Effects of live and heat-treated Limosilactobacillus fermentum PS150 on circadian rhythms and GABAergic signaling in a caffeine-induced insomnia mouse model

Abstract

Insomnia is the most prevalent sleep disorder worldwide and results from multiple factors. While Limosilactobacillus fermentum PS150 (PS150) improves sleep in animal models, its effects on insomnia remain unclear. In this study, a caffeine-induced insomnia mouse model was established to evaluate the effects of live PS150 and its heat-treated form (HT-PS150). Mice were supplemented with PS150 or HT-PS150 for 21 days, and caffeine was administered during the final week to induce insomnia-like symptoms. Sleep parameters, including sleep latency, duration, and recovery time, were subsequently evaluated using a pentobarbital-induced sleep test. Compared with the vehicle control group, caffeine significantly increased sleep latency, which was reversed by HT-PS150 but showed only a trend toward improvement with PS150. The sleep duration remained unchanged; however, both forms significantly shortened the recovery time. These results indicate the potential of PS150 to alleviate caffeine-induced sleep disturbance. In contrast, the caffeine-treated group exhibited increased adenosine A1 receptor expression, activation of protein kinase A–cAMP response element-binding protein signaling, upregulation of Per2, Cry1, and Cry2, and disrupted GABAergic balance in the prefrontal cortex, a key region involved in sleep homeostasis. PS150 and HT-PS150 reversed these alterations, thereby normalizing circadian and GABAergic signaling. Moreover, both treatments modified the gut microbiota composition, suggesting potential involvement of the microbiota–gut–brain axis. PS150 and HT-PS150 may ameliorate caffeine-induced sleep disturbances through mechanisms potentially associated with circadian modulation, regulation of GABAergic signaling, and alterations in gut microbiota composition. These findings highlight their potential as functional food ingredients or dietary supplements for supporting sleep health.