Effects of L-Carnitine during IVM on oocyte quality, cumulus cell viability and embryonic development in pigs

L-carnitine (LC) plays an important role in lipid catabolism and protects cells from damage caused by reactive oxygen species (ROS) due to its antioxidant activity. The aim of this study was to evaluate the effects of different LC concentrations during in vitro maturation (IVM) of porcine oocytes on oocyte quality and cumulus-oocyte complex (COC) metabolism, as well as their subsequent impact on subsequent embryonic development. The cumulus-oocyte complexes (COCs) were matured in vitro for 44 h without LC (control) or with different concentrations of LC (0.6, 1.25 or 2.5 mg/mL) in supplemented Medium 199. The concentration of 0.6 mg/mL of LC significantly decreased the intracellular lipid content, the intracellular level of ROS, and the mitochondrial function without affecting the percentage of nuclear maturation or the total glutathione (GSH) concentration of the oocytes compared to the control. The different concentrations of LC used during IVM affected the cumulus cell (CC) viability. The concentration of 2.5 mg/mL of LC significantly decreased the nuclear maturation of the oocytes compared to the control. No significant differences between LC treatments and control were observed in post-IVF parameters. The addition of LC during IVM decreased cleavage rates, but it did not affect blastocyst rates, total cell number, or apoptosis; notably, hatched blastocysts were observed only in the LC-treated group. In conclusion, low concentration of L-carnitine during IVM of porcine oocytes significantly decreased the intracellular lipid content, the intracellular ROS level, the mitochondrial function and the viability of CC without affecting embryo development.