Fig. 6.
DHEA attenuates preadipocyte differentiation via inhibition of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) oxoreductase activity. A and B: cells differentiated for 21 days in the presence of DHEA (0–25 μM) were incubated with serum-free DMEM containing 100 nM cortisone and 50,000 cpm/ml [3H]cortisone for 3 h. Individual well protein concentrations were calculated and used as an internal control. DHEA (≥1 μM) significantly inhibited 11β-HSD1 oxoreductase activity (A) and increased dehydrogenase activity (B). Data are expressed as means ± SE of 3 independent triplicate experiments. C: Chub-S7 cells were differentiated in the presence of DHEA (0–25 μM) and 500 nM cortisone (black bars) or 500 nM cortisol (open bars). mRNA expression analysis is presented at the time point where the most significant effect of DHEA coincubated with cortisone was observed: LPL and H6PDH, day 14; G3PDH and 11β-HSD1, day 21. mRNA expression was determined by quantitative PCR and expressed as %decrease in control. Data were obtained from 3 independent experiments. Statistical analysis was performed on ΔCT values. DHEA (≥10 μM), when coincubated with inactive cortisone, significantly inhibited LPL, G3PDH, and 11β-HSD1 expression to a greater extent than when coincubated with active cortisol. In contrast, there was no significant difference in H6PDH expression between treatments. *P < 0.05 and **P < 0.01 vs. control.