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 In two of the studies, giving the blood of young mice to old ones
undid age-related impairments in the brain, reversing declines in
learning and memory and boosting the creation of new neurons and the
ability of the brain to change its structure in response to
experience.
The third study found that a protein in the blood of young mice
improved the ability of old ones (comparable to a 70-year-old
person) to exercise.
"I think the study is quite wonderful," said neuroscientist Eric
Kandel of Columbia University, who shared the 2000 Nobel Prize in
medicine for his studies on the molecular basis of memory, referring
to one of the brain papers.
"It suggests there may be diffusible factors in the blood that are
age-dependent, and if you can isolate these substances you might be
able to give them as dietary supplements," added Kandel, who was not
involved in the studies and at 84 continues to conduct research.
Previous studies had shown that giving young mice blood from old
mice impaired their cognitive function. But these discoveries are
the first to show the opposite: young blood can reverse age-related
impairments.
IMPROVED LEARNING AND MEMORY
In a paper published in Nature Medicine, biologists led by Tony
Wyss-Coray of Stanford University and Saul Villeda of the University
of California San Francisco described two ways of exposing old mice
to young blood. They either injected plasma from 3-month-old mice
(young adults) into 18-month olds, which are near the end of their
lifespan, or surgically connected the circulatory system of a young
mouse to that of an old one.
Old codgers exposed to young blood improved markedly on two standard
tests of learning and memory. They made fewer errors navigating a
"water maze" and they learned that a specific environment was
associated with an electric shock.
Examining the brains of aged mice exposed to young blood, the
scientists found both structural and molecular differences from
regular old brains.
The treated brains had more "dendritic spines", structures on
neurons through which one communicates with another. In addition,
the rejuvenated brains produced more of a molecule whose levels rise
during learning. And they showed a greater ability to strengthen
connections between neurons, the cellular basis for learning and
memory.
"We've shown that at least some age-related impairments in brain
function are reversible," Villeda said in a statement. "They're not
final," since exposure to young blood "counteracts aging at the
molecular, structural, functional and cognitive levels in the aged
hippocampus," the scientists wrote.
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The hippocampus plays a leading role in learning and memory,
remembering where we left our keys and what we ate for lunch, and is
one of the brain structures most subject to the ravages of both
normal aging and Alzheimer's disease. It is not clear what
component of blood acts as a fountain of youth, the Stanford
scientists said. But heating the blood abolishes the rejuvenating
effects, pointing to some protein whose structure is warped by high
temperatures.
The two other mouse studies identified what may be the Ponce de Leon
molecule: a growth factor in blood.
In one study, Lee Rubin of Harvard University and colleagues also
surgically connected the circulatory systems of an old and a young
mouse, they report in a paper to be published by Science on Friday.
Result: the old brains created more new neurons in the region that
processes smells and their sense of smell became about as sharp as
younger mice's.
"Regardless of the age of the old brain . . . young blood is still
able to rejuvenate the aged brain," Rubin's team wrote.
Earlier research had suggested that the magic elixir in young blood
is a growth factor called GDF11, which is found in both humans and
mice.
In the third study, also in Science, biologists led by Harvard's Amy
Wagers used similar techniques to expose old mice to young blood,
finding that GDF11 improved the ability of old mice to exercise.
Rubin and Wagers each expect to test GDF11 in people within three to
five years.
Stanford's Wyss-Coray believes strongly enough in the therapeutic
possibilities of young blood that he co-founded a company, Alkahest,
to test its effect in humans. "Alkahest" is the name medieval
alchemists gave to a hypothetical substance that would act as an
"immortal liquor".
(Reporting by Sharon Begley; Editing by Stephen Powell)
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