Glucose absorption from maltotriose and glucose oligomers in the human jejunum

The jejunal absorption of glucose from (1-4)-linked glucose oligomers including maltotriose has been compared with that from free glucose and sucrose in normal subjects. A steady-state perfusion technique in vivo was used to study proximal jejunal assimilation of isotonic sugar-saline solutions isocaloric with 140 mmol/l glucose. Endogenous alpha-amylase was excluded from the test segment by proximal balloon occlusion. The glucose oligomer mixture consisted mainly of maltotriose, maltotetraose, maltopentaose and maltoheptaose. Glucose absorption was significantly faster from maltotriose alone and from the glucose oligomer mixture than from 140 mmol/l glucose controls, whereas glucose absorption from 70 mmol/l sucrose was similar to that from 70 mmol/l glucose plus 70 mmol/l fructose. Hydrolysis in vivo of maltotriose, the oligomer mixture and sucrose were similar, indicating that capture of glucose released by brush border sucrose hydrolysis was less efficient than that associated with (1-4)-linked oligomer hydrolysis. This suggests that the stoichiometric relationship of the active hydrolysis sites for sucrose to the glucose transport system is less advantageous than that of active sites for maltose hydrolysis. Hydrolysis of oligomers larger than maltohexaose may be rate limiting for glucose absorption in the absence of luminal amylase activity.