Correlation between cognition and plasma noradrenaline level in Alzheimer's disease: a potential new blood marker of disease evolution.

Recent evidence showing degeneration of the noradrenergic system in the locus coeruleus (LC) in Alzheimer's disease (AD) has motivated great interest in noradrenaline (NA) as a potential brain hallmark of the disease. Despite the current exploration of blood markers for AD, the deregulation of the plasma NA concentration ([NA]plasma) in AD is currently not well understood. This retrospective study includes a cohort of 71 patients (32 AD patients, 22 with other dementia and 17 without dementia) who were given consultations for memory complaints in the Cognitive Neurology Center of Lariboisière (Paris) between 2009 and 2014. As previously described in brain tissue, we show for the first time a linear correlation between [NA]plasma and Mini Mental State Examination (MMSE) score in AD patients. We observed that high [NA]plasma in AD patients was associated with higher [Aß1-42]CSF than in other AD patients with [NA]plasma similar to NC patients. In parallel, we observed a lower (p-Tau/Tau)CSF in AD patients with low [NA]plasma than in non-AD patients with [NA]plasma similar to [NA]plasma in NC patients. Our data suggest that [NA]plasma could be a potential biomarker of disease evolution in the context of AD and could possibly improve early diagnosis.