Lipogenic enzyme activities and mRNA in rat adipose tissue at weaning

Abstract

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.

Increased mitogen-activated protein kinase expression and activity in white adipose tissue of ventromedial hypothalamus-lesioned rats

“…The densitometric analysis of seven experiments revealed that 1 week after the VMH lesion the FAS mRNA expression was markedly increased (6-fold, p < 0.01) in WAT of VMH rats, in agreement with previous results [3]. PEPCK mRNA expression was markedly decreased (10-fold, p < 0.05) in WAT of VMH rats, in agreement with the well-known opposite regulation of FAS and PEPCK in WAT by modification of the hormonal and nutritional environment [22,26].…”

“…These probes were labelled with [a-32 P] dCTP using a rediprime labelling system kit. Hybridization conditions were performed as described previously [21][22][23]. The blots were exposed for 6-48 h at − 80°C with intensifying screens.…”

“…Since ERK-1 protein is over-expressed in WAT of VMH rats, we have measured the level of ERK-1 mRNA in adipose tissue of control and VMH rats. As internal controls, we studied the mRNA expression of two important metabolic enzymes, fatty-acid synthase (FAS) and phosphoenolpyruvate carboxykinase (PEPCK) which are subjected to important hormonal and nutritional regulation in WAT [22,25]. Representative Northern blot hybridizations with cDNA encoding for FAS, PEPCK and ERK-1 are shown in Figure 3.…”

Adiponutrin, a Transmembrane Protein Corresponding to a Novel Dietary- and Obesity-linked mRNA Specifically Expressed in the Adipose Lineage

“…Thus, in adipose tissue, the increase in lipogenesis after weaning to a commercial diet (high carbohydrate) is accompanied by a large increase in three major lipogenic enzyme activities and levels of corresponding mRNAs (i.e. FAS, acetyl-CoA carboxylase, and ATP-citrate lyase (24,25)). Nuclear spot 14 protein, the expression of which matches that of lipid synthesis (26), is also induced by premature weaning and disappears in catabolic circumstances such as fasting (27).…”

Insulin effects on sterol regulatory-element-binding protein-1c (SREBP-1c) transcriptional activity in rat hepatocytes

“…Total cellular RNAs were extracted from cultured hepatocytes using the guanidine thiocyanate method [11] and prepared for Northern-blot hybridization as described previously [12]. Labelling of each DNA probe with [α-$#P]dCTP was performed by random priming (Rediprime labelling kit ; Amersham Pharmacia Biotech, Little Chalfont, Bucks., U.K).…”