Beneficial effect of GABA-rich fermented milk on insomnia involving regulation of gut microbiota

Insomnia is a common health problem in modern societies. GABA, an inhibitory neurotransmitter, can promote relaxation and reduce anxiety. In this study, milk was fermented with Lactobacillus brevis DL1-11, a strain with high GABA-producing capacity. The potential beneficial effects of this fermented milk on anxiety and sleep quality were evaluated in animal experiments. Sixty mice were divided into control, non-GABA fermented milk (NGFM), low-dose GABA fermented milk (LGFM, 8.83 mg/kg.bw), medium-dose GABA fermented milk (MGFM, 16.67 mg/kg.bw), high-dose GABA fermented milk (HGFM, 33.33 mg/kg.bw) and diazepam groups. The results of open field test and elevated plus-maze test indicated decreases in anxiety behavior after oral HGFM administration. Moreover, mice in the HGFM group exhibited a significantly prolonged sleep time after an intraperitoneal injection of sodium pentobarbital and a shortened sleep latency after an intraperitoneal injection of sodium barbital. These results indicate a beneficial effect of HGFM on sleep. Additionally, significant increases in the relative abundances of Ruminococcus, Adlercreutzia and Allobaculum and the levels of some short-chain fatty acids (SCFAs), such as butyric acid, were observed in the HGFM group. The results suggest that GABA-fermented milk may improve sleep and the protective pathways may involve in regulation of gut microbiota and increase of SCFAs level.