Fig. 1.

Peptones and amino acids stimulate GLP-1 secretion from small intestinal cultures.

(a) Peptones (5 mg/ml) from three different sources stimulated GLP-1 secretion from mixed primary cultures from murine small intestine. Cultures were incubated for 2 h under control conditions or in the presence of meat, milk or vegetable peptones. GLP-1 secretion in each well is expressed relative to the basal secretion (control) measured in parallel on the same day. Data represent the mean ± SEM. ***p  < 0.001 compared with controls by one way ANOVA followed by Dunnet's multiple comparison test. n represents the number of wells, 42 for controls and 31, 12 and 12 for peptones from meat, milk and vegetable source, respectively. (b) Peptones from meat show a dose dependent stimulation of GLP-1 secretion. Cultures were incubated for 2 h under control conditions or in the presence of 0.5, 5 or 50 mg/ml meat peptones. GLP-1 secretion in each well is expressed relative to the basal secretion (control) measured in parallel on the same day. Data represent the mean ± SEM. ***p < 0.001 compared with controls by one way ANOVA followed by Dunnet's multiple comparison test. n = 12 wells each for controls and peptones. (c) GLP-1 secretion stimulated by a range of amino acids and the dipeptide Gly-Sar, all tested at 20 mM. Data represent the mean ± SEM. ***p < 0.001 compared with controls by one way ANOVA followed by Dunnet's multiple comparison test. n represents the number of wells for each condition, 36 for controls, 24 for Gln, 15 for Ala, 9 for Leu, 18 for Phe and 12 for Gly-Sar.