to study the association between rs12456492 and PD susceptibility in Asian populations. Literature searches of PubMed and Embase were performed up to June 3, 2015, and the strength of the association between rs12456492 and PD was evaluated by odds ratios (OR) and 95% confidence intervals (CI). Four studies conducted between 2013 and 2015, comprising 2017 PD cases and 2010 controls, were included in the meta-analysis. Significant association of rs12456492 with PD was found in the dominant  and additive models . Although sensitivity analysis found that the overall result was stable only in the dominant genetic model, a publication bias was also detected. Therefore, the results should be treated with caution. The current meta-analysis suggested that rs12456492 might be associated with increased PD risk in Asian populations, but studies using larger sample sizes and different ethnic populations will be needed to further confirm this association.Recent studies investigating the association of the Ras-like without CAAX 2 ( LRRK2, PARKIN, DJ1, ATP13A2, VPS35, PINK1, and SNCA34Parkinson’s disease (PD) is an age-related, progressive, complex neurodegenerative disease, which significantly affects quality of life and affects approximately 1% of people over 60 years of age. The disease is characterized behaviorally by motor and non-motor symptoms and pathologically by aggregations of the α-synuclein protein1SNCA, GBA, MAPT, and HLA6et al. identified an association between a polymorphism in Ras-like without CAAX 2 (RIT2), rs12456492, and PD risk in a large White population when performing a meta-analysis of GWAS resultset al.910et al. found no association between rs12456492 and PD in a Taiwanese populationRecently, several genome-wide association studies (GWAS) have identified numerous genes associated with sporadic PD, including Literature searches were performed using PubMed and Embase. The search strategy was based on the following search terms, “Parkinson’s disease or PD” and “Ras-like without CAAX 2 or RIT2 or Rin or rs12456492” and “polymorphism or mutation or variation or SNP”, with the last report up to June 3, 2015. All eligible studies were retrieved, and their bibliographies were examined for relevant publications.The inclusion criteria for studies were as follows: (1) association shown between rs12456492 and PD risk in Asian populations; (2) case-control design; and (3) available phenotype or allele frequencies of rs12456492 in cases and controls. Abstracts from conferences, studies without sufficient data for odds ratios (OR) and 95% confidence intervals (CI), republished or duplicate studies, and reviews were excluded.Data from eligible studies were extracted by Yanjun Lu and Wei Liu, according to the above inclusion and exclusion criteria. The following information was collected from each study: the first author, year of publication, country, ethnicity of the sample population, sample size, phenotype distribution, and minor allele frequency (MAF).2 tests were used to investigate the heterogeneity between studies. If P > 0.10 for the Q-test, or if I2 < 50%, the fixed-effect model was used to calculate the pooled ORs; if P < 0.10 for the Q-test, or if I2 > 50%, the random-effect model was applied. Sensitivity analysis was carried out by sequentially omitting one study at a time to estimate the stability of the result. Publication bias among studies was determined using Begg’s test and Egger’s test.Data were analyzed by STATA software, version 11.0 . Hardy Weinberg equilibrium (HWE) in the control group of each study was examined, and P < 0.05 was considered as departure from HWE. The association between rs12456492 and risk of PD was evaluated by pooled OR and 95% CI. Four genetic models, including the allelic (G vs. A), dominant (GG + AG vs. AA), recessive (GG vs. AG + AA), and additive (GG vs. AA), were used to analyze the association. The significance of the pooled OR was assessed by the Z test, and P < 0.05 was considered as statistically significant. The Q-test and Iet al. departed from HWE (P = 0.03), and their data were therefore excluded from further meta-analysis91012et al. chose an Asian population in IranThe selection process of studies included in this meta-analysis is shown in 8Q and I2. We found that rs12456492 was significantly associated with an increased risk of PD in the dominant and additive genetic models in the pooled Asian populations , and the results showed that rs12456492 was significantly associated with PD in all four genetic models in the subgroup with a MAF < 0.5 .Meta-regression was performed to explore the source of heterogeneity, considering the publication year and MAF (>0.5 vs. <0.5) as possible covariates. No covariate significantly contributing to the heterogeneity in any genetic model was found . Howeveret al.’s study, rs1245692 was associated with PD . In the additive genetic model, the sensitivity analysis showed that the result was not stable . In the dominant genetic model, the sensitivity analysis showed that the result was stable . These data implied that our meta-analysis results were not robust in the allelic, recessive, and additive genetic models but remain stable in the dominant genetic model in Asian populations.The sensitivity analysis showed that in the allelic and recessive genetic models, after omitting Lin Publication bias was assessed by Begg’s test and Egger’s test. A publication bias was found in the dominant genetic model. A trending bias also existed in the recessive and additive models  is a member of the Ras superfamily of small guanosine triphosphate binding proteins localized on the plasma membrane. RIT2 is specifically expressed in neurons, and preferentially expressed in the dopaminergic neurons in the substantia nigra (SN)et al. did not find a significant association between rs12456492 and PD risk. As a negative result might not be as readily accepted for publication as a positive result, this could be a contributing factor to the publication bias that we found in the rs12456492 investigation. These results indicated that the number of studies included in the meta-analysis was insufficient. Our meta-analysis suggested that although a significant association of rs12456492 with PD risk was found in the pooled population in some of the genetic models, the results should nonetheless be applied cautiously due to the instability caused by the limited number of studies and the sample size.We investigated the four selected studies carefully. Significant association of rs12456492 with PD risk was found in the pooled Asian population in the dominant and additive genetic models. Stratified analysis by MAF showed a significant association of rs12456492 