Parkinson's disease and low frequency alleles found together throughout LRRK2.

Mutations within LRRK2, most notably p.G2019S, cause Parkinson's disease (PD) in rare monogenic families, and sporadic occurrences in diverse populations. We investigated variation throughout LRRK2 (84 SNPs; genotype or diplotype found for 49 LD blocks) for 275 cases (European ancestry, onset at age 60 or older) and 275 neurologically healthy control subjects (NINDS Neurogenetics Repository). Three grade-of-membership groups, i.e. genetic risk sets, were identified that exactly matched many subjects (cases: 46, 4, 137; controls: 0, 178, 0), and distinguished 94% of the subjects (i.e. >50% likeness to one set). Set I, affected, carried certain low frequency alleles located in multiple functional domains. Set II was unaffected. Set III, also affected, resembled set II except for slightly elevated frequencies of minor alleles not defining set I. We conclude that certain low frequency alleles distributed throughout LRRK2 are a genetic background to a third of cases, defining a distinct subset.

Gonadotropins and cognition in older women.

Recent research studies associate elevated gonadotropin levels with dementia. Specifically, an age associated increase in levels of luteinizing hormone has been linked to an increased risk of Alzheimer's disease. The objective of this study was to investigate the association between gonadotropin levels and cognition in older, healthy postmenopausal women. Cognitive functioning was compared with plasma levels of estradiol, luteinizing hormone, follicle stimulating hormone, Abeta40 and APOE genetic status in 649 community-dwelling, non-demented older women residing in Western Australia. High endogenous luteinizing hormone levels were associated with a lower cognitive score, especially in older women and in those women that were depressed. Unexpectedly, disproportionately well preserved cognitive functioning was found for the oldest women who had high endogenous levels of follicle stimulating hormone. The findings indicate that gonadotropins can impact upon cognitive functioning in older postmenopausal women, and that luteinizing hormone and follicle stimulating hormone may exert contrasting effects. Taken together, the findings have important implications for the development of possible preventive strategies for dementia.

Genetic susceptibility sets for Alzheimer's disease identified from diverse candidate loci.

Alzheimer's disease (AD) has been demonstrated to be associated with gene variants of APOE, but numerous additional candidate loci exist with varying levels of statistical support. We defined susceptibility sets for AD based on information on 18 genetic loci on chromosome 10q (32 loci) and elsewhere (34 loci) and quantitative traits, including CSF tau and Abeta(42) levels. The 938 AD patients and 397 control subjects were enrolled in Scotland and Sweden. A fuzzy latent classification approach -- grade-of-membership analysis (GoM) -- was taken to identify risk sets. Individuals were automatically related to each set via GoM scores. Set I: unaffected + (downward arrow) CSF tau + (upward arrow) CSF Abeta(42) + multiple protective alleles. High intrinsic risk sets II-VI differed in onset age and relevant alleles: close resemblance (i.e., >75% aggregate membership) multiplied risk of AD >100-fold at ages 65 to 84. It is likely that AD has multiple determinants, including APOE polymorphism and gene variants located on chromosome 10q and elsewhere.

Analysis of APBB2 gene polymorphisms in sporadic Alzheimer's disease.

The accumulation of beta-amyloid (Abeta) in the brain plays a central role in the pathogenesis of Alzheimer's disease (AD). The processing of Abeta precursor protein to Abeta is modulated by binding proteins including APBB2 [amyloid beta precursor protein-binding family B member 2, FE65-like, FE65L1]. We investigated two intronic SNPs within the APBB2 gene: rs13133980 and hCV1558625 (rs17443013), among Polish AD patients and healthy controls (n=213, 171). The frequencies of rs13133980 alleles and genotypes did not differ between cases and controls, irrespective of age of onset or APOE epsilon4 carrier status. The hCV1558625 G allele was over-represented in patients with onset under age 70 compared to controls in the same age range (57% vs. 43%, p=0.03). The association between the hCV1558625 G allele and susceptibility for AD at relatively young ages needs to be confirmed in other samples.

Susceptibility groups for Alzheimer's disease (OPTIMA cohort): integration of gene variants and biochemical factors.

Information on gene variants and blood levels (APOE, BCHE-K, TF-C2, HFE-D, HFE-Y, ACE I/D, AR1; homocysteine, folate and vitamin B(12)) is available for participants in the Oxford Project to Investigate Memory and Ageing (OPTIMA) cohort (n=575). This information identified four risk sets for Alzheimer's disease (AD) using grade of membership analysis (GoM). Graded membership scores that relate individuals to each set are automatically generated. Sets I and III had low intrinsic risk. Set II had high intrinsic risk associated with multiple gene variants, e.g., APOE44/34. Set IV also had high intrinsic risk demonstrating low folate and B(12) levels. Membership in the high intrinsic risk sets was summed, coded as either close versus not close (>or=0.80 versus <0.80) and input into logistic models to predict relative risk: close resemblance multiplied risk 80-fold for possible AD before age 65 and 55-fold for probable or definite AD at ages 65-74. These findings implicate both biochemical and genetic factors in the risk for AD and further support dietary supplementation with folate and vitamin B(12) as a potential means to delay the onset of AD and/or its rate of progression.

