Circadian characteristics of interleukin-6 in blood and urine of clinically healthy men.
The cytokine interleukin-6 (IL-6) is a multi-functional small peptide molecule that is produced by various types of lymphoid and non-lymphoid cells and plays a central role in hematopoiesis, host defense mechanisms, and acute phase reactions, including regulation of inflammatory and immune responses. A high-sensitivity ELISA assay was applied to serum (S) and urine (U) samples available from 10 men (median age = 50y, range = 46-71y) in order to compare circadian characteristics of IL-6 between assays and in 2 biological fluids. S and U samples were collected at 3-h intervals for 24hrs beginning at 19:00h on May 14, 1993 (8 samples/subj) and frozen at -25 degrees C until analysis. IL-6 in U was adjusted for time & volume (pg/hr) and assigned to midpoint of collection interval. A significant time-effect was found by ANOVA and a high-amplitude circadian rhythm was detected by the least-squares fit of a 24-hr &/or 24+12-hr cosine for each assay. Higher serum IL-6 values were detected throughout the night, with a peak at 01:00h, and lower values throughout the day, with a nadir at 10:00h. In contrast, IL-6 values in urine were highest during the day, with a major peak in the afternoon at 17:30h and a minor peak at 08:30h, and lowest values overnight, with a nadir at 23:30h. Of interest, the rhythm in urinary IL-6 concentration (pg/ml) was more prominent than hourly excretion rate (pg/hr). Thus, endogenous IL-6 (and possibly other cytokine) levels may be significantly influenced by their large and predictable day-night variations and the biological fluid used.
Sothern
R B
RB
Rhythmometry Laboratory, St. Paul-Ramsey Medical Center, Minneapolis, MN 55455, USA.
Roitman-Johnson
B
B
Kanabrocki
E L
EL
Yager
J G
JG
Fuerstenberg
R K
RK
Weatherbee
J A
JA
Young
M R
MR
Nemchausky
B M
BM
Scheving
L E
LE
D000368:Aged; D002909:Chronobiology Phenomena / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D003627:Data Interpretation, Statistical; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015850:Interleukin-6 / Q000097:blood* / Q000652:urine*; D008297:Male; D008875:Middle Aged
D015850:Interleukin-6