Exercise training down-regulates hepatic lipogenic enzymes in meal-fed rats: fructose versus complex-carbohydrate diets

• Published in: The Journal of nutrition Vol. 128; no. 5; p. 810
• Main Authors: Fiebig, R, Griffiths, M A, Gore, M T, Baker, D H, Oscai, L, Ney, D M, Ji, L L
• Format: Journal Article
• Language: English
• Published: United States 01-05-1998
• Subjects: Acetyl-CoA Carboxylase - genetics; Acetyl-CoA Carboxylase - metabolism; Animals; Blood Glucose - analysis; Body Weight - physiology; Citrate (si)-Synthase - metabolism; Cohort Studies; Dietary Carbohydrates - administration & dosage; Down-Regulation; Fatty Acid Synthases - genetics; Fatty Acid Synthases - metabolism; Fatty Acids - analysis; Fatty Acids - classification; Female; Fructose - administration & dosage; Liver - chemistry; Liver - enzymology; Liver - physiology; Muscle, Skeletal - enzymology; Organ Size - physiology; Physical Conditioning, Animal - physiology; Pyruvate Kinase - metabolism; Pyruvic Acid - analysis; Random Allocation; Rats; Rats, Sprague-Dawley; RNA, Messenger - analysis; RNA, Messenger - genetics; Starch - administration & dosage
• ISSN: 0022-3166
• DOI: 10.1093/jn/128.5.810

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 contained 50% F or C (g/100 g), casein (20%), cornstarch (16.13%), corn oil (5%), minerals (5.37%), vitamins (1%) and Solka-floc (2%). Female Sprague-Dawley rats (n = 44) were randomly divided into C or F groups that were meal-fed for 3 h/d; each group was subdivided into exercise-trained (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 activities of all lipogenic enzymes assayed and mRNA abundance of FAS and acetyl-coenzyme A carboxylase (ACC) than C rats (P < 0.05). Concentrations 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, whereas those of 16:0 and 16:1 were higher, in livers of F than of C rats (P < 0.05). Training decreased FAS activity by 50% (P < 0.05), without affecting FAS mRNA level in C rats; this down-regulation was absent in the F rats. ACC mRNA abundance tended to be lower in CT than in CU rats (P < 0.075). L-Type pyruvate kinase activity was lower in FT than in FU rats (P < 0.05), whereas other lipogenic enzyme activities did 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 may attenuate this training-induced down-regulation.