Investigation of neuroendocrine effects of irisin hormone on puberty onset and reproductive system

It is known that exercise is an effective factor in puberty onset, endocrine system, reproductive system, and sexual dysfunction. However, the role of the irisin hormone, an adipomyokine that is released into the circulation in response to exercise, is not fully known. The main aim of this thesis study was to reveal the physiological role of the irisin hormone on pubertal maturation, components of the reproductive system, and sexual behavior. In addition, another important purpose of this study was to investigate the effectiveness of the irisin hormone in the treatment of antidepressant-induced sexual dysfunction. This thesis study consisted of two experimental stages. At the first experimental stage, the effectiveness of the irisin on the puberty onset and reproductive system was examined. Accordingly, irisin (100 ng/kg/day) was administered intraperitoneally to weaned female and male rats for about 10 weeks. As a result of the experimental studies, it was found that chronic irisin exposure led to delayed onset of puberty in female rats and did not affect the timing of puberty onset in male rats. It was also found that chronic irisin exposure played a stimulating role in spermatogenesis and caused histostructural changes in the ovarian and testicular tissues. Moreover, changes in reproductive hormones and neurotransmitter levels in the specific brain areas associated with the reproductive system occurred due to chronic irisin administration. As a result of all these changes, it was revealed that sexual motivation decreased in female rats and sexual motivation and performance increased in male rats. In the second experimental stage, the effectiveness of the irisin on sexual dysfunction was examined. Therefore, irisin (100 ng/kg/day for 4 weeks) was subcutaneously administered with mini-osmotic pumps in the female and male rats with paroxetine-induced sexual dysfunction. As a result of the experimental studies, it was determined that short-time irisin administration did not affect reproductive hormones, sperm parameters, ovarian and testicular tissues in rats. On the other hand, it was found that short-time irisin administration did not affect sexual motivation in female rats, but increased sexual motivation/performance in male rats. Additionally, it was observed that the histopathological changes in the ovarian and testicular tissues due to paroxetine exposure decreased with irisin administration. In the male rats, it was revealed that the negative effects of paroxetine exposure on testosterone levels and sperm parameters and its inhibitory effects on sexual behavior were eliminated with irisin administration. As a result, it was demonstrated, for the first time in this thesis study, that chronic irisin exposure delayed pubertal maturation and decreased sexual motivation in female rats. In male rats, on the other hand, it was determined that irisin had an androgenic potential and played a stimulating role in spermatogenesis and control of sexual behavior. In addition, it was revealed that irisin affected the neurotransmitter system and the application time of irisin had different effects on the hypothalamus-pituitary-gonadal axis. Furthermore, the results of this study showed that irisin can be a therapeutic agent in the treatment of antidepressant-induced sexual dysfunction. The results of our study demonstrate that irisin may have an important role in the mechanism of action of exercise on the reproductive system, and may also greatly contribute to understanding the relationship between irisin and the reproductive system.