title: Utilization of endogenous fatty acid stores for energy production in bovine preimplantation embryos.
abstract: Although current embryo culture media are based on carbohydrate metabolism of embryos, little is known about metabolism of endogenous lipids. L-carnitine is a β-oxidation cofactor absent in most culture media. The objective was to investigate the influence of L-carnitine supplementation on bovine embryo development. Abattoir-derived bovine cumulus oocyte complexes were cultured and fertilized. Post-fertilization, presumptive zygotes were transferred into a basic cleavage medium ± carbohydrates (glucose, lactate and pyruvate) ± 5 mm L-carnitine and cultured for 4 days in vitro. In the absence of carbohydrates during culture, embryos arrested at the 2- and 4-cell stages. Remarkably, +L-carnitine increased development to the morula stage compared to +carbohydrates alone (P < 0.001). The beneficial effects of L-carnitine were further demonstrated by inclusion of carbohydrates, with 14-fold more embryos reaching the morula stage after culture in the +carbohydrates +L-carnitine group compared to the +carbohydrates group (P < 0.05). Whereas there was a trend for +L-carnitine to increase ATP (P = 0.09), ADP levels were higher and ATP: ADP ratio were 1.9-fold lower (main effect, P < 0.05) compared to embryos cultured in -L-carnitine. Therefore, we inferred that +L-carnitine embryos were more metabolically active, with higher rates of ATP-ADP conversion. In conclusion, L-carnitine supplementation supported precompaction embryo development and there was an additive effect of +L-carnitine +carbohydrates on early embryo development, most likely through increased β-oxidation within embryos.
authors.affiliation: The Robinson Institute, Research Centre for Reproductive Health, School of Paediatrics and Reproductive Health, University of Adelaide, Adelaide, SA 5005, Australia. melanie.mcdowall@adelaide.edu.au
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Sutton-McDowall
authors.forename: Deanne
authors.initials: D
authors.lastname: Feil
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Robker
authors.forename: Jeremy G
authors.initials: JG
authors.lastname: Thompson
authors.forename: Kylie R
authors.initials: KR
authors.lastname: Dunning
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001755:Blastocyst / Q000187:drug effects / Q000378:metabolism*; D002241:Carbohydrates / Q000494:pharmacology; D002331:Carnitine / Q000494:pharmacology; D002417:Cattle / Q000196:embryology*; D003470:Culture Media; D046149:Embryo Culture Techniques / Q000379:methods / Q000662:veterinary*; D047108:Embryonic Development / Q000187:drug effects; D004734:Energy Metabolism; D005227:Fatty Acids / Q000378:metabolism*; D010084:Oxidation-Reduction
chemical_list: D002241:Carbohydrates; D003470:Culture Media; D005227:Fatty Acids; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002331:Carnitine