Lipogenic enzyme activities and mRNA in rat adipose tissue at weaning.
The activities and mRNA concentrations of two lipogenic enzymes, fatty acid synthetase and acetyl-CoA carboxylase, and one enzyme involved in glyceroneogenesis, phosphoenolpyruvate carboxykinase (PEPCK), were measured in rat white adipose tissue during the suckling-weaning transition. Activities and mRNA concentrations of lipogenic enzymes were low in suckling rats, whereas activity and mRNA concentration of PEPCK were high. At weaning to a high-carbohydrate diet, the rapid increase in lipogenic enzymes mRNA (10- to 20-fold) and decrease in PEPCK mRNA (10-fold) were followed by parallel changes in enzyme activities. In contrast, weaning to a high-fat diet prevented these modifications. Force feeding suckling rats with carbohydrates induced a rise in blood glucose and plasma insulin concentrations. During these experiments, mRNA concentrations increased 10- to 20-fold for lipogenic enzymes and decreased 5-fold for PEPCK in less than 6 h, whereas all enzyme activities did not vary. This suggests a pretranslational regulation of gene expression. Force feeding suckling rats with a mixture of fat devoid of carbohydrate induced a slight increase in plasma insulin concentration and a fall in PEPCK mRNA but was not accompanied by a rise in lipogenic enzyme mRNAs. This suggested that insulin is a prime regulator of PEPCK gene expression, whereas glucose and insulin act synergistically in the regulation of lipogenic enzyme gene expression.
Coupe
C
C
Centre de Recherches sur la Nutrition, Centre National de la Recherche Scientifique, Meudon-Bellevue, France.
Perdereau
D
D
Ferre
P
P
Hitier
Y
Y
Narkewicz
M
M
Girard
J
J
D000103:Acetyl-CoA Carboxylase / Q000235:genetics / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D000833:Animals, Suckling; D015342:DNA Probes; D004435:Eating; D064429:Fatty Acid Synthases / Q000235:genetics / Q000378:metabolism*; D005260:Female; D007700:Kinetics; D008025:Ligases / Q000378:metabolism*; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis* / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D014886:Weaning
D015342:DNA Probes; D012333:RNA, Messenger; D064429:Fatty Acid Synthases; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D008025:Ligases; D000103:Acetyl-CoA Carboxylase