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Much has been in the media lately on new developments in Alzheimer’s
disease research. Here is a brief update of what has been hot in 2000,
and what to look for in 2001.
There are four known genes associated with Alzheimer’s. Three of these
cause early-onset cases, affecting those between 40 and 60 years old.
The fourth increases the risk in later-onset, or after age 70, cases and
decreases the age at which these individuals might otherwise be at risk.
Most cases still appear to be sporadic or non-familial, meaning no
known gene is involved. Research on high-incidence families with none of
the known genes suggests that at least four more Alzheimer’s disease
genes are yet to be discovered. Three different research teams recently
announced that they believe there is a fifth Alzheimer’s gene. With the
recent sequencing of the human genome, we will probably see more
breakthroughs in this area soon.
The leading theory for the cause of Alzheimer’s disease is that an
abnormal protein begins to accumulate in the brain and interferes with
neuron functioning, eventually killing the neuron. This accumulation is
thought to occur for several decades before the disease is diagnosed.
It is believed that any number of abnormal events can lead to the
formation or accumulation of the abnormal protein, or amyloid. A number
of discoveries are defining what these events might be, and pieces of
evidence are converging on a unified theory.
For example, one of the enzymes that may help block the formation of
the abnormal proteins was discovered last year. There is now a race on
to see if therapies can be developed to block these enzymes.
Another line of research is examining why one version of amyloid is
pathological and other versions of amyloid are not. A hypothesis about
aging in general is that metabolism releases chemical forms of oxygen
and hydrogen-oxygen that bind to cell membranes and eventually kill the
cell. These free radicals can be mopped up before they attack the
membrane by antioxidant vitamins, such as Vitamins A, C, and E. Some
Alzheimer-related proteins may cause large quantities of free radicals.
Work is under way to see if blocking this whole process could prevent
Alzheimer’s. Adequate intake of Vitamins A, C, and E is thought to help
prevent other diseases, including heart disease. If you are thinking of
taking more vitamin pills, do not overdo it, because too much of these
vitamins may be harmful.
If Alzheimer’s disease is forming in the brain several decades before a
diagnosis is made, we need to find it earlier to have the best chance of
preventing it or blocking it. Recent brain imaging studies suggest that
those with Alzheimer’s genes process information differently than those
without a gene well before symptoms appear. A compound has been
developed that binds to the abnormal amyloid and can be seen on a brain
scan. This opens up the possibility of early diagnosis and of using the
compound to attack the amyloid and destroy it. Clinical trials are now
under way to see if a vaccine can prevent or reduce amyloid formation in
humans; it has shown success in laboratory tests on rats.
The amyloid deposits in the Alzheimer’s brain are held together in part
by copper and zinc bonds. We all need small quantities of copper and
zinc to live, so we do not want to completely remove these metals from
our bodies. But if we could break the bonds in the amyloid deposits, we
might be able to fight the disease. An old antibiotic called clioquinol
seems to be able to do exactly this. Mice that are given clioquinol seem
to lose the amyloid deposits. Clioquinol has been approved by the FDA as
an antibiotic, but was removed from the market because of side effects
involving the loss of Vitamin B-12. A clinical trial is under way to see
if clioquinol, perhaps supplemented with B-12, can be helpful in humans
with Alzheimer’s.
The active treatments for Alzheimer’s that are approved by the FDA now
include a new drug, Exelon. Three approved drugs, Cognex, Aricept and
Exelon, work by increasing the supply of a neurotransmitter used by many
of the neurons damaged by the disease. These drugs do not stop the
disease and are generally not beneficial in later stages, but in many
individuals in the early to middle stages, they provide some relief of
symptoms — delaying symptom progression by 6 months or so. These drugs
often carry unpleasant gastrointestinal side effects (the active
ingredient is similar to that of many pesticides). Aricept and Exelon
appear to have fewer of these side effects. More drugs are in advanced
clinical trials and will likely be approved by the FDA in the near
future, so physicians will have much more in their arsenal for treating
symptoms.
Clearly, four known genes either lead to the disease or increase the
risk of it, yet most cases
involve those with no known family history of Alzheimer’s. Although 15
percent of all cases occur under age 65, age itself is a major risk
factor, with the risk increasing from 10 percent over age 65 to 50
percent over age 85.
There are twice as many women as men with Alzheimer’s, mostly because
men tend to die younger. Estrogen does not help those with Alzheimer’s,
but it may help prevent it in post-menopausal women.
Another fascinating risk factor is gaining increased attention:
childhood intelligence. A University of Kentucky study has shown that
elderly nuns who had more fluent writing ability as young adults are
less likely to develop Alzheimer’s than those with poorer writing
ability. Recently, a study in Scotland showed that 11-year-olds who
scored high on an intelligence test in 1932 were less likely to develop
Alzheimer’s in their old age compared to those who scored lower.
Together with a study from China showing that more education reduces
the risk of being
diagnosed with Alzheimer’s, these findings suggest that the more
enriched our educational and intellectual lives, the less chance of
developing Alzheimer’s.
Announcements of new developments in Alzheimer’s research and news
stories about public figures with the disease increase awareness of just
how common Alzheimer’s is and how much it impacts the family. Early
diagnosis is important in helping families plan and in improving quality
of life for the patient and the care giver.
The Alzheimer’s Association, which can help with issues families face,
has offices across Colorado. It can be reached at www.alz.org. or
1-800-864-4404.
For more information, contact your local
Colorado State University Extension office.
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Uploaded Tuesday, November 27, 2007
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