Glucose flux from dietary disaccharides: all sugars are not absorbed at equal rates

Considerable discrepancies exist in the literature regarding the rates of glucose absorption from the common dietary disaccharides, lactose, maltose, and sucrose. This study compared the unidirectional flux of glucose derived from dietary disaccharides with that of their constituent monosaccharides in vitro. Lactose-stimulated short-circuit current (Isc) and mucosal-to-serosal flux (Jm----s) were lower than that of an equimolar glucose-galactose mixture and were phlorizin inhibitable. Maltose- and glucose-stimulated Isc were similar, but Jm----s of glucose derived from the hydrolysis of maltose was lower than that of free glucose. Sucrose-stimulated Isc and Jm----s were similar to that of an equimolar glucose-fructose mixture. Isc and Jm----s of glucose from both maltose and sucrose were phlorizin and acarbose inhibitable. We conclude that the rate of glucose uptake from disaccharides is less than or equal to that of free glucose and is dependent on the glucose source. We speculate that regulation of glucose uptake from disaccharides can occur at three sites: the hydrolytic enzyme, the glucose transporter, and the tight junctions.