Acute myocardial infarction and proinflammatory gene variants.

We identified four genetic risk sets for acute myocardial infarction (AMI) from information on functional gene variants that favor inflammation or modulate cholesterol metabolism: IL6 -174 G/C, TNF -308 G/A, IL10 -1082 G/A, SERPINA3 -51 G/T, IFNG +874 T/A, HMGCR -911 C/A, and APOE epsilon2/3/4; 316 patients and 461 healthy subjects, all Italian. Putative risk alleles are shown underlined. The sets were identified using grade-of-membership analysis. Membership scores in the sets are automatically generated for individuals. The 'low intrinsic risk' set had alleles that downregulate inflammation and cholesterol synthesis (IL6, TNF, ILl0, HMGCR). 'AMI across a broad age range' carried multiple proinflammatory alleles (IL6, TNF, IL10, SERPINA3): All 72 persons like this set were affected yet had relatively low plasma cholesterol levels. 'A subset of AMI in middle age' had numerous proinflammatory alleles (IL6, TNF, SERPINA3, IFNG, HMGCR). 'AMI after age 80' had a reduced risk set (IL6, IL10, IFNG). A total of 95% of cases had >/=50% membership in the high intrinsic risk sets. We conclude that proinflammatory gene variants taken together strongly determine an individual's risk for myocardial infarction. This information may better define the pathogenesis of myocardial infarction and identify individuals who might benefit from early interventions.

Multilocus genotypes spanning estrogen metabolism associated with breast cancer and fibroadenoma.

We investigated inherited polymorphic variation in genes spanning estrogen metabolism (10 SNPs [single nucleotide polymorphism]) to distinguish multilocus genotypes associated with breast cancer (n = 393), benign breast lesions (n = 154), and low risk (n = 1936). Three latent classification GoM extreme type groups represented the data: (a) fibroadenoma, and infrequent SRD5A2 and VDR alleles; (b) postmenopausal breast cancer, and infrequent CYP1A1-1 and CYP1A1-2 alleles (both over-represented infrequent alleles for CYP17, CYP19-3, and COMT); and (c) women at intrinsically low risk. Carriage of the respective multilocus genotypes increased risk 25-fold. We conclude that GoM latent classification may be useful to identify genetic risk sets and estimate risk for individuals.

Membership in genetic groups predicts Alzheimer disease.

The multiple polymorphisms contributing to Alzheimer disease (AD) have been difficult to identify. Three essentially sufficient risk sets were found using a fuzzy latent classification statistical model; that is, grade-of-membership analysis, and genotypes for APOE, APOCI, LDLr, cystatin C, and cathepsin D (180 cases, 120 controls). These were: (a) CST3:GA and CTSD:CT; (b) APOE44 and LDLr8:GG and LDLr13:TT; and (c) APOE34 and LDLr13:TC. Consonance with one of the groups and high aggregate membership carried >800-fold elevated risk for AD. The absence of these combinations defined low risk. APOE3/- with heterozygous promoter and receptor genotypes predicted long life without dementia.

Apolipoprotein gene E4 allele promoter polymorphisms as risk factors for Alzheimer's disease.

Alzheimer's disease is a complex neurodegenerative disorder, characterized by progressive cognitive decline and distinct neuropathology. The apolipoprotein gene E4 allele (APOE 4) is a major risk factor for the disease. Promoter polymorphisms at -491 and -427 may also contribute to the risk. We examined the two polymorphisms in 178 Alzheimer's patients and 141 controls. The -491AA genotype was overrepresented among the patients (68 versus 54%, P=0.01). However, in patients who were APOE4 carriers, the -491AA genotype more than doubled the risk [odds ratio (OR)=2.5; 95% confidence interval (CI)=1.2-5.4], especially in combination with -427TT [odds ratio (OR)=3.3; 95% confidence interval (CI)=1.5-7.7]. Moreover, the -491A/-427T/APOE4/APOC1A haplotype was threefold higher for patients. These results contribute to the evidence that regulation of APOE4 expression modulates risk for Alzheimer's disease.

In vitro apolipoprotein E protects human red blood cells against lysis induced by amyloid-beta (AP) fragment 25-35.

