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First study shows how diabetes could lead to Alzheimer's disease

Kathleen Blanchard's picture
Finding could explain link between diabetes and Alzheimer's disease

For the first time, researchers have discovered how diabetes could promote Alzheimer’s disease. The finding is important because understanding the link means early interventions for people living with diabetes could help with prevention.

Diabetes and Alzheimer’s disease are both increasing at alarming rates, especially among older people.

Scientists say they’ve now understand diabetes leads to increased accumulation of two hallmarks of Alzheimer’s disease in the brain - amyloid beta (Abeta) and tau protein, found in a study of mice with type 1 diabetes.

Pamela Maher, a senior staff scientist in Salk's Laboratory of Cellular Neurobiology writes in a press release, "We show that type 1 diabetes increases vascular-associated amyloid beta buildup in the brain and causes accelerated brain aging."

The researchers aren’t exactly sure why the brain accumulates Abeta that is a protein that leads to the formation of beta amyloid plaque from inflammation in the brain cells.

Abeta accumulates inside star-shaped brain cells called astrocytes. When astrocytes interact with Abeta, pro inflammatory molecules are released that destroys neurons. The finding had not previously been shown in type 1 diabetic mice.

The scientists also not there are other inflammatory processes that occur in addition to protein binding to sugars – a process known as non-enzymatic glycation.

Lead study author Antonio Currais, a postdoctoral researcher at Salk explains in a media release, "Both chronic peripheral inflammation and increased non-enzymatic glycation are associated with diabetes, and these changes may act on the brain to alter astrocyte function, which eventually leads to Alzheimer's-like changes."

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He adds that astrocytes play a key role for maintaining brain nerve cells (neurons) because they facilitate the transfer of nutrients between blood vessels and cells.

Abeta is normally removed from the brain by degrading enzymes that become deficient with aging, in the presence of diabetes and from genetic factors; found from past studies.

"Our study supports and extends the links between diabetes, aging and Alzheimer's," says Maher.

How the study was done

The Salk Institute researchers induced type 2 diabetes in two sets of mouse models. One set of mice age prematurely and are prone to Alzheimer’s like brain changes. The second set of mice is from the same gene pool, but age normally.

The scientists observed how type 1 diabetes interacts with age to lead to Alzheimer’s disease. They found that diabetes affected both older and diabetic mice in a variety of ways that are made worse with by premature aging.

The study is unique because it’s the first to show diabetes raises levels of proteins in the brain that are associated with Alzheimer’s disease, explaining how the disease might affect the brain. The finding is important because it could lead to new treatments that treat diabetes and dementia. The new study also builds on previous research about the link between diabetes and early onset of dementia.

Salk Institute for Biological Studies

Image: Courtesy of the Salk Institute for Biological Studies