Platelet Function regulated by Circadian rhythm

In a study published in PLoS ONE, researchers at Brigham and Women’s Hospital (BWH) have demonstrated that human platelet function is regulated by the circadian system, causing a peak in platelet activation analogous to the morning peak seen in adverse cardiovascular events.

Lead author and Assistant Professor of Medicine at the Division of Sleep Medicine at BWH, Frank Scheer, PhD, said: “Cardiovascular disease is still the number one cause of death in developed countries, and we know major adverse cardiovascular events do not occur at random, but are more frequent in the morning. Understanding the underlying factors for this morning peak in adverse events has the potential to address this pattern and decrease the risk.”
Also referred to as the body’s internal clock, the circadian rhythm was found to regulate platelet function. Analogous to the morning peak observed during adverse cardiovascular events such as myocardial infarction and stroke, the circadian rhythm caused a peak in platelet activation. A high level of platelet activation can influence blood-clotting resulting in adverse cardiovascular events. According to Scheer, since this finding imitates the pattern of morning peaks seen in cardiovascular risk, it could imply that platelet function is one of the factors that contributes to this morning peak in adverse cardiovascular events.

Scheer said, “Further study is required to test whether this circadian pattern in platelet activation, as demonstrated here in healthy subjects, is shifted in time or has different rhythm amplitude in people with cardiovascular disease.”
The study adopted a forced desynchrony protocol. As per the protocol, healthy young subjects were required to live a 20-hour day comprising 12 cycles in a dim-light, time-free, and controlled environment. The protocol design permitted the evaluation of what effect the internal circadian timing system might have on platelet function, independent of effects of the sleep/wake cycle and other behavioral or environmental changes. Flow cytometry and whole blood platelet aggregation were used to assess platelet function.

Better understanding of the underlying mechanisms causing the morning peak is expected to be of significant clinical relevance. Dr. Scheer said, “We believe it’s likely that there are many other factors that contribute to the peak in adverse cardiovascular events in the morning. The next steps in addressing this issue are to further investigate control mechanisms involved in the circadian rhythm in platelet function, the role of the circadian system in other cardiovascular risk factors, and the changes in circadian control of cardiovascular risk factors in vulnerable populations.”

The National Institutes of Health funded this research.

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