Comparison between D-[3-3H]- and D-[5-3H]glucose and fructose utilization in pancreatic islets from control and hereditarily diabetic rats.
The metabolism of D-glucose and/or D-fructose was investigated in pancreatic islets from control rats and hereditarily diabetic GK rats. In the case of both D-glucose and D-fructose metabolism, a preferential alteration of oxidative events was observed in islets from GK rats. The generation of 3HOH from D-[5-3H]glucose (or D-[5-3H]fructose) exceeded that from D-[3-3H]glucose (or D-[3-3H]fructose) in both control and GK rats. This difference, which is possibly attributable to a partial escape from glycolysis of tritiated dihydroxyacetone phosphate, was accentuated whenever the rate of glycolysis was decreased, e.g., in the absence of extracellular Ca(2+) or presence of exogenous D-glyceraldehyde. D-Mannoheptulose, which inhibited D-glucose metabolism, exerted only limited effects upon D-fructose metabolism. In the presence of both hexoses, the paired ratio between D-[U-14C]fructose oxidation and D-[3-3H]fructose or D-[5-3H]fructose utilization was considerably increased, this being probably attributable, in part at least, to a preferential stimulation by the aldohexose of mitochondrial oxidative events. Moreover, this coincided with the fact that D-mannoheptulose now severely inhibited the catabolism of D-[5-3H]fructose and D-[U-14C]fructose. The latter situation is consistent with both the knowledge that D-glucose augments D-fructose phosphorylation by glucokinase and the findings that D-mannoheptulose, which fails to affect D-fructose phosphorylation by fructokinase, inhibits the phosphorylation of D-fructose by glucokinase.
Giroix
Marie Hélène
MH
Laboratory of Nutrition Physiopathology, Centre National de la Recherche Scientifique, UMR 7059, University of Paris 7, F-75251, Paris, France.
Scruel
Olivier
O
Courtois
Philippe
P
Sener
Abdullah
A
Portha
Bernard
B
Malaisse
Willy J
WJ
D000818:Animals; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D005632:Fructose / Q000378:metabolism*; D005941:Glucokinase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D007553:Isotope Labeling; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D010766:Phosphorylation; D051381:Rats; D011922:Rats, Mutant Strains; D011994:Recombinant Proteins / Q000378:metabolism; D012016:Reference Values; D012727:Sex Characteristics; D014316:Tritium
D011994:Recombinant Proteins; D014316:Tritium; D005632:Fructose; D005941:Glucokinase; D005947:Glucose