with PD risk in all four genetic models in the subgroup with MAF < 0.5. We performed a meta-regression analysis to investigate the source of heterogeneity, although we failed when considering the publication year and MAF. MAF tended to influence the heterogeneity in the allelic and recessive genetic models , as rs12456492 was significantly associated with PD risk in the two genetic models in MAF < 0.5 subgroup. The sensitivity analysis showed that the association between rs12456492 and PD susceptibility was robust only in the dominant genetic model. However, a publication bias existed in the dominant genetic model, and a trending bias existed in the recessive and additive models. Of the four studies included in the meta-analysis, only Lin http://www.ncbi.nlm.nih.gov/projects/SNP/snp_ref.cgi?rs=12456492) showed that the frequency of allele G was 0.375 and 0.339 in Chinese and Japanese populations, respectively. In an Asian population, the highest MAF was 0.5. In the four studies included in the current meta-analysis, three of them had a MAF < 0.5, while Lin et al.’s data had a MAF > 0.5. The discrepancy of these results might be due to the genetic heterogeneity between different regions, as Lin et al.’s study included a Taiwanese population, while two other studies included a Chinese population from mainland China. This suggests that the complex etiology of PD is influenced by both hereditary and environmental factors. Moreover, in the study by Lin et al., both late-onset PD (62%) and early-onset PD (38%) patients were recruited, and the early-onset PD patients had an age of onset of less than 50 years. However, the mean ages of onset in the other three studies was greater than that in the study by Lin et al., and age might have influenced the heterogeneity and association. Due to insufficient data, we did not examine the contribution of age to heterogeneity in our meta-regression analysis. Therefore, experimental research and human studies with larger sample sizes, different ethnicity, and rigorous design are needed to further clarify this association.Differential associations of rs12456492 with PD susceptibility between different MAF groups might be due to the varying genetic backgrounds and sample sizes. Data from the PubMed SNP database .


Epidemiologic studies have reported various results relating phytoestrogens to prostate cancer (PCa). The aim of this study was to provide a comprehensive meta-analysis on the extent of the possible association between phytoestrogens (including consumption and serum concentration) and the risk of PCa.Eligible studies were retrieved via both computer searches and review of references. The summary relative risk ratio (RR) or odds ratio (OR) and 95 % confidence interval (CI) were calculated with random effects models.A total of 11 studies (2 cohort and 9 case–control studies) on phytoestrogen intake and 8 studies on serum concentration were included in the meta-analysis. The pooled odds ratio (OR) showed a significant influence of the highest phytoestrogens consumption  and serum concentration  on the risk of PCa. In stratified analysis, high genistein and daidzein intake and increased serum concentration of enterolactone were associated with a significant reduced risk of PCa. However, no significant associations were observed for isoflavone intake, lignans intake, or serum concentrations of genistein, daidzein, or equol.The overall current literature suggests that phytoestrogen intake is associated with a decreased risk of PCa, especially genistein and daidzein intake. Increased serum concentration of enterolactone was also associated with a significant reduced risk of PCa. Further efforts should be made to clarify the underlying biological mechanisms. Prostate cancer (PCa) was the second most frequently diagnosed cancer and the sixth leading cause of death from cancer among men worldwide in 2008 according to the estimate of the International Agency for Research on Cancer . The worPhytoestrogens, which have structural and functional similarities to 17b-oestradiol, are believed to have a prophylactic effect on PCa , 9. IsofAccording to 2 previous meta-analyses , 14, conTherefore, we performed a meta-analysis to address this gap. We updated and assessed quantitatively the association between intake of isoflavones and lignans and risk of PCa from the cohort and case–control studies. We also investigated the association between serum concentration of phytoestrogens and their metabolites and the risk of PCa.We identified relevant publications in the MEDLINE database using PubMed, Web of Science, and the Cochrane Library up to June 2014. Search terms included “phytoestrogens,” “isoflavones,” “lignans,” “flavonoids,” “genistein” or “daidzein,” “glycitein,” “equol,” “enterolactone,” and “enterodiol,” combined with “prostate cancer” or “prostatic carcinoma”. Two of the authors (SW and JH) reviewed the titles and abstracts independently to exclude any clearly irrelevant studies. The full texts of the remaining articles were read to determine whether they contained information on the topic of interest. Any disagreements were resolved by discussion. Furthermore, references in the retrieved publications, as well as those in previous reviews , 16, werTo be included, studies had to fulfill all of the following inclusion criteria: (i) case–control or cohort study published as an original article reported in English between 1980 and February 2014, (ii) estimated the relationship between phytoestrogens (intake or serum concentration) and the risk of PCa, (iii) provided a risk estimate relative risk (RR) [or odds ratio (OR)] and its 95 % confidence intervals (CI) or sufficient information allowing us to compute them, and (iv) adjustment made for age and potential risk factors. In studies with overlapping patients or controls, only the latest or the most informative were included. Any study with inconsistent or erroneous data was excluded. Meeting abstracts with insufficient data or unpublished reports were not considered. We included all methods for measuring exposure to phytoestrogens such as questionnaires, interviews, and serum level or urinary excretion. We did not include studies that used tumor-related biomarkers (such as PSA) as outcome. We also exclude data concerning phytoestrogens and the risk of recurrent PCa.For each study, the following characteristics were extracted: last name of first author, publication year, country in which the study was conducted, study design, population type and sample size, adjustment for potential confounders, definition of phytoestrogens exposure status, and estimates of associations. The levels of phytoestrogens exposure varied considerably among