Unhealthy blood vessels in the brain are found in half of all cases of dementia worldwide.
The damage is blamed on the breakdown of the blood-brain barrier with aging. The BBB, as you may know, keeps foreign matter and too-large molecules from passing from the bloodstream into the brain.
As we get older, many experts think this barrier starts to fail, and the toxic proteins linked to Alzheimer’s — beta-amyloid and tau — are able to gain access and build up in the brain.
The theory sounds reasonable enough, but is this actually how dementia unfolds? Scientists at the University of Southern California decide to take a closer look.
What they discovered came as a complete surprise. . .
Toxic Proteins Enter the Stage Later
The blood-brain barrier is made up of tiny blood vessels (capillaries) lined with closely spaced endothelial cells.
But the aging process can cause the tight junctions to weaken and capillaries to leak. Harmful substances can now enter the brain to wreak havoc.
To understand this process more, the USC team recruited 161 older adults who were either cognitively healthy or had some minor memory impairments. The volunteers were monitored for five years.
The researchers used a battery of cognitive tests as well as neuroimaging to measure brain capillaries and look for signs of damage in the hippocampus. This area of the brain is critical to learning and memory, and one of the first to be affected in Alzheimer’s.
The results were published in Nature Medicine on the 14th of January.
The scientists found those with the greatest blood vessel damage or leakage were also the ones with the lowest scores on the cognitive tests. The effect was strong but not really surprising.
What bowled over the scientific team was that the leakage was not related in any way to amyloid and tau. The damage occurred whether these destructive proteins were present in the participant’s brain or not.
The researchers wrote in conclusion that their findings suggest “BBB breakdown is an early biomarker of human cognitive dysfunction independent of Aβ [amyloid beta] and tau.”
Essential to Maintain Healthy Blood Vessels
The study was led by Professor Berislav Zlokovic, director of the Zilkha Neurogenetic Institute at the Keck School of Medicine of USC. He said, “[It] was surprising that this blood-brain barrier breakdown is occurring independently of tau and amyloid when people have cognitive impairment on a mild level. [This] suggests it could be a totally separate process or a very early process [and] shows why healthy blood vessels are so important for normal brain functioning.”
Another member of the team, Professor Daniel Nation, added, “The results were really kind of eye opening. It didn’t matter whether people had amyloid or tau pathology; they still had cognitive impairment.”
Dr. James Pickett, head of research at Alzheimer’s Society UK, added his comments:
“This study suggests these leaks are happening very early in the development of Alzheimer’s, sometimes even before toxic proteins build up, and therefore could be used to diagnose the disease earlier, or even be a target for potential treatments.”
So it’s really important to keep blood vessels healthy and strong. This can be achieved by keeping active, practicing good lifestyle and dietary habits, and regularly consuming foods with a high concentration of L-arginine.
This nutrient helps boost production of nitric oxide to relax and expand blood vessels, allowing for better blood flow. Arginine is found in garlic and onions, spinach, kale, arugula (rocket), beets and nuts. In recent years, beet root supplements have become a popular way to keep nitric oxide levels high.
Flavonoids also strengthen blood vessels. Good sources of these plant compounds are vegetables, herbs, onions, citrus fruit, berries, apples, red grapes, grape seeds, cocoa or dark chocolate, tea and red wine.
Of course. . .long-time readers of this newsletter already know the beta-amyloid and tau theory is full of holes (and I’m not talking about the holes in our BBB). This study provides further confirmation that we need to look elsewhere if we’re to prevent or treat dementia.