Clearance of amyloid beta-peptide from brain: transport or metabolism?

We read with interest the article by Iwata et al.1 in the February 2000 issue of Nature Medicine suggesting a major degrading catabolic pathway for Alzheimer amyloid -peptide (A) in brain. Our own work, however, has indicated that, in addition to production of the peptide, transport of A across the microvascular endothelium (that is, the site of the blood−brain barrier) is essential in controlling A levels in the brain2, 3.