Gut Dysbiosis in Insomnia and Diurnal Cycle

Abstract

Prolonged insomnia may shorten the life expectancy in humans, as this sleeping disorder has already been associated with miscellaneous detrimental health effects on humans such as risk of elevated blood pressure, type 2 diabetes, hyperlipidemia, obesity, coronary heart disease (CHD), and stroke. Numerous studies manifested that onset of sleeplessness and insomnia is linked to disruption of circadian and microbiome rhythms, immune response, and nutrient metabolism, however, precise mechanism is yet to be elucidated. Moreover, it is now understood that gut dysbiosis and circadian rhythm disruption can affect the quality of sleep, and are associated with other metabolic disorders. Considerable evidences have shown that gut microbiome regulates sleep and psychological states of its host through microbiome–gut–brain (MGB) axis. Research findings have indicated that diurnal variations, emotional state, and physiological stress can disrupt the composition and function of gut microbiota which in turn destabilizes host’s circadian gene expression and functions. Consequently, disruptions of gut microbiome-mediated functions such as diminished bile acids conjugation or enhanced generation of H₂S, and the reduced butyrate production, in turn affect substrate oxidation and metabolic homeostasis of the host. Furthermore, gut dysbiosis and altered circadian gene expression may cause onset of insomnia, circadian misalignment, and metabolic disorders. Nevertheless, insomnia condition can be reversed by: (1) achieving daily rhythmicity of gut bacteria by prebiotics enriched dietary interventions; (2) adopting healthy lifestyle especially meal timing, selective eating patterns and sleep timing; and (3) oral administration of probiotics in order to restore the gut microbial balance. Thus, manipulation of gut microbiome structure through synbiotic diet and chrononutrition-based approaches may therefore hold promise to consolidate host circadian rhythms.