the studies, so we extracted the most adjusted risk estimate of the highest reported category of phytoestrogens exposure relative to the lowest from these studies for comparison.2 score were used to assess the between-study heterogeneity of results [P < 0.05.The ORs were used as the common measure of association across studies by considering the RRs as ORs. The data from individual studies were pooled by use of the random effects model with the DerSimonian-Laird method , which c results , 19. Pub results  and the  results . If publ results  was usedThe detailed steps of our literature search are shown in Fig. 2 = 47.7, P = 0.039). We used meta-regression analysis to explore the influence of publication year, study design, sample size, and study conducted area. However, none was identified as a possible source of heterogeneity among all the included studies (data not shown). Further scrutiny found that the heterogeneity was reduced when the analysis was stratified by geographical region  and Egger’s test (P = 0.021) for publication bias were significant. The trim and fill analysis yielded the same conclusions without evidence of any potentially missed unpublished studies.We found that phytoestrogen intake  was statistically significantly associated with reduced risk of PCa with significant heterogeneity (IP = 0.035) among the eight studies evaluating daidzein intake and the risk of PCa. In contrast, there was no evidence of heterogeneity among studies of genistein, lignans, and isoflavones.In stratified analysis of individual types of phytoestrogens see Fig. , eight sP = 0.083), while the Egger’s test provided evidence for publication bias (P = 0.005). We used the trim and fill method to estimate the missing studies. The result yielded the same conclusions without evidence of any potentially missed unpublished studies.The Begg’s tests and Egger’s test provided no evidence of publication bias for daidzein and isoflavones (data not shown). However, for genistein analysis, the Begg’s tests indicated no substantial publication bias . When stratified analysis was conducted of individual types of serum phytoestrogens, only serum enterolactone was inversely associated with the risk of PCa with no heterogeneity (P = 0.183) (see Fig. We identified 10 studies that had investigated the association between serum phytoestrogen concentration and the risk for PCa. We excluded two studies , 36 becaas P = 0.97. When as P = 0.97. When This meta-analysis demonstrated that consumption of phytoestrogens was associated with a reduction in PCa risk of 20 % in men when the highest reported intake was compared with the lowest reported intake. The results of our separate analysis based on the type of phytoestrogens showed inverse associations for the consumption of genistein and daidzein and with increased serum concentrations of enterolactone. However, no significant associations were observed for isoflavone intake, lignan intake, or serum level of genistein, daidzein, and equol.It has been suggested that phytoestrogens may prevent cancer by a variety of mechanisms, including sex and/or growth hormone regulation, antioxidant properties, apoptosis of PCa cells, and/or inhibition of angiogenesis, invasion, and metastasis , 44. TheDue to the potential benefits, there have been six randomized controlled trials –56 that It is worth noting that in our analysis, stratification by region yielded a significant inverse association with PCa risk for studies in Asian populations, a marginally significant inverse association with risk for studies in US populations but no significant association with risk for those in Europe populations. This difference may, in part, be due to differences in environment and dietary patterns in these regions. Characterization of the individual variability as defined by the gut microflora composition and gene polymorphisms  may alsoAs a meta-analysis of previously published observational studies, our study has several limitations that need to be taken into account. First, only English language articles were included. We did not attempt to uncover unpublished observations and did not include studies with insufficient information to estimate an adjusted OR, which could bring publication bias, even though the trim and fill analysis yielded the same conclusions without evidence of any potentially missed unpublished studies. Second, for now, the two available cohort studies could not provide sufficient data for meta-analysis, so we have to choose case–control studies as the data resource for analysis. In addition, because some items were combined only from three studies, the total numbers of cases remained low. Third, the intake levels of phytoestrogens in the lowest and highest categories and the range of consumption level varied across studies. Moreover, food frequency questionnaires which assess dietary habits may lead to measurement errors. It is not only due to recall bias but also to the estimation by using different food composition databases, which may not be complete for the whole range of foods consumed. On the other hand, variation in individual metabolism of phytoestrogens due to differences in gut microflora and measurement in a single blood or urine sample may only reflect recent dietary intake. These differences may have contributed to the heterogeneity among studies. To be honest, phytoestrogen spectrum and content varies between the plant species, sort, and origin. Even the same molecule arising from the different sources can exert various effects. It may not be excluded that synthetic phytoestrogens with desirable structure and activity could be an easier and safer alternative of the traditional plant product of variable origin, phytoestrogen content, and activity. Several studies are going on developing novel and more selective synthetic phytoestrogens.Our findings support the hypotheses that serum enterolactone and consumption of genistein and daidzein protect against PCa risk. Interestingly enough, an association between PCa risk and isoflavone intake or serum concentrations of its metabolites was not found. The complexity of phytoestrogen composition and its metabolism make the evaluation of the effect of phytoestrogen on PCa very difficult. In the light of these findings, further prospective epidemiological studies using improved food databases and experimental studies are needed to identify the specific compounds that provide protection, to determine precisely how the complex metabolism of phytoestrogens may interact with other mechanisms to prevent cancer. Synthetic phytoestrogens with desirable structure and activity could be an easier and safer alternative of the traditional plant product.


