Astrocytic-derived vascular remodeling factors are independently associated with blood brain barrier permeability in Alzheimer's disease.

Astrocytes in Alzheimer's disease (AD) exert a pivotal role in the maintenance of blood-brain barrier (BBB) integrity essentially through structural support and release of soluble factors. This study provides new insights into the vascular remodeling processes occurring in AD, and reveals, in vivo, a pathological profile of astrocytic secretion involving Vascular Endothelial Growth Factor (VEGF), Matrix Metalloproteinases (MMP)-9, MMP-2 and Endothelin-1 (ET-1). Cerebrospinal fluid (CSF) levels of VEGF, MMP-2/-9 were lower in patients belonging to the AD continuum, compared to aged-matched controls. CSF levels of VEGF and ET-1 positively correlated with MMP-9 but negatively with MMP-2, suggesting a complex vascular remodeling process occurring in AD. Only MMP-2 levels were significantly associated with CSF AD biomarkers. Conversely, higher MMP-2 (ß = 0.411, p < 0.001), ET-1 levels (ß = 0.344, p < 0.001) and VEGF (ß = 0.221, p = 0.022), were associated with higher BBB permeability. Astrocytic-derived vascular remodeling factors are altered in AD, disclosing the failure of important protective mechanisms which proceed independently alongside AD pathology.

Constitutive NOS Production Is Modulated by Alzheimer's Disease Pathology Depending on APOE Genotype.

Both the endothelial (eNOS) and the neuronal (nNOS) isoforms of constitutive Nitric Oxide Synthase have been implicated in vascular dysfunctions in Alzheimer's disease (AD). We aimed to explore the relationship between amyloid pathology and NO dynamics by comparing the cerebrospinal fluid (CSF) levels of nNOS and eNOS of 8 healthy controls (HC) and 27 patients with a clinical diagnosis of Alzheimer's disease and isolated CSF amyloid changes, stratified according to APOE ε genotype (APOE ε3 = 13, APOE ε4 = 14). Moreover, we explored the associations between NOS isoforms, CSF AD biomarkers, age, sex, cognitive decline, and blood-brain barrier permeability. In our cohort, both eNOS and nNOS levels were increased in APOE ε3 with respect to HC and APOE ε4. CSF eNOS inversely correlated with CSF Amyloid-ß42 selectively in carriers of APOE ε3; CSF nNOS was negatively associated with age and CSF p-tau only in the APOE ε4 subgroup. Increased eNOS could represent compensative vasodilation to face progressive Aß-induced vasoconstriction in APOE ε3, while nNOS could represent the activation of NO-mediated plasticity strategies in the same group. Our results confirm previous findings that the APOE genotype is linked with different vascular responses to AD pathology.

Effect of Vascular Risk Factors on Blood-Brain Barrier and Cerebrospinal Fluid Biomarkers Along the Alzheimer's Disease Continuum: A Retrospective Observational Study.

BACKGROUND: Blood-brain barrier (BBB) dysfunction could favor the pathogenesis and progression of Alzheimer's disease (AD). Vascular risk factors (VRF) could worsen BBB integrity, thus promoting neurode generation. OBJECTIVE: To investigate BBB permeability and its relation with VRF along the AD continuum (ADc). Cerebrospinal fluid (CSF) Amyloid (A) and p-tau (T) levels were used to stratify patients. METHODS: We compared CSF/plasma albumin ratio (QAlb) of 131 AD patients and 24 healthy controls (HC). APOE genotype and VRF were evaluated for each patient. Spearman's Rho correlation was used to investigate the associations between Qalb and CSF AD biomarkers. Multivariate regression analyses were conducted to explore the relationship between Qalb and AD biomarkers, sex, age, cognitive status, and VRF. RESULTS: QAlb levels did not show significant difference between ADc patients and HC (p = 0.984). However, QAlb was significantly higher in A + T-compared to A + T+ (p = 0.021). In ADc, CSF p-tau demonstrated an inverse correlation with QAlb, a finding confirmed in APOE4 carriers (p = 0.002), but not in APOE3. Furthermore, in APOE4 carriers, sex, hypertension, and hypercholesterolemia were associated with QAlb (p = 0.004, p = 0.038, p = 0.038, respectively), whereas only sex showed an association in APOE3 carriers (p = 0.026). CONCLUSIONS: BBB integrity is preserved in ADc. Among AT categories, A + T-have a more permeable BBB than A + T+. In APOE4 carriers, CSF p-tau levels display an inverse association with BBB permeability, which in turn, seems to be affected by VRF. These data suggest a possible relationship between BBB efficiency, VRF and CSF p-tau levels depending on APOE genotype.

