Background: Proprotein convertase subtilisin/kexin type 9 (PCSK9), a pivotal protein in low-density lipoprotein cholesterol metabolism, has been validated to be an established target for cardiovascular (CV) risk reduction. Nevertheless, prospective studies concerning the associations between circulating PCSK9 and the risk of CV events and mortality have yielded, so far, inconsistent results. Herein, we conducted a meta-analysis to evaluate the association systemically.Methods: Pertinent studies were identified from PubMed, EMBASE, and Cochrane Library database through July 2020. Longitudinal studies investigating the value of circulating PCSK9 for predicting major adverse cardiovascular events (MACEs) or stroke or all-cause mortally with risk estimates and 95% confidence intervals (CI) were included in the analyses. Dose-response meta-analysis was also applied to evaluate circulating PCSK9 and risk of MACEs in this study.Results: A total of 22 eligible cohorts comprising 28,319 participants from 20 eligible articles were finally included in the study. The pooled relative risk (RR) of MACEs for one standard deviation increase in baseline PCSK9 was 1.120 . When categorizing subjects into tertiles, the pooled RR for the highest tertile of baseline PCSK9 was 1.252  compared with the lowest category. This positive association between PCSK9 level and risk of MACEs persisted in sensitivity and most of the subgroup analyses. Twelve studies were included in dose-response meta-analysis, and a linear association between PCSK9 concentration and risk of MACEs was observed . No significant correlation was found either on stroke or all-cause mortality.Conclusion: This meta-analysis added further evidence that high circulating PCSK9 concentration significantly associated with increased risk of MACEs, and a linear dose-response association was observed. However, available data did not suggest significant association either on stroke or all-cause mortality. Additional well-designed studies are warranted to further investigate the correlations between PCSK9 concentration and stroke and mortality. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a circulating serine protease, has a fundamental role in low-density lipoprotein cholesterol (LDL-C) metabolism by enhancing the endosomal and lysosomal degradation of hepatic LDL-Receptor, thereby resulting in increased LDL-C concentration.Over the past years, PCSK9 has been validated to be an established target for cholesterol-lowering therapies. Three randomized, double-blind, placebo-controlled cardiovascular (CV) outcome trials were completed and demonstrated that PCSK9 monoclonal antibodies significantly reduce plasma LDL-C level and major vascular events in subjects with high CV risk –3. The pCirculating concentration of PCSK9 has attracted scientific interest as a biomarker for CV risk stratification. In recent years, mounting studies have explored the association between circulating PCSK9 and the risk of CV events; however, the results remained divergent. Werner et al. reported that elevated PCSK9 serum concentrations are correlated with CV events in patients with stable coronary artery disease . NeverthIn accordance with recommendations of the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group , we searStudies were deemed eligible if they: (1) included participants of any age across different countries; (2) had PCSK9 levels in plasma or serum at baseline as exposure of interest; (3) had clinical outcomes including MACEs and/or stroke and/or all-cause mortality; (4) were prospective cohort studies or nested case-control studies performed within prospective cohort with a minimum follow-up of 1 year; (5)were full-text publications; (6) had a multivariable-adjusted relative risk (RR) or hazard ratio (HR) or odds ratio (OR) and the corresponding 95% confidence interval (CI) or provision of available information to calculate them. MACEs were defined as composite outcomes, including fatal and non-fatal coronary artery disease (CAD), fatal and non-fatal stroke, and heart failure. In order to better evaluate the causality between PCSK9 concentration and the clinical outcomes, we included only prospective cohort studies or prospective nested case-control studies.Two reviewers (YZ and WC) independently searched, selected studies and extracted data. The disagreement between the two reviewers was resolved by consensus. The following data were extracted from each study: the last name of the first author, year of publication, country of study, type and amount of participants, study type, the proportion of men, mean age, duration of follow-up, number of outcome events, CV risk status, the measurement method of PCSK9, mean or median concentration of PCSK9, sample source, adjusted confounding factors, statin use, the history of family hypercholesterolemia (FH), and the most fully adjusted HRs or RRs or ORs with 95% CIs of circulating PCSK9.Using the Newcastle-Ottawa Scale (NOS), the quality of the included studies was assessed . Each stThe risk estimates of the association between PCSK9 and the outcomes of interest in each study were reported as a HR, RR, or OR with 95% CI. Risk estimates adjusted for the maximum number of covariates were pooled across studies for inclusion in the meta-analyses. In this meta-analysis, all associations were estimated as RRs and 95% CIs. HRs were approximately considered as RRs, which have been commonly used in previous studies . ORs werQ statistic  and the I2 statistic   or fixed effects model  as appropriate. To test the robustness of the pooled results, sensitivity analyses were conducted by leave-one-out method in each turn to investigate the influence of every single study on the overall risk estimate  . We poolestimate , and by To assess the potential sources of heterogeneity, subgroup analyses which sorted by published year, mean age at baseline, sample size, CV risk, percentage of the history of FH, sample source, percentage of statin use, PCSK9 level at baseline, the assays for PCSK9 measurement, and degree of adjustment were performed. High CV risk cohort referred to participants in the studies with established CVD or known CVD risk factors  and low CV risk cohort to apparently healthy participants at baseline. Mean/median level of PCSK9 at baseline for included studies were extracted, and 258 ng/mL, the median for the 21 cohorts, was used as the cut-off point. A univariate meta-regression with restricted maximum likelihood was performed to measure if pooled RR significantly differed between each stratum analyzed.P for non-linearity was calculated to detect potential departure from a linear trend by testing the coefficient of the second spline equal to zero. In the presence of substantial linear trends (Pnon−linearity > 0.05), a linear model was conducted to achieve the association between circulating PCSK9 and the risk of MACEs by using the method of two-stage GLST  or linear association between circulating PCSK9 and risk of MACEs. We used the two-stage generalized least-squares trend (GLST) estimation method proposed by Greenland and Longnecker to estimate the study-specific slope lines first and then derive an overall average slope , 19. ThiP < 0.05 was considered statistically significant, except where otherwise specified.The possibility of publication bias of the outcome of MACEs was assessed graphically by funnel plots and quantitatively by Begg's rank correlation test and Egger's linear regression test , 21. WheOur initial search returned 1,245 articles. After we screened titles and abstracts, 29 articles were qualified for full-text evaluation. After full-text review, nine studies were excluded, and 22 eligible cohorts from 20 eligible articles were finally included for meta-analysis –9, 23–39P < 0.001), with moderate heterogeneity across studies .As shown in P < 0.001) than those with a low percentage ; the heterogeneity was also reduced, indicating that the source of heterogeneity appeared to be contributed by the medical history of FH. High baseline PCSK9 level was only significantly associated with increased MACEs in studies with a higher degree of cofounder adjustment  but not in those with a lower degree .Considering the aforementioned moderate heterogeneity between the included studies, we further conducted subgroup analyses based on potential clinical relevance . The posP < 0.001; I2 = 66.90%; Pheterogeneity < 0.001).For sensitivity analysis, exclusion of any single study did not immensely alter the combined risk estimate . After eI2 = 63.10%; Pheterogeneity < 0.001).Considering the fact that most of the included articles reported circulating PCSK9 as tertiles, we also compared individuals within the top tertile with the bottom tertile of circulating PCSK9 levels at baseline. Overall, there was a significant association between the highest PCSK9 tertile and the risk of MACEs  , with moSubgroup and sensitivity analyses for category PCSK9 achieved similar results to the analyses mentioned above for PSCK9 per 1-SD increase ; Yet, whAmong the 19 articles concerning PCSK9 and MACEs, seven articles were excluded because of lack of cases or cohort size or the risk estimate of each category, and 12 articles were finally involved in the dose-response meta-analysis , 35, 38.I2 = 57.6%, Pheterogeneity = 0.095) and for the highest tertile vs. the lowest tertile .In total, only two studies , 28, incI2 = 12.60%, Pheterogeneity = 0.334)   . For sub= 0.222) .P = 0.020, 0.016, respectively).The funnel plot for the correlation between PCSK9 and MACEs showed asymmetry  at its bottom , which wWhereas, the contour-enhanced funnel plot with four filled studies estimated from the trim-and-fill method plotted  demonstrOur study is an updated meta-analysis investigating the predictive role of circulating PCSK9 with clinical outcomes. In the present meta-analysis, 20 published articles, namely, 19 studies on MACEs, three studies on stroke, and six studies on all-cause mortality, involving a total of 28,319 participants were included. The result indicated that the PCSK9 level is an independent predictive marker for MACEs with a 25% increased risk while compared with the lowest tertile, and per unit of SD change in baseline PCSK9 corresponds to an increase of 12%. A dose-response meta-analysis between circulating PCSK9 concentration and MACEs risk was conducted further, and a linear dose-response relationship was observed. However, a significant association either with stroke or all-cause mortality was not suggested in the study.Since substantial heterogeneity was observed across studies for MACEs, subgroup and meta-regression analysis were employed to get more reliable pooled risk estimates. Despite consistent results found in most of the subgroup analyses, heterogeneity could be partially explained by the percentage of FH history in the study .via other mechanisms . The reduced heterogeneity might also indicate the heterogeneous nature of FH population, as reported in previous studies that the predictive value of some traditional risk factors for future MACEs was different from the general population  among different ELISA techniques . StudiesIn our view, the current meta-analysis has several strengths. First, it is the most comprehensive meta-analysis on this topic to date with a relatively large number of cases and participants. Finally, the risk estimates from the fully adjusted models for each study were applied in our analyses to reduce the potential of confounding. Despite these strengths, limitations of this meta-analysis should be noted. Firstly, the pooled result of PCSK9 and MACEs showed substantial heterogeneity among the included studies, which may affect the interpretation of the results. Although we conducted on stratified and sensitivity analyses to identify the sources of heterogeneity, the heterogeneity could not be fully explained. Furthermore, meta-regression techniques are limited used in the present analysis given the lack of information for many continuous factors, such as baseline LDL, high-sensitivity C-reactive protein, and the result should therefore be viewed with caution. Secondly, original studies included in the study reported the risk estimates calculated by different multivariable models, and the pooled association lost significance in the subgroup with a lower degree of confounder adjustment. On these grounds, the combined result might potentially