Ana Pozueta

Detection of early Alzheimer's disease in MCI patients by the combination of MMSE and an episodic memory test.

BackgroundMild cognitive impairment (MCI) is a heterogeneous clinical entity that comprises the prodromal phase of Alzheimers disease (Pr-AD). New biomarkers are useful in detecting Pr-AD, but they are not universally available. We aimed to investigate baseline clinical and neuropsychological variables that might predict progression from MCI to AD dementia.MethodsAll patients underwent a complete clinical and neuropsychological evaluation at baseline and every 6 months during a two-year follow-up period, with 54 out of 109 MCI patients progressing to dementia (50 of them progressed to AD dementia), and 55 remaining as stable MCI (S-MCI).ResultsA combination of MMSE and California Verbal Learning Test Long Delayed Total Recall (CVLT-LDTR) constituted the best predictive model: subjects scoring above 26/30 on MMSE and 4/16 on CVLT-LDTR had a negative predictive value of 93.93% at 2 years, whereas those subjects scoring below both of these cut-off scores had a positive predictive value of 80.95%.ConclusionsPr-AD might be distinguished from S-MCI at baseline using the combination of MMSE and CVLT-LDTR. These two neuropsychological predictors are relatively brief and may be readily completed in non-specialist clinical settings.

Relationship between cortical thickness and cerebrospinal fluid YKL-40 in predementia stages of Alzheimer's disease

Cerebrospinal fluid YKL-40 has been described as a marker of glial inflammation. We aimed to study the relationship between YKL-40 and brain structure and its interactions with core Alzheimers disease (AD) biomarkers. We measured cortical thickness (CTh) and cerebrospinal fluid biomarkers (amyloid-β 1-42 [Aβ42], total tau, p-tau, and YKL-40) of 80 cognitively normal controls and 27 patients with amnestic mild cognitive impairment. Subjects were classified as Aβ42+ (<550 pg/mL) or Aβ42- (>550 pg/mL). CTh difference maps were derived from the interaction and correlation analyses in the whole sample and within clinical groups. There was a strong correlation between YKL-40 and markers of neurodegeneration (total tau and p-tau). In the whole sample, we found a negative correlation between YKL-40 and CTh in AD vulnerable areas in Aβ42+ subjects but not in Aβ42 participants. Our results suggest that YKL-40 could track the inflammatory processes associated to tau-related neurodegeneration in the presence of the AD pathophysiological process.

Epistasis between intracellular cholesterol trafficking-related genes (NPC1 and ABCA1) and Alzheimer's disease risk

Aberrant cholesterol metabolism has been implicated in Alzheimers disease (AD). Recent findings have suggested an interaction of Niemann-Pick C1 (NPC1) and ATP-binding cassette transporter A1 (ABCA1) proteins in intracellular cholesterol transport and in maintaining cell cholesterol balance. Underexpression of NPC1 in concert with under-expression of ABCA1 would result in increased cholesterol accumulation and increased AD risk. We examined a functional polymorphism in the ABCA1 promoter region (-477, rs2422493), and four NPC1 polymorphisms in exon 6 (rs18050810), intron 20 (rs4800488), intron 22 (rs2236707), and intron 24 (rs2510344) capturing 85% of genetic variability in the Hap Map Caucasian (CEU) population, in a group of 631 Spanish AD patients and 731 controls. Subjects carrying both the ABCA1 (-477) TT genotype and the NPC1 (exon 6) GG genotype (OR=1.89; 95% CI 1.04-3.41), NPC1 (intron 20) AA genotype (OR=2.05; 95% CI 1.26-3.33), NPC1 (intron 22) AA genotype (OR=2.05; 95% or NPC1 (intron 24) GG genotype (OR=1.89; 95% higher risk of developing AD than subjects without these risk genotypes. Testing for epistatic interaction between genes in the pathway of cholesterol metabolism might be useful for predicting AD risk.

Genetic variations in tau-tubulin kinase-1 are linked to Alzheimer's disease in a Spanish case-control cohort

Neurofibrillary tangles, one of the characteristic neuropathological lesions found in Alzheimers disease (AD) brains, are composed of abnormally hyperphosphorylated tau protein. Tau-tubulin kinase-1 (TTBK1) is a brain-specific protein kinase involved in tau phosphorylation at AD-related sites. We examined genetic variations of TTBK1 by genotyping nine haplotype tagging SNPs (htSNPs) (rs2104142, rs2651206, rs10807287, rs7764257, rs3800294, rs1995300, rs2756173, rs6936397, and rs6458330) in a group of 645 Spanish late-onset AD patients and 738 healthy controls. Using a recessive genetic model, minor allele homozygotes for rs2651206 in intron 1 (OR=0.50, p=0.0003), rs10807287 in intron 5 (OR=0.49, p=0.0002), and rs7764257 in intron 9 (OR=0.57, p=0.023), which are in strong linkage disequilibrium, had a lower risk of developing AD than subjects homozygotes and heterozygotes for the major allele. TTBK1 is a promising new candidate tau phosphorylation-related gene for AD risk.

