Cori cycle contribution to plasma glucose appearance in man.

The contribution of recycled glucose to gluconeogenesis and plasma glucose appearance (Cori cycle) has previously been calculated from liver balance studies and from infusions of labeled glucose. Both techniques resulted in the estimate that Cori cycle activity accounts for about 15% of plasma glucose appearance. However, it is now understood that the specific activity of gluconeogenic precursors, which is used to determine their contribution to glucose appearance in plasma, overestimates the true precursor specific activity. Using earlier published data on substrate utilization and glucose turnover kinetics in humans, an empiric correction factor of 2.7 is derived which may approximately account for label dilution in the precursor pool. Use of this factor confirms that the former estimate of the contribution of Cori cycle activity to glucose turnover should be revised substantially upwards.