Resveratrol Reduces Steroidogenesis in Rat Ovarian Theca-Interstitial Cells: The Role of Inhibition of Akt/PKB Signaling Pathway

Abstract

Polycystic ovary syndrome is characterized by theca-interstitial hyperplasia and increased expression of steroidogenic genes, leading to excessive androgen production. Resveratrol, a natural polyphenol, promotes apoptosis and reduces rat theca-interstitial cell growth, in part by inhibiting the mevalonate pathway and decreasing the availability of substrates of isoprenylation [farnesyl-pyrophosphate (FPP) and geranylgeranyl-pyrophosphate (GGPP)]. This study evaluated the effect of resveratrol on rat theca-interstitial cell steroidogenesis. Because resveratrol may activate sirtuins, this study also investigated whether steroidogenesis was affected by sirtuin inhibitors (nicotinamide, sirtinol). Theca-interstitial cells were cultured with or without resveratrol (1-10 μm), GGPP (30 μm), FPP (30 μm), nicotinamide (1 mm), and/or sirtinol (10 μm). Resveratrol did not affect progesterone levels but reduced androgen production in a concentration-dependent fashion (androstenedione by up to 78% and androsterone by up to 76%). This inhibitory effect correlated with a decrease in mRNA expression of genes regulating androgen production, especially Cyp17a1 (by up to 73%). GGPP and FPP had no effect on androgen levels and Cyp17a1 mRNA levels and did not alter the effects induced by resveratrol. Similarly, sirtuin inhibitors did not reverse resveratrol-induced inhibition of steroidogenesis. However, resveratrol decreased activity of serine-threonine kinase/protein kinase B pathway, a cell-signaling pathway involved in ovarian steroidogenesis. The present findings indicate that resveratrol reduces androgen production primarily by inhibiting Cyp17a1 mRNA expression, and this inhibition may be mediated, in part, by blocking the activity of the serine-threonine kinase/protein kinase B pathway. These findings may be of clinical relevance to conditions associated with excessive production of androgens by theca cells, such as polycystic ovary syndrome.