Liquid Biopsy in Alzheimer's Disease Patients Reveals Epigenetic Changes in the PRLHR Gene.

In recent years, new DNA methylation variants have been reported in genes biologically relevant to Alzheimer's disease (AD) in human brain tissue. However, this AD-specific epigenetic information remains brain-locked and unreachable during patients' lifetimes. In a previous methylome performed in the hippocampus of 26 AD patients and 12 controls, we found higher methylation levels in AD patients in the promoter region of PRLHR, a gene involved in energy balance regulation. Our aim was to further characterize PRLHR's role in AD and to evaluate if the liquid biopsy technique would provide life access to this brain information in a non-invasive way. First, we extended the methylation mapping of PRLHR and validated previous methylome results via bisulfite cloning sequencing. Next, we observed a positive correlation between PRLHR methylation levels and AD-related neuropathological changes and a decreased expression of PRLHR in AD hippocampus. Then, we managed to replicate the hippocampal methylation differences in plasma cfDNA from an additional cohort of 35 AD patients and 35 controls. The isolation of cfDNA from the plasma of AD patients may constitute a source of potential epigenetic biomarkers to aid AD clinical management.

Association of Blood-Based DNA Methylation Markers With Late-Onset Alzheimer Disease: A Potential Diagnostic Approach.

BACKGROUND AND OBJECTIVES: There is an urgent need to identify novel noninvasive biomarkers for Alzheimer disease (AD) diagnosis. Recent advances in blood-based measurements of phosphorylated tau (pTau) species are promising but still insufficient to address clinical needs. Epigenetics has been shown to be helpful to better understand AD pathogenesis. Epigenetic biomarkers have been successfully implemented in other medical disciplines, such as oncology. The objective of this study was to explore the diagnostic accuracy of a blood-based DNA methylation marker panel as a noninvasive tool to identify patients with late-onset Alzheimer compared with age-matched controls. METHODS: A case-control study was performed. Blood DNA methylation levels at 46 cytosine-guanine sites (21 genes selected after a comprehensive literature search) were measured by bisulfite pyrosequencing in patients with "probable AD dementia" following National Institute on Aging and the Alzheimer's Association guidelines (2011) and age-matched and sex-matched controls recruited at Neurology Department-University Hospital of Navarre, Spain, selected by convenience sampling. Plasma pTau181 levels were determined by Simoa technology. Multivariable logistic regression analysis was performed to explore the optimal model to discriminate patients with AD from controls. Furthermore, we performed a stratified analysis by sex. RESULTS: The final study cohort consisted of 80 patients with AD (age: median [interquartile range] 79 [11] years; 58.8% female) and 100 cognitively healthy controls (age 77 [10] years; 58% female). A panel including DNA methylation levels at NXN, ABCA7, and HOXA3 genes and plasma pTau181 significantly improved (area under the receiver operating characteristic curve 0.93, 95% CI 0.89-0.97) the diagnostic performance of a single pTau181-based model, adjusted for age, sex, and APOE ɛ4 genotype. The sensitivity and specificity of this panel were 83.30% and 90.00%, respectively. After sex-stratified analysis, HOXA3 DNA methylation levels showed consistent association with AD. DISCUSSION: These results highlight the potential translational value of blood-based DNA methylation biomarkers for noninvasive diagnosis of AD. REGISTRATION INFORMATION: Research Ethics Committee of the University Hospital of Navarre (PI17/02218).

PLA2G4E, a candidate gene for resilience in Alzheimer´s disease and a new target for dementia treatment.

Clinical studies revealed that some aged-individuals accumulate a significant number of histopathological Alzheimer´s disease (AD) lesions in their brain, yet without developing any signs of dementia. Animal models of AD represent suitable tools to identify genes that might promote cognitive resilience and hence, this study first set out to identify cognitively resilient individuals in the aged-Tg2576 mouse model. A transcriptomic analysis of these mice identified PLA2G4E as a gene that might confer resistance to dementia. Indeed, a significant decrease in PLA2G4E is evident in the brain of late-stage AD patients, whereas no such changes are observed in early stage patients with AD neuropathological lesions but no signs of dementia. We demonstrated that adeno-associated viral vector-mediated overexpression of PLA2G4E in hippocampal neurons completely restored cognitive deficits in elderly APP/PS1 mice, without affecting the amyloid or tau pathology. These PLA2G4E overexpressing APP/PS1 mice developed significantly more dendritic spines than sham-injected mice, coinciding with the cognitive improvement observed. Hence, these results support the idea that a loss of PLA2G4E might play a key role in the onset of dementia in AD, highlighting the potential of PLA2G4E overexpression as a novel therapeutic strategy to manage AD and other disorders that course with memory deficits.

Evaluation of Chitotriosidase and CC-Chemokine Ligand 18 as Biomarkers of Microglia Activation in Amyotrophic Lateral Sclerosis.

BACKGROUND: The development of biomarkers for use in diagnosing, monitoring disease progression and analyzing therapeutic trials response in amyotrophic lateral sclerosis (ALS) is essential. OBJECTIVE: The aim of this study was to identify inflammatory factors in plasma or cerebrospinal fluid (CSF) from patients with ALS with particular attention to specific markers of microglia activation as chitotriosidase (ChT) and chemokine (C-C motif) ligand 18 (CCL18) to determine its potential as ALS biomarkers. METHODS: We studied CSF and plasma samples from 32 patients and 42 healthy controls. We assayed the ChT activity by a spectrofluorometric method and protein levels of other inflammatory -biomarkers (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6 and CCL18) by enzyme-linked immunosorbent assay. CHIT1 gene polymorphism in exon 10 (c.1049_1072dup24) encoding inactive ChT enzyme was genotyped in all subjects. RESULTS: ChT activity and TNF-alpha protein levels were significantly higher in CSF of ALS patients, but we found no correlation with the severity and progression of the disease. Nevertheless, we did not found any differences in CCL18 or IL-6 protein levels between both groups in CSF or plasma. In our sample, only 3% of subjects were homozygous carriers for the CHIT1 exon 10 duplication associated with defective enzyme. CONCLUSIONS: High ChT activity in CSF of patients with ALS may reflect microglia activation and could be a potential biomarker of the disease. We did not find any significant difference regarding CCL-18, another specific marker of microglia activation that is related with M2-like microglia phenotype. Deepening the understanding of the activation state of microglia (M1 and M2) may contribute to the knowledge about the specific role of neuroinflammation in ALS and future therapeutic strategies.

Liquid biopsy: a new source of candidate biomarkers in amyotrophic lateral sclerosis.

Noninvasive tests to diagnose and monitor the progression of neurodegenerative disorders have been a challenge for decades. The aim of this study was to explore the feasibility of applying liquid biopsy procedures to patients with a neurodegenerative disease such as amyotrophic lateral sclerosis (ALS). We isolated plasma cell-free DNA (cfDNA) in 20 ALS patients and 20 controls and used cfDNA to identify a novel differentially methylated mark in RHBDF2 gene in ALS patients compared to controls. Our findings support the notion that liquid biopsy may be applied to living patients as a source of potential epigenetic biomarkers for neurodegenerative disorders.