難消化性デキストリンの耐糖能に及ぼす影響

第I報: 消化吸収試験および糖負荷試験による検討

抄録

It is widely acknowledged that high viscosity water-soluble dietary fibers such as pectin and guar gum affect a lowering of blood glucose levels and a reducing of insulin secretion following a sugar load. However, as dietary fibers vary in origin and in chemical properties, their physiological functions differ as well. In this study the effects of Indigestible Dextrin (PF-C), a low viscosity, water-soluble dietary fiber obtained through acid and heat-treatment of potato starch, on various aspects of sugar tolerance were examined.
First, the influence of PF-C on sucrose hydrolysis was examined in rat intestinal mucosa cell homogenate confirming that PF-C did not inhibit sucrase activity. Then, in order to investigate the influence of PF-C on sugar digestion-absorption, an experiment was performed by using the everted intestinal sac of the rat in vitro. PF-C did not have an effect on glucose-transport into the serosal medium, whereas PF-C did inhibit the transport of hydrolyzed-glucose from sucrose, with no change in the hydrolysis of sucrose.Recently, Crane et al. reported that there is a specific route for hydrolyzed glucose from sucrose in glucose-absorption on the enteric surface (disaccharidase related transport system). The possibility exists that PF-C specifically affects this pathway. Further, total glucagon released into the serosal medium stimulated by both glucose and sucrose were reduced by PF-C.
On the basis of these results, an oral sugar tolerance test was conducted in both rats and healthy human subjects. In male Sprague-Dawley rats (8 weeks old, 250-280g) concurrent administration of PF-C (0.6g/kg body weight) reduced an increase in plasma insulin levels with no change in glucose levels following a glucose (1.5g/kg body weight) load. Further noted were reductions in increases in both plasma glucose and insulin levels following a sucrose (1.5g/kg body weight) plus PF-C (0.6g/kg body weight) load to that of the sucrose (1.5g/kg body weight) single load. These findings reflect the above mentioned in vitro results. Moreover, in healthy male subjects the increase in both plasma insulin and glucagon-like immunoreactivity (Gut GLI) levels following a Trelan-G75 load were significantly reduced by concurrent administration of PF-C.
From these observations it would appear that the effectiveness of reducing insulin secretion by PF-C results due to the decrease in sugar absorption by inhibiting the disaccharidase-related transport system. As glucagon-like peptide 1 (GLP-1), [an incretin in the enteroinsular axis] secreted with Gut GLI from intestinal L cells, is known to enhance insulin secretion following a sugar load, the resulting effectiveness by PF-C to reduce insulin secretion is thought to be attributed to the action on this enteroinsular axis mechanism.