The blood-brain barrier actively imports 92 blood proteins

A Gladstone team used protein labelling to track 861 plasma proteins in mice and found that the blood-brain barrier selectively allowed 92 into the brain, routing different proteins to specific cells. Liver-derived APOA1 supported astrocytes and neuronal connections. In Alzheimer mouse models, the barrier reduced import of APOA1 and other protective proteins before physical leakage appeared, alongside connection and behavioural changes. Mice engineered to produce more liver APOA1 showed fewer disease signs. The work reframes the barrier as an active transport interface, but it remains mouse and mechanism evidence; it does not show that APOA1 supplementation can prevent or treat Alzheimer's disease in people.