Diurnal cortisol, neuroinflammation, and neuroimaging visual rating scales in memory clinic patients.

BACKGROUND: Neuroinflammation is a hallmark of the Alzheimer's disease (AD) pathogenic process. Cortisol dysregulation may increase AD risk and is related to brain atrophy. This cross-sectional study aims to examine interactions of cortisol patterns and neuroinflammation markers in their association with neuroimaging correlates. METHOD: 134 participants were recruited from the Karolinska University Hospital memory clinic (Stockholm, Sweden). Four visual rating scales were applied to magnetic resonance imaging or computed tomography scans: medial temporal lobe atrophy (MTA), global cortical atrophy (GCA), white matter lesions (WML), and posterior atrophy. Participants provided saliva samples for assessment of diurnal cortisol patterns, and underwent lumbar punctures for cerebrospinal fluid (CSF) sampling. Three cortisol measures were used: the cortisol awakening response, total daily output, and the ratio of awakening to bedtime levels. Nineteen CSF neuroinflammation markers were categorized into five composite scores: proinflammatory cytokines, other cytokines, angiogenesis markers, vascular injury markers, and glial activation markers. Ordinal logistic regressions were conducted to assess associations between cortisol patterns, neuroinflammation scores, and visual rating scales, and interactions between cortisol patterns and neuroinflammation scores in relation to visual rating scales. RESULT: Higher levels of angiogenesis markers were associated with more severe WML. Some evidence was found for interactions between dysregulated diurnal cortisol patterns and greater neuroinflammation-related biomarkers in relation to more severe GCA and WML. No associations were found between cortisol patterns and visual rating scales. CONCLUSION: This study suggests an interplay between diurnal cortisol patterns and neuroinflammation in relation to brain structure. While this cross-sectional study does not provide information on causality or temporality, these findings suggest that neuroinflammation may be involved in the relationship between HPA-axis functioning and AD.

CYP46A1-mediated cholesterol turnover induces sex-specific changes in cognition and counteracts memory loss in ovariectomized mice.

The brain-specific enzyme CYP46A1 controls cholesterol turnover by converting cholesterol into 24S-hydroxycholesterol (24OH). Dysregulation of brain cholesterol turnover and reduced CYP46A1 levels are observed in Alzheimer's disease (AD). In this study, we report that CYP46A1 overexpression in aged female mice leads to enhanced estrogen signaling in the hippocampus and improved cognitive functions. In contrast, age-matched CYP46A1 overexpressing males show anxiety-like behavior, worsened memory, and elevated levels of 5α-dihydrotestosterone in the hippocampus. We report that, in neurons, 24OH contributes to these divergent effects by activating sex hormone signaling, including estrogen receptors. CYP46A1 overexpression in female mice protects from memory impairments induced by ovariectomy while having no effects in gonadectomized males. Last, we measured cerebrospinal fluid levels of 24OH in a clinical cohort of patients with AD and found that 24OH negatively correlates with neurodegeneration markers only in women. We suggest that CYP46A1 activation is a valuable pharmacological target for enhancing estrogen signaling in women at risk of developing neurodegenerative diseases.

Alzheimer's disease biomarker profiling in a memory clinic cohort without common comorbidities.

