“Type 3 Diabetes” – Does Insulin Resistance Play a Role In Alzheimer’s?

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Picture of a Human Head With Cogs Representing a Brain.In recent years, some researchers have proposed the name ‘type 3 diabetes’ for Alzheimer’s disease.

Significant debate and controversy exist in regard to this term, but some peer-reviewed research suggests some links between blood glucose and insulin dysregulation and Alzheimer’s (1).

In short; the name ‘type 3 diabetes’ covers the hypothesis that Alzheimer’s results from insulin resistance of the brain.

This article takes a deeper look at this theory of Alzheimer’s.

What is Alzheimer’s?

Alzheimer’s disease is a chronic condition in which brain neurons slowly degenerate and die (2, 3).

As a result, we see progressive memory loss and rapid declines in cognitive ability (4).

Sadly, the condition can hit anyone.

Someone being physically fit or having an intelligent mind is not relevant; the disease doesn’t discriminate, and it takes no prisoners.

A Cruel Condition

Alzheimer’s patients typically experience a slow deterioration; patients eventually lose the ability to interact with their environment, communicate, and even remember their family.

Ultimately, Alzheimer’s disease is fatal, and patients usually die from a resulting complication such as pneumonia (5).

Worse still, it’s not only the patient that suffers.

Alzheimer’s caregivers often have to spend all their time and money to look after their family member, and it’s a very emotionally and physically demanding job.

Key Point: Alzheimer’s Disease is a devastating condition that has been increasing in prevalence. It is seen as a chronic and progressive disease that slowly decreases the patient’s ability to think, move, communicate, and live everyday life.

An Old Man Looking Confused.Why is the name ‘Type 3 Diabetes’ Proposed For Alzheimer’s?

There are three types of diabetes:

  • Type 1 diabetes occurs when the pancreas cannot produce insulin.
  • When the body cannot produce sufficient insulin and the body’s cells becomes resistant to the effects of the hormone, a type 2 diabetes diagnosis follows.
  • Type 3 diabetes is now being proposed by some researchers to describe Alzheimer’s, due to the brain insulin resistance link. Generally speaking, diagnosis usually occurs in those over the age of 65, but the disease can develop over decades (6).

With this ‘type 3’ name, Alzheimer’s is being associated with the various so-called “diseases of civilization” that are part of the metabolic syndrome (7).

Potential Harms of the Modern Western Diet

For a significant part, these problems stemming from glucose and insulin issues relate to the food we eat.

And unfortunately, the modern Western—perhaps global—diet revolves around industrially processed food.

In fact, a study analyzing consumer purchases shows that 77% of all grocery purchases are either moderately (16%) or highly (61%) processed (8).

These foodstuffs contain significant amounts of calories, sugar, and refined carbohydrates, and eating them constantly can result in prolonged high blood-glucose and insulin levels.

Over time, this can potentially lead to worsening insulin resistance and eventually, metabolic disease (9).

Key Point: Some researchers believe that the modern diet may play a role in the etiology of Alzheimer’s disease.

The Potential Link Between Alzheimer’s and Diet

 

Now that we have looked at the theory of Alzheimer’s being “type 3 diabetes” – is there any actual evidence to support this?

The truth is that there is no conclusive evidence.

However, some of the existing research suggests there may be links between impaired glucose/insulin and the onset of Alzheimer’s disease.

Here is an overview.