Mattson et al. (9) demonstrated lysis of human red blood cells (RBC) exposed to amyloid peptide Abeta(25-35), a new experimental model for amyloid-beta toxicity. Lysis resulted from poreformation in the RBC membranes and was completely prevented by concurrent exposure to Congo red We demonstrate that human serum, purified ApoE from human plasma, and recombinant isoforms of ApoE neutralize the Abeta(25-35) cytotoxicity: the E2 and E4 isoforms were marginally more effective than E3. Second, we demonstrate that Abeta(25-35) forms fibrils in the reaction mixtures using electron-microscopy. Together these results suggest that the RBC model might be useful in preliminary identification of natural and synthetic substances able to protect against amyloid-beta cytotoxic effects due to fibrillar Abeta(25-35). Such compounds would be candidate molecules for testing in neuronal systems.

The biphasic relationship between regional brain senile plaque and neurofibrillary tangle distributions: modification by age, sex, and APOE polymorphism.

Epidemiologic studies indicate that elderly women are at higher risk for Alzheimer disease compared to men. In order to pathologically verify this result, the extent of AD brain lesions (NFT and SP) was compared for men and women at each age, that is, at each decade from 25 years to 95 years, in a large sample of > 5000 routine autopsy cases. Women had more affected brain regions beginning in late middle age. They also had more extensive SP depositions throughout the brain compared to men at each early NFT stage I, II, and III. At later NFT stages IV, V, and VI both men and women had extensive SP deposits. The gender gap in SPs at early NFT stages was large and specific to women who carried the APOE4 allele (P <.001) and in addition to the acceleration in NFT stage also found for APOE4+ women.

Albumin protects human red blood cells against Abeta25-35-induced lysis more effectively than ApoE.

Inhibition of the lysis of human red blood cells (RBCs) exposed to amyloid peptide Abeta25-35 is an model for screening natural and synthetic substances potentially protective against amyloid damage. In this system, human serum and a component, namely apolipoprotein E (apoE), completely prevent RBC lysis. This report demonstrates that albumin, another serum component, is 8-fold more protective: a concentration of 12.5 microg/ml protects RBCs against 20 microM-Abeta25-35, and prevents the formation of fibrillar Abeta25-35 aggregates stainable by Congo Red. The biological relevance of these findings is suggested by the following: (1) a large fraction ( approximately 90%) of circulating Abeta1-42 is bound to albumin; (2) albumin immunoreactivity is present in brain amyloid plaques; and (3) incubation of Abeta with albumin rapidly decreases detectable levels of free Abeta suggesting epitope masking. The results add new and important functional consequences to the amyloid-albumin relationship and imply that experimental systems investigating Abeta cytotoxicity should consider the protective interaction of albumin.

Genetic variation in apolipoprotein D and Alzheimer's disease.

Apolipoprotein D (apoD) is a lipoprotein-associated glycoprotein, structurally unrelated to apoE, that transports small hydrophobic ligands including cholesterol and sterols. Levels are increased in the hippocampus and CSF of Alzheimer's disease (AD) patients. We tested whether variation in the APOD gene affects AD risk. Four single nucleotide polymorphisms (SNPs) were investigated (in map order): exon 2, 15T-->C encodes an amino acid substitution Phe-->Ser at codon 15; intron 2, -352G-->A; intron 3, +45C-->T; intron 4, +718C-->T, determined by SNaPshot assay. SNP frequencies for 394 eastern Finnish AD patients were compared with those found for 470 control subjects, dividing subjects also into early-onset AD (EOAD; < or = 65 years) and late-onset AD (LOAD; >65 years) groups. The -352G allele was associated with a significant 3-fold increase in the risk of EOAD (OR: 2.7; 95% CI: 1.1-6.5). The -352G containing haplotypes were more common for EOAD cases (TGCC: 0.48 vs 0.41; TGCT: 0.08 vs 0.01 (p = 0.002). In the Grade-of-membership analysis, APOD genotype frequencies at each SNP site and disease status were used to construct two latent groups: the affected group carried -352 as GG or GA and +45 CC, was often women and enriched in APOE epsilon4. Each method suggested that the -352G allele frequency is higher for EOAD in the eastern Finnish population.

Transferrin neutralization of amyloid beta 25-35 cytotoxicity.

BACKGROUND: Fibrillar aggregates of amyloid beta 25-35 (Abeta(25-35)) form rapidly in vitro able to lyse human red blood cells (RBCs). Human sera, albumin, and apolipoprotein E (ApoE) each limit fibrillation and cytotoxicity. Potentially, these substances protect neurons from Abeta(1-40/42) aggregates. Transferrin (TF) is investigated in this study. METHODS: The Mattson red blood cells model was employed to determine whether co-incubation of transferrin and Abeta(25-35) prevented lysis. The formation of fibrillar Abeta(25-35) in the presence of transferrin was investigated using Congo red staining and spectrophotometric studies. RESULTS: We found that incubation of 20 muM Abeta(25-35) with physiologic levels of transferrin prevented red blood cells lysis and the formation of macro-aggregates. CONCLUSIONS: These in vitro results suggest that transferrin may limit fibrillar beta amyloid formation in vivo and cytotoxicity.

