Effect of SIRT1 on cellular apoptosis and steroidogenesis in bovine ovarian granulosa cells in vitro

• Resveratrol increased mRNA levels of SIRT1, but significant decrease was observed under the treatment of nicotinamide.
• Resveratrol significantly induced late apoptosis, while the significant increase was not found under nicotinamide treatment.
• Resveratrol decreased levels of estradiol, but higher levels of estradiol were obtained in the presence of nicotinamide.
• Resveratrol increased levels of progesterone, while nicotinamide significantly decreased the production of progesterone.
• Resveratrol decreased mRNA levels of SF-1, while significant increase was observed under the treatment of nicotinamide.

Sirtuin type 1 (SIRT1) gene plays an important role in the regulation of female reproduction, and we set out to determine if SIRT1 affects steroidogenesis. In this study, granulosa cells isolated from bovine ovaries were cultured and treated with resveratrol or nicotinamide, a SIRT1 activator or inhibitor, respectively. The mRNA and protein levels of SIRT1 of cultured granulosa cells were investigated by quantitative real-time RT-PCR and Western blot, and then the extent of cellular apoptosis was measured by FACS assay. The amounts of estradiol and progesterone in cultured media were measured by radioimmunoassay, and mRNA and protein levels of Steroidogenic Factor 1 (SF-1) were also investigated. We demonstrated that resveratrol exhibited a dose-dependent induction of SIRT1 expression, associated with late apoptosis in granulosa cells, while nicotinamide decreased SIRT1 expression with no effect on apoptosis. We observed the estradiol levels and SF-1 expression decreased while progesterone level increased after the treatment of resveratrol, but the opposite results were observed in the treatment of nicotinamide. In conclusion, SIRT1 affected apoptosis, steroidogenesis and the related gene expression in granulosa cells, which may provide new insight into the treatment of follicular and/or luteal phase deficiency.