Identification of a regulatory pathway of L-phenylalanine-induced GLP-1 secretion in the enteroendocrine L cells.

Glucagon like peptide-1 (GLP-1) is one of incretin hormone and is secreted when enteroendocrine L cells sense saccharides, amino acids, and fatty acids. Some amino acids have been shown to promote GLP-1 secretion from small intestinal enteroendocrine L cells. However, the molecular mechanisms that L-phenylalanine, a potent trigger of GLP-1 secretion, causes GLP-1 secretion from enteroendocrine L cells has not been elucidated. In this study, we used live-cell imaging to clarify the pathway by which L-phenylalanine activates enteroendocrine L cells. The results showed that L-phenylalanine was sensed by G-coupled receptor GPR142 and caused an increase in intracellular Ca concentration. In addition, L-phenylalanine was taken up directly into the cell via Na-dependent amino acid transporter, causing membrane depolarization and enhancing GLP-1 secretion. In summary, enteroendocrine L cells may regulate blood glucose levels in the body by detecting L-phenylalanine in the lumen and secreting GLP-1 via GPR142 and Na-dependent amino acid transporters.