As if having Diabetes isn’t bad enough, research has shown that in older age, those with the disease have a much higher tendency to develop Alzheimer’s. The reason wasn’t clear, but now research from The City College of New York (CCNY) ties the issue to a genetic link.

More interestingly, the researchers, who report their finding in the June 2012 issue of the journal Genetics, say that the gene that is seen in many people with Alzheimer’s, also appears to affect the insulin pathway.

Lead scientist in the study, Biology Professor Chris Li explained why the link is not such a stretch:

“People with type 2 diabetes have an increased risk of dementia. The insulin pathways are involved in many metabolic processes, including helping to keep the nervous system healthy.”

While the root causes of Alzheimer’s remain clouded, post mortems of patients who suffered from the disease have shown sticky plaques made from amyloid protein, collecting in the patients’ brains.

Where Alzheimer’s runs in families, it appears there is a mutation in the gene that is the precursor to the amyloid protein (APP). They took the work one stage further and looked at a protein APL-1, made by a gene in a worm, Caenorhabditis elegans (C. elegans ). It replicates the amyloid protein in humans perfectly.

Professor Li explains that they found the similar metabolic disruptions in the worms, where mutations had changed the APP gene:

“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 … 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 APL-1 protein is important to the worms and mammals alike, so when they took away that gene, the worms died. Li hopes that his work will provide new insight into the causes of both diabetes and Alzheimer’s. Dr. Mark Johnston, editor-in-chief of Genetics was impressed with the work and commented:

“This is an important discovery, especially as it comes on the heels of the U.S. government’s new commitment to treat and prevent Alzheimer’s disease by 2025 … We know there’s a link between Alzheimer’s and diabetes, but until now, it was somewhat of a mystery. This finding could open new doors for treating and preventing both diseases.”

Li concludes that big questions still remain as to exactly how the APP is linked with the insulin pathway, but nonetheless, the work opens a doorway to new drugs to target both diabetes and Alzheimer’s in the future.

Written by Rupert Shepherd