Study links brain tangles and diabetes independently of Alzheimer's

According to a new study published in the journal Neurology, diabetes may be linked to the buildup of "tangles" in the brain, separate from Alzheimer's disease.

Beta-amyloid are plaques in the brain that are a principal feature of Alzheimer's disease.

The study was based on data from the USA Alzheimer's Disease Neuroimaging Initiative. It looked at the relationship between type 2 diabetes and the loss of brain cells and their connections, the levels of beta-amyloid and tangles of protein in the spinal fluid of the participants.

Beta-amyloid are plaques on the brain that are a principal feature of Alzheimer's disease, while tangles are the abnormal twisting of the cellular filaments that hold the neuron in its proper shape. These tangles are caused by an aberrant form of a protein known as tau.

The researchers within neurosciences at Monash University in Melbourne, Australia, say that "evidence shows that people with type 2 diabetes have double the risk of developing dementia."

The study aimed to understand how diseases like diabetes may directly or indirectly affect brain cell death. It involved 816 people of an average age of 74.

Of those included in the study, 397 had mild cognitive impairment (MCI), 191 had Alzheimer's disease, 228 had no memory and thinking problems and 124 had diabetes.

"Studies such as this one seek to understand how diseases like diabetes may directly or indirectly affect brain cell death. Due to the fact that nerve cells in the brain do not replace themselves, it is extremely important to find ways to reduce the death of current brain cells."

The buildup of tangles may contribute to loss of brain tissue

The study finds that greater levels of tau in spinal fluid may reflect a greater build-up of these tangles.

On average, those in the study with diabetes had 16 picograms per milliliter greater levels of the tau protein in the spinal and brain fluid regardless of whether they had been diagnosed with dementia. It is these tangles, according to the researchers, that may eventually contribute to the development of dementia.

The study also found that a reduced thickness of the cortex - the layer of the brain with most nerve cells - was also associated with diabetes. 

Regardless of the presence of thinking and memory problems, MCI or dementia as a result of Alzheimer's, people with diabetes had cortical tissue that was an average of 0.03 millimeters less than those who did not have the condition.

In conclusion, a cause-and-effect relationship between diabetes and brain tangles is not determined as the study looked at participants' data at only one point in time.

References:

1.  Type 2 diabetes mellitus and biomarkers of neurodegeneration, Velandai Srikanth, PhD et al., Neurology, doi: 10.1212/WNL.0000000000001982, published online 2 September 2015, abstract.
2.  American Academy of Neurology news release, accessed 2 September 2015 via Newswise.
3.  Additional source: Alzheimer's Association, More about plaques, accessed 2 September 2015.