2017 Volume 63 Issue 3 Pages 263-270
Sufficient generation of adenosine triphosphate (ATP) by oocytes is critical for fertilization and embryo development. The objective of this study was to determine the effects of supplementing media with L-carnitine, a co-factor required for the metabolism of fatty acids, during the peri-fertilization period on embryo development and energy generation. Firstly, in vitro matured (IVM) porcine oocytes were co-incubated with sperm in IVF medium supplemented with 0‒24 mM L-carnitine. The blastocyst formation rate of the control group was greater than those of the L-carnitine groups (P < 0.05), except for the 3 mM L-carnitine group. Subsequently, oocytes and/or sperm were treated without or with 3 mM L-carnitine for either the 1 h pre-IVF oocyte incubation; the pre-IVF sperm preparation; the first 30 min of IVF; or the entire 5.5 h of IVF. Despite similar fertilization rates among the groups, the cleavage rate of the pre-IVF oocyte group was significantly greater than those of the other groups, except for the pre-IVF sperm group. Additionally, the oocyte ATP content and the cryotolerance of the resulting blastocysts were examined following the pre-IVF oocyte treatment. Oocyte ATP content was also similar among the groups (P > 0.05). Following vitrification, the post-warming survival rate of blastocysts derived from L-carnitine-treated oocytes was greater than that of blastocysts derived from untreated oocytes (42.4% vs. 24.9%; P < 0.05). In conclusion, a 1 h oocyte exposure to 3 mM L-carnitine immediately prior to insemination enhanced cleavage and improved the cryotolerance of resulting blastocysts. While the findings are suggestive of a lipolytic action, further studies are required to clarify the contributions of lipid metabolism and oxidative mechanisms to the observed effects of the L-carnitine treatment.