Pathways for glucose disposal after meal ingestion in humans

To characterize postprandial glucose disposal more completely, we used the tritiated water technique, a triple-isotope approach (intravenous [3-H-3] glucose and [C-14] bicarbonate and oral [6,6-H-2(2)]glucose) and indirect calorimetry to assess splanchnic and peripheral glucose disposal, direct and indirect glucose storage, oxidative and nonoxidative glycolysis, and the glucose entering plasma via gluconeogenesis after ingestion of a meal in 11 normal volunteers. During a 6-h postprandial period, a total of 98 g of glucose were disposed of. This was more than the glucose contained in the meal (similar to78 g) due to persistent endogenous glucose release (similar to21 g): splanchnic tissues initially took up similar to23 g, and an additional similar to75 g were removed from the systemic circulation. Direct glucose storage accounted for similar to32 g and glycolysis for similar to66 g (oxidative similar to43 g and nonoxidative similar to23 g). About 11 g of glucose appeared in plasma as a result of gluconeogenesis. If these carbons were wholly from glucose undergoing glycolysis, only similar to12 g would be available for indirect pathway glycogen formation. Our results thus indicate that glycolysis is the main initial postprandial fate of glucose, accounting for similar to66% of overall disposal; oxidation and storage each account for similar to45%. The majority of glycogen is formed via the direct pathway (similar to73%).