The implication of BDNF Val66Met polymorphism in progression from subjective cognitive decline to mild cognitive impairment and Alzheimer's disease: a 9-year follow-up study.

Brain-derived natriuretic factor (BDNF) Val66Met polymorphism has been frequently reported to be associated with Alzheimer's disease (AD) with contrasting results. Numerous studies showed that Met allele increased the risk of AD only in women, while other studies have found worse cognitive performance in Val/Val carriers. We aimed to inquire the effects of Val66Met polymorphism on the progression from subjective cognitive decline (SCD) to mild cognitive impairment (MCI) and from MCI to AD and to ascertain if this effect is modulated by demographic and cognitive variables. For this purpose, we followed up 74 subjects (48 SCD, 26 MCI) for a mean time of 9 years. All participants underwent extensive neuropsychological assessment, cognitive reserve estimation, BDNF and apolipoprotein E (ApoE) genotype analysis at baseline. Personality traits and leisure activities were assessed in a subgroup. Each patient underwent clinical-neuropsychological follow-up, during which 18 out of 48 SCD subjects progressed to MCI and 14 out of 26 MCI subjects progressed to AD. We found that Val66Met increased the risk of progression from SCD to MCI and from MCI to AD only in women. Nevertheless, Val/Val carriers who progressed from SCD to MCI had a shorter conversion time compared to Met carriers. We concluded that Val66Met polymorphism might play different roles depending on sex and stage of the disease.

Tumor Necrosis Factor α Influences Phenotypic Plasticity and Promotes Epigenetic Changes in Human Basal Forebrain Cholinergic Neuroblasts.

TNFα is the main proinflammatory cytokine implicated in the pathogenesis of neurodegenerative disorders, but it also modulates physiological functions in both the developing and adult brain. In this study, we investigated a potential direct role of TNFα in determining phenotypic changes of a recently established cellular model of human basal forebrain cholinergic neuroblasts isolated from the nucleus basalis of Meynert (hfNBMs). Exposing hfNBMs to TNFα reduced the expression of immature markers, such as nestin and ß-tubulin III, and inhibited primary cilium formation. On the contrary, TNFα increased the expression of TNFα receptor TNFR2 and the mature neuron marker MAP2, also promoting neurite elongation. Moreover, TNFα affected nerve growth factor receptor expression. We also found that TNFα induced the expression of DNA-methylation enzymes and, accordingly, downregulated genes involved in neuronal development through epigenetic mechanisms, as demonstrated by methylome analysis. In summary, TNFα showed a dual role on hfNBMs phenotypic plasticity, exerting a negative influence on neurogenesis despite a positive effect on differentiation, through mechanisms that remain to be elucidated. Our results help to clarify the complexity of TNFα effects in human neurons and suggest that manipulation of TNFα signaling could provide a potential therapeutic approach against neurodegenerative disorders.

Primary Progressive Aphasia: Natural History in an Italian Cohort.

BACKGROUND/AIMS: Few longitudinal studies have explored the progression of cognitive and functional impairment of patients with primary progressive aphasia (PPA). The aims of the study were to describe the clinical, neuroimaging, and genetic features of a cohort of 68 PPA patients, and to outline the natural history of the disease. MATERIALS AND METHODS: A sample of 23 patients with the logopenic variant, 26 with the nonfluent/agrammatic variant, and 19 with the semantic variant was retrospectively collected and followed-up for a maximum of 6 years. Clinical-neuropsychological assessment, fluorodeoxyglucose positron emission tomographic imaging, and genetic analyses were acquired at baseline. Disease progression was evaluated in terms of language impairment, global cognitive decline, and functional dependency. RESULTS: During follow-up, one third of subjects presented total language loss, and 20% severe functional dependency. Global cognitive decline after the first year (hazard ratio, 5.93; confidence interval, 1.63-21.56) and high schooling (hazard ratio, 0.07; confidence interval, 0.008-0.74) represented risk factors for functional impairment. The apolipoprotein E status was associated with the progression of cognitive decline. Positive family history for dementia was frequent and 3 genetic autosomal dominant mutations were identified. CONCLUSIONS: There were no differences in the progression of PPA subtypes. Genetics plays an important role in disease onset and progression.

