Adipocyte differentiation is inhibited by melatonin through the regulation of C/EBPbeta transcriptional activity.
Considering that melatonin has been implicated in body weight control, this work investigated whether this effect involves the regulation of adipogenesis. 3T3-L1 preadipocytes were induced to differentiate in the absence or presence of melatonin (10(-3) m). Swiss-3T3 cells ectopically and conditionally (Tet-off system) over-expressing the 34 kDa C/EBPbeta isoform (Swiss-LAP cells) were employed as a tool to assess the mechanisms of action at the molecular level. Protein markers of the adipogenic phenotype were analyzed by Western blot. At 36 hr of differentiation of 3T3-L1 preadipocytes, a reduction of PPARgamma expression was detected followed by a further reduction, at day 4, of perilipin, aP2 and adiponectin protein expression in melatonin-treated cells. Real-time PCR analysis also showed a decrease of PPARgamma (60%), C/EBPalpha (75%), adiponectin (30%) and aP2 (40%) mRNA expression. Finally, we transfected Swiss LAP cells with a C/EBPalpha gene promoter/reporter construct in which luciferase expression is enhanced in response to C/EBPbeta activity. Culture of such transfected cells in the absence of tetracycline led to a 2.5-fold activation of the C/EBPalpha promoter. However, when treated with melatonin, the level of C/EBPalpha promoter activation by C/EBPbeta was reduced by 50% (P = 0.05, n = 6). In addition, this inhibitory effect of melatonin was also reflected in the phenotype of the cells, since their capacity to accumulate lipids droplets was reduced as confirmed by the poor staining with Oil Red O. In conclusion, melatonin at a concentration of 10(-3 ) m works as a negative regulator of adipogenesis acting in part by inhibiting the activity of a critical adipogenic transcription factor, C/EBPbeta.
Alonso-Vale
Maria Isabel Cardoso
MI
Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Sao Paulo, SP, Brazil.
Peres
Sidney Barnabé
SB
Vernochet
Cécile
C
Farmer
Stephen R
SR
Lima
Fabio Bessa
FB
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D052242:Adiponectin / Q000235:genetics; D000818:Animals; D015153:Blotting, Western; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000235:genetics; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects* / Q000235:genetics; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D050556:Fatty Acid-Binding Proteins / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D008550:Melatonin / Q000494:pharmacology*; D051379:Mice; D047495:PPAR gamma / Q000235:genetics; D016133:Polymerase Chain Reaction; D015533:Transcriptional Activation / Q000187:drug effects
D052242:Adiponectin; D022763:CCAAT-Enhancer-Binding Protein-alpha; D022782:CCAAT-Enhancer-Binding Protein-beta; D002492:Central Nervous System Depressants; C493411:Fabp4 protein, mouse; D050556:Fatty Acid-Binding Proteins; D047495:PPAR gamma; D008550:Melatonin