Modulation of Early Human Preadipocyte Differentiation by Glucocorticoids

Abstract

Glucocorticoids provide an adipogenic stimulus that is most obvious in the truncal obesity of patients with Cushing's syndrome. Glucocorticoid treatment also strongly potentiates the differentiation of human preadipocytes in culture. However, the molecular basis of these stimulatory effects remains to be defined. In this study, we provide a detailed analysis of the specific contribution of glucocorticoid treatment to the differentiation of primary human preadipocytes cultured in chemically defined medium. Contrary to previous descriptions of glucocorticoids being required throughout the course of differentiation, our results show that glucocorticoid treatment is stimulatory only during the first 48 h of differentiation. Furthermore, stimulation by glucocorticoids and the peroxisome proliferator activator receptor-gamma agonist troglitazone is mediated sequentially. Several details of the early events in the differentiation of human preadipocytes and the contribution of steroid to these events differ from the responses observed previously in murine preadipocyte models. First, glucocorticoid treatment stimulated the early accumulation of CCAAT enhancer binding protein-beta (C/EBPbeta) in primary human preadipocytes. Second, induction of C/EBPalpha in primary human preadipocytes was noted within 4 h of adipogenic stimulus, whereas C/EBPalpha induction is not detected until 24-48 h in the murine 3T3 L1 preadipocyte model. Remarkably, by contrast to human primary preadipocytes, which do not undergo postconfluent mitosis, 3T3 L1 murine preadipocytes stimulated to differentiate under chemically defined conditions required glucocorticoids to survive the clonal expansion that precedes terminal differentiation, revealing a novel signal imparted by glucocorticoids in this immortalized murine cell system.

PPARγ ligand production is tightly linked to clonal expansion during initiation of adipocyte differentiation

“…Interestingly, in vitro adipocyte differentiation of human cells occurs in the absence of mitotic clonal expansion but requires the addition of an exogenous PPAR ␥ agonist ( 30 ). Adipocyte differentiation of C3H10T1/2 cells does not rely on completion of cell division ( 10 )…”

Nuclear receptor regulation of stemness and stem cell differentiation

“…However, it is of interest to note that the inhibition of the Wnt pathway is not necessary for RARβ/active GSK3-induced adipogenic differentiation of mES cells. Treatment with the synthetic glucocorticoid, dexamethasone, is pro-adipogenic in the differentiation of both human and mouse preadipocyte models (Tomlinson et al, 2006). Indeed, RARβ and GR are constitutively expressed during differentiation process of 3T3-L1 cells (Fu et al, 2005).…”

Transcription factor C/EBPβ promotes the transcription of the porcine GPR120 gene

“…C/EBPb, a crucial member of C/EBPs family (Ramji & Foka 2002), is highly expressed in the adipose, intestine, lung, and liver (Garvey et al 2003) and plays a crucial role in mouse 3T3-L1 fat cell differentiation (Cristancho & Lazar 2011). Similarly, C/EBPb mRNA was previously reported to be transiently induced at early stages of adipogenesis in human preadipocytes (Tomlinson et al 2006, Fuentes et al 2010. Moreover, C/EBPb is activated by glycogen synthase kinase 3b (Tang et al 2005) and then triggers transcription of PPARg and C/EBPa to promote adipogenic differentiation (Tang & Lane 2012).…”