Maternal insulin treatment improves pre-implantation embryo development in diabetic rats.

Pre-implantation embryos were recovered from control, diabetic and insulin-treated diabetic rats on day 5 of pregnancy. Compared to control animals, diabetic rats had a 20% reduction in the number of embryos per rat and blastocysts recovered from diabetic rats showed a 19% decrease in total cell number. The cellular decrease observed in blastocysts was mainly at the expense of the inner cell mass. Insulin replacement therapy was started on day 1 of pregnancy and normalized the glycaemia of diabetic rats but failed to raise the number of embryos per rat toward the control value. Insulin treatment, however, fully restored the normal cell number in both the inner cell mass and trophectoderm of blastocysts. The dead cell index, which was significantly elevated in the inner cell mass of blastocysts from diabetic rats, also returned to the control value following insulin treatment. Our data suggest that diabetes-induced impairment of pre-implantation development can be partly prevented by insulin treatment started shortly after conception.