be influenced. Thirdly, most of the included studies used the combined CV events as the outcome of interest, making it difficult to identify the risk of specific CV events including stroke and different stroke subtypes; the statistical power might be compromised, and therefore, advanced studies focusing specific CV outcomes are warranted in future research. Finally, statistical tests for detecting publication bias in pooling the effect estimates of PCSK9 and all-cause mortality and stroke may be potentially unreliable due to less than the recommended minimum number of 10 studies analyzed .This meta-analysis provided further evidence that high circulating PCSK9 concentration is associated with increased risk of MACEs with a linear dose-response relationship. However, available data did not suggest a significant correlation either on stroke or all-cause mortality. Our finding suggested that measurement of PCSK9 level may have the potential to improve risk stratification for medical decision and also support the result of the beneficial clinical role of PCSK9 inhibitors. To further investigate the correlations between PCSK9 concentration and stroke and mortality, additional well-designed multicenter studies with standardized methodologies are warranted.The original contributions presented in the study are included in the article/YZ had the idea for the study, did the statistical analysis with guidance from ML and WC, and drafted the manuscript. YZ and YW contributed to the study designed. YZ and WC participated in the search, data collection, and extraction. ML and WC did the major revision. All authors read and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Genetic association of uncoupling proteins (UCPs) variants with the susceptibility of diabetic retinopathy (DR) in diabetes mellitus (DM) patients has been reported but with controversy. Here we aimed to conduct a meta-analysis to confirm the association of different UCPs variants with DR.Three databases  were applied in the literature search. Five genetic models, including allelic, homozygous, heterozygous, dominant and recessive models, were evaluated. Odds ratios (OR) were estimated under the random or fixed-effects models. Subgroup analyses, publication bias and sensitivity analyses were also conducted.UCP1 rs1800592 and UCP2 rs659366) were included. Our meta-analysis showed that UCP1 rs1800592 was not associated with DR in type-2 DM patients, and UCP2 rs659366 also showed no association with DR. In the subgroup analyses on the stage of DR, allele G of UCP1 rs1800592 significantly increased the susceptibility of proliferative diabetic retinopathy (PDR) in type-2 DM patients in the allelic  and homozygous models . Subgroup analysis on ethnicity did not found any significant association of rs1800592 and rs659366 with DR.Eleven studies on 2 UCPs variants (UCP1 rs1800592 variant with PDR in patients with type-2 DM, suggesting its potential as a genetic marker for PDR prediction in population screening.Our meta-analysis confirmed the association of The online version contains supplementary material available at 10.1186/s12886-021-01838-1. Diabetic retinopathy (DR), a common sight-threatening microvascular complication among patients with diabetes mellitus (DM), is the major cause of irreversible blindness and visual impairment in working-age adults . Though +) in the inner membrane of mitochondria  is associated with the decreased UCP2 gene expression in human retina [UCP2 variants with DR in different ethnic groups.UCP2 is the most widely distributed uncoupling protein and most frequently studied in DM and DR, and itis associated with the increased oxidative stress and negatively regulates the insulin secretion , 44. Tote effect . The neg variant . One repn retina . This con retina . AdditioWe conducted the subgroup analyses on ethnicity in this meta-analysis. There was no significant association in different ethnic group, which could be due to the limited and sample sizes after stratification. Thus, the ethnicity-specific effects of these variants need to be determined with larger sample sizes in additional cohort studies.There are several limitations in this meta-analysis. First, the number of reported studies for each UCPs variant was still limited. Second, the lack of original clinical information would be difficult to adjust the relevant variables, such as duration of diabetes, medications and other chronic diseases.UCP1 rs1800592 and UCP2 rs659366 with DR in DM patients; yet allele G of UCP1 rs1800592 variant could be associated with the increased risk of PDR in type-2 DM patients. Our results suggest that UCP1 rs1800592 variant could be clinically applied as a genetic marker for PDR prediction and risk analysis in DM clinics.In summary, our meta-analysis revealed no significant pooled association of Additional file 1.Additional file 2.Additional file 3.Additional file 4: Table S1. Characteristics of other UCPs variants. Table S2. Analysis of the included studies by Newcastle-Ottawa quality assessment scale. Figure S1. Subgroup analysis of UCP1 rs1800592 by ethnicity. Figure S2. Subgroup analysis of UCP2 rs659366 by ethnicity. Figure S3. Subgroup analysis of UCP2 rs659366 by stage of DR. Figure S4. Sensitivity analyses of UCP1 rs1800592 in all genetic models. Figure S5. Sensitivity analyses of UCP2 rs659366 in all genetic models


Future studies should be designed to include standardized data collection and matching for important confounding factors such as body mass index, age, and race.(1) Background: Studies on the association between Vitamin D receptor gene polymorphism and gestational diabetes mellitus have been inconsistent. The aim of this study was to summarize available evidence on the association between polymorphisms of Vitamin D receptor genes and susceptibility to gestational diabetes mellitus. (2) Methods: We searched databases of PubMed, Web of Science, Embase, China national knowledge infrastructure (CNKI), China science and technology journal database (VIP), and Wanfang Data for relevant articles. A systematic review and a meta-analysis were done to compare the distribution of Vitamin D receptor gene polymorphisms in gestational diabetes mellitus patients with those in controls using allelic, codominant, dominant, and recessive models. (3) Results: A total of eight eligible articles were included in the systematic review and of them, six articles were included in the meta-analysis. The vitamin D receptor gene rs7975232 polymorphism was associated with gestational diabetes mellitus under the allelic model , codominant model , and recessive model  in the case of low heterogeneity. High heterogeneity existed in studies on the association of vitamin D receptor genes  Gestational diabetes mellitus (GDM), a pregnancy complication, is defined as any degree of glucose intolerance that first develops or is first diagnosed during pregnancy . The repThe incidence of GDM has been increasing. However, the biomolecular mechanisms of GDM are not clearly understood ,11. It iGenetic variants in the VDR gene are potential candidates for investigation to better understand how vitamin D pathways are involved in the pathogenesis of GDM. Results from studies on the relationship between VDR gene polymorphisms and GDM are inconsistent. The aim of this review was to summarize the available evidence on the association between VDR gene polymorphisms and GDM.This systematic review/meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines . A systeStudies were included in this systematic review if they met the following criteria: (1) observational study or experimental study which was conducted in pregnant women; (2) the study investigated the association between VDR gene polymorphism and GDM; (3) diagnoses for GDM were reported; (4) sample size was reported in article; (5) full article was written in English or Chinese. Exclusion criteria were as follows: (1) lack of information on specific SNPs of VDR gene; (2) no available information on distribution of VDR gene polymorphism in case and control; (3) abstracts, case reports, comments, conferences, reviews, academic dissertations, and book chapters; (4) case and control were not pregnant women with GDM and without GDM. When data from the same population were published several times, the first published paper was included.Endnote was used to manage articles and two investigators (Q.Z. and X.J.) assessed articles and extracted relevant data from eligible articles independently. Articles that met the inclusion requirements after screening for titles and abstracts were selected for full-text review. The following data were extracted from the eligible original studies: the last name of the first author, year of publication, diagnostic criteria, country of study, study design, the method used to evaluate VDR gene polymorphisms, sample size, age of study participants, matching, the result of Hardy–Weinberg equilibrium (HWE) in the control group, number of participants for each genotype, and the SNP code of the VDR gene that was studied.2) as the most important factor when assessing the comparability of cases and controls for this meta-analysis, because it has been reported in a number of studies that BMI is significantly associated with GDM [The NEWCASTLE-OTTAWA QUALITY ASSESSMENT SCALE was used to assess the quality of included studies . In addiwith GDM ,24. Two 2I statistic were used to evaluate the heterogeneity across studies, with 2I ≥ 25%, 2I ≥ 50%, and 2I ≥ 75%, respectively, indicating low, moderate, and high heterogeneity. The summary ORs were calculated using the Mantel–Haenszel method with a random-effects model if the heterogeneity observed across studies was significant (p ≤ 0.10 and/or 2I > 50%). Otherwise, a fixed-effects model was used. HWE was assessed by Pearson’s chi-squared test using the “meta” package of software R version 3.5.1. If the included article did not report the HWE in the control group, it was considered as in HWE if p > 0.05.Statistical analyses were performed using the “meta” package of software R (version 3.5.1)  Summary odds ratios (ORs) with their 95% confidence intervals (Cis) in the allelic genetic model, codominant genetic model, dominant genetic model, and recessive genetic model were calculated to assess the strength of association between VDR gene polymorphisms and the susceptibility to GDM. Cochran’s χ2 test and the 2I ≥ 50%). Subgroup analysis was carried out according to the following features of the included studies: year of publication (before 2019 versus 2019), study design , diagnostic criteria  versus American Diabetes Association (ADA), and matching (yes versus no).Because the number of included studies was less than 10, no formal assessment of publication bias was performed. Subgroup analysis and sensitivity analysis were conducted when heterogeneity was moderate or high , codominant model , and recessive model  in the case of low heterogeneity. rs1544410, rs2228570, and rs731236 with GDM.rs739837, rs11574143, and rs10735810 with GDM. However, these SNPs were not reported in other eligible studies. As a result, these two studies were not included in meta-analysis. These two articles reported no significant difference in VDR genes rs739837, rs11574143, and rs10735810 between cases and controls.Two eligible studies examined the association of VDR genes rs1544410, rs2228570 and rs731236. Study design and the diagnostic criteria were the main sources of heterogeneity of VDR genes rs2228570, rs731236. The results of sensitivity analysis are shown as forest maps in rs1544410, the results fluctuated greatly after omitting El-Beshbishy 2015 [rs731236, the results fluctuated greatly after omitting Rahmannezhad 2016 [The summarized sources of heterogeneity are displayed in shy 2015  and for had 2016  or Zhu 2had 2016 .rs7975232 polymorphism was correlated with GDM under several genetic models, while VDR gene rs1544410, rs2228570, and rs731236 polymorphisms were uncorrelated with GDM. The results should be interpreted with caution, however, because the sample size was not large enough, and there was high heterogeneity among studies on VDR gene polymorphisms rs1544410, rs2228570, and rs731236. Although six studies were included in the meta-analysis, the number of studies for each SNP was less than that, so the sample size for each specific VDR gene polymorphism was limited. Our subgroup analysis found