Sharing pathogenetic mechanisms between acute myocardial infarction and Alzheimer's disease as shown by partially overlapping of gene variant profiles.

Gene variants that promote inflammation and cholesterol metabolism have been associated with acute myocardial infarction (AMI) and Alzheimer's disease (AD). We investigated a panel of relevant polymorphisms to distinguish genetic backgrounds for AMI and AD: IL10 -1082G/A, IL6 -174G/C, TNF -308G/A, IFNG +874T/A, SERPINA3 -51G/T, HMGCR -911C/A, APOE ε2/3/4 (280 AMI cases, 257 AD cases, and 1307 population controls, all Italian (presumed risk alleles are shown in bold). Six genetic risk sets I to VI were identified by fuzzy latent classification: I had low risk; II and III had low risk before age 65 (II, III); low risk sets lacked pro-inflammatory alleles for HMGCR-TNF-APOE. Pro-inflammatory alleles for SERPINA3-IL10-IFNG were found for high risk sets IV to VI. Set IV 'AMI < age 40, AD < age 65' included risk alleles for HMGCR. Set V 'AMI over a broad range of age' included risk alleles for TNF+IL6. Set VI 'AMI at ages 40 to 55, AD ages 65+' included APOE ε4. Close resemblance to the high risk sets, as indicated by membership scores close to one, defined high relative risks. We conclude that AMI and AD share genetic backgrounds involving cholesterol metabolism and the upregulation of inflammation and that gene-gene interactions in relevant sets of genes may be useful in defining inherited risk for common disorders.

Earlier onset of Alzheimer's disease: risk polymorphisms within PRNP, PRND, CYP46, and APOE genes.

We studied eight polymorphisms within APOE, PRNP, PRND, and CYP46 genes in 213 Polish late-onset patients with Alzheimer's disease (AD) and 171 non-demented elderly controls. A latent classification approach, grade-of-membership analysis, was taken to identify three extreme pure type risk sets defined by the probabilities of being affected with AD and for genotypes found at the examined genes. Sets I and II represented high intrinsic risk, having a higher density of various genotypes compared to set III, at low intrinsic risk. A gradient of onset age depending on membership in the risk sets was also observed. Logistic regression analysis showed that the highest risk for AD was found for individuals who co-inherited APOE epsilon4 allele, PRNP codon 129 homozygosity, PRND codon 174 Thr allele, and CYP46 rs754203 g allele. AD can be influenced by genetic profiles leading to appearance of the disease, composed of genes which separately evoke a little or unnoticeable effect. Moreover, there may be multiple sufficient risk sets for AD. Looking at multiple genes together rather than analyzing them individually, may improve identification of risk alleles.

Genetic risk profiles for Alzheimer's disease: integration of APOE genotype and variants that up-regulate inflammation.

BACKGROUND: A number of studies associate Alzheimer's disease with APOE polymorphism and alleles which favor the increased expression of immunological mediators such as cytokines or acute phase proteins. We integrated this information to better define risk and determine the relative importance of APOE and immunological mediators. METHODS: We investigated functional gene variants for APOE, IL-10 (3 loci), ACT (2 loci), HMGCR, IL-1alpha, IL-1beta, TNF-alpha, IFN-gamma, and IL-6 found for 260 AD patients and 190 controls enrolled in Northern Italy. A fuzzy latent classification approach, namely grade-of-membership analysis (GoM), was taken to identify extreme pure type risk sets, or profiles. This approach automatically relates individuals to each profile via graded membership scores. FINDINGS: Four extreme pure type risk sets were identified. Set I defined low intrinsic risk and had a low probability of carrying pro-inflammatory alleles or APOE epsilon4. Three sufficient risk sets were identified: early onset AD (set II) was characterized by a high density of pro-inflammatory alleles, a rapid cognitive decline and independent of APOE epsilon4. Late onset AD had a lower density (ages 65-74, set III), or a subset homozygous (ages 75+, set IV), for these alleles and a high probability of one or two APOE epsilon4 alleles. A total of 97% of the subjects who were cases strongly resembled, i.e. had at least 50% membership in, the sufficient risk sets, as did 25% of middle aged control subjects. IL-10, HMGCR, ACT, and IL-1beta gene variants were each more informative in identifying the risk sets than was APOE. INTERPRETATION: AD likely has many determinants including APOE polymorphism and gene variants that modulate innate immunity. Identification of these factors, risk prediction for individuals, and successful prevention and treatment trials require integration of relevant information.