Effect of Phenformin in nondiabetic humans. Estimation of glucose turnover rate and Cori Cycle activity

Glucose turnover and the rate of recycling of glucose carbon into glucose, before and after a two day course of Phenformin 100 mg./day, has been evaluated with the aide of C-6 labeled 14C glucose in the nondiabetic human subject. These studies providing a measure of true glucose turnover and utilizing each subject as his own control support earlier data on this aspect of the action of Phenformin that had been obtained with uniformly labeled glucose in two groups of nondiabetic subjects. Direct evidence of increased Cori Cycle activity as measured by the appearance of 14C label in the C-(1–5) moiety of glucose and the evidence that glucose turnover increased by a factor of 2x the increase in the rate of glucose recycling suggest that gluconeogenesis is stimulated when this drug is given to humans. Ancillary measurement of the rate of glucose oxidation before and after Phenformin shows a slight stimulation of this aspect of glucose metabolism in the nondiabetic human following the drug, a finding that is concert with an earlier demonstration of significant increases in glucose oxidation in diabetic subjects treated with Phenformin.