Amyloid-β Dynamics Are Regulated by Orexin and the Sleep-Wake Cycle

Sleep and Alzheimer's Disease

Accumulation of amyloid-β (Aβ) in the brain is thought to be the initiating event in the pathogenesis of Alzheimer's disease (AD). Aβ is a peptide secreted in a soluble monomeric form predominantly by neurons and its aggregation into toxic forms is concentration dependent. Synaptic activity regulates the release of Aβ in vivo. However, how physiological and environmental processes are involved in regulation of Aβ levels is not understood. Kang et al. (p. 1005 , published online 24 September), by performing sleep-wake studies in freely behaving animals concomitant with in vivo microdialysis, found that brain interstitial fluid levels of Aβ were significantly correlated with wakefulness and negatively correlated with sleep. Furthermore, relatively short-term (3 weeks) sleep deprivation markedly accelerated amyloid plaque deposition in amyloid precursor protein transgenic mice. Thus, sleep-wake behavior is linked to Aβ levels and abnormal sleep may be linked to AD pathogenesis.