Identification of novel β-lactoglobulin-derived peptides, wheylin-1 and -2, having anxiolytic-like activity in mice

Abstract

Scope: We found that thermolysin digest of β-lactoglobulin, a major protein of bovine milk whey, exhibited anxiolytic-like activity in a behavioral experiment in mice, and then identified active components from the digest.

Methods and results: In the elevated plus-maze test, thermolysin digest of β-lactoglobulin had anxiolytic-like activity after intraperitoneal administration in mice. We identified several low-molecular-weight peptides in a fraction separated by reverse-phase HPLC having the most potent anxiolytic-like activities. Among them, Met-His and Met-Lys-Gly, corresponding to β-lactoglobulin (145-146) and (7-9), had anxiolytic-like activity at a dose of 0.3-1 and 3 mg/kg, respectively, after intraperitoneal administration. We named Met-His and Met-Lys-Gly wheylin-1 and -2, respectively. Next, we focused on wheylin-1, a more potent peptide with anxiolytic-like activity than wheylin-2. Wheylin-1 (1 mg/kg) had anxiolytic-like activity after oral administration. In the open-field test, wheylin-1 was also active. The anxiolytic-like activity of wheylin-1 was blocked by bicuculline, an antagonist of γ-amino butyric acid type A (GABA(A)) receptor, suggesting that wheylin-1 exhibited anxiolytic-like activity via the GABA(A) system.

Conclusion: Novel β-lactoglobulin-derived peptides, wheylin-1 and -2, may exhibit anxiolytic-like activities.

Keywords: Anxiolytic-like activity; Dipeptide; GABAA receptor; Thermolysin; β-lactoglobulin.