UGT2B17 deletion polymorphism has attracted studies to evaluate the association between the UGT2B17 deletion polymorphism and tumor risk in diverse populations. However, the available results are conflicting.UGT2B17 is a vital member of the UGT2 family and functions as a detoxification enzyme which catalyzes the glucuronidation of lipophilic compounds. Accumulating evidences implicates that it may contribute to the susceptibility of tumor risk. Identification of a A meta-analysis based on 14 studies from 10 publications including 5,732 cases and 5,112 controls was performed. Published literature from PubMed, EMBASE and Web of Science was pooled and the crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of the associations.UGT2B17 deletion polymorphism were associated with tumor risks  in a recessive model. However, after excluding two studies for their heterogeneity, the result then demonstrated that the UGT2B17 deletion polymorphism was not associated with tumor risks . A subgroup analysis based on tumor type, sex or race did not show significant results.Conclusively, our results indicate that individuals with a UGT2B17 deletion polymorphism is not associated with tumor risks.These results suggest that the  Tumors are a multifactorial disease and have become a major global public health burden in recent years. However, the precise mechanism of carcinogenesis is complicated and still remains to be identified. Studies have demonstrated that tumors are a result of the intricate interactions between interior and environmental factors UDP-glucuronosyltransferases (UGTs) are a family of phase II detoxification enzymes which catalyze the glucuronidation of lipophilic compounds like drugs, dietary substances, tobacco toxins and environmental xenobiotics UGT2B17 genes are clustered on chromosome 4q13 and have a high level of cDNA and amino acid sequence homology with other UGT2B enzymes UGT2B17 gene UGT2B17 is involved in the etiology of various tumors. An individuals' susceptibility to breast, lung, or prostate tumors might be associated with the UGT2B17 null genotype, which does not express protein UGT2B17 is a vital member of the UGT2 family and it is ubiquitously expressed in hepatic tissues as well as kidney, skin, lung, breast, uterine, and prostate. Studies have showed that UGT2B17 may contribute to the progress of chronic lymphatic leukemia and has an impact on antineoplastic drug metabolism in tumor cells UGT2B17 null genotype and risks for different types of tumor in diverse populations, such as prostate tumors UGT2B17 deletion polymorphism in the carcinogenic process, we executed a meta-analysis on all accessible case-control studies to estimate the overall tumor risk associated with the polymorphism and to measure the potential between-study heterogeneity.A number of studies have been done to elucidate the possible association between the UGT2B17 null genotype and tumor susceptibility, covering all the papers published through October 15th, 2013. Publications were identified using the following search terms: “Uridine diphosphoglucuronosyl transferases 2B17”, “UGT2B17 polymorphism”, “UGT2B17 deletion”, “tumor” or “carcinoma”. Additional literature was collected from a hand search from the references of original studies identified or review articles. No language restrictions were imposed. Only the latest or more comprehensive sample size was included if the studies had overlapping subjects. Studies chosen had to meet the following inclusion criteria: (1) a case-control design and (2) contain available genotype frequency. The major exclusion criterion was duplicates of previous publications.A comprehensive search of PubMed, EMBASE and Web of Science was conducted for relevant studies on the association between the Two reviewers independently extracted the data and reached a consensus on all items. The following information was obtained from each publication: author's first name, publication year, gender, tumor type, country of origin, ethnicity, number of cases and controls, source of control groups  and genotyping methods. The ethnic descents were classified as European, African, Asian and mixed. In four of the studies the data was presented as “Ins/Ins+ Ins/Del”, without the data for all three genotypes p<0.05 was regarded to have a significantly selective bias UGT2B17 null genotype and tumor risk. A significantly increased or reduced tumor risk was defined as having a 95% CI without one for OR. The fixed-effects and random-effects models are based on the Mantel-Haenszel method, and the DerSimonian and Laird methods were respectively utilized to pool the data P<0.001). First, the risks of the Del/Del and Ins/Del genotypes on tumors versus the wild-type Ins/Ins homozygote and (Ins/Del+ Del/Del) versus Ins/Ins from the data acquired was estimated. Next, the risks of the Del/Del versus (Ins/Ins+ Ins/Del) from all the pooled studies was estimated, assuming recessive effects of the UGT2B17 Del polymorphism. Stratified analyses were performed in accordance with sex, tumor type and ethnicity. Heterogeneity between the studies was calculated with the χ2-based Q test and P<0.05 was considered significant P<0.05 was considered significant P values.Hardy-Weinberg equilibrium (HWE) was evaluated using the goodness-of-fit chi-square test and a UGT2B17 deletion polymorphism and tumor risk, including 5,732 cases and 5,112 controls, . In a subgroup analysis on the source of control material, there was a significantly decreased risk in the hospital-based control group  using the recessive model. Nevertheless, the exclusion of two studies for their heterogeneity UGT2B17 null genotype and tumor risk   . In addity test)  (Table 3P<0.001). Meta-regression was utilized to evaluate the source of heterogeneity in the recessive model for gender  (P = 0.34), tumor type  (P = 0.66), material (blood or mixed) (P = 0.02), control source  (P = 0.43) and ethnicity  (P = 0.06). The results show that the material used for DNA extraction and the ethnicity did contribute to substantial altered heterogeneity. Next, a Galbraith radial plot was performed to delineate which study was the cause of the heterogeneity (P = 0.01). Again, the Galbraith radial plot was utilized to identify another heterogeneous study, the Park et al. study, based on a European population, contributed to the heterogeneity.Heterogeneity between studies was observed in the overall comparisons as well as in the subgroup analyses. There was significant heterogeneity in recessive genetic model .Begg's funnel plot and Egger's test were performed to assess the publication bias and the results are shown in UGT2B17 deletion polymorphism and tumors have attracted the attention in the research community. Park et al. UGT2B17 null polymorphisms may modify the risk of prostate tumor, particularly among those who have a family history of the disease. Interestingly, Carla et al. found significant differences in women but not in men, especially susceptibility for lung adenocarcinoma, which may be explained by its decreased rates of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butano (NNAL) glucuronidation