Background: Metformin is an antidiabetic drug used for the treatment of infertility in polycystic ovarian syndrome and has been shown to affect the functions of granulosa cells (GC) in humans and rodents. Recently, metformin has been shown to enhance folliculogenesis, ovulation rate and prolificacy in sheep. The objective of this study was to determine the effect of metformin on GC isolated from sheep ovaries on cell number, proliferation, steroidogenesis and some hormones and genes related to follicular development. 
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Methods: GC were cultured in 3D culture using hanging drops for 48 hours and then treated with various concentrations of metformin (0.001 mM, 0.01 mM, 0.1 mM), dorsomorphin (0.1 mM), or a combination of both (0.1 mM) for 48 hours. Cell number and proliferation were measured using the trypan blue exclusion dye method and MTT assay. Progesterone, estradiol and insulin concentration in culture media were quantified by RIA. The expression of GLUT4, PPAR&alpha; and SREBP1c was determined by qPCR. 
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Result: Metformin enhances the number and proliferation of GC while reducing the concentration of steroid hormones, such as androstenedione, progesterone and estrogen, in a dose-dependent manner. It also decreases the gene expression levels of SREBP1c and upregulates the mRNA expression of PPAR&alpha; and GLUT4 and dorsomorphin treatment reverses these effects. These results suggest that metformin may modulate ovarian steroidogenesis, metabolism and folliculogenesis, influencing sheep reproductive-performance. However, further studies are required to investigate the detailed mechanism through which metformin exerts its effect.

Metformin Modulates Steroidogenic and Metabolic Functions in Cultured Ovine Granulosa Cells