孟德尔随机化探究类风湿性关节炎与冠状动脉疾病因果关系以及步行速度的介导作用

目的类风湿性关节炎(rheumatoid arthritis, RA)患者的冠状动脉疾病(coronary artery disease, CAD)发生风险会升高。由于关节疼痛/僵硬或其他关节问题, RA患者的身体素质通常会有所降低,比如步行速度下降。但是,RA、步行速度和CAD这3者之间的因果关联目前尚不清楚。本研究旨在采用网络孟德尔随机化方法研究RA与CAD因果关系及步行速度在该因果关系中的介导作用。方法公共数据库下载RA、CAD和步行速度的全基因组关联研究(genomewide association study, GWAS)统计结果数据,进行两样本的孟德尔随机化分析。RA数据共有103 688例样本,CAD数据有547 261例样本,步行速度有452 264例样本。选取与RA和步行速度相关的独立SNP作为工具变量。使用逆方差加权法与加权中值法进行因果关系分析,并采用MR-Egger和留一法进行模型评价。结果分析结果显示,RA与CAD的总体因果效应是正相关(OR=1.03, 95%CI:1.01～1.04, P=3.90×10-5),RA与正常步行速度负相关(β=-0.02, 9...     

Investigating Causal Associations of Diet-Derived Circulating Antioxidants with the Risk of Digestive System Cancers: A Mendelian Randomization Study

Molecular mechanisms and observational studies have found that diet-derived antioxidants are associated with digestive system cancers, whereas there is a lack of causal evidence from randomized clinical trials. In this study, we aimed to assess the causality of these associations through a Mendelian randomization (MR) study. Single nucleotide polymorphisms of diet-derived circulating antioxidants (i.e., α- and γ-tocopherol, ascorbate, retinol, β-carotene, lycopene, and urate), accessed by absolute levels and relative metabolite concentrations, were used as genetic instruments. Summary statistics for digestive system cancers were obtained from the UK Biobank and FinnGen studies. Two-sample MR analyses were performed in each of the two outcome databases, followed by a meta-analysis. The inverse-variance weighted MR was adopted as the primary analysis. Five additional MR methods (likelihood-based MR, MR-Egger, weighted median, penalized weighted median, and MR-PRESSO) and replicate MR analyses for outcomes from different sources were used as sensitivity analyses. Genetically determined antioxidants were not significantly associated with five digestive system cancers, after correcting for multiple tests. However, we found suggestive evidence that absolute ascorbate levels were negatively associated with colon cancer in UK Biobank—the odds ratio (OR) per unit increase in ascorbate was 0.774 (95% confidence interval [CI] 0.608–0.985, p = 0.037), which was consistent with the results in FinnGen, and the combined OR was 0.764 (95% CI 0.623–0.936, p = 0.010). Likewise, higher absolute retinol levels suggestively reduced the pancreatic cancer risk in FinnGen—the OR per 10% unit increase in ln-transformed retinol was 0.705 (95% CI 0.529–0.940, p = 0.017), which was consistent with the results in UK Biobank and the combined OR was 0.747 (95% CI, 0.584–0.955, p = 0.020). Sensitivity analyses verified the above suggestive evidence. Our findings suggest that higher levels of antioxidants are unlikely to be a causal protective factor for most digestive system cancers, except for the suggestive protective effects of ascorbate on colon cancer and of retinol on pancreatic cancer.     

New proposal to address mediation analysis interrogations by using genetic variants as instrumental variables

The application of causal mediation analysis (CMA) considering the mediation effect of a third variable is increasing in epidemiological studies; however, this requires fitting strong assumptions on confounding bias. To address this limitation, we propose an extension of CMA combining it with Mendelian randomization (MRinCMA). We applied the new approach to analyse the causal effect of obesity and diabetes on pancreatic cancer, considering each factor as potential mediator. To check the performance of MRinCMA under several conditions/scenarios, we used it in different simulated data sets and compared it with structural equation models. For continuous variables, MRinCMA and structural equation models performed similarly, suggesting that both approaches are valid to obtain unbiased estimates. When noncontinuous variables were considered, MRinCMA presented, overall, lower bias than structural equation models. By applying MRinCMA, we did not find any evidence of causality of obesity or diabetes on pancreatic cancer. With this new methodology, researchers would be able to address CMA hypotheses by appropriately accounting for the confounding bias assumption regardless of the conditions used in their studies in different settings.     

基于孟德尔随机化的血脂六项与冠心病因果关系研究

目的 探究血脂六项指标（甘油三酯、总胆固醇、高密度脂蛋白、低密度脂蛋白、载脂蛋白A、载脂蛋白B）与冠心病之间的因果关系,为血脂六项指标与冠心病发病风险关联提供遗传学证据支持。方法 研究采用MR-Egger回归、加权中位数法（weight median estimator, WME）、随机效应逆方差加权法（inverse-variance weighted, IVW）、加权模型4种回归模型对血脂六项指标与冠心病的因果关系进行孟德尔随机化分析。结果 IVW模型显示甘油三酯（OR=1.402）、总胆固醇（OR=1.414）、低密度脂蛋白（OR=1.867）、载脂蛋白B（OR=1.738）为冠心病的危险因素,高密度脂蛋白（OR=0.791）为冠心病的保护因素,IVW模型则显示载脂蛋白A为有统计学意义的影响因素;MR-Egger回归截距项P值均>0.05,即筛选出的SNP不存在基因多效性,因此孟德尔随机化在本研究中为因果推断的有效方法;异质性检验结果P值均<0.001,故应重点关注随机效应IVW模型。结论 利用两样本孟德尔随机化方法排除混杂因素和反向因果关联后,得到无偏估计的结果,据此可以确定甘油三酯、总胆固醇、高密度脂蛋白、低密度脂蛋白、载脂蛋白B与冠心病之间存在因果关系。     

Circulating Proteins Influencing Psychiatric Disease: A Mendelian Randomization Study

BackgroundThere is a pressing need for novel drug targets for psychiatric disorders. Circulating proteins are potential candidates because they are relatively easy to measure and modulate and play important roles in signaling.MethodsWe performed two-sample Mendelian randomization analyses to estimate the associations between circulating protein abundances and risk of 10 psychiatric disorders. Genetic variants associated with 1611 circulating protein abundances identified in 6 large-scale proteomic studies were used as genetic instruments. Effects of the circulating proteins on psychiatric disorders were estimated by Wald ratio or inverse variance–weighted ratio tests. Horizontal pleiotropy, colocalization, and protein-altering effects were examined to validate the assumptions of Mendelian randomization.ResultsNine circulating protein-to-disease associations withstood multiple sensitivity analyses. Among them, 2 circulating proteins had associations replicated in 3 proteomic studies. A 1 standard deviation increase in the genetically predicted circulating TIMP4 level was associated with a reduced risk of anorexia nervosa (minimum odds ratio [OR] = 0.83; 95% CI, 0.76–0.91) and bipolar disorder (minimum OR = 0.88; 95% CI, 0.82–0.94). A 1 standard deviation increase in the genetically predicted circulating ESAM level was associated with an increased risk of schizophrenia (maximum OR = 1.32; 95% CI, 1.22–1.43). In addition, 58 suggestive protein-to-disease associations warrant validation with observational or experimental evidence. For instance, a 1 standard deviation increase in the ERLEC1-201-to-ERLEC1-202 splice variant ratio was associated with a reduced risk of schizophrenia (OR = 0.94; 95% CI, 0.90–0.97).ConclusionsPrioritized circulating proteins appear to influence the risk of psychiatric disease and may be explored as intervention targets.