Background: After nutrient ingestion there is an early response of glucagon-like peptide 1 (GLP-1) immunoreactivity, although GLP-1 is mainly produced in endocrine cells from the lower gut (ileum and colon/rectum), suggesting that indirect stimulation is important after the ingestion of carbohydrates that are predominantly absorbed from the upper intestine.

Methods: To enable contact of sucrose with lower gut mucosa, sucrose was administered by mouth with and without the simultaneous ingestion of 100mg of the -glucosidase inhibitor acarbose to six normal healthy volunteers.

Results: There was an early increment in GLP-1 15min after sucrose ingestion. With acarbose, sucrose reached the colon approximately 120min after ingestion, as indicated by an increment in breath hydrogen exhalation (p < 0.0001), and GLP-1 release was prolonged (p < 0.0001). The sucrose-related increments in glucose, insulin, C-peptide, and gastric inhibitory polypeptide (GIP) and the suppression of glucagon were only marginally affected by acarbose administration.

Conclusions: GLP-1 release appears to be influenced by indirect mechanisms (early response after sucrose) and by direct luminal contact with lower gut mucosal endocrine cells (late response with acarbose).