Alzheimer’s disease: why insulin is a new suspect

Johnson and Johnson recently announced that it was halting a clinical trial for a new Alzheimer’s drug after safety issues emerged. This latest failure adds to the dozens of large, costly clinical trials that have shown no effect in treating this devastating disease.

The growing list of failures should give us pause for thought – have we got the causes of Alzheimer’s all wrong?

In the first analysis of the disease, the German physician, Alois Alzheimer, noted odd changes in the brain of a patient who died of the condition. Alzheimer identified two kinds of protein aggregates that are not found in younger brains: plaques that are found between brain cells and tangles that are found inside brain cells.

Later research identified the proteins that made up the plaques as amyloid and those that form the tangles as tau. What these structures actually do is still under debate.

Unheeded warning

Alzheimer advised scientists not to jump to the conclusion that these proteins caused the disease. Unfortunately, his caution was ignored, and over the years it has become gospel that the build up of these proteins causes Alzheimer’s disease.

One problem is that it’s not possible to test, in a scientific experiment, if this theory is correct. Only in recent years has technology been developed that can test what these proteins do, and it is clearly not what scientists previously assumed. For example, genetically engineered mice that accumulate human amyloid in their brains show only mild impairment. But the pharmaceutical industry made up its mind a long time ago that amyloid is the culprit, and this has been the target for Alzheimer’s drugs ever since.

The aim of these drugs is to reduce the levels of amyloid in the brain, either by slowing down the formation of amyloid or by removing it from the brain. Both approaches have been tested many times now using different techniques and drug types. None of these trials have shown any effects, and some large drug companies, including Pfizer, have abandoned this area of research altogether.

The continued failure of new drugs to make a difference has to be interpreted as evidence that the amyloid protein is not the cause of Alzheimer’s disease. Some companies have changed their target to the tau protein. But again, drugs companies are assuming that a single protein is the cause of the disease.

Originally Published by The Conversation, continue reading here.

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