Diabetes, Vol 41, Issue 1 22-25, Copyright © 1992 by American Diabetes Association
Upregulation of GLUT2 mRNA by glucose, mannose, and fructose in isolated rat hepatocytes
T Asano, H Katagiri, K Tsukuda, JL Lin, H Ishihara, Y Yazaki and Y Oka
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Previously, demonstrated that GLUT2 mRNA and protein are increased in liver
of streptozocin-induced diabetic rats. To examine the mechanisms whereby
GLUT2 mRNA is regulated, we cultured isolated hepatocytes in the absence
and presence of various concentrations of glucose. Culture of hepatocytes
in high glucose concentration (27.8 mM) for 20 h induced a 3.2-fold
increase in GLUT2 mRNA levels compared with hepatocytes cultured without
D-glucose. Interestingly, D-mannose and D-fructose could substitute for
D-glucose to elevate the GLUT2 mRNA level, whereas 3-O-methyl-D-glucose,
2-deoxy-D-glucose, and sucrose, which were not metabolized or taken up by
the cells, were without effect. Insulin had no significant effect on GLUT2
mRNA levels in hepatocytes in the presence or absence of D-glucose.
Therefore, the regulation of the GLUT2 gene by D-glucose in hepatocytes is
contrary to that reported for GLUT1 and GLUT4 genes, which are
downregulated by D-glucose. These results also suggest that the elevated
GLUT2 mRNA level observed in diabetic rat liver is due to the high blood
glucose concentration rather than to insulin deficiency.