Diurnal variation in serum levels of cartilage oligomeric matrix protein in patients with knee osteoarthritis or rheumatoid arthritis

Abstract

Objective: To monitor changes in serum concentrations of cartilage oligomeric matrix protein (COMP) during a 24-h period to determine any diurnal variation, and to estimate the half life of COMP in the circulation in patients with symptomatic knee osteoarthritis and in those with rheumatoid arthritis. Methods: Serum samples were drawn every 4 h (7 samples/patient over 24 h) in 10 patients with knee osteoarthritis and 14 patients with rheumatoid arthritis. Osteoarthritis was defined radiographically and clinically (American College of Rheumatology (ACR) criteria) and rheumatoid arthritis according to the 1987 ACR criteria. Serum COMP was measured by sandwich ELISA. A statistical model for the diurnal variation in the COMP levels was developed using the computer program NONMEM. Results: No considerable changes in COMP levels were observed during the day between 08:00 and 21:00 in either group. A significant decrease in serum COMP was apparent during bed rest at night, reaching the lowest levels between 04:00 and 05:00 (p,0.03 or better v all other time points) in patients with osteoarthritis and in those with rheumatoid arthritis. From the rate of decreasing serum COMP levels, a putative half life of COMP in the circulation was estimated to be 7.4 h. Conclusion: During normal daytime activities, serum COMP levels are constant. The decrease during the night indicates a rapid elimination of COMP once it has reached the circulation. The stable COMP levels during the day suggest that it is not necessary to further standardise the time of serum sampling in clinical practice.

Within‐day variation and influence of physical exercise on circulating Galectin‐3 in patients with rheumatoid arthritis and healthy individuals

“…Similar studies on patients with specific diseases have not been conducted in the past. Although Galectin-3 in serum did not exhibit daytime variation, it should be borne in mind that potential changes between 10 p.m. and blood sampling in the morning may have been missed as reported for cartilage oligomeric matrix protein (COMP), an important constituent of articular cartilage [19]. While the cellular origin of Galectin-3 in RA cannot be determined from the present study, the elevated baseline values in the RA cohorts and previously published results obtained from patients with advanced RA favour the view that the increased Galectin-3 serum levels in RA are derived from the diseased joints.…”

Change in serum COMP concentration due to ambulatory load is not related to knee OA Status

“…It is possible that the further decrease in serum COMP concentration throughout the day in the current study reflects the diurnal variation in COMP concentration. 25 In addition, activity following the walking exercise in the current study was minimized and closely monitored. It is possible that patients in a previous study 10 were more active following the exercise than patients in the current study, resulting in the return of serum COMP levels to baseline only 6 h after the exercise.…”

The brain–joint axis in osteoarthritis: nerves, circadian clocks and beyond

“…The rhythmic clock-controlled genes include those involved in extracellular matrix remodelling, apoptosis and oxidative stress pathways 50,51 . Diurnal variations in serum levels of cartilage oligomeric matrix protein, hyaluronic acid, keratan sulfate, aggrecan, collagen type II and TGFβ have also been reported 52,53 . Several brain-controlled systemic factors, such as hormone rhythms (for example, glucocorticoids) and core body temperature cycles, are able to entrain the cartilage circadian rhythm 50 .…”