APLN and chronic kidney disease: In keeping with its inotropic actions, [Pyr1]apelin-13 30 nmol/min increased cardiac index by ~ 10% in both healthy subjects and patients with CKD patients (2.7 ± 0.1 to 3.0 ± 0.1 L/min/m2 and 2.5 ± 0.1 to 2.7 ± 0.2 L/min/m2 respectively, both p < 0.05; Fig. 1C).