Brain, immune system and selenium: a starting point for a new diagnostic marker for Alzheimer’s disease?

The clinical diagnosis of Alzheimer's disease (AD) is based primarily on neuropsychological tests, which assess the involutive damage, and imaging techniques that evaluate morphologic changes in the brain. Currently available diagnostic tests do not show complete specificity and do not permit accurate differentiation between AD and other forms of senile dementia. The correlation of these tests with laboratory investigations based on biochemical parameters could increase the certainty of diagnosis. In recent years, several biochemical markers for the diagnosis of AD have been proposed, but in most cases they show a limited specificity and their application is invasive, requiring, in general, sampling of cerebrospinal fluid. Thus, the use of a peripheral biochemical marker could represent a valuable complement for the diagnosis of this disease. Several studies have shown a relationship between neurodegenerative disorders typical of the ageing process, weakening of the immune system and alterations in the levels of selenium and of the antioxidant selenoenzymes in brain tissues and blood cells. Among blood cells, neutrophil granulocytes uniquely express the selenoenzyme methionine sulfoxide reductase B1 (MsrB1). In a preliminary analysis carried out on neutrophils from subjects affected by AD, we observed a significant decline in MsrB1 activity compared to normal subjects. Therefore, we deem it of particular interest to explore the potential use of MsrB1 as a selective peripheral marker for the diagnosis of AD.