Alzheimer's disease is a multifactorial disorder with large heterogeneity. Comorbidities such as hypertension, hypercholesterolaemia and diabetes are known contributors to disease progression. However, less is known about their mechanistic contribution to Alzheimer's pathology and neurodegeneration. The aim of this study was to investigate the relationship of several biomarkers related to risk mechanisms in Alzheimer's disease with the well-established Alzheimer's disease markers in a memory clinic population without common comorbidities. We investigated 13 molecular markers representing key mechanisms underlying Alzheimer's disease pathogenesis in CSF from memory clinic patients without diagnosed hypertension, hypercholesterolaemia or diabetes nor other neurodegenerative disorders. An analysis of covariance was used to compare biomarker levels between clinical groups. Associations were analysed by linear regression. Two-step cluster analysis was used to determine patient clusters. Two key markers were analysed by immunofluorescence staining in the hippocampus of non-demented control and Alzheimer's disease individuals. CSF samples from a total of 90 participants were included in this study: 30 from patients with subjective cognitive decline (age 62.4 ± 4.38, female 60%), 30 with mild cognitive impairment (age 65.6 ± 7.48, female 50%) and 30 with Alzheimer's disease (age 68.2 ± 7.86, female 50%). Angiotensinogen, thioredoxin-1 and interleukin-15 had the most prominent associations with Alzheimer's disease pathology, synaptic and axonal damage markers. Synaptosomal-associated protein 25 kDa and neurofilament light chain were increased in mild cognitive impairment and Alzheimer's disease patients. Grouping biomarkers by biological function showed that inflammatory and survival components were associated with Alzheimer's disease pathology, synaptic dysfunction and axonal damage. Moreover, a vascular/metabolic component was associated with synaptic dysfunction. In the data-driven analysis, two patient clusters were identified: Cluster 1 had increased CSF markers of oxidative stress, vascular pathology and neuroinflammation and was characterized by elevated synaptic and axonal damage, compared with Cluster 2. Clinical groups were evenly distributed between the clusters. An analysis of post-mortem hippocampal tissue showed that compared with non-demented controls, angiotensinogen staining was higher in Alzheimer's disease and co-localized with phosphorylated-tau. The identification of biomarker-driven endophenotypes in cognitive disorder patients further highlights the biological heterogeneity of Alzheimer's disease and the importance of tailored prevention and treatment strategies.

Serum Thioredoxin-80 is associated with age, ApoE4, and neuropathological biomarkers in Alzheimer's disease: a potential early sign of AD.

BACKGROUND: Thioredoxin-80 (Trx80) is a cleavage product from the redox-active protein Thioredoxin-1 and has been previously described as a pro-inflammatory cytokine secreted by immune cells. Previous studies in our group reported that Trx80 levels are depleted in Alzheimer's disease (AD) brains. However, no studies so far have investigated peripheral Trx80 levels in the context of AD pathology and whether could be associated with the main known AD risk factors and biomarkers. METHODS: Trx80 was measured in serum samples from participants from two different cohorts: the observational memory clinic biobank (GEDOC) (N = 99) with AD CSF biomarker data was available and the population-based lifestyle multidomain intervention trial Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER) (N = 47), with neuroimaging data and blood markers of inflammation available. The GEDOC cohort consists of participants diagnosed with subjective cognitive impairment (SCI), mild cognitive impairment (MCI), and AD, whereas the FINGER participants are older adults at-risk of dementia, but without substantial cognitive impairment. One-way ANOVA and multiple comparison tests were used to assess the levels of Trx80 between groups. Linear regression models were used to explore associations of Trx80 with cognition, AD CSF biomarkers (Aß42, t-tau, p-tau and p-tau/t-tau ratio), inflammatory cytokines, and neuroimaging markers. RESULTS: In the GEDOC cohort, Trx80 was associated to p-tau/t-tau ratio in the MCI group. In the FINGER cohort, serum Trx80 levels correlated with lower hippocampal volume and higher pro-inflammatory cytokine levels. In both GEDOC and FINGER cohorts, ApoE4 carriers had significantly higher serum Trx80 levels compared to non-ApoE4 carriers. However, Trx80 levels in the brain were further decreased in AD patients with ApoE4 genotype. CONCLUSION: We report that serum Trx80 levels are associated to AD disease stage as well as to several risk factors for AD such as age and ApoE4 genotype, which suggests that Trx80 could have potential as serum AD biomarker. Increased serum Trx80 and decreased brain Trx80 levels was particularly seen in ApoE4 carriers. Whether this could contribute to the mechanism by which ApoE4 show increased vulnerability to develop AD would need to be further investigated. TRIAL REGISTRATION: ClinicalTrials.gov NCT01041989 . Registered on 4 January 2010-retrospectively registered.

SR Protein Kinase 1 Inhibition by TAF15.