Genetic Interaction between Tau and the Apolipoprotein E Receptor LRP1 Increases Alzheimer’s Disease Risk

Abnormal tau hyperphosphorylation is one of the central events in the development of neurofibrillary tangles (NFTs) in Alzheimer’s disease (AD), and phosphorylation of tau is accelerated by the increase in the level of neuronal cholesterol. Apolipoprotein E (APOE) promotes the neuronal uptake of cholesterol via APOE receptors such as the low-density lipoprotein receptor-related protein 1 (LRP1), and the APOE ε4 allele is associated with an increase in NFT burden in AD brain. In a case-control study in 246 AD patients and 237 healthy controls, we examined whether the combined gene effects between tau (intron 9, rs2471738) polymorphism and LRP1 (exon 3, rs1799986) polymorphism might be responsible for susceptibility to AD, independently or in concert with the APOE ε4 allele. Subjects carrying both the tau (intron 9, rs2471738) T allele (CT and TT genotypes) and the LRP1 (exon 3, rs1799986) T allele (CT and TT genotypes) had a 6 times higher risk of developing AD than subjects without these risk genotypes (odds ration = 6.20, 95% confidence interval = 1.74–22.05, p = 0.005), and this genetic interaction was observed in either the presence or the absence of the APOE ε4 allele. These data suggest that the synergistic effects (epistasis) between tau and LRP1 might modify the risk of AD in an APOE ε4 allele-independent fashion.

MicroRNA Profile in Patients with Alzheimer’s Disease: Analysis of miR-9-5p and miR-598 in Raw and Exosome Enriched Cerebrospinal Fluid Samples

BACKGROUND MicroRNAs have been postulated as potential biomarkers for Alzheimers disease (AD). Exosomes are nanovesicles which transport microRNAs, proteins, and other cargos. It has been hypothesized that the exosome traffic might be increased in neurodegenerative disorders. OBJECTIVE i) To assess the cerebrospinal fluid (CSF) microRNA profile in a group of AD patients and control subjects and to validate a group of microRNAs previously reported by other authors. ii) To compare microRNA levels in whole CSF and in the exosome-enriched fraction in AD patients. METHODS A panel of 760 microRNAs was analyzed in the CSF of 10 AD patients and 10 healthy subjects. Among microRNAs differently expressed, we selected those that had been previously reported by other authors. Candidates were validated in a larger group by individual qPCR assays. MicroRNA expression was also evaluated in exosome-enriched CSF samples of patients with AD and controls. RESULTS Fifteen microRNAs were differently expressed in AD. MiR-9-5p, miR-134, and miR-598 were selected as candidates for further analysis. MiR-9-5p and miR-598 were detected in 50 and 75% of control CSF samples, respectively, while they were not detected in any AD CSF samples. We observed an opposite pattern when we evaluated the microRNA expression in the exosome-enriched CSF AD samples. No pattern variations were noted among healthy subjects. CONCLUSION These data propose miR-9-5p and miR-598 as potential biomarkers for AD. Further studies in plasma and other body fluids will confirm their potential role as easily accessible biomarkers. In addition, our data suggest that exosome trafficking is different between AD and control subjects raising the need to take this phenomenon into consideration in future studies of AD biomarkers.

Genetic variation in the tau protein phosphatase- 2A pathway is not associated with Alzheimer's disease risk

BackgroundTau abnormal hyperphosphorylation and the formation of neurofibrillary tangles in AD brain is the result of upregulation of tau kinases and downregulation of tau phosphatases.MethodsIn a group of 729 Spanish late-onset Alzheimers disease (AD) patients and 670 healthy controls, we examined variations into a set of candidate genes (PPP2CA, PPP2R2A, ANP32A, LCMT1, PPME1 and PIN1) in the tau protein phosphatase-2A (PP2A) pathway, to address hypotheses of genetic variation that might influence AD risk.ResultsThere were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by age, gender or APOE ε4 allele.ConclusionOur negative findings in the Spanish population argue against the hypothesis that genetic variation in the tau protein phosphatase-2A (PP2A) pathway is causally related to AD risk

DYRK1A genetic variants are not linked to Alzheimer's disease in a Spanish case-control cohort

BackgroundAs dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) has been implicated in the abnormal hyperphosphorylation of tau in Alzheimers disease (AD) brain, and the development of neurofibrillary tangles, we examined the contribution of this gene to the susceptibility for AD.MethodsWe examined genetic variations of DYRK1A by genotyping haplotype tagging SNPs (htSNPs) (rs11701483, rs2835740, rs1137600, rs2835761, rs2835762, rs2154545 and rs8132976) in a group of 634 Spanish AD cases and 733 controls.ResultsThere were no differences in the genotypic, allelic or haplotypic distributions between cases and controls in the overall analysis or after stratification by APOE ε4 allele.ConclusionOur negative findings in the Spanish population argue against the hypothesis that DYRK1A genetic variations are causally related to AD risk. Still, additional studies using different sets of patients and control subjects deserve further attention, since supporting evidence for association between DYRK1A gene and AD risk in the Japanese population exists.

