Decreased plasmatic spermidine and increased spermine in mild cognitive impairment and Alzheimer's disease patients

Background: Current evidence suggests that upregulation of polyamines system plays a role both in cognitive deficit and synaptic loss observed in Alzheimer's disease (AD). Objective: The aim of this study was to determine the plasmatic concentration of polyamines in mild cognitive impairment (MCI) and AD patients in comparison with healthy controls (HC). Methods: Plasmatic polyamines were quantified using the AbsoluteIDQ (R) p1130 and liquid chromatography coupled to tandem mass spectrometry (LC/MS-MS). Results: The study group comprised 34 AD patients, 20 MCI and 25 HC. All individuals were followed for 4 years. During this period 8 amnestic MCI patients (40% of the MCI sample at baseline) converted to AD. Spermidine level was lower in both patient groups (AD; MCI) compared to HC (p = 0.007). Plasma levels of spermine were higher in the MCI group (p < 0.001), but decreased in the sub-sample of MCI patients who converted to AD (p = 0.043). No statistically significant differences were found in ornithine and putrescine levels (p = 0.056 and p = 0.126, respectively). Discussion: Our results suggest dynamic changes in the expression of polyamines in the MCI-AD continuum.