Plasma amyloid‐β dynamics are regulated by the sleep‐wake cycle

Background It has been reported that sleep is an important physiological process and conducive to the elimination of brain metabolites and the recovery of brain function. Growing evidence suggested that sleep disorders were related to increased risk of AD and Aβ accumulation in the brain. Although peripheral Aβ clearance is associated with brain Aβ deposition, but the relationship between sleep‐wake cycle and plasma Aβ levels is unclear. Method Thirty cognitively normal healthy adults (aged 29.07 ± 8.12), sixteen males (53.33%), were recruited. Participants underwent normal sleep and peripheral blood samples were collected every three hours between 20:00 and 8:00 the next day. Plasma Aβ40, Aβ42, total tau, phosphorylated tau 181 (P‐tau), soluble low‐density lipoprotein receptor‐related protein (sLRP1) and soluble receptors for advanced glycation end products (sRAGE) levels were measured using ELISA kits. Result Plasma Aβ40 concentration at 5:00 decreased significantly compared with plasma level at 23:00 (p=0.041), and there is a dynamic tendency of decreasing after sleep onset and increasing after awake, which is in accordance with the sleep‐wake cycle. Furthermore, Aβ40 and Aβ42 levels were positively correlated with plasma sLRP1 (Aβ40: r=0.1791, p=0.0283; Aβ42: r=0.1780, p=0.0293). However, there was no significant dynamic change in Aβ42, Tau, P‐tau, Tau, sLRP1 and sRAGE levels in twelve hours. Conclusion Plasma Aβ40 dynamics are regulated by the sleep‐wake cycle, and it may play a positive feedback regulating role in sLRP1 level.