Role of clock genes in gastrointestinal motility.

Biological rhythms coordinate the timing of our internal bodily functions. Colonic motility follows a rhythm as well: most people will have a bowel movement in the morning and rarely during the night. Recent work provides a potential mechanism for this observation: the mouse colon possesses a functional circadian clock as well as a subset of rhythmically expressed genes that may directly impact on colonic motility. Furthermore, measures of colonic motility such as the colonic tissue contractile response to acetylcholine, stool output, and intracolonic pressure changes vary as a function of the time of day, but these variations are attenuated in mice with disrupted clock function. These laboratory findings are supported by clinical observations. Gastrointestinal symptoms such as diarrhea or constipation are prevalent among shift workers and time-zone travelers, both of which are conditions associated with disruptions in biological rhythms. This review will discuss new insights into the role of clock genes in colonic motility and their potential clinical relevance.