Weight Loss by Diet Versus Metabolic Surgery Increases Circulating NT-proANP in Obese Individuals

Background: Natriuretic peptides are endocrine factors that regulate various physiological processes via natriuretic peptide receptors (NPRs). Regulation of the atrial natriuretic peptide ANP during weight loss remains widely unknown. The present study investigated serum quantities of the circulating ANP precursor NT-proANP in obesity and during therapy-induced weight loss. Methods: The study enrolled 284 severely obese individuals. A total of 163 patients underwent metabolic surgery (either Roux-en-Y gastric bypass or vertical sleeve gastrectomy) and 121 patients participated in a non-invasive obesity therapy applying low-calorie formula diet. Anthropometric and physiological data were assessed, and blood serum was prepared at study baseline and at follow-up visits (3 and 12 months after start of intervention). Subcutaneous and visceral adipose tissue specimen were obtained from metabolic surgery patients. Circulating NT-proANP levels were determined by ELISA and gene expression levels of the receptor NPRA in adipose tissue were quantified by real-time RT-PCR. Results: Comparative analysis revealed significantly higher NPRA expression in visceral than in subcutaneous adipose tissue. NT-proANP levels significantly increased during weight loss over 12 months upon diet and metabolic surgery. NT-proANP serum concentrations were positively correlated with fibroblast growth factors 19 and 21 quantities at study baseline and considerably increased during weight loss in both cohorts after 12 months. We conclude that weight loss is a positive regulator of circulating NT-proANP quantities, regardless of the applied therapy.