Biology Reference
In-Depth Information
CHAPTER FIVE
Circadian Clocks, Food Intake,
and Metabolism
Etienne Challet
Neurobiology of Rhythms, Institute of Cellular and Integrative Neurosciences, CNRS UPR3212 Associated
with University of Strasbourg, Strasbourg, France
Contents
1.
Introduction
106
2. Physiology
108
2.1 Daily rhythm of food intake
108
2.2 Daily variations in energy metabolism
110
2.3 Cross talk between molecular clocks and intracellular metabolic pathways
112
2.4 Peripheral organs and most brain regions: Clocks entrainable by mealtime
114
2.5 SCN: The master light-entrainable clock is sensitive to metabolic and
reward cues
115
3. Pathology
118
3.1 Circadian disturbances are associated with metabolic dysfunctions
118
3.2 Metabolic pathologies are frequently associated with circadian disturbances
122
4. Chronotherapeutics
123
4.1 Pharmacology
123
4.2 Food composition and feeding time
124
4.3 Light and other (de)synchronizers
125
5. Conclusion
126
Acknowledgments
126
References
126
Abstract
Circadian rhythmicity that has been shaped by evolution over millions of years gener-
ates an internal timing controlling the sleep
wake and metabolism cycles. The daily var-
iations between sleep/fasting/catabolism and wakefulness/feeding/anabolism are
coordinated by a master hypothalamic clock, mainly reset by ambient light. Secondary
clocks, including liver and adipose tissue, are normally synchronized by the master clock,
but they are also sensitive to feeding time, especially when meals take place during the
usual resting period. Cellular metabolism and circadian clocks are tightly interconnected
at the molecular levels. Although the suprachiasmatic clock is not shifted by mealtime
under light
-
dark conditions, nutritional cues can feedback onto it and modulate its
function under hypo- and hypercaloric (high-fat) conditions. Food-related reward cues
-
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