Blood-brain barrier permeability is associated with different neuroinflammatory profiles in Alzheimer's disease.

INTRODUCTION: Inflammation is an important player in Alzheimer's disease (AD), whose effects can be influenced by the blood-brain barrier (BBB). Here, we investigated the relationship between BBB permeability, indicated by cerebrospinal fluid (CSF)/plasma albumin quotient (Qalb), and CSF indexes of neuroinflammation in a cohort of biologically defined AD patients. METHODS: Fifty-nine consecutive patients with mild cognitive impairment (MCI) or early AD (Mini-Mental State Examination [MMSE] >22) underwent CSF analysis for inflammatory cytokines (interleukin [IL]-1ß, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, Il-10, IL-12, IL-13, IL-17, tumor necrosis factor-α [TNF-α], interferon-γ [IFN-γ], granulocyte-monocyte colony-stimulating factor [GM-CSF], granulocyte colony-stimulating factor [G-CSF]). Using backward stepwise linear regression analysis, we explored the potential influence of each cytokine CSF level on Qalb considering age, sex, and apolipoprotein E (APOE) as covariates. RESULTS: Higher levels of IL-4 (ß = 0.356, 0.005) and IL-8 (ß = 0.249, 0.05) were associated with higher Qalb values, while macrophage inflammatory protein-1α (MIP-1ß) (ß = -0.274; p = 0.032) and TNF-α (ß = -0.248; p = 0.031) showed a significant negative association with BBB permeability. Age was also positively associated with Qalb (ß = 0.283; p = 0.016). CONCLUSIONS: Despite the overall integrity of the BBB, its permeability could either influence or be influenced by central neuroinflammation, reflected by CSF cytokine levels. This is in line with previous studies that showed that patients with a more intact barrier are those with more prominent neurodegeneration. Our findings suggest that different neuroinflammatory profiles can be associated with different levels of BBB permeability in AD.

Different associations between amyloid-ßeta 42, amyloid-ßeta 40, and amyloid-ßeta 42/40 with soluble phosphorylated-tau and disease burden in Alzheimer's disease: a cerebrospinal fluid and fluorodeoxyglucose-positron emission tomography study.

BACKGROUND: Despite the high sensitivity of cerebrospinal fluid (CSF) amyloid beta (Aß)42 to detect amyloid pathology, the Aß42/Aß40 ratio (amyR) better estimates amyloid load, with higher specificity for Alzheimer's disease (AD). However, whether Aß42 and amyR have different meanings and whether Aß40 represents more than an Aß42-corrective factor remain to be clarified. Our study aimed to compare the ability of Aß42 and amyR to detect AD pathology in terms of p-tau/Aß42 ratio and brain glucose metabolic patterns using fluorodeoxyglucose-positron emission tomography (FDG-PET). METHODS: CSF biomarkers were analyzed with EUROIMMUN ELISA. We included 163 patients showing pathological CSF Aß42 and normal p-tau (A + T - = 98) or pathological p-tau levels (A + T + = 65) and 36 control subjects (A - T -). A + T - patients were further stratified into those with normal (CSFAß42 + /amyR - = 46) and pathological amyR (CSFAß42 + /amyR + = 52). We used two distinct cut-offs to determine pathological values of p-tau/Aß42: (1) ≥ 0.086 and (2) ≥ 0.122. FDG-PET patterns were evaluated in a subsample of patients (n = 46) and compared to 24 controls. RESULTS: CSF Aß40 levels were the lowest in A - T - and in CSFAß42 + /amyR - , higher in CSFAß42 + /amyR + and highest in A + T + (F = 50.75; p < 0.001), resembling CSF levels of p-tau (F = 192; p < 0.001). We found a positive association between Aß40 and p-tau in A - T - (ß = 0.58; p < 0.001), CSFAß42 + /amyR - (ß = 0.47; p < 0.001), and CSFAß42 + /amyR + patients (ß = 0.48; p < 0.001) but not in A + T + . Investigating biomarker changes as a function of amyR, we observed a weak variation in CSF p-tau (+ 2 z-scores) and Aß40 (+ 0.8 z-scores) in the normal amyR range, becoming steeper over the pathological threshold of amyR (p-tau: + 5 z-scores, Aß40: + 4.5 z-score). CSFAß42 + /amyR + patients showed a significantly higher probability of having pathological p-tau/Aß42 than CSFAß42 + /amyR - (cut-off ≥ 0.086: OR 23.3; cut-off ≥ 0.122: OR 8.8), which however still showed pathological values of p-tau/Aß42 in some cases (cut-off ≥ 0.086: 35.7%; cut-off ≥ 0.122: 17.3%) unlike A - T - . Accordingly, we found reduced FDG metabolism in the temporoparietal regions of CSFAß42 + /amyR - compared to controls, and further reduction in frontal areas in CSFAß42 + /amyR + , like in A + T + . CONCLUSIONS: Pathological p-tau/Aß42 and FDG hypometabolism typical of AD can be found in patients with decreased CSF Aß42 levels alone. AmyR positivity, associated with higher Aß40 levels, is accompanied by higher CSF p-tau and widespread FDG hypometabolism.

