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.

Implication of GAB2 gene polymorphism in Italian patients with Alzheimer's disease.

A common polymorphism (rs2373115) in the GRB-associated binding protein 2 (GAB2) gene has been recently associated with the risk of developing Alzheimer's disease (AD) in 644 apolipoprotein E (ApoE) epsilon4 carriers. In order to assess the involvement of the GAB2 polymorphism in the risk of developing AD, we analyzed the genotype and allele distributions of the GAB2 rs2373115 polymorphism in 579 Italian subjects. Our results support a possible implication of GAB2 genetic variant in AD. However, the observed association was confined to ApoE epsilon4 non-carriers, thus suggesting a possible role of GAB2 as an independent risk factor for AD.

Neural correlates of altered insight in frontotemporal dementia: a systematic review.

Altered insight into disease or specific symptoms is a prominent clinical feature of frontotemporal dementia (FTD). Understanding the neural bases of insight is crucial to help improve FTD diagnosis, classification and management. A systematic review to explore the neural correlates of altered insight in FTD and associated syndromes was conducted. Insight was fractionated to examine whether altered insight into different neuropsychological/behavioural objects is underpinned by different or compatible neural correlates. 6 databases (Medline, Embase, PsycINFO, Web of Science, BIOSIS and ProQuest Dissertations & Theses Global) were interrogated between 1980 and August 2019. 15 relevant papers were found out of 660 titles screened. The studies included suggest that different objects of altered insight are associated with distinctive brain areas in FTD. For example, disease unawareness appears to predominantly correlate with right frontal involvement. In contrast, altered insight into social cognition potentially involves, in addition to frontal areas, the temporal gyrus, insula, parahippocampus and amygdala. Impaired insight into memory problems appears to be related to the frontal lobes, postcentral gyrus, parietal cortex and posterior cingulate. These results reflect to a certain extent those observed in other neurodegenerative conditions like Alzheimer's disease (AD) and also other brain disorders. Nevertheless, they should be cautiously interpreted due to variability in the methodological aspects used to reach those conclusions. Future work should triangulate different insight assessment approaches and brain imaging techniques to increase the understanding of this highly relevant clinical phenomenon in dementia.

SNPs in neurotrophin system genes and Alzheimer's disease in an Italian population.

Increasing evidence suggests a role for nerve growth factor (NGFB), brain-derived neurotrophic factor (BDNF), and their receptors, nerve growth factor receptor (NGFR), and neurotrophin tyrosine kinase receptors 1 and 2 (NTRK1 and NTRK2), in Alzheimer's disease (AD). However, genetic association between the neurotrophin system genes and AD has been poorly investigated. We genotyped 21 single nucleotide polymorphisms (SNPs) within these genes in a population of Italian AD patients and healthy controls. We found an allele-wise association of rs2072446 on NGFR with familial AD (fAD, p = 0.047), and a genotype-wise association of rs2289656 on NTRK2 with sporadic AD (sAD, p = 0.0036). rs6336 on NTRK1 resulted associated to early-onset sAD in both allele-wise (p = 0.028) and genotype-wise (p = 0.014) analysis, while rs1048218 on BDNF showed allele-wise association with late-onset sAD (p = 0.047). A trend to association with sAD and/or fAD was observed for other SNPs. Our results suggest that genetic variants of neurotrophin system genes might confer susceptibility to AD.

Lack of association between TNF-alpha polymorphisms and Alzheimer's disease in an Italian cohort.

Tumor necrosis factor-alpha (TNF-alpha) is a pro-inflammatory cytokine that plays an important role in the inflammatory process that can be observed in Alzheimer's disease (AD) brain. Different functional promoter polymorphisms within genes modulating inflammation have been demonstrated to elevate the AD risk; thus, we studied five common variations within the promoter region of the TNF-alpha gene in 609 subjects (253 AD patients and 356 controls). No positive associations were found, confirming the greater part of previous studies. Moreover, we also investigated the combined haplotypes of the five different polymorphisms without finding a positive association. Thus, the present investigation does not support the proposal that common nucleotide variations in the TNF-alpha gene can influence the development of AD at least in Italian population.

KIBRA gene variants are associated with episodic memory performance in subjective memory complaints.

The KIBRA gene encodes a cytoplasmatic protein, a member of the signal transduction protein family, expressed mainly in the brain. Recent studies have implicated the involvement of a genetic variation in the KIBRA gene (T allele) in human memory in normal subjects and in the risk of developing Alzheimer's disease (AD). We report here the distribution of the KIBRA genetic variant and the Apolipoprotein E (ApoE) epsilon4 allele and their association with neuropsychological measures in older adults reporting problems with everyday memory (subjective memory complaints, SMC). We found that SMC subjects with the CT/TT genotype performed more poorly than those with the CC genotype on long-term memory tests. Thus, in our opinion, these data suggest that the KIBRA genotype could affect memory performance in a different way in those that complain of memory deficits compared to those that do not.

