Type 3 Diabetes? The Link Between Insulin Resistance and Alzheimer’s – WTOP

Posted: May 6, 2020 at 12:46 am

Unlike Type 1 or Type 2 diabetes, Type 3 diabetes isnt an official clinical diagnosis. Its not an established medical

Unlike Type 1 or Type 2 diabetes, Type 3 diabetes isnt an official clinical diagnosis. Its not an established medical term at least not yet, points out Guojun Bu, chair of the department of neuroscience at Mayo Clinic in Jacksonville, Florida. But experts say the concept is still a useful one that speaks to the link between insulin resistance in the brain and dementia caused by the progressive brain disorder Alzheimers disease.

Insulin, a hormone produced by the pancreas, regulates glucose levels in the blood. With insulin resistance, the cells dont respond well to the hormone. That can lead to higher blood-sugar levels and the development of Type 2 diabetes (and before that, prediabetes, a precursor to the chronic condition). Research shows that, even short of a person developing diabetes, insulin resistance can impact the body and brain and lead to a range of health complications.

The concept of Type 3 diabetes comes from the idea that insulin resistance is linked, in many cases, to Alzheimers dementia, making it yet another form of diabetes. Of course, the term is also an oversimplification, says Dr. Gary Small, a professor of psychiatry at the UCLA Semel Institute and author of The Small Guide to Alzheimers Disease, since the association isnt completely understood.

Where it breaks down is that its not a 100% link not all patients who have Alzheimers disease have insulin resistance, and not all people who have insulin resistance have Alzheimers disease, Small explains. Now one could argue it could be a subtype of Alzheimers disease where theres that link.

[See: 9 Habits That May Reduce Your Risk for Developing Alzheimers.]

Insulin Resistance Isnt Limited to Diabetes

Today, more than 30 million people in the U.S. have diabetes, according to the Centers for Disease Control and Prevention. And many more people have insulin resistance which isnt routinely tested for.

Even though insulin resistance is associated with diabetes, its much more common than diabetes, says Suzanne Craft, a professor of gerontology and geriatric medicine and director of the Alzheimers Disease Research Center at the Wake Forest School of Medicine in Winston-Salem, North Carolina. It can lead to diabetes, but it can also cause a host of other complications Alzheimers disease being one of those. Those who have insulin resistance, particularly at mid-life, are at greater risk for developing Alzheimers disease, Craft says.

There is a lot of literature supporting the association between insulin resistance and various types of dementias that disproportionately affect older patients, particularly Alzheimers disease, echoes Dr. Samoon Ahmad, a professor of psychiatry at the NYU Grossman School of Medicine and founder of the Integrative Center for Wellness in New York City. Insulin resistance in Alzheimers is a growing area of focus. As noted in a 2018 review article in the Frontiers in Neuroscience, The epidemiological connection between diabetes, obesity, and dementia represents an important public health challenge but also an opportunity to further understand these conditions. The key intersection among the three diseases is insulin resistance.

The association also applies to conditions that are related to insulin resistance, including Type 2 diabetes and obesity, notes Christian Pike, a professor in the Leonard Davis School of Gerontology at the University of Southern California.

Researchers arent exactly sure why insulin resistance is associated with higher rates of Alzheimers disease and related forms of dementia. But theres no shortage of theories and possible mechanisms that have been suggested to explain the relationship. And, generally speaking, its well-known that insulin plays an important role in brain function.

Insulin basically transports glucose from the bloodstream into cells, Small says. So that makes sense if your insulin transport system getting those nutrients to brain cells is not functioning properly, that the brain is not being fed its main energy source as well.

Insulin has a number of important roles to play in healthy brain function, Craft notes. Accordingly, she says, there are several pathways through which insulin resistance could increase the risk for Alzheimers disease. For one thing the hormone helps brain cells form connections. It helps the brain repair itself from injury and generate new brain cells, Craft says. It plays a very important role in memory.

So dysfunction in regards to how insulin is used or isnt can have a meaningful impact on cognitive function. Insulin resistance, by definition, is the brain not responding normally to insulin, Craft explains. So by depriving the brain of all of these various functions of insulin, insulin resistance creates an environment in the brain that makes it vulnerable to developing the kind of injury thats associated with Alzheimers disease.

Given the important role of insulin, it could be used as a possible treatment for mild cognitive impairment and Alzheimers disease, as noted in a 2018 research review published in the Journal of Neurology. Insulin delivered through a nasal spray, for instance, has been shown to improve recall of story details or story recall in patients with Alzheimers or mild cognitive impairment.

Ultimately, insulin may be delivered as a means to improve or at least stabilize cognition in people with Alzheimer and other dementias. In limited studies, intranasal insulin delivery has been shown to lead to some cognitive benefits in dementia patients, Pike points out.

Theres evidence that the Alzheimers brain may be less sensitive to insulin, which is critical for memory formation and maintenance, Bu adds. But more research is needed to explore the possibilities for managing or treating Alzheimers with insulin.

In the meantime, whats already well established is that preventing insulin resistance can protect a persons overall health including brain health.

[See: 10 Myths About Diabetes.]

Preventing Insulin Resistance Through Lifestyle Changes

Factors out of ones control namely genetics, having a family history of insulin resistance or diabetes can predispose a person, or raise ones risk of developing insulin resistance. But lifestyle still plays an outsized role in preventing it.

Lifestyle changes are among the most effective ways of preventing or delaying Alzheimers disease, too. And they are recommendations weve all heard before, Craft says.

Those include:

Getting regular exercise.

Consuming a healthy, balanced diet.

Maintaining a healthy weight.

If a person did all of those things, the rate of insulin resistance would be dramatically reduced, Craft says.

What we dont understand is why some people have a greater tendency to develop insulin resistance than others, even when their diets and levels of exercise are more or less than the same, Ahmad says. Genetics is likely one answer, but there may be other factors we are not aware of, and these may complicate the association between Alzheimers risk and diet.

Even so, the role of lifestyle remains important. While some individuals are at a significantly higher risk of developing either diabetes or Alzheimers because of genetic factors, getting regular exercise and eating healthy will certainly lower ones risk of developing Type 2 diabetes and could lower ones risk of developing Alzheimers disease, Ahmad adds.

Federal physical activity guidelines suggest getting at least 150 minutes of moderate intensity exercise, like brisk walking, weekly. Shifting to a sustainable, well-rounded, balanced eating pattern rather than say an extreme diet is also encouraged.

While most people like to hear about fad diets that produce unrealistic or unsustainable results, the best way to plan ones meal is to avoid excessive amounts of alcohol and processed foods particularly those high in saturated fats and sugars and to try to eat foods that are as close to their whole or natural states as possible, Ahmad says. This means a diet that is rich in whole grains, lean proteins, and fruits and vegetables, particularly raw fruits and vegetables.

From improving heart health to brain health and staying disease-free in general for as long as possible data strongly suggests turning away from a traditional Western diet thats heavily processed and high in saturated fat and sugar. This type of eating pattern has been linked with a higher risk of Alzheimers disease.

[See: Best Foods for Brain Health.]

The kind of diet that protects the brain is generally a Mediterranean-style diet that includes fresh fruits and vegetables, legumes, healthy fats from omega-3s which are anti-inflammatory, Small says. You can get omega-3 fats from fish and nuts. He notes that the fruits and veggies provide antioxidants and may fight against wear and tear from oxidative stress that causes damage to neurons over the years. A diet that limits refined sugars and processed foods will lower risk for Type 2 diabetes as well as Alzheimers dementia.

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