Abstract: Objective: To investigate the relationship between Irisinincduced by endurance training and FTO expression in fatty tissue in high fat diet-induced obese rats.Methods:Themale SDrats were randomly divided into control, high fat diet group, high fat diet plus exercise group and exercise group.Exercisewas performed on a treadmill, keeping 8.2 m/min at 0% grade corresponding to 53% of maximal oxygen uptake ,for 15,30 , 45 and 60 min for the first,second and third time.Thereafter,exercise intensity and duration were maintained until the end of the eighth week. The rats were exercised for 5 days a week.It analysised the body weight, fat mass, blood Irisin level, FNDC5 expression in skeletal muscle and expressions of FTO and UCP1 in fatty tissue after 8 week treadmill training. Results: High fat diet significantly induced body weight and fat mass increase, blood Irisin level decrease, FNDC5 expression decline in skeletal muscle and FTO expression increase and UCP1 expression decrease in fatty tissue in rats. Endurance training can markedly decrease high fat diet-induced body weight and fat mass increase, increase hight fat diet-induced blood Irisin level decline, promote high fat diet-induced FNDC5 down-regulated expression in skeletal muscle and reduce high fat diet-induced FTO up-regulated expression but increase down-regulated UCP1 expression in fatty tissue. Blood Irisin level was negatively correlated to FTOmRAN and protein significantly in fat tissue in high fat diet, high fat diet plus exercise and exercise groups. FNDC5mRNA and protein in skeletal muscle were markedly negatively correlated to FTOmRNA and protein in fatty tissue respectively in high fat diet group and high fat diet plus exercise group. FNDC5mRNA in skeletal muscle was negatively correlated to FTOmRNA but no significance, however, FNDC5 protein was markedly negatively correlated with FTO protein in exercise group.Conclusion: Endrance training may be induce Irisin release increase, which inhibit FTO expression and then enhance UCP1 expression in fatty tissuein rats.

Key words: Endurance Training, Obesity, FibronectinType III Domain Containingprotein 5, FatMass and Obesity-Associated Protein Gene, Rats