Expression pattern of glucose metabolism genes correlate with development rate of buffalo oocytes and embryos in vitro under low oxygen condition.

Abstract

This study evaluates the effect of low oxygen conditions (5 Vs 20%) on buffalo embryo development. Expression patterns of key glucose metabolism genes (HK, PFK, LDH, PDH, G6PDH and Glut1) were assessed in buffalo oocytes and embryos cultured at 5 and 20% oxygen and correlated with development rate. Maturation rate was observed by determining MII stages by Aceto-orcein method and blastocyst formation was observed at 7 day post insemination (dpi). Expression levels of genes were determined by real time PCR in oocytes / embryos at 5 and 20% O2. Oocyte maturation and blastocyst formation rates were significantly higher at 5% O2 as compared to 20% O2 (P < 0.05). The expression pattern of glycolytic genes (HK, PFK and G6PDH) indicated that oocytes and embryos under 5% O2 tend to follow anaerobic glycolysis and pentose phosphate pathways to support optimum embryo development. Under 20% O2, oocytes and embryos had high expression of PDH indicating higher oxidative phosphorylation. Further, less G6PDH expression at 20% O2 was indicative of lower pentose phosphate activity. Higher expression of LDH was observed in oocytes and embryos under 20% O2 indicating sub-optimal culture conditions. High Glut1 activity was observed in the oocytes / embryos at 5% O2, indicative of high glucose uptake correlating with high expression of glycolytic genes. The expression patterns of glucose metabolism genes could be a valuable indicator of the development potential of oocytes and embryos. The study indicates the importance of reduced oxygen conditions for production of good quality embryos.