• Citer

Hexose metabolism in pancreatic islets. Participation of Ca2+-sensitive 2-ketoglutarate dehydrogenase in the regulation of mitochondrial function

par Sener, Abdullah ;Rasschaert, Joanne ;Malaisse, Willy
Référence Biochimica et biophysica acta. Bioenergetics, 1019, 1, page (42-50)
Publication Publié, 1990

Article révisé par les pairs

• Accès en ligne
• Détails
• Contenu
• Statistiques

Résumé :

A rise in extracellular D-glucose concentration results in a preferential and Ca2+-dependent stimulation of mitochondrial oxidative events in pancreatic islet cells. The possible participation of Ca2+-dependent mitochondrial dehydrogenases, especially 2-ketoglutarate dehydrogenase, in such an unusual metabolic situation was explored in intact islets, islet homogenates and isolated islet mitochondria. In intact islets exposed to a high concentration of D-glucose, the removal of extracellular Ca2+ impaired D-[6-14C]glucose oxidation whilst failing to affect the cytosolic or mitochondrial ATP/ADP ratios. In islet homogenates, the activity of 2-ketoglutarate dehydrogenase displayed exquisite Ca2+-dependency, the presence of Ca2+ causing a 10-fold increase in affinity for 2-ketoglutarate. In intact islet mitochondria, the oxidation of 2-[1-14C]ketoglutarate also increased as a function of extramitochondrial Ca2+ availability. Moreover, prior stimulation of intact islets by D-glucose resulted in an increased capacity of mitochondria to oxidize 2-[1-14C]ketoglutarate. The absence of extracellular Ca2+ during the initial stimulation of intact islets impaired but did not entirely suppress such a memory phenomenon. It is proposed that the mitochondrial accumulation of Ca2+ in nutrient-stimulated islets indeed accounts, in part at least, for the preferential stimulation of mitochondrial oxidative events in this fuel-sensor organ.