Metabolism of glucose by human embryos

Abstract

Glucose turnover, as measured by CO2 production, lactate accumulation and carbon incorporation from [U-14C]glucose as sole energy substrate, was low on the 2nd day of culture of human embryos resulting from in-vitro fertilization but above that of unfertilized oocytes. In general, all parameters of metabolism increased substantially during the following 2 days of development but the rate of increase in lactate production was greater than that of CO2, especially between Days 3 and 4. Within developing embryos, no correlation was evident between the metabolic turnover of glucose and the method of patient stimulation, the morphological quality of embryos or the apparent rate of cleavage in culture. The results indicate that, before Day 3 of development, glucose is not effective as an energy source for the human embryo because of a blockade to glycolysis similar to that in mouse embryos.

A multi-sensor system for measuring bovine embryo metabolism

“…The observed increases in oxygen consumption, glucose uptake, and lactate production of bovine embryos as they progress toward the blastocyst stages are consistent with previous studies (Thompson et al, 1996; Guerif et al, 2013), and parallel the well-established increase in embryo energy demand as cell numbers increase (Hardy et al, 1989; Overstrom et al, 1992). The mean values of glucose and lactate flux in bovine embryos in the present study are similar to those previously reported for bovine (Thompson et al, 1996) and human embryos (Hardy et al, 1989; Wales et al, 1987). However, observed rates are lower than those reported for equine embryos (Lane et al, 1996) and bovine and human embryos incubated in lactate-free culture media (Guerif et al, 2013; Gott et al, 1990), suggesting variations due to both species and culture media composition.…”

Mitochondrial DNA copy number is regulated by DNA methylation and demethylation of POLGA in stem and cancer cells and their differentiated progeny

“…Glycolysis is also used in zygotes and preimplantation embryos, suggesting that ESCs rely on the same energy-generating pathway as their precursor cells. 42 , 43 , 44 ESCs can increase mtDNA copy number in a cell-specific manner during differentiation ensuring that specialised cells acquire the appropriate number of mtDNA copies to meet their specific requirements for OXPHOS-derived ATP. 6 Cancer cells have low mtDNA copy number and rely predominantly on aerobic glycolysis instead of OXPHOS, even under normoxic conditions, which also promotes a highly proliferative state.…”

What is the relationship between the metabolism of preimplantation embryos and their developmental competence?

“…Hexokinase may be regulated by compartmentalization Leese et al, 1993). Wales et al (1987) suggested the block to glycolysis in human embryos may be similar to that found in mouse embryos. Human embryos contain the full complement of glycolytic enzymes, although intracellular activities are unknown .…”