Time-Course Alterations of Plasma and Soleus Agouti-Related Peptide and Relationship to ATP, Glycogen, Cortisol, and Insulin Concentrations Following Treadmill Training Programs in Male Rats

Abstract

No studies have examined the time-course changes of the appetite stimulating hormone, agouti-related peptide (AgRP), induced by exercise training. The purpose of the study was to determine the effects of short (3 weeks), moderate (9 weeks), and long-term (12 weeks) treadmill training on plasma and soleus concentrations of AgRP, as well as ATP and glycogen concentrations in soleus muscle and liver tissues. 54 Wistar male rats were randomly assigned into control (total n=27; 3 week control=10; 9 week control=8; 12 week control=9) and training (total n=27; 3 week trained=10; 9 week trained=8; 12 week trained=9). The training groups ran for 60 min/d, 5 d/wk at 25 m/min and 0% grade for 3, 9, and 12 weeks. After the last exercise session soleus muscle, liver, and plasma were collected and frozen. Results demonstrated that after 3, 9, and 12 weeks of exercise training there was an increase in plasma and soleus AgRP that declined with age. Soleus muscle glycogen was inversely related to AgRP. After 9 weeks of training there was a significant decrease and increase in plasma insulin and cortisol, respectively. Thus, as little as 3 weeks of running enhances AgRP concentration in rat soleus and plasma whereas changes in liver ATP and glycogen and soleus muscle glycogen require 9 weeks for alteration. Plasma and soleus muscle AgRP decline with age, and AgRP concentration in plasma and soleus are related to insulin, soleus ATP, and liver glycogen.