Although SRPKs were discovered nearly 30 years ago, our understanding of their mode of regulation is still limited. Regarded as constitutively active enzymes known to participate in diverse biological processes, their prominent mode of regulation mainly depends on their intracellular localization. Molecular chaperones associate with a large internal spacer sequence that separates the bipartite kinase catalytic core and modulates the kinases' partitioning between the cytoplasm and nucleus. Besides molecular chaperones that function as anchoring proteins, a few other proteins were shown to interact directly with SRPK1, the most-studied member of SRPKs, and alter its activity. In this study, we identified TAF15, which has been involved in transcription initiation, splicing, DNA repair, and RNA maturation, as a novel SRPK1-interacting protein. The C-terminal RGG domain of TAF15 was able to associate with SRPK1 and downregulate its activity. Furthermore, overexpression of this domain partially relocalized SRPK1 to the nucleus and resulted in hypophosphorylation of SR proteins, inhibition of splicing of a reporter minigene, and inhibition of Lamin B receptor phosphorylation. We further demonstrated that peptides comprising the RGG repeats of nucleolin, HNRPU, and HNRNPA2B1, were also able to inhibit SRPK1 activity, suggesting that negative regulation of SRPK1 activity might be a key biochemical property of RGG motif-containing proteins.

Serum proBDNF Is Associated With Changes in the Ketone Body ß-Hydroxybutyrate and Shows Superior Repeatability Over Mature BDNF: Secondary Outcomes From a Cross-Over Trial in Healthy Older Adults.

Background: ß-hydroxybutyrate (BHB) can upregulate brain-derived neurotrophic factor (BDNF) in mice, but little is known about the associations between BHB and BDNF in humans. The primary aim here was to investigate whether ketosis (i.e., raised BHB levels), induced by a ketogenic supplement, influences serum levels of mature BDNF (mBDNF) and its precursor proBDNF in healthy older adults. A secondary aim was to determine the intra-individual stability (repeatability) of those biomarkers, measured as intra-class correlation coefficients (ICC). Method: Three of the arms in a 6-arm randomized cross-over trial were used for the current sub-study. Fifteen healthy volunteers, 65-75 y, 53% women, were tested once a week. Test oils, mixed in coffee and cream, were ingested after a 12-h fast. Labeled by their level of ketosis, the arms provided: sunflower oil (lowK); coconut oil (midK); caprylic acid + coconut oil (highK). Repeated blood samples were collected for 4 h after ingestion. Serum BDNF levels were analyzed for changes from baseline to 1, 2 and 4 h to compare the arms. Individual associations between BHB and BDNF were analyzed cross-sectionally and for a delayed response (changes in BHB 0-2 h to changes in BDNF at 0-4 h). ICC estimates were calculated from baseline levels from the three study days. Results: proBDNF increased more in highK vs. lowK between 0 and 4 h (z-score: ß = 0.25, 95% CI 0.07-0.44; p = 0.007). Individual change in BHB 0-2 h, predicted change in proBDNF 0-4 h, (ß = 0.40, CI 0.12-0.67; p = 0.006). Change in mBDNF was lower in highK vs. lowK at 0-2 h (ß = -0.88, CI -1.37 to -0.40; p < 0.001) and cumulatively 0-4 h (ß = -1.01, CI -1.75 to -0.27; p = 0.01), but this could not be predicted by BHB levels. ICC was 0.96 (95% CI 0.92-0.99) for proBDNF, and 0.72 (CI 0.47-0.89) for mBDNF. Conclusions: The findings support a link between changes in peripheral BHB and proBDNF in healthy older adults. For mBDNF, changes differed between arms but independent to BHB levels. Replication is warranted due to the small sample. Excellent repeatability encourages future investigations on proBDNF as a predictor of brain health. Clinical Trial Registration:ClinicalTrials.gov, NCT03904433.

Kleine-Levin syndrome is associated with birth difficulties and genetic variants in the TRANK1 gene loci.

