The effect of L-carnitine supplementation during in vitro maturation on oocyte maturation and somatic cloned embryo development.

The quality of the recipient cytoplasm was reported as a crucial factor in maintaining the vitality of SCNT embryos and SCNT efficiency for dairy cows. Compared with oocytes matured in vivo, oocytes matured in vitro showed abnormal accumulation and metabolism of cytoplasmic lipids. L-carnitine treatment was found to control fatty acid transport into the mitochondrial β-oxidation pathway, which improved the process of lipid metabolism. The results of this study show that 0.5 mg/ml L-carnitine significantly reduced the cytoplasmic lipid content relative to control. No significant difference was observed in the rate of oocyte nuclear maturation, but the in vitro developmental competence of SCNT embryos was improved in terms of increased blastocyst production and lower apoptotic index in the L-carnitine treatment group. In addition, the pregnancy rate with SCNT embryos in the treatment group was significantly higher than in the control group. In conclusion, the present study demonstrated that adding L-carnitine to the maturation culture medium could improve the developmental competence of SCNT embryos both in vitro and in vivo by reducing the lipid content of the recipient cytoplasm.