Cerebrospinal Fluid sTREM-2, GFAP, and ß-S100 in Symptomatic Sporadic Alzheimer's Disease: Microglial, Astrocytic, and APOE Contributions Along the Alzheimer's Disease Continuum.

BACKGROUND: Many transversal mechanisms act synergistically at different time-points in the cascade of Alzheimer's disease (AD), since amyloid-ß (Aß) deposition, tau pathology, and neuroinflammation influence each other. OBJECTIVE: We explored the contributions of microglia and astrocytes in patients with symptomatic sporadic AD stratified according to AT(N) system and APOE genotype. METHODS: We compared the cerebrospinal fluid (CSF) levels of sTREM-2 and markers of astrocytic activation (GFAP; ß-S100) from 71 patients with AD (23 A+T-,48 A+T+; 38 APOEɛ3, 33 APOEɛ4) and 30 healthy controls (HC). With multivariate analyses we investigated associations between glial biomarkers, Aß42, and p-tau in all subgroups. RESULTS: CSF sTREM-2 was higher in A+T+ [1.437 (0.264)] and A+T- [1.355 (0.213)] than in HC [1.042 (0.198); both p < 0.001]; GFAP and ß-S100 were comparable across groups. Considering all patients, sTREM-2 positively associated with Aß42 (p = 0.04) and p-tau (=0.016), with the first being present only in the A+T- subgroup (p = 0.023). GFAP positively associated with Aß42 in all patients (p = 0.020) and in the A+T+ subgroup (p = 0.04). Stratifying by APOE, a positive association of sTREM-2 and p-tau was confirmed selectively in carriers of ɛ4 (p = 0.018). Finally, sTREM-2 positively correlated with ß-S100 in all subgroups, and with GFAP in A+T+ (p = 0.042). CONCLUSION: Our results confirm the increase of CSF sTREM-2 in AD, which associates with reduced amyloidopathy in A+T- patients. Moreover, microglial activation seems to increase CSF tau levels in carriers of APOEɛ4, is associated with astrocytic reactivity (GFAP) in A+T+, and likely leads the acquisition of a more neurotoxic astrocytic phenotype (ß-S100).

Functional Correlates of Microglial and Astrocytic Activity in Symptomatic Sporadic Alzheimer's Disease: A CSF/18F-FDG-PET Study.

Glial and microglial cells contribute to brain glucose consumption and could actively participate in shaping patterns of brain hypometabolism. Here, we aimed to investigate the association between 18F-fluorodeoxyglucose (18F-FDG) uptake and markers of microglial and astrocytic activity in a cohort of patients with Alzheimer's Disease (AD). We dosed cerebrospinal fluid (CSF) levels of soluble Triggering Receptor Expressed on Myeloid cells (sTREM2), Glial Fibrillary Acidic Protein (GFAP), a marker of reactive astrogliosis, and ß-S100, a calcium-binding protein associated with a neurotoxic astrocytic profile. No associations were found between sTREM-2 and 18F-FDG uptake. Instead, 18F-FDG uptake was associated negatively with CSF ß-S100 in the left supramarginal gyrus, inferior parietal lobe and middle temporal gyrus (Brodmann Areas (BA) 21 and 40). Increased ß-S100 levels could negatively regulate neuronal activity in the temporo-parietal cortex to prevent damage associated with AD hyperactivity, or rather they could reflect neurotoxic astrocytic activation contributing to AD progression in key strategic areas. We also identified a trend of positive association of 18F-FDG uptake with CSF GFAP in the right fronto-medial and precentral gyri (BA 6, 9 and 11), which has been reported in early AD and could either be persisting as an epiphenomenon tied to disease progression or be specifically aimed at preserving functions in the frontal cortex. Overall, CSF markers of astrogliosis seem to correlate with cortical glucose uptake in symptomatic sporadic AD, highlighting the role of astrocytes in shaping regional hypometabolism and possibly clinical presentation.

Interplay between the catecholaminergic enzymatic axis and neurodegeneration/neuroinflammation processes in the Alzheimer's disease continuum.