Recent Research Findings

  • A peer-reviewed review of the evidence showed that impaired insulin signaling may cause Alzheimer’s disease. In this particular study, the researchers were quite assertive with their conclusion that “it is justified to refer to Alzheimer’s as type 3 diabetes” (10).
  • Some researchers have proposed that an excessive amount of carbohydrate–especially fructose–and a deficiency of fat and dietary cholesterol may potentially lead to Alzheimer’s disease (11).
  • Researchers at the Department of Biopathology and Medical and Forensic Biotechnologies outline their belief that Alzheimer’s disease has a high prevalence in Western society due to incorrect diet and poor lifestyle (12).
  • Suzanne M. de la Monte, a researcher at the Department of Medicine, Pathology, Neurology, and Neurosurgery at Rhode Island Hospital and the Warren Alpert Medical School of Brown University recently published a paper reviewing the evidence. According to the researcher, there is “growing evidence” that suggests brain insulin resistance is a major contributor to Alzheimer’s. Particularly, abnormalities in biochemical, molecular, and signal transduction are almost the same as those seen in type 2 diabetes (13).
  • Research coming out of the Department of Neurology at Zhongshan Hospital University demonstrated that Alzheimer’s patients show “cerebral glucose hypometabolism”. In other words, this means that patients have an abnormally slow rate of utilizing glucose in their brain, possibly due to impaired insulin signaling (14).
  • A recent paper published in the Journal of Insulin Resistance by Amy Berger discussed how declines in the cerebral (brain) metabolic rate of glucose can begin in those with genetic risk for Alzheimer’s as young as their thirties. And impaired cell responses to insulin may be behind these declines (15).
  • Researchers have demonstrated that, even in the early stages of Alzheimer’s, cerebral glucose utilization is reduced by up to 45% (16).

The Hypothesis of Alzheimer’s and Brain Insulin Resistance

Illustration of a Human Brain.The studies referenced above all suggest that chronically elevated blood sugar and insulin issues may be causational in Alzheimer’s, hence the proposed ‘type 3 diabetes’ name.

According to this theory, here is a simple plain English overview:

As the brain becomes resistant to the effects of insulin, it can no longer efficiently utilize glucose.

When the brain cannot correctly use glucose, it builds up in the brain (hyperglycemia) and leads to oxidative stress and the formation of advanced glycation end products.

Both of these processes further damage the brain, promote accumulation of amyloid beta (plaque in the brain) and impair insulin signaling (17).

According to the theory, our brain’s neurons will decline as the rate at which they can utilize energy (glucose) drops.

And eventually, they will die.

Key Point: Some evidence suggests that the pathology of Alzheimer’s disease links to brain insulin resistance.

Potentially Supportive Evidence: Alzheimer’s Risk Factors

If we look at the risk factors for Alzheimer’s disease, then we can see a potentially important pattern.

Chronic Sleep DeprivationLack of Exercise
ObesityPoor Diet
Sleep Apnea

Interestingly, each of these factors has been associated with the risk of developing Alzheimer’s, and each one also relates to how well we metabolize glucose.

In the sections below, you can see the references that support this.

A Sleep-Deprived Man Who Cannot Get To Sleep.Chronic Sleep Deprivation

  • Chronic sleep disturbances are a stressor that can trigger earlier onset of Alzheimer’s disease. The effects include memory impairment and damage to connections in the brain (21).
  • One week of sleep deprivation significantly reduces insulin sensitivity (22).

Lack of Exercise

  • In older adults with glucose intolerance, regular aerobic exercise leads to improvements in cognitive performance (23).
  • The “first line of defense” against Alzheimer’s is behavior that increases insulin sensitivity, such as physical exercise (24).

Obesity

  • The epidemic of diseases relating to insulin resistance, such as obesity and type 2 diabetes, are “driving the significant increases in Alzheimer’s disease” (25).
  • Obese adolescents with insulin resistance have higher levels of circulating molecules that have links to increased risk of Alzheimer’s in the elderly (26).

A Man Eating Two Donuts - Chocolate and Strawberry.Poor Diet

  • The typical Western diet promotes higher fasting blood glucose levels (27).

Sleep Apnea

  • There is a theory that sleep apnea can increase insulin resistance. Additionally, a wealth of evidence suggests that sleep apnea has a causal relationship with dementia (29, 30).
Key Point: The major risk factors for Alzheimer’s all share a common associations to glucose dysregulation and insulin resistance.

Conclusion

In conclusion, there are some interesting links between glucose dysregulation and Alzheimer’s disease.

However, at this point, this is only a hypothesis, and it is too early to promote the name ‘type 3 diabetes’.

Hopefully, future research will make the roots of Alzheimer’s disease more clear.

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