Salmon contains DHA, which helps to keep the
blood-brain barrier strong. (Public domain photo)
The Blood-Brain Barrier
The blood-brain barrier consists of tightly packed endothelial cells that line the capillaries around and inside the brain. The membranes of adjacent cells in the barrier are joined by so-called "tight junctions", which block the passage of virtually all materials. Materials are forced to travel through the cells in the barrier in order to enter the brain tissue. This enables the cells to have some control over the passage of the materials.
The blood-brain barrier does allow some substances to enter the brain, including nutrients such as oxygen, glucose, amino acids, and water. Brain cells need these chemicals in order to survive. Lipid-soluble substances can also pass through the barrier. Bacteria, other pathogens, and substances that could act as neurotoxins are blocked, however.
Role of an Omega-3 Fatty Acid
The blood-brain barrier protects the brain.
(Public domain photo)
A Transporter Protein
The protein also inhibits transcytosis in the cells. This is a process in which a substance enters a cell via vesicle formation (endocytosis), moves to the opposite membrane of the cell, and then leaves the cell in another vesicle (exocytosis). A vesicle is a small, membranous sac. The cell has other ways to transport materials, but some substances must move through the cell by transcytosis.
The Harvard researchers have bred mice with a mutated form of the gene that codes for the Mfsd2a protein. The mutation in the gene causes an altered protein to be produced. The altered protein can no longer transport lipids containing DHA. As a result, the mice develop "leaky" blood-brain barriers which allow the passage of materials that are normally blocked. In addition, the formation of the vesicles needed in transcytosis is no longer inhibited, which also increases the passage of materials. The same results occur when mice lack the Mfsd2a protein entirely.