that year of publication was one of the most common sources of heterogeneity among studies on VDR gene polymorphisms rs1544410, rs2228570, and rs731236. It should be noted that all eligible studies were published after 2012 and three of them were published in 2019, indicating that this field of research may be still in its infancy. Another meta-analysis published recently about the association between GDM and seven gene polymorphisms reported that the VDR FokI rs2228570 polymorphism was significantly associated with susceptibility to GDM [rs2228570 and rs10735810 polymorphisms of the VDR gene in the meta-analysis, which probably have the same restriction enzyme FokI.It has been hypothesized that deficiency of vitamin D may be a risk factor for GDM, but findings in previous studies on this topic remain inconsistent ,34,35,36y to GDM . This isrs7975232 was the most likely to be associated with GDM, but only three studies have examined the gene polymorphism of rs7975232, with a total of only 417 cases and 436 controls. Therefore, future studies should focus on the VDR gene rs7975232. Second, although the associations of VDR genes rs1544410, rs2228570, and rs731236 with GDM were not significant overall, subgroup analysis indicated that matching and year of publication were the most common sources of heterogeneity, suggesting that the quality of study has been improving in recent years and that future studies should try to control confounding by matching important factors such as BMI, age, and race. Third, important information such as SNPs of the VDR gene [Currently, there are no effective measures to prevent GDM. However, the relationship between VDR gene polymorphism and gestational diabetes susceptibility may provide new ideas for the prevention of gestational diabetes in the future. Populations susceptible to GDM during pregnancy could be found by genotyping of VDR, so as to provide targeted vitamin D supplementation recommendations. Although no definitive conclusion regarding the association between VDR gene polymorphism and GDM could be drawn from this systematic review and meta-analysis, important information for future research directions could be obtained from this exercise. First, the VDR gene VDR gene ,41 or diVDR gene ,43 was nOur study had several limitations. First, we searched for publications in English and Chinese only, and would have missed articles in other languages or gray literature. Second, the heterogeneity of the subgroup analysis was high, indicating that interpretation of the results of this study should be treated with caution. Third, race is a very important factor during polymorphism analysis. However, as not all included studies reported the race of the study population, the lack of data made it impossible to conduct subgroup analysis using race as a grouping factor.rs7975232 polymorphism of the VDR gene may be associated with GDM. Future studies should use standardized data collection and matching for important confounding factors such as BMI, age, and race.This systematic review suggests that the


In conclusion, our data suggest that tobacco smoking during pregnancy increases the risk of moderate/severe BPD. Our results highlight the detrimental effects of tobacco smoking and reinforce the hypothesis of the involvement of prenatal insults in the etiopathogenesis of BPD.Epidemiological evidence and animal studies support that intrauterine exposure to tobacco smoke disturbs lung development and has a negative effect in the pulmonary health of the offspring. Individual studies suggest an association between fetal exposure to maternal smoking and risk of developing bronchopulmonary dysplasia (BPD). However, this association has not yet been systematically investigated. We aimed to conduct a systematic review of studies reporting on tobacco smoking during pregnancy as potential risk factor for BPD. PubMed/MEDLINE and EMBASE databases were searched. BPD was defined as requirement of supplemental oxygen on postnatal day 28 , at the postmenstrual age (PMA) of 36 weeks , or as requirement of more than 30% oxygen and/or positive pressure at 36 weeks PMA (severe BPD). Pooled risk ratios (RR) and 95% confidence intervals (CI) were calculated using a random-effects model. Of 2,894 potentially relevant studies, 33 met the inclusion criteria. The included studies evaluated 171,772 infants and included 30,445 cases of exposure to maternal smoking and 25,340 cases of BPD of any severity. Meta-analysis showed a significant association between tobacco smoking during pregnancy and BPD36 (17 studies, RR 1.126, 95% CI 1.008–1.259,  Bronchopulmonary dysplasia (BPD), the chronic lung disease of prematurity, is the most common complication of very and extreme preterm birth –6. In adTobacco smoking during pregnancy is associated with a range of detrimental effects in offspring, including stillbirth, congenital anomalies, intrauterine growth restriction, preterm birth, and neonatal mortality –14. EpidWe followed the same methodology that was used in our previous meta-analysis on the association between chorioamnionitis and BPD . The PopA comprehensive literature search was undertaken using the PubMed/MEDLINE and EMBASE databases from their inception to March 1, 2019. The search terms involved various combinations of the following keywords: “maternal smoking,” “bronchopulmonary dysplasia,” “chronic lung disease,” “preterm birth,” “prematurity,” “low birth weight,” “very low birth weight,” “observational study,” “cohort study,” “case-control,” and “risk factors.” Search strategy is detailed in Two investigators (MJH and EV) independently evaluated studies for inclusion and any disagreements were resolved by discussion. Studies were included for analysis if satisfying all following criteria: (1) full text available in English, German, Dutch, Spanish, French, Italian, Portuguese, or Catalan; (2) with a prospective or retrospective cohort study or case-control design; (3) assessing BPD  as outcome of infants exposed to tobacco smoking during pregnancy (self-reported or assessed through laboratory tests), or assessing the risk factors for BPD, when tobacco smoking during pregnancy was one of the investigated risk factors; and (4) in a study population of newborn infants with a gestational age below 34 weeks or birth weight below 1,500 g. Studies not complying with the above-mentioned criteria were excluded. We did not set an a priori minimum sample size of the studies to be included.Two investigators (GG-L and EW-K) independently extracted data, and two reviewers (EV-M and EV) checked the data extraction for completeness and accuracy. Data extracted from each study included citation information, language of publication, location where research was conducted, time period of the study, study objectives, study design, definitions of maternal smoking and BPD, inclusion/exclusion criteria, patient characteristics, and results . Criteria for classification of BPD were similar to those used in our previous meta-analysis : “BPD deMethodological quality was assessed using the Newcastle-Ottawa Scale (NOS) for cohort studies . This sccomprehensive meta-analysis V3.0 software . The Mantel-Haenszel risk ratio (RR) with 95% confidence interval (CI) was calculated from the raw data provided in the studies. When raw data were not available, published RRs, or odds ratios (ORs) were extracted. ORs were converted to risk ratios following the method of Zhang et al. , moderate (50% ≤ I2 < 75%), and high (I2 ≥ 75%). Sources of heterogeneity were explored through subgroup analyses and random effects (method of moments) meta-regression analyses  (p = 0.036) (p = 0.734). Neither visual inspection of funnel plots  suggested publication or selection bias. There were insufficient studies with the definition of severe BPD to evaluate publication bias.Sixteen studies reported data on BPD28 , 25–39 a= 0.681) . In cont= 0.681) –53 showe= 0.036) . Accordi= 0.036) . Only th= 0.036) , 39, 40.el plots  nor EggeNeither subgroup-analysis  nor metaTo the best of our knowledge, this is the first systematic review and meta-analysis investigating the relationship between maternal smoking in pregnancy and BPD. Meta-analysis demonstrated a significant association between exposure to maternal smoking during pregnancy and risk of developing moderate/severe BPD (BPD36). In contrast, meta-analysis could not demonstrate a significant association between maternal smoking and all BPD (BPD28) or severe BPD. Our analysis is limited by the relative low number of studies and by the heterogeneity across studies. Studies on exposure to maternal smoking during pregnancy are by definition observational and, consequently, susceptible to confounding by unmeasured differences between the exposed and unexposed populations . In addiBias relating to exposure assessment is a major source of systematic error in studies of environmental exposures . Self-reAs discussed elsewhere , 61, metThat prenatal exposure to tobacco smoke increases the risk of BPD is a biologically plausible hypothesis. There is strong evidence from animal studies on the adverse impact of antenatal smoke exposure on lung development , 11. TheRisk of BPD is inversely correlated with GA and maternal smoking is a well-known risk factor for preterm birth. Therefore, an important part of the role of maternal smoking on the pathogenesis of BPD would be related to its role as a trigger for preterm birth. The etiopathogenesis of very (GA 28–32 weeks) and extremely (GA <28 weeks) preterm birth has been divided into two main categories: intrauterine infection/inflammation and placental vascular dysfunction. The first category includes pathological conditions such as chorioamnionitis, preterm labor, premature rupture of membranes, placental abruption, and cervical insufficiency. The second category is associated with gestational hypertensive disorders and the entity identified as fetal indication/fetal growth restriction –70. SmokExposure to tobacco smoke is associated with respiratory complications beyond BPD and the detrimental effects of smoking during pregnancy may also cumulate with smoking during lactation and with second-hand smoking exposure at home , 79. MatIn summary, the present meta-analysis confirmed the findings of previous individual studies on the association between maternal smoking during pregnancy and risk of BPD. Therefore, our results highlight the detrimental effects of tobacco smoking and reinforce the hypothesis of the involvement of prenatal insults in the etiopathogenesis of BPD. As assessed by Been and Millet, “children have the right to grow up in a smoke-free world” . Smoke-fThe datasets generated and analyzed for this study will be made available by the authors, without undue reservation, to any qualified researcher.GG-L carried out the search and selected studies for inclusion, carried out data collection, carried out statistical analyses, assessed methodological quality, contributed to interpretation of results, helped draft the initial manuscript, and reviewed and revised the manuscript. EW-K carried out and supervised data collection, contributed to statistical analyses an interpretation of results, and reviewed and revised the manuscript. EV-M contributed to data collection, contributed to statistical analyses an interpretation of results, and reviewed and revised the manuscript. MH contributed to the search and inclusion of studies, contributed to interpretation of results, and reviewed and revised the manuscript. MK contributed to data collection, contributed to interpretation of results, and reviewed and revised the manuscript. BK contributed to interpretation of results and reviewed and revised the manuscript. EV conceptualized and designed the study, carried out the search and selected studies for inclusion, supervised data collection, assessed methodological quality, contributed to statistical analyses and interpretation of results, drafted the initial manuscript, and reviewed and revised the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


