TRPV4 couples with NCX1 to mediate glucose‐dependent glucagon‐like peptide‐1 release and improve glucose homeostasis

Abstract Although glucose, as a secretagogue of intestinal hormone, can stimulate glucagon‐like peptide 1 (GLP‐1) release, it has not been fully elucidated how glucose triggers GLP‐1 release from enteroendocrine cells (EECs). Here, we investigated the regulatory mechanisms of glucose‐induced Ca 2+ ‐dependent GLP‐1 release from EECs. STC‐1 cells that possess many features of native intestinal EECs were used. The expression of TRPV4 channels and Na + /Ca 2+ exchanger 1 (NCX1) in STC‐1 was analysed by immunocytochemistry. Calcium and sodium imaging, and patch clamp were applied, and GLP‐1 was detected using quantitative PCR, western blot and enzyme‐linked immunosorbent assays. Glucose markedly induced Na + and Ca 2+ signalling in STC‐1 cells. The glucose‐induced Ca 2+ signalling was significantly attenuated by selective blockers of the voltage‐gated Ca 2+ channels (VGCC), ryanodine receptors and Ins P 3 receptors. Most importantly, glucose‐induced Ca 2+ signalling was significantly attenuated by the selective blockers of TRPV4 and NCX1. Moreover, the physical and functional couplings of TRPV4 and NCX1 were demonstrated in STC‐1 cells, and they promoted glucose‐mediated Ca 2+ signalling to upregulate expression and release of GLP‐1 via Ca 2+ ‐sensitive PKCα. Finally, the selective TRPV4 activator improved glucose tolerance in an oral glucose tolerance test in mice, but the selective blockers of TRPV4 and NCX1 attenuated glucose‐induced intestinal GLP‐1 release. We demonstrate a coupling of TRPV4 and NCX1 in EECs to regulate glucose‐stimulated intestinal GLP‐1 release via a novel TRPV4/NCX1/Ca 2+ /PKCα axis. Targeting this axis may provide new therapeutic potentials for glycometabolic diseases. image Key points Glucagon‐like peptide 1 (GLP‐1) secreted primarily from intestinal L cells in response to meals plays a critical role in maintaining glucose homeostasis. Physical and functional couplings of TRPV4 and NCX1 are pivotal in glucose‐stimulated GLP‐1 release via a novel TRPV4/NCX1/Ca 2+ /PKCα axis. Since this axis is involved in glucose homeostasis, our findings may provide new potential drug targets for prevention/treatment of glycometabolic diseases.