Genetic influence on the reduction in bovine embryo lipid content by L-carnitine

Abstract

The decreased rate of pregnancy obtained in cattle using frozen in vitro embryos compared with in vivo embryos has been associated with over-accumulation of intracellular lipid, which causes cell damage during cryopreservation. It is believed that the higher lipid content of blastomeres of bovine embryos produced in vitro results in darker-coloured cytoplasm, which could be a consequence of impaired mitochondrial function. In this study, l-carnitine was used as a treatment to reduce embryonic lipid content by increasing metabolism in cultured bovine embryos. We have observed previously that in vivo embryos of different dairy breeds collected from cows housed and fed under the same conditions differed in lipid content and metabolism. As such, breed effects between Holstein and Jersey were also examined in terms of general appearance, lipid composition, mitochondrial activity and gene expression. Adding l-carnitine to the embryo culture medium reduced the lipid content in both breeds due to increased mitochondrial activity. The response to l-carnitine was weaker in Jersey than in Holstein embryos. Our results thus show that genetics influence the response of bovine embryos to stimulation of mitochondrial metabolism.

Mitochondrial contributions to oocyte and embryonic quality in bovine

“…This higher lipid content is known to negatively affect survival to cryopreservation (Abe et al, 2002;Rizos et al, 2003). The higher lipid content in Jersey embryos is also correlated lower mitochondrial activity (Baldoceda et al, 2015a).…”

“…This lipid accumulation could be reflective of impaired mitochondrial functions limiting the rate of lipid metabolism. In support of this, breed differences have been described where embryos from Jerseys naturally contain more lipid droplets of smaller size than Holstein counterparts (Baldoceda et al, 2015a). This higher lipid content is known to negatively affect survival to cryopreservation (Abe et al, 2002;Rizos et al, 2003).…”

“…It was anticipated that this metabolic regulator could have the dual effects of reducing lipid content however that would do so would increase the level of the dangerous free radicals. Addition of L-carnitine to the bovine embryo culture medium significantly reduced lipid intracellular lipid content in embryos although the extent of response varied between individual embryos indicating that not all embryos could proceed to lipid catabolism with the same efficiency Furthermore, the impact of L-Carnitine was overall weaker and more variable in Jersey embryos (Baldoceda et al (2015a) which were already found to have a reduced mitochondrial activity Also, Baldoceda et al (2015b). This was also supported at the gene expression level where key genes involved in lipid management such as droplet size (perilipin-2) were differentially regulated in Jersey compared to Holstein.…”

Metabolic Regulation and Cryotolerance of In Vitro-Produced Holstein Embryos

“…Altering embryonic metabolism may provide a way to reduce this lipid accumulation and improve development rates as the embryos are rescued from oxidative stress (Absalón-Medina et al, 2014;Paschoal et al, 2012). These elevated lipid levels negatively influence cryotolerance; however, the exact mechanism by which this occurs is unknown (Abe, Yamashita, Satoh, & Hoshi, 2002;L. Baldoceda, Gagne, Ferreira, & Robert, 2015;Seidel, 2006).…”

“…Addition of L-carnitine to IVC medium has been shown to decrease intracellular lipid accumulation, improve blastocyst development rate, and decrease ROS in bovine embryos (L. Baldoceda et al, 2015;T. Takahashi et al, 2013).…”