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Strawberries Boost Memory
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Mothers have long exhorted their children to eat their fruit and vegetables. But
once kids are beyond mom's watchful eye, the hated greens often go the way
of Barbie dolls and power rangers. Now, there's another reason to reach for
colorful fruits past adolescence.
Fisetin, a naturally occurring chemical commonly found in strawberries and
other fruits and vegetables, stimulates signaling pathways that enhance long-
term memory, report researchers at the Salk Institute for Biological Studies.
Roughly one third of people age 60 and over suffer from memory and recall
woes. As the average age of the U.S. population climbs, the number of people
ravaged by Alzheimer's disease and other forms of dementia continues to rise.
"Since the development of a basic understanding of the biochemical
pathways involved in memory formation, the holy grail of CNS research in the
pharmaceutical industry is the identification of a safe, orally active drug that
activates memory-associated pathways and enhances memory," said lead
author Pamela Maher, Ph.D., a researcher in the Cellular Neurobiology
Laboratory at the Salk Institute.
Maher hit upon the beneficial effects of fisetin when she screened a collection
of flavonoids, substances with anti-oxidant activities found in many plants, for
their neuroprotective abilities in tissue culture models of neurodegenerative
disease.
Maher found that some of those compounds, including fisetin, induced
differentiation or maturation of neural cells.
"That suggested to us that these compounds might be particularly beneficial,
since they might not only protect neural cells from dying but might be able to
promote new connections between nerve cells," Maher explained.
Interestingly the signaling pathway activated by fisetin in neural differentiation
also played a role in memory formation, a process neuroscientists call "long-
term potentiation" or LTP. LTP allows memories to be stored in the brain by
strengthening connections between neurons.
"We wanted to find out whether we could detect any effects of fisetin on long-
term potentiation and the formation of memories in animals," Maher recalled.
Since the hippocampus plays an important role in establishing new
memories, Maher, and co-authors Tatsuhiro Akaishi and Kazuho Abe, both at
Musashino University in Tokyo, Japan, extended the study and found that
fisetin activates the same signaling pathway in rat hippocampal tissues and
also induces LTP.
Next, they tested fisetin's effects in a so-called object discrimination test in
which got to explore two objects for a certain amount of time. The next day,
one of the objects was replaced with a novel one. If the mice remembered the
object from the day before, they spent less time exploring the old one and
instead turned their attention to the novel object. Indeed, mice administered a
single dose of fisetin could better recall familiar objects. In fact, fisetin worked
almost as well as rolipram, a substance known to enhance memory.
Memory loss caused by neurodegenerative disease occurs due to loss of
neurons, a situation very different from that of healthy mice. Thus the ultimate
goal is to stop neuronal loss. Nevertheless, memory-enhancing drugs can
improve Alzheimer's disease symptoms.
The observations that fisetin protects and promotes survival of cultured
neurons and boosts memory in healthy mice make it a promising candidate
for further studies.
Fisetin is readily available in strawberries but is also found in tomatoes,
onions, oranges, apples, peaches, grapes, kiwifruit and persimmons. Gingko
biloba leaves, while rich in other flavonoids, do not contain fisetin.
While eating strawberries sounds like an enjoyable alternative to popping a
pill, Maher cautions that it would take about 10 pounds a day to achieve a
beneficial effect, which might prove too much even for the most avid
strawberry lovers.
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