Kleine-Levin syndrome (KLS) is a rare disorder characterized by severe episodic hypersomnia, with cognitive impairment accompanied by apathy or disinhibition. Pathophysiology is unknown, although imaging studies indicate decreased activity in hypothalamic/thalamic areas during episodes. Familial occurrence is increased, and risk is associated with reports of a difficult birth. We conducted a worldwide case-control genome-wide association study in 673 KLS cases collected over 14 y, and ethnically matched 15,341 control individuals. We found a strong genome-wide significant association (rs71947865, Odds Ratio [OR] = 1.48, P = 8.6 × 10-9) within the 3'region of TRANK1 gene locus, previously associated with bipolar disorder and schizophrenia. Strikingly, KLS cases with rs71947865 variant had significantly increased reports of a difficult birth. As perinatal outcomes have dramatically improved over the last 40 y, we further stratified our sample by birth years and found that recent cases had a significantly reduced rs71947865 association. While the rs71947865 association did not replicate in the entire follow-up sample of 171 KLS cases, rs71947865 was significantly associated with KLS in the subset follow-up sample of 59 KLS cases who reported birth difficulties (OR = 1.54, P = 0.01). Genetic liability of KLS as explained by polygenic risk scores was increased (pseudo R2 = 0.15; P < 2.0 × 10-22 at P = 0.5 threshold) in the follow-up sample. Pathway analysis of genetic associations identified enrichment of circadian regulation pathway genes in KLS cases. Our results suggest links between KLS, circadian regulation, and bipolar disorder, and indicate that the TRANK1 polymorphisms in conjunction with reported birth difficulties may predispose to KLS.

Ketosis After Intake of Coconut Oil and Caprylic Acid-With and Without Glucose: A Cross-Over Study in Healthy Older Adults.

Introduction: Medium-chain-triglycerides (MCT), formed by fatty acids with a length of 6-12 carbon atoms (C6-C12), constitute about two thirds of coconut oil (Coc). MCT have specific metabolic properties which has led them to be described as ketogenic even in the absence of carbohydrate restriction. This effect has mainly been demonstrated for caprylic acid (C8), which constitutes about 6-8% of coconut oil. Our aim was to quantify ketosis and blood glucose after intake of Coc and C8, with and without glucose intake. Sunflower oil (Suf) was used as control, expected to not break fasting ketosis, nor induce supply-driven ketosis. Method: In a 6-arm cross-over design, 15 healthy volunteers-age 65-73, 53% women-were tested once a week. After a 12-h fast, ketones were measured during 4 h after intake of coffee with cream, in combination with each of the intervention arms in a randomized order: 1. Suf (30 g); 2. C8 (20 g) + Suf (10 g); 3. C8 (20 g) + Suf (10 g) + Glucose (50 g); 4. Coc (30 g); 5. Coc (30 g) + Glucose (50 g); 6. C8 (20 g) + Coc (30 g). The primary outcome was absolute blood levels of the ketone ß-hydroxybutyrate, area under the curve (AUC). ANOVA for repeated measures was performed to compare arms. Results: ß-hydroxybutyrate, AUC/time (mean ± SD), for arms were 1: 0.18 ± 0.11; 2: 0.45 ± 0.19; 3: 0.28 ± 0.12; 4: 0.22 ± 0.12; 5: 0.08 ± 0.04; 6: 0.45 ± 0.20 (mmol/L). Differences were significant (all p ≤ 0.02), except for arm 2 vs. 6, and 4 vs. 1 & 3. Blood glucose was stable in arm 1, 2, 4, & 6, at levels slightly below baseline (p ≤ 0.05) at all timepoints hours 1-4 after intake. Conclusions: C8 had a higher ketogenic effect than the other components. Coc was not significantly different from Suf, or C8 with glucose. In addition, we report that a 16-h non-carbohydrate window contributed to a mild ketosis, while blood glucose remained stable. Our results suggest that time-restricted feeding regarding carbohydrates may optimize ketosis from intake of MCT. Clinical Trial Registration: The study was registered as a clinical trial on ClinicalTrials.gov, NCT03904433.

Aniridia with PAX6 mutations and narcolepsy.

