Could a leak in the blood-brain barrier cause poor memory?
From:
The University of Washington
March
18, 2021 – Have you forgotten where you laid your keys? Ever wondered
where you had parked your car? Or having trouble remembering the name of the
new neighbor? Unfortunately, these things seem to get worse as one gets older.
A big question for researchers is where does benign forgetfulness end and true
disease begin?
One of the keys to having a healthy
brain at any age is having a healthy blood-brain barrier, a complex interface
of blood vessels that run through the brain. Researchers reviewed more than 150
articles to look at what happens to the blood-brain barrier as we age. Their
findings were published
March 15 in Nature Aging.
Whether the changes to the blood-brain
barrier alters brain function is still up for debate. But research
shows the blood-brain barrier leaks as we age, and we lose cells called
pericytes.
“It turns out very little is known how
the blood-brain barrier ages,” said lead author William Banks, a gerontology
researcher at the University of Washington School of Medicine and at the
Veterans Affairs Puget Sound Health Care System. “It’s often hard to tell
normal aging from early disease.”
The blood-brain barrier, discovered in
the late 1800s, prevents the unregulated leakage of substances from blood into
the brain. The brain is an especially sensitive organ and cannot tolerate
direct exposure to many of the substances in the blood. Increasingly,
scientists have realized that the blood-brain barrier also allows many
substances into the brain in a regulated way to serve the nutritional needs of
the brain. It also transports informational molecules from the blood to the
brain and pumps toxins out of the brain. A malfunctioning blood-brain barrier
can contribute to diseases such as multiple sclerosis, diabetes,
and Alzheimer’s.
Before scientists can understand how
such malfunctioning can contribute to the diseases of aging, they need to
understand how a healthy blood-brain barrier normally ages.
Research shows that healthy aging
individuals have a very small leak in their blood-brain barrier. This leakage
is associated with some measures of the benign forgetfulness of aging,
considered by most scientists to be normal. But could this leak and the
difficulties in recall be the early stages of Alzheimer’s disease?
When a person carries the ApoE4 allele,
the strongest genetic risk of Alzheimer’s risk, researchers said there is an
acceleration of most of the blood-brain barrier age-related changes.
People with ApoE4 have a hard time
getting rid of amyloid beta peptide in their brains, which causes an
accumulation of plaque. With healthy aging, the pumps in the blood-brain
barrier work less efficiently in getting rid of the amyloid beta peptide. The
pumps work even less well in people with Alzheimer’s disease.
Another key finding in the review is
that as we age, two cells begin to change in the blood-brain barrier: pericytes
and astrocytes.
Recent work suggests that the leak in
the blood-brain barrier that occurs with Alzheimer’s may be due to an
age-related loss of pericytes. Astrocytes, by contrast, seem to be overactive.
Recent work suggests that preserving pericyte function by giving the factors
that they secrete or even transplanting them could lead to a healthier
blood-brain barrier.
Some research suggests that pericyte
health can be preserved by some of the same interventions that extend lifespan,
such as regular exercise, caloric restriction, and rapamycin.
Other findings raise the question of
whether the brain’s source of nutrition and its grip on control of the immune
and endocrine systems could deteriorate with aging. Another finding raises the
possibility that the rate at which many drugs are taken up by the brain may
explain why older folks sometimes have different sensitivities to drugs than
their children or grandchildren.
https://newsroom.uw.edu/news/could-leak-blood-brain-barrier-be-cause-poor-memory
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