Plasma neurofilament light chain predicts Alzheimer's disease in patients with subjective cognitive decline and mild cognitive impairment: A cross-sectional and longitudinal study.

BACKGROUND AND PURPOSE: We aimed to evaluate the accuracy of plasma neurofilament light chain (NfL) in predicting Alzheimer's disease (AD) and the progression of cognitive decline in patients with subjective cognitive decline (SCD) and mild cognitive impairment (MCI). METHODS: This longitudinal cohort study involved 140 patients (45 with SCD, 73 with MCI, and 22 with AD dementia [AD-D]) who underwent plasma NfL and AD biomarker assessments (cerebrospinal fluid, amyloid positron emission tomography [PET], and 18 F-fluorodeoxyglucose-PET) at baseline. The patients were rated according to the amyloid/tau/neurodegeneration (A/T/N) system and followed up for a mean time of 2.72 ± 0.95 years to detect progression from SCD to MCI and from MCI to AD. Forty-eight patients (19 SCD, 29 MCI) also underwent plasma NfL measurements 2 years after baseline. RESULTS: At baseline, plasma NfL detected patients with biomarker profiles consistent with AD (A+/T+/N+ or A+/T+/N-) with high accuracy (area under the curve [AUC] 0.82). We identified cut-off values of 19.45 pg/mL for SCD and 20.45 pg/mL for MCI. During follow-up, nine SCD patients progressed to MCI (progressive SCD [p-SCD]), and 14 MCI patients developed AD dementia (progressive MCI [p-MCI]). The previously identified cut-off values provided good accuracy in identifying p-SCD (80% [95% confidence interval 65.69: 94.31]). The rate of NfL change was higher in p-MCI (3.52 ± 4.06 pg/mL) compared to non-progressive SCD (0.81 ± 1.25 pg/mL) and non-progressive MCI (-0.13 ± 3.24 pg/mL) patients. A rate of change lower than 1.64 pg/mL per year accurately excluded progression from MCI to AD (AUC 0.954). CONCLUSION: Plasma NfL concentration and change over time may be a reliable, non-invasive tool to detect AD and the progression of cognitive decline at the earliest stages of the disease.

Parkinson-ALS with a novel MAPT variant.

The mutations on microtubule associated protein tau (MAPT) gene manifest clinically with behavioural frontotemporal dementia (FTD), parkinsonism, such as progressive supranuclear palsy and corticobasal degeneration, and rarely with amyotrophic lateral sclerosis (ALS). FTD-parkinsonism and FTD-ALS are clinical overlaps included in the spectrum of MAPT mutation's phenotypes. The mutations on MAPT gene cause the dysfunction of tau protein determining its accumulation in neurofibrillary tangles. Recent data describe frequently the co-occurrence of the aggregation of tau protein and α-synuclein in patients with parkinsonism and Parkinson disease (PD), suggesting an interaction of the two proteins in determining neurodegenerative process. The sporadic description of PD-ALS clinical complex, known as Brait-Fahn-Schwarz disease, supports the hypothesis of common neuropathological pathways between different disorders. Here we report the case of a 54-year-old Italian woman with idiopathic PD later complicated by ALS carrying a novel MAPT variant (Pro494Leu). The variant is characterized by an amino acid substitution and is classified as damaging for MAPT functions. The case supports the hypothesis of tau dysfunction as the basis of multiple neurodegenerative disorders.

Understanding the interplay between APO E polymorphism and cognition in the Italian oldest old: results from the "Mugello study".

INTRODUCTION: Recent data suggest that the deleterious effect on general health and cognition of ε4 allele of Apolipoprotein E (ApoE) observed in the elderly population, may attenuate in extreme aging. This study aimed to describe the ApoE genotype distribution and its relationship with cognition in a group of nonagenarians living in the Mugello area, Italy. MATERIAL AND METHODS: Cognition was evaluated using the Mini-Mental-State-Examination (MMSE). DNA was extracted from blood samples to determine ApoE genotyping. Participants were classified into three ApoE groups (ε2, ε3, ε4). Logistic and linear regression models were created, to assess the relationship between ApoE genotype group and dementia diagnosis and cognitive performance, respectively. RESULTS: 169 subjects were included. ApoE ε3 was the most prevalent genotype (76.3%). Dementia prevalence was 26.6% and it was not associated with the presence of ApoE ε4. Participants of ε4 group were significantly more likely to have lower cognitive performances than ε2 and ε3, independently of a dementia diagnosis. DISCUSSION: Results support that ApoE genotype no longer plays a role in the health condition of the oldest old, however, an interaction is detectable between ApoE polymorphism and cognitive performances at this extreme age.

