Presentation Authors: Akiko Itoga*, Ximmin Zha, Yoshitaka Aoki, Yosuke Matsuta, Hideaki Ito, Osamu Yokoyama, Fukui, Japan
Introduction: Recent reports indicate that there may be a physiological link between hypogonadism and metabolic syndrome (MetS) (J Androl 2009, 30: 370). In fact, hyperinsulinemia and obesity inhibit testicular testosterone production (Nat Rev Endocrinol 2009, 5: 673). Male Otsuka Long-Evans Tokushima Fatty (OLETF) rats fed a normal chow show MetS. Tadalafil was suggested to increase testosterone levels in patients with erectile dysfunction (Clin Endocrinol 2004, 61: 382; J Sex Med 2008, 5:1482), We used OLETF rats as a model of MetS and LETO rats as a control to investigate the effect of tadalafil on the levels of testosterone and estradiol, and mounting behavior.
Methods: We treated 36-week-old male OLETF and LETO rats with oral tadalafil (100 Î¼g/kg/day) for 12 weeks, whereas the sham groups received only vehicle for 12 weeks. Before and after the 12-week tadalafil treatment, the serum levels of total and free testosterone and estradiol were compared among four treatment groups. Serum testosterone and estradiol levels were monitored with a rat ELISA kit. Copulatory disorder was examined by matching each rat to an estrous female.
Results: The testosterone level was significantly lower in the OLETF groups vs. the LETO groups at 36 weeks. After the 12-week tadalafil treatment, the levels of total and free testosterone were both significantly increased in the OLETF-tadalafil group vs. the OLETF-vehicle group, and also increased in the LETO-tadalafil vs. LETO- vehicle (Fig.1). Tadalafil treatment decreased the estradiol levels in both the OLETF and LETO rats (Fig2). A significant suppression of mounting behavior, that is, elongation of intromission latency, was found in OLETF rats, however, 12-week tadarafil treatment prevented the mounting ability from worsening.
Conclusions: Our results indicate that tadalafil treatment improved the sex hormone balance between testosterone and estradiol in a rat model of MetS. Tadalafil treatment might prevent the mounting ability from worsening for MetS patients.
Source of Funding: Nippon shinyaku Co.Ltd