Previous research has shown that women are at a higher risk for developing Alzheimer’s disease (AD) than men. In a new study published in the journal Science Advances, US researchers from Scripps Research and Massachusetts Institute of Technology reported that the higher AD incidence in women could be linked to a modified immune system protein. In the study, researchers conducted post-mortem autopsies on 40 human brains. Half of the brains were from people who had died of AD and half were from people who hadn’t. Each group had an equal number of males and females. Findings showed that women who died from AD had a higher amount of a chemically-modified version of an inflammatory immune protein called complement C3 in their brains compared to men who died with the disease.
The chemical reaction making this modified version of complement C3 is called protein S-nitrosylation. Results revealed that the amount of S-nitrosylated complement C3 was more than six times higher in female brains with AD than in male brains with AD. Levels were also 34.2 times higher in female brains with AD than in female brains without the disease. The study also showed that the hormone estrogen helps protect against the production of this form of complement C3. However, oestrogen levels drop during menopause. The researchers believe the drop in estrogen caused by menopause may leave women more vulnerable to this modified version of complement C3.