Role of pyroglutamylated RFamide peptide43 in germ cell dynamics in mice testes in relation to energy metabolism.

QRFP is a neuropeptide that regulates glucose homeostasis and increases insulin sensitivity in tissues. We have previously shown that QRFP and its receptor (GPR103) are predominantly expressed in germ cells and Sertoli cells, respectively, in mice testes. In the present study, we report that QRFP caused an increase in PCNA and a decrease in p27Kip1 expressions in the testis under both in vivo and ex vivo conditions. Besides, via an in vivo study, cell cycle analysis by FACS showed an increase in 2C cells and a decrease in 1C cells. QRFP also induced expression of GDNF and phosphorylation of Akt and ERK-1/2. Together these results suggest that QRFP has a proliferative effect on germ cells in mice testes, since it caused a proportional increase in the mitotic activity and the number of spermatogonial cells. Further, observations of increased expressions of STAT-3 and Neurog3 in treated mice suggest that QRFP treatment regulates priming of undifferentiated spermatogonia to undergo differentiation, while a decrease in c-Kit expression indicate that spermatogonia at this time point are in an undifferentiated state. In addition, QRFP administration also caused an increase in intratesticular levels of glucose and lactate, and in LDH activity accompanied by increased expressions of GLUT-3 and LDH-C in the testis. Also, the phosphorylation of IR-β and expressions of p-Akt and p-mTOR were increased under ex vivo conditions in testicular tissue. In conclusion, our findings suggest that QRFP treatment caused proliferation of germ cells independently from the hypothalamic-pituitary axis via regulation of testicular energy metabolism.