Omega-3
vetzuur tegen de ziekte van Alzheimer.*
Het
omega-3 vetzuur Docosahexaeenzuur
(DHA)
blijkt twee markers voor de ziekte van Alzheimer te kunnen verminderen. Het
lijkt erop dat voeding rijk aan dit omega-3 vetzuur DHA de ziekte van Alzheimer
kan voorkomen. Dit blijkt althans uit een studie met genetisch aangepaste
muizen. DHA kan de vorming van het proteïne tau tegengaan.
Tau
veroorzaakt neurofibrillaire kluwens , een marker voor Alzheimer. Verder kan DHA
de hoeveelheid van het proteïne beta-amyloid verminderen en daardoor de plaques
vorming in de hersenen. Inmiddels hebben in Amerika 5% van alle mensen van 65
jaar met de ziekte van Alzheimer te maken. Voor 80 jarigen ligt dit percentage
al op 50%.
Wellicht is het westers voedingspatroon van de laatste tientallen jaren hier niet vreemd aan. De verhouding tussen omega-6 en omega-3 vetzuren die onder ideale omstandigheden 1:1 zou moeten zijn bedraagt gemiddeld wel 10-30:1.
Inmiddels
zijn een tweetal clinical trials bezig over DHA en de hersenen bij mensen.
Omega-3
Fatty Acid May Help Prevent Alzheimer's Brain Lesions
A
type of omega-3 fatty acid may slow the growth of two brain lesions that are
hallmarks of Alzheimer's disease, UC Irvine scientists have discovered. The
finding suggests that diets rich in docosahexaenoic acid (DHA) can help prevent
the development of Alzheimer's disease later in life.
This study with genetically modified mice is the first to show that DHA, an
omega-3 fatty acid, can slow the accumulation of tau, a protein that leads to
the development of neurofibrillary tangles. Such tangles are one of two
signature brain lesions of Alzheimer's disease. DHA also was found to reduce
levels of the protein beta amyloid, which can clump in the brain and form
plaques, the other Alzheimer's lesion.
Previous studies have shown that DHA may have therapeutic value for Alzheimer's
patients, but this research is among the first to show that it may delay the
onset of the disease. DHA is found in fish, eggs, organ meats, micro-algae,
fortified foods and food supplements.
"We are greatly excited by these results, which show us that simple changes
in diet can positively alter the way the brain works and lead to protection from
Alzheimer's disease pathology," said Frank LaFerla, professor of
neurobiology and behavior and co-author of the study.
This research appears in The Journal of Neuroscience.
LaFerla and his research team studied the effects of DHA in mice bred to develop
the plaques and tangles associated with Alzheimer's disease. Mice in the control
group were given food that mimics a typical American diet, with the ratio of
omega-6 fatty acids to omega-3 fatty acids being 10:1. Studies indicate that a
proper ratio is important to maintain health, with the ideal being 3:1 to 5:1.
Typical Western diets contain unhealthy ratios ranging from 10:1 to 30:1.
Omega-6 fatty acids are found in corn, peanut and sunflower oils.
Mice in three test groups were given food with a 1:1 ratio of omega-6 fatty
acids to omega-3 fatty acids. One of these groups received supplemental DHA only,
and two groups received DHA plus additional omega-6 fatty acids. After three
months, mice in all of the test groups had lower levels of beta amyloid and tau
than mice in the control group, but at nine months, only mice on the DHA diet
had lower levels of both proteins. These results suggest that DHA works better
on its own than when paired with omega-6 fatty acids.
The scientists also determined the mechanism by which DHA leads to lower levels
of beta amyloid. DHA, they found, leads to lower levels of presenilin, an enzyme
responsible for cutting beta amyloid from its parent, the amyloid precursor
protein. Without presenilin, beta amyloid cannot be generated. When clumped into
plaques, beta amyloid disrupts communication between cells and leads to symptoms
of Alzheimer's disease.
This latest study adds to growing evidence that diet and lifestyle changes may
reduce the risk of developing Alzheimer's disease. LaFerla and his team have
previously shown that short but repeated learning sessions can slow the physical
progression of Alzheimer's in mice, suggesting that the elderly can delay onset
of the disease by keeping their minds active. The team also found that stress
hormones appear to rapidly exacerbate the formation of plaques and tangles,
suggesting that managing stress could slow the progression of Alzheimer's.
"Combined with mental stimulation, exercise, other dietary intakes, and
avoiding stress and smoking, we believe that people can significantly improve
their odds against this disease," said Kim Green, scientist and lead author
on the DHA, learning and stress studies.
Alzheimer's is a progressive neurodegenerative disorder that affects more than
4.5 million adults in the United States. With an aging population, that number
could approach 20 million by 2050. Five percent of people older than 65 have
Alzheimer's, and up to one-half of people are affected by age 80.
###
UCI scientists Hilda Martinez-Coria and Hasan Khashwji, along with Martek
Biosciences Corp. researchers Eileen Hall, Karin Yurko-Mauro and Lorie Ellis
worked on this study.
Martek funded the study, and two clinical trials evaluating DHA are under way.
The first trial, sponsored by Martek and the National Institute on Aging and
conducted by the Alzheimer's Disease Cooperative Study, is examining the effects
of DHA in slowing the progression of cognitive and functional decline in
patients with mild to moderate Alzheimer's disease. The second trial, also
sponsored by Martek, is evaluating the effects of DHA on age-related cognitive
decline in healthy, older adults with mild memory complaints. For more
information, visit http://www.clinicaltrials.gov/.
About the University of California, Irvine: The University of California, Irvine
is a top-ranked university dedicated to research, scholarship and community
service. Founded in 1965, UCI is among the fastest-growing University of
California campuses, with more than 25,000 undergraduate and graduate students
and about 1,800 faculty members. The second-largest employer in dynamic Orange
County, UCI contributes an annual economic impact of $3.7 billion.
(Mei 2007)