Research published in April 2016 shows that high insulin levels can cause Alzheimer’s. Alzheimer’s disease has been known to occur more often in diabetics. But until recently it was not known why there would be this association. New research from New York University (NYU) has shed light on this puzzle. The key is an enzyme that breaks down insulin, called insulin-degrading enzyme (IDE). Melissa Schilling (no relation to me), an innovation professor at NYU has discovered the metabolic pathway between diabetes and Alzheimer’s disease. This finding has enormous implications regarding the prevention of Alzheimer’s, as I will discuss below. Here is a link to the original paper.
Background information about Alzheimer’s
Alzheimer’s disease affects about 5.2 million Americans and 44 million people worldwide. There is a progressive loss of cognitive functioning over a long period of time due to senile plaques in the cerebral cortex and the subcortical areas of the brain. These senile plaques are made up of amyloid-beta substance and of neurofibrillary tangles. This protein material is like glue, which prevents the neurons from working properly and causes memory loss and the confusion, which is so typical for Alzheimer’s patients. Normally amyloid-beta is in solution and prevents lipoproteins in the brain from oxidizing. But when the insulin-degrading enzyme is busy breaking down high levels of insulin, this enzyme system is overwhelmed. Amyloid-beta gets supersaturated, as it is not eliminated at a normal speed. This leads to the glue-like deposits of amyloid-beta in Alzheimer’s brains.
It is estimated that in 2004 the direct cost to the US of Alzheimer’s disease was $214 billion. By 2050 this could go up to $1.5 trillion, if no cure is found.
High insulin levels can cause Alzheimer’s, but other mechanisms too
Professor Schilling found in her research that there are four main malfunctions that can lead to high amyloid-beta in the brain of Alzheimer’s patients.
- With diabetes type1, when the patient does not receive enough insulin, the insulin-degrading enzyme in the brain is not working hard enough. This results in inadequate removal of amyloid-beta from the brain and neurofibrillary tangles of amyloid-beta are deposited.
- IDE requires zinc as a co-factor to work properly in breaking down amyloid-beta. Zinc deficiency is quite common, particularly in older people. With this mechanism insulin levels are normal, but amyloid-beta is removed poorly, as IDE function is diminished.
- In early type 2 diabetes there are high insulin levels and there is a competitive inhibition of the elimination of insulin and amylin-beta. This is probably the most common form of getting Alzheimer’s disease.
- Excess production of an amyloidogenic protein can lead to an overabundance of amylin-beta, which overwhelms the insulin-degrading enzyme.
What treatment options are there for Alzheimer’s disease?
Several implications follow from the four mechanisms that were described above.
- If a type 1 diabetic patient is insulin deficient, intranasal insulin would be beneficial.
- If the patient has type 2 diabetes, intranasal insulin or injected insulin would be the wrong approach. As stated earlier, there is the competitive inhibition of the elimination of insulin and amylin-beta. It is the insulin-degrading enzyme, which is the limiting factor. Simple dietary changes are needed where sugar is cut out and starchy foods are limited. This normalizes insulin levels and the IDE function returns to normal.
- Alzheimer’s patients and patients with mild cognitive dysfunction should be tested with glucose tolerance tests (GTT). It the test is abnormal, a knowledgeable dietician should be consulted.
- Obesity is strongly associated with hyperinsulinemia and diabetes. Again frequent GTT should be done followed by dietary intervention when abnormal.
- Professor Melissa Schilling stated that 86 million Americans are pre-diabetic, but they have no symptoms. Only glucose tolerance testing can diagnose that condition. This will prevent a lot of cases of diabetes and Alzheimer’s disease.
- Large parts of the population have no knowledge of the glycemic index of carbohydrates. In order to limit glucose overload and excessive insulin production educational nutritional programs are needed. This will be a powerful tool in Alzheimer’s disease prevention.
It has been known for some time that diabetics have a higher rate of Alzheimer’s disease. Alzheimer’s has also been called “Diabetes of the brain” or “Type 3 Diabetes”. This new research has shed some light on the connection of elevated insulin to Alzheimer’s disease. It was news to me that there is a competitive inhibition of the elimination of insulin and amylin-beta via the insulin-degrading enzyme. It boils down to recognizing that sugar overconsumption causes Alzheimer’s disease. If you want to keep your brain power until a ripe old age, you better eliminate a lot of sugar and adopt a healthy Mediterranean diet.
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