BACKGROUND AND PURPOSE: The locus coeruleus (LC) provides dopamine/noradrenaline (DA/NA) innervation throughout the brain and undergoes early degeneration in Alzheimer's disease (AD). We evaluated catecholaminergic enzyme levels in the cerebrospinal fluid (CSF) of a group of patients biologically defined as within the AD continuum (ADc) and explored their relationship with AD biomarkers and cytokine/growth factor levels to investigate their interplay with neurodegenerative and neuroinflammatory processes. METHODS: The CSF concentration of DA transporter (DAT), tyrosine-hydroxylase (TH), DOPA-decarboxylase (DDC), and dopamine-ß-hydroxylase (DßH), as well as cytokine/growth factor levels, were analyzed in 41 ADc patients stratified according to CSF beta-amyloid (Aß)1-42 (A) and p-tau (T) in AD pathological changes (A+ T-) and AD (A+ T+) subgroups, as well as in 15 control subjects (A- T-). RESULTS: The ADc group had lower CSF levels of DAT and TH but increased DßH levels to compensate for NA synthesis. DDC levels were higher in the A+ T+ subgroup but comparable with controls in the A+ T- subgroup, probably because the DA system is resilient to the degeneration of LC neurons in the absence of tau pathology. Adjusting for age, sex, APOE genotype, and cognitive status, a significant association was found between TH and Aß1-42 (R2  = 0.25) and between DDC and p-tau (R2  = 0.33). Finally, TH correlated with interleukin (IL)-10 levels (p = 0.0008) and DßH with IL-1ß (p = 0.03), IL-4 (p = 0.02), granulocyte colony-stimulating factor (p = 0.007), and IL-17 (p = 0.01). CONCLUSIONS: Taken together, these findings suggest that catecholaminergic enzymes, functional markers of the catecholaminergic system, are closely linked to the neurodegenerative and neuroinflammatory processes in AD pathology.

Biobanking for Neurodegenerative Diseases: Challenge for Translational Research and Data Privacy.

Biobanking has emerged as a strategic challenge to promote knowledge on neurological diseases, by the application of translational research. Due to the inaccessibility of the central nervous system, the advent of biobanks, as structure collecting biospecimens and associated data, are essential to turn experimental results into clinical practice. Findings from basic research, omics sciences, and in silico studies, definitely require validation in clinically well-defined cohorts of patients, even more valuable when longitudinal, or including preclinical and asymptomatic individuals. Finally, collecting biological samples requires a great effort to guarantee respect for transparency and protection of sensitive data of patients and donors. Since the European General Data Protection Regulation 2016/679 has been approved, concerns about the use of data in biomedical research have emerged. In this narrative review, we focus on the essential role of biobanking for translational research on neurodegenerative diseases. Moreover, we address considerations for biological samples and data collection, the importance of standardization in the preanalytical phase, data protection (ethical and legal) and the role of donors in improving research in this field.

Precuneus magnetic stimulation for Alzheimer's disease: a randomized, sham-controlled trial.

Repetitive transcranial magnetic stimulation (rTMS) is emerging as a non-invasive therapeutic strategy in the battle against Alzheimer's disease. Alzheimer's disease patients primarily show alterations of the default mode network for which the precuneus is a key node. Here, we hypothesized that targeting the precuneus with TMS represents a promising strategy to slow down cognitive and functional decline in Alzheimer's disease patients. We performed a randomized, double-blind, sham-controlled, phase 2, 24-week trial to determine the safety and efficacy of precuneus stimulation in patients with mild-to-moderate Alzheimer's disease. Fifty Alzheimer's disease patients were randomly assigned in a 1:1 ratio to either receive precuneus or sham rTMS (mean age 73.7 years; 52% female). The trial included a 24-week treatment, with a 2-week intensive course in which rTMS (or sham) was applied daily five times per week, followed by a 22-week maintenance phase in which stimulation was applied once weekly. The Clinical Dementia Rating Scale-Sum of Boxes was selected as the primary outcome measure, in which post-treatment scores were compared to baseline. Secondary outcomes included score changes in the Alzheimer's Disease Assessment Scale-Cognitive Subscale, Mini-Mental State Examination and Alzheimer's Disease Cooperative Study-Activities of Daily Living scale. Moreover, single-pulse TMS in combination with EEG was used to assess neurophysiological changes in precuneus cortical excitability and oscillatory activity. Our findings show that patients that received precuneus repetitive magnetic stimulation presented a stable performance of the Clinical Dementia Rating Scale-Sum of Boxes score, whereas patients treated with sham showed a worsening of their score. Compared with the sham stimulation, patients in the precuneus stimulation group also showed also significantly better performances for the secondary outcome measures, including the Alzheimer's Disease Assessment Scale-Cognitive Subscale, Mini-Mental State Examination and Alzheimer's Disease Cooperative Study-Activities of Daily Living scale. Neurophysiological results showed that precuneus cortical excitability remained unchanged after 24 weeks in the precuneus stimulation group, whereas it was significantly reduced in the sham group. Finally, we found an enhancement of local gamma oscillations in the group treated with precuneus stimulation but not in patients treated with sham. We conclude that 24 weeks of precuneus rTMS may slow down cognitive and functional decline in Alzheimer's disease. Repetitive TMS targeting the default mode network could represent a novel therapeutic approach in Alzheimer's disease patients.