PPARG2 Pro12Ala; rs1801282) has been linked to both cancer risk and dietary factors. We conducted the first systematic literature review of studies published before December 2020 using the PubMed database to summarize the current evidence on whether dietary factors for cancer may differ by individuals carrying C (common) and/or G (minor) alleles of the PPARG2 Pro12Ala allele polymorphism. The inclusion criteria were observational studies that investigated the association between food or nutrient consumption and risk of incident cancer stratified by PPARG2 Pro12Ala allele polymorphism. From 3815 identified abstracts, nine articles  covering three cancer sites  were included. CG/GG allele carriers were more impacted by dietary factors than CC allele carriers. High levels of protective factors  were associated with a lower cancer risk, and high levels of risk factors  were associated with a higher cancer risk. In contrast, both CG/GG and CC allele carriers were similarly impacted by dietary fats, well-known PPAR-γ agonists. These findings highlight the complex relation between PPARG2 Pro12Ala allele polymorphism, dietary factors, and cancer risk, which warrant further investigation.Peroxisome proliferator-activated receptor-γ2 gene Pro12Ala allele polymorphism ( PPARG1, PPARG2, and PPARG3, with PPARG2 being the longest and most bioactive ) interaction in relation to incident cancer risk. Titles and abstracts, and/or full texts were excluded if they meet one of the following criteria: (1) Review, letter, editorial, commentary, or case reports; (2) in vitro, functional, or animal studies; (3) study not about PPAR polymorphism and incident cancer risk; (4) only abstract available; (5) no diet-gene interactions reported; or (6) overlap of the study population in another eligible original study or duplicated with individual studies in eligible meta-analysis.The eligible studies needed to meet the following criteria: Human studies, written in English, and reporting the diet-gene , relative risk, or incidence rate ratio (IRR), and 95% confidence interval (CI); and the statistical significance of the interactions. Two authors (L.T. and Y.T.) extracted data from each study independently, and inconsistencies were discussed and brought to consensus.Data were extracted from each included study. Specific data extracted are: Last name of the first author; year of publication; study design; sample size ; study population characteristics ; study location; cancer site; The risk of bias for each study was assessed by two authors (L.T. and Y.T.) independently using Newcastle–Ottawa scale for case-control and cohort studies ; any disThe eight studies included in our systematic review were conducted in a wide variety of countries; two were carried out in Denmark, and each of the other studies were conducted in the United States, Finland, Spain, India, Korea and Japan . In termPPARG2 Pro12Ala modified the association between alcohol intake and cancer risk  Alcohol intake and breast or colorectal cancer risk; and (2) diet and colorectal cancer risk.Through our systematic literature review, we identified eight case-control studies  covering three continents  and three cancer sites  that examined the association between dietary factors and cancer risk among participants who differ in PPARG2 Pro12Ala polymorphism generally play a more important role in the etiology of colorectal cancer than other cancer sites [Dietary factors and er sites ,33,34,35er sites ,37,38. Ser sites ,29,30, her sites . In contPPARG2 Pro12Ala variant and reported no statistically significant interaction [PPARG1 acts as an oncogene and PPARG2 inhibits proliferation in prostate cancer cells [PPARG2 Pro12Ala variant in prostate cancer, the interaction needs to be investigated in other study populations.Regarding prostate cancer, we found only one study, a nested case-control study among male smokers in Finland. This study investigated the interaction of dietary fat intake with eraction . There ier cells . Althouger cells . Furtherer cells ,37. GivePPARG2 Pro12Ala polymorphism. In general, CC allele carriers had an increased risk of breast cancer compared with G allele carriers [One study of breast cancer examined its association with alcohol consumption among postmenopausal women after stratifying by carriers . PPAR-γ carriers ,42,43,44carriers , which mPPARG2 Pro12Ala allele polymorphism. In the future, additional studies are warranted to elucidate the link between bioactive food components and cancer risk at sites with moderate to high PPARG expression such as the digestive tract  with high levels of bioactive food components [PPARG2 Pro12Ala allele polymorphism, although limited studies were available. This may be due to side effects of full PPAR-γ agonists reported for type 2 diabetes, which might have nullified beneficial effects. Moreover, CC allele carriers were more susceptible to colorectal cancer and G allele carriers were more susceptible to gastric cancer [Other than the three cancer sites , we did not find any study of other cancer sites that investigated the interaction between diet and mponents ,37. Regac cancer ,17, whicPPARG2 Pro12Ala allele polymorphism in the association with cancer risk. We were able to include a large number of study participants in this review . Moreover, we included previous studies conducted from a wide range of geographic locations, which facilitated to cover a wider range of dietary factors that could not have been achieved within one study population. This study also has limitations. First, we used only one database, PubMed, with potentially a limited number of studies available. Moreover, although all included studies had good quality based on the risk of bias assessment, they were not without potential bias nor were we able to fully control the quality of these studies. There was heterogeneity in reporting of interaction effects among the studies included in this review, which did not allow us to conduct a meta-analysis. Hence, we provided a comprehensive review with detailed descriptions. Future studies of diet-gene interactions need to consider more uniform reporting, such as by modeling low dietary intake and common allele groups as reference.This study has several strengths. To our knowledge, this is the first systematic review on diet-gene interactions of PPARG2 Pro12Ala polymorphism on the association between dietary factors and cancer risk. For colorectal cancer, the most studied cancer site, risk factors  were more detrimental in individuals carrying the G allele, whereas high levels of protective factors  were more beneficial in individuals carrying the G allele. In contrast, dietary fat and meat intakes were equally detrimental, and fish intake was equally protective in both PPARG2 Pro12Ala genotypes, which need to be confirmed in future studies. More evidence is currently available on interactions of PPARG2 Pro12Ala polymorphism with dietary factors other than well-known full PPAR-γ agonists, suggesting that partial PPAR-γ agonists or other novel bioactive compounds may be more relevant for the PPAR-γ’s involvement in carcinogenesis. Although limited evidence is currently available, future studies may need to focus more on such dietary factors, especially for cancers in the digestive tract that have relatively high amounts of bioactive food components and PPARG expression.In conclusion, our systematic literature review found limited evidence on modifying effects of


PARP‐1 gene, is highly implicated in the susceptibility of cancer. However, the roles of PARP‐1 rs1136410 C>T on cancer risk vary from different studies. We comprehensively screened all qualified publications from several databases, including PubMed, EMBASE, MEDLINE, CNKI and Wanfang. The searching was updated to April 2020. Our meta‐analysis included 60 articles with 65 studies, comprised of a total of 23 996 cases with cancer and 33 015 controls. Overall, pooled data showed that the PARP‐1 rs1136410 C>T polymorphism was significantly but a border‐line associated with an increased risk of overall cancer . Subgroup analysis indicated that rs1136410 C allele contributed to high risk among gastric, thyroid, and cervical cancer, but lower risk among brain cancer. Furthermore, increased cancer risk was detected in the subgroups of Asian, controls from population‐based design studies, and HWE ≤ 0.05 studies. Sensitivity analysis and Egger's test showed that results of the meta‐analysis were fairly stable. The current study indicated that PARP1 rs1136410 C>T polymorphism may have an impact on certain types of cancer susceptibility.Poly(ADP‐ribose) polymerase‐1 (PARP‐1) is a nuclear chromatin‐associated enzyme involved in the DNA damage response. SNP rs1136410 C>T, the most studied polymorphism in  Numerous SNPs have been identified in PARP‐1 gene. Among them, rs1136410 T>C  is a non‐synonymous polymorphism that could change valine to alanine. PARP‐1 rs1136410 T>C genetic polymorphism was previously investigated in various types of cancer. However, the results of epidemiological studies are inconsistent and contradictory. The present work aims to fill this gap in the literature by presenting the latest updated meta‐analysis of the available evidence in elucidating the relationship of PARP‐1 rs1136410 T>C and the risk of cancer.Poly(ADP‐ribose) polymerases (PARP), also known as ADP‐ribosyl‐transferase diphtheria toxin‐like (ARTDs), are evolutionary‐conserved family of proteins involved in diverse biological.22.1PubMed, EMBASE, MEDLINE, Wanfang, and CNKI were searched for English/Chinese‐language articles published from January 1990, through April 2020. The following syntaxes were used: (a) PARP‐1 or poly (ADP‐ribose) polymerase 1 or PARP1 or ADPRT or ADPRT1 or rs1136410 C>T; (b) SNPs or polymorphisms or polymorphism or variants; (c) cancer or cancers or carcinoma or tumour or neoplasm. To obtain other appropriate publications, we also manually examined the references of the selected articles. Eligible criteria were as follows: (a) case‐control study; (b) assessing rs1136410 C>T and cancer risk; and (c) enough information in allele frequency. Editorials, reviews, meta‐analysis, case‐only studies, duplicate studies were ruled out.2.2For each included study, a reviewer (H. Li) abstracted relevant study characteristics:  and classified the data into a structured form. Another reviewer (Y. Zha) checked all data for completeness and accuracy. Disagree parts (the conflicted information extraction by the two authors) were resolved through discussion until consensus was made.2.3P > .05 indicates not violating HWE. The association between PARP‐1 rs1136410 C>T and cancer risk were assessed by calculating ORs with the corresponding 95% CIs. Significant heterogeneity exists if I2 > 50%. If so, the random‐effect model was adopted, otherwise, the fixed‐effect model was used. Subgroup analyses by ethnicity, cancer type, source of control, and HWE in controls were performed to detect the source of heterogeneity. We also assessed the quality of each included study, the detailed method was described elsewhere.P value < .05 implies a significant finding.We used a chi‐square test to determine if genotype frequencies in controls of each study conformed to Hardy‐Weinberg equilibrium (HWE). 33.1Initial retrieval from PubMed, EMBASE, and MEDLINE databases got a total of 298 potentially relevant published records. We also obtained 12 articles from CNKI and Wanfang database. After titles and abstracts screening, 248 not relevant records were excluded. 4 articles were excluded due to being covered by others. A total of 58 case‐control design articles with reporting frequency of genotypes were included. Additionally, 2 eligible articles were also identified from references cited in the obtained articles. Ultimately, 65 studies from 60 publications were included Table . A total3.2The main results of the meta‐analysis were shown in Table 3.3Q test (P < .001) implied an existence of significant heterogeneity under all the genetic models. Therefore, a random‐effect model was applied to produce ORs and 95% CIs. In addition, the sequential sensitivity analysis was conducted to give an evaluation of the impact of a single study on the pooled ORs. The data of meta‐analysis is of great reliability, as no statistical fluctuation of the pooled ORs incurred after omitting in each study ; Writing‐original draft . Yong‐Jiu Zha: Data curation ; Writing‐original draft . Jie Liu: Methodology ; Software (supporting); Validation . Fang Du: Investigation ; Software ; Supervision . Xiao‐Quan Li: Supervision ; Visualization ; Writing‐review & editing . Xu Zhao: Funding acquisition ; Resources ; Supervision ; Visualization ; Writing‐review & editing .App S1Click here for additional data file.


