P295 APOE polymorphism and cortical plasticity are independently associated with cognitive decline in Alzheimer’s disease

Abstract

Introduction APOE E4 allele associates not only with AD risk and a lower age onset, but also with faster cognitive decline and greater cerebral atrophy, suggesting a key role of this polymorphism in modulating both disease risk and clinical outcome. Objectives In this study we investigated the correlation between cognitive decline, motor cortical plasticity and cerebrospinal fluid (CSF) biomarkers profile of AD patients divided by APOE polymorphism in E4 allele carriers (E4) and homozygous E3 carriers. Materials and methods A monophasic Magstim 200 device was used to deliver intermitted/continuous theta burst stimulation (iTBS/cTBS) protocols. ELISA was used for determination of CSF biomarkers level. Forty-one AD patients underwent lumbar puncture for CSF withdrawal, blood screening for APOE polymorphism, stimulation protocols applied over the primary motor cortex and mini mental state examination (MMSE) at baseline and at 6-, 12- and 18-months. Results No difference was found in CSF biomarkers profile within the APOE variants group. I-TBS after-effects were significantly reduced in E3 in comparison with E4 AD patients. Correlation analyses revealed that the individual amount of iTBS induced plasticity correlated with delta-MMSE and total Tau showing that a less pronounced LTP-like plasticity and higher total-Tau CSF levels were associated with a higher delta-MMSE. Only in apoE4 patients Tau pathology correlates with cortical plasticity impairment and cognitive decline. A multivariate analysis showed that APOE polymorphism and LTP-like plasticity, but not t-Tau levels, are independently able to predict delta-MMSE in AD patients. Conclusions APOE variants show different level of cortical plasticity and are independently associated with clinical progression in AD patients. Tau pathology is specific for ApoE4 group driving cortical plasticity impairment and cognitive decline. ApoE4 patients represent a pure model of TAU-driven AD pathology. ApoE3 patients are characterized by different mechanisms of cortical plasticity impairment and clinical symptoms. LTP impairment is a marker of pathophysiological dysfunction in AD and, as such, it should be taken in account also for the adoption of new pharmacological strategies, considering AD as a disorder of synaptic plasticity.