C-13 NMR-STUDY OF IGF-I-EFFECTS AND INSULIN-EFFECTS ON MITOCHONDRIA FUNCTION IN CULTURED BRAIN-CELLS

DEVELOPMENT of differential cell culture systems has facilitated the s tudy of cellular and physiological actions of growth factors. Here we report the novel effects of insulin and insulin-like growth factor (IG F)-I on energy metabolism in cerebral cortical neurones, astrocytes an d co-cultures thereof. Incorporation of label from [1-C-13]glucose int o lactate has been shown to involve both glycolysis and the tricarboxy lic acid cycle in astrocytes. Thus C-13 nuclear magnetic resonance spe ctroscopy was used to monitor mitochondrial function by measuring C-13 labelling of the C-2 position of lactate. It could be demonstrated th at insulin and IGF-I have similar effects on mitochondria but individu al effects on cytosolic glucose metabolism. Evidence is presented that IGF-I and insulin stimulate neurones to release factors affecting ast rocytic lactate production. Furthermore, lactate released from neurona l-astrocytic co-cultures was mostly of astrocytic origin, implicating the importance of lactate for neuronal metabolism.