The role of L-carnitine in bovine embryo metabolism. A review of the effect of supplementation with a metabolic modulator on in vitro embryo production.

Early embryo development is driven first by the maternal RNAs and proteins accumulated during the oocyte's cytoplasmic maturation and then after the embryo genome activation. In mammalian cells, ATP generation occurs via oxidative pathways or by glycolysis, whereas in embryonic stem cells, the consumption of glucose, pyruvate, lipids, and amino acids results in ATP synthesis. Although the bovine embryo has energy reserves in glycogen and lipids, the glycogen concentration is deficient. Conversely, lipids represent the most abundant energy reservoir of bovine embryos, where lipid droplets-containing triacylglycerols are the main fatty acid stores. Oocytes of many mammalian species contain comparatively high amounts of lipids stored as droplets in the ooplasm. L-carnitine has been described as a cofactor that facilitates the mobilization of fatty acids present in the oocyte's cytoplasm into the mitochondria to facilitate ß-oxidation processes. However, the L-carnitine effects by addition to media in the in vitro produced embryos on the quality are highly disputed and contradictory by different researchers. This review's objective was to explore the effect that the addition of L-carnitine on culture media could have on the overall bovine embryo production in vitro, from the oocyte metabolism to the modulation of gene expression in the developing embryos.

Association of a genetic polymorphism in the BMPR-1B gene, and non-genetic factors with the natural prolificacy of the Colombian-haired sheep.

INTRODUCTION: Colombian-haired sheep (OPC) is a creole breed with very good adaptation to the tropical conditions of our country. In sheep, it has been shown that the litter size (LS) is associated with ovulation rate, the number of fertilized eggs, and embryo survival. Also, LS is determined by genetic and environmental effects. In this sense, the receptor 1B of bone morphogenetic protein (BMPR-1B) has been described as a genetic factor. Therefore, the aim of the present work was to characterize and associate the SNP C864T in the BMPR-1B gene with LS in the specific OPC biotypes Ethiopian and Sudan. MATERIALS AND METHODS: Reproductive history (LS, number of calving in the mother, identification of the father, conception year, and conception period) of 200 OPC sheep was assessed. Additionally, sheep were genotyped by sequencing for the SNP C864T. An association between LS, reproductive history, and C864T variation was performed using a GLM fixed-effect model. RESULTS: The frequency of the T allele (0.75 ± 0.03) was higher than that of the C allele (P<0.05). The genotypic frequencies were 0.55 ± 0.06, 0.38 ± 0.04, and 0.07 ± 0.01, for TT, TC, and CC, respectively. An average value of He (0.37 ± 0.03) and HWE (P=0.97) was found. The LS found was 1.45 ± 0.15. This varied, between biotypes, with number of calving in the mother, with the father, and at the time of conception (P <0.05). CONCLUSION: The LS varied between genotypes (P<0.05). The CC genotype was the most prolific (1.81 ± 0.4), followed by the heterozygous (1.45 ± 0.04) and the TT homozygous (1.09 ± 0.04). However, we did not find a variation between biotypes within the genotypes (P>0.05). In conclusion, the polymorphism target in the exon 9 of the BMPR-1B gene and non-genetic factors affected significantly the litter size in the OPC.

l-Carnitine Supplementation during In Vitro Maturation and In Vitro Culture Does not Affect the Survival Rates after Vitrification and Warming but Alters Inf-T and ptgs2 Gene Expression.

l-carnitine is a potent antioxidant used for in vitro culture systems. Controversial results have been reported using l-carnitine in culture medium at different stages of in vitro bovine embryo production. Cumulus-oocyte complexes (n = 843) were in vitro-fertilized and cultured and added (treatment group) or not added (control group) with l-carnitine. At day three of culture, each group was subdivided into two subgroups receiving no l-carnitine (group 1), 3.8 mM l-carnitine added during in vitro maturation (group 2), 1.5 mM added during the in vitro culture (group 3), and 3.8 mM and 1.5 mM added during the maturation and culture, respectively (group 4). At day 8, blastocyst embryos were examined for mitochondrial activity, the presence of lipid droplets, total cell number, gene expression, and cryotolerance by vitrification. The data were analyzed with a one-way analysis of variance. l-carnitine added in the late in vitro culture significantly reduced mitochondrial activity and lipid content, and upregulated ifn-τ and ptgs2 gene expression compared to controls (p < 0.05). l-carnitine supplementation did not significantly affect the embryo rate production or survival rate after vitrification and warming (p > 0.05). l-carnitine supplementation significantly improved embryo potential to develop viable pregnancies in agreement with a study reporting improved pregnancy rates.

L-carnitine supplementation in culture media improves the pregnancy rate of in vitro produced embryos with sexed semen from Bos taurus indicus cows.

The in vitro embryo production industry in the actual world presents some difficulties related to low embryonic production rates, a problem that could be associated with in vitro culture conditions that differed from the in vivo (oviductal) conditions, mainly related to cytoplasmic lipid accumulation. L-carnitine is known as a modulator of ß-oxidation in the developing embryo, as it has been demonstrated that it improves embryo quality without affecting the in vitro embryo production rate. The aim of the present work was to evaluate the effect of L-carnitine supplemented during the in vitro maturation and culture processes on the implantation rate of in vitro produced embryos. Supplementation with 3.8 mM of L-carnitine was used during in vitro maturation, and later, during late in vitro culture, it was added at 1.5 mM. A control group contained no L-carnitine supplementation. Bovine oocytes obtained by ultrasound-guided follicle aspiration from healthy Bos taurus indicus cows were matured, fertilized and cultured in vitro. Multiparous F1 (Bos taurus taurus × Bos taurus indicus) cows were used as recipients. Overall, 460 oocytes were processed in three independent replicates from in vitro maturation until day 8 of the in vitro culture. No significant difference was found between treatments of in vitro embryo production. However, pregnancy rate at days 45 and 72 was significantly higher in blastocysts derived from L-carnitine treatment (31.55 ± 9.78%) compared to the control group (18.68 ± 6.31%). In conclusion, addition of L-carnitine at 3.8 mM and 1.5 mM in the maturation, and culture medium after day 3 of in vitro production process, significantly improved pregnancy rate after embryo transfer.