Neuroimaging shows dramatic brain cell loss in
Alzheimer's
Brain cells disappear quickly and steadily in patients with
Alzheimer's disease, an international team of researchers reported
on Thursday. Neuroimaging studies (MRI) indicated a 5% annual loss
of brain cells in Alzheimer's patients, and what more alarming, up
to 10% in the frotal lobe, the key memory areas. In contrast,
healthy volunteers monitored in the study lost less than 1% of their
brain cells a year. Neurologists at UCLA, in Britain and in
Australia scanned the brains of 12 Alzheimer's patients and 14
healthy volunteers very three months.
Now the doctors could, for the first time ever, see Alzheimer's
disease progressing in living patients. MRI gives a finer image of
bodily structures than x-rays. The rearchers were stunned to see a
spreading wave of tissue loss. Initially confined to memory areas,
this loss moved across the brain like a lava flow, destroying more
and more tissue as the disease progressed, the investigators decribe
writing in the Journal of Neuroscience.
 Memory systems go
first and then the frontal areas involved in inhibition and
self-control and later areas involved in emotion. Another feature is
that some parts of the brain are completely spared. One example is
the visual area. Why it is, is a mystery, theu autors say.
The researchers said their findings would help doctors check to
see if treatments are helping, and perhaps help chart the course of
the disease. Alzheimer's is assessed using standard tests of a
patient's behavior and performance, rather than any physical
evidence. This will probably continue to be the case.
"The diagnosis of Alzheimer's disease really depends upon
demonstration of cognitive dysfunction," Gilman said in an
interview with Reuters Health.
Reference: Thompson P,
Hayashi K, de Zubicaray G, et al. Dynamics of gray matter loss in
Alzheimer´s. Journal of Neuroscience. 2003 February
Carnosine Therapy in Alzheimer's Disease
The main reason for brain cell destruction is probably the
inhibition of the proteasome, a protein which removes damaged and
denaturated proteins from the brain cells. The causes of proteasome
inhibition are explained in a separate
review.
Carnosine
protects the proteasome and hence fights Alzheimer´s disease.
Carnosine is a dipeptide, also called a neuropeptide and
neurotransmitter. Patients with Alzheimer´s disease develop
extracellular deposits of amyloid protein and microscopic tangles of
fibrils inside nerve cells. In experiments, treatment with carnosine
was found to reduce or completely prevent cell damage caused by
ß-amyloid. Carnosine blocks and inactivates ß-amyloid, so it
protects neural tissues against dementia.
Moreover, carnosine protects the brain cells by fighting the
highly toxic alpha, beta-unsaturated aldehyde acrolein which is
formed during the peroxidation of polyunsaturated lipids, raising
the possibility that it functions as a 'toxicological second
messenger' during oxidative cell injury.
Recent research also confirms that the toxic unsaturated aldehyde
crotonaldehyde (CA) contributes to carbonylation
resulting in protein damage during lipid peroxidation. As carnosine
combats all aldehydes, it offers another explanation for its
benefits in prevention of Alzheimer´s disease and other conditions
with oxidative stress. Moreover, Carnosine protects proteasomes,
protein molecules which detoxify the brain cells, and Carnosine
removes toxic heavy metals from the brain cells in a biochemical
process called chelation.
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