Affiliations: [a]
National Institute of Mental Health, Klecany, Czech Republic
| [b] Third Faculty of Medicine, Charles University, Prague, Czech Republic
| [c] Mitchell Center for Neurodegenerative Diseases, University of Texas Medical Branch, Galveston, TX, USA
| [d] Department of Neurology, and Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, TX, USA
Correspondence:
[*]
Correspondence to: Rakez Kayed, 301 University Blvd, Route 1045, Galveston, TX 77555-1045, USA. Tel.: +1 409 772 0138; E-mail: rakayed@utmb.edu and Michala Kolarova, Topolova, 748, 250 67, Klecany, Czech Republic. Tel.: +420 283088232; E-mail: michala.kolarova@nudz.cz.
Abstract: Although tau protein was long regarded as an intracellular protein with several functions inside the cell, new evidence has shown tau secretion into the extracellular space. The active secretion of tau could be a physiological response of neurons to increased intracellular amounts of tau during the progression of tau pathology. We looked for potential differences in the serum levels of toxic tau oligomers in regards to cognitive impairment of subjects. We detected tau oligomers in the serum of Alzheimer’s disease (AD) patients, but they were also present to some extent in the serum of healthy older subjects where the levels positively correlated with aging (Spearman r = 0.26, p = 0.016). On the contrary, we found lower levels of tau oligomers in the serum of mild cognitive impairment (MCI) (p = 0.033) and MCI-AD (p = 0.006) patients. These results could suggest that clearance of extracellular tau proteins takes place, in part, in the periphery. In the case of MCI patients, the lower levels of tau oligomers could be the result of impaired clearance of tau protein from interstitium to blood and consequent accumulation of tau aggregates in the brain.
Keywords: Alzheimer’s disease, oligomers, serum, tau protein
