Alzheimer’s and diabetes: studies that investigate the link – 12/19/2023 – Balance and Health

Few diseases have such a devastating impact as Alzheimer’s. Although we are aware that with age we will lose our memory, we are terrified by the idea that we will eventually not be able to recognize our loved ones or ourselves.

These memories, which have been stored in the brain for years, disappear until they disappear for good. Although efforts to find a treatment have not yet yielded the desired results, we have learned a lot along the way.

Recent research has proposed a new approach to the development of Alzheimer’s disease. It may not just be a matter of the accumulation of beta-amyloid plaques and hyperphosphorylated tau tangles, as previously thought, but also of how our brain cells interact with insulin.

Insulin is a hormone that regulates blood glucose concentrations, which is why it is closely linked to another disease, diabetes mellitus. In fact, these diseases share risk factors: advanced age, diet, obesity and chronic inflammation.

Could there be a relationship between the brain and the pancreas that links the two diseases?

Let’s imagine for a moment that neural connections resemble cables in an electrical network through which thought and memory information would be transmitted.

These cables start from neurons and reach others. Neurons are cells that need fuel to function, and the essential fuel is, precisely, glucose.

Insulin acts like a bell on the door of cells. When the bell rings, the cell knows to open the door for glucose to enter. Without this bell, even if there is abundant glucose in the blood, the cell doesn’t notice it, doesn’t open the door and doesn’t receive the fuel.

When the cell receives more glucose than it needs, it ends up generating insulin resistance. In other words, he is reluctant to open the door.

This is why insulin resistance, linked to type 2 diabetes, promotes the accumulation of sugar in the blood. Furthermore, it promotes the formation of beta-amyloid plaques, characteristic of Alzheimer’s.

Studies with rats revealed that the administration of streptozocin, a drug used to induce diabetes in animal models, generates insulin resistance and neurodegeneration similar to Alzheimer’s.

The relationship has also been observed in humans, although it has not been linked to greater accumulation of beta-amyloid or tau tangles in brain autopsies.

The inflammation link

A chronic state of low-grade inflammation generated by insulin resistance would also link both diseases.

Inflammation is a fundamental process for combating external aggressions and repairing the damage caused. When it becomes chronic, it can lead to changes that are associated with metabolic diseases such as obesity, cardiovascular disease, diabetes and Alzheimer’s.

In this scenario of insulin resistance, oxidative stress and inflammation, cells enter apoptosis (programmed cell death). If this happens, if the cells die, the network of cables will become tangled and the brain will not function properly. Then the patient starts to forget and stops processing the information. This is how Alzheimer’s appears.

All of this suggests that metabolic problems may be the key to both diseases. For this reason, some researchers have suggested that Alzheimer’s be considered a new type of diabetes.

Type 3 diabetes?

The new type of diabetes would be called “type 3 diabetes.” It would join type 1, of more genetic than environmental origin; type 2, with more environmental influence than genetics; and gestational, which occurs in some pregnant women.

The term emerged in 2005 at the University of Rhode Island, whose researchers proposed that Alzheimer’s could be a form of cerebral diabetes, characterized by insulin resistance and metabolic dysfunction.

Although it is important to highlight that this is not a term accepted by the entire scientific community, it is a hypothesis that can be useful in contributing to a more complete view of the disease.

The links between the two diseases have become stronger, but there is still much to discover, especially about how to use this information to benefit patients.

Since insulin resistance and inflammation play central roles, they could share therapeutic strategies. In this sense, promoting healthy lifestyles, including nutrition, could have a positive impact on the prevention and treatment of diabetes and Alzheimer’s disease.

The link between Alzheimer’s and diabetes could transform our understanding of both diseases.

The idea of ​​type 3 diabetes, although there is no scientific consensus, could open new doors for research linking the two diseases, with insulin resistance and inflammation taking center stage, as well as effective treatments.

With each new discovery we get a little closer to treating diseases that affect millions of people around the world. Are we on the threshold of a new era in Alzheimer’s disease research? Only time and science will be able to answer this question.

*Javier Sánchez Perona is a scientist at the Superior Council for Scientific Research (CSIC), in Spain, and professor at the Pablo de Olavide University, in Seville, Spain.

**This article was published on The Conversation and reproduced here under a Creative Commons license. Click here to read the original version.