@article{3161988,
    title = "Circadian rhythmicity, variability and correlation of interleukin-6
levels in plasma and cerebrospinal fluid of healthy men",
    author = "Agorastos, Agorastos and Hauger, Richard L. and Barkauskas, Donald A. and and Moeller-Bertram, Tobias and Clopton, Paul L. and Haji, Uzair and and Lohr, James B. and Geracioti, Jr., Thomas D. and Patel, Piyush M. and and Chrousos, George P. and Baker, Dewleen G.",
    journal = "Psychoneuroendocrinology",
    year = "2014",
    volume = "44",
    pages = "71-82",
    publisher = "PERGAMON-ELSEVIER SCIENCE LTD",
    issn = "0306-4530",
    doi = "10.1016/j.psyneuen.2014.02.020",
    keywords = "Interleukin-6 (IL-6); Cytokines; Circadian; Immune; Inflammation; Blood
brain-barrier (BBB); Cerebrospinal fluid (CSF); Sleep; Stress;
Neuroimmunology",
    abstract = "Background: Interleukin-6 (IL-6) is a cytokine with pleiotropic actions
in both the periphery of the body and the central nervous system (CNS).
Altered IL-6 secretion has been associated with inflammatory
dysregulation and several adverse health consequences. However, little
is known about the physiological circadian characteristics and dynamic
inter-correlation between circulating and CNS IL-6 levels in humans, or
their significance.
Methods: Simultaneous assessment of plasma and cerebrospinal fluid (CSF)
IL-6 levels was performed hourly in 11 healthy male volunteers over 24
h, to characterize physiological IL-6 secretion levels in both
compartments.
Results: IL-6 levels showed considerable within- and between-subject
variability in both plasma and CSF, with plasma/CSF ratios revealing
consistently higher levels in the CSF. Both CSF and plasma IL-6 levels
showed a distinctive circadian variation, with CSF IL-6 levels
exhibiting a main 24 h, and plasma a biphasic 12 h, circadian component.
Plasma peaks were roughly at 4 p.m. and 4 a.m., while the CSF peak was
at around 7 p.m. There was no correlation between coincident CSF and
plasma IL-6 values, but evidence for significant correlations at a
negative 7-8 h time lag.
Conclusions: This study provides evidence in humans for a circadian IL-6
rhythm in CSF and confirms prior observations reporting a plasma
biphasic circadian pattern. Our results indicate differential IL-6
regulation across the two compartments and are consistent with local
production of IL-6 in the CNS. Possible physiological significance is
discussed and implications for further research are highlighted.
Published by Elsevier"
}