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Doctors have announced the results of a study of a small number of patients with Alzheimer's and amnestic mild cognitive impairment whose memories improved after taking insulin spray.

Insulin Also Improves Memory in People Who Have "Pre-Alzheimer's"

Doctors at the University of Washington Medical School in Seattle and the US Veterans Administration's Puget Sound Health Care System have announced the results of a study of a small number of patients with Alzheimer's and amnestic mild cognitive impairment (aMCI) whose memories improved after taking inhaled insulin.

It turns out that the brain makes much of its own insulin. Like the rest of the body, certain parts (but usually not all) of the brain can become insulin resistant. The brain attempts to force glucose into those regions of the brain by releasing more insulin into the blood vessels inside the skull, but the cells just become even more insulin resistant. Eventually the brain is unable to make enough insulin and the same kinds of changes that happen in arteries also happen in the brain.

In terms of treatment, this poses a dilemma. Giving an insulin resistant type 2 diabetic insulin injections  won't necessarily provide insulin to the brain. Any insulin for the brain itself has to be applied more directly, and there are severe complications (including death) when insulin is injected directly into the brain. How is it possible to give the brain extra insulin.

It turns out that insulin inhaled through the nose reaches the brain quickly. A nasal inhalation device filled with micronized insulin particles gets insulin into the brain—but why isn't more insulin better for the brain? Why did the Alzheimer's patients who got just 20 units a day do better than the Alzheimer's patients who got 40 units a day?

The reason for this is that insulin itself causes insulin resistance. Providing the brain a little extra insulin helps the regions of the brain that are not insulin resistant use sugar more effectively and produce more energy. There are different numbers of glucose receptors in different parts of the brain. But providing the brain with too much insulin just shuts down other parts of the brain that seek to protect themselves from absorbing too much sugar.

Nasal insulin is not going to be available at your local pharmacy anytime soon, so if you are a type 2 diabetic, what can you do to protect yourself from developing "type 3" diabetes, insulin deficiency of the brain that causes Alzheimer's? Here are some suggestions.

  • Train your brain. Whether it's learning a new hobby—especially learning a new athletic activity—learning a new language, meeting new people, going to new places, or starting a new career, using your brain requires energy. Your brain cells are less likely to become insulin resistant, closing themselves off from receiving glucose from the bloodstream, if they need more glucose for more energy because you are using your brain in new ways.
  • Control your diabetes, keeping your blood sugar levels as constant as you can. It's better to maintain blood sugar levels that are always approximately normal, that is, around 90 mg/dl or 5.5 mmol/L, but if you can't keep blood sugar levels normal, at least keep them from fluctuating between very high levels and very low levels. If your blood sugar levels get too low, your brain can't function. If your blood sugar levels get too high, parts of your brain will protect themselves from free radical damage by stopping the inflow of glucose by becoming insulin resistant.
  • Take vitamin D. Like insulin, vitamin D is not helpful if it is taken in megadoses. Too much vitamin D does not help your brain. Up to 1000 IU a day, however, increases sensitivity to insulin and helps preserve memory, even in Alzheimer's and aMIC.

  • Park SA. A common pathogenic mechanism linking type-2 diabetes and Alzheimer's disease: evidence from animal models. J Clin Neurol. 2011 Mar, 7(1):10-8. Epub 2011 Mar 31.