Plasma apelin levels in pulmonary arterial hypertension: a potential early diagnostic biomarker?

Background/Introduction Pulmonary arterial hypertension (PAH) is a progressive disorder characterized by pulmonary vasoconstriction, vascular remodeling, impaired angiogenesis, and right ventricular dysfunction. Despite advances in treatment, biomarkers that may support diagnosis and reflect disease burden remain limited. Apelin is an endogenous peptide that acts through the APJ receptor and modulates vascular tone, endothelial function, nitric oxide-mediated vasodilation, and the renin-angiotensin system. These properties suggest a potential role for apelin in the pathobiology and clinical evaluation of PAH. Purpose To investigate whether circulating apelin levels are associated with the presence of PAH and to assess their relationship with clinical severity and risk stratification. Methods Forty patients with PAH and 40 age-matched healthy controls were included. All participants underwent transthoracic echocardiographic evaluation, six-minute walk testing, and apelin measurement. Patients with PAH were additionally categorized according to the European Society of Cardiology four-strata risk model and World Health Organization functional class. Comparisons were performed between groups and across risk categories, and multivariable logistic regression analysis was used to determine whether apelin was independently associated with PAH. Results Apelin levels were significantly higher in patients with PAH than in healthy controls (1006.20 ± 312.99 pg/mL vs. 812.46 ± 245.80 pg/mL; p = 0.003). This elevation was observed across PAH subtypes, without significant differences among ESC risk groups (p = 0.24) or World Health Organization functional classes (p = 0.06). In multivariable logistic regression analysis, apelin remained independently associated with the presence of PAH (odds ratio 1.003, 95% confidence interval 1.001-1.005; p = 0.007). Conclusion(s) Circulating apelin levels are elevated in PAH and may provide supportive diagnostic information in the clinical assessment of this condition. However, apelin does not appear to adequately discriminate disease severity, functional status, or risk category. These findings suggest that apelin may be more useful as a diagnostic adjunct than as a marker of risk stratification in PAH.