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

Abstract

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.