Like Diabetes, Like Alzheimer's

Insulin resistance tied to brain shrinkage in areas affected by Alzheimer disease

(RxWiki News) The hormone insulin plays a central role in diabetes. Now, it seems the hormone may also play a role in the early signs of Alzheimer's disease.

Insulin resistance (when the body does not properly use to insulin) may be linked to the shrinking of brain areas involved in muscle control, memory, emotions and speech, according to recent research.

This means your blood sugar level may impact Alzheimer's patients.

"Exercise your body and mind."

Insulin resistance has been shown to affect areas of the brain also affected by Alzheimer's disease, said Barbara B. Bendlin, PhD, of William S. Middleton Memorial Veterans Hospital in Wisconsin, and colleagues in background information to their study.

With that in mind, the researchers thought that insulin resistance could also play a role in the development of Alzheimer's.

Insulin is a natural hormone the body needs to use glucose (sugar) for energy. When some becomes insulin resistance, levels of sugar in the blood can rise, which can lead to prediabetes and diabetes.

From their study, Dr. Bendlin and colleagues found that patients with higher levels of insulin resistance at the beginning of the study had less gray matter - a part of the brain involved in memory, muscle control, speech, sensory perception (seeing and hearing) and emotions.

After 4 years, higher levels of insulin resistance were still associated with less gray matter.

In addition, higher levels of insulin resistance were associated with less brain volume in areas such as:

  • the medial temporal lobe - thought to be involved in memory of facts, knowledge, time, places and associated emotions
  • prefrontal cortex - involved in decision making, telling the difference between good and bad and predicting outcomes among other functions
  • precuneus - involved in self-consciousness, memories related to the self, and situating oneself in a physical space or preparing for movements within that space

The researchers also found that higher insulin resistance was related to shrinking of the medial temporal lobe - also known as atrophy of the medial temporal lobe.

This atrophy was linked to poorer scores on the Rey Audiotory Verbal Learning Test (RAVLT) - a measure of verbal learning and memory. Higher levels of insulin resistance, which led to higher levels of brain shrinkage, were associated with worse RAVLT scores.

That is, as brain shrinkage worsened, so too did RAVLT scores.

The authors concluded that their findings suggest that insulin resistance in middle-aged adults was associated with brain shrinkage in areas of the brain affected by Alzheimer's disease.

At the beginning of the study, the researchers measured insulin resistance, gray matter volume and RAVLT scores of 372 participants. About 4 years later, the same was done in another 121 participants.

The study was published October 15 in Diabetes Care, a journal of the American Diabetes Association.

Review Date: 
October 22, 2012