Endocrine Abstracts

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is one of the isoforms of the PPAR-family of nuclear hormone receptors. Ligand activated PPARs dimerise with retinoid X receptor and act as transcription factors translating nutritional, pharmacological and metabolic stimuli into changes in the expression of genes. PPARgamma is thought to serve several roles in adipocyte differentiation, fatty acid and lipid metabolism and insulin sensitivity. PPARgamma has also been shown to modulate ovarian steroidogenesis of bovine and porcine ovarian cells. Thiazolidinediones, PPARgamma agonists, have been shown to improve insulin sensitivity and reduce androgen production in women with polycystic ovary syndrome. The aim of this study was to investigate the expression of PPARgamma and the effect of PPARgamma and RXR ligands on steroidogenesis and proliferation of a human granulosa transfected cell line (HGC-5). Using RT-PCR and PCR TaqMan technology, we demonstrated the presence of mRNA for PPARgamma and P450scc (cholesterol side chain cleavage enzyme) in HGC-5s. The cells lack receptors for LH and FSH but are responsive to forskolin, a stimulator of adenylate cyclase. After HGC-5s were incubated with PPARg and RXR ligands plus/minus forskolin (10 microMolar) for 48h, progesterone production and cell proliferation were measured using radioimmunoassay and a mitochondrial tetrazolium assay, respectively. The PPARgamma ligands farglitazar, rosiglitazone and troglitazone showed no consistent effect on basal progesterone production but the RXR ligand LG-retinoid significantly increased progesterone production (P<0.05) at 0.1 and 10 microMolar concentrations. In the presence of forskolin, however, farglitazar at 1 and 10 microMolar and LG-retinoid at 0.1, 1 and 10 microMolar concentrations stimulated significantly (P<0.001) progesterone production compared to the effects of forskolin alone. There was no effect of PPARgamma and RXR ligands on proliferation of HGC-5s. These results demonstrate that agonists of PPARgamma and RXR mediate progesterone production in a human granulosa cell line, adding support for the concept of a physiological role for these nuclear receptors in human ovarian steroidogenesis. This work was supported by Wellbeing.