Effects of exercise training on diet-induced lipogenic enzymes and body composition in rats

It is well known that a carbohydrate-rich diet promotes lipogenesis via induction of hepatic lipogenic enzymes, whereas chronic physical exercise reduces body fat. The purpose of this study was to investigate whether exercise training can decrease diet-induced hepatic lipogenic enzymes and total body fat composition. Female Sprague-Dawley rats were randomly divided into exercise trained (T) and sedentary (S) groups. Training was performed on a treadmill for 8 weeks for up to 25 m/minute, 15% grade for 90 minutes/day, 5 days/week. The T and S groups were further divided into four dietary treatments. Fifty percent of the calories for each diet were from a basal ingredient and the other 50% were from either cornstarch (C), glucose (G), fructose (Fr), or fat (Fa). T significantly decreased body fat and increased body water content in all dietary groups (p < 0.01), but had no effect on body weight. Fr rats had significantly heavier liver weight than did the remaining groups. Activities of hepatic fatty acid synthase, ATP-citrate lyase (CL), malic enzyme (ME), pyruvate kinase, and glucose-6-phosphate dehydrogenase were significantly higher in Fr and lower in Fa compared with C and G. Training significantly increased activities of CL and ME in Fa, but had little effect on these enzymes in other groups. These data suggest that the fat-reducing effect of conventional exercise training is elicited by regulatory mechanisms other than by a reduction of hepatic lipogenic enzymes.