PAX6 gene mutations cause a variety of eye and central nervous system (CNS) abnormalities. Aniridia is often accompanied by CNS abnormalities such as pineal gland atrophy or hypoplasia, leading to disturbed circadian rhythm and sleep disorders. Less is known on the coincidence of narcolepsy in this patient group. We aimed to find out whether the circadian rhythm or sleep-wake structure was affected in patients with aniridia. Four members of a family segregating with congenital aniridia in two generations were included in the study. The patients were subjected to genetic testing for a PAX6 mutation, multiple sleep latency test, whole-brain magnetic resonance imaging (MRI), hypocretin-1 in cerebrospinal fluid, and Human Leukocyte Antigen DQ beta1*06:02. All four members were heterozygous for the pathogenic c.959-1G>A mutation in the PAX6 gene. Sleep disturbance was observed in all family members. The index patient was diagnosed with narcolepsy. MRI showed a hypoplastic pineal gland in all members. We describe the first case of a patient with PAX6 haploinsufficiency, aniridia and pineal gland hypoplasia diagnosed with narcolepsy type-1, suggesting a complex sleep disorder pathogenesis.

Pandemrix-induced narcolepsy is associated with genes related to immunity and neuronal survival.

BACKGROUND: The incidence of narcolepsy rose sharply after the swine influenza A (H1N1) vaccination campaign with Pandemrix. Narcolepsy is an immune-related disorder with excessive daytime sleepiness. The most frequent form is strongly associated with HLA-DQB1*06:02, but only a minority of carriers develop narcolepsy. We aimed to identify genetic markers that predispose to Pandemrix-induced narcolepsy. METHODS: We tested for genome-wide and candidate gene associations in 42 narcolepsy cases and 4981 controls. Genotyping was performed on Illumina arrays, HLA alleles were imputed using SNP2HLA, and single nucleotide polymorphisms were imputed using the haplotype reference consortium panel. The genome-wide significance threshold was p < 5 × 10-8, and the nominal threshold was p < 0.05. Results were replicated in 32 cases and 7125 controls. Chromatin data was used for functional annotation. FINDINGS: Carrying HLA-DQB1*06:02 was significantly associated with narcolepsy, odds ratio (OR) 39.4 [95% confidence interval (CI) 11.3, 137], p = 7.9 × 10-9. After adjustment for HLA, GDNF-AS1 (rs62360233) was significantly associated, OR = 8.7 [95% CI 4.2, 17.5], p = 2.6 × 10-9, and this was replicated, OR = 3.4 [95% CI 1.2-9.6], p = 0.022. Functional analysis revealed variants in high LD with rs62360233 that might explain the detected association. The candidate immune-gene locus TRAJ (rs1154155) was nominally associated in both the discovery and replication cohorts, meta-analysis OR = 2.0 [95% CI 1.4, 2.8], p = 0.0002. INTERPRETATION: We found a novel association between Pandemrix-induced narcolepsy and the non-coding RNA gene GDNF-AS1, which has been shown to regulate expression of the essential neurotrophic factor GDNF. Changes in regulation of GDNF have been associated with neurodegenerative diseases. This finding may increase the understanding of disease mechanisms underlying narcolepsy. Associations between Pandemrix-induced narcolepsy and immune-related genes were replicated.

Prevalence of Apolipoprotein E Polymorphisms in Alzheimer's Disease, Mild Cognitive Impairment, and Healthy Elderly: A Northern Greece Study.

BACKGROUND: Apolipoprotein E ε4 allele (APOEε4) is a major genetic risk factor for Alzheimer's disease (AD). APOEε4 carriers have a higher risk of cognitive impairment and AD in a gene dose-dependent manner. The above notion is investigated in the Greek population. METHODS: A sample of 1,703 subjects (967 AD patients, 576 mild cognitive impairment [MCI] and 160 Healthy Elderly), was genotyped for APOE from 2008 to 2017. DNA was extracted from peripheral blood using the QIAamp Blood DNA purification kit (Qiagen Inc., USA). Descriptive statistics, one-way analysis of variance with Bonferroni post hoc tests, Pearson chi-square test, and binary logistic regression models were used for the statistical analysis. RESULTS: The APOE genotype and allele frequencies in AD group were significantly different from those in the Control and MCI groups. The frequencies of ε4/4 homozygotes were 1.9, 1.6, and 5.7%, while the ε4/- carriers' distribution was 22.5, 24.1, and 37.4% in the Control, MCI, and AD groups respectively. The estimated odds of ε4/4 for AD was 5.731-fold higher compared to the estimated odds of ε3/3. The interaction between gender and APOE did not have a significant effect on the odds for MCI (p = 0.942) and AD (p = 0.984). CONCLUSION: In Greece, APOE ε4 presence is related to an increased risk for AD in a dose-related manner. Contrary to long-standing views, men and women with the APOE ε4 genotype have nearly the same odds of developing MCI and AD.

