Effects of D-glucose concentration, D-fructose, and inhibitors of enzymes of the pentose phosphate pathway on the development and sex ratio of bovine blastocysts.
D-glucose at 5.6 mM reduces the progression of in vitro-produced (IVP) bovine embryos from the morula to the blastocyst stage and skews sex ratio towards males. Possibly, the presence of two transcriptionally active X-chromosomes compromises female embryo development through imbalance in glucose metabolism. Here, we have determined the threshold of embryo sensitivity to glucose, whether substitution of D-fructose for glucose reduces the selective loss of female embryos, and whether inhibition of an X-linked gene product, glucose 6-phosphate dehydrogenase (G6PD), normalizes sex ratio among bovine blastocysts. IVP zygotes were cultured in glucose-free medium to 72 hr post-insemination, at which time 8-cell embryos were selected for treatment and cultured until 144 hr post-insemination. Addition of 4 mM glucose at the 8-cell stage reduced (P < 0.05) the number of blastocyst that formed, whereas 2.5 and 1 mM glucose had no effect. Sex ratio in the presence of 4 and 2.5 mM glucose differed significantly from 0.5, while 1 mM glucose had no effect. D-fructose (5.6 mM) did not compromise development to blastocyst and did not alter the sex ratio of blastocysts that formed. When G6PD inhibitors (dehydroepiandrosterone: DHEA and 6-aminonicotinamide: 6-AN), which effectively inhibit the reduction of the NADPH-sensitive dye, brilliant cresyl blue (BCB) in bovine morulae, were added to the culture medium containing 4 mM glucose, embryo development was moderately reduced, but sex ratio skewing was corrected (with 6-AN) or lowered (with DHEA). In conclusion, glucose above 2.5 mM impairs bovine embryo development and increases sex ratio, most likely as a result of increased pentose-phosphate (PP) pathway activity in female embryos.
Kimura
Koji
K
University of Missouri, Department of Animal Sciences, 105 Life Sciences Center, Columbia, MO 65211, USA. kimurak@affrc.go.jp
Spate
L D
LD
Green
M P
MP
Roberts
R Michael
RM
D000818:Animals; D001755:Blastocyst / Q000187:drug effects* / Q000378:metabolism; D002417:Cattle; D003687:Dehydroepiandrosterone / Q000494:pharmacology; D046149:Embryo Culture Techniques; D047108:Embryonic Development / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D005632:Fructose / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology*; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D009028:Morula / Q000187:drug effects / Q000378:metabolism; D010078:Oxazines; D010427:Pentose Phosphate Pathway / Q000187:drug effects*; D012744:Sex Ratio; D013194:Staining and Labeling
D004791:Enzyme Inhibitors; D010078:Oxazines; D005632:Fructose; D003687:Dehydroepiandrosterone; C006797:Brilliant Cresyl Blue; D005954:Glucosephosphate Dehydrogenase; D005947:Glucose