Effects of habitual exercise and dietary restriction on intrahepatic and periepididymal fat accumulation in Zucker fatty rats

BACKGROUND: Habitual exercise and dietary restriction are commonly recommended to prevent or ameliorate obesity and lifestyle-related diseases, including fatty liver. This study investigated the effects of habitual exercise and dietary restriction on hepatic triglyceride (TG) levels, serum leptin levels, and histological adipocyte size in periepididymal adipose tissue from Zucker fatty (ZF) rats. METHODS: Six-week-old male ZF rats were randomly assigned to one of three groups: sedentary (Sed), sedentary and dietary restriction (Sed + DR), and training and dietary restriction (Tr + DR). Male Zucker lean (L) rats were used as control animals. All rats had access to water and the allowed quantity of food ad libitum. The rats in the Sed + DR and Tr + DR groups were fed a 30% restricted diet, while those in the Tr + DR group exercised voluntarily on a wheel ergometer. After 12 weeks, the rats were sacrificed for a histological examination of their liver and periepididymal adipose tissue. Hepatic and serum TG, serum total cholesterol, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, free fatty acid, and leptin levels were also measured. RESULTS: The hepatic TG levels were significantly higher in the Sed + DR group than in the L (P < 0.001) and Sed (P < 0.05) groups. By contrast, the hepatic TG levels in the Tr + DR group were significantly lower than those in the Sed (P < 0.05) and Sed + DR (P < 0.001) groups, but not significantly different from the L group values. The periepididymal adipocytes were significantly larger in the Sed, Sed + DR, and Tr + DR groups than in the L group (P < 0.001) and were significantly smaller in the Tr + DR group compared to the Sed and Sed + DR groups (P < 0.001). CONCLUSIONS: Our results suggest a relationship between lipid metabolism and the size of adipose cells in ZF rats. Exercising plays an important role in decreasing hepatic TG levels, serum leptin levels, and the size of adipose cells.