Pyroglutamylated RFamide peptide 43: A putative modulator of testicular steroidogenesis

We have recently shown that QRFP and its receptor are predominantly expressed in germ cells, Sertoli cells and Leydig cells in mice testes.

The present study investigated the role of QRFP in testicular steroidogenesis in mice.

Both ex vivo and in vivo experiments were performed. For ex vivo, testicular tissues were cultured with 0, 10, 100 and 1000 nM QRFP, with or without hCG, for 6, 12 and 24 h, and media were used for testosterone assay. The hCG-stimulated testicular tissues were used for immunoblot of SF1, StAR, CYP11A1, 3β- and 17β-HSD. For in vivo, mice received bilateral intratesticular injection of saline or 0.3, 1 and 3nmol QRFP and were killed at 6, 12 and 24 h post-injection. Testosterone in serum was measured at above durations, while qRT-PCR of HMG-CoA synthase 1 and SR-B1 and immunoblot of steroidogenesis-related markers were performed at 24 h post-injection.

Testosterone production under basal and hCG-stimulated conditions increased in a time-dependent manner, and QRFP supplementation to testicular culture caused an increase and a decrease in hormone production. The effect of QRFP on testosterone production under hCG-stimulated culture or in vivo conditions at 6 and 24h was similar. At 6h, testosterone production increased at 10 and 100 nM and also at 0.3 and 1nmol QRFP, while it decreased at 1000 nM and 3 nmol doses. At 24 h, testosterone level decreased at lower concentrations (10 nM and 0.3 nmol) and thereafter increased at middle (100nM and 1nmol) and higher (1000 nM and 3 nmol) concentrations under both hCG-stimulated culture and in vivo.

QRFP induced production of testosterone by modulating steroidogenic machinery at optimal doses and durations. Further, findings of in vivo study indicate that QRFP besides directly regulating testicular steroidogenesis may also have modulated other factors which act together in a holistic manner to control steroidogenesis.