Regulation of amyloid-β dynamics and pathology by the circadian clock

Nighttime restlessness and daytime drowsiness are common and early symptoms of Alzheimer's Disease (AD). This symptomology implicates dysfunctional biological timing, yet the role of the circadian system in AD pathogenesis is unknown. To evaluate the role of the circadian clock in amyloid-beta (A beta) dynamics and pathology, we used a mouse model of beta-amyloidosis and disrupted circadian clock function either globally or locally in the brain via targeted deletion of the core clock gene Bmal1. Our results demonstrate that loss of central circadian rhythms leads to disruption of daily hippocampal interstitial fluid A beta oscillations and accelerates amyloid plaque accumulation, whereas loss of peripheral Bmal1 in the brain parenchyma increases expression of Apoe and promotes fibrillar plaque deposition. These results provide evidence that both central circadian rhythms and local clock function influence A beta dynamics and plaque formation and demonstrate mechanisms by which poor circadian hygiene may directly influence AD pathogenesis.