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IL-6 and its circadian secretion in humans
A N Vgontzas1, E O Bixler, H-M Lin
1Sleep Research and Treatment Center, Department of Psychiatry, Penn State College of Medicine, Hershey, PA 17033, USA. axv3@psu.edu
Neuroimmunomodulation
|May 21, 2005
Summary
Interleukin-6 (IL-6) is a key sleep mediator, influencing sleepiness and circadian rhythms. Its levels fluctuate with sleep patterns, impacting sleep quality and daytime alertness in both healthy individuals and those with sleep disorders.
Area of Science:
- Immunology
- Sleep Medicine
- Chronobiology
Background:
- Interleukin-6 (IL-6) is a cytokine implicated in various physiological and pathophysiological processes.
- IL-6 secretion exhibits a circadian rhythm, potentially linking it to sleep-wake regulation.
- Elevated IL-6 levels are observed in sleep disorders like narcolepsy and obstructive sleep apnea.
Purpose of the Study:
- To investigate the role of IL-6 as a mediator of sleepiness.
- To characterize the circadian pattern of IL-6 secretion in relation to sleep.
- To examine age-related differences in IL-6 circadian rhythm.
Main Methods:
- Analysis of 24-hour IL-6 secretory patterns in healthy young and old adults.
- Application of cosinor analysis to 'detrended' IL-6 data.
- Review of existing literature on IL-6 and sleep in humans and animal models.
Main Results:
- IL-6 exhibits a biphasic circadian pattern in young adults, with distinct nadirs and zeniths.
- Sleep deprivation and sleep disorders alter IL-6 secretion patterns, often leading to daytime peaks.
- IL-6's circadian rhythm is flattened in older adults compared to younger individuals.
- IL-6 demonstrates somnogenic properties and a diurnal rhythm in rats.
Conclusions:
- IL-6 acts as a mediator of sleepiness, with its circadian pattern reflecting the homeostatic drive for sleep.
- Age influences the robustness of IL-6's circadian rhythm.
- Understanding IL-6's role provides insights into sleep regulation and sleep disorders.