Alzheimer's risk: Scientists yesterday said they had identified a molecule that could be targeted to treat mental impairment in patients with Down syndrome.
Researchers from the Institute of Psychiatry at King's College, London, found that people with Down syndrome had higher levels of myo-inositol in their brains compared with people without the condition.
Writing in Archives of General Psychiatry, the team said that increased levels of this molecule were linked to reduced intellectual ability.
The researchers, led by Prof Declan Murphy, used a special type of scan to measure the concentrations of myo-inositol in the brains of 38 adults with Down and compare them with 42 healthy controls.
It is suspected that high levels of myo-inositol could play a part in predisposing people with Down syndrome to early-onset Alzheimer's disease, which can cause severe dementia. This is because the molecule is known to promote the formation of amyloid plaques, which are a key hallmark of Alzheimer's.
The researchers said that once they reached the age of 40, almost all those with Down showed symptoms of Alzheimer's. The combination of already existing mental retardation with increasing levels of dementia is hard to treat and expensive to manage.
Down syndrome is the most common genetic cause of mental retardation. It occurs when a child is born with three copies of chromosome 21 rather than just two, as is normal. One of the genes of chromosome 21 encodes a transporter that pumps the molecule myo-inositol into the brain.
The researchers said the increased levels of the molecule in the brains of people with Down could be explained by the fact that these people have an extra copy of the gene that makes this pump.
Prof Murphy said: "We have shown in this study that adults with Down syndrome have a significantly higher concentration of myo-inositol in the hippocampal region of their brains, and this increase is associated with a reduced cognitive ability.
"We are now carrying out more studies to see if we can reduce the concentration of myo-inositol in the brains of people with Down.
"We hope that if we can do this, it will be a new way of treating this devastating disorder."