Roles of Peripheral Clocks: Lessons from the Fly

Circadian rhythms are 24-h oscillations driven by a hypothalamic master oscillator that entrains peripheral clocks in almost all cells, tissues and organs. Circadian misalignment, triggered by industrialization and modern lifestyles, has been linked to several pathological conditions, with possible impairment of the quality or even the very existence of life. Living organisms are continuously exposed to air pollutants, and among them, ozone or particulate matters (PMs) are considered to be among the most toxic to human health. In particular, exposure to environmental stressors may result not only in pulmonary and cardiovascular diseases, but, as it has been demonstrated in the last two decades, the skin can also be affected by pollution. In this context, we hypothesize that chronodistruption can exacerbate cell vulnerability to exogenous damaging agents, and we suggest a possible common mechanism of action in deregulation of the homeostasis of the pulmonary, cardiovascular and cutaneous tissues and in its involvement in the development of pathological conditions.

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Integrative coordination of circadian mammalian diversity:neuronal networks and peripheral clocks

Progress in Neurobiology ◽

10.1016/s0301-0082(97)00069-5 ◽

1998 ◽

Vol 54 (1) ◽

pp. 87-97 ◽

Cited By ~ 15

Author(s):

O Ikonomov

Keyword(s):

Peripheral Clocks

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Circadian molecular clocks tick along ontogenesis

Physiological Research ◽

10.33549/physiolres.931458 ◽

2008 ◽

pp. S139-S148

Author(s):

A Sumová ◽

Z Bendová ◽

M Sládek ◽

R El-Hennamy ◽

K Matějů ◽

...

Keyword(s):

Current Model ◽

Complex Structure ◽

Postnatal Period ◽

Circadian System ◽

Molecular Clocks ◽

Suprachiasmatic Nuclei ◽

Intercellular Coupling ◽

Peripheral Clocks ◽

Complete Set ◽

Formal Properties

The circadian system controls the timing of behavioral and physiological functions in most organisms studied. The review addresses the question of when and how the molecular clockwork underlying circadian oscillations within the central circadian clock in the suprachiasmatic nuclei of the hypothalamus (SCN) and the peripheral circadian clocks develops during ontogenesis. The current model of the molecular clockwork is summarized. The central SCN clock is viewed as a complex structure composed of a web of mutually synchronized individual oscillators. The importance of development of both the intracellular molecular clockwork as well as intercellular coupling for development of the formal properties of the circadian SCN clock is also highlighted. Recently, data has accumulated to demonstrate that synchronized molecular oscillations in the central and peripheral clocks develop gradually during ontogenesis and development extends into postnatal period. Synchronized molecular oscillations develop earlier in the SCN than in the peripheral clocks. A hypothesis is suggested that the immature clocks might be first driven by external entraining cues, and therefore, serve as "slave" oscillators. During ontogenesis, the clocks may gradually develop a complete set of molecular interlocked oscillations, i.e., the molecular clockwork, and become self-sustained clocks.

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An ultradian feeding schedule in rats affects metabolic gene expression in liver, brown adipose tissue and skeletal muscle with only mild effects on circadian clocks

10.20944/preprints201809.0201.v1 ◽

2018 ◽

Author(s):

Paul de Goede ◽

Satish Sen ◽

Yan Su ◽

Ewout Foppen ◽

Vincet-Joseph Poirel ◽

...

Keyword(s):

Gene Expression ◽

Skeletal Muscle ◽

Feeding Behavior ◽

Circadian Clocks ◽

Daily Rhythm ◽

Feeding Schedule ◽

Metabolic Gene Expression ◽

Brown Adipose ◽

Peripheral Clocks ◽

Master Clock

Restricted feeding is well known to affect expression profiles of both clock and metabolic genes. However, it is unknown whether these changes in metabolic gene expression result from changes in the molecular clock or in feeding behavior. Here we eliminated the daily rhythm in feeding behavior by providing 6-meals evenly distributed over the light/dark-cycle. Animals on this 6-meals-a-day feeding schedule retained the normal day/night difference in physiological parameters including body temperature and locomotor activity. The daily rhythm in respiratory exchange ratio (RER), however, was significantly phase-shifted through increased utilization of carbohydrates during the light phase and increased lipid oxidation during the dark phase. This 6-meals-a-day feeding schedule did not have a major impact on the clock gene expression rhythms in the master clock but did have mild effects on peripheral clocks. By contrast, genes involved in glucose and lipid metabolism showed differential expression. Concluding, eliminating the daily rhythm in feeding behavior in rats does not affect the master clock and only mildly affects peripheral clocks, but disturbs metabolic rhythms in liver, skeletal muscle and brown adipose tissue in a tissue-dependent manner. Thereby a clear daily rhythm in feeding behavior strongly regulates timing of peripheral metabolism, separately from circadian clocks.

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Multi-Modal Regulation of Circadian Physiology by Interactive Features of Biological Clocks

Biology ◽

10.3390/biology11010021 ◽

2021 ◽

Vol 11 (1) ◽

pp. 21

Author(s):

Yool Lee ◽

Jonathan P. Wisor

Keyword(s):

Circadian Clock ◽

Neurological Diseases ◽

Night Shift ◽

Hormone Secretion ◽

Local Environment ◽

Biological Clocks ◽

Tightly Coupled ◽

Peripheral Clocks ◽

Living Organisms ◽

Circadian Physiology

The circadian clock is a fundamental biological timing mechanism that generates nearly 24 h rhythms of physiology and behaviors, including sleep/wake cycles, hormone secretion, and metabolism. Evolutionarily, the endogenous clock is thought to confer living organisms, including humans, with survival benefits by adapting internal rhythms to the day and night cycles of the local environment. Mirroring the evolutionary fitness bestowed by the circadian clock, daily mismatches between the internal body clock and environmental cycles, such as irregular work (e.g., night shift work) and life schedules (e.g., jet lag, mistimed eating), have been recognized to increase the risk of cardiac, metabolic, and neurological diseases. Moreover, increasing numbers of studies with cellular and animal models have detected the presence of functional circadian oscillators at multiple levels, ranging from individual neurons and fibroblasts to brain and peripheral organs. These oscillators are tightly coupled to timely modulate cellular and bodily responses to physiological and metabolic cues. In this review, we will discuss the roles of central and peripheral clocks in physiology and diseases, highlighting the dynamic regulatory interactions between circadian timing systems and multiple metabolic factors.

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