Dehydroepiandrosterone effects on the mRNA levels of peroxisome proliferator-activated receptors and their coactivators in human hepatoma HepG2 cells

To investigate the effect of dehydroepiandrosterone (DHEA) on intracellular mRNA levels of peroxisome proliferator-activated receptors (PPARs) and PPAR-gamma coactivators (PGCs), we conducted a quantitative real-time RT-PCR study using HepG2 cells. Treatment with 100 mu mol/l DHEA for 2-20 h caused a time-dependent elevation of mRNA levels in the cells. Upon 20 h, PPAR-alpha, -gamma 1, and -gamma 2 mRNAs and PGC-1 alpha and -1 beta mRNAs increased to 157,161,155,656, and 475% of control levels, respectively (p < 0.05 each). Treatment with actinomycin D for 2.5-8 h revealed a significant stabilization effect of DHEA on PPAR-gamma 1 and PGC-1 alpha mRNAs at both 2.5 and 8 h incubation periods and a mild but significant stabilization effect on PGC-1 beta mRNA at the 8 h incubation period suggesting that DHEA can modulate turnover of these mRNA transcripts. Basal mRNA levels of PPAR-a and PGC-1 alpha were significantly suppressed upon 20 h treatment with cycloheximide, while those of PPAR-gamma 1, -gamma 2,and PGC-1 beta were elevated. Cycloheximide also significantly reduced DHEA-induced accumulation of PPAR-alpha, -gamma 1, -gamma 2, and PGC-1 alpha mRNAs, demonstrating the dependence of the DHEA action on de novo protein synthesis. The findings demonstrate that a supraphysiological concentration of DHEA can substantially influence gene expression of the PPAR signalling machinery at both transcriptional and posttranscriptional levels.