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Circadian rhythm and melatonin
Research Guide
What is Circadian rhythm and melatonin?
Circadian rhythm and melatonin refers to the molecular, genetic, and physiological mechanisms of mammalian circadian rhythms, including the circadian clock, melatonin's regulatory role, retinal ganglion cells, peripheral clocks, phototransduction, gene expression, metabolism, oxidative stress, and health effects of sleep disruption.
This field encompasses 92,793 papers on circadian rhythms and melatonin in mammalian systems. Key components include the suprachiasmatic nucleus as the central circadian pacemaker synchronized by light via retinal ganglion cells. Disruptions in these rhythms link to metabolic, endocrine, and health outcomes such as sleep disorders.
Topic Hierarchy
Research Sub-Topics
Melatonin Receptor Signaling
This sub-topic examines the molecular mechanisms of melatonin binding to MT1 and MT2 receptors and their downstream signaling pathways in regulating circadian rhythms. Researchers investigate receptor pharmacology, G-protein coupling, and crosstalk with other hormonal systems.
Intrinsically Photosensitive Retinal Ganglion Cells
This sub-topic focuses on the role of melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) in non-visual phototransduction and circadian entrainment. Researchers study ipRGC subtypes, their projections to the suprachiasmatic nucleus, and light-induced responses.
Peripheral Circadian Clocks
This sub-topic explores the autonomous circadian oscillators in peripheral tissues like liver, muscle, and adipose, their synchronization by the suprachiasmatic nucleus, and tissue-specific clock gene functions. Researchers analyze desynchrony effects on organ physiology and metabolism.
Circadian Regulation of Metabolism
This sub-topic investigates how core clock genes like CLOCK and BMAL1 transcriptionally control glucose homeostasis, lipid metabolism, and feeding rhythms. Researchers examine clock-metabolism feedback loops and impacts of chronodisruption on obesity and diabetes.
Circadian Clock and Oxidative Stress
This sub-topic studies how circadian rhythms modulate reactive oxygen species production, antioxidant defenses, and redox-sensitive clock gene expression. Researchers explore oxidative stress as a mediator of clock disruption in aging and neurodegeneration.
Why It Matters
Circadian rhythm disruptions from sleep debt impair metabolic and endocrine function, as shown by Spiegel et al. (1999) in 'Impact of sleep debt on metabolic and endocrine function,' where restricted sleep increased cortisol and reduced glucose tolerance in healthy adults. Phototransduction by retinal ganglion cells sets the circadian clock independently of rods and cones, per Berson et al. (2002) in 'Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock,' enabling light entrainment essential for synchronizing physiology with day-night cycles. Coordination of circadian timing across mammals, detailed by Reppert and Weaver (2002) in 'Coordination of circadian timing in mammals,' underlies peripheral clocks in metabolism and gene expression, with desynchronization contributing to oxidative stress and disease pathogenesis as noted in stress mediator effects by McEwen (1998) in 'Protective and Damaging Effects of Stress Mediators.' These mechanisms impact insomnia epidemiology, affecting 10-30% prevalence rates from Ohayon (2002) in 'Epidemiology of insomnia: what we know and what we still need to learn.'
Reading Guide
Where to Start
'Coordination of circadian timing in mammals' by Reppert and Weaver (2002), as it provides a foundational overview of central and peripheral clock interactions essential for understanding mammalian circadian systems.
Key Papers Explained
Reppert and Weaver (2002) in 'Coordination of circadian timing in mammals' establishes the suprachiasmatic nucleus's role in synchronizing peripheral clocks, which Berson et al. (2002) in 'Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock' complements by detailing light input mechanisms via retinal ganglion cells. Spiegel et al. (1999) in 'Impact of sleep debt on metabolic and endocrine function' builds on this by quantifying rhythm disruption effects on metabolism, while Ohayon (2002) in 'Epidemiology of insomnia: what we know and what we still need to learn' extends to population-level health impacts. McEwen (1998) in 'Protective and Damaging Effects of Stress Mediators' connects stress mediators to circadian-mediated damage.
