Association Between Plasma Cystatin C And Cardiovascular Events:Mendelian Randomization Analyses

ObjectivesCystatin C was significantly associated with cardiovascular disease(CVD)and death risk,but causal inferences have not been confirmed.We aimed to analyze the relationship between plasma cystatin C and the risk of CVD and CVD mortality,based on the large follow-up cohort UK Biobank.To avoid the effects of confounding factors and reverse causal associations,Mendelian Randomization(MR)was futher used to assess the causal association between plasma cystatin C and the risk of CVD and mortality.MethodsOur study included 305874 individuals free of CVDs or cancer at baseline.Cox proportional hazard model was used to evaluate hazard ratios(HR)and confidence interval(95%CI)for the risk of CVDs[stroke,myocardial infarction(MI),and coronary heart disease(CHD)]and CVD mortality.Cox proportional hazards model with restricted cubic splines was used to assess the dose-response relationship between cystatin C level and the risk of CVD and CVD mortality,further confirming the nonlinear relationships.Stratified analysis and sensitivity analysis further test the robustness of the observed associations.Mendelian randomization study was used to further evaluate the causal relationship,further excluded the samples lacking genotyping data,and finally included 268244 subjects.According to the large genome-wide association study,28 single nucleotide polymorphism(SNPs)related to cystatin C were selected as genetic instrument variable.We created the genetic risk score(GRS)for the cystatin C separately using 28 SNPs.Linear MR used the two-stage least squares method to evaluate the causal effect value of cystatin C and CVD and CVD mortality risk for each increase of 1-SD.In addition,inverse variance weighted(IVW),weighted median(WM,MR-Egger regression,MR pleiotropy residual sum and outlier(MR-PRESSO)were used for further analysis.Through the weak instrumental variable and the multiple validity test,explore whether the instrumental variable meets the conditions,and construct a new instrumental variable after removing the multiple validity SNP,and then conducted the sensitivity analysis.Results1.A total of 305874 subjects were included in the study,with median follow-up time of 12.65 years.The following events and deaths were recorded:17716 all cause deaths(including 3301 deaths from CVD)and 26723 incident CVD events.The Cox proportional regression model showed that the increased level of cystatin C was associated with the risk of CVD and CVD mortality.Participants were divided into five groups Q1(<0.78mg/L),Q2(0.78-0.85mg/L),Q(0.85-0.92mg/L),Q4(0.92-1.00mg/L)and Q5(>1.00mg/L)according to quintile of Cystatin C.Compared with Q1,the HR(95%CI)of Q5 was 1.37(1.30-1.44),P-trend<0.001;The HR of stroke risk was 1.50(1.35-1.67),P-trend<0.001;The HR of MI risk was 1.62(1.47-1.78),P-trend<0.001;The HR of CHD risk was 1.35(1.27-1.43),Ptrend<0.001;The HR of all-cause death risk was 1.44(1.35-1.53),P-trend<0.001;The HR of CVD mortality was 1.73(1.48-2.03),P-trend<0.001;The HR of all-cause mortality was 1.44(1.35-1.53),P-trend<0.001.The results of restricted cubic spline showed that there were linear relationships between plasma cystatin C and the risk of CVD(stroke,CHD)and CVD mortality.There was non-linear correlation between plasma cystatin C and the risk of MI and all-cause mortality(P-nonlinear<0.05).We found that the level of cystatin C with a strong positively association with MI and all-cause mortality at concentrations of cystatin C>1.02mg/L.Sensitivity analysis showed that plasma cystatin C was consistent with the related results of incident CVD,stroke,MI,CHD,and CVD mortality.2.The linear MR showed that every SD increase of cystatin C had no significant difference with incident CVD(HR=0.97,95%CI:0.78-1.22),stroke(HR=0.97,95%CI:0.61-1.55),MI(HR=0.96,95%CI:0.64-1.45),CHD(HR=0.98,95%CI:0.76-1.26)and CVD mortality risk(HR=1.04,95%CI:0.54-2.00).Nonlinear MR indicated that different grades of GRS were not associated with the risk of CVD and CVD mortality.IVW method showed no causal role of genetically predicted plasma cystatin C in CVDs(OR=1.03,95%CI:0.89-1.19),stroke(OR=1.01,95%CI:0.75-1.35),MI(OR=1.02,95%CI:0.79-1.31),CAD(OR=1.02,95%CI:0.87-1.21)and CVD mortality risk(OR=0.99,95%CI:0.64-1.51).The results of weighted median method,Egger regression method and MRPRESSO method are consistent with IVW method.ConclusionStudies have shown that higher plasma cystatin C was associated with the risk of CVD(stroke,MI,CHD),all-cause mortality,and CVD mortality.There was linear dose-response relationships between plasma cystatin C and the risk of CVD and CVD mortality,and nonlinear dose-response relationship with the risk of all-cause mortality.However,Mendel randomization study did not confirm the causal relationships between plasma cystatin C and CVD and CVD mortality.