Chocolade en thee tegen schade na beroerte*
Uit een studie, weliswaar met muizen, blijkt dat de bioactieve stoffen catechinen
beschermend werken bij beroertes. Zij
beperken de aangerichte schade duidelijk door twee bestaande
beschermingsmechanismes van de hersenen verder te stimuleren. Cathechinen worden
vooral aangetroffen in cacao, chocolade en (groene) thee. Slechts kleine
hoeveelheden catechinen zijn nodig om voor bescherming te zorgen. Uit een
eerdere studie van dezelfde onderzoeker bleek
resveratrol ook de hersenen te beschermen.
Dark Chocolate Compound Could Protect Against Stroke Brain Injury
New research on mice suggests that a compound found in dark chocolate and tea
may protect against brain injury from a stroke.
You can read about the study led by Johns Hopkins University School of Medicine
in Baltimore, Maryland, in the Journal of Cerebral Blood Flow and Metabolism.
We already know from previous epidemiological studies that plant foods rich in
polyphenols, such as flavanols (not to be confused with flavonols), can lower
the risk of ischemic heart disease (disease that results from reduced blood
supply to the heart), but how it does so is not clear.
In this study, Dr Sylvain Doré, associate professor of anesthesiology and
critical care medicine and pharmacology and molecular sciences at the Johns
Hopkins University School of Medicine, and colleagues, investigated whether
epicatechin (EC), a flavanol found in in cocoa and tea, protected mice against
brain damage from an ischemic stroke (where the blood supply to the brain is cut
off).
For the study, they fed mice with 5, 15, or 30 mg/kg doses of EC and then 90
minutes later induced an ischemic stroke by essentially cutting off the blood
supply to their brains (middle cerebral artery occlusion, MCAO).
They found that the treated mice had significantly less brain damage (infarcts)
and reduction in brain function ("decreased neurologic deficit scores, NDS")
compared to mice that had not been fed with EC.
They also found that mice given 30 mg/kg of EC 3.5 hours after an induced stroke
(MCAO) also had significantly less brain damage and NDS. However, when given 6
hours later, there was no protective effect.
(Usually with humans, treatments to prevent brain damage from strokes have to be
given within a two- to three-hour window.)
Doré told the media these findings suggest that EC stimulates two already well
researched pathways that shield brain cells from damage: these are the pathways
used by the enzyme heme oxygenase 1 (HO1) and the transcriptional factor Nrf2.
When they did the same tests on mice bred to lack these pathways, they found
that the protective effect of EC on the brain was mostly abolished, and the
brain cells died after the induced stroke.
The researchers hope their findings will help us better understand how to
research acute stroke damage, and how to protect against chronic brain-wasting
diseases such as Alzheimer's and other age-related cognitive disorders.
However, they were keen to point out this was not a clinical trial and this
study should not be an excuse for us to go out and start eating masses of
chocolate, which is also high in calories and fat. People should eat a diet high
in a variety of fruits and vegetables, they said.
Research interest in epicatechin started in earnest with investigations of the
eating habits of remote populations of Kuna Indians who live on islands off the
coast of Panama.
These remote populations appeared to have low rates of heart disease, but when
they moved away from their islands they were no longer protected from heart
problems.
Genetic studies confirmed that the protection came from their environment rather
than their genes, and scientists eventually settled on the likely cause being
the very bitter epicatechin-rich cocoa drink they consumed when they lived on
their island.
Doré believes the amounts of epicatechin needed to confer protective benefits
might be quite small because their effect is indirect: they probably "jump-start"
the protective pathways that are already there:
"Epicatechin itself may not be shielding brain cells from free radical
damage directly, but instead, epicatechin, and its metabolites, may be prompting
the cells to defend themselves," said Doré.
"Even a small amount may be sufficient," he added.
He also cautioned that not all dark chocolates are the same: they contain
differing amounts of bioactive epicatechin:
"The epicatechin found in dark chocolate is extremely sensitive to changes
in heat and light," said Doré, explaining that you have to make sure you
don't destroy the compound when you make the chocolate.
"Only few chocolates have the active ingredient. The fact that it says 'dark
chocolate' is not sufficient," he warned.
The National Institutes of Health and the American Heart and Stroke Association
funded the study.
"The flavanol (-)-epicatechin prevents stroke damage through the Nrf2/HO1
pathway."
Zahoor A Shah, Rung-chi Li, Abdullah S Ahmad, Thomas W Kensler, Masayuki
Yamamoto, Shyam Biswal and Sylvain Doré.
J Cereb Blood Flow Metab, advance online publication, DOI:10.1038/jcbfm.2010.53
Source: Johns Hopkins Medicine. (Augustus 2010)
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