Soy‐ghretropin, a novel ghrelin‐releasing peptide derived from soy protein

Abstract

Edited by Michael SussmanWe investigated exogenous secretagogues of ghrelin, which is an orexigenic hormone isolated from the stomach. We found that the tryptic digest of soy b-conglycinin stimulated ghrelin secretion by the ghrelin-producing cell line, MGN3-1. We then identified a 22-amino acid peptide corresponding to the bconglycinin a-subunit ] from an active fraction separated by HPLC. The N-terminal undecapeptide of bCGa , NKNPFLFGSNR, exhibited ghrelin-releasing activity at a lower dose than that of bCGa . We named NKNPFLFGSNR 'soy-ghretropin', which corresponds to bCGa (192)(193)(194)(195)(196)(197)(198)(199)(200)(201)(202). Neither [des-N 1 K 2 ]-soy-ghretropin nor [des-R 11 ]-soy-ghretropin stimulated ghrelin secretion; hence, both the N-and Cterminal structures of soy-ghretropin were indispensable. Orally administered soy-ghretropin increased plasma ghrelin levels and food intake in vivo. Soyghretropin is the first exogenous ghrelin-releasing peptide derived from food protein.

Lacto‐ghrestatin, a novel bovine milk‐derived peptide, suppresses ghrelin secretion

“…In vitro experiment on ghrelin secretion in MGN3-1 cells Acylated ghrelin concentrations in culture media of MGN3-1 cells were measured as described previously [20]. Briefly, MGN3-1 cells were washed with Dulbecco's phosphate-buffered saline (DPBS) and incubated with chemicals dissolved in DMEM containing 50 lM sodium octanoate at 37°C for 4 h. The collected culture media were centrifuged at 800 g for 5 min at 4°C.…”

“…Cyclic AMP and Ca 2+ levels in MGN3-1 cells were measured as described previously [20]. For cAMP measurement, cells were incubated with chemicals dissolved in Krebs-Ringer-HEPES buffer (110 mM NaCl, 5 mM KCl, 1.8 mM CaCl 2 , 1 mM MgCl 2 , 55 mM sucrose, 25 mM glucose, 10 mM HEPES, pH 7.4) containing 500 lM 3-isobutyl-1-methylxanthine at 37°C for 30 min.…”

“…Measurement of plasma ghrelin levels was performed with slight modification to the previously described method [20]. Briefly, 11-weeks-old male ddY mice (Japan SLC, Shizuoka, Japan) were deprived of food pellets for 18 h in the case of fasting conditions.…”

“…Currently, a number of low molecular weight bioactive peptides have been found from the protease hydrolysate of several food proteins including milk protein [10][11][12][13][14][15][16][17][18][19]. Recently, our group has reported the first exogenous ghrelin-releasing peptide derived from food protein [20]. In this study, we focused on exogenous peptides that exhibited ghrelin secretion-lowering activity, which may contribute to suppressing food intake and/ or preventing obesity.…”

Comprehensive analysis of a dipeptide library to identify ghrelin release‐modulating peptides

“…Several amino acids, glucose, and fatty acids were reported to affect ghrelin secretion . Recently, our group identified ghrelin release‐modulating peptides from enzymatic digests of food proteins . However, the structural characteristics of peptides which can modulate ghrelin secretion are unknown.…”