Biomarkers study in atypical dementia: proof of a diagnostic work-up.

BACKGROUND: An early differentiation between Alzheimer's Disease (AD) and other dementias is crucial for an adequate patients' management, albeit it may result difficult for the occurrence of "atypical presentations." Current diagnostic criteria recognize the importance of biomarkers for AD diagnosis, but still an optimal diagnostic work-up isn't available. OBJECTIVE: Evaluate the utility and reproducibility of biomarkers and propose an "optimal" diagnostic work-up in atypical dementia. METHODS: (1) a retrospective selection of "atypical dementia cases"; (2) a repetition of diagnostic assessment by two neurologists following two different diagnostic work-ups, each consisting of multiple steps; (3) a comparison between diagnostic accuracy and confidence reached at each step by both neurologists and evaluation of the inter-rater agreement. RESULTS: In AD, regardless of the undertaken diagnostic work-up, a significant gain in accuracy was reached by both neurologists after the second step, whereas in frontotemporal dementia (FTD), adding subsequent steps was not always sufficient to increase significantly the baseline accuracy. A relevant increment in diagnostic confidence was detectable after studying pathophysiological markers in AD, and after assessing brain metabolism in FTD. The inter-rater agreement was higher at the second step for the AD group when the pathophysiological markers were available and for the FTD group when the results of FDG-PET were accessible. CONCLUSIONS: In atypical cases of dementia, biomarkers significantly raise diagnostic accuracy, confidence, and agreement. This study introduces a proof of diagnostic work-up that combines imaging and CSF biomarkers and suggests distinct ways to proceed on the basis of a greater diagnostic likelihood.

Imaging and cognitive reserve studies predict dementia in presymptomatic Alzheimer's disease subjects.

There is strong evidence that Alzheimer's disease (AD) pathology starts decades before clinical onset. Cognitive reserve (CR) and brain reserve can be a good predictive model for AD development. Neuroimaging can help in describing cerebral reserves, as well as in detecting AD brain pathology before the onset of clinical dementia. Education and occupation act as proxies for CR and are associated with a lower risk of AD and delayed onset of symptoms. The apolipoprotein E (ApoE)-ε4 allele is a strong risk factor for AD and is associated with lower hippocampal volume even in normal aging. A fluorodeoxyglucose positron emission tomography study of brain metabolism shows different metabolic phenotypes among subjects with different educational levels and ApoE genotypes. More highly educated subjects reach a clinical level when the cerebral areas involved in coping with network disruption are seriously impaired, and the AD-ε4 carriers show more global metabolic brain impairment compared with non-ε4 carriers. Thus, CR can counteract a genetically unfavorable background, suggesting a possible preventive strategy. AD research findings have already produced results, since recent epidemiological studies report a decreasing incidence of AD in the last years.

Ataxia-telangiectasia mutated (ATM) genetic variant in Italian centenarians.

Lifespan is attributable to genetic factors and some studies have attempted to identify putative genes implicated in human longevity. Several genetic loci have been associated with longevity, but some of these are not replicable, probably due to the vast differences among ethnicities. We analyzed in 128 Italian long-lived individuals and 150 unrelated healthy subjects, the recently reported association between rs189037 in the ataxia-telangiectasia mutated gene promoter and longevity in Chinese nonagenarians/centenarians. Our study confirms the association between the rs189037 C/T genotype and longevity in Italian centenarians, with an odds ratio of 1.85 (95 % CI 0.99-3.45). To understand the genetic basis for longevity is an extraordinarily difficult task, and therefore it is important to replicate any positive findings, especially if detected in other ethnic groups, in order to reach reliable conclusions on the real effect that candidate genes have on longevity.

TOMM40 polymorphisms in Italian Alzheimer's disease and frontotemporal dementia patients.