Paper Timeline
Most-cited paper highlighted in red. Papers ordered chronologically.
Advanced Directions
Research continues to explore molecular details of peripheral clocks and phototransduction, with no recent preprints available; foundational questions from top papers like non-visual photoreception and sleep disruption effects remain active.
Papers at a Glance
| # | Paper | Year | Venue | Citations | Open Access |
|---|---|---|---|---|---|
| 1 | Protective and Damaging Effects of Stress Mediators | 1998 | New England Journal of... | 6.4K | ✕ |
| 2 | The structure of the nervous system of the nematode <i>Caenorh... | 1986 | Philosophical transact... | 5.8K | ✕ |
| 3 | Orexins and Orexin Receptors: A Family of Hypothalamic Neurope... | 1998 | Cell | 5.5K | ✓ |
| 4 | Inflamm‐aging: An Evolutionary Perspective on Immunosenescence | 2000 | Annals of the New York... | 5.0K | ✕ |
| 5 | Hallmarks of aging: An expanding universe | 2023 | Cell | 4.8K | ✕ |
| 6 | Coordination of circadian timing in mammals | 2002 | Nature | 4.3K | ✕ |
| 7 | Epidemiology of insomnia: what we know and what we still need ... | 2002 | Sleep Medicine Reviews | 3.7K | ✕ |
| 8 | Rapamycin fed late in life extends lifespan in genetically het... | 2009 | Nature | 3.6K | ✓ |
| 9 | Impact of sleep debt on metabolic and endocrine function | 1999 | The Lancet | 3.6K | ✕ |
| 10 | Phototransduction by Retinal Ganglion Cells That Set the Circa... | 2002 | Science | 3.5K | ✕ |
Frequently Asked Questions
What role do retinal ganglion cells play in circadian rhythms?
Retinal ganglion cells mediate phototransduction to set the circadian clock, as demonstrated by Berson et al. (2002) in 'Phototransduction by Retinal Ganglion Cells That Set the Circadian Clock.' These cells respond to light independently of rods and cones, projecting to the suprachiasmatic nucleus to synchronize rhythms with environmental time.
How does sleep debt affect endocrine function?
Sleep debt elevates evening cortisol concentrations and reduces nocturnal growth hormone secretion, according to Spiegel et al. (1999) in 'Impact of sleep debt on metabolic and endocrine function.' It also impairs glucose tolerance, mimicking metabolic changes seen in normal aging.
What coordinates circadian timing in mammals?
Circadian timing in mammals is coordinated by the suprachiasmatic nucleus interacting with peripheral clocks via neural and humoral signals, as outlined by Reppert and Weaver (2002) in 'Coordination of circadian timing in mammals.' This ensures synchronized physiological processes like metabolism and gene expression.
What is the prevalence of insomnia in the population?
Insomnia affects approximately 10% of the population chronically and up to 30% with occasional symptoms, per Ohayon (2002) in 'Epidemiology of insomnia: what we know and what we still need to learn.' Factors include age, gender, and comorbidities influencing circadian disruptions.
How do stress mediators interact with circadian systems?
Stress mediators activated during circadian disruptions can protect or damage tissues, linking to disease pathogenesis through oxidative stress and inflammation, as explained by McEwen (1998) in 'Protective and Damaging Effects of Stress Mediators.' This occurs via glucocorticoid effects on gene expression and metabolism.
Open Research Questions
- ? How do peripheral clocks in metabolism interact with central circadian pacemakers under chronic sleep disruption?
- ? What specific molecular pathways in retinal ganglion cells enable non-rod/cone phototransduction for circadian entrainment?
- ? To what extent do circadian desynchronizations contribute to endocrine changes like elevated cortisol independent of sleep debt?
- ? How do genetic variations in circadian clock genes influence individual susceptibility to oxidative stress from rhythm disruptions?
Recent Trends
The field maintains 92,793 works with no specified 5-year growth rate; core insights from highly cited papers such as Reppert and Weaver on coordination and Berson et al. (2002) on phototransduction persist without new preprints or news in the last 12 months.
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