The role of plasma neurofilament light chain and glial fibrillary acidic protein in subjective cognitive decline and mild cognitive impairment.

INTRODUCTION AND AIM: NfL and GFAP are promising blood-based biomarkers for Alzheimer's disease. However, few studies have explored plasma GFAP in the prodromal and preclinical stages of AD. In our cross-sectional study, our aim is to investigate the role of these biomarkers in the earliest stages of AD. MATERIALS AND METHODS: We enrolled 40 patients (11 SCD, 21 MCI, 8 AD dementia). All patients underwent neurological and neuropsychological examinations, analysis of CSF biomarkers (Aß42, Aß42/Aß40, p-tau, t-tau), Apolipoprotein E (APOE) genotype analysis and measurement of plasma GFAP and NfL concentrations. Patients were categorized according to the ATN system as follows: normal AD biomarkers (NB), carriers of non-Alzheimer's pathology (non-AD), prodromal AD, or AD with dementia (AD-D). RESULTS: GFAP was lower in NB compared to prodromal AD (p = 0.003, d = 1.463) and AD-D (p = 0.002, d = 1.695). NfL was lower in NB patients than in AD-D (p = 0.011, d = 1.474). NfL demonstrated fair accuracy (AUC = 0.718) in differentiating between NB and prodromal AD, with a cut-off value of 11.65 pg/mL. GFAP showed excellent accuracy in differentiating NB from prodromal AD (AUC = 0.901) with a cut-off level of 198.13 pg/mL. CONCLUSIONS: GFAP exhibited excellent accuracy in distinguishing patients with normal CSF biomarkers from those with prodromal AD. Our results support the use of this peripheral biomarker for detecting AD in patients with subjective and objective cognitive decline.

The Frequency of Intermediate Alleles in Patients with Cerebellar Phenotypes.

Cerebellar syndromes are clinically and etiologically heterogeneous and can be classified as hereditary, neurodegenerative non-hereditary, or acquired. Few data are available on the frequency of each form in the clinical setting. Growing interest is emerging regarding the genetic forms caused by triplet repeat expansions. Alleles with repeat expansion lower than the pathological threshold, termed intermediate alleles (IAs), have been found to be associated with disease manifestation. In order to assess the relevance of IAs as a cause of cerebellar syndromes, we enrolled 66 unrelated Italian ataxic patients and described the distribution of the different etiology of their syndromes and the frequency of IAs. Each patient underwent complete clinical, hematological, and neurophysiological assessments, neuroimaging evaluations, and genetic tests for autosomal dominant cerebellar ataxia (SCA) and fragile X-associated tremor/ataxia syndrome (FXTAS). We identified the following diagnostic categories: 28% sporadic adult-onset ataxia, 18% cerebellar variant of multiple system atrophy, 9% acquired forms, 9% genetic forms with full-range expansion, and 12% cases with intermediate-range expansion. The IAs were six in the FMR1 gene, two in the gene responsible for SCA8, and one in the ATXN2 gene. The clinical phenotype of patients carrying the IAs resembles, in most of the cases, the one associated with full-range expansion. Our study provides an exhaustive description of the causes of cerebellar ataxia, estimating for the first time the frequency of IAs in SCAs- and FXTAS-associated genes. The high percentage of cases with IAs supports further screening among patients with cerebellar syndromes.

Effect of BDNF Val66Met polymorphism on hippocampal subfields in multiple sclerosis patients.

Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism was shown to strongly affect BDNF function, but its role in modulating gray matter damage in multiple sclerosis (MS) patients is still not clear. Given BDNF relevance on the hippocampus, we aimed to explore BDNF Val66Met polymorphism effect on hippocampal subfield volumes and its role in cognitive functioning in MS patients. Using a 3T scanner, we obtained dual-echo and 3DT1-weighted sequences from 50 MS patients and 15 healthy controls (HC) consecutively enrolled. MS patients also underwent genotype analysis of BDNF, neurological and neuropsychological evaluation. Hippocampal subfields were segmented by using Freesurfer. The BDNF Val66Met polymorphism was found in 22 MS patients (44%). Compared to HC, MS patients had lower volume in: bilateral hippocampus-amygdala transition area (HATA); cornus ammonis (CA)1, granule cell layer of dentate gyrus (GCL-DG), CA4 and CA3 of the left hippocampal head; molecular layer (ML) of the left hippocampal body; presubiculum of right hippocampal body and right fimbria. Compared to BDNF Val66Val, Val66Met MS patients had higher volume in bilateral hippocampal tail; CA1, ML, CA3, CA4, and GCL-DG of left hippocampal head; CA1, ML, and CA3 of the left hippocampal body; left HATA and presubiculum of the right hippocampal head. In MS patients, higher lesion burden was associated with lower volume of presubiculum of right hippocampal body; lower volume of left hippocampal tail was associated with worse visuospatial memory performance; lower volume of left hippocampal head with worse performance in semantic fluency. Our findings suggest the BNDF Val66Met polymorphism may have a protective role in MS patients against both hippocampal atrophy and cognitive impairment. BDNF genotype might be a potential biomarker for predicting cognitive prognosis, and an interesting target to study for neuroprotective strategies.

PRedicting the EVolution of SubjectIvE Cognitive Decline to Alzheimer's Disease With machine learning: the PREVIEW study protocol.

BACKGROUND: As disease-modifying therapies (DMTs) for Alzheimer's disease (AD) are becoming a reality, there is an urgent need to select cost-effective tools that can accurately identify patients in the earliest stages of the disease. Subjective Cognitive Decline (SCD) is a condition in which individuals complain of cognitive decline with normal performances on neuropsychological evaluation. Many studies demonstrated a higher prevalence of Alzheimer's pathology in patients diagnosed with SCD as compared to the general population. Consequently, SCD was suggested as an early symptomatic phase of AD. We will describe the study protocol of a prospective cohort study (PREVIEW) that aim to identify features derived from easily accessible, cost-effective and non-invasive assessment to accurately detect SCD patients who will progress to AD dementia. METHODS: We will include patients who self-referred to our memory clinic and are diagnosed with SCD. Participants will undergo: clinical, neurologic and neuropsychological examination, estimation of cognitive reserve and depression, evaluation of personality traits, APOE and BDNF genotyping, electroencephalography and event-related potential recording, lumbar puncture for measurement of Aß42, t-tau, and p-tau concentration and Aß42/Aß40 ratio. Recruited patients will have follow-up neuropsychological examinations every two years. Collected data will be used to train a machine learning algorithm to define the risk of being carriers of AD and progress to dementia in patients with SCD. DISCUSSION: This is the first study to investigate the application of machine learning to predict AD in patients with SCD. Since all the features we will consider can be derived from non-invasive and easily accessible assessments, our expected results may provide evidence for defining cost-effective and globally scalable tools to estimate the risk of AD and address the needs of patients with memory complaints. In the era of DMTs, this will have crucial implications for the early identification of patients suitable for treatment in the initial stages of AD. TRIAL REGISTRATION NUMBER (TRN): NCT05569083.

Huntingtin gene intermediate alleles influence the progression from subjective cognitive decline to mild cognitive impairment: A 14-year follow-up study.

BACKGROUND AND PURPOSE: Huntingtin (HTT) is a gene containing a key region of CAG repeats. HTT alleles containing from 27 to 35 CAG repeats are termed intermediate alleles (IAs). We aimed to assess the effect of IAs on progression of cognitive impairment in patients with subjective cognitive decline (SCD). METHODS: We included 106 patients with SCD. All the patients underwent neuropsychological assessments and blood sample collection at baseline. Patients were followed up for a median (interquartile range) time of 13.75 (8.17) years. We genotyped APOE and HTT at the end of the follow-up. RESULTS: Eleven out of 106 patients (10.38%, 95% confidence interval [CI] 4.57-16.18) were carriers of IAs (IA+ ). During the follow-up, 44 patients (41.51%, 95% CI 32.13-50.89) progressed to mild cognitive impairment (MCI; p-SCD group), while 62 patients (58.49%, 95% CI 49.11-67.87) did not (np-SCD group). Rate of progression to MCI was associated with IAs, age at baseline, and APOE ɛ4. We dichotomized age at baseline (<60 years = younger patients [YP], >60 years = older patients [OP]) and then classified patients into four groups: YP/IA- , YP/IA+ , OP/IA-  and OP/IA+ . The OP/IA+  group had a higher proportion of patients with progression from SCD to MCI (85.71%, 95% CI 59.79-100) as compared to the YP/IA-  group (28.57%, 95% CI 13.60-43.54, χ2  = 15.25; p < 0.001) and the OP/IA-  group (45.00%, 95% CI 32.41-57.59, χ2  = 7.903; p = 0.005). We classified patients according to APOE and IA as: ɛ4- /IA- , ɛ4- /IA+ , ɛ4+ /IA- , ɛ4+ /IA+ . The proportion of patients with progression in the ɛ4+ /IA+  group (100%) was higher as compared to the ɛ4- /IA-  group (33.33%, 95% CI 21.96-44.71, χ2  = 14.43; p < 0.001) and ɛ4+ /IA-  (55.56%, 95% CI 36.81-74.30, χ2  = 4.60; p = 0.032). CONCLUSIONS: Intermediate alleles interact with age and APOE ɛ4, increasing the risk of progression to MCI in SCD patients.

