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The effects of exercise and diurnal variation on monocyte subsets and monocyte-platelet aggregates
Eduard Shantsila1, Luke D Tapp, Benjamin J Wrigley
1University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham B18 7QH, UK. e.shantsila@bham.ac.uk
Insights
Monocyte subset Mon2 and phagocytic activity show diurnal variation. Exercise temporarily increases monocytes and reduces monocyte-platelet aggregates (MPAs), which are also affected by delayed blood processing.
Area of Science:
- Immunology
- Cardiovascular Disease Pathophysiology
- Flow Cytometry
Background:
- Monocytes are key players in cardiovascular disease.
- Limited data exist on factors influencing monocyte levels.
Purpose of the Study:
- To investigate biological and methodological factors affecting monocyte subset levels.
- To assess the impact of exercise, diurnal variation, and blood processing time on monocytes.
Main Methods:
- Flow cytometry was used to analyze three monocyte subsets (Mon1, Mon2, Mon3) and monocyte-platelet aggregates (MPAs).
- Studies included 12 healthy volunteers for exercise effects, 16 for diurnal variation, and 12 samples for delayed processing.
- Measurements were taken at various time points post-exercise, across a 24-hour cycle, and after blood collection.
Main Results:
- Monocyte subset Mon1 increased post-exercise, while MPAs decreased.
- Significant diurnal variations were observed in Mon2 counts and phagocytic activity of Mon1 and Mon2.
- Monocyte counts were stable up to 2 hours, but MPAs increased significantly after 2 hours post-sampling.
Conclusions:
- Monocyte subset Mon2 and phagocytic activity exhibit significant diurnal variation.
- Exercise transiently alters monocyte counts and MPAs.
- Timely blood sample processing is crucial: within 2 hours for monocyte subsets and within 1 hour for MPAs and CD14/CD16 expression.
Background:
Monocytes are important mediators in the pathophysiology of cardiovascular disease, but only scarce data are available on biological and methodological factors affecting their levels.
Design:
Three monocyte subsets, CD14(++) CD16(-) CCR2+ (Mon1), CD14(++) CD16(+) CCR2(+) (Mon2), CD14(+) CD16(+) CCR2(-) (Mon3), and monocyte-platelet aggregates (MPAs) were analysed by flow cytometry. The effects of treadmill exercise were assessed on 12 healthy volunteers. Diurnal variation was evaluated in 16 healthy volunteers, and the effects of delayed blood processing were measured in 12 samples.
Results:
Mon1 were increased when measured 15 min after exercise followed by a reduction at 1 h (P < 0·05 for both). MPAs were significantly reduced at 15 min and 1 h (P < 0·05 for both). There was significant diurnal variation in the numbers of Mon2, which were highest at 6 pm and lowest at 6 am. There were also significant diurnal variations in phagocytic activity of Mon1 and Mon2, which were highest at 12 pm and lowest at 12 am. Monocyte counts remained stable up to 2 h after venipuncture. MPAs were significantly increased at 2 h and increased further by 4 h after sampling.
Conclusions:
Monocyte subset Mon2 and monocyte phagocytic activity undergo significant diurnal variation. A single bout of exercise causes a temporal increase in monocytes and a reduction in MPAs. Monocyte subset counts should be analysed within 2 h of blood sampling, whereas measurement of MPAs and monocyte CD14 and CD16 expression should be performed within 1 h.
