Effect of vitamin D₃ on uterine morphology and insulin signaling in a polycystic ovary syndrome (PCOS) rat model

Polycystic ovary syndrome (PCOS) is a common endocrinopathy in women of reproductive age leading to infertility. Besides reproductive and hormonal disturbances, PCOS is often characterized by vitamin D₃ (VD) deficiency. This study aimed to determine the effect of VD on uterine histoarchitecture, the biochemical composition of gland secretions, and the insulin signal transduction pathway using a PCOS rat model. The experiment was conducted on four animal groups (n=8/group): control (C), VD supplemented (VD; 500IU/day), letrozole-treated (PCOS; 1 mg/kg body weight), and VD-treated PCOS (PCOS+VD) group. Herein, VD supplementation did not improve histomorphometric parameters in the PCOS uterus, whereas clearly influenced sugar composition in uterine gland secretions, restoring their content to that observed in the C group. Furthermore, we found that VD can reduce peripheral and local uterine insulin resistance developed in the PCOS rats via activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway and subsequent glucose metabolism in the uterus. To sum up, the present results suggest a possible beneficial role of VD supplementation for the maintenance of uterus functions in PCOS rats.