Lowered circulating apelin is significantly associated with an increased risk for hypertension: A meta-analysis

Background and Objective: Apelin is a bioactive peptide manifesting a potent vasodilatory property. In this meta-analysis, we aimed to investigate for the first time whether circulating apelin differed significantly between hypertensive patients and normotensive controls. Methods: Both PubMed and Embase were searched for eligible articles. Eligibility evaluation and data collection were done independently by two investigators. Weighted mean difference (WMD) with 95% confidence interval (CI) was calculated under random-effects model by STATA. Results: Ten studies were synthesized finally, including 1610 patients and 1105 controls. Overall analysis revealed that circulating apelin was significantly lowered in patients than in controls (WMD = −39.85 pg/mL, 95% CI: −65.56 to −14.15; P = 0.002), with significant heterogeneity (I2 = 89.4%). By race, patients had lower circulating apelin than controls in Caucasian populations (WMD = −79.82 pg/mL, 95% CI: −105.80 to −53.85; P < 0.001), without heterogeneity (I2=0.0%), while no significance was observed in Chinese and African-Americans. Further grouping studies by source of controls found a significant reduction in circulating apelin in studies with hospital-based controls (WMD = −96.28 pg/mL, 95% CI: −129.67 to −62.88; P < 0.001) (I2 = 49.4%), but not in studies with population-based controls. Conclusions: Via a meta-analysis of 10 studies and on 2715 subjects, our findings demonstrated that lowered circulating apelin was significantly associated with an increased risk for hypertension, especially in Caucasian populations.