Most of us know that our pancreas produces insulin but researchers
have recently learned that our brains also produce insulin. They
have also discovered that this brain insulin and its growth factors
are necessary for the survival of brain cells. It appears that a
deficiency of this newly appreciated brain insulin may actually
contribute to the progression of Alzheimer's Disease.
While it has been previously discovered that insulin resistance,
a characteristic of diabetes, is associated with neurodegeneration,
one study demonstrated strong evidence of the link between diabetes
and Alzheimer's disease.
Additionally, through studying a genetic abnormality in rats that
blocks insulin signals in the brain, scientists found insulin and
IGF (insulin-like growth factor) I and II were expressed in neurons
positioned in several locations in the brain. Researchers concluded
that a decrease in insulin signaling in the brain contributes to
the degeneration of brain cells--an early sign of Alzheimer's disease.
These irregularities, however, do not relate to type 1 or type 2
diabetes, but serve as indicators of a different, more complex,
disease process that stems from the central nervous system.
Postmortem Research
By looking at postmortem (collected after death) brain tissue in
Alzheimer's patients, researchers discovered that growth factors
were not produced at normal levels in the part of the brain responsible
for memory--known as the hippocampus--causing cells in other parts
of the brain to die.
Insulin and IGF I were greatly reduced in all the areas of the
brain affected by the progression of Alzheimer's. Such areas include
the frontal cortex, hippocampus and hypothalamus. While scientists
have suspected a link between diabetes and Alzheimer's disease,
this is the first study to provide evidence of that connection.
Journal
of Alzheimer's Disease February 2005; 7(1): 45-61
Medical
News Today March 7, 2005
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