Prevalence of Alzheimer's disease and vascular dementia: association with education. The Rotterdam study.

OBJECTIVE--To estimate the prevalence of dementia and its subtypes in the general population and examine the relation of the disease to education. DESIGN--Population based cross sectional study. SETTING--Ommoord, a suburb of Rotterdam. SUBJECTS--7528 participants of the Rotterdam study aged 55-106 years. RESULTS--474 cases of dementia were detected, giving an overall prevalence of 6.3%. Prevalence ranged from 0.4% (5/1181 subjects) at age 55-59 years to 43.2% (19/44) at 95 years and over. Alzheimer''s disease was the main subdiagnosis (339 cases; 72%); it was also the main cause of the pronounced increase in dementia with age. The relative proportion of vascular dementia (76 cases; 16%), Parkinson''s disease dementia (30; 6%), and other dementias (24; 5%) decreased with age. A substantially higher prevalence of dementia was found in subjects with a low level of education. The association with education was not due to confounding by cardiovascular disease. CONCLUSIONS--The prevalence of dementia increases exponentially with age. About one third of the population aged 85 and over has dementia. Three quarters of all dementia is due to Alzheimer''s disease. In this study an inverse dose-response relation was found between education and dementia--in particular, Alzheimer''s disease.     

Sequence variation in the CHAT locus shows no association with late-onset Alzheimer's disease

There is substantial evidence for a susceptibility gene for late-onset Alzheimer's disease (AD) on chromosome 10. One of the characteristic features of AD is the degeneration and dysfunction of the cholinergic system. The genes encoding choline acetyltransferase (ChAT) and its vesicular transporter (VAChT), CHAT and SLC18A3 respectively, map to the linked region of chromosome 10 and are therefore both positional and obvious functional candidate genes for late-onset AD. We have screened both genes for sequence variants and investigated each for association with late-onset AD in up to 500 late-onset AD cases and 500 control DNAs collected in the UK. We detected a total of 17 sequence variants. Of these, 14 were in CHAT, comprising three non-synonymous variants (D7N in the S exon, A120T in exon 5 and L243F in exon 8), one synonymous change (H547H), nine single-nucleotide polymorphisms in intronic, untranslated or promoter regions, and a variable number of tandem repeats in intron 7. Three non-coding SNPs were detected in SLC18A3. None demonstrated any reproducible association with late-onset AD in our samples. Levels of linkage disequilibrium were generally low across the CHAT locus but two of the coding variants, D7N and A120T, proved to be in complete linkage disequilibrium.     

Occludin is overexpressed in Alzheimer's disease and vascular dementia

The tight junctions (TJs) are key players in the control of blood-brain barrier (BBB) properties, the most complex TJs in the vascular system being found in the endothelial cells of brain capillaries. One of the main TJs proteins is occludin, which anchors plasma membranes of neighbour cells and is present in large amounts in the brain endothelia. Previous studies demonstrated that disruption of BBB in various pathological situations associates with changes in occludin expression, and this change could be responsible for malfunction of BBB. Therefore in this study, applying an immunohistochemical approach, we decided to explore the occludin expression in frontal cortex (FC) and basal ganglia in ageing control, Alzheimer's disease (AD), and vascular dementia (VD) brains, as far as all these pathologies associate microangiopathy and disruption of BBB. Strikingly, we found selected neurons, astrocytes and oligodendrocytes expressing occludin, in all cases studied. To estimate the number of occludin-expressing neurons, we applied a stereological approach with random systematic sampling and the unbiased optical fractionator method. We report here a significant increase in ratio of occludin-expressing neurons in FC and basal ganglia regions in both AD and VD as compared to ageing controls. Within the cerebral cortex, occludin was selectively expressed by pyramidal neurons, which are the ones responsible for cognitive processes and affected by AD pathology. Our findings could be important in unravelling new pathogenic pathways in dementia disorders and new functions of occludin and TJs.     