Interleukin-10 promoter polymorphisms influence susceptibility to ulcerative colitis in a gender-specific manner.

OBJECTIVE: Pathological evidence supports a potential role of the pro- and anti-inflammatory cytokine network in the pathogenesis of inflammatory bowel disease (IBD). Moreover, associated studies suggest a possible involvement of cytokine-related genes in IBD susceptibility. In this study, we evaluated the effect of the anti-inflammatory interleukin-10 (IL10) gene on ulcerative colitis (UC). MATERIAL AND METHODS: Two functional single nucleotide polymorphisms (-1082 G/A, -819 T/C) in the IL10 promoter in 203 Italian sporadic UC patients and 391 controls were determined using high-resolution melting analysis. RESULTS: The frequency of the -1082A allele was significantly higher in the UC patients than in controls (p=0.00003); -1082 genotype frequencies were also significantly different between UC patients and controls (p=0.0001). Allele and genotype frequencies of -819 T/C were not significantly associated with UC. Furthermore, the frequencies of haplotypes -1082A/-819C and -1082A/-819T, which have been reported to have a lower promoter activity, were significantly higher in UC patients than in controls (p=0.0004). After gender stratification, we found a significant difference in the -1082A allele (p=0.00004) and genotype (p=0.0002) frequencies only between female UC patients and controls; the same result was obtained for the -1082A/-819C and -1082A/-819T haplotypes (p=0.0006). CONCLUSIONS: A gender effect is observed, with women of AG/AA IL10 genotypes and AC/AT haplotypes having a higher risk of developing UC at a younger age. This finding could be related to the previously documented lower IL10 production associated with the -1082A allele and to the IL10 down-regulating effect of estrogens.

Mutational screening analysis of DHCR24/seladin-1 gene in Italian familial Alzheimer's disease.

There is evidence that both environmental and genetic factors may play a role in the pathogenesis of Alzheimer's disease (AD). The amount of brain cholesterol, for instance, has been suggested to play a role in the development of the disease. Accordingly, the Apolipoprotein E (ApoE) epsilon4 allele has been identified as a major risk factor for the occurrence of AD. The product of the DHCR24/seladin-1 gene has enzymatic activity, which converts desmosterol into cholesterol. The expression of this gene, which confers protection against beta-amyloid toxicity and from oxidative stress, is downregulated in AD vulnerable brain regions and it has been proposed as possibly involved in the pathogenesis of this disease. In this study, we evaluated the possible genetic contribution of the DHCR24/seladin-1 gene to Italian familial cases of AD. The exons 1-9 of this gene from 100 patients were subjected to mutation screening analysis. We identified a new C to T transition in exon 1 (Leu60Leu) and a previously described C to T transition in exon 7 (Ile342Ile-rs718265). Our preliminary results suggest the absence of an association between DHCR24/seladin-1 genotypes and AD in the Italian population.

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.

Association of IL10 promoter polymorphism in Italian Alzheimer's disease.

Recent studies have reported a genetic association between single nucleotide polymorphisms (SNPs) in the promoter region of Interleukin (IL) 10 and Alzheimer's disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of cytokines as a potential cause for AD susceptibility, we analyzed genotypes, allele distributions and haplotypes of IL10 promoter polymorphisms -1082 (rs1800896) and -819 (rs1800871) in an Italian sample of 222 sporadic AD patients and 179 normal controls. All 401 subjects were also genotyped for the Apolipoprotein E (ApoE) polymorphism. We reported a positive association between the -819T/C polymorphism and AD. Moreover, we found a significant difference for this SNP in the ApoE varepsilon4 non-carrier AD patients compared to the ApoE varepsilon4 non-carrier control group. For the -1082A genotype and allele distribution, no significant association was found in AD patients, although it was detected within the AT haplotype. Our results indicate that IL10 polymorphisms may be involved in the risk of developing AD.

Angiotensin converting enzyme insertion/deletion polymorphism in sporadic and familial Alzheimer's disease and longevity.

A recent, large meta-analysis has reproposed the role of the angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism as a risk factor for Alzheimer's disease (AD). To further investigate the proposed association and to better clarify the role of ACE as a risk factor for AD, we analyzed the genotype and allele frequency distribution of ACE I/D and apolipoprotein E (APOE) gene polymorphisms in 235 Italian patients with sporadic AD, 153 with familial AD (FAD), 192 healthy controls and 111 centenarians. Patients with AD were consecutively gathered from among the outpatients from the Neurology Department at the University of Florence. All 691 subjects were genotyped for ACE and APOE polymorphisms. There were no significant differences in ACE genotypes or allele frequencies in all the studied groups, even after stratification for APOE epsilon4 carrier status. Centenarians show the highest allele D frequency, although the value is not significant, thus suggesting a possible implication of the D allele as an epistatic allele that has pleiotropic age-dependent effects. In conclusion, our data suggest that the ACE allelic variant is not a susceptibility factor in sporadic and familial AD (FAD), nor does it mitigate the effect of the APOE epsilon4 allele in the risk of developing AD. Moreover, our data do not suggest a possible involvement of the D allele in longevity.

