Exploring the effect of APOE ε4 on biomarkers of neurodegeneration in Alzheimer's disease.

BACKGROUND AND AIMS: This study aims to assess the association between APOE genotype and biomarkers of neurodegeneration in Alzheimer's disease (AD). METHODS: We performed a retrospective observational study at the University Hospital "P. Giaccone" in Palermo, Italy. We enrolled patients with cognitive decline, including AD. For each patient, we measured amyloid beta (Aß)42, Aß40, tau protein phosphorylated at threonine 181 (pTau), total tau (tTau), neurogranin, alpha-synuclein, and neurofilament light chain (NfL) in cerebrospinal fluid (CSF). RESULTS: The study population consisted of 194 patients (123 AD and 71 non-AD). AD patients have significantly lower Aß42 levels and Aß42/40 ratio and higher pTau, tTau, and NfLs levels than non-AD patients. In AD patients, the APOEε4 allele is associated with a significantly lower Aß42/40 ratio and higher levels of pTau, tTau, neurogranin, and alpha-synuclein. This association is not observed in non-AD patients. CONCLUSIONS: This study provides evidence of the significant impact of the APOE ε4 allele on neurodegenerative biomarkers in AD patients, highlighting its role in exacerbating amyloid and tau pathology as well as synaptic degeneration.

Evaluation of serum and cerebrospinal fluid biomarkers after vaccination against SARS-CoV-2.

OBJECTIVE: Vaccines are a major achievement of science, and new vaccines against SARS-CoV-2 are protecting the entire population from a life-threatening infection. Although several neurological complications or worsening of pre-existing neurological conditions after vaccination have been observed, whether a biological plausibility exist between new vaccines against-SARS-CoV-2 and neurological consequences is unclear. The aim of this study is to evaluate whether vaccines against SARS-CoV-2 induce systemic or cerebrospinal fluid alterations in patients with neurological disorders. METHODS: Patients who underwent lumbar puncture (LP) between February 2021 and October 2022 were enrolled. Serum C-reactive protein (CRP), neutrophil to lymphocyte ratio (NLR), cerebrospinal fluid total protein content (CSF-TPc), glucose CSF/serum ratio, number of CSF cells per cubic millimeter, and CSF neurofilament light chain (CSF-NfL) were compared between unvaccinated and vaccinated patients. RESULTS: A total of 110 patients were included and fitted into three groups according firstly to vaccination status (vaccinated and unvaccinated) and then to time from last dose of vaccine to LP (within or after 3 months). TPc, CSF/SGlu ratio, number of cells per cubic millimeter, CSF-NfL, CRP, and NLR were not different between groups (all p > 0.05), and also, they did not differ neither according to age nor diagnosis. No relevant differences between groups were also noticed when the at-risk time window was set to 6 weeks. INTERPRETATION: No signs of neuroinflammation, axonal loss and systemic inflammation were found in patients with neurological disorders after anti-SARS-CoV-2 vaccination compared with unvaccinated ones.

Biomarkers Related to Synaptic Dysfunction to Discriminate Alzheimer's Disease from Other Neurological Disorders.

Recently, the synaptic proteins neurogranin (Ng) and α-synuclein (α-Syn) have attracted scientific interest as potential biomarkers for synaptic dysfunction in neurodegenerative diseases. In this study, we measured the CSF Ng and α-Syn concentrations in patients affected by AD (n = 69), non-AD neurodegenerative disorders (n-AD = 50) and non-degenerative disorders (n-ND, n = 98). The concentrations of CSF Ng and α-Syn were significantly higher in AD than in n-AD and n-ND. Moreover, the Aß42/Ng and Aß42/α-Syn ratios showed statistically significant differences between groups and discriminated AD patients from n-AD patients, better than Ng or α-Syn alone. Regression analyses showed an association of higher Ng concentrations with MMSE < 24, pathological Aß 42/40 ratios, pTau, tTau and the ApoEε4 genotype. Aß 42/Ng was associated with MMSE < 24, an AD-related FDG-PET pattern, the ApoEε4 genotype, pathological Aß 42 levels and Aß 42/40 ratios, pTau, and tTau. Moreover, APO-Eε4 carriers showed higher Ng concentrations than non-carriers. Our results support the idea that the Aß 42/Ng ratio is a reliable index of synaptic dysfunction/degeneration able to discriminate AD from other neurological conditions.

Modulating Long Term Memory at Late-Encoding Phase: An rTMS Study.

Despite a huge effort of the scientific community, the functioning of Long-Term Memory (LTM) processes is still debated and far from being elucidated. Functional and neurophysiological data point to an involvement of Dorsolateral Prefrontal Cortex (DLPFC) in both encoding and retrieval phases. However, the recently proposed Explicit/Implicit Memory Encoding and Retrieval (EIMER) model proposes that LTM at the encoding phase consists of anatomically and chronologically different sub-phases. On this basis, we aimed to investigate the role of right DLPFC during a late-encoding phase by means of low-frequency rTMS. Thirty right-handed healthy subjects were divided into three experimental groups. Inhibitory rTMS was applied over right-DLPFC immediately after the encoding phase (Late-Encoding Group) or before recognition phase (Pre-Recognition Group), 24 h after, of an LTM task. Both groups also received sham stimulation during the non-target phase, while the third group (Sham Group) received only sham stimulation in both phases. The Late-Encoding Group collected a lower number of correct responses compared with Sham Group (p = 0.00), while Pre-Retrieval Group increased accuracy as compared to the Sham Group (p = 0.0). rTMS-inhibition of the right DLPFC seems able to interfere with LTM memory performances when delivered at a late stage of the encoding phase, with opposite effects at the pre-retrieval phase.

Prognostic Role of CSF ß-amyloid 1-42/1-40 Ratio in Patients Affected by Amyotrophic Lateral Sclerosis.

The involvement of ß-amyloid (Aß) in the pathogenesis of amyotrophic lateral sclerosis (ALS) has been widely discussed and its role in the disease is still a matter of debate. Aß accumulates in the cortex and the anterior horn neurons of ALS patients and seems to affect their survival. To clarify the role of cerebrospinal fluid (CSF) Aß 1-42 and Aß 42/40 ratios as a potential prognostic biomarker for ALS, we performed a retrospective observational study on a cohort of ALS patients who underwent a lumbar puncture at the time of the diagnosis. CSF Aß 1-40 and Aß 1-42 ratios were detected by chemiluminescence immunoassay and their values were correlated with clinical features. We found a significant correlation of the Aß 42/40 ratio with age at onset and Mini Mental State Examination (MMSE) scores. No significant correlation of Aß 1-42 or Aß 42/40 ratios to the rate of progression of the disease were found. Furthermore, when we stratified patients according to Aß 1-42 concentration and the Aß 42/40 ratio, we found that patients with a lower Aß 42/40 ratio showed a shorter survival. Our results support the hypothesis that Aß 1-42 could be involved in some pathogenic mechanism of ALS and we suggest the Aß 42/40 ratio as a potential prognostic biomarker.