Alzheimer’s disease and type 2 diabetes are so closely related that drugs currently used to control glucose levels in diabetes may also alleviate the symptoms and progression of Alzheimer’s disease, according to new research from the University of Aberdeen.
This is also the first study of its kind to show that Alzheimer’s disease can lead to diabetes, as opposed to diabetes occurring first. This is contrary to what was previously thought - that diabetes begins with a malfunction in the pancreas or a high fat, high sugar diet.
The research was led by Professor Bettina Platt, who formed a unique collaboration between her Alzheimer’s research team and the diabetes research team led by Professor Mirela Delibegovic. The teams wanted to study why the two diseases are so commonly found together in elderly patients.
The researchers developed a model of Alzheimer’s disease and were surprised to find that increased levels of a gene involved in the production of toxic proteins in the brain not only led to Alzheimer’s-like symptoms, but also to the development of diabetic complications.
Professor Platt said of her research:
“Many people are unaware of the relationship between diabetes and Alzheimer’s disease, but the fact is that around 80% of people with Alzheimer’s disease also have some form of diabetes or disturbed glucose metabolism. This is hugely relevant as Alzheimer’s is in the vast majority of cases not inherited, and lifestyle factors and comorbidities must therefore be to blame.
“Our research teams are particularly interested in the impact of lifestyle related factors in dementia and by collaborating with experts in diabetes and metabolism, we have been able to investigate the nature of the link in great detail.“
The theory that Alzheimer’s is actually type III diabetes was first proposed in 2005 when a small study found that levels of both insulin and insulin-like growth factors in deceased Alzheimer’s patients brains were significantly lower than those in the brains of people who had died of other causes. The researchers conclusion was that insulin and insulin-like growth factor are produced not only in the pancreas but also in the brain.
“Until now, we always assumed that obese people get type 2 diabetes and then are more likely to get dementia - we now show that actually it also works the other way around,” Platt said.
“Additionally, it was previously believed that diabetes starts in the periphery, i.e. the pancreas and liver, often due to consumption of an unhealthy diet, but here we show that dysregulation in the brain can equally lead to development of very severe diabetes - so again showing that diabetes doesn’t necessarily have to start with your body getting fat - it can start with changes in the brain.
This study provides a new therapeutic angle into Alzheimer’s disease and we now think that some of the compounds that are used for obesity and diabetic deregulation might potentially be beneficial for Alzheimer’s patients as well. The good news is that there are a number of new drugs available right now which we are testing to see if they would reverse both Alzheimer’s and diabetes symptoms.
We will also be able to study whether new treatments developed for Alzheimer’s can improve both, the diabetic and cognitive symptoms.“
Kaja Plucińska, Ruta Dekeryte, David Koss, Kirsty Shearer, Nimesh Mody, Phillip D. Whitfield, Mary K. Doherty, Marco Mingarelli, Andy Welch, Gernot Riedel, Mirela Delibegovic, Bettina Platt Neuronal human BACE1 knockin induces systemic diabetes in mice Diabetologia July 2016, Volume 59, Issue 7, pp 1513–1523
Image: US National Institute on Aging, Alzheimer’s Disease Education and Referral Center. PET scan of the brain of a person with AD showing a loss of function in the temporal lobe