Fig. 1: Expression of GLP-1 in rat and human stomach cells.

GLP-1-positive cells and mucosal GLP-1 content in the rat (a) and human (b) stomach. Representative immunostaining of GLP-1 in fundic mucosa sections from an HFD rat and an obese individual. Bar scale 100 µm. Arrows indicate GLP-1-positive cells. Insert: a high magnification of human fundic GLP-1-positive cells. Quantification of mucosal GLP-1 content from HFD obese rat stomach and colon mucosal scrapings (n = 6 rats) and from gastric biopsies (n = 15 for fundus and n = 16 for antrum) of obese candidates for bariatric surgery. Results are presented as scatter data plots with mean ± SEM of mucosal GLP-1 protein content. Each point corresponded to one obese subject. One-way ANOVA followed by Tukey’s multiple comparison test were used to analyze data in the rat (a), and Mann–Whitney test was used compare data in human (b). ***P < 0.001; NS not significant. c LC-MS/MS identification of GLP-1. Principal peptides identified in acid-ethanol gastric mucosa extracts from rat ileum and stomach are represented in green and blue, respectively. Red arrows show physiological cleavage sites by PC1/3. Identified peptides are further described in Supplementary Table 1. d Immunoreactivity of GLP-1, ghrelin, and somatostatin (SST) in stomach. Confocal analysis and representative photomicrographs of GLP-1 (red), ghrelin (green), and SST (green) positive cells in rat gastric mucosa. Nuclei were stained with Hoechst solution (blue). Bar Scale 20 µm. Note that the GLP-1-positive cells are also positive for ghrelin in the fundic mucosa and somatostatin in the antrum. Inserts: high magnification of these cells. Total (e) and active (f) GLP-1 contents in the rat stomach, ileum, and colon. Quantification of total and active GLP-1 content from lean rat stomach, ileum, and colon mucosal scrapings. Results are expressed as GLP-1 in pg/mg protein and presented as scatter data plots with mean ± SEM. Each point corresponded one rat with n = 10 for stomach and n = 9 for ileum and colon. Data were analyzed by a one-way ANOVA followed Tukey multiple comparison test *P < 0.05; ***P < 0.001; NS for not significant. Source data are provided as a Source data file.