The weaker sex and Alzheimer's
Alzheimer's disease affects women more often, scientists have found
Women's brains accumulate scraps of "protein garbage" faster, which accelerates the development of Alzheimer's disease and the manifestation of its clinical symptoms. This is told by researchers who published an article in the journal JAMA Neurology (Buckley et al., Sex Differences in the Association of Global Amyloid and Regional Tau Deposition Measured By Positron Emission Tomography in Clinically Normal Older Adults).
"There is a lot of evidence that women are more likely to suffer from Alzheimer's disease, but no one has quantified this. We checked whether there are differences in the levels of tau protein in the brains of women and men who have not yet acquired it," write Rachel Buckley from Harvard University (USA) and her colleagues.
Both Alzheimer's disease and Parkinson's disease are caused by the accumulation of various "protein debris" in nerve cells, which gradually kills neurons in different parts of the brain. Their death leads to memory loss and senile dementia in the first case, and to loss of control over the limbs in the second.
In both cases, scientists do not yet understand the mechanisms that cause brain cells to accumulate tau protein, beta-amyloid plaques, alpha-synuclein tangles and other potential causes of these diseases. For this reason, biologists not only cannot create drugs for Alzheimer's and Parkinson's diseases, but also cannot understand whether the former is contagious and for what reasons they develop.
Buckley and her colleagues have been studying for many years how both types of protein accumulate in the brains of people who have not yet suffered from Alzheimer's disease, using positron tomographs and other diagnostic systems that "highlight" their clusters.
Recently, scientists have been interested in whether there are differences in the formation of these molecules and their "tangles" in men and women who have not yet suffered from dementia, but are at risk, and in patients who have already become victims of Alzheimer's disease.
Having recruited three dozen volunteers, the scientists injected into their bodies special radioactive tags attached to beta-amyloid and tau protein, and counted the number of their molecules in their brains. After that, they separated them by gender and compared them with each other.
As this analysis showed, there were no differences between the sexes among healthy people, however, when even small amounts of beta-amyloid appeared in the brains of volunteers, the picture changed dramatically.
On average, the nerve cells of the sick women contained 6-10% more tau protein than in men with a similar proportion of the second type of "garbage". In the most severe cases, the difference reached 40-70%.
Such changes, according to neurophysiologists, appeared brightest and fastest in the entorhinal cortex of the brain, one of the memory centers that usually becomes the first victim of Alzheimer's disease. Scientists believe that these small differences in the "normal" proportions of beta-amyloid and tau protein can accelerate the degeneration of nervous tissue and contribute to the rapid development of dementia.
Interestingly, similar conclusions were reached by Russian and foreign epidemiologists who studied the spread of the epidemic of dementia and other disorders of the nervous system associated with Alzheimer's disease. Their calculations showed that 27 million representatives of the weaker sex and about 17 million men suffer from it.
Neither scientists know what these differences are related to yet, but Buckley and her colleagues believe that they may be caused by some peculiarities in the work of women's bodies.
For example, the fairer sex, on average, are more susceptible to inflammation and disorders in the immune system, potentially contributing to the accumulation of pathogenic proteins in their cells. The researchers hope that experiments on animals with "human" versions of the genes responsible for their production will give a more accurate answer to this question.
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