Chromosome 19 is one of the several prominent chromosomes related to the risk of developing late-onset Alzheimer's disease (LOAD) and frontotemporal lobar degeneration (FTLD). However, only Apolipoprotein E (APOE) has been confirmed as a risk factor for both disorders. The aim of this study was to investigate a set of polymorphisms in the translocase of the outer mitochondrial membrane 40 (TOMM40) gene, located in close proximity to APOE, to clarify if the TOMM40 gene may be considered a risk factor for AD and FTLD, independently of APOE status. We performed a case-control study in a dataset of Italian LOAD and FTLD patients, analyzing the following three single-nucleotide polymorphisms (SNPs): rs157580, rs2075650 and rs157581. The analysis was made in 710 Italian subjects: 282 LOAD patients, 156 FTLD patients and 272 healthy subjects. Our results confirm the presence of an association between TOMM40 SNPs and LOAD in our Italian population, suggesting that genetic variations proximate to APOE contributes to the LOAD risk. Genotype and allele distribution of the TOMM40 polymorphisms between the FTLD group and controls did not show any statistical difference. When we analyzed haplotype distribution of the SNPs, taking into account the presence of the APOE allele, we observed a strong association between the ε4 allele and the GAC haplotype both in LOAD and FTLD patients. In contrast, this association did not hold for ε3/GAC. These results demonstrate that the TOMM40 gene does not have an APOE-independent role in the risk of developing LOAD and FTLD.

Progranulin genetic screening in frontotemporal lobar degeneration patients from central Italy.

Recently, mutations in the progranulin gene (GRN) were reported to account for the vast majority of Frontotemporal lobar Degeneration (FTLD) and a growing number of reports describe the implication of this gene in the development of the FTLD pathology with a significant variation in clinical features. To better clarify the contribution of GRN mutations to Italian FTLD, we screened 381 subjects: 171 cases and 210 healthy subjects, all from Central Italy, particularly of Tuscan origins. GRN gene was analyzed using High Resolution Melting Analysis and automated Genetic Analyzer. Human Progranulin ELISA Kit was employed to determine the plasma progranulin levels. The screening showed a total of six genetic variants in the GRN gene: 3 pathogenic and 3 non pathogenic in 13 out of 171 patients. The rare intronic variant IVS2 +7 G > A was found in one patient. The pathogenetic mutation, p.T272SfsX10, is confirmed as the most common GRN mutation in Italian FTLD patients with a frequency in our study of 2.32%. Moreover, we identified the first Italian patient with the p.R493X mutation, to date described in 43 families worldwide. Our data report, for the first time, the occurrence of GRN mutations in Tuscany, Central Italy, confirming that genetic variations in this gene could be a considerable genetic cause of FTLD and that genetic screening might be useful both in familial and sporadic FTLD patients.

Genetic variation in APOE, GRN, and TP53 are phenotype modifiers in frontotemporal dementia.

Frontotemporal dementia (FTD) is a clinical, genetic, and pathologic heterogeneous group of neurodegenerative diseases. In this study, we investigated the role of APOƐ4, rs5848 in GRN, and rs1042522 in TP53 gene as disease risk factors and/or phenotype modifiers in 440 FTD patients, including 175 C9orf72 expansion carriers. We found that the C9orf72 expansion carriers showing an earlier age at onset (p < 0.001). Among the clinical groups, the FTD-MND (motoneuron disease) showed the lowest survival (hazard ratio [HR] = 4.12), and the progressive nonfluent aphasia group showed the highest onset age (p = 0.03). In our cohort, the rs1042522 in TP53 was associated with disease onset (p = 0.02) and survival (HR = 1.73) and rs5848 GRN with a significantly shorter survival in CC homozygous patients (HR = 1.98). The frequency of APOƐ4 carriers was significantly increased in the C9orf72 noncarriers (p = 0.022). Although validation of our findings is necessary, our results suggest that TP53, GRN, and APOE genes may act as phenotype modifiers in FTD and should be considered in future clinical trials.

Challenges in Alzheimer's Disease Diagnostic Work-Up: Amyloid Biomarker Incongruences.

