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Thursday, 8 November, 2001, 19:03 GMT
Vital ingredient for a healthy memory
Brain
Cholesterol is secreted by cells in the brain
Cholesterol plays a crucial role in making sure that the brain works properly.

The compound is notorious for clogging up the arteries, leading to heart disease and stroke.

But scientists have found that it stimulates the nerve cells of the brain to make the connections that are essential to learning and memory.


A defective cholesterol metabolism in the brain may impair its development and function

Dr Frank Pfrieger
The brain does not obtain cholesterol from the blood.

The molecules are too big to pass across the blood-brain barrier which provides a frontline defence against toxic substances.

New research by French and German scientists suggests that instead cholesterol is secreted by support cells within the brain.

These glial cells play a vital role in helping to nourish the nerve cells or neurons.

Previous work had suggested that glial cells were involved in the growth of synapses - the tendril-like branches which connect different nerve cells.

The formation of synapses plays an important part in learning and memory.

Survived

Brain cell
Cholesterol appears to help brain cells make new connections
Isolated neurons in the laboratory survived and grew, but showed only a few of the electrical signals generated by synapses.

But when exposed to substances secreted by glial cells they produced strong signs of synaptic activity.

The identity of the glial ingredient which triggered synapse formation has remained a mystery until now.

But research published in the journal Science suggests that cholesterol is the magic ingredient.

The work has been carried out by a team led by Dr Frank Pfrieger, at the Max-Delbruck-Center for Molecular Medicine in Berlin.

They have uncovered the process by which cholesterol from the glial cells docks on to receptor sites on the neurons.

They showed in laboratory experiments that this docking process prompted the nerve cells to sprout synapses.

The scientists speculate that genetic or age-related problems in the cholesterol mechanism might play a role in neurodegenerative diseases such as Alzheimer's.

Dr Pfrieger said: "Cholesterol is necessary in large quantity if nerve cells are to make connections with each other.

"A defective cholesterol metabolism in the brain may impair its development and function."

Dr Pfrieger said the exact way that cholesterol stimulated synapse formation was unclear.

It could be that the compound acted as a signal, or it could simply be a key ingredient in the complex structure of the synapse itself.

See also:

03 Aug 01 | Health
Cholesterol warning for elderly
22 Jun 01 | Health
Cracking the cholesterol problem
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