Effects of endurance training under hyperoxia on serum and tissue lipid levels in rats

Effects of 6 weeks endurance training (5 days per week) under hyperoxia (60% O2 plus 40% N2) on serum and tissue lipid levels were investigated in male rats. Rats were divided into 4 groups: normoxia-control (NC), hyperoxia-control (HC), normoxia-training (NT), and hyperoxia-training (HT). NT and HT groups were run on a treadmill in a chamber at 20 m per min with a 6 degree gradient for 30 min. The chamber was perfused with hyperoxic gas. After training under hyperoxia, high density lipoprotein cholesterol (HDL-C) was higher (p less than 0.01) than in the normoxic condition, but there were no changes in serum lipids and glucose, or liver and aorta cholesterol. Skeletal muscle TG and liver glycogen in hyperoxic condition tended to show the higher values. Basal lipolysis of adipose tissue was increased (p less than 0.05) by hyperoxia, and decreased (p less than 0.01) by training, but there was no change of norepinephrine induced lipolysis in any group. The results suggest that endurance training or resting under hyperoxia induces increased HDL-C or lipolytic activity of adipose tissue. These effects might be caused by greater fat oxidation during exercising or resting under hyperoxia.