Screening and identification of novel peptides stimulating GLP‐1 secretion from plant proteins after simulated gastrointestinal digestion

Abstract Glucagon‐like peptide‐1 (GLP‐1), secreted by enteroendocrine L cells, plays a crucial role in glucose homeostasis and appetite regulation. The identification of food‐derived bioactive compounds capable of stimulating endogenous GLP‐1 secretion has attracted increasing attention in the development of functional foods. This study evaluated the effects of simulated gastrointestinal digests from four plant proteins (quinoa, oat, barley, and mung bean) on GLP‐1 secretion and identified the responsible bioactive peptides. All four plant protein digests stimulated GLP‐1 secretion in STC‐1 cells in a dose‐dependent manner, with oat protein digest (OPD) exhibiting the strongest activity, followed by barley protein digest (BPD). At 5 mg/mL, OPD and BPD increased GLP‐1 secretion by approximately 11.5‐fold and 6.7‐fold, respectively, compared with the control. Acute oral administration of OPD and BPD (1000 mg/kg body weight) also significantly increased plasma GLP‐1 concentrations 120 min after administration, reaching 3.25‐fold and 1.71‐fold of the control, respectively. LC–MS/MS analysis identified ten candidate peptides, among which six novel peptides (LVLPQ, SDAQNK, QPQQLSQ, QQVFQPQ, VQVQIPF, and VVTGVGGQ) significantly stimulated GLP‐1 secretion in vitro. These findings expand the current knowledge of food‐derived GLP‐1 secretagogues, identify oat and barley proteins as promising sources of GLP‐1 secretion‐stimulating peptides, and provide novel candidates for the development of functional food ingredients targeting endogenous GLP‐1 secretion.