EGCG improves follicular development of diabetic mice by the hypothalamic-pituitary-ovarian axis

Impaired oocyte quality of diabetic mice can be improved by epigallocatechin gallate (EGCG) in vitro. However, the underlying mechanism is unknown. Here, we examined whether EGCG improves follicular development of diabetic mice by acting on the hypothalamic-pituitary-ovarian axis.

We investigated the estrous cyclicity of diabetic mice before (DM) and after treatment with EGCG (DM+EGCG) and found that DM do not have obvious proestrus and estrus phases but recovered near normal estrous cycle after EGCG treatment. We next examined the serum levels of various hormones and found that EGCG treatment significantly alleviated the impacts of diabetes on follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Abnormal levels of estradiol (E2), androgen, and progesterone (PROG) in DM were also improved after EGCG treatment, suggesting that EGCG improved the functioning of the reproductive endocrine system. The proportions of follicles at different stages were similar in all groups but the total number of follicles increased significantly with EGCG treatment, suggesting that EGCG may increase follicle numbers by improving the primordial follicle pool. We then examined the expression of genes associated with the activation and apoptosis of primordial follicles. Our data showed that the decreased number of primordial follicles in DM mice are caused by the increased apoptosis, which improved with EGCG treatment.

Our results indicate that EGCG alleviates the adverse effects of diabetes on follicular development in vivo by improving the function of the reproductive endocrine system.