Association of apelin and apelin receptor with the risk of coronary artery disease: a meta-analysis of observational studies

It is well established that apelin-APLNR (apelin receptor) pathway plays a central role in cardiovascular system. In this meta-analysis, we summarized published results on circulating apelin concentration in association with coronary artery disease (CAD), apelin and APLNR genetic polymorphism(s) in predisposition to CAD risk and circulating apelin changes after surgical treatment for CAD. The results from 15 articles were pooled. Two authors independently took charge of literature search, article selection and information collection. Overall, circulating apelin concentration was significantly lower in CAD patients (N=1021) than in controls (N=654) (weighted mean difference [WMD]: -1.285 ng/mL, 95% confidence interval [CI]: -1.790 to -0.780, P<0001), with significant heterogeneity (I(2)=99.3%) but without publication bias. For the association of APLNR gene rs9943582 polymorphism with CAD (patients/controls: 5975/4717), the mutant T allele was associated with a 5.2% increased risk relative to the wild C allele (odds ratio: 1.052, 95% CI: 0.990 to 1.117, P=0.100), without heterogeneity (I(2)=0.0%) or publication bias. Circulating apelin was increased significantly after surgical treatment for CAD (N=202) (WMD: 2.011 ng/mL, 95% CI: 0.541 to 3.481, P=0.007), with significant heterogeneity (I(2)=98.0%). Stratified analyses showed that circulating apelin was significantly reduced in studies with age- and sex-matched patients and controls (WMD: -1.881 ng/mL, 95% CI: -2.457 to -1.304, P<0.001) and with total sample size ≥125 (WMD: -1.657 ng/mL, 95% CI: -2.378 to -0.936, P<0.001), relative to studies without matching reports and with total sample size <125. In brief, our results suggested that circulating apelin was a prominent athero-protective marker against the development of CAD.