Endocrine Abstracts

Objectives: Growing interest has been focused on the role of atrial natriuretic peptide (ANP) in the protection of cardiac and vascular integrity. Moreover, ANP enhances lipolysis and fat-oxidation. However, the impact of exercise on ANP in obesity is not yet investigated. The aim of this study was to evaluate the modulation of exercise-induced changes in ANP in obesity.

Methods: We studied the hormonal and metabolic responses to 30 min exercise on cyclo-ergometer at a self-selected intensity in 12 obese healthy subjects (OS) (6males; BMI 33.9±1.6 kg/m²) and 13 lean controls (LC) (6males; 21.6±0.5 kg/m²).

Blood samples were collected every 15 min: before, during exercise and for 90 minutes thereafter. Heart rate (HR) was monitored and plasma MR-proANP_53–90 was measured using a chemiluminescence assay.

Results: All the subjects concluded the 30 minutes of exercise at an average peak intensity of 138.4±42.6 W (85.2±10.8% of subjects’ HRmax.) that were comparable between groups (P>0.05).

Exercise significantly increased ANP levels in both study groups (P<0.01). However, the ANP response was more pronounced in LC as compared to OS (proANP-AUC120: 131.8±5.3 (OS) vs 151.8±5.9 (LC); P<0.01]. Similarly, the exercise-induced stimulation of lipolysis was diminished in obese subjects (P<0.01).

Conclusions: This study demonstrates that the ANP responsiveness to exercise is reduced in obesity. The mechanisms underlying differential regulation of ANP in obesity and the role of ANP in mediating the exercise-induced lipolysis needs further investigations.