Decreased Frontal Gamma Activity in Alzheimer Disease Patients.

OBJECTIVE: In Alzheimer disease (AD) animal models, synaptic dysfunction has recently been linked to a disorder of high-frequency neuronal activity. In patients, a clear relation between AD and oscillatory activity remains elusive. Here, we attempt to shed light on this relation by using a novel approach combining transcranial magnetic stimulation and electroencephalography (TMS-EEG) to probe oscillatory activity in specific hubs of the frontoparietal network in a sample of 60 mild-to-moderate AD patients. METHODS: Sixty mild-to-moderate AD patients and 21 age-matched healthy volunteers (HVs) underwent 3 TMS-EEG sessions to assess cortical oscillations over the left dorsolateral prefrontal cortex, the precuneus, and the left posterior parietal cortex. To investigate the relations between oscillatory activity, cortical plasticity, and cognitive decline, AD patients underwent a TMS-based neurophysiological characterization and a cognitive evaluation at baseline. The latter was repeated after 24 weeks to monitor clinical evolution. RESULTS: AD patients showed a significant reduction of frontal gamma activity as compared to age-matched HVs. In addition, AD patients with a more prominent decrease of frontal gamma activity showed a stronger impairment of long-term potentiation-like plasticity and a more pronounced cognitive decline at subsequent follow-up evaluation at 24 weeks. INTERPRETATION: Our data provide novel evidence that frontal lobe gamma activity is dampened in AD patients. The current results point to the TMS-EEG approach as a promising technique to measure individual frontal gamma activity in patients with AD. This index could represent a useful biomarker to predict disease progression and to evaluate response to novel pharmacological therapies. ANN NEUROL 2022;92:464-475.

Isolated Amyloid-ß Pathology Is Associated with Preserved Cortical Plasticity in APOE4 Alzheimer's Disease Patients.

BACKGROUND: Long-term potentiation (LTP) like-cortical plasticity impairment and cholinergic neurotransmission deficits have been widely demonstrated in Alzheimer's disease (AD) patients. OBJECTIVE: In this study we aim to investigate the neurophysiological features underlying cognitive decline in AD patients according to the National Institute on Aging-Alzheimer's Association (NIA-AA) classification and APOE genotype. METHODS: 65 newly diagnosed AD patients were enrolled. APOE genotype and lumbar puncture for the analysis of cerebrospinal fluid biomarkers were performed for diagnostic purposes. Patients were subdivided upon NIA-AA criteria, according to the presence of biomarkers of amyloid-ß (Aß) deposition (A) and fibrillar tau (T), in four groups: A+/T-E4 (n = 9), A+/T-E3 (n = 18), A+/T+ E4 (n = 21), and A+/T+ E3 (n = 17). We applied intermittent theta burst stimulation protocol over the primary motor cortex to assess LTP-like cortical plasticity and short latency afferent inhibition (SAI) protocol to investigate central cholinergic activity. Patients were followed over 24 months. Cognitive decline was evaluated considering changes in Mini-Mental State Examination (MMSE) scores respect to the baseline. RESULTS: A+/T-E4 patients showed preserved LTP-like cortical plasticity as compared to A+/T-E3 and to A+/T+ patients independently from genotype (p < 0.001). In addition, A+/T-E4 patients showed a slower cognitive decline with respect to A+/T+ E4 (delta MMSE -0.5±2.12 versus -6.05±4.95; post-hocp = 0.004) and to A+/T+ E3 patients (-4.12±4.14; post-hoc p = 0.028). No differences were found for SAI protocol (p > 0.05). CONCLUSION: Our results suggest that APOE4 in patients with isolated Aß pathology could exert positive effects on LTP-like cortical plasticity with a consequent slower cognitive decline.

Diabetes mellitus contributes to higher cerebrospinal fluid tau levels selectively in Alzheimer's disease patients with the APOE4 genotype.

