A new study, by Harvard University, published in Scientific American suggests that Alzheimer’s may be caused by the body’s natural defenses to infections attacking the brain.
Alzheimer’s and Amyloid Beta
The study presents a brand new hypothesis on the origins of the debilitating disease. It has always been thought that amyloid beta had a role in to play in the disease, but for the first time it is suggested that this protein is actually produced by the brain when trying to defend itself against various bacteria or viral infections. These infections are not necessarily huge or debilitating attacks on the brain. They may be very mild, causing no side affects, but the aggressive and strong defense response triggered certainly has consequences over time.
As foreign invaders attack the brain, this amino acid becomes pivotal in the plaque-like substance that envelopes the infection, trapping whatever has penetrated the membrane, like a fly in ointment. However, once the bacteria, or fungus, or virus, has been destroyed, the remnants of this plaque remain, an empty prison cell if you will. As the amyloid builds up over time, this plaque is dotted all over the brain and begins to prevent connections from forming, which eventually will manifest itself as memory loss.
Before this study was published it was generally assumed that this amyloid build up served no purpose and was essentially junk that accumulated as people aged. Elsewhere in the body this defense system happens too, the difference being that white blood cells (like mom’s with teenage kids) come along afterwards and clean everything up.
To test the theory, they approached the problem from both sides, using mice as their guinea pigs (so to speak). If a bacterium were introduced to a brain cell, would amyloid be produced to defend itself; and if a mouse, that had no amyloid production, were to be infected, would the infection quickly overrun the defenses. Both hypotheses were found to be true.
What further supports this theory is that generally the most vulnerable part of the brain is the hippocampus, so this is where the bacteria can attack, meaning this is where the amyloid build up can occur. What function does the hippocampus serve… memory and learning, the two areas most damaged by Alzheimer’s.
Consequences of the Study
The results are considered intriguing and controversial by professionals working in Alzheimer research.
It could have far reaching consequences for the way the disease is tackled by scientists. While the amyloid build up has always been considered central in the causes of Alzheimer’s, it is now understood that the brain produces this as defense, so having small amounts present may not be troublesome, it is just important to control any excesses. The author of the study, Rudolph Tanzi, confirmed when discussing this build up, “we might want to think about just dialing it down,”
So far the study has only looked at testing this theory on animals, roundworms, fruit flies and mice. So far all the evidence indicates the validity of the idea, but no human testing has yet occurred. This is planned for the near future. Further trials are required to conclusively prove the theory, but sufferers (and also the immediate family, as they tend to be the ones who suffer just as much) will be heartened by any new breakthroughs to tackle this degenerative disease.
