Diabetes and Sugar May Be Linked to Alzheimer’s, Experts Explain Why

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People living with Type 2 diabetes are known to be at greater risk of developing Alzheimer’s disease, but the reasons behind this association were unclear.

New research from Wake Forest University School of Medicine in North Carolina reveals that increased sugar consumption and elevated blood glucose levels alone can trigger the growth of toxic proteins in the brain, a key indicator of the disease.

These toxic proteins, called amyloid plaques, build up in the brains of people with the degenerative condition. According to the U.S. Centers for Disease Control and Prevention (CDC), more than 1 in 10 Americans are diagnosed with diabetes, and a significant portion may eventually develop Alzheimer's. Given the potential impact on the number of individuals who may subsequently develop Alzheimer's, the new research underscores the importance of managing diabetes and addressing factors such as sugar intake and blood glucose levels.

Published in May in JCI Insight, this study provides new insights into the metabolic changes associated with diabetes that heighten the risk of Alzheimer's.

Sugar Helps Toxic Proteins Form in the Brain

Using mice, Wake Forest researchers found that consuming sugar water instead of regular drinking water led to the formation of more amyloid plaques in the brain.

To understand what drives this phenomenon, the researchers identified metabolic sensors called adenosine triphosphate (ATP)-sensitive potassium channels (KATP channels) that play a role in this process.

By removing these sensors from the brains of test mice, researchers discovered that the increase in blood sugar no longer raised amyloid protein levels or led to plaque formation.

They also examined the expression of these metabolic sensors in the brains of people with Alzheimer's disease and observed similar changes associated with the disease.

These findings suggest that these sensors may have a role in the progression of Alzheimer's and could potentially be targeted for future treatments.

This work is noteworthy because it identifies a potential drug target that links diabetes and Alzheimer’s disease, Percy Griffin, who has a doctorate in molecular cell biology and is the director of scientific engagement for the Alzheimer's Association, told The Epoch Times. The study also adds to people's understanding of exactly how known risk factors operate to raise or lower Alzheimer’s risk.

“However, mice are not people, and they don’t actually get Alzheimer’s disease,” Griffin added. “So while this study provides some intriguing hints, the findings need to be confirmed and then replicated in humans to see if they are worth pursuing further."

Earlier Onset Diabetes Increases Your Risk for Alzheimer's

In a 2021 study of 10,095 people from 1985 to 2019, researchers documented 1,710 cases of diabetes and 639 cases of dementia. They observed that for every 1,000 participants examined every year who did not have diabetes by age 70, only about nine developed dementia.

However, for participants diagnosed with diabetes, the rates of dementia per 1,000 were 10 for people diagnosed up to five years earlier, 13 for six to 10 years earlier, and over 18 for a diabetes onset of over 10 years earlier. These findings suggest that an earlier diagnosis of diabetes is linked to an increased risk of significant cognitive decline. This association is likely attributed to prolonged exposure to elevated blood sugar levels, heightened damage to blood vessels resulting in reduced oxygen supply to the brain, and potential impact on brain cells due to insulin resistance.

The study authors emphasized that cardiovascular damage due to diabetes was unlikely to account for what they observed. They hypothesized that brain metabolic dysfunction is the primary driver of Alzheimer's disease, "highlighting the role of decreased transport of insulin through the blood-brain barrier, impairments in insulin signaling, and consequently decreased cerebral glucose utilization," the study authors wrote.

About two of every three Americans are considered overweight or obese, and one out of three is obese. Obesity is a significant risk factor for Type 2 diabetes and cognitive decline.

Dr. Jonathan J. Rasouli, director of complex and adult spinal deformity surgery at Northwell Staten Island University Hospital, emphasizes the importance of diet in preventing cognitive decline.

“Scientists have long suspected a link between sugar intake, insulin resistance, and eventual development of neurodegenerative disorders such as Alzheimer's disease,” he said.

In Type 2 diabetes, insulin resistance is the underlying issue with sugar metabolism. When patients become insulin resistant, their bodies no longer effectively absorb dietary sugar from the bloodstream into healthy tissues. “As a result, sugar molecules hang around in the blood and do not get broken down for energy,” Rasouli added. “These molecules can ultimately damage the body if they stay around for too long.”

In the brain, high blood sugar (hyperglycemia) is associated with strokes and dementia.

Rasouli further noted that sugar can alter how our natural gut bacteria digest food, leading to neurocognitive decline due to the accumulation of toxins.

Clinical Trial Investigates Insulin Nasal Spray to Improve Cognition

There is evidence the brain is affected by insulin, and the direct introduction of insulin to the brain has shown potential benefits for cognition. The strong connection between insulin resistance commonly seen in diabetes and cognitive health has led some scientists to refer to Alzheimer's as "type 3 diabetes."

Previous research has explored treatments based on this connection, with promising results. A systematic review of studies found that Alzheimer's patients with genetic risk factors who received insulin through nasal spray showed improved verbal memory.

In a placebo-controlled pilot study, 24 individuals with amnestic memory impairment, or mild Alzheimer's disease, showed improved verbal memory retention and attention after a three-week daily dose of intranasal insulin compared to a placebo.

Wakefield Forest University is conducting a clinical trial until 2028 to investigate the safety and effectiveness of nasal spray insulin and empagliflozin, an FDA-approved drug used for Type 2 diabetes, in improving cognition and reducing amyloid proteins associated with Alzheimer's disease.

During the trial, participants will be randomized into one of four daily treatment protocols for four weeks: intranasal insulin, an empagliflozin pill, both, or a placebo. The nasal spray is designed to deliver insulin directly to the brain without affecting glucose levels.