- Scientists say they may have discovered a previously
unknown form of diabetes, after finding the brain produces insulin as well
as the pancreas.
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- Unlike other types of diabetes, the form - dubbed type
3 by the US Brown Medical School team - is not thought to affect blood
sugar.
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- Type 3 affects brain insulin levels, and appears to be
linked with Alzheimer's disease.
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- The team's research appears in the Journal of Alzheimer's
Disease.
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- Type 1 and type 2 diabetes occur when the body is unable
to produce or use insulin from the pancreas.
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- The so-called 'type 3' diabetes refers to lower than
normal levels of newly discovered brain insulin, which appears to be
associated
with Alzheimer's disease in some way.
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- Scientists have known for some time that people with
diabetes have an increased risk of Alzheimer's disease - by up to
65%.
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- They have also discovered that many type 2 diabetics
have deposits of a protein in their pancreas which is similar to the
protein
deposits found in the brain tissue of people with Alzheimer's
disease.
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- Research has been going on to find out what links the
two conditions.
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- Dr Suzanne de la Monte and colleagues now believe it
is down to what they are calling type 3 diabetes.
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- By looking at rodents and post-mortem brain tissue from
people with Alzheimer's disease they have found that insulin and its
related
proteins are actually produced in the brain, and that reduced levels of
both are linked to Alzheimer's disease.
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- 'Brain' insulin
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- They say this insulin and its related growth factors
and receptors in the brain are vital for the survival of brain
cells.
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- If they are not produced at normal levels, the cells
die.
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- In the case of Alzheimer's, the cells that die are
located
in the part of the brain involved with memory, called the
hippocampus.
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- Dr de la Monte, who is a neuropathologist at Rhode Island
Hospital, said: "What we found is that insulin is not just produced
in the pancreas, but also in the brain.
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- "These abnormalities do not correspond to type 1
or type 2 diabetes, but reflect a different and more complex disease
process
that originates in the central nervous system."
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- Not only does this opens the way for targeted treatment
to the brain and changes the way we view Alzheimer's disease, "it
raises the possibility of a type 3 diabetes", she said.
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- "The implication is that treating type 1 or type
2 diabetes may have no impact on Alzheimer's disease. We believe that
therapeutic
agents need to be designed that specifically influence the actions of
insulin
in the brain," she said.
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- Cathy Moulton, care advisor at Diabetes UK, said:
"So
far studies on a potential link between Alzheimer's and diabetes have come
up with inconclusive results.
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- 'More research'
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- "There is some evidence to suggest that poorly
controlled
diabetes also affects the functioning of the brain.
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- "However, far more research on a link between
Alzheimer's
and diabetes is needed before we can draw any firm
conclusions."
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- A spokeswoman from the Alzheimer's Research Trust said:
"Researchers have believed for some time that the role of insulin
and its growth factors are very important in Alzheimer's disease.
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- "Scientists have suggested that the link could be
down to molecular changes affected by insulin.
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- "Work funded by the Alzheimer's Research Trust is
currently investigating the way insulin acts on the brain and should
improve
our understanding of Alzheimer's and hopefully lead to way to new
treatments.
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- Professor Greg Cole, from the University of California
Los Angeles' Alzheimer's Disease Research Center, said: "This is a
new finding. It is interesting that the brain makes very low levels of
insulin.
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- "But its significance is unclear. The levels are
so low that they have not been detected with less sensitive methods. I
don't think we can say they are high enough to matter.
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- "I suspect that the brain insulin itself is not
very significant and neither is its deficit in Alzheimer's disease and,
therefore, I wouldn't call it type 3 diabetes."
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- But he said there was evidence that diabetes and
Alzheimer's
are linked in some way.
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- © BBC MMV
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- http://news.bbc.co.uk/2/hi/health/4315609.stm
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