Rhythm of digestion: keeping time in the gastrointestinal tract.
ABSTRACT 1. The best characterized mammalian circadian rhythms follow a light-entrained central master pacemaker in the suprachiasmatic nucleus and are associated with fluctuations in the activities of clock genes, including Clock, Bmal1, Per and Cry, the products of which bind to sequences in the promoters of effector genes. This is the central clock. 2. In the present review, we discuss evidence for an independent, but interacting, gut-associated circadian clock, the peripheral clock, which is entrained by food. 3. Disruption of circadian rhythms is associated with a wide range of pathologies, most prominently metabolism linked, but the effects of disruption of circadian rhythms on the digestive system are less well studied, although also likely to lead to functional consequences. There are clues suggestive of links between gastrointestinal disorders related to inflammation, cancer and motility and disruption of peripheral rhythms. Research aimed at understanding these links is still in its infancy. 4. We also discuss practical aspects of the presence of circadian rhythms in gastrointestinal tissues for researchers related to experimental design, data interpretation and the choice of animal models. 5. There is currently sufficient evidence to suggest that circadian rhythms are important to gut function, metabolism and mucosal defence and that further investigation will uncover connections between disordered rhythms and gastrointestinal malfunction.
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ABSTRACT: Developmental biology is among the many subdisciplines of the life sciences being transformed by our increasing awareness of the role of coevolved microbial symbionts in health and disease. Most symbioses are horizontally acquired, i.e., they begin anew each generation. In such associations, the embryonic period prepares the animal to engage with the coevolved partner(s) with fidelity following birth or hatching. Once interactions are underway, the microbial partners drive maturation of tissues that are either directly associated with or distant from the symbiont populations. Animal alliances often involve complex microbial communities, such as those in the vertebrate gastrointestinal tract. A series of simpler-model systems is providing insight into the basic rules and principles that govern the establishment and maintenance of stable animal-microbe partnerships. This review focuses on what biologists have learned about the developmental trajectory of horizontally acquired symbioses through the study of the binary squid-vibrio model. Expected final online publication date for the Annual Review of Microbiology Volume 68 is September 08, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.Annual Review of Microbiology 06/2014; DOI:10.1146/annurev-micro-091313-103654 · 13.02 Impact Factor
Article: Chronobiology and Nutrition.[Show abstract] [Hide abstract]
ABSTRACT: Numerous long-term studies have investigated the circadian clock system in mammals, which organizes physiological functions, including metabolism, digestion, and absorption of food, and energy expenditure. Food or nutrition can be a synchronizer for the circadian clock systems, as potent as the external light-dark signal can be. Recent studies have investigated different kinds of food, frequency of consumption, and time of consumption for optimizing body clock and ensuring healthy habits. In this review, we discuss recent studies investigating chronobiology and nutrition, and then summarize available information as "Chrono-nutrition" for the development of a new standardized research strategy.Neuroscience 09/2013; DOI:10.1016/j.neuroscience.2013.08.049 · 3.33 Impact Factor
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ABSTRACT: Knowing animals' gut retention time (GRT) for important food items is critical when using non-invasive studies based on faecal remains, e.g. when analysing nutritive quality of food, or relating diet or behaviour to movements. We analysed GRT in six captive brown bears Ursus arctos, after feeding on either berries (a mixture of bilberry Vaccinium myrtillus and lingonberry V. vitis-idaea) or animal carcasses (either reindeer Rangifer tarandus, European rabbit Oryctolagus cuniculus, domestic pig Sus scrofa domestica, cattle Bos taurus or horse Equus ferus caballus). Median GRT(50%) (i.e. when 50% of all faeces containing experimental food had been defecated) was 5 hours and 47 minutes (1st and 3rd quartiles = 4 hours and 36 minutes and 7 hours and 3 minutes; N = 20) after feeding on berries and 14 hours and 30 minutes (1st and 3rd quartiles = 10 hours and 9 minutes and 16 hours and 57 minutes; N = 20) after feeding on carcasses. Median GRT(50%) in (i.e. first defecation comprised of experimental food) was 3 hours and 5 minutes (1st and 3rd quartiles = 1 hour and 51 minutes and 4 hours and 12 minutes; N = 21) for berries and 8 hours and 2 minutes (1st and 3rd quartiles = 6 hours and 14 minutes and 10 hours and 44 minutes; N = 20) for carcasses. Median GRT(max) (i.e. last defecation comprised of experimental food) was 15 hours and 27 minutes (1st and 3rd quartiles = 11 hours and 36 minutes and 17 hours and 16 minutes; N = 21) for berries and 16 hours and 16 minutes (1st and 3rd quartiles = 12 hours and 11 minutes and 17 hours and 27 minutes; N = 20) for carcasses. A carcass diet had 6 hours and 26 minutes +/- 1 hour and 56 minutes (SE) longer GRT(50%) than a berry diet (N = 39), despite low variation in food intake. Activity level, feeding time (midday/midnight), sex, age (subadult/adult), ingested amounts of food, prior food remains processed by the gut (i.e. cumulative faeces weight) and defecation rate did not influence the GRT(50%). Our reported GRT estimates are reliable values to be used within research and management to relate diet based on faecal remains to habitat use for common and important food items used by Scandinavian brown bears.Wildlife Biology 03/2013; 19(3):317-324. DOI:10.2981/12-121 · 1.07 Impact Factor