Experiments do not support a recent claim that glutamate formed from the amination of citric
acid cycle-derived α-ketoglutarate is a messenger in glucose-induced insulin secretion
(Maechler, P., and Wollheim, C.(1999) Nature 402, 685–689). Glucose, leucine, succinic
acid methyl ester, and α-ketoisocaproic acid all markedly stimulate insulin release but do not
increase glutamate levels in pancreatic islets. Increasing the intracellular glutamate levels to
10-fold higher than basal levels by adding glutamine to islets does not stimulate insulin …