Inactivation of Histone Deacetylase 1 (HDAC1) But Not HDAC2 Is Required for the Glucocorticoid-Dependent CCAAT/Enhancer-Binding Protein α (C/EBPα) Expression and Preadipocyte Differentiation

Several drugs currently used in the management of mood disorders, epilepsy (ie, valproic acid), or the control of inflammation (ie, corticosteroids) have been shown to promote visceral obesity in humans by increasing the number of newly formed adipocytes. Valproic acid is classified as a nonspecific histone deacetylase (HDAC) inhibitor, along with trichostatin A and butyric acid. In vitro experiments have demonstrated that such molecules greatly enhance the rate of preadipocyte differentiation, similarly to the effect of corticosteroids. The glucocorticoid receptor stimulates adipogenesis in part by enhancing the transcription of C/ebpa through the titration, and subsequent degradation, of HDAC1 from the C/ebp alpha promoter. There is, however, controversy in the literature as to the role of HDACs during adipogenesis. In this study, we sought to demonstrate, using 2 different strategies, the definite role of HDAC1 in adipogenesis. By using small interference RNA-mediated knockdown of HDAC1 and by generating an enzymatically inactive HDAC1(D181A) by site-directed mutagenesis, we were able to show that HDAC1, but not HDAC2, suppresses glucocorticoid receptor-potentiated preadipocyte differentiation by decreasing CCAAT/enhancer-binding protein (C/ebp)alpha and Ppar gamma expression levels at the onset of differentiation. Finally, we demonstrate that HDAC1(D181A) acts as adominant negative mutant of HDAC1 during adipogenesis by modulating C/EBP alpha transcriptional activity on the C/ebp alpha promoter.