Reproduction Abstracts

Free fatty acids are not only energy fuels but also signaling molecules. In fact, long-chain fatty acids (LCFAs) have been identified as the ligands for G protein-coupled receptor 40 and 120 (GPR40 and 120). We have previously observed that GPR120 mRNA is expressed in the mouse sperm head. Based on the result, we hypothesized that the LCFAs act as signaling molecules to regulate sperm motility through GPR120. The aim of present study is to clarify whether extracellular LCFAs act as the regulator of flagellar motility of the mouse sperm.

Sperm were obtained from the caudal epididymidis of the matured ICR mouse. Expression of GPR40 and 120 mRNA were observed by RT-PCR, and the localization of GPR120 were identified by the immunohistochemical method. Further, sperm motility was analyzed as the flagellar beat frequency and movement distance.

GPR120 mRNA expression was confirmed in sperm, but GPR40 mRNA expression was not observed. GPR120 protein was localized in the head and middle-piece of sperm. 20 min exposure of sperm to oleic acid, docosahexaenoic acid or GPR120 agonist GW9508 induced an increase in flagellar beat frequency and movement distance of sperm. On the other hand, the flagellar beat frequency and movement distance are decreased when sperm were exposed to palmitate. These results indicate that extracellular unsaturated LCFAs induce an increase in flagellar beat frequency and quicken movement speed, and extracellular saturated LCFAs decrease flagellar beat frequency and decelerate movement speed. In addition, the result of GW9508 suggests involvement of GPR120 to this sperm motility regulating mechanism.