Glutamine supplementation to porcine embryo culture medium improves development, increases leucine consumption, and enhances mitochondrial activity. In cancer cells, glutamine has been implicated in the activation of mechanistic target of rapamycin complex 1 (mTORC1) to support rapid proliferation. The objective of this study was to determine if glutamine metabolism, known as glutaminolysis, was involved in mTORC1 activation in porcine embryos. Culture with 3.75 mM Gluta-MAX improved development to the blastocyst stage compared to culture with 1 mM GlutaMAX, and culture with 0 mM GlutaMAX decreased development compared to all groups with GlutaMAX. Ratios of phosphorylated to total MTOR were increased when embryos were cultured with 3.75 or 10 mM GlutaMAX, which was enhanced by the absence of leucine, but ratios for RPS6K were unchanged. As another indicator of mTORC1 activation, colocalization of MTOR and a lysosomal marker was increased in embryos cultured with 3.75 or 10 mM GlutaMAX in the absence of leucine. Culturing embryos with glutaminase inhibitors decreased development and the ratio of phosphorylated to total MTOR, indicating reduced activation of the complex. Therefore, glutaminolysis is involved in the activation of mTORC1 in porcine embryos, but further studies are needed to characterize downstream effects on development.glutamine, mechanistic target of rapamycin, porcine, preimplantation embryo
| INTRODUCTIONGlutamine is a versatile amino acid with several roles in porcine preimplantation embryo development. Petters et al. (1990) demonstrated that porcine one-and two-cell stage embryos could be cultured to the blastocyst stage in medium containing glutamine without glucose, pyruvate, or lactate, indicating that glutamine acts as an energy source to drive proliferation. As further support, glutamine consumption for the tricarboxylic acid cycle was shown to be consistent from the two-cell to blastocyst stages in in vitro-produced porcine embryos (Swain et al., 2002). Moreover, the presence of glutamine in porcine embryo culture medium reduced intracellular H 2 O 2 concentrations and DNA damage in Day 3 embryos, indicating a role of glutamine in redox regulation (Suzuki et al., 2007). Deep sequencing revealed that several transcripts related to glutamine transport and metabolism were upregulated in in vitro-produced porcine embryos compared to in vivo counterparts, potentially indicating a deficiency in the medium (Bauer et al., 2010). FollowingThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.