Effects of D-mannoheptulose upon D-glucose metabolism in tumoral pancreatic islet cells.
D-[3H]mannoheptulose was recently reported to be poorly taken up by tumoral pancreatic islet cells of the RINm5F and INS-1 lines. We have now investigated the effects of D-mannoheptulose upon D-glucose metabolism in these two cell lines. D-mannoheptulose (1.0-10.0 mM) only caused a minor decrease of D-glucose metabolism in RINm5F cells, whether at low (1.1 mM) or higher (8.3 mM) D-glucose concentration. A comparable situation was found in INS-1 cells examined after more than 20 passages. In both cases, however, the hexaacetate ester of D-mannoheptulose (5.0 mM) efficiently inhibited D-glucose metabolism. In the INS-1 cells, the relative extent of the inhibitory action of D-mannoheptulose upon D-glucose metabolism increased from 12.4 +/- 2.6 to 38.3 +/- 3.8% as the number of passages was decreased from more than 20 to 13-15 passages, the latter percentage remaining lower, however, than that recorded in INS-I cells also examined after 13-15 passages but exposed to D-mannoheptulose hexaacetate (66.9 +/- 2.2%). These findings when compared to our recent measurements of D-[3H]mannoheptulose uptake, reinforce the view that the entry of the heptose into cells and, hence, its inhibitory action on D-glucose metabolism are dictated by expression of the GLUT2 gene.
Rasschaert
J
J
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
Kadiata
M M
MM
Malaisse
W J
WJ
D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D007515:Islets of Langerhans / Q000166:cytology*; D008356:Mannoheptulose / Q000494:pharmacology*; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D051381:Rats; D013997:Time Factors
D051272:Glucose Transporter Type 1; D051273:Glucose Transporter Type 2; D009004:Monosaccharide Transport Proteins; D008356:Mannoheptulose; D005947:Glucose