Peripheral amyloid-beta levels regulate amyloid-beta clearance from the central nervous system.

Amyloid-beta (Abeta) is cleared from the brain by both proteolytic digestion and transport across the blood-brain-barrier into the peripheral circulatory system. To investigate the role peripheral Abeta levels play in regulating Abeta brain clearance, we measured the clearance of [125I]-Abeta(1-40) injected into the brains of liver-ligated rats that allowed peripheral Abeta levels to be maintained at elevated levels for approximately one hour with/without a single peripheral bolus of unlabeled Abeta(1-40). We found that elevating peripheral Abetalevels significantly decreased [125I]-Abeta(1-40) brain clearance, thus supporting the hypothesis that peripheral Abeta levels regulate Abeta clearance from the central nervous system.