Paradoxical Clearance of Natriuretic Peptide between Pulmonary and Systemic Circulation: A Pulmonary Mechanism of Maintaining Natriuretic Peptide Plasma Concentration in Obese Individuals

Abstract

Although it has been reported that obese patients have low levels of natriuretic peptide, the metabolism of natriuretic peptide in this population remains unclear. This study aimed to examine the effects of body mass index on the natriuretic peptide clearance rate from the pulmonary and systemic circulation. We conducted a prospective observational cohort study. Thirty patients with atrial fibrillation undergoing pulmonary vein isolation in single center participated in the study. We measured pulmonary and systemic atrial/brain natriuretic peptide clearance and clinical parameters including body mass index and pulmonary oxygen levels. Significantly lower atrial natriuretic peptide levels were found in all pulmonary veins when compared with the pulmonary artery. The pulmonary atrial natriuretic peptide clearance rate was negatively correlated with body mass index. In contrast, the systemic atrial natriuretic peptide clearance rate was positively correlated with the body mass index. A reciprocal relationship therefore exists between pulmonary and systemic atrial natriuretic peptide clearance. Regional pulmonary atrial natriuretic peptide clearances in the inferior lung were significantly negatively correlated to oxygen pressure in the inferior pulmonary veins. There was a similar tendency for brain natriuretic peptide, but the differences between the pulmonary artery and each pulmonary vein were not significant. Overweight patients have higher systemic atrial natriuretic peptide clearance, whereas they show a lower pulmonary atrial natriuretic peptide clearance, which might be related to pulmonary tissue hypoxia.