Expression of leptin and its long-form receptor in the porcine corpus luteum during pregnancy and the protective role of leptin in corpus luteum function in vitro

Although the hormone leptin and its long-form receptor (LEPR) have been identified in the porcine ovary, their direct roles in mediating corpus luteum (CL) function in pregnant sows have not been clearly defined. In this study, we investigated leptin and LEPR expression in the porcine CL during pregnancy and evaluated the effect of the hormone on CL function in vitro. Leptin and LEPR were continuously expressed in the CL throughout pregnancy, and their expression patterns were generally similar, with higher levels in the early and middle stages of pregnancy and lower levels in the late stage. Immunohistochemical analysis revealed that both leptin and LEPR were predominantly localized in the luteal cells, with strong immunostaining observed in the early and middle stages CL and weak immunostaining in the late stage. Leptin 1–100 nM concentrations significantly increased the viability of cultured luteal cells (P < 0.05) and promoted their release of progesterone (P4) in a dose-dependent manner. Furthermore, leptin attenuated the prostaglandin F_2α (PGF_2α)-induced decreases in cell viability and P4 release. Additionally, leptin was found to have stimulatory effects on luteinizing hormone (LH) and prostaglandin E₂ (PGE₂) release but an inhibitory effect on PGF_2α secretion. In conclusion, the presence of leptin and LEPR in the CL and the stimulatory effects of the hormone on the viability of luteal cells and their release of P4, LH, and PGE₂ suggest that leptin has a positive regulatory effect on CL function in pregnant sows.