Hexose metabolism in pancreatic islets. Metabolic and secretory responses to D-fructose.
D-Fructose (3.3 to 33.0 mmol/liter) caused a concentration-related increase in insulin output from rat islets exposed to D-glucose (3.3 to 7.0 mmol/liter), such an increase not being more marked in mouse islets. The fructose-induced increment in insulin release, relative to that evoked by D-glucose, was two times higher in islets exposed to D-glucose than in islets stimulated by D-mannose, 2-ketoisocaproate, or nonnutrient secretagogs. Likewise, the metabolism of D-fructose in islet cells was significantly different in the absence or presence of D-glucose. Thus, the ketose was largely channeled into the pentose phosphate pathway in glucose-deprived, but not so in glucose-stimulated, islets. In both glucose-deprived and glucose-stimulated islets, however, the magnitude of the secretory response to D-fructose was commensurate with the increase in ATP production attributable to its catabolism. These findings indicate that the metabolic fate of hexoses--and, hence, their insulinotropic capacity--is not ruled solely at the level of their phosphorylation.
Sener
A
A
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
Malaisse
W J
WJ
D000818:Animals; D005632:Fructose / Q000378:metabolism / Q000494:pharmacology*; D005947:Glucose / Q000494:pharmacology; D006601:Hexoses / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007651:Keto Acids / Q000494:pharmacology; D007700:Kinetics; D008358:Mannose / Q000494:pharmacology; D051379:Mice; D051381:Rats; D013806:Theophylline / Q000494:pharmacology
D006601:Hexoses; D007328:Insulin; D007651:Keto Acids; D005632:Fructose; C013082:alpha-ketoisocaproic acid; D013806:Theophylline; D005947:Glucose; D008358:Mannose