BACKGROUND AND PURPOSE: Diabetes mellitus (DM) is considered a risk factor for Alzheimer's disease (AD) and shares some pathological pathways, such as activation of amyloid cascade and tau phosphorylation. The aim of the present study was to investigate to what extent DM could impact on neurodegeneration within the AD continuum, using ß amyloid (A: Aß1-42 ) and phosphorylated tau (T: p-tau) biomarkers to discriminate patients by Alzheimer's pathological change (A+/T-) and AD (A+/T+), according to the National Institute on Aging and Alzheimer's Association classification. In addition, we aimed to evaluate whether APOE genotype interacts with tau protein and glucose metabolism dysfunction to affect the pathological process. METHODS: For this retrospective observational study, 1350 patients were recruited. The patients underwent a complete clinical investigation, neuropsychological assessment, lumbar puncture for cerebrospinal fluid (CSF) biomarkers analysis and APOE genotyping. RESULTS: A total of 607 patients fulfilled the clinical criteria of mild cognitive impairment or early dementia. In A+T- patients (n = 350), DM did not influence CSF biomarker levels, while among A+T+ patients (n = 257) those with DM showed increased total tau (t-tau) levels compared to non-DM patients (DM: 919.4 ± 444 vs. non-DM: 773.1 ± 348.2; p = 0.04), but similar p-tau (p = 0.72) and Aß1-42  levels (p = 0.83). Furthermore, multivariable regression analyses showed a significant association between DM and t-tau CSF levels, adjusting for age and sex, in APOE E4+ carriers (coefficient 222.83, 95% confidence interval 47.49-398.1; p = 0.01), but not in APOE E4- (p = 0.53). CONCLUSIONS: The present study shows a clear dependency of CSF t-tau levels on DM for APOE E4+ AD patients, suggesting important differences between APOE E4-related and non-related disease, with key implications for AD pathophysiology and treatment.

Brain energy metabolism and neurodegeneration: hints from CSF lactate levels in dementias.

Mitochondrial dysfunction is pivotal in the development of neurodegenerative dementias, causing cellular death alongside disease-specific pathogenic cascades. Holding cerebrospinal fluid (CSF) lactates as an indirect measure of brain metabolic activity, we first compared CSF lactate levels from patients with Alzheimer's disease (AD)-stratified according to the ATN system and epsilon genotype-frontotemporal dementia (FTD) and dementia with Lewy body (DLB) to findings from healthy controls. With respect to controls, we detected lower CSF lactates in patients with AD and FTD but comparable levels in patients with DLB. Second, a correlation analysis between CSF lactates and biomarkers of neurodegeneration identified an inverse correlation between lactates and levels of t-tau and p-tau only in the Alzheimer's continuum. The reduction of CSF lactate correlates to the advent of tauopathy and cellular death in AD, implying that Aß pathology alone is not sufficient to induce neuronal metabolic impairment. The metabolic impairment in FTD patients has a similar explanation, as it is likely due to fast neuronal degeneration in the disease. The absence of CSF lactate reduction in patients with DLB may be related to the prevalent subcortical localization of the pathology.

Cognitive reserve and Alzheimer's biological continuum: clues for prediction and prevention of dementia.

Cognitive reserve is originally an epidemiological concept that encompasses individual abilities to cope with changes. It is considered the result of a balance between processes of cellular damage and repair, and its description raised much interest in predicting and preventing cognitive decline in aging and Alzheimer's disease (AD). In this study, we discussed the concept of cognitive reserve considering the recent definition of AD as a biological continuum and suggest that the protection of cognitive reserve may result from efficient synaptic plasticity mechanisms. Despite pathological changes of AD appearing very early during life, long before the onset of cognitive symptoms, different variables act together to keep repair mechanisms effective guaranteeing successful aging if environmental enrichment is maintained.

Effects of Palmitoylethanolamide Combined with Luteoline on Frontal Lobe Functions, High Frequency Oscillations, and GABAergic Transmission in Patients with Frontotemporal Dementia.