Gender differences in cognitive reserve: implication for subjective cognitive decline in women.

BACKGROUND: Subjective Cognitive Decline (SCD) is a self-experienced decline in cognitive capacity with normal performance on standardized cognitive tests, showing to increase risk of Alzheimer's Disease (AD). Cognitive reserve seems to influence the progression from SCD to Mild Cognitive Impairment (MCI) and to AD. The aim of our study was to investigate gender differences in cognitive reserve evaluating how sex might modulate the role of cognitive reserve on SCD. METHODS: We included 381 SCD patients who underwent clinical evaluation, neuropsychological assessment, evaluation of premorbid intelligence by the Test di Intelligenza Breve (TIB), cognitive complaints by the Memory Assessment Clinics Questionnaire (MAC-Q), and apolipoprotein E (APOE) genotyping. RESULTS: The proportion between women and men was significantly different (68.7% [95% CI 63.9-73.4 vs 31.4%, 95% CI 26.6-36.0]). Women were younger than men at onset of SCD and at the baseline visit (p = 0.021), had lower years of education (p = 0.007), lower TIB scores (p < 0.001), and higher MAC-Q scores (p = 0.012). TIB was directly associated with age at onset of SCD in both women and men, while years of education was inversely associated with age at onset only in women. Multivariate analysis showed that sex influences TIB independently from years of education. TIB was directly associated with MAC-Q in men. CONCLUSIONS: Sex interacts with premorbid intelligence and education level in influencing the age at onset and the severity of SCD. As the effect of education was different between men and women, we speculated that education might act as a minor contributor of cognitive reserve in women.

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.

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.

KIBRA T allele influences memory performance and progression of cognitive decline: a 7-year follow-up study in subjective cognitive decline and mild cognitive impairment.

KIBRA is a signal transducer protein, mainly expressed in the kidney and brain. A single-nucleotide polymorphism (SNP rs17070145, T → C exchange) has been linked to different cognitive function. In 2008, we studied 70 subjects who complained of subjective cognitive decline (SCD) and found that CT/TT carriers performed worse than CC carriers on a long-term memory test. We followed up the 70 SCD subjects and also 31 subjects affected by mild cognitive impairment (MCI) for a mean follow-up time of 7 years, during which 16 SCD subjects progressed to MCI and 14 MCI subjects progressed to Alzheimer's disease (AD). Carrying the T allele was associated with MCI and with a two times-higher risk of developing MCI than CC carriers. In the SCD sample, CT/TT carriers showed a greater worsening on Rivermead Behavioral Memory Test (RBMT) compared to CC carriers. In the MCI sample, CT/TT carriers performed worse than CC carriers on RBMT. There is a lack of consensus on the effect of KIBRA gene variants on cognitive performances in episodic memory and on the risk of AD. Our results confirm a role of T allele on progression of cognitive decline.

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.

A new social-family model for eating disorders: A European multicentre project using a case-control design.

