Selective effects of PPARγ agonists and antagonists on human pre-adipocyte differentiation

Aim: The insulin sensitizer rosiglitazone (RTZ) acts by activating peroxisome proliferator and activated receptor gamma (PPAR gamma), an effect accompanied in vivo in humans by an increase in fat storage. We hypothesized that this effect concerns PPAR gamma 1 and PPAR gamma 2 differently and is dependant on the origin of the adipose cells (subcutaneous or visceral). To this aim, the effect of RTZ, the PPAR gamma antagonist GW9662 and lentiviral vectors expressing interfering RNA were evaluated on human pre-adipocyte models. Methods: Two models were investigated: the human pre-adipose cell line Chub-S7 and primary pre-adipocytes derived from subcutaneous and visceral biopsies of adipose tissue (AT) obtained from obese patients. Cells were used to perform oil-red O staining, gene expression measurements and lentiviral infections. Results: In both models, RTZ was found to stimulate the differentiation of pre-adipocytes into mature cells. This was accompanied by significant increases in both the PPAR gamma(1) and PPAR gamma(2) gene expression, with a relatively stronger stimulation of PPAR gamma(2). In contrast, RTZ failed to stimulate differentiation processes when cells were incubated in the presence of GW9662. This effect was similar to the effect observed using interfering RNA against PPAR gamma(2). It was accompanied by an abrogation of the RTZ-induced PPAR gamma(2) gene expression, whereas the level of PPAR gamma(1) was not affected. Conclusions: Both the GW9662 treatment and interfering RNA against PPAR gamma(2) are able to abrogate RTZ-induced differentiation without a significant change of PPAR gamma(1) gene expression. These results are consistent with previous results obtained in animal models and suggest that in humans PPAR gamma(2) may also be the key isoform involved in fat storage.