in women. However, a study conducted by Gallagher et al. demonstrated that there was no association between the UGT2B17 deletion polymorphism and risk of prostate tumor in Caucasian men.It has been suggested that glucuronidation is a major detoxification pathway for compounds like bilirubin and steroid hormones, as well as xenobiotics, including alcohol, and environmental carcinogens. During tumorigenesis progression, UGT2B17 acts as a catalyzer to transfer glucuronic acid from UDPGA into endogenous and exogenous molecules. Altered expression of the UGT2B17 protein is mediated by its gene deletion polymorphism, and has been shown to be relevant to carcinogenesis. Correlations between the UGT2B17 deletion polymorphism and tumor risk remains conflicting and inconclusive. These conflicting findings may be a result of the small effect of the UGT2B17 deletion polymorphism on tumor risk, or the low statistical power in the published studies. Therefore, the meta-analysis presented herein, including 5,733 cases and 5,112 controls from 14 case-control studies, provides little evidence of an association between the UG2B17 deletion polymorphism and tumor risk. The findings of the meta-analysis are unclear; when all the studies in the analysis, a small but significant decrease of tumor risk were reported in the recessive model, but with great heterogeneity. The other three models did not show positive effects of tumor risk reduction. When stratified by the source of control material, meaningful results were only observed in the hospital-based controls with OR = 1.46, 95% = 1.06–2.01 and P = 0.11. Recent studies indicate that men exhibited a 4-fold higher UGT2B17 expression level than women, and these findings are indicate that this increase gene expression may play a greater role in reducing tumor risks in men than in women. By contrast, our analysis found out that this polymorphism did not have any gender-specific effects on tumor risks .In general, the results depicting the association between the UGT2B17 allele to those with UGT2B17 homozygous deletions UGT2B17 deletion polymorphism has tumor risk could not be revealed using the recessive model.Although, the results did report some possible links in tumors, the positive results were only slightly more significant than what would be found by chance. Several studies had merit and deserve individual mention. Owing to the limitations of the genotyping methods utilized in the early published studies, the heterozygous (Del/Ins) and homozygous (Ins/Ins) UGT2B17 genotypes could not be distinguished 2I values were used to demonstrate heterogeneity and great heterogeneity was observed with the recessive model (2I = 67.3%), which indicates that our meta-analysis may be inaccurate. The heterogeneity may emanate from various factors, such as population characteristic diversities, DNA extraction materials used and differences in controls. Tumor cells typically lose heterozygosity UGT2B17 null genotype and breast tumors material = P0.02) and Galbraith radial plots . Following exclusion of the breast tumor study UGT2B17 polymorphism may influence the susceptibility to non-tumor diseases, so its genotype frequency possibly differed between the hospital-based and population-based controls. Proper population-based control subjects may reduce the biases in the genetic association studies rather than the hospital controls which could be relatively easier and more economical to recruit. The results presented herein are more reliable when two studies were excluded for homogeneity UGT2B17 deletion polymorphism and tumor susceptibility .To sort out the possible causes of heterogeneity, the control selection procedures in the pooled studies were taken into consideration. The results show that the source of control will affect the meta-analysis UGT2B17 deletion polymorphism and the risk of tumor. Neither a total analysis, nor a stratified investigation, demonstrated a significant association with susceptibility to tumor; which means the UGT2B17 deletion polymorphism may have no role in tumor vulnerability. However, because of the relatively small sample sizes and the inadequate numbers of studies, the results need to be further validated and confirmed. Our analysis had other limitations.: First, our results were based on an unadjusted estimated, a more precise analysis would have been conducted if more detailed individual data were available which could have been adjusted for age or gender Second, only studies with full text from English databases were selected, and this may have led to publication. Third, the majority studies used were investigations in Europeans. However, our meta-analysis also had some merits. When two studies were excluded from the analysis, the homogeneity of pooled studies was maintained, which guaranteed reliability of our analysis. Additionally, no differences in tumor susceptibility between men and women have been discovered and it might be worth to note that sex hormones may contribute to the tumor in other ways.To the best of our knowledge this is the first meta-analysis that did a comprehensive assessment of the relationship between the UGT2B17 deletion polymorphism and tumor risk. Moreover, it would be interesting to extend the investigation to a wider range of human populations which may result in a better, comprehensive understanding of the association.This study reveals no significant association between the Checklist S1PRISMA 2009 checklist.(DOC)Click here for additional data file.


I2 statistics. All statistical tests were two-sided. Ten prospective studies were included with a total of 994,810 participants and 16,601 CVD events. A borderline significant inverse association was observed while comparing parity with nulliparous, with summarized RR = 0.79 . In dose-response analysis, we observed a significant nonlinear association between parity number and CVD mortality. The greatest risk reduction appeared when the parity number reached four. The findings of this meta-analysis suggests that ever parity is inversely related to CVD mortality. Furthermore, there is a statistically significant nonlinear inverse association between parity number and CVD mortality.Parity has been shown to inversely associate with cardiovascular disease (CVD) mortality, but the evidence of epidemiological studies is still controversial. Therefore, we quantitatively assessed the relationship between parity and CVD mortality by summarizing the evidence from prospective studies. We searched MEDLINE (PubMed), EMBASE and ISI Web of Science databases for relevant prospective studies of parity and CVD mortality through the end of March 2015. Fixed- or random-effects models were used to estimate summary relative risks (RRs) and 95% confidence intervals (CIs). Heterogeneity among studies was assessed using the  Cardiovascular disease (CVD) is one of the dominant causes of death and disability. It accounts for millions deaths worldwide each year and leads to be an important public issue1Pregnancy and parturition are important events in the life of a woman. Fluctuations of serum sex hormone levels during the process