BACKGROUND: Discordance among amyloid biomarkers is a challenge to overcome in order to increase diagnostic accuracy in dementia. OBJECTIVES: 1) To verify that cerebrospinal fluid (CSF) Aß42/Aß40 ratio (AßR) better agrees with Amyloid PET (Amy-PET) results compared to CSF Aß42; 2) to detect differences among concordant positive, concordant negative, and discordant cases, basing the concordance definition on the agreement between CSF AßR and Amy-PET results; 3) to define the suspected underlying pathology of discordant cases using in vivo biomarkers. METHOD: We retrospectively enrolled 39 cognitively impaired participants in which neuropsychological tests, apolipoprotein E genotype determination, TC/MRI, FDG-PET, Amy-PET, and CSF analysis had been performed. In all cases, CSF analysis was repeated using the automated Lumipulse method. In discordant cases, FDG-PET scans were evaluated visually and using automated classifiers. RESULTS: CSF AßR better agreed with Amy-PET compared to CSF Aß42 (Cohen's K 0.431 versus 0.05). Comparisons among groups did not show any difference in clinical characteristics except for age at symptoms onset that was higher in the 6 discordant cases with abnormal CSF AßR values and negative Amy-PET (CSF AßR+/AmyPET-). FDG-PET and all CSF markers (Aß42, AßR, p-Tau, t-Tau) were suggestive of Alzheimer's disease (AD) in 5 of these 6 cases. CONCLUSION: 1) CSF AßR is the CSF amyloid marker that shows the better level of agreement with Amy-PET results; 2) The use of FDG-PET and CSF-Tau markers in CSFAßR+/Amy-PET-discordant cases can support AD diagnosis; 3) Disagreement between positive CSF AßR and negative Amy-PET in symptomatic aged AD patients could be due to the variability in plaques conformation and a negative Amy-PET scan cannot be always sufficient to rule out AD.

Linguistic profiles, brain metabolic patterns and rates of amyloid-ß biomarker positivity in patients with mixed primary progressive aphasia.

We aimed to detail language profiles, brain metabolic patterns and proportion of Alzheimer's disease biomarkers in a cohort of patients with mixed primary progressive aphasia (mPPA). We considered 58 patients with PPA: 10 with non-fluent/agrammatic variant (nfvPPA), 16 with semantic variant (svPPA), 21 with logopenic variant (lvPPA) and 9 with mPPA. Patients with mPPA were further classified as 4 nf/lvPPA (with prevailing features for nfvPPA and lvPPA) and 5 s/lvPPA (with prevailing features for svPPA and lvPPA). Nf/lvPPA patients were characterized by higher proportion of Naming impairment compared to nfvPPA and more frequent Grammatical Errors and Phonologic Errors than lvPPA. S/lvPPA had higher proportion of impairment in Sentences Repetition compared to svPPA and in Single-word Comprehension compared to lvPPA. 100% of nf/lvPPA and 40% of s/lvPPA had Aß positive biomarkers. Brain hypometabolic pattern in Nf/lvPPA was consistent with lvPPA, while s/lvPPA had a brain metabolism resembling svPPA. We concluded that nf/lvPPA patients might be considered as PPA variant due to Alzheimer's disease and s/lvPPA group mainly included patients with svPPA.

Influence of ApoE Genotype and Clock T3111C Interaction with Cardiovascular Risk Factors on the Progression to Alzheimer's Disease in Subjective Cognitive Decline and Mild Cognitive Impairment Patients.

BACKGROUND: Some genes could interact with cardiovascular risk factors in the development of Alzheimer's disease. We aimed to evaluate the interaction between ApoE ε4 status, Clock T3111C and Per2 C111G polymorphisms with cardiovascular profile in Subjective Cognitive Decline (SCD) and Mild Cognitive Impairment (MCI). METHODS: We included 68 patients who underwent clinical evaluation; neuropsychological assessment; ApoE, Clock and Per2 genotyping at baseline; and neuropsychological follow-up every 12-24 months for a mean of 13 years. We considered subjects who developed AD and non-converters. RESULTS: Clock T3111C was detected in 47% of cases, Per2 C111G in 19% of cases. ApoE ε4 carriers presented higher risk of heart disease; Clock C-carriers were more frequently smokers than non C-carriers. During the follow-up, 17 patients progressed to AD. Age at baseline, ApoE ε 4 and dyslipidemia increased the risk of conversion to AD. ApoE ε4 carriers with history of dyslipidemia showed higher risk to convert to AD compared to ApoE ε4- groups and ApoE ε4+ without dyslipidemia patients. Clock C-carriers with history of blood hypertension had a higher risk of conversion to AD. CONCLUSIONS: ApoE and Clock T3111C seem to interact with cardiovascular risk factors in SCD and MCI patients influencing the progression to AD.

