Synergistic Effect of Insulin on <i>in vitro</i> Development of Immature Bovine Oocytes

Abstract

Problem statement: Development of efficient culture system to support embryonic development would be valuable when quality of produced embryos was important. However, the rate of bovine embryo production in vitro was still lower than expected. Present study, including of three experiments, was carried out to investigate the effect of insulin on nuclear maturation and subsequent development of immature bovine oocytes and in vitro fertilized embryos. Approach: Grade one cumulus-oocyte-complexes harvested from slaughterhouse ovaries were selected and randomly allocated in each treatment groups. In experiment 1, in vitro maturation medium (Hepes-buffered medium 199 + fetal calf serum + gonadotrophins + antibiotics) supplemented with 0 (control), 1, 10, 20 and 100 µg mL −1 of insulin. In experiment 2, to eliminate the effect of serum and hormones, Hepesbuffered medium 199 was supplemented with 1 mg mL −1 polyvinyl alcohols (PVA) and same levels of insulin. In experiment 3, the effect of insulin on bovine in vitro embryo development was assessed. Presumptive zygotes were randomly cultured in synthetic oviductal fluid added with 0 (control), 1, 10, 20 and 100 µg mL −1 of insulin. Results: In experiment 1, nuclear maturation and embryo development rates were significantly higher in 1 and 10 µg mL −1 compared with other groups (P<0.05). In experiment 2, both maturation and cleavage rate significantly increased in 1 and 10 µg mL −1 insulin.The only treatment resulted in higher hatchability was 10 µg mL −1 insulin (17.1±2.34%) compared with control (11.34±3.94). In experiment 3, cleavage and morula rates were significantly greater in 1 and 10 µg mL −1 insulin compared with other groups; although the highest rates resulted by using 10 µg mL −1 . Conclusion: Obtained results show that inclusion of 10 µg mL −1 insulin in maturation and culture medium exerted beneficial effects on nuclear maturation of bovine oocytes and in vitro embryo development till morula stage.

IMPACT OF INSULIN CONCENTRATION ON In vitro MATURATION OF RABBIT OOCYTES.

“…It has been shown that insulin (0.1-10 μg/ml) enhanced the mitosis of bovine granulosa cells and accelerated progression of meiosis in oocytes enclosed with cumulus cells. Both granulosa cells and oocyte normally express insulin receptor (Dashtizad et al, 2010). In accordance with the present results regarding the significant reduction in percentage of degenerated oocytes by 10 μg/ml insulin, Wasielak and Bogacki (2007) found that the incidence of apoptotic DNA degeneration was reduced by addition of insulin, insulin like growth factor I (IGF I) and other growth factors to the maturation medium.…”

“…The obtained data from the current study indicated an interaction effect between insulin and hormones (FSH, LH and E2) on embryonic stages atartig at M II. Similarly (Dashtizad et al, 2010) showed an interaction between insulin and FSH/or E2 on the bovine COCs. Also, Suzuki et al (2006) reported that stimulating effect of insulin on the proliferation of bovine granulosa cells is synergistic with gonadotrophins.…”

“…When the maturation rate was expressed in term of oocytes reaching both TI+MII, insulin supplementation at a level of 5 µg/ml showed significantly (P<0.05) the best improvement on oocyte maturation (51.0%) as compared to other insulin level (45.5-47.6%) or the control medium (39.5%). The potential role of insulin level supplements on IVM of immature rabbit oocytes, in particular, at a level of 5 µg/ml was reported in bovine oocytes by Dashtizad et al (2010 ). who demonstrated that presence of 1 or 10 μg/ml insulin in the maturation media showed a positive effect on maturation and cleavage rates of bovine immature oocytes in vitro.…”

“…Therefore, the existence of FSH and E2 in the IVM medium might interfere the real effects of insulin on the maturation of bovine cumulus-intact oocytes. Insulin by itself had a positive effect on in vitro bovine embryo production system (Dashtizad et al, 2010). Furthermore, insulin increases progesterone and estradiol production by bovine granulosa cells in the presence of FSH (Spicer et al, 1993).…”

Scoping review of primary studies evaluating Bovine in vitro oocyte maturation and embryo development

“…After culturing oocytes in 0, 200, 800, and 2 000 pg/mL ghrelin during in vitro maturation of oocytes, Dovolou et al (73) found that ghrelin groups significantly suppressed blastocyst formation rates, whereas Dovolou et al (74) found no differences between the control, 200, and 2 000 pg/mL ghrelin groups, and fewer blastocysts were produced with 800 pg/mL than in the control group when the hormone was administered daily during the culture of zygotes. Dashtizad et al (75) reported that insulin at 10 μg/mL exerted beneficial effects on oocyte and embryo development up to the morula stage. E 2 and P 4 .…”