Figure 1.

Mechanism of glucose‐dependent insulinotropic polypeptide (GIP) secretion induced by glucose in K cells. Under the normoglycemic state, glucose loaded in the intestinal lumen is transported through sodium–dependent glucose cotransporter 1 in the apical side of K cells, which induces membrane depolarization and GIP secretion. Adenosine triphosphate‐sensitive potassium (K_ATP) channels are expressed in K cells. However, they remain closed in the basal condition. Under the high glycemic state, K_ATP channels maintain open. When glucose is transported, the elevation of cellular ATP levels caused by cellular metabolism leads to close K_ATP channels, which also triggers membrane depolarization, and involves in GIP secretion in addition to the sodium–dependent glucose cotransporter 1 (SGLT1)‐dependent manner. FGF21, fibroblast growth factor 21; GK, glucokinase; SUR1, sulfonylurea receptor 1; VDCC, voltage‐dependent Ca channel. [Colour figure can be viewed at wileyonlinelibrary.com]