Stimulation of preadipocyte differentiation by steroid through targeting of an HDAC1 complex

Abstract

Glucocorticoids potentiate the early steps of preadipocyte differentiation and promote obesity in Cushing's syndrome and during prolonged steroid therapy. We show that glucocorticoids stimulate 3T3 L1 preadipocyte differentiation through a non-transcriptional mechanism mediated through the ligand-binding domain of the glucocorticoid receptor. This enhanced the onset of CCAAT/enhancer binding protein (C/EBPa) expression by potentiating its initial transcriptional activation by C/EBPb. In the absence of steroid, C/EBPb associated with a transcriptional corepressor complex containing mSin3A and histone deacetylase 1 (HDAC1), but lacking HDAC2 and RbAp46/48. HDAC1/mSin3A were recruited to the C/EBPa promoter with C/EBPb and promoted the deacetylation of histone H4. Steroid induced the speci®c depletion of this corepressor by targeting the HDAC1 within the complex for degradation through the 26S proteasome. Treatment with histone deacetylase inhibitors replaced the effects of steroid treatment on preadipocyte differentiation and C/EBPa expression, while overexpression of HDAC1 abrogated the stimulatory effects of steroid. Recapitulation of the glucocorticoid effect by progestin treatment in the presence of the progesterone receptor ligand-binding domain suggests a conserved mechanism relevant to many aspects of steroid-mediated differentiation. Keywords: CAAT enhancer binding protein b function/ histone deacetylase 1/initiation of preadipocyte differentiation/26S proteasome/steroid hormone action IntroductionThe glucocorticoid receptor (GR) is a ligand-activated nuclear hormone receptor that regulates gene expression primarily through direct interaction with DNA response elements (Mangelsdorf et al., 1995). Glucocorticoids provide an adipogenic stimulus that is most obvious in the truncal obesity of patients with Cushing's syndrome (Peeke and Chrousos, 1995). Weight gain is also a sideeffect of immunosuppressive glucocorticoid therapies (Pijl and Meinders, 1996). In rodents, the weight loss that follows adrenalectomy is prevented by glucocorticoid replacement (Freedman et al., 1986;Sainsbury et al., 2001). However, gene-targeted mice in which GR is compromised for DNA binding are of normal weight and do not display any overt signs of alterations in adipogenesis, suggesting that the effects of glucocorticoids on adipogenesis may be mediated through a non-genomic mechanism (Reichardt et al., 2000a).The adipocytes that constitute white fat originate from committed precursor cells, which differentiate in response to a series of cues including insulin and inducers of cAMP. In primary preadipocytes and most cell culture models, glucocorticoids strongly potentiate differentiation (Gregoire et al., 1998). The early responses to insulin and cAMP include the transient induction of CCAAT/enhancer binding protein (C/EBP) b and C/EBPd, and overexpression of C/EBPb is suf®cient to force preadipocyte differentiation in culture (Yeh et al., 1995). In vivo, the stimulatory effect of C/EBPb activity is complemented by the action of C/...

Prostaglandin F2α inhibits adipocyte differentiation via a Gαq‐Calcium‐Calcineurin‐Dependent signaling pathway

“…HDACs are enzymes that play an important role in the regulation of gene expression and are best known for their role in repressing gene transcription via interaction with transcriptional repressors [Ng and Bird, 2000]. Interestingly, both HDACs and transcriptional repressors have previously been implicated in the regulation of adipocyte differentiation: HDAC-1 has been shown to associate with the C/EBPa promoter and play an important role in preventing C/EBPa expression in unstimulated preadipocytes [Wiper-Bergeron et al, 2003], while a number of transcriptional repressors have been implicated in the regulation of adipogenesis via the direct inhibition of both C/EBPa and PPARg gene expression [Tong et al, 2000;Yun et al, 2002;Banerjee et al, 2003;Shi et al, 2003]. Hence, it is tempting to speculate that one potential mechanism by which the PGF2a-calcineurin signaling pathway may inhibit adipocyte differentiation is by inducing the expression and/or activity of an HDAC-associated transcriptional repressor that is either able to directly inhibit the expression of the PPARg and C/EBPa genes, or alternatively, acts indirectly, by inhibiting the expression of a gene(s) that is normally required to promote the expression of PPARg and C/ EBPa.…”

Expression and activity of steroid aldoketoreductases 1C in omental adipose tissue are positive correlates of adiposity in women

“…Testosterone treatment also inhibited the activity of adipose tissue LPL (21,22). On the other hand, the specific role of progesterone on fat metabolism is not yet completely elucidated, as some studies found that progesterone stimulated fat accumulation, LPL activity, lipogenesis, and steroid-mediated differentiation of preadipocytes (20,32,35), and others reported that progesterone could be responsible for the female fat distribution pattern via an anti-glucocorticoid action in abdominal fat (26,37). Whether increased metabolism of these steroids in adipose tissue of obese women, through enzymes examined here, relates to actually increased or reduced binding of the steroids to their receptors remains unclear (16).…”

Anti-inflammatory functions of glucocorticoid-induced genes

“…Finally, GCs can enhance the function of C/EBPβ. This process involves the phosphorylation of C/EBPβ and exchange of associated coactivator/corepressor proteins, although it is unclear whether a direct interaction between GR and C/EBPβ is required (Berg et al, 2005;Boruk et al, 1998;Wiper-Bergeron et al, 2003).…”