Studies have shown that people with type-2 diabetes, or late-onset, diabetes, are more likely to develop Alzheimer's disease, the most common form of dementia. The mechanism underlying the correlation between diabetes and Alzheimer's is still largely unknown. But researchers agree that type-2 diabetes affects glucose metabolism in the neurons of the brain, and that glucose metabolism, in turn, can affect the transmission of signals between nerve cells.
Alzheimer's Disease
Alzheimer's disease is the most common form of dementia. The disease causes cell death in the hippocampus, the brain's main memory center. In progressed stages of the disease, this leads to serious memory problems and other cognitive disabilities. According to a study published in the December issue of "Neuron," Alzheimer's disease occurs when a protein called "Tau" causes the formation of a resilient layer of plaque at the synapses, or nerve endings, of the neurons of the hippocampus. This plaque formation prevents successful communication between neurons.
Neuron Glucose Metabolism
Glucose is the main energy source for the brain and the central nervous system. During periods of starvation, the brain can use other kinds of fuel, including a by-product of fat metabolism called ketose bodies. When an abnormality occurs in either glucose or ketosis metabolism, cognitive functions suffer. Memory formation is particularly sensitive to abnormalities in glucose metabolism. The neurotransmitter acetylcholine is crucial to the initial formation of memory. Yet, as argued by a research team in a June 2003 issue of "Pharmacopsychiatry," the brain can only produce acetylcholine in the presence of insulin and a product of glucose breakdown, called acetyl CoA.
The Alzheimer-Diabetes Correlation
Diabetics have an abnormality that gives rise to a decreased cell expression of insulin. As insulin is indirectly involved in memory formation, it is not extremely surprising that Alheimer's and diabetes are significantly correlated. A study published in an August 2010 issue of "Neurology" provided concrete evidence of a significant correlation. In the test, 135 people from Japan were monitored for diabetes and Alzheimer's disease over 10 to 15 years. After their deaths, an autopsy was performed. It was found that 72 percent of people with diabetes-2 had plaque formation in the hippocampus, while only 62 percent of participants without symptoms of type-2 diabetes had symptoms of Alzheimer's disease.
Possible Treatments
The correlation between diabetes and Alzheimer's disease gives hope of a cure of Alzheimer's disease. A study published in the November 2010 issue of "PNAS" suggested that metformin, a drug used to treat type 2-diabetes, could perhaps be effective as a treatment of Alzheimer's disease. The research team showed that metformin can prevent Alzheimer-related changes in the protein Tau in the neurons of mice. As Tau is one of the main factors thought to be implicated in Alzheimer's disease, these results offer hope for a future treatment of Alzheimer's.
References
- "Neuron"; Tau Mislocalization to Dendritic Spines Mediates Synaptic Dysfunction Independently of Neurodegeneration; B. R. Hover, et al.; December 2010
- "Pharmacopsychiatry"; Memory function and brain glucose metabolism; S. Hoyer; June 2003
- "Neurology"; Insulin resistance is associated with the pathology of Alzheimer disease. The Hisayama Study; T. Matsuzaki, et al.; August 2010
- Science Daily: Diabetes Drug Could Work Against Alzheimer's, Animal Study Suggests
