Effects of acute and chronic exercise on the activities of hepatic lipogenic enzymes in rats

Abstract

Effects of acute exercise and chronic exercise training on activities of five hepatic lipogenic enzymes were studied in rats fed different high-carbohydrate diets. In Study 1, ATP citrate lyase (CL), pyruvate kinase (PK), and fatty acid synthase (FAS) activities were greater in rats fed a high-fructose diet than in rats fed high-glucose or high-cornstarch diets. Exercise decreased CL, PK, FAS, and glucose-6-phosphate dehydrogenase (G6PDH) activities, especially in fructose-fed rats. Study 2 examined the time course of dietary induction of enzymes in fasted/refed rats, and the inhibitory effect of exhaustive exercise on induction. Fasting suppressed all activities to minimal levels. FAS and PK activities increased between 4 and 8 hours of refeeding, then plateaued and were greater in fructose versus cornstarch rats. Activities of malic enzyme, CL, and G6PDH peaked after 48 hours; fructose-fed rats had higher activities than cornstarch-fed rats. Exercise inhibited activities of FAS, PK, and G6PDH, especially in fructose-fed rats. Study 3 investigated whether chronic exercise training would prevent dietary-induction of FAS and PK. Activities of all enzymes were two times greater in fructose-fed versus cornstarch-fed rats. Cornstarch-fed rats showed significantly lower FAS activity with training; fructose-fed rats had significantly lower PK activity after training.