Effects of A 4-Week Aerobic Exercise on Lipid Profile and Expression of LXRα in Rat Liver

OBJECTIVE: Liver X receptors (LXRs) are ligand-activated transcription factors of the nuclear hormonal receptor superfamily which modulate the expression of genes involved in cholesterol homeostasis. Hence, further unraveling of the molecular function of this gene may be helpful in preventing cardiovascular diseases. MATERIALS AND METHODS: This experimental intervention study included twelve adult Wistar male rats (12-14 weeks old, 200-220 g) which were divided into the control (n=6) and training (n=6) groups. The training group received exercise on a motor-driven treadmill at 28 meters/minute (0% grade) for 60 minutes a day, 5 days a week for 4 weeks. Rats were sacrificed 24 hours after the last session of exercise. A portion of the liver was excised, immediately washed in ice-cold saline and frozen in liquid nitrogen for extraction of total RNA. Plasma was collected for high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC) and triglycerides (TG) measurements. All variables were compared by independent t test. RESULTS: A significant increase in LXRα transcript level was observed in trained rats (P<0.01). Plasma HDL-C concentration was also significantly higher (P<0.01) in trained rats. There was a significant decrease in the concentrations of LDL-C (P<0.01) and TC (P<0.02), and the ratios of TC/HDL-C (P<0.001) and LDL/HDL-C (P<0.002) in trained rats. However, the TG concentration was unchanged (P>0.05). CONCLUSION: We found that endurance training induces significant elevation in LXRα gene expression and plasma HDL-C concentration resulting in depletion of the cellular cholesterol. Therefore, it seems that a contributor to the positive effects of exercise in cardiovascular disease prevention is through the expression of LXRα, which is a key step in reverse cholesterol transport.