A new mechanism that may partly explain the onset of Alzheimer’s disease has just been demonstrated by researchers at Duke University (United States). Published in the Journal of Neuroscience on April 14, their study focuses on arginine, an essential amino acid found in meat, the fish and dairy products, which we use to produce protein.
For this research, the scientists used mice that were genetically modified so that their immune systems resembled ours. Like the other rodents used, these mice developed Alzheimer’s disease with the same characteristics (protein plaques, neurofibrillary degeneration, loss of neurons, loss of memory, etc.).
The gradual emergence of these symptoms in these animals allowed researchers to study their brains long enough to see how the disease started, says Dr. Matthew Kan, co-author of the study. By studying the abnormalities of the immune system of these mouse, they noticed that certain key cells of immunity residing in the brain, the microgliocytes, began to divide and evolve at an early stage of the disease. The microgliocytes of these sick mice produced an enzyme, arginase, capable of breaking down arginine, the precious amino acid found in regions of the brain linked to memory.
Thus, “if the destruction of arginine is so important in the mechanism of the disease, it might be possible, in [l’empêchant] reverse this pathology, ”said Dr. Carol Colton, professor of neurology at Duke University and co-author of the study.
An anti-cancer drug to neutralize the arginase enzyme
To prevent this abnormal destruction of arginine, the researchers neutralized the arginase enzyme produced by microgliocytes with an anti-cancer drug called DFMO. Given to mice before the first symptoms of the disease appeared, it did reduce the protein plaques developed in their brains. Mice also performed better on memory tests.
“All this suggests to us is that by blocking this process of reducing arginine we can protect mice at least from Alzheimer’s disease,” says Dr Kan. Already tested in humans in the treatment of certain cancers, the DFMO molecule has never yet been evaluated as a potential therapy against Alzheimer’s.
Researchers are now studying the effect of this drug in mice after symptoms of Alzheimer’s disease appear, to see if it could reverse them.
While it’s tempting to think that eating more arginine will counteract its destruction and prevent Alzheimer’s disease, Dr. Colton advises against this practice. The brain is in fact protected by a protective barrier that determines the amount of arginine that can enter it.
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