Reproduction, Fertility and Development
Volume 27 Number 4 2015
Oocyte and Embryo Metabolism
This review considers the forces that have driven research on egg and embryo metabolism. An early focus on basic research was followed by a period of neglect due to overemphasis on improving assisted conception techniques. Metabolism is now back centre stage and an integral part of exciting research to understand how embryos develop, with the goal of ensuring the ‘best start in life’.
Proper energy provision is the lifeblood of oocyte maturation that yields fertilisable ova with full developmental potential. This process involves complex interaction between carbohydrate, purine and fatty acid metabolic pathways fuelling nuclear maturation to MII and the cytoplasmic maturation necessary for developmental competence. An understanding of such metabolic relationships enables the optimisation of oocyte maturation media necessary to achieve these developmental endpoints.
This study investigated the influence of high glucose and lipid levels (as seen in obesity) on oocyte health. Both lipid and glucose treatments compromised embryo development and increased the activities of glucose fuel sensing (hexosamine biosynthetic pathway) and lipotoxicity responses (endoplasmic reticulum-stress, ER-stress). However, there were no additive effects when glucose and lipids were combined, and in the case of ER-stress markers, glucose partially recovered the effects of lipotoxicity.
Obesity is associated with compromised oocyte quality. This study examined lipids within human follicular fluid and oocytes to determine whether they are altered by obesity or associated with oocyte quality. The results show that the ovarian follicular environment, which surrounds and nourishes the oocyte, exhibits a distinct metabolite profile compared to blood; but do not reveal associations between these parameters on and IVF outcomes
RD14359Applying metabolomic analyses to the practice of embryology: physiology, development and assisted reproductive technology
Metabolomics technology permits non-invasive monitoring of multiple metabolites from a single embryo during in vitro culture. Applying metabolomics to the analysis of individual embryos from several species, we demonstrate species- and stage-specific differences in metabolism and significant metabolic differences between in vivo- and in vitro-produced embryos. These results provide an insight into the metabolic pathways used by embryos, and their relationship with embryo quality.
RD14310Ambient ionisation mass spectrometry for lipid profiling and structural analysis of mammalian oocytes, preimplantation embryos and stem cells
Lipid structural characterisation in single oocytes and preimplantation embryos is relevant for studies on cryopreservation, nutrition and the impact of culture on embryonic metabolism. In this paper, research on lipidomics of single oocytes and preimplantation embryos by ambient mass spectrometry is reviewed and discussed. This approach alone or in combination with other techniques can have a profound impact on the understanding of developmental biology and cell differentiation.
Perturbations in blastocyst metabolism compromise development of the subsequent fetus. Nutrient availability, oxygen concentration and the redox state of the blastocyst all affect the relative activities of specific metabolic pathways. Significantly, metabolism regulates more than ATP generation, with metabolites and cofactors representing important regulators of the epigenome, putting metabolism centre stage when considering interactions of the blastocyst with its environment.
RD14293Arginine increases development of in vitro-produced porcine embryos and affects the protein arginine methyltransferase–dimethylarginine dimethylaminohydrolase–nitric oxide axis
In vitro culture results in porcine embryos that are less developmentally competent compared to in vivo-produced embryos. Supplementing culture medium with an essential amino acid, arginine, improves embryo development in vitro and by affecting the NO–DDAH–PRMT axis. A better understanding of the metabolic response to additional arginine will help to improve the production of pig embryos for agriculture and biomedicine.
Deficiencies in one-carbon related substrates and/or cofactors, such as folate and vitamin B12, during the periconceptional period can lead to epigenetic alterations in DNA and associated proteins in developmentally important genes in the embryo. Such epigenetic modifications can negatively impact on the subsequent health of offspring. Appropriate parental nutrition during this period can obviate these effects, particularly in subjects carrying risk alleles.
Couples wishing to improve their chances when embarking on treatment with artificial reproductive technologies may turn to adjuvant therapies such as nutritional supplements. However, the practice of routine dietary supplementation prior to, and during in vitro fertilisation (IVF) treatment has not been subject to well-powered prospective randomised trials. Although the importance of nutrition in early pregnancy has been determined, further work examining specific nutrients is required before clinical advice can be given.
RD14455Do little embryos make big decisions? How maternal dietary protein restriction can permanently change an embryo’s potential, affecting adult health
Poor maternal nutrition around conception permanently changes embryo development, affecting growth and metabolism into adulthood, increasing chronic disease risk. Evidence suggests preimplantation embryos ‘assess’ maternal nutrient quality and ‘decide’ the optimal ‘strategy’ for emerging extra-embryonic lineages to improve nutrient delivery and protect the competitive fitness of offspring. However, if postnatal nutrition is plentiful, such adaptations promote adult cardiometabolic disease, a legacy from our beginnings, with healthcare implications.
RD14363Nutrition and maternal metabolic health in relation to oocyte and embryo quality: critical views on what we learned from the dairy cow model
Nutrition and maternal metabolic health affect oocyte and embryo quality. This review summarises the value of in vivo and in vitro animal models to explain decreased oocyte and embryo quality in metabolically compromised individuals, with an emphasis on the bovine model. The challenges of current in vitro models are highlighted and the difficulties in extrapolating in vitro results to the in vivo situation are discussed.
RD14285Dexamethasone treatment of pregnant F0 mice leads to parent of origin-specific changes in placental function of the F2 generation
Antenatal treatment of mothers with synthetic glucocorticoids like dexamethasone improves neonatal viability in preterm human infants but reduces birth weight and programs life-long, detrimental cardiometabolic traits in experimental animals. This study demonstrates that placental function is altered in the offspring of female mice that were overexposed to dexamethasone before birth by treatment of their mothers. The findings suggest that the placenta can contribute to the intergenerational inheritance of phenotypic traits induced by grandparental glucocorticoid exposure.
Embryonic health is a new theme in research and healthcare. We emphasise the importance of lifestyle of parents-to-be, which significantly contributes to embryonic health with short-term health consequences for reproduction and pregnancy, and long term for health during the life course. These individuals and healthcare professionals therefore should be adopting a life course approach using personalised lifestyle care by mHealth pregnancy platforms, such as www.slimmerzwanger.nl.
RD14251Adverse effects of obesity and/or high-fat diet on oocyte quality and metabolism are not reversible with resumption of regular diet in mice
Obesity is a global epidemic and has a significant adverse effect on human reproduction. The hypothesis of this study was that obesity impacts oocyte metabolism and its ability to undergo meiosis, but that this process may be reversible with dietary modification and weight reduction. Unfortunately in this model, these “life style” interventions did not reverse the adverse effect of diet and obesity on oocyte quality.