Assessment of Apelin Serum Levels in Persistent Atrial Fibrillation and Coronary Artery Disease

Background: Apelin, the endogenous ligand of orphan receptor APJ (gene symbol APLNR), is an adipokine that was suggested to have a direct correlation with obesity. This peptide might play a role in obesity-related disorders, especially in the cardiovascular system. Currently, few data are available on levels and potential metabolic functions of apelin in different cardiac diseases including atrial fibrillation (AF) and coronary artery disease (CAD), which have common underlying pathophysiological mechanisms. This study aimed to investigate apelin levels in patients with AF and CAD that were overweight or obese, as well as its relationship with anthropometry and metabolic profile. Methods: This preliminary investigation was compromised of 41 patients with AF and 39 with CAD aged > 50 years and body mass index (BMI) > 25 kg/m(2). Serum levels of apelin, fasting plasma glucose, insulin, homeostatic model assessment, triglyceride, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol and very-low-density lipoprotein were measured. Results: The apelin serum levels were not statistically different between patients with AF and CAD. A negative correlation was observed between apelin with weight (r = 0.257, P = 0.023) and BMI (r = 0.258, P = 0.023). Moreover, apelin showed an inverse correlation with insulin (r =-0.227, P = 0.045) and marginally with homeostatic model assessment (r = 0.21, P = 0.066). There was a negative association between apelin and triglyceride (r = 0.238, P = 0.036) and very-low-density lipoprotein (r = 0.25, P = 0.027). Conclusions: Apelin serum levels were not significantly different among patients with AF and CAD. The unexpected inverse correlation of apelin with weight and BMI might indicate the dominant effects of pathophysiological conditions such as AF and CAD on serum levels of apelin compared with BMI and adipose tissue. Understanding the precise role of apelin in modulating obesity-induced disorders including AF and CAD requires further studies.