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Alzheimer's gene linked to diabetes

18 June 2012
Appeared in BioNews 661

A gene known to be found in many Alzheimer's disease patients has been linked to the way insulin is processed in the body. The finding could prove there is a link between Alzheimer's disease and type 2 diabetes, explaining why people with diabetes face a higher risk of developing Alzheimer's.

'We know there's a link between Alzheimer's and diabetes, but until now, it was somewhat of a mystery', said Professor Mark Johnston, editor-in-chief of Genetics, the journal in which the study was published. 'This finding could open new doors for treating and preventing both diseases'.

People with type 2 diabetes have an almost two-fold higher risk of developing Alzheimer's disease compared to those without diabetes, although the link between the two diseases has remained elusive until now.

'The insulin pathways are involved in many metabolic processes, including helping to keep the nervous system healthy', said Professor Chris Li of the City College of New York, who led the study.

Professor Li and her team studied the ALP-1 gene in the nematode worm, which is similar to the APP gene in humans known to be involved in Alzheimer's disease. When all copies of ALP-1 were removed from the worms' DNA, the animals died. However, when the gene contained mutations that made the gene less effective, the worms' metabolism was affected.

'What we found was that mutations in the worm-equivalent of the APP gene slowed their development, which suggested that some metabolic pathway was disrupted', said Professor Li. 'We began to examine how the worm-equivalent of APP modulated different metabolic pathways and found that the APP equivalent inhibited the insulin pathway'.

The idea of a link was strengthened by the finding that additional mutations in genes involved in the insulin pathway could reverse the effect of a mutated ALP-1 gene. It now seems that the ALP-1 gene might be involved in both Alzheimer's disease and type 2 diabetes.

'This early-stage study may provide an interesting clue to help scientists unravel how diabetes and Alzheimer's are linked', said Dr Marie Janson, director of development at Alzheimer's Research UK, which has itself funded studies looking at the link between diabetes and Alzheimer's.

'As this research looked at the effects of a gene in worms, studies are now needed to discover whether the equivalent gene in people has the same effect, and exactly what mechanisms may be involved', she added.

There is currently no cure for Alzheimer's. The disease is the most common cause for dementia, which affects around 800,000 people in the UK.

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