EXERCISE TRAINING DOWN-REGULATES HEPATIC LIPOGENIC ENZYMES IN MEAL-FED RATS - FRUCTOSE VERSUS COMPLEX-CARBOHYDRATE DIETS

The maximal activity and mRNA abundance of hepatic fatty acid synthase (FAS) and other lipogenic enzymes were investigated in rats meal-fed either a high fructose (F) or a high cornstarch (C) diet. The diet con tained 50% F or C (g/100 g), casein (20%), cornstarch (16.13%), corn o il (5%), minerals (5.37%), vitamins (1%) and Solka-floc (2%). Female S prague-Dawley rats (n = 44) were randomly divided into C or F groups t hat were meal-fed for 3 h/d; each group was subdivided into exercise-t rained (T) and untrained (U) groups. Treadmill training was performed 4 h after the initiation of the meal at 25 m/min, 10% grade for 2 h/d, 5 d/wk, for 10 wk, Rats were killed 9 h after the meal and 27 h after the last training session. F-fed rats had significantly higher activi ties of all lipogenic enzymes assayed and mRNA abundance of FAS and ac etyl-coenzyme A carboxylase (ACC) than C mts (P < 0.05). Concentration s of plasma insulin and glucose and liver pyruvate were not altered by F feeding. Proportions of the fatty acids 18:2 and 20:4 were lower, w hereas those of 16:0 and 16:1 were higher, in livers of F than of C ra ts (P < 0.05). Training decreased FAS activity by 50% (P < 0.05), with out affecting FAS mRNA level in C rats; this down-regulation was absen t in the F rats. ACC mRNA abundance tended to be lower in CT than in C U rats (P < 0.075), L-Type pyruvate kinase activity was lower in FT th an in FU rats (P < 0.05), whereas other lipogenic enzyme activities di d not differ between T and U rats of each diet group, We conclude that hepatic lipogenic enzyme induction by high carbohydrate meal feeding may be inhibited by exercise training and that a fructose-rich diet ma y attenuate this training-induced down-regulation.