Fig. 1.

Glucocorticoid treatment of naive preadipocytes enhances subsequent differentiation and induces components of the insulin signaling pathway. A, Photomicrographs of Oil Red O staining of neutral lipids content (upper) and Western analysis of aP2 protein expression (lower) from human adipocytes differentiated for 14 d. Differentiation was preceded by 48 h culture of the cells with vehicle (left) or 1 μm dex (right, +dex). To initiate differentiation, cells were treated with MIX and insulin (MI) or MIX, insulin, and 1 μm dex (MID). Scale bar, 1mm. Results are representative of a minimum of five repeats. B, Microarray analysis derived AFC of insulin signaling components in human preadipocytes. AFC of mRNA expression compared with control cells was determined using RMA analysis, and statistical validation was calculated using FDR-CI analysis. C, qRT-PCR-derived average fold induction in mRNA abundance at d 0 of IR, IRS1, IRS2, and PI3KR1 in dex-pretreated (+) compared with control (−) human preadipocytes. For analysis, n = 3, each performed in duplicate. Data are plotted ±sem. *, P ≤ 0.05; **, P ≤ 0.01 as determined using a Student’s paired t test. D, Western analysis of protein expression at d 0 in control (−) and dex-pretreated (+) cells. Average fold induction ±sd was calculated by densitometry using ImageQuant software (n ≥ 3). P value was determined as described in C: †, P ≤ 0.1; *, P ≤ 0.05. Hs., Homo sapiens.