Vitamin D3-induced changes in steroidogenic pathway within periovarian adipose tissue of rats with polycystic ovary syndrome*

This study investigated the effect of vitamin D₃ on polycystic ovary syndrome (PCOS) characteristics, as well as on periovarian adipose tissue (POAT) morphology and function, through the expression of key molecules involved in steroidogenesis in a letrozole-induced rat model of PCOS. Over a 21-day experimental period, 32 female Wistar rats were randomly assigned to four groups (n=8 per each group): control (C), vitamin D₃-supplemented (VD), letrozole-treated to induce PCOS (L), and letrozole plus vitamin D₃-treated (VD+L). PCOS induction was confirmed in the L group by increased body weight, acyclicity, ovarian cyst formation, and hyperandrogenism. Following vitamin D₃ treatment, single antral follicles in the ovary and a few nucleated epithelial cells in vaginal smears were observed in the VD+L group. The induction of PCOS increased the average size of periovarian adipocytes, whereas vitamin D₃ reversed this effect. Regarding the effect of vitamin D₃ on steroidogenesis in POAT, mRNA transcript and protein abundances of StAR protein and CYP17A1 were unchanged among groups. A decrease in CYP11A1 protein abundance was noted in the L and VD+L groups, alongside reduced 3βhsd transcript level. However, vitamin D₃ exerted the most pronounced effect on CYP19A1 expression, with significantly greater mRNA and protein abundances in the VD+L group than in the L group, suggesting enhanced 17β-estradiol synthesis. Overall, these findings highlight the crucial role of vitamin D₃ in modulating POAT steroidogenesis, which may in turn impact ovarian function and improve reproductive parameters in PCOS.