Haploid Parthenotes Have Higher Demand for Glucose and Pyruvate Compared to Normally Fertilized Embryos During their In Vitro Development.

Haploid parthenogenetic embryos (HPEs) typically exhibit poor in vitro development, which may be attributed to the absence of paternal factors. Since the metabolic pattern determines the developmental potential of early embryos, the present study aimed to ascertain whether the compromised developmental potential of HPEs reflects distinct metabolic requirements compared to normally fertilized embryos (NFEs). The developmental trajectories and utilization of key metabolic substrates of HPEs and NFEs of Swiss albino mice were assessed by culturing them in M16 medium with varying concentrations of glucose (0-5 g/L) and pyruvate (0-90 mg/L). mRNA expression of glucose transporter-4 (Glut-4), glycolytic [glucose-6-phosphate dehydrogenase (G6pd) and pyruvate dehydrogenase (Pdha1)] and antioxidant [superoxide dismutase (Sod1), catalase (Cat), glutathione s- transferase (Gstcd) and glutathione reductase (Gsr)] enzymes were assessed at various developmental stages. Higher blastocyst rate was obtained when HPEs were cultured in elevated glucose (5 g/L) and pyruvate (54 mg/L) concentrations. Inhibition of glycolysis using 2-deoxy glucose resulted in high percentage of HPEs getting arrested at 2-cell stage, while NFEs were able to progress to 4-cell stage. Spent media analysis revealed that HPEs exhibit high glucose dependency compared to NFEs. Further, G6pd, Pdha1, Sod1 and Cat were upregulated, while Gsr and Gstcd were downregulated in HPEs. Our findings suggest that the HPEs have altered metabolic requirements compared to NFEs and provide an insight into the paternal contribution in regulation of metabolic pathways in early embryos. This study forms a basis for optimizing culture conditions for in vitro development of parthenogenetic embryos.