Takahashi Toshikiyo, Inaba Yasushi, Somfai Tamas, Kaneda Masahiro, Geshi Masaya, Nagai Takashi, Manabe Noboru
NARO Institute of Livestock and Grassland Science, Ikenodai 2, Tsukuba, Ibaraki 305-0901, Japan.
Reprod Fertil Dev. 2013;25(4):589-99. doi: 10.1071/RD11262.
High lipid content in embryos is associated with low freezing tolerance. This study assessed the effects of exogenous L-carnitine, an enhancer of lipid metabolism, on the in vitro development and freezing survival of bovine embryos. Also, effects on metabolic activity, reactive oxygen species (ROS) and apoptosis were investigated. Supplementation of embryo culture medium with 1.518 mM or 3.030 mM L-carnitine significantly increased the rates of zygote development to the blastocyst stage and blastocyst cell numbers whereas 6.072 mM of this compound did not improve embryo development. Survival rates after slow freezing of blastocysts were significantly higher when embryos were cultured in the presence of 1.518 mM or 3.030 mM L-carnitine compared with the control. A lower density of lipid droplets was detected in L-carnitine-treated blastocysts compared with the control. L-carnitine significantly reduced ROS levels in 2-cell embryos but did not reduce ROS levels at later stages. The apoptotic cell rate was not different between control and L-carnitine-treated blastocysts. L-carnitine significantly increased ATP levels in 2-cell embryos but not at the 8-cell or blastocyst stages. L-carnitine increased the expression of metabolism-related ATP6 and COX1 genes in blastocysts. In conclusion, L-carnitine supplementation enhanced lipid metabolism in embryos resulting in improved development and cryotolerance of bovine blastocysts produced in vitro.
胚胎中高脂质含量与低冷冻耐受性相关。本研究评估了脂质代谢增强剂外源性L-肉碱对牛胚胎体外发育和冷冻存活率的影响。此外，还研究了其对代谢活性、活性氧（ROS）和细胞凋亡的影响。在胚胎培养基中添加1.518 mM或3.030 mM的L-肉碱可显著提高合子发育至囊胚阶段的比率和囊胚细胞数量，而6.072 mM的该化合物则不能改善胚胎发育。与对照组相比，当胚胎在含有1.518 mM或3.030 mM L-肉碱的条件下培养时，囊胚缓慢冷冻后的存活率显著更高。与对照组相比，在经L-肉碱处理的囊胚中检测到的脂滴密度更低。L-肉碱显著降低了2-细胞胚胎中的ROS水平，但在后期阶段并未降低ROS水平。对照组和经L-肉碱处理的囊胚之间的凋亡细胞率没有差异。L-肉碱显著提高了2-细胞胚胎中的ATP水平，但在8-细胞或囊胚阶段则没有。L-肉碱增加了囊胚中与代谢相关的ATP6和COX1基因的表达。总之，补充L-肉碱可增强胚胎中的脂质代谢，从而改善体外生产的牛囊胚的发育和耐冻性。
