To shed some light on this issue, we additionally summarized the changes of circulating apelin concentration after surgical treatment for CAD, and our results on the basis of 4 studies revealed that circulating apelin concentration was increased remarkably at the 5th day of post-surgery relative to that before the surgery, which can, at least in part, support a causal role of circulating apelin in the aetiology of CAD. The gene discussed is APLN; the disease is coronary artery disorder.