Substantial linkage disequilibrium across the insulin-degrading enzyme locus but no association with late-onset Alzheimer's disease

Insulin-degrading enzyme (IDE; insulysin; EC 3.4.24.56) is a 110-kDa neutral metallopeptidase that can degrade a number of peptides including beta-amyloid. The gene encoding IDE is located on chromosome 10 close to a region of linkage for late-onset Alzheimer's disease (LOAD) and thus is a functional and positional candidate for this disorder. We analysed all of the coding exons, untranslated regions and 1000 bp of 5'-flanking sequence of IDE by using denaturing high-performance liquid chromatography and sequencing. We detected eight single nucleotide polymorphisms (SNPs), three in the 5' flanking sequence and five in the coding sequence, of which three were found at lower than 5% frequency. None of them changed the amino acid sequence. We genotyped the five SNPs with allele frequencies of more than 5% in 133 Caucasian LOAD cases and 135 controls collected in the UK and 95 cases and 117 controls collected at the Mayo Clinic, Rochester, USA. Two of the SNPs were analysed in a further independent case-control sample (Washington University, St. Louis: 86 cases, 94 controls). No significant association was found with any individual SNP in any of the samples or with any haplotypes. Analysis of the marker D10S583, which maps 36 kb upstream of IDE, also failed to show association in 134 cases and 111 matched controls from the UK ( P=0.63). Strong linkage disequilibrium was detected between the five SNPs that spanned the whole of the 120-kb genomic region of IDE and one major and a number of minor haplotypes were detected in the populations studied. We conclude that IDE does not make a substantial contribution to the aetiology of LOAD and therefore cannot account for the linkage between LOAD and 10q.     

"Closing-in" phenomenon in Alzheimer's disease and subcortical vascular dementia

Background  

The 'closing-in' phenomenon is defined as a tendency to close in on a model while copying it. This is one of several constructional apraxia observed in dementia, particularly in Alzheimer's disease (AD). The aim of this study was to investigate the usefulness of it in the differential diagnosis of AD and subcortical vascular dementia (SVD) and to clarify the factors associated with it.     

Cerebrospinal fluid markers in differential diagnosis of Alzheimer's disease and vascular dementia

Alzheimer's disease (AD) and vascular dementia (VaD) are the two most common causes of dementia in old people. They remain difficult to differentiate in practice because of lack of sensitivity and specificity of current clinical diagnostic criteria. Recent molecular and cellular advancements indicate that the use of cerebrospinal fluid markers may improve early detection and differential diagnosis of AD. Our objective in this study was to determine diagnostic accuracy of three cerebrospinal (CSF) markers: total tau protein (t-tau), tau protein phosphorylated on threonine 181 (p-tau181) and tau protein phosphorylated on serine 199 (p-tau199). Using commercially available ELISA kits concentrations of t-tau, p-tau181 and p-tau199 were analyzed in 12 patients with probable AD, 9 patients with VaD and 12 NC subjects. The median levels of all three markers were significantly higher in AD group versus VaD and NC groups. However, when the sensitivity levels were set to 85% or higher, only t-tau and p-tau199 satisfied consensus recommendations (specificity more than 75%) when differentiating AD from VaD. In conclusion, our preliminary data on a small group of selected subjects suggest that the CSF t-tau and p-tau199 levels are useful markers for differentiating AD from VaD.     

Association between an alpha(2) macroglobulin DNA polymorphism and late-onset Alzheimer's disease.

An association between a five-base-pair deletion/insertion DNA polymorphism at the alpha(2) macroglobulin gene (A2M) and late-onset Alzheimer's disease (LOAD) has been recently described. We developed a PCR assay to analyze this polymorphism in 190 LOAD patients (older than 65 years) and 400 controls from Spain. Controls were stratified into three groups: <65 years (n = 200), 65 to 80 years (n = 100), and 81 years or older (n = 100). We found a significantly higher frequency of carriers of the D allele in patients older than 81 years compared to controls older than 81 years (p = 0.0012). In addition, the frequency of the D allele was significantly lower in controls older than 81 years compared to controls younger than 65 (p = 0.048). Our work suggests that the D allele confers an age-dependent increased risk to develop late-onset Alzheimer's disease.     

Potential therapeutic targets of huperzine A for Alzheimer's disease and vascular dementia

Huperzine A (HupA), a novel Lycopodium alkaloid isolated from Chinese folk medicine Huperzia serrata (Qian Ceng Ta), is a potent, selective and well-tolerated inhibitor of acetylcholinesterase (AChE). It has been proven to significantly improve the learning and memory impairment in Alzheimer's disease (AD) and vascular dementia (VaD) patients in China. Interestingly, our recent data indicate that HupA also possesses other protective functions. This paper will give an overview on the protective effects of HupA, which includes regulating beta-amyloid precursor protein (APP) metabolism, protecting against Abeta-mediated oxidative stress, apoptosis and mitochondrial dysfunction, as well as anti-inflammation. The multiple neuroprotective effects of HupA might yield additional beneficial effects in AD and VaD therapy.     