BACKGROUND: Frontotemporal dementia (FTD) is a presenile neurodegenerative disease for which there is no effective pharmacological treatment. Recently, a link has been proposed between neuroinflammation and FTD. OBJECTIVE: Here, we aim to investigate the effects of palmitoylethanolamide (PEA) combined with luteoline (PEA-LUT), an endocannabinoid with anti-inflammatory and neuroprotective effects, on behavior, cognition, and cortical activity in a sample of FTD patients. METHODS: Seventeen patients with a diagnosis of probable FTD were enrolled. Cognitive and neurophysiological evaluations were performed at baseline and after 4 weeks of PEA-LUT 700 mg×2/day. Cognitive effects were assessed by Neuropsychiatric Inventory (NPI), Mini-Mental State Examination, Frontal Assessment Battery (FAB), Screening for Aphasia in Neurodegeneration, Activities of Daily Living-Instrumental Activities of Daily Living, and Frontotemporal Lobar Degeneration-modified Clinical Dementia Rating scale. To investigate in vivo neurophysiological effects of PEA-LUT, we used repetitive and paired-pulse transcranial magnetic stimulation (TMS) protocols assessing LTP-like cortical plasticity, short-interval intracortical inhibition, long-interval intracortical inhibition (LICI), and short-latency afferent inhibition. Moreover, we used TMS combined with EEG to evaluate the effects on frontal lobe cortical oscillatory activity. RESULTS: Treatment with PEA-LUT was associated with an improvement in NPI and FAB scores. Neurophysiological evaluation showed a restoration of LICI, in particular at ISI 100 ms, suggesting a modulation of GABA(B) activity. TMS-EEG showed a remarkable increase of TMS-evoked frontal lobe activity and of high-frequency oscillations in the beta/gamma range. CONCLUSION: PEA-LUT could reduce behavioral disturbances and improve frontal lobe functions in FTD patients through the modulation of cortical oscillatory activity and GABA(B)ergic transmission.

Effect of Rotigotine vs Placebo on Cognitive Functions Among Patients With Mild to Moderate Alzheimer Disease: A Randomized Clinical Trial.

Importance: Impairment of dopaminergic transmission may contribute to cognitive dysfunction in Alzheimer disease (AD). Objective: To investigate whether therapy with dopaminergic agonists may affect cognitive functions in patients with AD. Design, Setting, and Participants: This phase 2, monocentric, randomized, double-blind, placebo-controlled trial was conducted in Italy. Patients with mild to moderate AD were enrolled between September 1, 2017, and December 31, 2018. Data were analyzed from July 1 to September 1, 2019. Interventions: A rotigotine 2 mg transdermal patch for 1 week followed by a 4 mg patch for 23 weeks (n = 47) or a placebo transdermal patch for 24 weeks (n = 47). Main Outcomes and Measures: The primary end point was change from baseline on the Alzheimer Disease Assessment Scale-Cognitive Subscale. Secondary end points were changes in Frontal Assessment Battery, Alzheimer Disease Cooperative Study-Activities of Daily Living, and Neuropsychiatric Inventory scores. Prefrontal cortex activity was evaluated by transcranial magnetic stimulation combined with electroencephalography. Results: Among 94 patients randomized (mean [SD] age, 73.9 [5.6] years; 58 [62%] women), 78 (83%) completed the study. Rotigotine, as compared with placebo, had no significant effect on the primary end point: estimated mean change in Alzheimer Disease Assessment Scale-Cognitive Subscale score was 2.92 (95% CI, 2.51-3.33) for the rotigotine group and 2.66 (95% CI, 2.31-3.01) for the placebo group. For the secondary outcomes, there were significant estimated mean changes between groups for Alzheimer Disease Cooperative Study-Activities of Daily Living score (-3.32 [95% CI, -4.02 to -2.62] for rotigotine and -7.24 [95% CI, -7.84 to -6.64] for placebo) and Frontal Assessment Battery score (0.48 [95% CI, 0.31 to 0.65] for rotigotine and -0.66 [95% CI, -0.80 to -0.52] for placebo). There was no longitudinal change in Neuropsychiatric Inventory scores (1.64 [95% CI, 1.06-2.22] for rotigotine and 1.26 [95% CI, 0.77-1.75] for placebo group). Neurophysiological analysis of electroencephalography results indicated that prefrontal cortical activity increased in rotigotine but not in the placebo group. Adverse events were more common in the rotigotine group, with 11 patients dropping out compared with 5 in the placebo group. Conclusions and Relevance: In this randomized clinical trial, rotigotine treatment did not significantly affect global cognition in patients with mild to moderate AD; however, improvement was observed in cognitive functions highly associated with the frontal lobe and in activities of daily living. These findings suggest that treatment with the dopaminergic agonist rotigotine may reduce symptoms associated with frontal lobe cognitive dysfunction and thus may delay the impairment of activities of daily living. Trial Registration: ClinicalTrials.gov Identifier: NCT03250741.

Effects of Cerebellar Theta Burst Stimulation on Contralateral Motor Cortex Excitability in Patients with Alzheimer's Disease.