Iron deficiency (ID) is concerned as the most common nutritional deficiency worldwide. The effects of ID on thyroid function and autoimmunity in pregnant women and reproductive-age women are controversial. The aim of the current study was to summarize the evidences and evaluate the relationship between ID and thyroid disorders.In this systematic review and meta-analysis, studies published on the Cochrane, Embase, Medline, and PubMed databases by October 2020 were searched. A total of 636 studies which discussed the correlation between ID and thyroid disorders were eligible in the initial search. Pooled mean differences (MD) and 95% confidence intervals (CI) were calculated for the assessment of thyrotropin (TSH) and free thyroxine (FT4) levels. Combined odd ratios (OR) and 95% CI were calculated for the assessment of the prevalence of overt and subclinical hypothyroidism, positive thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb).P = 0.01) and both positive TPOAb and TgAb . The meta-analysis of pregnant women showed that pregnant women with ID had increased serum TSH levels  and decreased FT4 levels . Meanwhile, the prevalence of overt  and subclinical  hypothyroidism in pregnant women with ID was significantly increased.For women of reproductive age, ID could significantly increase the risk of positive TPOAb (OR: 1.89; 95% CI: 1.17, 3.06: ID may adversely affect thyroid function and autoimmunity of pregnant and reproductive-age women and it is very necessary for monitoring iron nutritional status and early treatment of ID for them. Thyroid dysfunction is a common endocrine disorder in pregnant women, and consists of imbalanced thyroid hormone levels  and positive thyroid antibody status. Studies have shown that about 0.3%–3% of pregnant women suffer from hypothyroidism . HypothyIron is an important micronutrient for maintaining cell energy and metabolism . Iron deA systematic review and meta-analysis was conducted to answer the following PICO question: “Do pregnant or reproductive-age women with ID have a higher risk of thyroid function or autoimmune abnormalities than them without ID?” The Preferred Reporting Items for systematic review and meta-analysis protocols (PRISMA-P) were referenced in the process of carrying out our meta-analyses .Literature published on the Cochrane, Embase, Medline and PubMed databases by October 2020 were searched. The search keywords used were: iron, pregnant, pregnancy, reproductive-age, thyroid function, thyroid dysfunction, thyroid disease, hypothyroidism, hyperthyroidism, thyroid peroxidase antibody, and thyroglobulin antibody. The search formula and the number of results in each database were shown in The inclusion criteria were as follows: Reproductive-age women (Women aged 15–49 years old who can give birth to a baby) or pregnant women were considered as the research object; studies in English language; studies discussed the correlation between ID and thyroid function or autoantibodies; participants were divided into groups according to with ID or not; data on thyroid function indicators, autoantibodies, or the prevalence of overt hypothyroidism and subclinical hypothyroidism can be extracted. Books, conference abstracts, reports, comments, and animal experiments that could not be used for further data extraction and analyses were excluded.Two of the researchers extracted the following information of the included studies independently: first author, publication year, country of the population, pregnant stage, participants number in each group, diagnostic criteria for ID and thyroid disorders, study type, TSH and FT4 values from participants with or without ID, the events number of overt hypothyroidism, subclinical hypothyroidism, positive TPOAb and TgAb, and positive TPOAb, positive TgAb from participants with or without ID.The Agency for Healthcare Research and Quality (AHRQ) scale was used for the assessment of the quality of the included studies. Studies with 0–3 points, 4–7 points, and 8–11 points were considered as low-, moderate-, and high-quality, respectively .We imported the data into the Review Manager software (Revman 5.4.1) to evaluate the differences between TSH and FT4 values of participants with or without ID, and to compare the prevalence of overt hypothyroidism, subclinical hypothyroidism, and positive thyroid autoantibodies. For dichotomous outcomes, the Mantel–Haenszel statistical method was used to calculate the significance of the pooled odds ratios (OR). For continuous outcomes, the Inverse-Variance statistical method was used to calculate the significance of the pooled mean differences (MD). Some studies provided data as median and interquartile range (or maximum and minimum), and we calculated their mean and standard deviation according to formulas , 19. TheI2 was used to estimate the level of study heterogeneity. I2 values of 25%, 50%, and 75% were identified as low, medium, and high heterogeneity, respectively. When I2 was greater than 50, the random-effects model was used to summarize the results. When I2 was less than 50, the fixed-effects model was used to summarize the results. Sensitivity analyses were conducted to interpret the source of heterogeneity. The protocol of the sensitivity analysis was to delete one study from each rotation and then re-calculated the pooled results of the remaining studies. P < 0.05 was considered to indicate statistical significance.>Begg’s tests and Egger’s tests were used to estimate the publication bias.A total of 636 articles were searched from the Cochrane, Embase, Medline and PubMed databases based on the keywords. After removing the duplicate articles, 445 articles’ titles and abstracts were read. Sixteen of them were downloaded in full and read carefully. Eight articles were excluded because the data couldn’t be extracted , 21 or tP = 0.25; I2: 42%). Sensitivity analyses showed that the combined MD was stable after one research had been deleted. Begg’s test (P = 1.000) and Egger’s test (P = 0.753) did not indicate publication bias.The pooled results from the comparison of serum TSH levels between ID group and control group were shown in I2: 96%). Heterogeneity decreased when Zhang et al.’s article was removed (I2: 21%). Begg’s test (P = 1.000) and Egger’s test (P = 0.462) did not indicate publication bias.The pooled results from the comparison of serum FT4 levels between ID group and control group were shown in P = 0.01; I2: 0%; Compared with participants in control group, participants in ID group had higher risk of positive TPOAb . Sensitivity analyses showed that the combined MD was stable after one research had been deleted. Begg’s test (P = 0.707) and Egger’s test (P = 0.910) did not indicate publication bias.Meta-analysis of the six articles using the pooled results from the comparison of serum TSH levels between ID group and control group were shown in P < 0.00001; I2: 87%). Sensitivity analysis showed that the combined MD was stable after one research had been deleted. In order to explore the source of heterogeneity, we conducted a subgroup analysis based on the different diagnostic criteria of ID. The heterogeneity was still high after the subgroup analysis, which might be due to the different time of the diagnosis of ID and the measurement of biochemical indicators in different articles. Begg’s test (P = 0.230) and Egger’s test (P = 0.152) did not indicate publication bias.Meta-analysis of the six articles using the pooled results from the comparison of serum FT4 levels between ID group and control group were shown in P = 0.004; I2: 0%; Compared with control group, subjects in ID group had higher risk of overt hypothyroidism . Sensitivity analyses showed that the combined OR was stable after one research had been deleted. To explore the source of heterogeneity, a subgroup analysis was conducted based on the different diagnostic criteria of ID. The subgroup analysis showed that subjects in ID group had higher risk to have positive TPOAb  and Egger’s test (P = 0.851) did not indicate publication bias.The pooled results from the comparison of serum TPOAb levels between ID group and control group were shown in P = 0.25; I2: 0%).The pooled results from the comparison of serum TgAb levels between ID group and control group were shown in P = 0.22; I2: 0%; There was no significant association of autoantibodies-positive status between ID group and control group .The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


The hyperechogenicity of the substania nigra (SN) has been established as a valid finding in patients with Parkinson’s disease (PD), probably caused by an increased tissue iron concentration in the SN. The application of transcranial sonography (TCS) has been investigated for further echogenic basal ganglia alterations in patients with extrapyramidal movement disorders. Compared to PD, a hyperechogenic nucleus lentiformis (LN) has been reported to appear more frequently in atypical parkinsonian syndromes (aPS) such as the parkinsonian phenotype of multiple system atrophy (MSA-P) or the progressive supranuclear palsy (PSP). As the evidence providing study sizes are small, we conduct the first meta-analysis of the prevalence of LN hyperechogenicity in PD and aPS. We search for available studies providing prevalence of LN hyperechogenicity in patients with PD and aPS (MSA-P and PSP) detected by TCS in MEDLINE and SCOPUS databases. We calculate the prevalence rates of LN hyperechogenicity detection in patients with clinical diagnosis of PD vs. aPS under the random-effects model. We include a total of 1330 patients, 1091 PD and 239 aPS (MSA-P and PSP). We find a significantly higher prevalence of LN hyperechogenicity in aPS  compared to PD . After proving a higher prevalence of LN hyperechogenicity in aPS compared to PD, its histopathological cause needs to be investigated. Furthermore, its full diagnostic accuracy and the qualification to serve as a risk factor for MSA-P and PSP should also be questioned in future studies. Transcranial sonography (TCS) in Parkinson’s disease (PD) has been increasingly applied over the last two decades and has proven to be a very helpful tool in the diagnostic process and risk stratification of extrapyramidal movement disorders . SubstanThe present systematic review and meta-analysis was conducted according to the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement . We sear2 statistics. For the subgroup analyses we used a standard test for heterogeneity across subgroup results to investigate potential differences between subgroups. All statistical analyses were performed with the use of the Stata Statistical Software Release 13 for Windows .We calculated the rates of LN hyperechogenicity detection by TCS by dividing the number of cases (patients with LN hyperechogenicity) by the total number of patients receiving TCS. After the overall analysis, we performed subgroup analyses according to the clinical diagnosis of PD vs. aPS. For all proportion analyses we implemented the variance-stabilizing double arcsine transformation . The ranFrom research on MEDLINE and SCOPUS we found 150 potentially relevant articles. The remaining 15 ,25,26,272 =8 7.08%, aPS: I2 = 69.35%). For the PD group, the prevalence of LN hyperechogenicity was calculated to 16% (95% CI: 0.10-0.23) and ranged from 0% to 64%. In the aPS group, the corresponding prevalence was 76% (95% CI: 0.62–0.88) with a range from 0% to 100%. Heterogenicity was substantial for both groups , but studies specifically targeting this question are lacking ,28. UntiTCS is a rapid, low-cost, non-invasive and safe examination with a very good and reliable interrater agreement. The SN hyperechogenicity has been identified as a risk factor to develop PD ,32. DespBased on animal and post-mortem studies, it has been suggested that SN hyperechogenicity in TCS is caused by an increase of the iron concentration in the SN ,35,36,37To our knowledge, this is the first meta-analysis assessing the prevalence of LN hyperechogenicity in TCS for patients with PD and aPS (MSA-P or PSP). The literature search and data extraction were thoroughly conducted to avoid any bias, especially to exclude calculation with the same cohorts in case of identical authorships in different studies. Despite the greatest care, this is a general problem for meta-analysis and cannot be completely solved. This meta-analysis revealed a high prevalence of LN hyperechogenicity in aPS compared to PD, underlining the importance of TCS examination for the diagnostic process of parkinsonian syndromes. From the neuropathological point of view, MSA-P and PSP are distinct diseases ,29 which


