Fertilization and early embryology: Comparison of pyruvate uptake by embryos derived from conception and non-conception natural cycles

Abstract

The uptake of pyruvate by human embryos derived from natural cycles in the first 24 h following fertilization was examined. Since only one egg was obtained and therefore only one embryo transferred to the woman, it was possible to relate pyruvate consumption by a particular embryo to the outcome of that cycle (pregnancy or no pregnancy). The results showed that embryos have a wide range of pyruvate uptake values (2-53 pmol/embryo/h) but that this variation was reduced significantly to an intermediate range of values in those embryos that were able to implant (10-30 pmol/embryo/h). An association was found between embryo morphology and pyruvate consumption. Morphologically good embryos were more likely to implant if they demonstrated an intermediate pyruvate uptake. However, poor embryos did not implant even if they had a pyruvate uptake of 10-30 pmol/embryo/h. No relationship was found between the type of infertility and pyruvate consumption of individual embryos. It is suggested that the ability of an embryo to implant is multifactorial and that both morphology and pyruvate uptake may be factors.

The quiet embryo hypothesis: Molecular characteristics favoring viability

“…If the ''quiet embryo'' hypothesis is correct, and embryo viability is associated with a reduced consumption of energy and biosynthetic precursors, this leads to the conclusion that protein accretion in viable embryos is efficiently directed toward creating the building blocks required for development of the early embryo, while nonviable embryos are devoting additional resources for other purposes (discussed below). This general conclusion is consistent with the data on amino acid (Houghton et al, 2002) and pyruvate (Connaghan et al, 1993;Turner et al, 1994) turnover by early human embryos, where the endpoints were blastocyst formation and ongoing pregnancy, respectively.…”

“…Those which develop successfully to the blastocyst stage have amino acid turnover values distributed within a lower range than those for embryos which fail to develop, that is, arrest (Houghton et al, 2002). Similarly, human embryos with a pyruvate consumption distributed in the mid to lower range are the most likely to give rise to a pregnancy following embryo transfer (Connaghan et al, 1993;Turner et al, 1994). On the basis of these and other data, Leese (2002) proposed that early embryo viability is best served by a metabolism that is ''quiet'' rather than ''active''.…”

Can embryo metabolism be used for selecting bovine embryos before transfer?

“…La [2,6,28,37]. In retrospective analysis, in vitro glucose uptake by day 10 0 in vivo-produced bovine blastocysts [28] and day 4 mouse blastocysts [6] was positively correlated with viability after transfer to recipient females.…”

Zygote serine decreased uptake from the fertilization medium is associated with implantation and pregnancy

“…Liquid chromatography (the separation technique in this study) is known to simplify sample preparation since it can function in any temperature and does not require sample volatility [16]. The MS technology has been successfully applied in a variety of biological fluids and tissues and has been used not only on metabolomics, but also on proteomics in the field of ART [42,43]. In regard to MS applied on embryo culture media, Marhuenda-Egea et al evaluated retrospectively 25 samples after day 3 embryo/s transfer using liquid chromatography coupled to mass spectrometry [36].…”