Sources of carbon in hepatic glycogen synthesis during absorption of an oral glucose load in humans.

The role of hepatic glycogen is central in the short-term storage and supply of glucose. In the studies described, both glucose and its precursors are labeled and their incorporation into hepatic glycogen is measured during absorption of an oral glucose load in humans. The measurements are accomplished using tracer-determined non-steady-state turnover techniques. Mobilization of newly formed glycogen is achieved by glucagon infusions. After ingestion of a 100-g glucose load in normal fasting (12 h) man, no more than 10 g of the glucose taken up by the liver is converted directly into glycogen. On the other hand, by measuring the uptake of 14C from 14CO2 into glycogen and correcting for Krebs cycle exchange of label, at least an additional 15 g of the glycogen formed can simultaneously be accounted for by new synthesis of glycogen from glucogenic precursors.