Purpose: This study was designed to evaluate whether a 4-month endurance training program could improve ANP- as well as isoproterenol-mediated (beta-adrenergic receptor agonist) in situ lipolysis and adipose tissue blood flow (ATBF) in the subcutaneous adipose tissue (SCAT) of untrained overweight subjects.
Methods: Ten overweight men aged 26.0 +/- 1.4 yr with a mean body mass index of 27.6 +/- 0.2 kg.m(-2), performed aerobic exercise 5 d.wk(-1) for 4 months. Before and after the training period, SCAT responsiveness was investigated in situ during a 60-min infusion of 1 micromol.L(-1) isoproterenol and 10 micromol.L(-1) ANP through microdialysis probes. Plasma metabolic parameters and physical fitness variables were measured as well.
Results: Endurance training significantly increased fat-free mass and VO2max, while reducing plasma insulin, glucose, NEFA, low density lipoprotein (LDL)-C and the respiratory exchange ratio at rest. Training significantly lowered resting dialysate glycerol levels in SCAT. The lipid-mobilizing effect of ANP was markedly enhanced (by 191%, P < 0.05) after training as was that of isoproterenol (by 145%, P < 0.05). Resting adipose tissue blood flow as well as ANP- and isoproterenol-mediated rise in ATBF was increased after training.
Conclusion: The present study shows that endurance training improves ANP- as well as beta-adrenergic-receptor-mediated lipid mobilization and ATBF in the SCAT of overweight subjects. The recovery of a higher lipolytic efficiency in adipose tissue is an important benefit of a training program in overweight subjects.