Article

Diabetologia

, Volume 50, Issue 3, pp 682-689

First online:

Expression of the gene encoding the high-K m glucose transporter 2 by the early postimplantation mouse embryo is essential for neural tube defects associated with diabetic embryopathy

  • R. LiAffiliated withDevelopmental and Stem Cell Biology, Joslin Diabetes CenterDepartment of Medicine, Harvard Medical School
  • , B. ThorensAffiliated withDepartment of Physiology, Center for Integrated Genomics, University of Lausanne
  • , M. R. LoekenAffiliated withDevelopmental and Stem Cell Biology, Joslin Diabetes CenterDepartment of Medicine, Harvard Medical School Email author 

Abstract

Aims/hypothesis

Excess glucose transport to embryos during diabetic pregnancy causes congenital malformations. The early postimplantation embryo expresses the gene encoding the high-K m GLUT2 (also known as SLC2A2) glucose transporter. The hypothesis tested here is that high-K m glucose transport by GLUT2 causes malformations resulting from maternal hyperglycaemia during diabetic pregnancy.

Materials and methods

Glut2 mRNA was assayed by RT-PCR. The K m of embryo glucose transport was determined by measuring 0.5–20 mmol/l 2-deoxy[3H]glucose transport. To test whether the GLUT2 transporter is required for neural tube defects resulting from maternal hyperglycaemia, Glut2 +/ mice were crossed and transient hyperglycaemia was induced by glucose injection on day 7.5 of pregnancy. Embryos were recovered on day 10.5, and the incidence of neural tube defects in wild-type, Glut2 +/ and Glut2 −/− embryos was scored.

Results

Early postimplantation embryos expressed Glut2, and expression was unaffected by maternal diabetes. Moreover, glucose transport by these embryos showed Michaelis–Menten kinetics of 16.19 mmol/l, consistent with transport mediated by GLUT2. In pregnancies made hyperglycaemic on day 7.5, neural tube defects were significantly increased in wild-type embryos, but Glut2 +/ embryos were partially protected from neural tube defects, and Glut2 −/− embryos were completely protected from these defects. The frequency of occurrence of wild-type, Glut2 +/ and Glut2 −/− embryos suggests that the presence of Glut2 alleles confers a survival advantage in embryos before day 10.5.

Conclusions/interpretations

High-K m glucose transport by the GLUT2 glucose transporter during organogenesis is responsible for the embryopathic effects of maternal diabetes.

Keywords

Neural tube Diabetic pregnancy Diabetic embryopathy Embryo GLUT2 SLC2A2