Regulation of glycolysis in the mouse blastocyst during delayed implantation

Abstract

The rate of oxidation of glucose is reduced in mouse embryos in the prolonged free living phase associated with delayed implantation and increases when the embryos are reactivated by estrogen. To determine how these changes in metabolism are regulated, several aspects of glucose metabolism were evaluated in dormant and reactivated blastocysts: 1) Embryos were exposed to 14C-pyruvate in vitro and evolved 14CO2 was measured. It was found that the rate of production of CO2 was equal in the two types of blastocysts, suggesting that aerobic pathways are fully functional during delayed implantation. 2) Production of lactate in the presence of O2 was measured and a decrease of 30% was found in delayed implanting embryos, suggesting that the overall regulatory mechanism for glucose metabolism resides in the glycolytic portion of the pathway. 3) Capacity for uptake and phosphorylation of glucose was evaluated using 3H-2-deoxyglucose and was found to be equal in the two types of embryos. 4) Total amounts of the rate-controlling enzymes for glycolysis (i.e., hexokinase and phosphofructokinase) in lysates of delayed and reactivated embryos were found to be equal, indicating that amounts of these enzymes are not limiting in delayed implantation. 5) Lactate production, measured under anaerobic conditions, was found to be equal, demonstrating that it is not the capacity for glycolysis but a difference in the degree of allosteric inhibition that is responsible for reduced glucose oxidation in delayed implantation. 6) Levels of ATP, ADP, and hexose-6-phosphates were found to be consistent with allosteric inhibition of the glycolytic pathway at phosphofructokinase during delay and a release of this inhibition with reactivation.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulatory roles for mitochondria in the peri-implantation mouse blastocyst: possible origins and developmental significance of differential ΔΨm

“…Increased mitochondrial metabolism detected some hours after blastocyst reactivation could be a consequence of the reversal of this inhibition for the existing enzyme combined with translation from nascent phosphofructokinase transcripts (Hamatani et al 2004). Our finding of elevated levels of ATP in diapausing blastocysts supports the notion of allosteric inhibition advanced by Nieder and Weitlauf (1984). Changes in DCm (high to low) have been reported for early mouse and human embryos that develop abnormally or arrest prematurely in vitro (Wilding et al 2002, Acton et al 2004, are developmentally compromised after photosensitization of mitochondria stained with r123 (Thouas et al 2004), or undergo iatrogenically induced reductions in polarity under certain culture conditions (Van Blerkom et al 2003) or after cryopreservation (Ahn et al 2002.…”

“…The decreased energy requirement for diapausing mouse blastocysts results from significantly reduced levels of transcription, translation and protein phosphorylation, and the cessation of DNA replication and cell division , Weitlauf & Kiessling 1980, Hamatani et al 2004, Lopes et al 2004). Nieder and Weitlauf (1984) showed that diminished mitochondrial respiratory activity in diapausing mouse blastocysts is associated with significant elevation in cytoplasmic ATP content, and proposed that a constitutively high ATP content caused allosteric inhibition of phosphofructokinase and coincident reduction in glucose oxidation. Increased mitochondrial metabolism detected some hours after blastocyst reactivation could be a consequence of the reversal of this inhibition for the existing enzyme combined with translation from nascent phosphofructokinase transcripts (Hamatani et al 2004).…”

Metabolism of Preimplantation Embryo Development

“…For example, maternal diabetes, resulting in hyperglycemic conditions, may alter the gene expression pattern, hence development potential, of the preimplantation embryos (Fraser, Waite, Wood, & Martin, 2007;Jungheim & Moley, 2008). In addition, in many mammalian species, environmental cues and/or metabolic stress can and do elicit developmental pause, such as delayed implantation or embryonic diapause (McGowen, Erez, Romero, & Wildman, 2014;Nieder & Weitlauf, 1984). These and other studies show that the maternal environment strongly influences the developmental potential of the preimplantation embryo (Fleming et al, 2004;Thompson, Mitchell, & Kind, 2007;Watkins, Papenbrock, & Fleming, 2008).…”

Effects of metabolic substrates and ionic environment on in-vitro activation of delayed implanting mouse blastocysts

“…However, after 18 h in these con¬ ditions this energy reserve may be depleted, thus explaining the apparent dormancy of blastocysts in long-term culture without glucose and amino acids (Wordinger & Brinster, 1976;Van Blerkom et al, 1979;Naeslund, 1979). In addition, Nieder & Weitlauf (1984) (Medium E) did not prevent activation although the absolute increase in thymidine incorporation at 24 h was lower than in BMOC-3 with normal Na+. This is in disagreement with the findings of Van Winkle (1977,1981) in which the increase in labelled amino acid incorporation expected with activation was prevented by incubation in medium with 55 mM-Na+.…”