We investigated the effects of habitual exercise and diet restriction on the hepatic fat accumulation in Zucker fatty rats. Male 6-week-old Zucker fatty rats were divided into obese (Ob), diet restriction (DR), and diet restriction + exercise (DR + Ex) groups. Male Zucker lean rats (L) were used as a control group. The rats in the L and Ob groups were maintained on ad libitum diets. The rats in the DR and DR + Ex groups were fed a 30% restricted diet. The rats in the DR + Ex group exercised voluntarily on a wheel ergometer. After 6 weeks of intervention, the serum free fatty acid and leptin levels in the Ob group were significantly higher than those in the L group. In the Ob group, the hepatic triglyceride content was higher than that in the L group and hepatocyte fat infiltration was observed on haematoxylin and eosin staining. These changes were suppressed by DR + Ex, but not by the DR intervention. These results suggest that habitual exercise inhibits fat accumulation in the liver of Zucker fatty rats.

The authors have found that compulsory training using treadmill running increases pancreatic weight, protein content, and enzyme activity in hypertrophied acinar cells in rats. The purpose of the present study was to investigate the effect of voluntary running exerise on the exocrine pancreas in rats. Female F344 rats were divided into control, compulsory training, and voluntary training groups. The compulsory trained rats were exercised for 60 min on a treadmill (final speed, 35 m/min), 5 days a week, for 8 weeks. The voluntary trained rats were exercised on a voluntary basis on a wheel ergometer with a load of 30% of their body weight every day. Mean running distance for the voluntary training group was 5.2±1.0 km/day. Final body weight for the compulsory and voluntary training groups was significantly lower than for the control group. Soleus muscle weight and citrate synthase activity of the plantaris muscle for the compulsory and voluntary training groups were significantly higher than for the control group. Pancreatic wet weight, protein content, and amylase and lipase activities for the compulsory and voluntary training groups were significantly higher than for the control group. Pancreatic wet weight, protein content, and amylase and lipase activities for the compulsory and voluntary training groups were significantly higher than for the control group. Total DNA content of whole pancreas in the voluntary training group was significantly higher than for the control and compulsory training groups. Electron micrographs revealed that acinar cells obviously hypertrophied and zymogen granules increased in the compulsory and voluntary training groups rats compared with the compulsory group. These results suggest that voluntary training increases pancreatic weight and protein content in hypertrophied and/or hyperplasic acinar cells, which in turn increases synthesis and the storage of exocrine pancreatic enzymes.