In vivo hyperglycemia and its effect on Glut-1 expression in the embryonic heart.
BACKGROUND
Maternal diabetes exposes embryos to periods of hyperglycemia. Glucose is important for normal cardiogenesis, and Glut-1 is the predominant glucose transporter in the embryo.


METHODS
Pregnant mice were exposed to 6 or 12 hr hyperglycemia during organogenesis using intraperitoneal (IP) injections of D-glucose on gestational day (GD) 9.5 (plug = GD 0.5). Embryos were examined for morphology and total cardiac protein, and embryonic hearts were evaluated for Glut-1 protein and mRNA expression immediately after treatment (GD 9.75, GD 10.0), as well as on GD 10.5 and GD 12.5.


RESULTS
IP glucose injections were effective in producing sustained maternal hyperglycemia. Maternal hyperglycemia for 6 or 12 hr on GD 9.5, followed by normoglycemia, produced a decrease in overall size and total cardiac protein in embryos evaluated on GD 10.5 but no difference on GD 12.5. Cardiac Glut-1 expression was immediately upregulated in embryos exposed to 6 or 12 hr maternal hyperglycemia. On GD 10.5, cardiac Glut-1 expression was not different in embryos exposed to maternal hyperglycemia for 6 hr but was downregulated in embryos exposed for 12 hr. On GD 12.5, cardiac Glut-1 expression in embryos exposed to maternal hyperglycemia on GD 9.5 for 6 or 12 hr, followed by normoglycemia, was not different from controls. The temporal pattern was the same for Glut-1 protein and mRNA expression.


CONCLUSIONS
Hyperglycemia-induced alterations in Glut-1 expression likely interfere with balance of glucose available to the embryonic heart that may affect cardiac morphogenesis.
Joyner
Nia T
NT
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA. ntjoyner@unity.ncsu.edu
Smoak
Ida W
IW
D000818:Animals; D005260:Female; D015870:Gene Expression / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D006321:Heart / Q000196:embryology*; D006943:Hyperglycemia / Q000378:metabolism*; D051379:Mice; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism*; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism
D051272:Glucose Transporter Type 1; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495678:Slc2a1 protein, mouse; D005947:Glucose