Additionally, circulating levels of apelin are decreased in chronic heart failure (Földes et al., 2003) and in essential and pulmonary hypertension (Sonmez et al., 2010; Chandra et al., 2011), and increased in disease states such as aortic stenosis (Duman et al., 2018), and left ventricular hypertrophy (Helske et al., 2010). This evidence concerns the gene APLN and pulmonary arterial hypertension.