SPP1 polymorphisms and susceptibility to urolithiasis have apparent inconsistencies with no data available for local population.Urolithiasis is a worldwide urological problem with significant contribution of genetic factors. Pakistan, which resides within the Afro-Asian stone belt, has a high reported prevalence (12%) of urolithiasis. Osteopontin (SPP1) is a urinary macromolecule with a suggested critical role in modulating renal stone formation, genetic polymorphisms of which may determine individual risk of developing urolithiasis. However, results of previous studies regarding SPP1 genetic polymorphisms in an effort to investigate potential association with urolithiasis using indigenous candidate gene association study design. Further, a comprehensive meta-analysis following a systematic literature search was also done to ascertain an evidence based account of any existent association regarding SPP1 promoter polymorphisms and risk of developing urolithiasis.A total of 235 urolithiasis patients and 243 healthy controls, all of Pakistani ancestry, underwent genotyping for six SPP1 promoter polymorphisms, rs2853744:G > T, rs11730582:T > C and rs11439060:delG>G, were found to be significantly associated with risk of urolithiasis in indigenous genetic association study . We also observed a 1.68-fold positive association of a tri-allelic haplotype of these SPP1 promoter polymorphisms (G-C-dG) with risk of urolithiasis . However, no association was evident when data were stratified according to gender, age at first presentation, stone recurrence, stone multiplicity, parental consanguinity and family history of urolithiasis. The overall results from meta-analysis, which included 4 studies, suggested a significant association of SPP1 rs2853744:G > T polymorphism with susceptibility of urolithiasis , but not for other SPP1 polymorphic variants analyzed.Three SPP1 polymorphisms with urolithiasis for the first time from South Asia, however, this association persisted only for SPP1 rs2853744:G > T polymorphism after meta-analysis of pooled studies. Further studies with a larger sample size will be required to validate this association and assess any potential usefulness in diagnosis and prognosis of renal stone disease.In conclusion, we report significant association of 3  Urolithiasis is a common urological problem   causing The reported etiology of urolithiasis is multifactorial involving environmental and genetic risk factors with heritability of 50% , 7. The SPP1 knockout animal models suggesting an important role of osteopontin in various phases of renal stone formation, including crystal nucleation, aggregation, retention, adhesion to renal epithelial cells and stone formation , presenting at five different tertiary care hospitals of Punjab, during a period of 29 months. All urolithiasis patients provided clinical and pedigree details, with confirmation provided by their attending clinician (a urologist) in addition to relevant medical records, and whole blood samples (EDTA anticoagulated) for genetic study. In addition, 243 healthy subjects that were age and gender matched with same ethnic origin having no personal or familial antecedents of urolithiasis were also recruited as control group. Specific details pertaining to enrollment of study subjects and their baseline characteristics have been described earlier .SPP1 gene including five promoter polymorphisms  by Sanger sequencing and one coding polymorphism (rs1126616:C > T) by PCR-RFLP based approach . Two researchers independently determined the genotypes of all SPP1 polymorphisms, based on DNA sequencing or PCR-RFLP, to minimize chances of genotyping bias.Subjects were genotyped for six polymorphisms of SPP1 polymorphisms that violated HWE, as indicated by p < 0.05 for in the control group, were not processed for further data analyses. Odds ratios (ORs) with associated 95% confidence intervals (CI) were determined to assess strength of statistical association, if any, considering allelic, genotypic, recessive, dominant and log-additive models by the same SNPstats program. The pairwise linkage disequilibrium and haplotype analysis for SPP1 polymorphisms was conducted using the Haploview program  [The observed overall heterogeneity in the results of different studies regarding association of ctively] –39; b) ectively] ; and c) SPP1 polymorphisms and risk of urolithiasis. To the best of our knowledge, no meta-analysis has been carried out previously regarding association of SPP1 promoter polymorphisms with urolithiasis risk. The results of present meta-analysis reveal that GG genotype of SPP1 rs2853744:G > T significantly increased the risk of urolithiasis by 1.37 fold in a recessive model. However, no significant association between other SPP1 polymorphisms analyzed (rs11730582:T > C and rs11439060:delG>G) was observed after correction for multiple testing. Several indicators of the robustness of analyses done and results generated in the current meta-analysis can be identified including; a) all the studies included in the meta-analysis were in HWE, b) no publication bias or heterogeneity was observed except for rs11439060:delG>G, c) a single study did not influenced the cumulative results as suggested by sensitivity analysis, and d) correction for multiple testing was applied. Inclusion of Pakistani dataset in the overall meta-analysis also reinforced the results obtained in this study. However, the results should still be interpreted with caution because of the limited number of primary studies available for present meta-analysis.Meta-analysis is a powerful tool that provides evidence based comprehensive and reliable results compared to a single study when investigating association of potential risk factors and disease phenotype. Therefore, in addition to presenting results of indigenous study, we also conducted a meta-analysis to clarify the possible association between SPP1 coding region genetic variant (rs1126616:C > T) and lower serum and urine osteopontin levels with increased risk of developing urolithiasis [SPP1 polymorphism (including SPP1 promoter polymorphisms investigated in this study) in the analysis, which limits the usefulness and broader applicability of that study.Currently, there is only one meta-analysis available on the subject which revealed positive association of ithiasis , howeverSPP1 polymorphisms because we could find only a couple of studies with limited sample size.Despite the efforts made to generate evidence based and robust statistical results through current case control and meta-analysis study, a number of limitations should be acknowledged. First, a comprehensive investigation and correlation of biochemical parameters of renal stone disease  could not be done due to limited resources available. Second, all the eligible studies, including our own data, could not address all the known risk factors involved. Keeping in view the multifactorial nature of the urolithiasis phenotype, a more comprehensive and precise analysis should be based on adjusted estimates considering covariates such as gender, age, lifestyle, dietary habits including fluid intake, and other genetic factors, thus also investigating gene-gene and gene-environment interactions. Third, sub-group analysis based on ethnicity, source of control samples and other factors, could not be performed due to limited number of published studies available for current meta-analysis. Further, we did not include other SPP1 promoter polymorphisms and their tri-allelic haplotype with increased risk of urolithiasis from South-Asian region under the indicated genetic model. In addition, evidence from meta-analysis part of the study supports the positive association of rs2853744:G > T SPP1 SNP and susceptibility of urolithiasis. Further studies using larger sample sizes and analyses of gene-gene and gene-environment factors in diverse populations are suggested to validate and determine usefulness and broader relevance of SPP1 and other genetic polymorphisms in accessing risk and prognosis of urolithiasis.In conclusion, the current study provides first account of a modest but statistically significant association of three Additional file 1. Oligonucleotide sequences, PCR conditions and restriction enzyme used for the genotyping of SPP1 gene polymorphisms.Additional file 2. Basic characteristics of the study participants in the case-control part of the study.Additional file 3. Basic information and HWE analysis for SPP1 gene polymorphisms analyzed in this study.Additional file 4. Representative electropherograms for each genotype of three SPP1 polymorphisms. (A) rs11730582:T > C, (B) rs2853744:G > T and (C) rs11439060:delG>G.Additional file 5. Pairwise linkage disequilibrium (LD) map, based on D´ values, of SPP1 polymorphic markers analyzed in the present study. No significant LD was apparent in any of the SPP1 polymorphic pairs analyzed.Additional file 6. A Association of SPP1 rs2853744:G > T with different clinical characteristics of urolithiasis. B Association of SPP1 rs11730582:T > C with different clinical characteristics of urolithiasis. C Association of SPP1 rs11439060:delG>G with different clinical characteristics of urolithiasis.Additional file 7. Meta-analysis of SPP1 rs11730582:T > C polymorphism with risk of urolithiasis. a) and b) Forest plots of urolithiasis association with rs11730582 polymorphism using dominant and recessive model, respectively. c) and d) Funnel plots of rs11730582 polymorphism assuming dominant and recessive inheritance, respectively, using fixed effect model.Additional file 8. Meta-analysis of SPP1 rs11439060:delG>G polymorphism with susceptibility of urolithiasis. a) and b) Forest plots of urolithiasis association with rs11439060 polymorphism following dominant and recessive model, respectively. c) and d) Funnel plots of rs11439060 polymorphism using dominant and recessive inheritance, respectively, by random effect model.Additional file 9. Raw dataset with details of genotypes and phenotypes of every study subject analyzed for SPP1 polymorphisms in this study.


