A Pilot Study on Blood Concentration of β-Amyloid (40 and 42) and Phospho-Tau 181 in Horses

In humans, aging is often accompanied by cognitive decline, as seen in Alzheimer's disease. In contrast, the aging process in horses remains poorly characterized. This study aims to explore the presence of blood-based biomarkers associated with cognitive degeneration in this species. Twenty-three Arabian horses were enrolled, and 5 mL of blood was collected from each to measure serum levels of β-amyloid peptides (Aβ40 and Aβ42) and phosphorylated tau protein (pTau181), both considered reliable indicators of cognitive impairment in other species. Aβ42 was undetectable in all samples, while pTau181 ranged from 5.38 to 54.42 pg/mL and Aβ40 from 67.4 to 743.9 pg/mL. Statistical analysis of the data, performed with the non-parametric Spearman test, did not reveal any correlation between age and the concentrations of Aβ40 and pTau. The pTau/Aβ40 ratio also did not appear to be correlated with the age of the subjects. Interestingly, none of the horses exhibited behavioral changes or clinical signs suggestive of cognitive dysfunction. This absence of symptoms may be related to the undetectable levels of Aβ42, the isoform considered crucial in initiating tau phosphorylation and subsequent neurodegeneration, despite possibly being present at concentrations higher than those typically found in healthy humans.