Neuropeptides
It has long been
known that type 1 diabetes is caused by the destruction of
insulin producing cells in the pancreas by the body’s own
immune system. This is not so much due to antibodies but a type
of white blood cell called CD8+ lymphocytes. They are very
important in protecting the body from infections but at times
they can attack the body’s own tissues.
Scientists have
studied type 1 diabetes in a strain of mice known as NOD. This
stands for non-obese diabetic. This is a specially bred strain
that has a tendency to develop inflammation of the pancreas and
type 1 diabetes. It occurs spontaneously in about 60-80% of
females and 20-30-% of males. Researchers at the Hospital for
Sick Children in Toronto, Canada found that injecting a
chemical called substance P into the artery to the pancreas
stopped and reversed the process for weeks. In addition it
reversed the resistance to insulin that is found in these
diabetic mice.
Substance P is
called a neuropeptide or a neurotransmitter. This means that it
is involved with the transmission of impulses between nerves.
It has a number of functions but usually it especially
important in the sensation of pain.
The importance of
this finding is that it suggests that the cause of the
destruction of insulin producing cells is not simply the immune
system but nerves appear to be involved too. If injecting
substance P or a similar substance into the pancreas could stop
or even reverse the destruction of insulin producing cells in
type 1 diabetes, this would be a great advance.
There is already
evidence that neuropeptides play a part in the production of
diabetic neuropathy. This is damage to nerves caused by
diabetes. This is the first time that neuropeptides have been
implicated in the underlying process of destruction of insulin
producing cells that causes diabetes.
Although this
research was published late in 2006 it is important to realise
that it does not mean that the end of type 1 diabetes is in
sight. The findings relate to inbred experimental mice and may
not be applicable to humans.
In the human, the
islets of Langerhans that contain the cells that produce
glucagon and insulin, are richly supplied by autonomic nerves.
These are the nerves of the sympathetic and parasympathetic
nervous system and they stimulate polypeptide secretion from
the nerves in the pancreas. The parasympathetic nerves and
administration of their transmitting chemicals stimulate
insulin and glucagon secretion. The sympathetic nerves and
administration of their transmitters inhibit insulin but
stimulate glucagon secretion.
Dr Tony Woolfson MB
BS DM MRCP(UK)
Learn how to master your diabetes. Visit my website at
www.diabetesdietdoctor.com.
|