of pregnancy and delivery, perinatal hemodynamic changes, oxidative stress and other gestational factors exert complex influences on the cardiovascular system. Although previous studies have devoted great efforts to evaluate the relationship between childbearing history and mortality of CVD, the aforementioned association is still inconsistent. The association between parity and risk of CVD was first studied in the 1980s, which demonstrated the increased prevalence of CVD with parity number34567810111213141516171811151718The information of study quality is described in 13141316171213I2 = 90.9%; P < 0.001; P = 0.760) or Begg’s test (P = 0.260) (Six studies1114151718= 0.260) .I2 = 86.4%; P < 0.001; P < 0.001). There was evidence of a J-shaped association in the non-linear dose-response meta-analysis of parity number and CVD mortality. The association of parity number with CVD mortality appears to follow an inversely linear dose-response pattern until the parity number reaches four live births. After this point, the association appears to rebound  after omission of the study by Jacobs and colleaguesI2 = 0%; P = 0.957) after omission of the study by Jaffe and colleaguesI2 = 77.1%; P < 0.001) after omission of the study by Dior and colleaguesI2 = 80.0%; P < 0.001) after omission of the study by Jaffe and colleagues19In the sensitivity analysis, the six study-specific RR of the ever parity versus nulliparous women . Additionally, non-linear dose-response analysis displays a potential J-shaped relationship between parity number and CVD mortality. We firstly comprehensively and quantitatively evaluate the relationship between parity and CVD mortality.Findings from this meta-analysis demonstrate a borderline significant reduced risk of CVD mortality in ever parity Several potential mechanisms might have been proposed but the exact biologic mechanisms are not fully understood. Previous studies showed that complicated metabolic changes, such as dyslipidemia, abnormal glucose tolerance and increased body mass index, developed with increasing parity number20As for the associations between endogenous estrogen exposure and CVD mortality, however, former studies have reported conflicting results6et al.et al.19et al. suggested that women with more than 4 pregnancies were at lower CVD mortality risk13Compared to nulliparous, our meta-analysis shows that ever parity has a significantly protective effect against the death caused by CVD within a limited number of parity. Interestingly, as the 10 included cohorts displayed different viewpoints of parity and CVD mortality, the published information on this issue is scarce and inconsistent. Some studies reported a non-linear association between parity and CVD mortality10When we carried out the analysis of parity and CVD mortality by geographic location, significant positive association were observed in Israelite11151718Our meta-analysis has several strengths. The included studies showed conflicting results, which may result from their limited statistical range and power. Our study, however, was conducted based on approximately 994,810 study participants and 16,601 CVD cases from 10 cohort studies. This massive database generated a stronger statistical power for us to detect and verify this putative association. Moreover, prospective design also helped to make the present study more robust by eliminating selection bias and recall bias. At the same time, our approach with meta-analysis toward the studies was one of the powerful tools to assess the role of parity in the risk of CVD mortality. To guarantee the analysis quality, this meta-analysis had a big sample size, and the follow-up duration was considerably long. Although outcome evidence from long-term randomized trials is ideal, these studies are too difficult to implement on a practical basis, especially regarding reproductive factors.Meanwhile, several limitations should also be acknowledged. First, the discovered information toward the relationship between parity and mortality from subtypes of CVD and each diagnosis criteria was limited, which remained this topic open to further research in the field of observational cohort studies. Second, parity is associated with several other factors, such as gestational hypertension, gestational diabetes mellitus, gynecological tumor and so on, which are established risk factors for CVD. Third, higher deliveries was generally associated with unhealthy factors such as a higher possibility of abortion, oral contraceptive and so on. The observed association between moderate parity and a lower risk of CVD is unlikely to consider these confounders. Fourth, delivery mode was not taken into account in our study., natural labor and caesarean section might lead to different prognoses. Last, the quality of individual original studies varied. Quality scoring might ignore some important information or introduce somewhat arbitrary subjective factors into the analysis because of combining disparate study features into a single score. Although we used the Newcastle-Ottawa Scale (NOS)1314141518171213In conclusion, the present meta-analysis suggests a potential non-linear J-shaped relationship between the number of parity and CVD mortality. Since the number of included studies was limited, further studies are warranted to confirm our findings as well as to stratify the results by the types of CVD and other risk factors to eliminate the residual confounding.We applied the Meta-analysis Of Observational Studies in Epidemiology (MOOSE) as the guidance to conduct and report this studyThe literature was selected by 4 criteria: (1) the study had a prospective design; (2) the exposure was either parity or the number of livebirth; (3) the outcome was mortality from CVD, coronary heart diseases (CHD), or ischemic heart disease (IHD); and (4) risk estimates with 95% confidence intervals (CIs). If multiple literatures were based on the same population, we chose the literature with larger sample size. We identified 10 potentially relevant prospective studies101112131415161718101213Two independent investigators (Haichen Lv and Hongyi Wu) evaluated the eligibility and abstracted the data of each study. Discrepancies were settled by discussion. We summarized the following data from the selected studies: name of first author, year of publication, study’s country and design, sample size, follow-up year, exposure and outcome method, adjusted risk estimates and their 95%CIs of each included study for ever parity compared with nulliparous, and potential confounders adjusted for in the primary analysis. We also calculated the risk estimate from the raw data demonstrated in the literatureThe Newcastle-Ottawa Scale (NOS)et al.1011141516Considering heterogeneity between the studies, we used fixed-effectset al.et al.The methods described by Greenland I2 statisticsP values were two sided with a significance level of 0.05.In the studies, heterogeneity was assessed by using the How to cite this article: Lv, H. et al. Parity and Cardiovascular Disease Mortality: a Dose-Response Meta-Analysis of Cohort Studies. Sci. Rep.5, 13411; doi: 10.1038/srep13411 (2015).


