Vitamin D and adipogenesis: new molecular insights.

The focus of the current review is to highlight some new insights into the molecular mechanism by which vitamin D, a potentially nutritionally modulated factor, influences adipogenesis. Recent studies, predominantly using the mouse 3T3-L1 pre-adipocyte cell culture model, have shown that the role of vitamin D in inhibiting adipogenesis is mediated at the molecular level through a vitamin D receptor (VDR)-dependent inhibition of CCAAT enhancer binding protein-alpha (C/EBP alpha) and peroxisome proliferator-activated receptor-gamma (PPAR gamma) expression and a decrease in PPAR gamma transactivating activity in the pre-adipocyte. The latter action may reflect a vitamin D-induced decrease in endogenous PPAR gamma ligand availability and a competition between VDR and PPAR gamma for a limiting amount of retinoid X receptor (RXR), a common heterodimeric binding partner of both nuclear receptors.