Impaired transport of DHA disrupts the blood-brain barrier.
Lipid rafts – cholesterol-filled “bubbles” found in the cell membrane – serve as staging areas for many cellular activities. One type of lipid raft, called caveolae, facilitates the transport of substances across the membrane of endothelial cells. Findings from a 2017 study demonstrate that suppression of caveolae-mediated transport in brain endothelial cells protects the integrity of the blood-brain barrier.
The blood-brain barrier is a highly selective semi-permeable barrier made up of endothelial cells connected via tight junctions. This barrier separates the circulating blood from the brain’s extracellular fluid and prevents the entry of substances that may be neurotoxic. Disruption of the blood-brain barrier has been implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, and multiple sclerosis, among others.
The investigators' previous research showed that a critical player in blood-brain barrier function is Mfsd2a, a transmembrane protein found exclusively on the endothelial cells that line blood vessels on the barrier. Mfsd2a participates in lipid transport and is the sole means by which lysophospholipid DHA, the brain’s preferred form of DHA (a type of omega-3 fatty acid) is delivered to the brain.
Using mice that carried a mutation that blocked Mfsd2a’s capacity to transport DHA, the investigators assessed blood-brain barrier function as well as caveolae formation and activity in the animals' brains. Then they compared the lipid composition of brain endothelial cells to lung epithelial cells, which lack Mfsd2a.
They found that mice that lacked Mfsd2a function had leakier blood-brain barriers and greater caveolae formation and activity than normal mice. They also found that brain endothelial cells had higher lipid concentrations than lung epithelial cells. The most abundant lipid in the brain endothelial cells was DHA, which was found in concentrations that were two to five times higher.
These findings suggest that Mfsd2a-mediated transport of lipids, particularly DHA, impairs caveolae activity, thereby preserving blood-brain integrity. Learn more about links between Mfsd2a, DHA, and brain health in this open-access peer-reviewed article by Dr. Rhonda Patrick..
