Plasticity of circadian clocks and consequences for metabolism.
The increased prevalence of metabolic disorders and obesity in modern society, together with the widespread use of artificial light at night, have led researchers to investigate whether altered patterns of light exposure contribute to metabolic disorders. This article discusses the experimental evidence that perturbed environmental cycles induce rhythm disorders in the circadian system, thus leading to metabolic disorders. This notion is generally supported by animal studies. Distorted environmental cycles, including continuous exposure to light, affect the neuronal organization of the central circadian pacemaker in the suprachiasmatic nucleus (SCN), its waveform and amplitude of the rhythm in electrical activity. Moreover, repeated exposure to a shifted light cycle or the application of dim light at night are environmental cues that cause a change in SCN function. The effects on the SCN waveform are the result of changes in synchronization among the SCN's neuronal cell population, which lead consistently to metabolic disturbances. Furthermore, we discuss the effects of sleep deprivation and the time of feeding on metabolism, as these factors are associated with exposure to disturbed environmental cycles. Finally, we suggest that these experimental studies reveal a causal relationship between the rhythm disorders and the metabolic disorders observed in epidemiological studies performed in humans.
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
C P
CP
Coomans
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
E A
EA
Lucassen
Department of Medicine, Division of Endocrinology, Leiden University Medical Center, Leiden, Netherlands.|Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands.
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S
Kooijman
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
K
K
Fifel
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
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T
Deboer
Department of Medicine, Division of Endocrinology, Leiden University Medical Center, Leiden, Netherlands.|Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, Netherlands.
P C N
PC
Rensen
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
S
S
Michel
Department of Molecular Cell Biology, Laboratory for Neurophysiology, Leiden University Medical Center, Leiden, Netherlands.
J H
JH
Meijer
D000818:Animals; D000066670:Cell Plasticity; D021081:Chronobiology Disorders / Q000150:complications*; D057906:Circadian Clocks / Q000502:physiology*; D004435:Eating / Q000502:physiology; D004734:Energy Metabolism; D006801:Humans; D008029:Lighting / Q000009:adverse effects*; D008659:Metabolic Diseases / Q000209:etiology*; D017440:Photoperiod; D012892:Sleep Deprivation / Q000378:metabolism; D013493:Suprachiasmatic Nucleus / Q000503:physiopathology*
circadian; desynchronization; light; metabolic disorders; suprachiasmatic nucleus