Although the cerebellum is not among the most renowned brain structures affected in Alzheimer`s disease (AD), recent evidence suggest that it undergoes degenerative changes during the course of the disease. A main neurophysiological feature of AD patients is the remarkable impairment of long term potentiation (LTP)-like cortical plasticity assessed in the primary motor cortex (M1) using theta burst stimulation (TBS) protocols. In healthy conditions, continuous (cTBS) and intermittent TBS (iTBS) of the cerebellum induce respectively long term depression (LTD)-like and LTP-like after effects in the contralateral M1. Here we aimed at examining the effects of cerebellar TBS on contralateral M1 excitability in a sample of 15 AD patients and 12 healthy age matched controls (HS). Motor evoked potentials (MEPs) were obtained in the contralateral M1 before and after cerebellar cTBS and iTBS protocols. As compared to HS, AD patients showed an impairment of LTP-like cortical plasticity mechanisms following cerebellar iTBS. No difference was observed for the cTBS protocol, in which both populations exhibited the expected LTD-like after effect. This study shows that mechanisms of cerebellar-cortical plasticity are impaired in AD. Given its role in high order cognitive functions, new potential therapeutic strategies could be built up in the future to modulate neural activity in the cerebellum in AD.

LTP-like cortical plasticity predicts conversion to dementia in patients with memory impairment.

BACKGROUND: New diagnostic criteria consider Alzheimer's disease (AD) as a clinico-biological entity identifiable in vivo on the presence of specific patterns of CSF biomarkers. OBJECTIVE: Here we used transcranial magnetic stimulation to investigate the mechanisms of cortical plasticity and sensory-motor integration in patients with hippocampal-type memory impairment admitted for the first time in the memory clinic stratified according to CSF biomarkers profile. METHODS: Seventy-three patients were recruited and divided in three groups according to the new diagnostic criteria: 1) Mild Cognitive Impaired (MCI) patients (n = 21); Prodromal AD (PROAD) patients (n = 24); AD with manifest dementia (ADD) patients (n = 28). At time of recruitment all patients underwent CSF sampling for diagnostic purposes. Repetitive and paired-pulse transcranial magnetic stimulation protocols were performed to investigate LTP-like and LTD-like cortical plasticity, short intracortical inhibition (SICI) and short afferent inhibition (SAI). Patients were the followed up during three years to monitor the clinical progression or the conversion to dementia. RESULTS: MCI patients showed a moderate but significant impairment of LTP-like cortical plasticity, while ADD and PROAD groups showed a more severe loss of LTP-like cortical plasticity. No differences were observed for LTD-like cortical plasticity, SICI and SAI protocols. Kaplan-Meyer analyses showed that PROAD and MCI patients converting to dementia had weaker LTP-like plasticity at time of first evaluation. CONCLUSION: LTP-like cortical plasticity could be a novel biomarker to predict the clinical progression to dementia in patients with memory impairment at prodromal stages of AD identifiable with the new diagnostic criteria based on CSF biomarkers.

Protective Role of Cerebrospinal Fluid Inflammatory Cytokines in Patients with Amnestic Mild Cognitive Impairment and Early Alzheimer's Disease Carrying Apolipoprotein E4 Genotype.

BACKGROUND: Neuroinflammatory cytokines can play a pivotal role in Alzheimer's disease (AD) contributing to the evolution of degenerative processes. OBJECTIVE: We aimed at evaluating the levels of cerebrospinal fluid (CSF) inflammatory cytokines, chemokines, and growth factors in subjects with diagnosis of amnestic mild cognitive impairment and mild AD. METHODS: We evaluated CSF contents of inflammatory cytokines in 66 patients divided according to the NIA-AA research framework and the APOE genotype. CSF of a group of cognitively unimpaired individuals (n = 23) was evaluated as control. All patients were evaluated for 24 months using Mini-Mental State Examination (MMSE). RESULTS: We found significant increased levels of IL-4, IL-6, IL-8, and G-CSF in the CSF of A+/T-APOE4 carriers, respect to A+/T-patients homozygous for APOE3, respect to A+/T+ patients, regardless the APOE status, and respect to controls. Over a period of 24 months, A+/T-APOE4 carriers, with increased levels of cytokines, showed a preserved cognitive evaluation when compared to the other subgroups of patients (delta MMSE at 24 months respect to baseline: 0.10±0.35; p < 0.05). CONCLUSION: Our data suggest that during early phases of AD, in APOE4 carriers, Aß pathology likely induces a specific cytokines pattern synthesis associated to cognitive preservation. These data highlight the different role that neuroinflammation can play in AD pathology based on the presence of specific CSF biomarkers and on the APOE status.