The stimulation of insulin secretion by D-glyceraldehyde correlates with its rate of oxidation in islet cells.
D-Glyceraldehyde's capacity to mimic the effect of D-glucose on insulin secretion has not yet been sufficiently substantiated. It has been recently proposed, however, that they might act through different mechanisms in insulin-secreting tumoral cells. Therefore, we have performed a dose-related study of both the secretory and metabolic effects of D-glyceraldehyde on islets, which have been compared with those produced by D-glucose. D-Glyceraldehyde's capacity to stimulate secretion was paralleled in a dose-dependent manner by its rate of oxidation to 14CO2. Partial inhibition of D-glyceraldehyde oxidation by beta-iodoacetamide resulted in a proportional decrease in the secretory response. L-Glyceraldehyde, which was apparently very poorly oxidized by islets, did not stimulate secretion. The ratio of the maximum insulin responses D-glyceraldehyde and D-glucose (57%) correlated with the ratio of their respective maximum rates of oxidation (68%). At sub-maximal concentrations there was a potentiation of the secretagogue effects of the hexose by the triose, which was not apparent at a maximum effective dose of glucose. It is concluded that D-glyceraldehyde mimics the secretory effect of glucose because, similarly to the hexose, it is metabolized through islet aerobic glycolysis. The lower potency of D-glyceraldehyde as an insulin secretagogue than D-glucose is determined by the lower capacity of islets to oxidize the triose compared with the hexose. D-Glyceraldehyde, unlike D-glucose, is metabolized in islets to D-lactate. Alternative routes for the metabolism of D-glyceraldehyde might explain some of the secretagogue differences between the triose and the hexose.
Alcázar
O
O
Departamento de Bioquímica, Facultad de Medicina, Universidad Complutense, Madrid, Spain.
Giné
E
E
Qiu-Yue
Z
Z
Tamarit-Rodríguez
J
J
D000818:Animals; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D005985:Glyceraldehyde / Q000378:metabolism / Q000494:pharmacology*; D006019:Glycolysis; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar
D007328:Insulin; D005985:Glyceraldehyde; D005947:Glucose