The effects of exercise and diurnal variation on monocyte subsets and monocyte-platelet aggregates

摘要

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 15min after exercise followed by a reduction at 1h (P0·05 for both). MPAs were significantly reduced at 15min and 1h (P0·05 for both). There was significant diurnal variation in the numbers of Mon2, which were highest at 6pm and lowest at 6am. There were also significant diurnal variations in phagocytic activity of Mon1 and Mon2, which were highest at 12pm and lowest at 12am. Monocyte counts remained stable up to 2h after venipuncture. MPAs were significantly increased at 2h and increased further by 4h 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 2h of blood sampling, whereas measurement of MPAs and monocyte CD14 and CD16 expression should be performed within 1h.