Genetic variation in caspase-1 as predictor of accelerated progression from mild cognitive impairment to Alzheimer's disease

There has been a lot of interest in the detection of predictors of conversion from mild cognitive impairment (MCI) to Alzheimer’s disease (AD) using neuroimaging methods, CSF biomarkers and cognitive tests [2]. Despite the many genetic studies of AD, there has been little research directed toward determining the influence of genetic variation on progression from MCI to AD [1, 4]. Variation in the caspase-1 (CASP1) gene has been evaluated in both cognitive function in elderly individuals with normal cognition [5] and in predisposition to AD [6], but no previous study has specifically explored the association between genetic variation in CASP1 and progression from MCI to AD. As a primary goal in this study, we investigate APOE e4 allele and CASP1 (rs580253) polymorphisms in order to predict MCI individuals likely to convert to AD in a relatively short follow-up period. Between 2007 and 2009, we examined 84 consecutive patients who attended the Department of Neurology of University Hospital ‘‘Marques de Valdecilla’’ (Santander, Spain) and that fulfilled the Petersen criteria for amnestic MCI [3]. Patients with MCI were longitudinally assessed at 6-month intervals (mean duration of follow-up 26.5 months; SD 8.1; range 7–37 months). According to their Clinical Dementia Rating (CDR) scores during the follow-up period, 50 MCI patients whose global CDR score changed from CDR = 0.5 to CDR = 1 were diagnosed as MCI-converters to AD (70% women; mean age 76.3 years; SD 5.7; range 60–85 years), and two additional MCI patients converted to dementia with Lewy bodies and vascular dementia, respectively; 32 MCI whose global CDR score remained stable were classified as MCI-nonconverters to AD (63% women; mean age 74.8 years; SD 7.0; range 60–86 years). Except one MCI-converter to AD patient with a minimal follow-up period of 7 months, the rest of our patients were followed up for at least 1 year to avoid the risk to label as MCI-non-converter to AD subjects who will develop dementia over time. We selected the CASP1 gene (rs580253) polymorphism that had been previously related to cognitive function [5]. Blood samples were taken after written informed consent had been obtained from the subjects or their representatives. The study was approved by the ethical committee of the University Hospital ‘‘Marques de Valdecilla’’. Kaplan–Meier curves and Cox regression model (including APOE status, age and gender) were used to assess whether timeto-conversion was associated with CASP1 (rs580253) polymorphism. Kaplan–Meier survival analysis (Fig. 1), shows the effect of APOE e4 allele and CASP1 (rs580253) T allele on the time-to-conversion to AD in patients with MCI. Survival function estimates did not differ significantly between APOE e4 allele carriers and non-carriers. Conversely, the mean time of conversion from MCI to AD was 25.2 months (SD 9.1) in people with CASP1 (rs580253) T allele (CT and TT genotypes) versus 31.7 months (SD 7.4) in CASP1 (rs580253) T allele non-carriers (CC genotype); thus, CASP1 (rs580253) T allele accelerated the progression from MCI to AD by an average of 6.5 months (P = 0.009). The risk factors of conversion from MCI to AD were analyzed simultaneously with a multivariate Cox A. Pozueta J. L. Vazquez-Higuera P. Sanchez-Juan E. Rodriguez-Rodriguez C. Sanchez-Quintana I. Mateo J. Berciano O. Combarros (&) Neurology Service and CIBERNED, University Hospital ‘‘Marques de Valdecilla’’ (University of Cantabria), 39008 Santander, Spain e-mail: combarro@unican.es

Binge Drinking in Young University Students Is Associated with Alterations in Executive Functions Related to Their Starting Age.

Our aim was to evaluate whether or not alcohol consumption in the form of binge drinking is associated with alterations of memory and executive functions in a population of university students. At the same time, we have studied the role of potential modulating factors, such as the APOE genotype or physical exercise.University students enrolled in academic year 2013–2014 at Escuelas Universitarias Gimbernat-Cantabria, affiliated with the University of Cantabria, were invited to participate in the study. We gathered sociodemographic data and details regarding the lifestyle of 206 students (mean age 19.55 ± 2.39; 67.5% women). We evaluated memory and executive functions via a series of validated cognitive tests. Participants were classified as binge drinkers (BD) and non-BD. Using Students t-distribution we studied the association between cognitive tests and BD patterns. Multivariate analyses were carried out via multiple linear regression. 47.6% of the students were found to be BD. The BD differed significantly from the non-BD in their results in the executive functions test TMT B (43.41 ± 13.30 vs 37.40 ± 9.77; p = 0.0003). Adjusting by age, sex, academic records, age at which they started consuming alcohol, cannabis consumption, level of physical activity and other possible modifying variables, the association was statistically significant (p = 0.009). We noticed a statistically significant inverse correlation (Pearson’s r2 = -0.192; p = 0.007) between TMT B and starting age of alcohol consumption. Differences were observed in another executive functions test, TMT A, but only in the group of women (19.73±6.1 BD vs 17.78±5.4 non-BD p = 0.05). In spite of the young age of our participants, BD was associated with a lower performance in the executive functions test (TMT B). These deficits were related to the age at which they started drinking alcohol, suggesting an accumulative effect.