Resistin decreases insulin-like growth factor I–induced steroid production and insulin-like growth factor I receptor signaling in human granulosa cells

Objective To identify resistin in human ovarian follicles and investigate the effect and the molecular mechanisms associated with resistin on steroidogenesis in human granulosa cells (GCs). Design The effects of recombinant human resistin on the secretion of progesterone (P) and estradiol (E2 ) by cultured human GCs were investigated. Setting Academic institutions. Patient(s) Twenty infertile and healthy women undergoing IVF. Intervention(s) Primary human GC cultures stimulated with recombinant human resistin (10 ng/mL). Main Outcome Measure(s) Determination of messenger RNA (mRNA) and protein expression of resistin in fresh human GCs by reverse transcriptase-polymerase chain reaction (RT-PCR), immunoblot and immunohistochemistry, respectively; measurement of P and E2 levels in the conditioned media by radioimmunoassay; determination of cell proliferation by tritiated thymidine incorporation; and analysis of signaling pathways activation by immunoblot analysis. Result(s) Human GCs and theca cells express resistin. In primary human GCs, resistin decreases P and E2 secretion in response to insulin-like growth factor I (IGF-I). This was associated with a reduction in the P450 aromatase and P450scc (cholesterol side-chain cleavage cytochromes P450) (P450scc) protein levels but not those of 3β-hydroxysteroid dehydrogenase (3β-HSD) or steroidogenic acute regulatory protein (StAR) and with a decrease in IGF-I-induced IGF-I receptor and mitogen-activated protein kinase (MAPK) extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Resistin treatment does not affect IGF-I-induced cell proliferation and basal steroidogenesis (there is no IGF-I or follicle-stimulating hormone stimulation). In the basal state, resistin rapidly stimulates Akt and MAPK ERK1/2 and p38 phosphorylation in primary human GCs. Conclusion(s) Resistin is present in human GCs and theca cells. It decreases P and E2 secretion, P450scc and P450 aromatase protein levels, and IGF-IR signaling in response to IGF-I in primary human GCs.