Bitter Peptides YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV, Released during Gastric Digestion of Casein, Stimulate Mechanisms of Gastric Acid Secretion via Bitter Taste Receptors TAS2R16 and TAS2R38

Abstract

Eating satiating, protein-rich foods is one of the key aspects of modern diet, although a bitter off-taste often limits the application of some proteins and protein hydrolysates, especially in processed foods. Previous studies of our group demonstrated that bitter-tasting food constituents, such as caffeine, stimulate mechanisms of gastric acid secretion as a signal of gastric satiation and a key process of gastric protein digestion via activation of bitter taste receptors (TAS2Rs). Here, we tried to elucidate whether dietary non-bitter-tasting casein is intra-gastrically degraded into bitter peptides that stimulate mechanisms of gastric acid secretion in physiologically achievable concentrations. An in vitro model of gastric digestion was verified by casein-fed pigs, and the peptides resulting from gastric digestion were identified by liquid chromatography–time-of-flight-mass spectrometry. The bitterness of five selected casein-derived peptides was validated by sensory analyses and by an in vitro screening approach based on human gastric parietal cells (HGT-1). For three of these peptides (YFYPEL, VAPFPEVF, and YQEPVLGPVRGPFPIIV), an upregulation of gene expression of TAS2R16 and TAS2R38 was observed. The functional involvement of these TAS2Rs was verified by siRNA knock-down (kd) experiments in HGT-1 cells. This resulted in a reduction of the mean proton secretion promoted by the peptides by up to 86.3 ± 9.9% for TAS2R16kd (p < 0.0001) cells and by up to 62.8 ± 7.0% for TAS2R38kd (p < 0.0001) cells compared with mock-transfected cells.

Conserved Sites and Recognition Mechanisms of T1R1 and T2R14 Receptors Revealed by Ensemble Docking and Molecular Descriptors and Fingerprints Combined with Machine Learning

“… a Note: index 0–9 is derived from Liang’s work, index 10–12 is derived from Richter’s work, index 13–21 is derived from Liu’s work, index 22–29 is derived from Shan’s work, index 30–38 is derived from Zhang’s work, index 39–47 is derived from Liang’s work, and index 48–53 is derived from Cui’s work …”

Purification, Identification, and Mechanistic Investigation of Novel Selenium-Enriched Antioxidant Peptides from Moringa oleifera Seeds

“…However, our current research is mainly based on in vitro cell antioxidant experiments to study the antioxidant activity of the Se-enriched peptides. Considering the possible changes in the structure of these Se-enriched peptides during digestion and the metabolic transformation after absorption, the relevant effective concentrations obtained in the current experimental results need to be further verified in animal or human intervention studies.miaojy8181@scau.edu.cn…”

Identification of a Bitter Peptide Contributing to the Off-Flavor Attributes of Pea Protein Isolates

“…Several indole derivatives have been found in bitter cruciferous vegetables, such as broccoli, cabbage, and Brussels sprouts . Although not related to sensory bitter taste perception, Ritcher et al recently reported bitter peptides upregulated the gene expression of TAS2R16 and TAS2R38, which altered gastric acid secretion from HGT-1 cells.…”

“…Identified Amino Acid Sequence of a Bitter PA1b Variant Peptide in PPI in bitter cruciferous vegetables, such as broccoli, cabbage, and Brussels sprouts. 32 Although not related to sensory bitter taste perception, Ritcher et al 33 recently reported bitter peptides upregulated the gene expression of TAS2R16 and TAS2R38, which altered gastric acid secretion from HGT-1 cells. Furthermore, the PA1b peptide is known to possess an inhibitor cysteine knot (ICK) or knottin motif, where the two disulfide bonds form a loop through which the third disulfide bond passes.…”