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. 2019 Sep 26;10:2176. doi: 10.3389/fmicb.2019.02176

FIGURE 5.

FIGURE 5

SCFAs contribute to GLP-1 secretion via MAPK pathways in IECs. (A–C) Transcription levels of FFAR2 (A), FFAR3 (B), and GLP-1R (C) were assessed by qPCR in primary IECs treated with 3 mM acetate, 1 mM propionate, and 1 mM butyrate for 24 h (n = 8); (D) GLP-1 concentrations in the IECs culture medium after treatments of 3 mM acetate, 1 mM propionate, and 1 mM butyrate for 2 h, respectively (n = 8); (E) SCFAs-mediated activation of ERK, JNK and p38MAPK in IECs treated with 3 mM acetate, 1 mM propionate, and 1 mM butyrate. Intracellular levels of p-ERK, p-JNK, and p-p38 were analyzed by western blotting. Relative phosphorylation levels were calculated by p-p38, and p-ERK/ERK and pJNK/JNK, and which were normalized to control (n = 4); (F–H) Quantity of p-ERK, p-JNK, and p38MAPK at 5 min after treatment of SCFAs: (F) Acetate, (G) Propionate, and (H) Butyrate; (I–K) MAPK inhibitors block SCFA-induced increase of GLP-1 secretion. IECs were treated with 3 mM acetate, 1 mM propionate, and 1 mM butyrate, with or without the ERK-specific inhibitor (UO126, 10 μM), JNK inhibitor (SP600125, 20 μM), and p38 inhibitor (SB203580, 10 μM), respectively. GLP-1 concentration was detected by high sensitivity GLP-1 Active ELISA-Chemiluminescent kit (n = 6): (I) Acetate, (G) Propionate, (H) Butyrate. Data were presented as mean ± SE. ∗p < 0.05, ∗∗p < 0.01, and ∗∗∗p < 0.001.