Study on the mechanism of sarsasapogenin in treating precocious puberty by regulating HPG axis

Abstract

Background Precocious puberty is a common endocrine disorder in children,and its pathogenic factor is early initiation of hypothalamic-pituitary-gonadal (HPG) axis. Sarsasapogenin is the main component of traditional Chinese medicine Zhimu, which has anti-fertility effect. There is already evidence that anti-fertility drugs may be resistant to precocity by regulating the HPG axis. Therefore, we speculated that sarsasapogenin might also has the effect. In order to test this hypothesis, this study determined the effect and mechanism of sarsasapogenin on precocious puberty by establishing a danazol-induced precocious puberty model. Methods Female Sprague-Dawley rats were divided into normal(N)group, model (M) group, leuprolide (L) group and sarsasapogenin (Sar) group. Rats at 5 days of age were given a single subcutaneous injection of 300 microgram of danazol dissolved in 25 microliter vehicle of ethylene glycol-ethanol (1:1, v/v), to establish the precocious puberty model. After 10 days of modeling, drug intervention was started. Vaginal opening was started at the age of 20 days, and then vaginal cell smears were examined. The development of uterus and ovary was observed by hematoxylin and eosin (HE) staining. The levels of Serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and estradiol (E2) were determined by radioimmunoassay. The expressions of hypothalamic gonadotropin releasing hormone (GnRH), Kiss-1, G protein-coupled receptor 54 (GPR54) and pituitary gonadotropin releasing hormone receptor (GnRH-R) were detected by RT-PCR. Results The day of vaginal opening was significantly advanced in the M than that in the N group. Compared with the M group, the Sar and L groups could significantly delay the opening time of vaginal (P < 0.001,P < 0.05,respectively). The Sar group could significantly decrease uterine and ovarian coefficients, and reduce uterine wall thickness (P < 0.05, respectively). In terms of serum hormones (LH, FSH, E2), the M group was significantly higher than the N group (P < 0.001,respectively). Moreover, the Sar group can significantly down-regulate the levels of serum hormones (P < 0.001, P < 0.01, P < 0.01,respectively). Also, the expression of GnRH, GnRH-R, Kiss-1 mRNA were significantly decreased in the Sar group compared with that in the M group (P < 0.01, P < 0.05, P < 0.001, respectively). Conclusions The results showed that sarsasapogenin had the effect of treating precocious puberty, and its mechanism might be to down-regulate the expression of GnRH and GnRH-R mRNA through the Kiss-/GPR54 system, thus delaying the initiation of HPG axis.