Role for ATXN1, ATXN2, and HTT intermediate repeats in frontotemporal dementia and Alzheimer's disease.

We analyzed the frequency of intermediate alleles (IAs) in the ATXN1, ATXN2, and HTT genes in several neurodegenerative diseases. The study included 1126 patients with Alzheimer's disease (AD), 440 patients with frontotemporal dementia (FTD), and 610 patients with Parkinson's disease. In all cohorts, we genotyped ATXN1 and ATXN2 CAG repeats. In addition, in the FTD cohort, we determined the number of HTT CAG repeats. The frequency of HTT IAs was higher in patients with FTD (6.9%) versus controls (2.9%) and in the C9orf72 expansion noncarriers (7.2%) versus controls (2.9%), although the difference was nonsignificant after correction for multiple testing. Compared with controls, progressive nonfluent aphasia (PNFA) groups showed a significantly higher frequency of HTT IAs (13.6% vs. 2.9% controls). For the ATXN2 gene, we observed an increase in IA frequency in AD cases (AD 4.1% vs. controls 1.8%) and in the behavioral FTD group (4.8% vs. 1.8%). For the ATXN1 gene, we found a significant increase of IAs in patients with PNFA (18.6%) versus controls (6.7%). In conclusion, our work suggests that the HTT and ATXN1 IAS may contribute to PNFA pathogenesis and point to a link between ATXN2 IAS and AD.

High Frequency of Crossed Aphasia in Dextral in an Italian Cohort of Patients with Logopenic Primary Progressive Aphasia.

BACKGROUND: Primary progressive aphasia (PPA) has been described as a neurodegenerative language disorder mainly affecting the left hemisphere. Few cases of right hemisphere damage in right-handed PPA subjects have been reported. This condition, named crossed aphasia in dextral (CAD), is relatively rare and probably related to an alteration during neurodevelopment of language networks. OBJECTIVE: To explore the prevalence of CAD in an Italian cohort of 68 PPA patients, in order to evaluate whether right hemisphere language lateralization could be a risk factor for PPA. METHODS: Clinical-demographic and cerebral [18F]-fluorodeoxyglucose positron emission tomography ([18F]FDG-PET) scan were analyzed, resulting in 23 logopenic variant (lvPPA) patients, 26 non-fluent variant (nfvPPA) patients, and 19 semantic variant (svPPA) patients. SPM single subject routine was performed for diagnostic purposes in order to identify the hypometabolic pattern of each patient. Based on brain metabolic profile, PPA patients were divided in right and left lvPPA, nfvPPA, and svPPA. [18F]FDG-PET group analyses were performed with SPM two-sample t-test routine. RESULTS: 26% of lvPPA cases were identified as CAD based on right hypometabolic pattern. CAD patients did not differ from left lvPPA regarding demographic features and general cognitive performance; however, they performed better in specific working memory tasks and showed brain hypometabolism limited to the superior, middle, and supramarginal temporal gyri. CONCLUSION: Atypical lateralization of language function could determine a vulnerability of the phonological language loop and in that way could be a risk factor for lvPPA.

Genetic Heterogeneity of Alzheimer's Disease: Embracing Research Partnerships.

Studies on the genetics of Alzheimer's disease (AD) have revealed the complexity and heterogeneity of the disease. All our studies have supported this evidence and contribute to the current understanding of the genetic architecture of AD. This report reviews the success of our investigations, focusing on the implications and importance of the genetics of AD, and demonstrates the relevance of research strategies embracing partnerships.

Novel GRN Mutations in Alzheimer's Disease and Frontotemporal Lobar Degeneration.

