Circadian clocks in the digestive system

Many molecular, physiological and behavioural processes display distinct 24-hour rhythms that are directed by the circadian system. The master clock, located in the suprachiasmatic nucleus region of the hypothalamus, is synchronized or entrained by the light-dark cycle and, in turn, synchronizes clocks present in peripheral tissues and organs. Other environmental cues, most importantly feeding time, also synchronize peripheral clocks. In this way, the circadian system can prepare the body for predictable environmental changes such as the availability of nutrients during the normal feeding period. This Review summarizes existing knowledge about the diurnal regulation of gastrointestinal processes by circadian clocks present in the digestive tract and its accessory organs. The circadian control of gastrointestinal digestion, motility, hormones and barrier function as well as of the gut microbiota are discussed. An overview is given of the interplay between different circadian clocks in the digestive system that regulate glucose homeostasis and lipid and bile acid metabolism. Additionally, the bidirectional interaction between the master clock and peripheral clocks in the digestive system, encompassing different entraining factors, is described. Finally, the possible behavioural adjustments or pharmacological strategies for the prevention and treatment of the adverse effects of chronodisruption are outlined. Many molecular, physiological and behavioural processes display distinct daily rhythms that are directed by the circadian system. This Review summarizes knowledge about the diurnal regulation of gastrointestinal processes by circadian clocks present in the digestive tract and its accessory organs, including circadian control of digestion, motility, hormones, barrier function and the gut microbiota.

Automated summary

The circadian system controls various physiological processes in the body, including digestion, motility, hormone secretion, barrier function, and gut microbiota, through the coordination between the master clock and peripheral clocks. External cues, such as feeding time, also play a role in synchronizing peripheral clocks. This system helps prepare the body for predictable environmental changes and influences glucose and lipid metabolism in the digestive system.