Islet metabolism: recent acquisitions

Isolated pancreatic rat islets deprived of exogenous nutrients maintain a sustained rate of O2 consumption. Glucose exerts little effect upon the utilization of endogenous nutrients. It is proposed that, under physiological conditions circulating L-glutamine represents a major fuel to cover the basal energy expenditure of the islets. Exogenous L-glutamine, which is actively metabolized in the islets, also provides an adequate substrate for the reaction catalyzed by glutamate dehydrogenase. L-glutamine dramatically enhances insulin release evoked by those amino acids which cause allosteric activation of the latter enzyme, e.g. L-leucine or b(-)BCH.