OBJECTIVE: To examine a new socio-family risk model of Eating Disorders (EDs) using path-analyses. METHOD: The sample comprised 1264 (ED patients = 653; Healthy Controls = 611) participants, recruited into a multicentre European project. Socio-family factors assessed included: perceived maternal and parental parenting styles, family, peer and media influences, and body dissatisfaction. Two types of path-analyses were run to assess the socio-family model: 1.) a multinomial logistic path-model including ED sub-types [Anorexia Nervosa-Restrictive (AN-R), AN-Binge-Purging (AN-BP), Bulimia Nervosa (BN) and EDNOS)] as the key polychotomous categorical outcome and 2.) a path-model assessing whether the socio-family model differed across ED sub-types and healthy controls using body dissatisfaction as the outcome variable. RESULTS: The first path-analyses suggested that family and media (but not peers) were directly and indirectly associated (through body dissatisfaction) with all ED sub-types. There was a weak effect of perceived parenting directly on ED sub-types and indirectly through family influences and body dissatisfaction. For the second path-analyses, the socio-family model varied substantially across ED sub-types. Family and media influences were related to body dissatisfaction in the EDNOS and control sample, whereas perceived abusive parenting was related to AN-BP and BN. DISCUSSION: This is the first study providing support for this new socio-family model, which differed across ED sub-types. This suggests that prevention and early intervention might need to be tailored to diagnosis-specific ED profiles.

Rare mutations in SQSTM1 modify susceptibility to frontotemporal lobar degeneration.

Mutations in the gene coding for Sequestosome 1 (SQSTM1) have been genetically associated with amyotrophic lateral sclerosis (ALS) and Paget disease of bone. In the present study, we analyzed the SQSTM1 coding sequence for mutations in an extended cohort of 1,808 patients with frontotemporal lobar degeneration (FTLD), ascertained within the European Early-Onset Dementia consortium. As control dataset, we sequenced 1,625 European control individuals and analyzed whole-exome sequence data of 2,274 German individuals (total n = 3,899). Association of rare SQSTM1 mutations was calculated in a meta-analysis of 4,332 FTLD and 10,240 control alleles. We identified 25 coding variants in FTLD patients of which 10 have not been described. Fifteen mutations were absent in the control individuals (carrier frequency <0.00026) whilst the others were rare in both patients and control individuals. When pooling all variants with a minor allele frequency <0.01, an overall frequency of 3.2 % was calculated in patients. Rare variant association analysis between patients and controls showed no difference over the whole protein, but suggested that rare mutations clustering in the UBA domain of SQSTM1 may influence disease susceptibility by doubling the risk for FTLD (RR = 2.18 [95 % CI 1.24-3.85]; corrected p value = 0.042). Detailed histopathology demonstrated that mutations in SQSTM1 associate with widespread neuronal and glial phospho-TDP-43 pathology. With this study, we provide further evidence for a putative role of rare mutations in SQSTM1 in the genetic etiology of FTLD and showed that, comparable to other FTLD/ALS genes, SQSTM1 mutations are associated with TDP-43 pathology.

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.

Plasma GFAP, NfL and pTau 181 detect preclinical stages of dementia.

Background: Plasma biomarkers are preferable to invasive and expensive diagnostic tools, such as neuroimaging and lumbar puncture that are gold standard in the clinical management of Alzheimer's Disease (AD). Here, we investigated plasma Glial Fibrillary Acidic Protein (GFAP), Neurofilament Light Chain (NfL) and Phosphorylated-tau-181 (pTau 181) in AD and in its early stages: Subjective cognitive decline (SCD) and Mild cognitive impairment (MCI). Material and methods: This study included 152 patients (42 SCD, 74 MCI and 36 AD). All patients underwent comprehensive clinical and neurological assessment. Blood samples were collected for Apolipoprotein E (APOE) genotyping and plasma biomarker (GFAP, NfL, and pTau 181) measurements. Forty-three patients (7 SCD, 27 MCI, and 9 AD) underwent a follow-up (FU) visit after 2 years, and a second plasma sample was collected. Plasma biomarker levels were detected using the Simoa SR-X technology (Quanterix Corp.). Statistical analysis was performed using SPSS software version 28 (IBM SPSS Statistics). Statistical significance was set at p < 0.05. Results: GFAP, NfL and pTau 181 levels in plasma were lower in SCD and MCI than in AD patients. In particular, plasma GFAP levels were statistically significant different between SCD and AD (p=0.003), and between MCI and AD (p=0.032). Plasma NfL was different in SCD vs MCI (p=0.026), SCD vs AD (p<0.001), SCD vs AD FU (p<0.001), SCD FU vs AD (p=0.033), SCD FU vs AD FU (p=0.011), MCI vs AD (p=0.002), MCI FU vs AD (p=0.003), MCI FU vs AD FU (p=0.003) and MCI vs AD FU (p=0.003). Plasma pTau 181 concentration was significantly different between SCD and AD (p=0.001), MCI and AD (p=0.026), MCI FU and AD (p=0.020). In APOE ϵ4 carriers, a statistically significant increase in plasma NfL (p<0.001) and pTau 181 levels was found (p=0.014). Moreover, an association emerged between age at disease onset and plasma GFAP (p = 0.021) and pTau181 (p < 0.001) levels. Discussion and conclusions: Plasma GFAP, NfL and pTau 181 are promising biomarkers in the diagnosis of the prodromic stages and prognosis of dementia.