Background: Bluetongue caused by the bluetongue virus (BTV) is a non-contagious and an insect-borne disease mainly affecting domestic and wild ruminants. Bluetongue in cattle is associated with vesicular lesions, weight loss, low milk production, and low reproductive capacity. It should not be ignored as it is associated with large economic losses to the livestock breeding industry in China. Although many studies have investigated bluetongue virus infection in cattle, no nationwide study on the prevalence of bluetongue virus infection in cattle from China has yet been conducted. This meta-analysis aimed to evaluate the seroprevalence and risk factors for bluetongue in cattle.Results: We collected 50 publications from 1988 to 2019 through PubMed, ScienceDirect, Chinese Web of Knowledge (CNKI), VIP Chinese journal database, and Wanfang database. A total of the pooled bluetongue seroprevalence of 12.2%  in cattle was tested. The point estimate of bluetongue collected from 2001 to 2011 was 22.5% (95% CI: 1.2–58.9), which was higher than after 2012 . The analysis of the feeding model subgroup revealed that the seroprevalence of bluetongue was significantly higher (P < 0.05) among free-range cattle  than among cattle from intensive farming systems . The seroprevalence of bluetongue in different species showed significant variation (P < 0.05), with the highest seroprevalence of 39.8% (95% CI: 18.7–63.0) in buffalo and the lowest seroprevalence of 4.3% (95% CI: 1.2–9.0) in yak. In the zoogeographical division subgroup, the seroprevalence of bluetongue correlated positively within a certain range with the species distribution of Culicoides.Conclusion: Our findings suggested that bluetongue was prevalent in cattle in China. In addition, the contact with sheep, other ruminants, or transmission media such as Culicoides may increase the seroprevalence of bluetongue disease in cattle. It is necessary to carry out continuous monitoring of the bluetongue seroprevalence. Moreover, comprehensive and improved strategies and measures should be implemented to prevent and control the spread of bluetongue. Bluetongue (BT) is highly prevalent and unevenly distributed among Chinese cattle.The animal disease prevention plan may effectively reduce this epidemic in cattle.An intensive farming model may play an active role in the prevention of BT in cattle.This is the first meta-analysis of BT seroprevalence in cattle in China.Orbivirus of the family Reoviridae and transmitted through biting by hematophagous midges of Culicoides (Bluetongue caused by the bluetongue virus (BTV) is an arboviral non-contagious disease of domestic and wild ruminants and is designated as a reportable disease by the World Organization for Animal Health (OIE) . BTV is licoides . BTV is licoides –4, leadilicoides , 6.Culicoides  and “bluetongue” (in Chinese) were used for advanced search in the Chinese databases. All the Chinese databases used fuzzy search and synonym expansion. All the retrieved citations were imported into Endnote X9 (version 9.3.1).Eligible studies were selected in accordance with the following criteria: (1) the objects of the research must be cattle; (2) the study aim must be to investigate the seroprevalence of bluetongue infection in cattle; (3) data must include information on the number of examined cattle and the number of bluetongue-positive cattle; (4) the study location must be in China; (5) the study design must be a cross-sectional study; and (6) the study must be published in Chinese or English. Studies that did not meet all the abovementioned criteria were excluded. Duplicate studies and review studies (not research papers) were also excluded.-positive cattle, diagnostic tests, and farming mode. To reduce the heterogeneity caused by the different detection methods, we only extracted the results of the serological detection methods [agar gel immunodiffusion (AGID) and enzyme-linked immunosorbent assay (ELISA)] in the study and always used ELISA as the primary detection method. When a study used both ELISA and AGID (or other methods), we extracted only the rate obtained by the ELISA method for subsequent data analysis. The database was established by Microsoft Excel (version 16.32).Four trained reviewers performed the data extraction separately. Any differences in the process were determined by another reviewer (the author of this article). The following information was extracted from all the collected studies: first author, publication year, sampling year, geographical region of the study, cattle variety, total number of examined cattle, the number of bluetongueWe assessed the quality of the publications selected based on these criteria using a method derived from the Grading of Recommendations Assessment, Development, and Evaluation method –27. StudWe conducted this meta-analysis of proportions in R v3.5.2 , where the “meta” package was used to estimate the models . When thI2 and Cochrane Q statistics . I2 < 50% indicates low heterogeneity; I2 > 50% indicates high heterogeneity, which describes the percentage of differences between studies due to heterogeneity.High heterogeneity can be expected in the meta-analysis of seroprevalence. Therefore, we use the random-effect model in advance to perform overall data integration and subgroup analysis. We assessed the heterogeneity between studies using the The visualized statistical results of the meta-analysis were represented by forest plots. The funnel plot and Egger's test were used to detect publication bias, and sensitivity analysis was used to verify the stability of results. Subgroup analysis and single-factor regression analysis were used to analyze heterogeneity. The following codes were used for this portion of the analysis:P-value, Egger's test was used to assess the publication bias of studies. The bias was considered to be non-existent when P ≥ 0.05. There may be publication bias if P < 0.05. In the sensitivity analysis, one study was deleted at a time and other studies were analyzed to estimate whether a single study would have a significant impact on the results.In the funnel diagram, the symmetry of the figure is judged subjectively. If it is symmetrical, there may be no publication bias or heterogeneity. If it is asymmetric, there may be publication bias or heterogeneity. According to the Simultaneously, we conducted subgroup analysis stratified by the following potential risk factors: the investigated factors included the region (Northern China vs. other regions), sampling year (2012 or later vs. 2000 or before and 2001–2011), detection method [competitive (C)-ELISA vs. AGID], cattle variety , farming mode (comparison of intensive farming with free range), and study quality (high vs. middle and low). In the meta-analysis of seroprevalence, the detection method is usually the source of heterogeneity. Here, we used the detection method as a covariate and performed multivariate meta-regression analysis with other risk factors to explain the heterogeneity caused by the detection method.Culicoides species mentioned . A total of 87,472 cattle across seven regions and 23 provinces of China were investigated, and the results revealed that the pooled seroprevalence of bluetongue was 12.2%  (Table 2). According to our quality criteria, 5 papers were considered to be of high quality (four or five points), 34 were of moderate quality (two or three points), and the remaining 11 papers were deemed to be of low quality (zero to one point).The .4–16.6) , Table 2Four positive conversions were performed on the data . The rest = 4.582, P = 3.294e−05, indicating that there might be publication bias in the included studies . There was significantly high heterogeneity in all the subgroups, and all estimates of the pooled seroprevalence for each subgroup were calculated using the random-effects model. In terms of geographical region, the highest seroprevalence of bluetongue was 45.9%  in Southern China and the lowest seroprevalence was 0.1%  in Northeastern China, and the difference was statistically significant (P < 0.05). We obtained preliminary statistics on the seroprevalence of bluetongue in different provinces. The results showed that the highest positive rate of bluetongue was 46.3% (95% CI: 29.5–63.5) in Guangxi Province, followed by Guangdong at 45.4% (95% CI: 15.8–76.9). The seroprevalence of bluetongue in Hebei , Heilongjiang , and Jilin  was lower than that in other provinces  among free-range cattle at 22.5%  than among intensive farming cattle at 1.8% . The pooled seroprevalence of bluetongue in different species showed significant variation (P < 0.05), with the highest seroprevalence of 39.8%  in buffalo and the lowest seroprevalence of 4.3%  in yak. The seroprevalence of bluetongue investigated by AGID was 12.2% , and in the C-ELISA test, it was 11.6% , and no significant difference was found (P = 0.717)  = 99.04%] and had the least impact on the research quality  (Culicoides (n = 129).Furthermore, the pooled seroprevalence of bluetongue was 16.6%  in cattle collected before 2000, 22.5%  in cattle collected during 2001–2011, and 9.9%  in cattle collected in 2012 or later. The estimated pooled seroprevalence of bluetongue was significantly higher (= 0.717) . In addi 99.51%) . In the P < 0.05).Regression analysis showed that the region, cattle variety, farming mode, and quality score subgroup might be the main sources of heterogeneity , which may lead to unstable results. In addition to climatic factors, further cross-province circulation of animals and animal products should be verified. The present study confirms the widespread seroprevalence of bluetongue in cattle in China , with statistical significance among different regions . We founin China .50 (median effective dose) . Diagnostic technology for bluetongue disease of China GB/T 18636-2017) stipulates that AGID and C-ELISA are suitable for detecting BTV antibody in serum samples. Since the establishment of the 2002 standard, reverse transcription–polymerase chain reaction (RT-PCR) and fluorescent RT-PCR molecular biological detection methods have been added. Molecular biology is currently the best detection method, with high sensitivity and strong specificity. RT-PCR methods were able to detect representative strains of all 24 BTV serotypes and different BTV serotypes in the Mediterranean region, with a detection limit of < 0.01 ECEve dose) , 85. How36-2017 sve dose) . C-ELISAve dose)  and has ve dose) , its intve dose) , causingve dose) . It is nP = 0.015) may be the source of heterogeneity . Then, we carried out multivariate meta-regression analysis on varieties with years as covariates, and the results revealed that years were not the source of heterogeneity in the subgroup . We speculated that the difference in the seroprevalence between cows and yellow cattle may be caused by different breeding modes. However, data regarding the farming modes was insufficient for multivariate meta-regression analysis on varieties and farming modes. In general, dairy cows are mostly under the intensive farming system, while yellow cattle are mostly in the free-range system as draft cattle or beef cattle. This result is consistent with the farming mode subgroup.In different regions, with global warming, there is an indication that the prevention and control of bluetongue in cattle and other animals should be paid more attention. BTV infection may exhibit annual variation due to climatic modulation . MoreoveThe results revealed a significant difference in the seroprevalence of bluetongue between cattle in the free-range and intensive farming systems in the farming mode subgroup, indicating that risk behaviors do differ between farming mode. Intensive farming greatly reduced the infection rate of bluetongue disease, indicating that intensive farming had more advanced technologies  and better management in this regard. Moreover, cattle from the free-range farming system had a larger range of activities and more likely to be bitten by mosquitoes transmitting the BTV . TherefoWe tried to determine season as a potential risk factor, but results could not be obtained due to lack of adequate data. However, we speculated that season may be one of the potential risk factors affecting the change in seroprevalence, because warm temperature and human environment are positively associated with animal habitats. In fact, a 1°C increase in temperature has been reported to increase the risk of bluetongue by 27% . OptimalP = 0.009), suggesting that more risk factors should be collected as quality evaluation.In addition, we found that the study quality was the source of heterogeneity in the present study  and Northeastern China (n = 3) might not reflect the true seroprevalence in the investigated regions, and the quality level of the