Brain needs cholesterol

Cholesterol may be bad for arteries, but it could be vital to the brain.

A study by German and French scientists suggests cholesterol helps build the nerve connections involved in learning and memory.

But the brain cholesterol is not obtained from the blood, where high levels lead to blocked arteries, heart attacks and strokes.

The molecules that carry it are too big to pass through the blood-brain barrier, which protects neurons from toxic substances.

The research shows cholesterol is secreted by the brain's "support" cells, called glial cells, which nourish and look after neurons.

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

The formation of synapses plays an important part in learning and memory. 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 glial ingredient that triggered synapse formation remained a mystery until the research reported in the journal Science.

The European team, led by Dr Frank Pfrieger at the Max-Delbruck-Centre for Molecular Medicine in Berlin, conducted experiments which showed the key glial factor to be cholesterol.

Cholesterol from the glial cells attached to carrier proteins called apoE, which docked on to molecular receptor sites on neurons, the researchers found.

This prompted the nerve cells to sprout synapses.

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

Dr Pfrieger said: "A defective cholesterol metabolism in the brain may ... impair its development and function."

- NZPA