Abstract

Introduction: Ghrelin is a gut hormone predominantly produced by the stomach and, to a lesser extent, by other regions of the gastrointestinal tract. Ghrelin circulates in the bloodstream in two different forms: acylated (or n-octanoylated) and unacylated (or des-octanoylated or des-acylated). The purpose of this study was to examine the effect of 12 weeks training on plasma acylated ghrelin concentrations and gastrocnemius muscle mRNA expression in male rats. Materials & Methods: Twenty adult Wistar male rats (8 weeks old, 280±20 g) were used. Animals were randomly divided into experimental (EX, n = 10, V=34m/min) and control (n=10) groups. Training groups were given exercise on a motor-driven treadmill (0% grade, 60min, and 5 days/week for 12 weeks). Gastrocnemius was excised and frozen in liquid nitrogen for extraction of ghrelin mRNA and plasma acylated ghrelin, were measured. Results: Plasma acylated ghrelin was significantly (P<0.01) higher in high intensity trained rats. Also muscle mRNA expression was higher in trained rats compared to control rats. Conclusion: Data indicate that higher ghrelin mRNA expression in muscle and higher plasma acylated ghrelin levels could be attributed to metabolic changes (muscle glycogen and ATP depletion are less in endurance trained species). A higher plasma acylated ghrelin in the present study might be attributed to liver and skeletal muscle glycogen and ATP deficiency and incomplete energy sources recovery after the last exercise session along with overnight fast. Lower muscle glycogen levels, as we observed in the present study, might be considered as stimuli for this elevated plasma acylated ghrelin in trained rats.