Intracellular site of insulin action: mitochondrial Krebs cycle.

Effect of insulin on the oxidation of carbons-1,4 and -2,3 of succinate and their incorporation into protein were studied in isolated rat hepatocytes and diaphragm muscle pieces. Oxidation of carbons-2,3 of succinate and their incorporation into hepatocyte protein were stimulated significantly by insulin. Insulin had only a trivial effect on 14CO2 formation from the carboxyl carbons of succinate. These data suggest that insulin affects only those carbons of succinate that are metabolized in the intramitochondrial Krebs cycle.