FIG. 5.

ffar2 and ffar3 knockout impairs SCFA-triggered GLP-1 secretion. A: GLP-1 secretion from primary colonic cultures from wild-type, ffar2^−/−, and ffar3^−/− mice. Mixed primary cultures from the colon from wild-type, ffar3^−/−, and ffar2^−/− mice were incubated in bath solution containing 10 mmol/L glucose together with acetate (1 mmol/L), propionate (1 mmol/L), and IBMX (100 μmol/L) as indicated (all n = 6). B: GLP-1 secretion from primary colonic cultures from wild-type, ffar2^−/−, and ffar3^−/− mice triggered by a 140 mmol/L cocktail of SCFAs and an osmotic control of 140 mmol/L NaCl. GLP-1 secretion in each well is expressed relative to the basal secretion (control) measured in parallel on the same day, and error bars represent 1 SEM. Effects of SCFAs in the absence (*P < 0.05, **P < 0.01, and ***P < 0.001) or presence (ΔΔP < 0.01 and ΔΔΔP < 0.001) of IBMX and effects of genotype (#P < 0.05, ##P < 0.01, and ###P < 0.001) were assessed for significance by two-way ANOVA with post hoc Bonferroni correction test. C–F: Expression of ffar3 (C), ffar2 (D), gcg (E), and pyy (F) mRNA in colonic tissue isolated from ffar3^−/− (n = 5) and ffar2^−/− (n = 5) mice and wild-type littermates (n = 6). Expression was normalized to that of β-actin in the same sample. Data are presented as geometric means, and the error bar was calculated from the log(base 2) data. Significance comparisons between genotypes were calculated by one-way ANOVA with a post hoc Dunnett test performed on the log(base 2) data: *P < 0.05 and ***P < 0.001. G: Content of active GLP-1 peptide in colonic tissue isolated from ffar3^−/− and ffar2^−/− mice and wild-type littermates. Active GLP-1 in colonic extracts was assessed by enzyme-linked immunosorbent assay and is expressed relative to sample protein assessed with a Bradford assay. Significance comparisons between genotypes (n = 6 each) were calculated by one-way ANOVA with a post hoc Dunnett test: *P < 0.05.