ABSTRACT
Dietary peptides potently stimulate glucagon-like peptide-1 (GLP-1) secretion, however, the underlying molecular mechanisms, such as structure-activity relationships and sensing mechanisms are only partly elucidated. In this study, we used a dipeptide library to identify dipeptides that potently stimulate GLP-1 release and to clarify the underlying structure-activity relationship. Murine enteroendocrine GLUTag cells were exposed to 339 dipeptides for 60 min, and the concentration of GLP-1 released into the supernatant was measured. Subsequently, selected dipeptides were examined for their reproducibility and dose responsiveness. In addition, we investigated the role of constituent amino acids in the secretion of GLP-1, and whether tripeptides containing the active dipeptide structures maintained their activity. In a concentration range of 1-5 mg/mL, twelve dipeptides had reproducible and concentration-dependent GLP-1-releasing activity. Among them, nine dipeptides (FY, KF, NI, PM, QL, QY, WF, WN, WY) were novel, with WY exhibiting the most potent activity. The reverse sequences and most free amino acids did not induce GLP-1 secretion, indicating that GLP-1-producing cells recognize the structure of each peptide to induce GLP-1 secretion. However, no apparent similarities were found between the active peptides. A comparison between the six tripeptides composed of F, W, and Y revealed the further potent tripeptides FWY and WYF, than WY. In the present study, a comprehensive analysis revealed nine novel dipeptides with high potential to stimulate GLP-1 secretion. Furthermore, the results indicate that 'WY' is a specific dipeptide sequence that potently stimulates GLP-1 secretion.