Release of glucagon-like peptide-1 (GLP-1) by carbohydrates in the perfused rat ileum

The effect of various carbohydrates on glucagon-like peptide-1 (GLP-1) release was studied in the in vivo perfused rat ileum. GLP-1 concentrations in the mesenteric venous effluent increased significantly after luminal perfusion with substrates of a sodium/glucose cotransporter ( d -glucose, d -galactose, methyl- α d -glucoside, and 3- O -methyl- d -glucose). d -Fructose induced a sodium-independent release of GLP-1. Carbohydrates like 2-deoxy- d -glucose and N -acetyl- d -glucosamine, which are not substrates of a luminal sodium/glucose or fructose transporter, did not affect GLP-1 release. Since methyl- α d -glucoside is not a substrate of the basolateral glucose transport mechanism and 3- O -methyl- d -glucose is not metabolized within intestinal cells, it is concluded that intracellular metabolism of carbohydrates and intracellular removal are not essential to induce GLP-1 secretion in rats.