How Diabetes and Alzheimer’s Disease are Connected
A new study provides significant evidence that diabetes and Alzheimer’s disease have a special relationship. Experts at Washington University School of Medicine report that high blood sugar levels associated with diabetes can raise the levels of key protein fragments found in Alzheimer’s disease patients.
Numerous previous studies have suggested the relationship between diabetes and the most common form of dementia. Among them is an International Journal of Alzheimer’s Disease report in which experts noted that traits of type 2 diabetes (e.g., insulin resistance, abnormal use of glucose, metabolic dysregulation) are also seen in the early stages of Alzheimer’s disease separate from type 2 diabetes.
In another, later study, scientists at Albany University showed that excess amounts of insulin reaches the brain and interfere with the natural destruction of amyloid plaques. These plaques are found in individuals with Alzheimer’s disease and are believed to play a significant role in the development of cognitive decline.
New study of diabetes and Alzheimer’s disease
Now a new team has shown that high levels of sugar (glucose) in the blood can lead to a rapid rise in amyloid beta levels. According to the study’s lead author, Shannon Macauley, PhD, the findings of their animal study suggest that “diabetes…can have harmful effects on brain function and exacerbate neurological conditions such as Alzheimer’s disease.”
The study involved provoking a rise in sugar levels in mice that had been bred to develop an Alzheimer’s-like condition. Here’s what the authors observed:
- Introduction of high sugar levels in these animals resulted in a 20 percent increase in the level of amyloid-beta levels
- Older mice who already had some plaques in their brain were infused with sugar and showed a 40 percent rise in amyloid-beta levels
- Elevations in blood sugar levels resulted in an increase in the activity of brain neurons, which in turn stimulated production of the amyloid beta
Elevated sugar levels can cause minute openings on the surface of brain cells (called KATP channels) to close. When this happens, neurons become overly active, resulting in increased production of amyloid beta.
In another experiment, the authors challenged the mice by giving them a drug (diazoxide), which causes sugar levels to rise. They found that the diabetes drug allowed the KATP channels to remain open, a finding that may lead to a new way to treat Alzheimer’s disease.
The new research results support a close connection between Alzheimer’s disease and high glucose levels associated with diabetes and other conditions marked by abnormal glucose metabolism. Could these findings help scientists find a way to better treat or possibly even prevent Alzheimer’s disease?
EurekAlert/Washington University School of Medicine release
Macauley SL et al. Hyperglycemia modulates extracellular amyloid-B concentrations and neuronal activity in vivo. The Journal of Clinical Investigation 2015 May 4