Effects of glucose refeeding and glibenclamide treatment on glucokinase and GLUT2 gene expression in pancreatic B-cells and liver from rats.
The mutual role of glucose and insulin in the regulation of glucokinase and GLUT2 glucose transporter gene expression in pancreatic B-cells and liver has been studied in vivo in the rat. Glucokinase mRNA was quantified by competitive reverse-transcriptase PCR analysis, and GLUT2 mRNA by Northern-blot analysis in total RNA fractions. As in the liver, glucokinase mRNA decreased by 64% in pancreatic B-cells after starvation for 2 days and was induced 3-fold by short-term treatment (1 h) of the rats with oral glucose (4 g/kg body wt.). In contrast the sulphonylurea compound glibenclamide (0.1 mg/kg body wt.) did not significantly stimulate glucokinase gene expression in pancreatic B-cells. But glibenclamide caused a 4-fold increase of glucokinase mRNA in liver which was abolished by concomitant administration of diazoxide, a drug which antagonizes glibenclamide stimulated insulin secretion. GLUT2 gene expression was decreased by 50% in pancreatic B-cells and liver after starvation of the rats for 2 days. Neither short-term treatment (1 h) with glucose nor glibenclamide resulted in a significant increase of GLUT2 gene expression in pancreatic B-cells and liver. The results suggest that it is glucose which stimulates glucokinase gene expression in pancreatic B-cells whereas the transcriptional regulation of the glucokinase gene in liver is directed by insulin.
Tiedge
M
M
Institute of Clinical Biochemistry, Hannover Medical School, Germany.
Lenzen
S
S
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D003981:Diazoxide / Q000494:pharmacology; D005215:Fasting; D015971:Gene Expression Regulation, Enzymologic; D005941:Glucokinase / Q000235:genetics*; D005947:Glucose / Q000378:metabolism*; D051273:Glucose Transporter Type 2; D005905:Glyburide / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000201:enzymology*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar
D017931:DNA Primers; D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; D005941:Glucokinase; D005947:Glucose; D003981:Diazoxide; D005905:Glyburide