Gastric emptying of hexose sugars: role of osmolality, molecular structure and the CCK₁ receptor.
BACKGROUND
It is widely reported that hexose sugars slow gastric emptying (GE) via osmoreceptor stimulation but this remains uncertain. We evaluated the effects of a panel of hexoses of differing molecular structure, assessing the effects of osmolality, intra-individual reproducibility and the role of the CCK(1) receptor, in the regulation of GE by hexoses.


METHODS
Thirty one healthy non-obese male and female subjects were studied in a series of protocols, using a (13) C-acetate breath test to evaluate GE of varying concentrations of glucose, galactose, fructose and tagatose, with water, NaCl and lactulose as controls. GE was further evaluated following the administration of a CCK(1) receptor antagonist. Three subjects underwent repeated studies to evaluate intra-individual reproducibility.


RESULTS
At 250 mOsmol, a hexose-specific effect was apparent: tagatose slowed GE more potently than water, glucose and fructose (P < 0.05). Fructose (P < 0.05) also slowed GE, but with substantial inter-, but not intra-, individual differences. As osmolality increased further the hexose-specific differences were lost. At 500 mOsmol, all hexoses slowed GE compared with water (P < 0.05), whereas lactulose and saline did not. The slowing of GE by hexose sugars appeared to be CCK(1) receptor-dependent.


CONCLUSIONS
The effects of hexose sugars on GE appear related to their molecular structure rather than osmolality per se, and are, at least in part, CCK(1) receptor-dependent.
Little
T J
TJ
Section of Gastrointestinal Sciences, Manchester Academic Health Sciences Centre, Salford Royal NHS Foundation Trust, The University of Manchester, Salford, UK. tanya.little@adelaide.edu.au
Gopinath
A
A
Patel
E
E
McGlone
A
A
Lassman
D J
DJ
D'Amato
M
M
McLaughlin
J T
JT
Thompson
D G
DG
D000085:Acetates / Q000378:metabolism; D000328:Adult; D019540:Area Under Curve; D002245:Carbon Dioxide / Q000378:metabolism; D005260:Female; D005746:Gastric Emptying / Q000187:drug effects* / Q000502:physiology; D005772:Gastrointestinal Transit / Q000187:drug effects; D006601:Hexoses / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D010421:Pentanoic Acids / Q000494:pharmacology; D043886:Receptor, Cholecystokinin A / Q000037:antagonists & inhibitors / Q000502:physiology*; D015203:Reproducibility of Results; D013329:Structure-Activity Relationship
D000085:Acetates; D006601:Hexoses; D010421:Pentanoic Acids; D043886:Receptor, Cholecystokinin A; D002245:Carbon Dioxide; C103490:dexloxiglumide