BACKGROUND: During the twentieth century, frontotemporal dementia (FTD) was often misdiagnosed, confused with Alzheimer's disease or psychiatric disorders, jeopardizing care and research. OBJECTIVE: To analyze the FTD genes in the DNA samples of patients belonging to families clinically classified as probable Alzheimer's disease (FAD) in the early 1990s and not carrying mutation in the three main genes linked to FAD (Presenilin 1, Presenilin 2, and Amyloid precursor protein). METHODS: The genetic screening was performed on 63 probands diagnosed as FAD before the early 2000s. RESULTS: Four patients out of the 63 studied (4/63, 6.3%) resulted as carrying four different GRN genetic variations: p.T272SfsX10, p.R110X, p.C149LfsX10, and p.W304C. The first two mutations (p.T272SfsX10, p.R110X) are the most frequent ones in Italy in FTD patients; the latter two (p.C149LfsX10 and p.W304C) are not described in the scientific literature. CONCLUSION: Our data suggest that it can be important to re-examine FAD patients diagnosed when the FTD spectrum was not well recognized and the causative FTD genes had not yet been identified. Moreover, we propose initially analyzing genes associated with the first form of suspected dementia and, if the results are negative, studying genes implicated in the other form of dementia.

Alzheimer's Disease Progression: Factors Influencing Cognitive Decline.

BACKGROUND: Alzheimer's disease (AD) patients present high variability in the rate of cognitive decline. Despite the wide knowledge on factors influencing dementia risk, little is known on what accounts for AD progression. Previous studies on this topic have mainly analyzed each factor separately without taking into account the interaction between genetic and non-genetic factors. OBJECTIVE: The aim of the present study is to evaluate the role of demographic, clinical, therapeutic, and genetic factors and their interaction on cognitive decline among newly diagnosed AD patients. METHODS: We retrospectively selected 160 AD patients diagnosed at the Neurology Unit of Careggi University Hospital of Florence. We evaluated the occurrence of rapid cognitive changes defined as the worsening of more than four points at the Mini-Mental State Examination after 2-year follow up period. RESULTS: Among the 160 AD patients, 50% presented rapid disease progression. Extrapyramidal signs at disease onset were predictors of worse outcome (OR 2.2), especially among Apolipoprotein E (APOE) ɛ4 allele carriers, while the presence of family history for dementia decreased the risk of rapid progression by about 50%. Higher educated ɛ4-carriers showed a slower AD progression. We identified the chronic use of aspirin as potential secondary preventative strategy for the non ɛ4-carriers. CONCLUSION: At dementia onset, some clinical and demographic data can be predictors of future progression. The outcomes of the present study support the already hypothesized interaction between genetic and non-genetic factors during disease course and suggest genetic-based approaches.

Association of the New Variant Tyr424Asp at TBK1 Gene with Amyotrophic Lateral Sclerosis and Cognitive Decline.

A new risk gene associated with amyotrophic lateral sclerosis (ALS) has recently been identified: the Tank-binding kinase 1 (TBK1) gene. Up to now, 90 TBK1 variants have been described in ALS patients with or without frontotemporal dementia (FTD), thus making TBK1 the third or fourth most frequent genetic cause of ALS and FTD. A point mutation analysis in a cohort of 69 Italian ALS patients was performed in order to analyze the frequency of TBK1 mutations and the correlation with clinical phenotypes. The analysis identified the novel variant p.Tyr424Asp in a patient with a rapid progression of the disease. Our data supports the implication of TBK1 in ALS pathogenesis in Italy.

Low Florbetapir PET Uptake and Normal Aß1-42 Cerebrospinal Fluid in an APP Ala713Thr Mutation Carrier.

According to the literature, the APP Ala713Thr mutation is associated with Alzheimer's disease and cerebral amyloid angiopathy. We describe a case of dementia clinically compatible with frontotemporal dementia in an APP Ala713Thr mutation carrier in which both [18F]Florbetapir PET uptake and Aß1-42 cerebrospinal fluid levels were normal. Further evidences are required to establish if this association is only incidental.