The association of CLOCK gene T3111C polymorphism and hPER3 gene 54-nucleotide repeat polymorphism with Chinese Han people schizophrenics

Many reports have shown that the biologic rhythm could be altered due to mutations of circadian gene hClock or hPeriod, and the mutations of circadian genes have some relationship with psychosis according to recent studies. A preliminary study has been conducted to examine wether the T3111C single nucleotide polymorphism of the hClock gene or the length polymorphism of the hPer3 gene is associated with the development of schizophrenia. The samples from schizophrenics (n = 148, male: 57.4%, female: 42.6%) and normal controls (n = 199, male: 59.3%, female: 40.7%) were examined. Allele frequencies of T3111C SNP of hClock were significantly different between schizophrenics and controls (χ² = 19.738, P < 0.05). Schizophrenics had a significantly higher frequency of the C allele compared with controls (OR = 2.613, 95% CI = 1.693–4.034). On the other hand, there is no significant difference of allele frequencies of 18 exon of hper3 between schizophrenics and controls (χ² = 0.192, P > 0.05). Our results suggest that the T3111C (RS1801260) polymorphism of hClock gene is associated with schizophrenia, but it seems that the length polymorphism of 18 exon of hPer3 may not be associated with schizophrenia. It is important to address of the relationship between circadian gene polymorphisms and dopamine functions in further study.     

Genetic association of the gene encoding RPGRIP1L with susceptibility to vascular dementia

A previous genome-wide association study (GWAS) failed to discover any nucleotide sequence variant associated with susceptibility to vascular dementia (VaD) and remained a problem of false negatives produced by a low statistical power. The current study was conducted to identify such potential false negatives and to provide comprehensive evidence for the most plausible predisposing genetic factor using large-scale Korean cohorts. We identified the gene encoding retinitis pigmentosa GTPase regulator-interacting protein 1-like (RPGRIP1L) with multiple nucleotide variants associated with susceptibility to VaD by a modest significant threshold (P<10(-4)). Genetic associations were intensively examined with its sequence variants using 207 VaD patients and 207 age- and gender-matched control subjects. Genetic association analysis with dense variants in the region associated with VaD revealed 3 variants (P<0.0017) in strong linkage. Further analysis with VaD-related phenotypes using Korean Association REsource (KARE) cohort data showed that the region of the gene was associated with alanine aminotransferase (ALT), aspartate aminotransferase (AST), and blood pressure (BP) (P<7.6×10(-4)). The current study provided the first evidence of the association between RPGRIP1L gene and susceptibility of VaD. Functional studies are needed to understand underlying biological mechanism of the genetic association.     

ACE gene polymorphism in peripheral vascular disease.

Peripheral vascular disease is an atherosclerotic process. It has been suggested that angiotensin converting enzyme insertion/deletion polymorphism is associated with atherosclerosis. The aim of this study was to investigate the role of the insertion/deletion polymorphism of the angiotensin-converting enzyme in Turkish patients with peripheral vascular disease in Western part of Turkey. We also investigated the relationship between serum angiotensin converting enzyme activity and distribution of genotypes in both patients and control group. The study group consisted of 78 patients with peripheral vascular disease. The control group consisted of 73 healthy adults. Serum angiotensin converting enzyme activities in patients were higher than those of the control group (p<0.05). Angiotensin converting enzyme genotype frequencies in patients were observed as 28.2%, 18% and 53.8% for DD, II and ID polymorphism, respectively. These frequencies in controls were 42.5%, 20.5% and 37% for DD, II and ID, respectively. Serum angiotensin converting enzyme activities in both groups with II genotype were significantly lower than those with ID and DD genotype (p<0.05). Although conflicting results have been reported about this polymorphism in patients with peripheral vascular disease, we suggest that the angiotensin converting enzyme ID genotype may be a risk factor for peripheral vascular disease.     

Meta-analysis for genome-wide association study identifies multiple variants at the BIN1 locus associated with late-onset Alzheimer's disease