OLR1 and PCSK9 genes are associated with atherosclerosis, cardiovascular disease and ischemic stroke. The overall prevalence of PCSK9 rs505151 and OLR1 rs11053646 variants in ischemic stroke were 0.005 and 0.116, respectively. However, to date, association between these polymorphisms and ischemic stroke remains inconclusive. Therefore, this first meta-analysis was carried out to clarify the presumed influence of these polymorphisms on ischemic stroke. All eligible case-control and cohort studies that met the search terms were retrieved in multiple databases. Demographic and genotyping data were extracted from each study, and the meta-analysis was performed using RevMan 5.3 and Metafor R 3.2.1. The pooled odd ratios (ORs) and 95% confidence intervals (CIs) were calculated using both fixed- and random-effect models. Seven case-control studies encompassing 1897 cases and 2119 controls were critically evaluated. Pooled results from the genetic models indicated that OLR1 rs11053646 dominant  and co-dominant models  were significantly associated with ischemic stroke. For the PCSK9 rs505151 polymorphism, the OR of co-dominant model  was found to be higher among ischemic stroke patients. In conclusion, the current meta-analysis highlighted that variant allele of OLR1 rs11053646 G > C and PCSK9 rs505151 A > G may contribute to the susceptibility risk of ischemic stroke.Both  Ischemic stroke is a heterogeneous group of neurovascular diseases and contributes to major morbidity and mortality in both developed and developing countries3OLR1) gene. This receptor protein mediates the recognition, internalization and degradation of ox-LDL. It is known that ox-LDL plays an important role during atherogenesis, by inducing vascular endothelial cell activation and dysfunction, results in pro-inflammatory responses, oxidative stress, necrosis and apoptosis3LOX-1 is one of the major scavenger receptor for oxidized low density lipoprotein (ox-LDL), which encoded by human oxidized low density lipoprotein receptor 1  in the OLR1 gene have been identified, including a c.501G > C transversion on exon 4, which results in an amino acidic substitution from lysine to asparagine at position 167 (p.K167N). This SNP was found to decrease binding and internalization of ox-LDL89111213The PCSK9 was formerly known as neural apoptosis-regulated convertase 1 and characterized as the ninth member of the subtilisin family of kexin-like proconvertases. PCSK9 plays an essential role in the proteolytic maturation of several secretory proteins such as neuropeptides, growth factors, cytokines and pro-hormones164PCSK9 gene is located on chromosome 1p32.3 and is 22-kb in length. It comprises of 12 exons and 11 introns, which encodes for 692 amino acids. Previous studies have investigated the relationship between PCSK9 SNPs and their changes in circulating LDL-C levels. A common SNP - 23968A > G (rs505151) in exon 12, results in an amino acid substitution from glutamate to glycine at position 670 (p.E670G), is potentially associated with the altered enzyme activity of PCSK92021The OLR1 rs11053646 and PCSK9 rs505151 polymorphisms and ischemic stroke. Therefore, we undertook the current meta-analysis from all eligible case-control studies and performed a critical review on these published articles, for the purpose of providing the highest level of evidence on their risk significance.Both OLR1 and PCSK9 are positively linked, where the inhibition of PCSK9 can suppress the development of atherosclerosis by disrupting LOX-1 expressionOLR1 rs11053646 and PCSK9 rs505151 polymorphisms, 84 and 176 studies were identified from the initial search  multiple studies from the same author (n = 1), (ii) insufficient information (n = 1), and (iii) study that reporting on polymorphism other than our interest (n = 1). No additional eligible article was found despite performing the extensive manual search on the references cited in the eligible publications and review articles. Therefore, a total of four (OLR1 rs11053646) and three articles (PCSK9 rs505151) encompassing 1138 and 759 cases as well as 1213 and 906 controls that met the inclusion criteria were included in the final meta-analysis model  1.33 . Interestingly, both of the co-dominant models for OLR1 rs11053646 and PCSK9 rs505151 demonstrated similar odds towards ischemic stroke . Although it is not statistically significant, the GG genotype carriers of PCSK9 rs505151 had a higher risk of ischemic stroke as compared to the wild-type carriers .Since heterogeneity has been observed in the overall comparison, random-effect models were applied for all of the forest plots , except t models . Ironicaic model . Neverthhet < 0.10 and I2 > 50%  and recessive (p = 0.37) models, except for the heterozygous model (p = 0.002).The significance of inter-study heterogeneity in the overall comparison models is summarized as PI2 > 50% . Meanwhie models  as well nt model . HoweverOLR1 rs11053646 and PCSK9 rs505151 polymorphisms with the risk of ischemic stroke. In this study, a total of seven eligible articles comprising 1897 stroke cases and 2119 healthy controls were included. The present meta-analysis covered all the publications indexed in the major databases such as PubMed, Scopus and Web of Science, as well as other databases from China, Hong Kong, India, Japan, Korea, Malaysia, Russia and Latin America. The positive association between the allelic variant of the studied genes and increased ischemic stroke risks represent the major findings of this meta-analysis. Present study has extended our previous knowledge on the participation of a large number of candidate genes in the development of ischemic stroke, particularly the genes involved in the coagulation, homocysteine and lipid signaling pathwaysTo the best of our knowledge, this is the first meta-analysis that comprehensively assessed the association between OLR1 in the pathogenesis of atherosclerosis and ischemic stroke has been investigated2526in vitro analysis has demonstrated that amino acids substitution of p.K167N (c.501G > C) may reduce the binding affinity of the OLR1 receptor and reduce the LOX-1 expression26OLR1 rs11053646 C allele is associated with ischemic stroke in the dominant model and/or in the recessive model. Consistent with this phenomenon, Liu and colleaguesp < 0.001; OR = 1.32, p = 0.04, respectively). Similarly, Zhang et al.p < 0.001) and CC genotype  were significantly higher among Chinese patients with ischemic stroke. However, other studies have shown a lack of association between this SNP and ischemic stroke11et