Effect Of Insulin On Imprinted Genes Igf2 And H19 MRNA Expression Of Mouse Preimplantation Embryo

The present study was aimed to reveal the alterations of expression of the growth-related imprinted genes, H19 and Igf2 (insulin-like growth factor 2) in embryos and fetuses, after preimplantation exposure to insulin, and to reveal the molecular mechanisms involved in insulin stimulation the embryo development both in vivo and in vitro.1.In vitro experiment2-cell embryos were cultured in either 0 or 0.25μg/ml insulin to the blastocyst stage and then transferred into pseudo-pregnant recipient mice. Insulin exposure caused an significant increase in the cell number of blastocyst and an elevation in birth body weight. The ratio of the blastocyst cell number of insulin-exposed group was 9.34% higher than that of the control group; the birth body weight in insulin-exposed group was 16.1% higher than that of the control group (P<0.01, pair t-test) .Real-time reverse transcription-polymerase chain reaction analysis revealed that exposure of preimplantation embryos to insulin increased the mRNA expression of both Igf2 and H19 in blastocyst embryos and E14 fetuses. The mRNA expression of Igf2 of blastocyst in insulin-exposed group was 1.8 fold,of control group, and H19 was 2.2 fold of control group;the mRNA expression of Igf2 and H19 of E14 fetuses in insulin-exposed group were both 1.5 fold of control group.Our results demonstrated that exposure of preimplantation embryos to insulin increased the mRNA expression of both Igf2 and H19 in blastocyst embryos and E14 fetuses, and promoted the development of embryos.2. In vivo experimentMouse models of diabetes mellitus were induced by 150 mg·kg^-1 doses of STZ through intra peritoneal injection. Then the diabetic female mouse was mated to the normal male mouse. Total RNA of E14 fetuses were extracted. mRNA expression levels of Igf2/H19 in fetuses on E14 were detected using real-time PCR. Real-time reverse transcription-polymerase chain reaction analysis revealed that treated group decreased the mRNA expression of Igf2 in E14 fetuses. The mRNA expression of Igf2 in diabetic fetuses was 0.65-fold of control.And the birth body weight in STZ treated group was 27.0% lower than that of the control group (P<0.01). The present study provided the evidence that maternal diabetes(low serum insulin) alters the expression of imprinted genes, and affects fetal development.In conclusion, insulin stimulates preimplantation embryo development by acceleration the cavitation formation, increasing blastocyst number and birth body weight. The result demonstrated, that the mechanism of insulin's action may involve the increase of the expression of imprinted genes which contributes to the later fetal stages.