Recent GWAS studies focused on uncovering novel genetic loci related to AD have revealed associations with variants near CLU, CR1, PICALM and BIN1. In this study, we conducted a genome-wide association study in an independent set of 1034 cases and 1186 controls using the Illumina genotyping platforms. By coupling our data with available GWAS datasets from the ADNI and GenADA, we replicated the original associations in both PICALM (rs3851179) and CR1 (rs3818361). The PICALM variant seems to be non-significant after we adjusted for APOE e4 status. We further tested our top markers in 751 independent cases and 751 matched controls. Besides the markers close to the APOE locus, a marker (rs12989701) upstream of BIN1 locus was replicated and the combined analysis reached genome-wide significance level (p = 5E-08). We combined our data with the published Harold et al. study and meta-analysis with all available 6521 cases and 10360 controls at the BIN1 locus revealed two significant variants (rs12989701, p = 1.32E-10 and rs744373, p = 3.16E-10) in limited linkage disequilibrium (r² = 0.05) with each other. The independent contribution of both SNPs was supported by haplotype conditional analysis. We also conducted multivariate analysis in canonical pathways and identified a consistent signal in the downstream pathways targeted by Gleevec (P = 0.004 in Pfizer; P = 0.028 in ADNI and P = 0.04 in GenADA). We further tested variants in CLU, PICALM, BIN1 and CR1 for association with disease progression in 597 AD patients where longitudinal cognitive measures are sufficient. Both the PICALM and CLU variants showed nominal significant association with cognitive decline as measured by change in Clinical Dementia Rating-sum of boxes (CDR-SB) score from the baseline but did not pass multiple-test correction. Future experiments will help us better understand potential roles of these genetic loci in AD pathology.     

Genome-wide association of familial late-onset Alzheimer's disease replicates BIN1 and CLU and nominates CUGBP2 in interaction with APOE

Late-onset Alzheimer''s disease (LOAD) is the most common form of dementia in the elderly. The National Institute of Aging-Late Onset Alzheimer''s Disease Family Study and the National Cell Repository for Alzheimer''s Disease conducted a joint genome-wide association study (GWAS) of multiplex LOAD families (3,839 affected and unaffected individuals from 992 families plus additional unrelated neurologically evaluated normal subjects) using the 610 IlluminaQuad panel. This cohort represents the largest family-based GWAS of LOAD to date, with analyses limited here to the European-American subjects. SNPs near APOE gave highly significant results (e.g., rs2075650, p = 3.2×10⁻⁸¹), but no other genome-wide significant evidence for association was obtained in the full sample. Analyses that stratified on APOE genotypes identified SNPs on chromosome 10p14 in CUGBP2 with genome-wide significant evidence for association within APOE ε4 homozygotes (e.g., rs201119, p = 1.5×10⁻⁸). Association in this gene was replicated in an independent sample consisting of three cohorts. There was evidence of association for recently-reported LOAD risk loci, including BIN1 (rs7561528, p = 0.009 with, and p = 0.03 without, APOE adjustment) and CLU (rs11136000, p = 0.023 with, and p = 0.008 without, APOE adjustment), with weaker support for CR1. However, our results provide strong evidence that association with PICALM (rs3851179, p = 0.69 with, and p = 0.039 without, APOE adjustment) and EXOC3L2 is affected by correlation with APOE, and thus may represent spurious association. Our results indicate that genetic structure coupled with ascertainment bias resulting from the strong APOE association affect genome-wide results and interpretation of some recently reported associations. We show that a locus such as APOE, with large effects and strong association with disease, can lead to samples that require appropriate adjustment for this locus to avoid both false positive and false negative evidence of association. We suggest that similar adjustments may also be needed for many other large multi-site studies.     

血清胱抑素C与2型糖尿病下肢血管病变的相关性研究

目的:探讨血清胱抑素C(Cys C)与2型糖尿病下肢血管病变的关系。方法:采用下肢动脉彩色多普勒超声筛查我院内分泌科糖尿病住院患者100例,糖尿病有下肢血管病变者(PVD)50例,糖尿病无下肢血管病变者(NPVD)50例;正常人(NC)40例。测定血清胱抑素C浓度、血脂等指标,并测定其临床一般资料,记录身高、体重等。结果:糖尿病合并PVD组血清Cys C水平明显高于无PVD、NC组,差异有统计学意义(P0.05),且糖尿病无PVD组与NC组相比,糖尿病无PVD组血清Cys C水平也高于NC组,差异也有统计学意义(P0.05)。2型糖尿病有PVD与Cys C、糖尿病病程(Course)、血糖(FBG)、年龄(Age)相关(P0.01)。多元Logistic回归分析显示胱抑素C、病程、年龄是PVD的危险因素。结论:2型糖尿病并PVD的发生与发展除了与病程、年龄有关外,还可能与胱抑素C有关。     

Plasma 24S-hydroxycholesterol levels in elderly subjects with late onset Alzheimer's disease or vascular dementia: a case-control study

Background  

In central nervous system cholesterol cannot be degraded but is secreted into circulation predominantly in the form of its polar metabolite 24(S)-hydroxycholesterol (24S-OH-Chol). Some studies suggested an association between 24S-OH-Chol metabolism and different neurological diseases including dementia. A possible decrease in 24S-OH-Chol plasma levels has been reported late onset Alzheimer's disease (LOAD) and vascular dementia (VD), but results of previous studies are partially contradictory.     

