411
The effects of α-lipoic acid on oxidative stress during pig oocyte maturation
The effects of α-lipoic acid on oxidative stress during pig oocyte maturation
Polyspermic penetration (polyspermy) of pig oocytes is a persistent problem for producers and researchers during in vitro fertilization (IVF). The objective of this study was to reduce the occurrence of polyspermy by improving the maturation conditions of oocytes through supplementation of α-lipoic acid (ALA). Oocytes (n=250) were supplemented during the last 24 h of maturation with 50, 100, or 150 μM ALA and then subjected to IVF and embryo culture. After IVF, a portion of the embryos were evaluated for penetration, polyspermy, and male pronuclear formation rates. The remaining embryos were evaluated 48 h after IVF for cleavage and 144 h for blastocyst formation. There were no significant differences between treatment groups with respect to penetration, polyspermy, and male pronuclear formation rates. Oocytes supplemented with 100 μM ALA had significantly higher (P < 0.05) cleavage rates (82.35 ± 23.62%) by 48 h after IVF compared to the other levels of ALA supplementation and a significantly higher percentage (P < 0.05) of embryos reaching the blastocyst stage of development (47.06 ± 16.73%) by 144 h after IVF compared to all other groups. Oocytes were then supplemented with 100 μM ALA during the last 24 h of maturation and catalase, superoxide dismutase, and nuclear DNA fragmentation levels were determined at the end of maturation. There were no significant differences in superoxide dismutase activity levels or the number of oocytes with fragmented nuclear DNA at the end of maturation between treatment groups. Oocytes supplemented with 100 μM ALA had significantly lower (P < 0.05) levels of catalase activity (0.13 ± 0.12 units/oocyte) compared to oocytes that were not supplemented with 100 μM ALA (0.37 ± 0.10 units/oocyte). These results indicate that supplementing 100 μM ALA during the later stages of maturation improves embryo development by increasing cleavage and blastocyst rates 48 and 144 h after IVF, respectively.
Keywords: polyspermy, pig, oocyte