Exogenous γ-tocotrienol promotes preimplantation development and improves the quality of porcine embryos

γ-tocotrienol (GTT), an isomer of vitamin E, has been the subject of increasing interest due to its strong anti-oxidant effects. Therefore, in this study, the effects of GTT on blastocyst development, expression levels of reactive oxygen species (ROS) and apoptotic index were investigated in preimplantation porcine embryos. After in vitro maturation and fertilisation, porcine embryos were cultured for 6 days in porcine zygote medium 3 supplemented with or without GTT (200μM) under oxidative stress conditions (200μM hydrogen peroxide (H₂O₂)). Blastocyst development was significantly improved in the GTT-treated group when compared with the H₂O₂-treated group (P<0.05). Subsequent evaluation of the intracellular levels of ROS and numbers of apoptotic nuclei in GTT-treated blastocysts revealed that ROS levels of GTT-treated porcine blastocysts were decreased (P<0.05) and the numbers of apoptotic nuclei were reduced by GTT treatment in porcine embryos. Moreover, the total cell numbers of blastocysts were significantly increased in the GTT-treated group relative to the untreated group under H₂O₂-induced oxidative stress (P<0.05). The expression levels of apoptosis-related genes (BCL-XL, BAX) in GTT-treated blastocysts were then investigated using real-time reverse transcription polymerase chain reaction. Expression of the anti-apoptotic BCL-XL gene was shown to be increased in the GTT-treated blastocyst group, whereas expression of the pro-apoptotic BAX gene was decreased. Taken together, these results suggest that GTT (200μM) under H₂O₂-induced oxidative stress, thereby improving the developmental competence of porcine embryos via modulation of intracellular levels of ROS and the apoptotic index during the preimplantation stage.