VEGF gene polymorphism association with diabetic neuropathy

Vascular factors beside metabolic problems are involved in both etiopathogenesis of diabetic neuropathy, and more remarkably, later in “repair” phase, that governs the net balance between neuro-regenerative/degenerative reactions. Regarding ischemic nature of diabetic neuropathy that highlights necessity of blood vessels re-establishment during tissue healing, VEGF (vascular endothelial growth factor) has been recently the subject of extensive investigations in diabetic neuropathy (DNU). This growth factor possesses angiogenic potentials in addition to the hemodynamic functions. The distribution of VEGF gene polymorphisms at positions −7*C/T, −1001*G/C, −1154*G/A and −2578*C/A were analysed by ARMS–PCR in 248 type 1 diabetic British-Caucasian subjects (81 DNU+, 167 DNU−). We have found that distribution of a VEGF gene polymorphism at promoter region (−7*C/T) was significantly different between diabetic subjects with vs. without neuropathy and the allele (C) conferred susceptibility to DNU (P = 0.02; OR = 1.78, 95% CI 1.0–3.1). The present study indicates that polymorphism of the VEGF gene at position −7*C/T might be implicated in the pathogenesis of diabetic neuropathy as it may harbour some functional/regulatory potential in VEGF gene expression. However, this requires further studies in order to better understand its phenotypic impact and to investigate the prognostic value of this polymorphism in diabetic neuropathy as a chronic complication of diabetes.     

Comprehensive analysis of APOE and selected proximate markers for late-onset Alzheimer's disease: patterns of linkage disequilibrium and disease/marker association

The epsilon(4) allele of APOE confers a two- to fourfold increased risk for late-onset Alzheimer's disease (LOAD), but LOAD pathology does not all fit neatly around APOE. It is conceivable that genetic variation proximate to APOE contributes to LOAD risk. Therefore, we investigated the degree of linkage disequilibrium (LD) for a comprehensive set of 50 SNPs in and surrounding APOE using a substantial Caucasian sample of 1100 chromosomes. SNPs in APOE were further molecularly haplotyped to determine their phases. One set of SNPs in TOMM40, roughly 15 kb upstream of APOE, showed intriguing LD with the epsilon(4) allele and was strongly associated with the risk for developing LOAD. However, when all the SNPs were entered into a logit model, only the effect of APOE epsilon(4) remained significant. These observations diminish the possibility that loci in the TOMM40 gene may have a major effect on the risk for LOAD in Caucasians.     

Replication of EPHA1 and CD33 associations with late-onset Alzheimer's disease: a multi-centre case-control study

Background

A recently published genome-wide association study (GWAS) of late-onset Alzheimer's disease (LOAD) revealed genome-wide significant association of variants in or near MS4A4A, CD2AP, EPHA1 and CD33. Meta-analyses of this and a previously published GWAS revealed significant association at ABCA7 and MS4A, independent evidence for association of CD2AP, CD33 and EPHA1 and an opposing yet significant association of a variant near ARID5B. In this study, we genotyped five variants (in or near CD2AP, EPHA1, ARID5B, and CD33) in a large (2,634 LOAD, 4,201 controls), independent dataset comprising six case-control series from the USA and Europe. We performed meta-analyses of the association of these variants with LOAD and tested for association using logistic regression adjusted by age-at-diagnosis, gender, and APOE ε4 dosage.

Results

We found no significant evidence of series heterogeneity. Associations with LOAD were successfully replicated for EPHA1 (rs11767557; OR = 0.87, p = 5 × 10^-4) and CD33 (rs3865444; OR = 0.92, p = 0.049), with odds ratios comparable to those previously reported. Although the two ARID5B variants (rs2588969 and rs494288) showed significant association with LOAD in meta-analysis of our dataset (p = 0.046 and 0.008, respectively), the associations did not survive adjustment for covariates (p = 0.30 and 0.11, respectively). We had insufficient evidence in our data to support the association of the CD2AP variant (rs9349407, p = 0.56).

Conclusions

Our data overwhelmingly support the association of EPHA1 and CD33 variants with LOAD risk: addition of our data to the results previously reported (total n > 42,000) increased the strength of evidence for these variants, providing impressive p-values of 2.1 × 10^-15 (EPHA1) and 1.8 × 10^-13 (CD33).