Dietary natural cocoa ameliorates disrupted circadian rhythms in locomotor activity and sleep-wake cycles in mice with chronic sleep disorders caused by psychophysiological stress

Katsutaka Oishi 1, Hiroki Okauchi 2, Saori Yamamoto 3, Sayaka Higo-Yamamoto 3

Abstract

Objectives: Cocoa contains many chemical compounds that affect the physiological functions of experimental animals and humans. The present study used a mouse model characterized by disrupted circadian rhythms of locomotor activity and sleep-wake cycles to determine whether natural cocoa improves chronic sleep disorders (CSDs) induced by psychophysiological stress.

Methods: Mice were fed a high-fat, high-sucrose diet supplemented with 2.0% natural cocoa and stressed for 30 d to induce CSDs.

Results: Dietary cocoa restored the amplitude reduction of day-night activity rhythms by improving reduced nocturnal wheel-running activities during CSDs. Electroencephalography revealed that dietary cocoa significantly ameliorated CSD-induced increases in wakefulness during the first half of the inactive phase and in nonrapid eye movement sleep during the first half of the active phase. The attenuation of circadian rapid eye movement sleep rhythms and increased electroencephalography slow-wave activity (a marker of nonrapid eye movement sleep intensity) induced by CSDs improved in mice supplemented with cocoa. Dietary cocoa notably did not affect wheel-running activity rhythms or sleep-wake cycles under normal conditions. Dietary cocoa significantly increased the hypothalamic mRNA expression of Hspa1 a that encodes HSP70 and is associated with sleep regulation. Furthermore, Hspa1 a expression was not induced by CSDs in mice supplemented with cocoa.

Conclusions: These findings suggest that dietary cocoa exerts beneficial effects on insomnia and circadian sleep disorders induced by psychophysiological stress.