Investigation of irisin's role in pubertal onset physiology in female rats

The timing of pubertal development is closely related to metabolic status and energy reserves. It is thought that irisin, which is involved in the regulation of energy metabolism and is shown to be present in the hypothalamo-pituitary-gonadal (HPG) axis, may play a role in this process. In our study, we aimed to investigate the effect of irisin administration on pubertal development and HPG axis in rats.

36 female rats were included in the study were divided into 3 groups: 100 ng/kg/day irisin treatment group (irisin-100), 50 ng/kg/day irisin treatment group (irisin-50), and control group. On the 38th day, serum samples were taken to determine levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH), estradiol and irisin. Brain hypothalamus samples were taken to determine levels of pulsatile gonadotropin-releasing hormone (GnRH), kisspeptin, neurokinin-B, dynorphin (Dyn), and makorin ring finger protein-3 (MKRN3).

Vaginal opening and estrus were seen firstly in the irisin-100 group. At the end of the study, the highest rate of vaginal patency was found in the irisin-100 group. Hypothalamic protein expression levels of GnRH, NKB and Kiss1 in homogenates; serum FSH, LH, and estradiol levels were the highest in the irisin-100 group, followed by the irisin-50 and control groups, respectively. Ovarian sizes were significantly greater in the irisin-100 group compared to the other groups. The hypothalamic protein expression levels of MKRN3 and Dyn were the lowest in the irisin-100 group.

In this experimental study, irisin triggered the onset of puberty in a dose-dependent manner. Irisin administration caused the excitatory system to dominate in the hypothalamic GnRH pulse generator.