| With an advancing age,the reproductive capacity is reduced in females.Among others,the oxidative stress in individual tissues and organs is believed to be one of the main contributors to the aging process.Two factors have a larger impact on development of oxidative stress i.e.,increased ROS levels in tissues and organs and diminished antioxidant system.As for the antioxidants system,several selenoproteins have been shown to have an important antioxidant role.The selenium content is believed to be reduced during aging.Therefore,the purpose of the present study was to investigate the effects of dietary sodium selenite on the reproductive capacity in selenium deficient aging ICR mice.First,the 12 month-old ICR mice were fed a selenium-deficient diet(0.08 mg·kg-1 Se)for 14 days and then mice were randomly divided into three groups i.e.,selenium-deficient group(0.08 mg·kg-1 Se)and two selenium-treated groups(0.015 mg·kg-1 sodium selenite and 0.33 mg·kg-1 sodium selenite)and were fed respective diets for the next 42 days.In addition,the selenium content and total antioxidant capacity were detected in blood.Moreover,the number of follicles(HE),apoptosis level(TNUEL),GPX4 expression(IHC)Selenoprotein K expression(IF)were evaluated in ovarian tissue specimen.Meanwhile,m RNA relative expression(RT-q PCR)of antioxidant,anti-apoptosis,and other selenoprotein genes was analyzed.Some of the mice were induced to superovulate and then GV oocytes were collected and their in vitro developmental potential following parthenogenetic activation was evaluated.Following results were observed:(1)Following feeding with selenium-deficient diet for 14 days,and after 42 days of treatment,the blood selenium concentration and the total antioxidant capacity of 0.33 mg·kg-1 sodium selenite group showed significantly higher values compared to the selenium-deficient groups(P<0.05).(2)According to the observation of HE stained sections,the number of primordial follicles,primary follicles,secondary follicles in 0.33 mg·kg-1 sodium selenite group was significantly increased(P<0.05).(3)After in vitro maturation and parthenogenetic activation,the blastocysts rate of oocytes was significantly increased(P<0.05),and none of the embryos in the selenium-deficient group developed to hatched blastocysts.Additionally,rate of embryo development in 0.33 mg·kg-1 sodium selenite group was significantly increased(P< 0.05).(4)A significant difference was observed when compared to the 0.33 mg·kg-1 sodium selenite group in which a significantly lower rate of apoptosis was observed in the selenium-deficient and 0.15 mg·kg-1 sodium selenite groups(P<0.05).(5)After 42 days feeding with sodium selenite,the expression of selenoprotein K in 0.33 mg·kg-1 sodium selenite group was significantly higher than the selenium-deficient group(P<0.05).The expression of GPX4 in selenium-treated groups was significantly higher than the selenium-deficient group(P<0.05).(6)Meanwhile,m RNA relative expression of Gpx1,Gpx3,and Gpx4 in 0.33 mg·kg-1 sodium selenite group was dramatic increased.Similarly,m RNA relative expression of Selenof,Selenok,Selenom,in selenium-treated groups was significant increased(P<0.05),and 0.33 mg·kg-1 sodium selenite group was higher than the 0.15 mg·kg-1.And the m RNA relative expression of Bcl-2 in selenium-treated groups was dramatic reduced(P<0.05)and same to m RNA relative expression of p21 in 0.33 mg·kg-1 sodium selenite group(P<0.05).In summary,these results indicate that the addition of 0.33 mg·kg-1 sodium selenite in feed for 42 days can effectively alleviate the decline in blood selenium levels caused by aging,increase the blood total antioxidant capacity,and maintain ovarian reserve,ameliorate follicular development,improve oocyte quality,and enhance the embryo development potential,thereby improving the reproductive capacity of aging ICR mice.These effects were potentially linked to the reduced apoptosis level,up-regulated expression of some antioxidant selenoprotein genes,down-regulated the expression of apoptosis-related genes,and increased GPX4 protein expression. |
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