Treadmill training enhances rat agouti-related protein in plasma and reduces ghrelin levels in plasma and soleus muscle.

Ghrelin and agouti-related protein (AgRP) are orexigenic peptides secreted from stomach mucosa and the arcuate nucleus of the hypothalamus, respectively. Both peptides affect feeding behavior and play a role in energy balance, glucose homeostasis, and adiposity. The purpose of the current study was to determine the effects of moderate-term (6 weeks) running regimen on resting levels of ghrelin, AgRP, adenosine triphosphate, and glycogen in soleus muscle as well as plasma concentrations of the orexigenic hormones. Eighteen adult Wistar male rats (12 weeks old, 235-255 g) were randomly assigned to training (n = 10) and control (n = 8) groups. The training group ran for 60 min/d, 5d/wk at 25 m/min and 0% grade for 6 weeks. Forty-eight hours after the last exercise session, rats were killed; and soleus muscle and plasma were collected and frozen in liquid nitrogen for later analysis. Results demonstrated that 6 weeks of treadmill exercise reduced ghrelin and increased AgRP levels in plasma. Trained rat soleus muscle had higher levels of glycogen but not adenosine triphosphate or AgRP compared with untrained controls. Data indicate that training lowers ghrelin levels in rat soleus and plasma, which is accompanied by higher plasma AgRP and soleus glycogen content.