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   Researchers uncover new connection between Alzheimer's disease and diabetes   
      
      
   Posted in: Medical Science News | Medical Research News | Medical Condition   
   News   
      
   Published on May 5, 2015 at 5:54 AM   
      
   Researchers have uncovered a unique connection between diabetes and   
   Alzheimer's disease, providing further evidence that a disease that robs   
   people of their memories may be affected by elevated blood sugar, according to   
   scientists at Washington    
   University School of Medicine in St. Louis.   
      
   While many earlier studies have pointed to diabetes as a possible contributor   
   to Alzheimer's, the new study - in mice - shows that elevated glucose in the   
   blood can rapidly increase levels of amyloid beta, a key component of brain   
   plaques in Alzheimer's    
   patients. The buildup of plaques is thought to be an early driver of the   
   complex set of changes that Alzheimer's causes in the brain.   
      
   The research is published May 4 in The Journal of Clinical Investigation.   
      
   "Our results suggest that diabetes, or other conditions that make it hard to   
   control blood sugar levels, can have harmful effects on brain function and   
   exacerbate neurological conditions such as Alzheimer's disease," said lead   
   author Shannon Macauley,    
   PhD, a postdoctoral research scholar. "The link we've discovered could lead us   
   to future treatment targets that reduce these effects."   
      
   People with diabetes can't control the levels of glucose in their blood, which   
   can spike after meals. Instead, many patients rely on insulin or other   
   medications to keep blood sugar levels in check.   
      
   To understand how elevated blood sugar might affect Alzheimer's disease risk,   
   the researchers infused glucose into the bloodstreams of mice bred to develop   
   an Alzheimer's-like condition.   
      
   In young mice without amyloid plaques in their brains, doubling glucose levels   
   in the blood increased amyloid beta levels in the brain by 20 percent.   
      
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   When the scientists repeated the experiment in older mice that already had   
   developed brain plaques, amyloid beta levels rose by 40 percent.   
      
   Looking more closely, the researchers showed that spikes in blood glucose   
   increased the activity of neurons in the brain, which promoted production of   
   amyloid beta. One way the firing of such neurons is influenced is through   
   openings called KATP channels    
   on the surface of brain cells. In the brain, elevated glucose causes these   
   channels to close, which excites the brain cells, making them more likely to   
   fire.   
      
   Normal firing is how a brain cell encodes and transmits information. But   
   excessive firing in particular parts of the brain can increase amyloid beta   
   production, which ultimately can lead to more amyloid plaques and foster the   
   development of Alzheimer's    
   disease.   
      
   To show that KATP channels are responsible for the changes in amyloid beta in   
   the brain when blood sugar is elevated, the scientists gave the mice   
   diazoxide, a glucose-elevating drug commonly used to treat low blood sugar. To   
   bypass the blood-brain    
   barrier, the drug was injected directly into the brain.   
      
   The drug forced the KATP channels to stay open even as glucose levels rose.   
   Production of amyloid beta remained constant, contrary to what the researchers   
   typically observed during a spike in blood sugar, providing evidence that the   
   KATP channels    
   directly link glucose, neuronal activity and amyloid beta levels.   
      
   Macauley and her colleagues in the laboratory of David M. Holtzman, MD, the   
   Andrew B. and Gretchen P. Jones Professor and head of the Department of   
   Neurology, are using diabetes drugs in mice with conditions similar to   
   Alzheimer's to further explore this    
   connection.   
      
   "Given that KATP channels are the way by which the pancreas secretes insulin   
   in response to high blood sugar levels, it is interesting that we see a link   
   between the activity of these channels in the brain and amyloid beta   
   production," Macauley said. "   
   This observation opens up a new avenue of exploration for how Alzheimer's   
   disease develops in the brain as well as offers a new therapeutic target for   
   the treatment of this devastating neurologic disorder."   
      
   The researchers also are investigating how changes caused by increased glucose   
   levels affect the ability of brain regions to network with each other and   
   complete cognitive tasks.   
      
   Source: Washington University School of Medicine   
      
      
      
      
   http://www.news-medical.net/news/20150505/Researchers-uncover-ne   
   -connection-between-Alzheimers-disease-and-diabetes.aspx   
      
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