Biological Roles of PPAR-γ and C/EBP on Adipogenesis and SCD-1 Gene Expression

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It is shown that C/EBP family proteins and PPAR-γ play important roles on adipocyte differentiation. However, the precise roles of each molecule have not been defined. To explore this issue, we transfected C/EBP-β and -δ double knockout mouse embryonic fibroblasts with adenovirus vector containing mouse PPAR-γ2 (pAdex-mPPARγ2). When the pAdex-mPPARγ2-transfected cells were stimulated with troglitazone or 15-deoxy-△ィイD112.14ィエD1-PGJ2, they became to show mature adipocyte phenotype stained with oil-red-O. Intracellular triglyceride content and SCD-1 and aP2 mRNA levels of these cells did not differ, compared with wild-type mouse embryonic fibroblasts transfected with pAdex-mPPARγ2. However, LPL and GLUT4 mRNA levels were significantly lower in these cells. Thus, forced expression of PPAR-γ2 alone can induce adipocyte differentiation in the absence of C/EBP-β and C/EBP-γ, although C/EBP-β and /or C/EBP-δ are important for the expression of some adipocyte-specific genes.