Acute and chronic exposure of rat intestinal mucosa to dextran promotes SGLTI-mediated glucose transport.
BACKGROUND
The intestinal handling of dextran, an alpha-1,6-linked glucose polymer, is poor compared with starch, and some ingested dextran might therefore reach the lower small intestine. As luminal sugar up-regulates SGLT1 (sodium-dependent glucose transporter) locally, we report the effects of a dextran-enriched diet on jejunal and ileal brush border membrane (BBM) glucose uptake.


METHODS
Rats were maintained on a diet containing 65% maltodextrin or 32.5% maltodextrin + 32.5% dextran (10 kD or 40 kD) for 8-10 days, and the kinetics of phlorizin-sensitive [3H]-glucose uptake by purified BBM vesicles was determined.


RESULTS
Ingestion of 40-kD but not 10-kD dextran increased Vmax for jejunal and ileal glucose uptake (+64.3% and +61.8% respectively, both P < 0.02). The transport response to 40-kD dextran was in keeping with lower levels of expired H2 at the end of the feeding period. High-performance liquid chromatography (HPLC) analysis of luminal contents indicated extensive hydrolysis of ingested dextran. Finally, 3-h jejunal exposure to 40-kD dextran in vivo increased the Vmax for glucose uptake by jejunal BBM.


CONCLUSIONS
It is likely that increased SGLT1-mediated glucose uptake after short or longer term mucosal exposure to dextran results from luminal dextran per se or a hydrolysis product. The clinical implications of this up-regulation are discussed.
Department of Physiology, Royal Free Hospital School of Medicine, London, UK. esdeb@rfhsm.ac.uk
E S
ES
Debnam
E E
EE
Denholm
G K
GK
Grimble
D000208:Acute Disease; D000818:Animals; D000925:Anticoagulants / Q000032:analysis / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D001835:Body Weight; D002851:Chromatography, High Pressure Liquid; D002908:Chronic Disease; D003911:Dextrans / Q000032:analysis / Q000494:pharmacology*; D004435:Eating; D005947:Glucose / Q000378:metabolism*; D006859:Hydrogen / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology*; D007583:Jejunum / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009834:Oligo-1,6-Glucosidase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D051269:Sodium-Glucose Transporter 1
D000925:Anticoagulants; D003911:Dextrans; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; C495676:Slc5a1 protein, rat; D051269:Sodium-Glucose Transporter 1; D006859:Hydrogen; D012964:Sodium; D009834:Oligo-1,6-Glucosidase; D005947:Glucose