al.p = 0.48; OR = 0.98, p = 0.91, respectively). Likewise, a relatively small number of studyp = 0.66 and p = 0.63). Hence, the presence of genetic heterogeneity and small sample size could possibly explain the divergent results of these studies.The clinical impact of PCSK9 in the risk of hypercholesterolemia and ischemic stroke2930PCSK9 gene can contribute to the variable expression and affect the enzyme activity of PCSK9. Nevertheless, the association between p.E670G and LDL-C still remains controversial. Some studies213233PCSK9 670 GG variant is associated with higher LDL-C levels and increased intima-media thickness progression, in the presence of ApoE4 allele3637PCSK9 rs505151 is associated with ischemic stroke, where the distribution of G allele is higher among ischemic stroke patients. Among the included studies, Abboud and colleaguesp = 0.047; OR = 2.01, p = 0.045 respectively). This observation is further supported by a Tunisian case-control study, where the incidence of G alleles  tends to be higher towards ischemic stroke riskIncreasing evidence has indicated the critical roles of OLR1 rs11053646 and PCSK9 rs505151. However, the non-significant P-value of Egger’s test (p > 0.05) indicated that the overall pooled results are unbiased, except for the OLR1 rs11053646 heterozygous model. Therefore, the results of this model shall be interpreted with caution. The observed heterogeneity may be attributed by the different ethnicities, sample size, study design, genotyping methods, and other environmental factors. Moreover, population heterogeneity may be derived from the genetic diversity of individual studies, i.e. genetic diversity may still exist even though the studied subjects are derived from the same population, ethnicity, country and district.A pertinent source of bias in the meta-analysis is that the source of selected study may be skewed due to the tendency of journals in selectively publishing studies with positive findings. Begg’s funnel plots demonstrated the existence of publication bias in different genetic models of PCSK9 rs505151 are limited for the subgroup analysis, since only a single Asian population was presented in this meta-analysis. Despite these limitations, our meta-analysis covered the most available association case-control studies, which involving both the hospital- and population-based. Furthermore, the present study has provided a better understanding on the association between the studied SNPs and the risk of ischemic stroke for the first time.However, there are several limitations in the current meta-analysis. For instance, we did not perform stratification analysis according to ischemic stroke subtypes since TOAST classification was not been reported in any of the eligible studies. In addition, the subgroup analysis has not been carried out in this meta-analysis. The population data of OLR1 rs11053646 and PCSK9 rs505151 may confer an increased risk of ischemic stroke. Therefore, these SNPs may be used as genetic biomarkers in relation to the burden of ischemic stroke, and serve as potential targets for diagnostic and therapeutic implications, and could thus have potential benefit for translational research in ischemic stroke. Further investigations with larger number of samples from more countries are needed, in order to facilitate the translation of genetic biomarkers into clinical practice.In conclusion, the current meta-analysis suggested that the variant alleles of LOX-1”, “OLR1”, “proprotein convertase subtilisin/kexin type 9”, “PCSK9”, “neural apoptosis-regulated convertase 1”, “NARC1”, “ischemic stroke”, “cerebrovascular disease”, “cerebrovascular accident”, “brain infarction”, “brain ischemia”, “cerebral ischemia”, polymorphism”, “variant”, “gene mutation”, “single nucleotide polymorphism (SNP)”, “gene variation” and the related Chinese characters were used as the criteria for searching. There was no limitation in language, where articles written in English, Japanese, Korean, Spanish, Russian or Chinese were retrieved. In addition, the time period for literature searching was from the first available article until July 2015.This meta-analysis followed the Cochrane Collaboration definition and PRISMA 2009 guidelines for meta-analysis and systematic review. We performed a comprehensive literature search throughout PubMed, Scopus, Web of Science, Google scholar, WHO Global Health Library, VHL, Jstage, KoreaMed, Korean Science Citation Index, POPLINE, New York Academy of Medicine Grey Literature Report, Indian Citation Index, System for Information on Grey Literature in Europe, IMSEAR, MJM, Mycite, WPRIM and CNKI to retrieve the genetic association studies of ischemic stroke. The medical subject heading and keywords terms “lectin-like oxidized LDL receptor-1”, “The inclusion criteria for the gene association studies in the final meta-analysis were as follows: (i) case-control and/or cohort studies; (ii) contained SNP genotype data; and (iii) adequate data for the calculation of odds ratios (ORs) and 95% confidence intervals (CIs).Data abstraction was performed independently by two authors (A.A. and L.K.W.). This meta-analysis was conducted when the data of three unduplicated studies are available. The following information from each study was summarized: (i) first author; (ii) publication year; (iii) province of study population; (iv) ethnicity; (v) number of cases and controls; (vi) mean age and sex ratio; and (vii) genotyping method.OLR1 rs11053646 and PCSK9 rs505151. The heterogeneity for all the included studies was evaluated using Cochran’s Q test and I2 statistics. The random-effects model was chosen when significant heterogeneous exist ; otherwise, fixed-effects model would be adopted. Potential publication bias was tested with Begg’s funnel plot and Egger’s regression test. The statistical tests were performed using the Review manager version 5.3 and Metafor package in R version 3.2.1p < 0.05 was considered statistically significant.The genotypic distributions for studied polymorphisms were compared against the controls for any possible deviations from the Hardy-Weinberg equilibrium. Crude OR and 95% confident interval (CIs) were calculated to test the strength of associations between studied polymorphisms and ischemic stroke. The significance of the pooled ORs was determined by Z test for polymorphisms under different genetic models  for How to cite this article: Au, A. et al. The Influence of OLR1 and PCSK9 Gene Polymorphisms on Ischemic Stroke: Evidence from a Meta-Analysis. Sci. Rep.5, 18224; doi: 10.1038/srep18224 (2015).