Glucocorticoids repress induction by thiazolidinediones, fibrates, and fatty acids of phosphoenolpyruvate carboxykinase gene expression in adipocytes.
Phosphoenolpyruvate carboxykinase (PEPCK) exerts a glyceroneogenic function in adipocytes in which transcription of its gene is increased by unsaturated fatty acids and fibrates. We used cultured rat adipose tissue fragments and 3T3-F442A adipocytes to show that the antidiabetic thiazolidinedione BRL 49653, a ligand and an activator of the gamma isoform of peroxisome proliferator activated receptors (PPARgamma), is a potent inducer of PEPCK mRNA. In 3T3-F442A adipocytes, the effect of BRL 49653 is rapid and concentration dependent, with a maximum reached at 1 microM and a half-maximum at 10-100 nM. PEPCK mRNA is similarly induced by the natural ligand of PPARgamma, the 15-deoxy-delta(12-14) prostaglandin J2. These observations strongly suggest that PPARgamma is a primary regulator of PEPCK gene expression in adipocytes. Dexamethasone at 10 nM repress induction of PEPCK mRNA by 1 microM BRL 49653, 0.32 mM oleate, or 1 mM clofibrate, in a cycloheximide-independent manner. The antiglucocorticoid RU 38486 prevents dexamethasone action, demonstrating involvement of the glucocorticoid receptor. Stable transfectants of 3T3-F442A adipocytes bearing -2100 to +69 base pairs of the PEPCK gene promoter fused to the chloramphenicol acetyltransferase (CAT) gene respond to 1 microM BRL 49653 or 1 mM clofibrate by a large increase in CAT activity, which is prevented by the simultaneous addition of 10 nM dexamethasone. Hence, in adipocytes, glucocorticoids act directly through the 5'-flanking region of the PEPCK gene to repress, in a dominant fashion, the stimulation of PEPCK gene transcription by thiazolidinediones and fibrates.
Glorian
M
M
Centre de Recherche sur l'Endocrinologie Moléculaire et le Développement, C.N.R.S., Meudon, France.
Franckhauser-Vogel
S
S
Robin
D
D
Robin
P
P
Forest
C
C
D016475:3T3 Cells / Q000737:chemistry / Q000166:cytology; D017667:Adipocytes / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002994:Clofibrate / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects / Q000235:genetics; D005227:Fatty Acids / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005796:Genes / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D005938:Glucocorticoids / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007545:Isoproterenol / Q000037:antagonists & inhibitors / Q000494:pharmacology; D008297:Male; D051379:Mice; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000187:drug effects* / Q000235:genetics*; D014176:Protein Biosynthesis; D011506:Proteins / Q000187:drug effects; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D012045:Regulatory Sequences, Nucleic Acid / Q000187:drug effects / Q000235:genetics; D000077154:Rosiglitazone; D013844:Thiazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology; D045162:Thiazolidinediones; D015534:Trans-Activators / Q000494:pharmacology; D014157:Transcription Factors / Q000502:physiology
D000318:Adrenergic beta-Agonists; D005227:Fatty Acids; D005938:Glucocorticoids; D007004:Hypoglycemic Agents; D011506:Proteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D045162:Thiazolidinediones; D015534:Trans-Activators; D014157:Transcription Factors; D000077154:Rosiglitazone; D003907:Dexamethasone; D010729:Phosphoenolpyruvate Carboxykinase (GTP); D002994:Clofibrate; D007545:Isoproterenol