Data-driven subtypes of mixed semantic-logopenic primary progressive aphasia: Linguistic features, biomarker profiles and brain metabolic patterns.

Mixed primary progressive aphasia (mPPA) accounts for a substantial proportion of primary progressive aphasia (PPA) cases. However, the lack of a standardised definition of this condition has resulted in misclassification of PPA cases. In this study, we enrolled 55 patients diagnosed with PPA, comprising 12 semantic variant (svPPA), 23 logopenic variant (lvPPA), and 20 mPPA cases with linguistic characteristics consistent with both svPPA and lvPPA (s/lvPPA). All patients underwent language assessments, evaluation of Alzheimer's disease biomarkers (via cerebrospinal fluid analysis or Amyloid-PET), and 18F-FDG-PET brain scans. An agglomerative hierarchical clustering (AHC) analysis based on linguistic characteristics revealed two distinct clusters within the s/lvPPA group: cluster k1 (n = 10) displayed an AD-like biomarker profile, with lower levels of Aß42 and Aß42/Aß40 ratio, along with higher levels of t-tau and p-tau compared to cluster k2 (n = 10). Interestingly, k1 exhibited linguistic features that were similar to those of svPPA. Both clusters exhibited extensive temporoparietal hypometabolism. These findings support the hypothesis that a subgroup of s/lvPPA may represent a clinical manifestation of AD-related PPA.

Disentangling empathy impairment along Alzheimer's disease continuum: From subjective cognitive decline to Alzheimer's dementia.

Little is known about empathy changes from the early stages of Alzheimer's Disease (AD) continuum. The aim of this study is to investigate empathy across AD spectrum from Subjective Cognitive Decline (SCD) to Mild Cognitive Impairment (MCI) and AD dementia (AD-d). Forty-five SCD, 83 MCI and 80 AD-d patients were included. Empathy was assessed by Interpersonal Reactivity Index (IRI) (Perspective Taking - PT, Fantasy - FT, Empathic Concern - EC, and Personal Distress - PD), rated by caregivers before (T0) and after (T1) cognitive symptoms' onset. IRI was also administered to SCD patients to have a self-reported empathy evaluation. Facial emotion recognition was assessed by Ekman-60 Faces Test. Twenty-two SCD, 54 MCI and 62 AD-d patients underwent CSF biomarkers analysis and were classified as carriers of AD pathology (AP+) when they were A+/T+ (regardless of N), or non-carriers (AP-) when they were A- (regardless of T and N), or A+/T-/N-, or A+/T-/N+ according to the A/T(N) system. Cerebral FDG-PET SPM analysis was used to explore neural correlates underlying empathy deficits. PD scores significantly increased from T0 to T1 in SCD, MCI and AD-d (p < .001), while PT scores decreased in MCI and in AD-d (p < .001). SCD AP+ showed a greater increase in PD scores over time (ΔPD T0 - T1) than SCD AP- (p < .001). SCD self-reported PT scores were lower than those of general Italian population (14.94 ± 3.94, 95% C.I. [13.68-16.20] vs 17.70 ± 4.36, 95% C.I. [17.30-18.10]). In AD continuum (SCD AP+, MCI AP+, AD-d), a positive correlation was detected between PT-T1 and brain metabolism in left posterior cingulate gyrus, precuneus and right frontal gyri; a negative correlation was found between ΔPT and brain metabolism in bilateral posterior cingulate gyri. PT may be subtly involved since the preclinical phase of AD. Changes over time of PD are influenced by the underlying Alzheimer's pathology and could potentially serve as an early AD neuropsychological marker.