The in vitro effect of leptin on semen quality of water buffalo (Bubalus bubalis) bulls

The purpose of this study was to evaluate the probable effects of leptin addition in different levels to the semen extender on sperm quality (motility and motility parameters, viability, sperm membrane integrity, and DNA damage). Semen specimens were evaluated immediately after leptin addition, equilibration time and after thawing the frozen semen. Five healthy buffalo bulls (5 ejaculates from each bull) were used. Each ejaculate was diluted at 37 ˚C with tris-based extender containing 0 (control), 10, 20, 50, 100, and 200 ng mL-1 leptin. The diluted semen was kept 4 hr in refrigerator to reach to the equilibration time and then packed in 0.5 mL French straws and frozen in liquid nitrogen. Our results showed that, in the fresh semen, no significant difference was observed in all sperm quality parameters evaluated among all of the examined leptin concentrations. Addition of 10 ng mL-1 leptin into semen extender significantly preserved sperm motility, all of the motility parameters, and viability in equilibrated semen compared to that of control group. However, in vitro addition of 200 ng mL-1 leptin, significantly decreased theses parameters. In the frozen thawed semen, all leptin concentrations decreased sperm motility and viability, but significant decrease was observed in concentrations of 100 and 200 ng mL-1. Adding leptin to semen extender did not have any significant influence on sperm DNA damage and sperm membrane integrity in all examined groups. These findings suggest that in vitro addition of 10 ng mL-1 leptin could preserve sperm motility and viability in cooled semen of buffaloes.