Adropin may regulate corpus luteum formation and its function in adult mouse ovary

Adropin, a unique peptide hormone, has been associated with the regulation of several physiological processes, including glucose homeostasis, fatty acid metabolism, and neovascularization. However, its possible role in ovarian function is not understood. Our objective was to examine the expression of adropin and its putative receptor, GPR19, in the ovaries of mice at various phases of the estrous cycle.

Immunohistochemistry and western blot analysis were performed to explore the localization and changes in expression of adropin and GPR19 in the ovaries during different phases of the estrous cycle in mice. Hormonal assays were performed with ELISA. An in vitro study was performed to examine the direct effect of adropin (10, 100 ng/ml) on ovarian function.

A western blot study showed that adropin and GPR19 proteins were maximum during the estrus phase of the estrous cycle. Interestingly, adropin and GPR19 displayed intense immunoreactivity in granulosa cells of large antral follicles and corpus luteum. This suggested the possible involvement of adropin in corpus luteum formation. Adropin treatment stimulated progesterone synthesis by increasing GPR19, StAR, CYP11A1, and 3β-HSD expressions, while it decreased estrogen synthesis by inhibiting 17β-HSD and aromatase protein expressions. Moreover, adropin treatment upregulated the cell cycle arrest-CDK inhibitor 1B (p27^kip1), pERK1/2, and angiogenic protein (EG VEGF) that are involved in the process of luteinization.

Adropin GPR19 signaling promotes the synthesis of progesterone and upregulates the expression of p27^kip1, EG VEGF, and erk1/2, resulting in cell cycle arrest and neovascularization, which ultimately leads to corpus luteum formation.