Asynchrony in circadian rhythms of gastric function in the rat. A model for gastric mucosal injury

Circadian rhythms: a regulator of gastrointestinal health and dysfunction

Circadian rhythms regulate much of gastrointestinal physiology including cell proliferation, motility, digestion, absorption, and electrolyte balance. Disruption of circadian rhythms can have adverse consequences including the promotion of and/or exacerbation of a wide variety of gastrointestinal disorders and diseases. Areas covered: In this review, we evaluate some of the many gastrointestinal functions that are regulated by circadian rhythms and how dysregulation of these functions may contribute to disease. This review also discusses some common gastrointestinal disorders that are known to be influenced by circadian rhythms as well as speculation about the mechanisms by which circadian rhythm disruption promotes dysfunction and disease pathogenesis. We discuss how knowledge of circadian rhythms and the advent of chrono-nutrition, chrono-pharmacology, and chrono-therapeutics might influence clinical practice. Expert opinion: As our knowledge of circadian biology increases, it may be possible to incorporate strategies that take advantage of circadian rhythms and chronotherapy to prevent and/or treat disease.

The role of the circadian clock system in nutrition and metabolism

Mammals have an endogenous timing system in the suprachiasmatic nuclei (SCN) of the hypothalamic region of the brain. This internal clock system is composed of an intracellular feedback loop that drives the expression of molecular components and their constitutive protein products to oscillate over a period of about 24 h (hence the term 'circadian'). These circadian oscillations bring about rhythmic changes in downstream molecular pathways and physiological processes such as those involved in nutrition and metabolism. It is now emerging that the molecular components of the clock system are also found within the cells of peripheral tissues, including the gastrointestinal tract, liver and pancreas. The present review examines their role in regulating nutritional and metabolic processes. In turn, metabolic status and feeding cycles are able to feed back onto the circadian clock in the SCN and in peripheral tissues. This feedback mechanism maintains the integrity and temporal coordination between various components of the circadian clock system. Thus, alterations in environmental cues could disrupt normal clock function, which may have profound effects on the health and well-being of an individual.

Shift work increases the frequency of duodenal ulcer in H pylori infected workers

AIM

To evaluate whether shift work is associated with an increased rate of peptic ulcer in H pylori infected workers.

METHODS

During a two year period, consecutive dyspeptic workers underwent non-invasive evaluation of H pylori status by means of urea 13C breath test or stool testing. Those testing positive were included in the study and divided into two main categories: day-time workers and shift workers. An upper gastrointestinal endoscopy was performed in all workers, and biopsy specimens were taken from the stomach to confirm the presence of H pylori infection (culture and histology).

RESULTS

A total of 247 day-time workers and 101 shift workers were included. The prevalence of duodenal ulcer was significantly higher in shift workers than in day-time workers (29 of 101 v 23 of 247; OR = 3.92, 95% CI 2.13 to 7.21), and persisted after multivariate analysis, taking into account possible confounding factors (OR = 3.96, 95% CI 2.10 to 7.47).

CONCLUSION

Shift work increases the ulcerogenic potential of H pylori infection and should be considered a risk factor for duodenal ulcer in infected shift workers. Treatment of infection in this high risk group may improve the health of workers and may reduce the economic impact of peptic ulcer.

Relationship of work schedules to gastrointestinal diagnoses, symptoms, and medication use in auto factory workers

BACKGROUND

Gastrointestinal (GI) complaints are common in shift workers. This study examines the relationship between work schedules and GI symptoms, medications, and diagnoses.

METHODS

In a cross-sectional survey of 343 US auto factory workers, four work schedule variables were examined: assigned shift, number of hours worked, number of night hours, and schedule variability. Multiple regression tested the relationship between GI outcomes and work schedule variables while controlling for covariates.

RESULTS

The evening shift was associated with more GI symptoms and GI diagnoses. Unexpectedly, more consistent work times were associated with having a GI diagnosis. As schedule variability increased the probability of GI medication use increased in low noise exposure.

CONCLUSION

Findings suggest that evening shift and widely varying work start and end times may increase risks for GI disturbances.

Rhythmic patterns in incidence of peptic ulcer perforation over 5.5 decades in Norway

The incidence of ulcer perforation in 1480 patients treated in the Bergen area of Norway between 1935 and 1990 was analyzed for daily (circadian), weekly (circaseptan), and yearly (circannual) time effects. A circadian rhythm was found overall that was reproducible and fairly stable across seasons, decades, and days of the week. After subgrouping, a circadian rhythm was found in younger patients, males, and duodenal perforations, while a 12 h (circasemidian) rhythm characterized ulcer perforation for women and for gastric ulcers. Duodenal perforations showed highest incidence in the afternoon, while gastric perforations showed a major peak around noon and a secondary peak near midnight. For duodenal ulcer perforation, the circannual pattern was characterized by a 6-month rhythm, with significantly higher incidence in May-June-July and in November-December in most subgroups. A circaseptan rhythm was not found, but there was a significantly higher incidence on Thursday-Friday as compared to Sunday-Monday. The pathophysiological mechanisms underlying the perforation of an ulcer thus seemed to show pronounced circadian and 6-month rhythmic variations, much less so circaseptan or circannual rhythms. While it is likely that exogenous environmental and/or societal factors play a significant role, variations in ulcer perforation may be related to endogenous biological rhythms in pathophysiological factors since the circadian pattern of duodenal perforation follows that for gastric acidity. Knowledge of the temporal patterns in peptic ulcer perforation and associated pathophysiologic factors should prove useful in optimizing the chronotherapeutic management of ulcer disease.