Glucocorticoids induce the expression of the leptin gene through a non-classical mechanism of transcriptional activation.
Leptin is a hormone which is produced in adipose tissue and which plays a role in the regulation of energy homeostasis. The expression of the ob gene, encoding leptin, is under multi-hormonal control. We have shown previously that high doses of glucocorticoids are positive regulators of leptin expression in rats and that they concomitantly reduce food intake and body mass gain in these animals. In the present report we analyse the molecular mechanism of this glucocorticoid regulation of leptin expression. In cultured rat adipocytes dexamethasone induces leptin mRNA levels, an effect not inhibited by the protein synthesis inhibitor cycloheximide. In addition, our data indicate that the induction of the expression of the leptin gene by dexamethasone is at least in part due to a transcriptional activation that is mediated by the glucocorticoid receptor. Deletion mapping of the human leptin promoter shows that cis-elements involved in the glucocorticoid effect are located between -55 and +31 relative to the transcription initiation site. Since this region does not contain a binding site for the glucocorticoid receptor, the effect does not rely on the classical molecular mechanism of glucocorticoid receptor action. A role of C/EBP and Sp-1 in mediating this glucocorticoid effect was furthermore excluded. Multiple nuclear factors from 3T3-L1 preadipocytes interact with this promoter region of the human leptin gene and may be potential mediators of the induction by glucocorticoids.
De Vos
P
P
INSERM U325 and Département d'Athérosclérose, Institut Pasteur, Lille, France.
Lefebvre
A M
AM
Shrivo
I
I
Fruchart
J C
JC
Auwerx
J
J
D016475:3T3 Cells; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D020738:Leptin; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
D017931:DNA Primers; D020738:Leptin; D009687:Nuclear Proteins; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D003907:Dexamethasone