study was variable, suggesting that more surveillance of bluetongue infection should be continuously undertaken in cattle in these areas. Fifth, some of the included studies did not explicitly mention whether to use random sampling. Therefore, our research may have a sampling bias. Sixth, though the studies included in this review were eligible, most were of moderate or low quality. This may be due to the lack of the underlying factor of sampling randomness or sampling method. To prove the quality of research, more risk factors should be considered and analyzed in the future.There are some limitations in our meta-analysis that may affect the results. First, we found a number of potentially relevant studies through our systematic review, but not all the underlying studies were suitable for use. Therefore, some of these studies might not have been included in this meta-analysis, and some potential risk factors may be missed. Second, numerous qualified studies were acquired in our systematic review, but not all data were available. There is not enough data for the subgroup analysis on the seroprevalence of bluetongue, such as the breeding model and variety. Third, analyzable data were limited, involving age, sex, living environment, the presence or absence of sheep or other ruminants, the presence or absence of Based on a systematic meta-analysis, we assessed the seroprevalence of bluetongue in cattle from China. The results showed that bluetongue was epidemic in cattle in China. Region, variety, feeding methods, and other factors might affect the seroprevalence of bluetongue. We suggested that appropriate control schemes be formulated according to the differences in breeding patterns and geographical conditions in the various regions. It is also necessary to conduct epidemiological investigations on cattle in more regions to further explore the risk factors of bluetongue infection in cattle. Comprehensive surveillance programs should be adopted to prevent the spread of bluetongue in cattle.The original contributions presented in the study are included in the article/FL and RD are responsible for the idea and concept of the paper. D-LL, BZ, G-YG, and J-ML collected the data. QW, YZ, and X-YY analyzed the results. Q-LG wrote the manuscript. XL and KS revised the manuscript. All the authors contributed to the manuscript editing and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


BDNF gene with smoking, the findingsremain controversial, mainly due to small-to-moderate sample sizes. The main aim ofcurrent investigation is to explore whether the variant of Val66Met has any geneticfunctions in the progress of smoking persistence. The Val-based dominant geneticmodel considering Val/*  and Met/Met as two genotypeswith comparison of the frequency of each genotype in current smokers and neversmokers. There were seven genetic association articles including eight independentdatasets with 10,160 participants were chosen in current meta-analyticinvestigation. In light of the potent effects of ethnicity on homogeneity acrossstudies, we carried out separated meta-analyses according to the ancestry origin byusing the wide-used tool of Comprehensive Meta-analysis software (V 2.0). Ourmeta-analyses results indicated that the Val66Met polymorphism was significantlylinked with smoking persistence based on either all the chosen samples  or Asiansamples . No significant clue of bias in publications orheterogeneity across studies was detected. Thus, we conclude that the Val66Met(rs6265) variant conveys genetic susceptibility to maintaining smoking, and smokerswho carry Val/* genotypes have a higher possibility of maintaining smoking thanthose having Met/Met genotype.Although numerous genetic studies have reported the link betweenVal66Met in  Cigarette smoking, a chronic and complex brain-related disorder, hasbeen documented to lead to many diseases, including various cancers –3. NotabCHRNA5-A3-B4 gene cluster on the chromosome of15q24–25.1 region are remarkably linked with nicotine dependence [Twin- and family-based genetic studies –13 havependence , 19.Genetics-based linkage and association studies have implicated thefunctions of genetic components in the pathogenesis of smoking-related behaviors,including the effect on the dopamine-related reward circuit . NicotinBDNF gene in thechromosome 11p13–15, shows highly expression in the mammalian brain, and involves inregulation of multiple biological functions of neurons, such as neuron development,regeneration, survival, and maintenance [BDNFexpression in the rat hippocampus, whereas acute nicotine prominently decreases thegene expression of BDNF. Genome-wide linkageinvestigations have suggested that the chromosome 11p13 region is likely to harborgenes conferring susceptibility to nicotine dependence [BDNF implicated in vulnerability to smokingbehaviors.BDNF, encoded by ntenance . BDNF isntenance –27. Animntenance . These pntenance  have docpendence . Recent pendence , 31, 32 BDNF and dependence of nicotine inmale smokers based on European-American origin, a growing number of genetics-basedassociation researches [BDNF on smoking persistence. Thereby, we conducted ameta-analysis based on a large-scale sample sizes of existing studies for theassociation between rs6265 in BDNF and smokingpersistence.In particular, the genetic variant of Val66Met  has beeninvestigated extensively to influences the BDNF system. The functional polymorphismof Val66Met was observed to change BDNF intracellular packaging and trafficking,which affects the activity-dependent secretion of BDNF protein . Since Bsearches ,35–42 hhttps://www.ncbi.nlm.nih.gov/pubmed) for studies with regard to the association of variants inBDNF with smoking behaviors prior to June25, 2018. The searching keywords used were “susceptibility”, “polymorphism”,“genetics”, “variant”, “BDNF”, “brain-derivedneurotropic factor”, “smoking”, “nicotine”, “cigarette”, and “tobacco”.Abstracts were tested for possible related papers in consistent with the normalcriteria for inclusion and exclusion proposed by Moher et al. [We interrogated the public database of NCBI PubMed , criteria of diagnosis for defining smokingphenotype, and the count of subjects with distinct smoking status stratified bythe genotypes of rs6265.According to the “Quality of Reporting of meta-analysis and PRISMAguidelines” , nine stBDNFunder a dominant model with smoking persistence.As documented in previous studies , 18,44,Z-scoreexamination, and P value < 0.05 is thoughtto be significant.Firstly, we combined all datasets from the included articles toconduct an overall meta-analysis. Further, we performed separated meta-analysesthrough taking into account the underlying influence of different race: Asianancestry and Caucasian ancestry. Since there is only one study for Africanancestry, no stratified meta-analysis for this race. All meta-analyses wereconducted by employing the wide-used tool of Comprehensive Meta-analysissoftware package . The significance of acombined OR is calculated by a We used both random and fixed models for meta-analyses. Withrespect the random model based on DerSimonian and Laird methods , which aQ andI2 test[PQ < 0.05, and further it can be assessed by the valueof I2 (I2 = Q − df/Q), whichis employed for determining the percentage of evaluated variation acrossdifferent chosen studies resulting from heterogeneity instead of that by chanceof random. For a typical example, when I2 value is equal to 50%, theoutcomes from meta-analyses can inflate evaluated variation percentage notexplained by genotype to 50% [We used both Cochran’s dI2 test to evalue to 50% ,18. FurIn current study, we searched ten studies reported between 2007 and2017  with the 95% CIfrom 1.03–1.46 in both the fixed and random models .We first carried out an overall meta-analysis to reveal whether thelink of Val66Met genotypes in g et al.  was straP = 0.044) in the fixed model .Although there was no evidence of significant heterogeneity between studies ofCaucasian population , no significant association was detected. The nonsynonymous Val66Met (C196T) polymorphism (rs6265) islocated at the position of 196 in the genomic region encoding pro-BDNF protein,thyroid tissue (P = 6.30 × 10−6) and whole bloodsamples (P = 0.00135)  Fig. .Fig. 5ThBDNF and smoking persistence, and detected a prominent effect ofVal66Met polymorphism on smoking persistence based on a large-scale samples. Sincethere exist no significant evidence of heterogeneity across all chosen studies orpublication bias identified, we thus concluded that the Val allele play a crucialrole in the pathology of the persistence of smoking, suggesting that carriers ofVal/Val and Val/Met genotypes have a higher likelihood of maintaining smoking thanindividuals carrying the homozygous genotype of Met/Met.In current investigation, we first conducted a meta-analysis toidentify the association between Val66Met (rs6265) in BDNF gene, located on chromosome 11, has beenwell-reported to be correlated with substance abuses and psychiatric diseases, suchas nicotine dependence [P = 3.6 × 10−8).However, the pattern of the results for smoking persistence is inconsistent, whichprimarily because of the small sample size or sampling bias in each investigation.It remains an open question whether the genetic variant of rs6265 has an effect onsmoking persistence. The meta-analytic method is extensively thought to be aneffective tool for improving the power of our statistical analysis through combiningvarious studies on the same topic.The dopaminergic reward system functionally response to the stimulationof nicotine is regulated by BDNF protein, which could regulate dopamine D3 receptor(DRD3) expression through a regulation system of stimulating the function of theDRD1 . The encpendence ,31, alcpendence , schizoppendence , personapendence , and attpendence . The welpendence . Thers6pendence and incrpendence . Consistpendence , 54. Furpendence ,35–42. pendence  identifiIn view of recessive, additive, and allelic genetic models have nosignificant results, the Val-dominant model was mainly applied in currentmeta-analytic investigation. The rs6265 polymorphism was detected to besignificantly correlated with maintaining smoking based on all chosen samples andAsian ancestry-based samples. As for Caucasian population, we did not detect anyevidence for the link. The allele frequencies of Val allele of rs6265 variant showhighly differences across different population, with Val allele estimated to be~78.4% in Caucasian population but only about 51.5% among Asian populations, whichis in consistent with the findings reported by previous articles , 55. As BDNFVal66Met show genetic interaction with 5-HTTLPR variant in the serotonin transportergene. They demonstrated that individuals with BDNF Met variant and 5-HTTLPR LL havea higher scores of neuroticism, but with BDNF Val variant and 5-HTTLPR LL have alower scores of neuroticism.Although a significant association between rs6265 and smokingpersistence was observed, the findings of current meta-analytic investigation shouldbe cautiously explained in light of underlying flaws as listed in the following.First, smoking is a common brain disorder with a complex etiology influenced bymultiple factors and commonly show a comorbidity with other neuropsychiatricdisorders or drug addictions, which appears to have a highly likelihood to sharecommon genetic susceptibility components in the dopamine-related reward circuit.Further, the vast majority of the chosen studies did not offer relevant data thatallows us to include or exclude subjects with comorbidity diseases in the selectedsamples. Thus, these comorbidity diseases in included smokers or never smokers mightconfuse the results of current meta-analysis. Second, there existed distinct genderratios of subjects among these chosen articles, which might contribute to theexisting limitations, as indicated by many previous reported studies , 56, 57.In sum, our current meta-analyses show the Val66Met variant has amoderate effect on smoking persistence in a large-scale samples. Compared withindividuals with Met/Met genotype, individuals with Val/* genotypes have a 23%greater possibility of maintaining smoking, which suggests that thedopamine-relevant functions of Val66Met variant is implicated in mediating thebiological process of smoking persistence. More related molecular experiments areneeded to explore the biological function and regulation mechanism of the rs6265variant on smoking persistence and reveal the genetic interactions with other genes.Current investigation advances our understanding of genetic components underlyingsmoking persistence, and would contribute to the development of effective strategiesfor smoking cessation.Supplemental TablesSupplemental Figures