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 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.
Fiebig
R
R
Departments of Kinesiology and Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Griffiths
M A
MA
Gore
M T
MT
Baker
D H
DH
Oscai
L
L
Ney
D M
DM
Ji
L L
LL
D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000502:physiology; D002950:Citrate (si)-Synthase / Q000378:metabolism; D015331:Cohort Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D015536:Down-Regulation; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000032:analysis / Q000145:classification; D005260:Female; D005632:Fructose / Q000008:administration & dosage; D008099:Liver / Q000737:chemistry / Q000201:enzymology* / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology; D009929:Organ Size / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D011770:Pyruvate Kinase / Q000378:metabolism; D019289:Pyruvic Acid / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013213:Starch / Q000008:administration & dosage
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005227:Fatty Acids; D012333:RNA, Messenger; D005632:Fructose; D019289:Pyruvic Acid; D013213:Starch; D064429:Fatty Acid Synthases; D002950:Citrate (si)-Synthase; D011770:Pyruvate Kinase; D000103:Acetyl-CoA Carboxylase