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.

The novel PSEN1 M84V mutation associated to frontal dysexecutive syndrome, spastic paraparesis, and cerebellar atrophy in a dominant Alzheimer's disease family.

We identified the novel PSEN1 pathogenic mutation M84V in 3 patients belonging to a large kindred affected by autosomal dominant Alzheimer's disease (AD). The clinical phenotype was characterized by early onset dementia in 14 affected subjects over 3 generations. Detailed clinical, imaging and genetic assessment was performed. We highlighted the presence of unusual symptoms such as frontal executive syndrome, psychosis and spastic paraparesis in these patients. Spastic paraparesis has been reported in other PSEN1 mutations in adjacent codons, suggesting that the position of the genetic defect may affect the clinical expression, although this phenotype can occur in mutations throughout the whole PSEN1 gene. Brain magnetic resonance imaging showed diffuse cortical atrophy, but also atrophy of cerebellar lobules, mainly involving Crus I, in 2 patients without cerebellar motor deficits. These neuroimaging results were consistent with recent findings about the association between sporadic AD and distinct and circumscribed cerebellar atrophy. The present work acknowledged the novel PSEN1 pathogenic mutation M84V and might contribute to the ongoing debate about the involvement of cerebellum in AD.

Fragile X premutation with atypical symptoms at onset.

OBJECTIVE: To evaluate the presence of carriers of the fragile X premutation among male patients with sporadic ataxia without expansion into known spinocerebellar ataxia genes. DESIGN: Clinical and genetic examinations were performed on patients with sporadic pure ataxia and patients with ataxia associated with extracerebellar features such as pyramidal and extrapyramidal signs, dementia, or peripheral neuropathy. SETTING: University department of neurology. PATIENTS: One hundred forty-two Italian men with sporadic ataxia with onset at age 30 to 84 years. INTERVENTIONS: The CGG repeat size of the FMR1 gene was evaluated with fluorescent polymerase chain reaction. Premutated allele lengths were confirmed with Southern blot analysis. RESULTS: FMR1 premutation alleles with a repeat number greater than 55 were detected in 3 probands (2.1%) from a total of 142 male subjects initially referred to our university medical center for evaluation of sporadic ataxia. Two patients had typical fragile X syndrome with associated tremor or ataxia, and the third patient had spastic paraparesis without clear symptoms of cerebellar ataxia and without the common signs seen at magnetic resonance imaging. CONCLUSIONS: Genetic analysis of the FMR1 gene could provide a reliable diagnostic tool for the definitive diagnosis of late-onset ataxias. Additional studies are needed to clarify the importance of premutation screening in patients with movement disorders or other associated atypical features at onset, such as paraparesis.

Association analysis of the paraoxonase-1 gene with Alzheimer's disease.

Genetic variants in the paraoxonase (PON) gene cluster, particularly a single C/T promoter polymorphism (rs 705381) in the PON-1 gene, have recently been associated with Alzheimer's disease (AD). The T allele, in particular, presents an increased risk for the development of AD. Here, we investigate the potential role of this polymorphism in an Italian case-control population consisting of 306 sporadic AD patients and 275 controls, and also evaluate a possible interaction with the ApoE genotype. No association between the PON-1 polymorphism and AD was observed. The T allele frequency was slightly over-represented in AD patients compared to the controls, but this was far from being statistically significant. Our sample was evaluated to have 97.3% power to detect an OR of 2.0 (64.3% power with OR=1.5) at an alpha level of 0.05. No evidence of an interaction between the T risk-allele and the ApoE epsilon4 allele status and no effect of the PON-1 polymorphism on age at onset was detected. Our results do not support other studies indicating that the PON-1 promoter polymorphism plays a major role in AD, suggesting that other large studies are necessary to further elucidate the effect of PON on the development of the disease in the general population.

Cystatin C and apoe polymorphisms in Italian Alzheimer's disease.

Recent studies have reported a genetic association between the 73 G/A polymorphism within exon 1 of the cystatin C gene and Alzheimer's disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of CST3 as risk factor for AD, we analyzed the genotype and allele frequency distribution of CST3 G73A and apolipoprotein (ApoE) gene polymorphisms in 243 Italian patients with AD and 186 controls. Patients with AD were consecutively collected among the outpatients from the Neurology Department at the University of Florence. All 429 subjects were genotyped for CST3 and ApoE polymorphisms. After stratification according to age, the GG frequency resulted slightly higher in younger (<65 years) cases, but far from statistically significant. There was also no evidence of a statistical interaction between CST3 and ApoE polymorphisms. In conclusion, our data suggest that the CST3 genetic variant is not a susceptibility factor in AD, nor mitigate the effect of the ApoE varepsilon4 allele in the risk of developing AD.