Early Exercise Persisted Attenuation of Obesity, Hypertriglycemia, and Hepatic Steatosis in Obese Diabetic OLETF Rat

초록

Aerobic exercise is a key component for the prevention and clinical management of type 2 diabetes mellitus and fatty liver. Interestingly, previous studies showed that although short-term exercise training improved insulin signaling in skeletal muscle in young men, these changes did not occur in middle-aged men. In this study, the differential effects of aerobic exercise done at different aging points on metabolic parameters, inflammatory cytokine level and fatty change in liver were investigated in obese diabetic animal model. We evaluated the early (from 12 weeks old to 26 weeks old), late (from 26 weeks old to 40 weeks old) and continuous (from 12 weeks old to 40 weeks old) effects of aerobic exercise (15 m/min and 60 min/day) on body weight and composition, lipid profiles and morphological change of liver in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. Decreased total body mass, increased lean body mass, and decreased fat mass were observed in all exercise groups. More significant improvement of oral glucose tolerance was observed in the continuous exercise group compared with early and late exercise (each group, n=10). Early exercise showed delayed beneficial effects on body weight and glucose tolerance which persisted throughout even without exercise at later stages. The decreased changes of lipid profiles in triglyceride and free fatty acid were observed in early and late exercise groups and more significant decrease in triglyceride was observed in the continuous exercise group. The plasma levels of cytokine IL-10 showed more significant increase in continuous exercise groups compared with early exercise. Furthermore, both early and late exercise exhibited significantly reduced large lipid vacuole filling in the cytoplasm and reduced lipid droplet size compared with OLETF control group. Although not delivered continuously, both early and late exercise showed improved glucose tolerance. Furthermore, both early and continuous exercise can maintain the benefi