Resveratrol improves the quality of pig oocytes derived from early antral follicles through sirtuin 1 activation

During oocyte growth, the number of mitochondria drastically increases and mitochondrial function profoundly affects the oocyte competence. Resveratrol is a well-known activator of sirtuin 1 (SIRT1), which has a role in cellular energy homeostasis and mitochondrial biogenesis. The main aim of the present study was to examine the effect of supplementation of culture media with resveratrol on oocyte development and mitochondrial number and functions. Lipid contents and developmental ability of the oocytes grown in vitro were also examined. Oocyte-granulosa cell complexes were collected from early antral follicles of gilt ovaries and were cultured in medium containing 0 or 2 μM resveratrol for 14 days. Immunostaining revealed that resveratrol enhanced SIRT1 expression in oocytes. Antrum formation during the culture period and survivability of the granulosa cells surrounding the developed oocytes did not differ between the two concentrations of resveratrol. In addition, the ability of oocytes to complete meiotic maturation did not differ between the two concentrations of resveratrol, whereas the ability of oocytes to develop to the blastocyst stage was improved significantly by resveratrol (7.4% vs. 1.6%; P < 0.05). Resveratrol upregulated the ATP content in oocytes grown in vitro, and the addition of 2 μM of the SIRT1 inhibitor 6-Chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide (EX527) diminished this effect although EX527 alone had no effect on ATP content. The mitochondrial DNA copy number in oocytes determined by quantitative real-time polymerase chain reaction increased during in vitro oocyte development, but resveratrol did not affect the kinetics of the mitochondrial DNA copy number. We found that resveratrol also increased the expression level of phospho-5′-adenosine monophosphate–activated protein kinase in oocytes but decreased the lipid content in oocytes grown in vitro. These results suggest that resveratrol increased the ATP content in oocytes via energy homeostasis and improved the developmental ability of oocytes grown in vitro.