Microbiome and Circadian Rhythms: Implications for Sleep, Aging, and Therapeutic Strategies

The gut microbiome undergoes diurnal fluctuations, bridging the gap between the host and the external environment and influencing the circadian transcriptional rhyth m in the hepatic and gastrointestinal systems, ultimately affecting overall metabolism. Circadian rhythms, the 24-h rhythmic cycles of physiological processes, regulated by the suprachiasmatic nucleus (SCN), an endogenous clock in the anterior hypothalamus. The gut microbiome also influences sleep and mental states through the microbiome–gut–brain axis. Recent studies in mice have shown that misalignment of the circadian rhythm with the sleep–wake cycle alters the gut microbiota composition. Dysbiosis leads to decreased levels of beneficial gut microbial metabolites, such as short-chain fatty acids (SCFAs), that contribute to age-related neurodegenerative disorders. This chapter explores the molecular crosstalk between the gut microbiota and circadian rhythm, emphasizing the impact of sleep–wake cycle disruptions and aging-related neurodegenerative disorders. Additionally, it provides insights into therapeutic techniques and solutions involving the modulation of gut microbiota and the light–dark cycle to mitigate these disorders. Understanding the intricate relationship between the microbiome and circadian rhythms offers potential interventions for sleep, aging, and associated neurodegenerative conditions.