Improvement of sleep duration and quality through GABA_A receptor by whey protein hydrolysate containing DIQK as the main active compound

This study characterized the sleep activity, sleep mechanism, and active peptides of whey protein hydrolysates selected through behavioral analysis of fruit flies (Drosophila melanogaster). Sleep-inducing whey protein (WP) hydrolysate was selected through fruit fly behavior analysis, and sleep activity was measured using a pentobarbital model and electroencephalographic analysis. The mechanism of action was confirmed using a γ-aminobutyric acid (GABA) receptor antagonist, and the active peptide was identified using liquid chromatography-mass spectrometry. Whey protein hydrolysate, prepared using Alcalase and Prozyme (WP-AP), increased sleep time in a dose-dependent manner. The WP-AP significantly increased not only sleep time but also slow-wave sleep and showed an insomnia-alleviating effect in a caffeine-induced insomnia mouse model. In addition, the gene and protein expression levels of GABA subtype A receptors increased in the brains of mice orally administered with WP-AP. Through peptide analysis, the mixture of DIQK, VPPF peptide, and GABA contained in WP-AP was estimated to exhibit sleep activity, and due to its high content, DIQK was speculated to be the main sleep-inducing ingredient. These results indicate that WP-AP has the potential to be used as a new ingredient to improve sleep quality.