Induction of aP2 gene expression by nonmetabolized long-chain fatty acids.

Abstract

Long-chain fatty acids (FA) have been shown to regulate expression of the gene for the adipocyte FA-binding protein aP2. We examined whether this effect was exerted by FA themselves or by a FA metabolite. The a-bromo derivative of palmitate, an inhibitor of FA oxidation, was synthesized in the radioactive form, and its metabolism was investigated and correlated with its ability to induce aP2 in Ob1771 preadipocytes. a-Bromopalmitate was not utilized by preadipocytes. It was not cleared from the medium over a 24-hr period and was not incorporated into cellular lipids. Short incubations indicated that a-bromopalmitate exchanged across the preadipocyte membrane but remained in the free form inside the cell. In line with this, preadipocyte homogenates did not activate a-bromopalmitate to the acyl form. However, although it was not metabolized, bromopalmitate was much more potent than native FA in inducing aP2 gene expression. Induction exhibited the characteristics previously described for native FA, indicating that a similar if not identical mechanism was involved. The data indicated that induction of aP2 was exerted by unprocessed FA. Finally, in contrast to preadipocytes, adipocytes metabolized bromopalmitate. This reflected increased activity with cell differentiation of a palmitoyl-CoA synthase that could activate palmitate and bromopalmitate at about one-fifth the rate for palmitate. In preadipocytes, the predominant fattyacyl-CoA synthase, arachidonyl-CoA synthase, had very low affinity for both FA. Increased activity of the palmitoyl-CoA synthase, which has a wider substrate range, is likely to be important for initiation of lipid deposition.Fatty acids (FA) (10)(11)(12). In this report, we investigated whether the effect of long-chain FA to induce aP2 in Ob1771 was exerted by FA themselves or by FA metabolism. This information would be essential to elucidate the molecular mechanism of the FA effect. Furthermore, a similar regulatory effect of FA might apply to other genes induced during adipose differentiation.For example, in Ob1771 preadipocytes, FA also induced the gene for fatty-acyl-CoA synthase (EC 2.3.1.86) (8). In BFC-1 preadipocytes, an increase in membrane transport of FA was an early event during cell differentiation, which would be consistent with FA playing a role in modulating subsequent differentiation steps (9).Our results, using a-bromopalmitate, indicate that induction of aP2 in preadipocytes is exerted by unprocessed FA. The data also demonstrate increased expression, with cell differentiation, of a palmitoyl-CoA synthase that has a wide range of FA substrates (which include a-bromopalmitate) and that is likely to be important for the initiation of adipogenesis. MATERIALS AND METHODSMaterials. Guanidinium isothiocyanate and films for autoradiography (X-Omat, AR) were from Kodak. Cesium chloride was from Fisher Scientific. The multiprime labeling kit for cDNA, the [32P]dCTP, and the nitrocellulose filters were from Amersham. The cDNA for aP2 (13) was a gift from H. Green (Harvard...

Stimulatory effect of unsaturated fatty acids on the level of plasminogen activator inhibitor‐1 mRNA in cultured human endothelial cells

“…5). We could also localize these consensus sequences in the promoter region of the murine PAI-1 gene, as well as in the regulatory regions of the rat S14 and murine aP2 genes, both of which have been reported to be transcriptionally regulated by fatty acids [23,25] (Fig. 5).…”

“…One potential explanation could be that the fatty acids are directly involved in transcriptional regulation of the PAI-1 gene. An interesting feature of the polyunsaturated fatty acids is their ability to regulate the expression of genes by binding to fatty acid responsive factors [22,23,25]. Sloots et al identified consensus nucleotide sequences in the upstream region of five oleic acid-inducible genes of the diploid yeast Candida lropicalis.…”

“…Exogenously provided fatty acid can serve as a biological effector [18]. Fatty acids can also be directly involved in regulating gene expression by binding to specific, fatty acidresponsive transcription factors [19][20][21][22][23][24][25].…”

Induction of Hepatic Glucose-6-Phosphatase Gene Expression by Lipid Infusion

“…Indeed, dietary fatty acids have been shown to regulate the gene expression of pancreatic GLUT2 and glucokinase (16), and long-chain fatty acids can induce the expression of the genes for the adipocyte fatty acid-binding protein aP2 (17) and liver carnitine palmitoyltransferase I (CPT I) (18). Additionally, the expression of a number of hepatic lipogenic, glycolytic, and gluconeogenic genes is regulated by polyunsaturated fatty acids at the transcriptional level (19,20).…”

CORPS GRAS ET OBESITE Acides gras alimentaires et obésité : aspects qualitatifs et quantitatifs

“…Ainsi, les bases moléculaires par lesquelles les AGPI affectent l'expression génique hépatique impliquent vraisemblablement au moins deux voies distinctes mettant en jeu soit des facteurs trans soit des éléments régulateurs en cis. Tandis que la répression de l'expression génique semble être due aux AGPI, les acides gras saturés et insaturés sont capables de stimuler l'expression de gènes dans le foie [63] et dans le tissu adipeux blanc [64,65]. Le fait que les effets des AGPI sur l'expression génique soient rapides dans le foie et beaucoup plus lents dans le tissu adipeux est en faveur d'une régulation spécifique du type tissulaire considéré [58,48].…”