Koyama H, Ikeda S, Sugimoto M, Kume S
Laboratory of Animal Physiology and Functional Anatomy, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
Reprod Domest Anim. 2012 Dec;47(6):921-7. doi: 10.1111/j.1439-0531.2012.01992.x. Epub 2012 Feb 7.
The development of mammalian pre-implantation embryos is inhibited by heat stress, and the inhibitory effect is associated with excess reactive oxygen species (ROS). Folate is a nutrient with various physiological functions including antioxidative effects. We first investigated the transcript expression for 10 enzymes in the cycle of folate metabolism (folate-methionine cycle) in mouse embryos at the 1-cell, 2-cell, 4- to 8-cell, morula and blastocyst stages using reverse transcription-polymerase chain reaction. All of the transcripts were consistently expressed, except for Mat1a, which was not detected from the 4- to 8-cell stage onward. Next, the effects of folic acid (the synthetic form of folate) on the development and ROS levels of heat-stressed embryos were investigated. One-cell mouse embryos were cultured with or without 1000 ng/ml folic acid basically at 38°C, and in the heat-stressed groups, embryos were exposed to 39.5°C/10 h/day on the first two days of culture. The heat stress significantly (p < 0.05) decreased blastocyst development and cell number and increased ROS levels compared to those in the group not subjected to heat stress; however, among the heat-stressed groups, blastocyst development and cell number were increased and the ROS level was decreased by the addition of folic acid. These results indicate that the mRNA of folate-methionine cycle enzymes are expressed in mouse pre-implantation embryos, suggesting they can independently utilize folate, and the inhibitory effects of heat stress on the development of mouse pre-implantation embryos are ameliorated by folic acid. The ameliorating effects of folic acid may be partly due to its antioxidative property.
热应激会抑制哺乳动物植入前胚胎的发育，且这种抑制作用与过量的活性氧（ROS）有关。叶酸是一种具有多种生理功能的营养素，包括抗氧化作用。我们首先使用逆转录-聚合酶链反应研究了小鼠胚胎在1细胞、2细胞、4至8细胞、桑葚胚和囊胚阶段叶酸代谢循环（叶酸-甲硫氨酸循环）中10种酶的转录本表达。除了Mat1a外，所有转录本均持续表达，Mat1a从4至8细胞阶段起未被检测到。接下来，研究了叶酸（叶酸的合成形式）对热应激胚胎发育和ROS水平的影响。将单细胞小鼠胚胎在基本为38°C的条件下培养，添加或不添加1000 ng/ml叶酸，在热应激组中，胚胎在培养前两天暴露于39.5°C/每天10小时。与未受热应激的组相比，热应激显著（p < 0.05）降低了囊胚发育和细胞数量，并增加了ROS水平；然而，在热应激组中，添加叶酸可增加囊胚发育和细胞数量，并降低ROS水平。这些结果表明，叶酸-甲硫氨酸循环酶的mRNA在小鼠植入前胚胎中表达，表明它们可以独立利用叶酸，并且叶酸可改善热应激对小鼠植入前胚胎发育的抑制作用。叶酸的改善作用可能部分归因于其抗氧化特性。