Rhamnolipids, Microbial Virulence Factors, in Alzheimer's Disease.

Alzheimer's disease (AD) has been attributed to chronic bacterial infections. The recognition of human microbiota as a substantial contributor to health and disease is relatively recent and growing. During evolution, mammals live in a symbiotic state with myriads of microorganisms that survive at a diversity of tissue micro-surroundings. Microbes produce a plethora of secretory products [amyloids, lipopolysaccharides, virulence factors rhamnolipids (RLs), toxins, and a great number of neuroactive compounds]. The contribution of infectious microbial components to the pathophysiology of the human central nervous system including AD is considered potentially substantial, but the involvement of the RLs has never been reported. Here, RLs were isolated from serum and identified through various conventional methods including the colorimetric orcinol method, thin-layer chromatography, attenuated total reflection Fourier transform infrared (ATR-FTIR), and dot blot using antibodies against RLs. Dot blot demonstrated elevated RL levels in sera of AD patients compared to controls (p = 0.014). Moreover, ELISA showed similarly elevated RL levels in cerebrospinal fluid of both AD (0.188 versus 0.080) (p = 0.04) and mild cognitive impairment (0.188 versus 0.129) (p = 0.088) patients compared to healthy, and are well-correlated with the AD stages severity assessed using the Mini-Mental State Examination. These results provide conclusive evidence for the newly-reported implication of RLs in AD, adding it to the list of bacterial components, opening new avenues for AD investigation. Moreover, they strengthen and vindicate the divergence of research toward the exploration of bacterial involvement in AD generation and progression.

Genetic predisposition to increased blood cholesterol and triglyceride lipid levels and risk of Alzheimer disease: a Mendelian randomization analysis.

BACKGROUND: Although altered lipid metabolism has been extensively implicated in the pathogenesis of Alzheimer disease (AD) through cell biological, epidemiological, and genetic studies, the molecular mechanisms linking cholesterol and AD pathology are still not well understood and contradictory results have been reported. We have used a Mendelian randomization approach to dissect the causal nature of the association between circulating lipid levels and late onset AD (LOAD) and test the hypothesis that genetically raised lipid levels increase the risk of LOAD. METHODS AND FINDINGS: We included 3,914 patients with LOAD, 1,675 older individuals without LOAD, and 4,989 individuals from the general population from six genome wide studies drawn from a white population (total n=10,578). We constructed weighted genotype risk scores (GRSs) for four blood lipid phenotypes (high-density lipoprotein cholesterol [HDL-c], low-density lipoprotein cholesterol [LDL-c], triglycerides, and total cholesterol) using well-established SNPs in 157 loci for blood lipids reported by Willer and colleagues (2013). Both full GRSs using all SNPs associated with each trait at p<5×10-8 and trait specific scores using SNPs associated exclusively with each trait at p<5 × 10-8 were developed. We used logistic regression to investigate whether the GRSs were associated with LOAD in each study and results were combined together by meta-analysis. We found no association between any of the full GRSs and LOAD (meta-analysis results: odds ratio [OR]=1.005, 95% CI 0.82-1.24, p = 0.962 per 1 unit increase in HDL-c; OR=0.901, 95% CI 0.65-1.25, p=0.530 per 1 unit increase in LDL-c; OR=1.104, 95% CI 0.89-1.37, p=0.362 per 1 unit increase in triglycerides; and OR=0.954, 95% CI 0.76-1.21, p=0.688 per 1 unit increase in total cholesterol). Results for the trait specific scores were similar; however, the trait specific scores explained much smaller phenotypic variance. CONCLUSIONS: Genetic predisposition to increased blood cholesterol and triglyceride lipid levels is not associated with elevated LOAD risk. The observed epidemiological associations between abnormal lipid levels and LOAD risk could therefore be attributed to the result of biological pleiotropy or could be secondary to LOAD. Limitations of this study include the small proportion of lipid variance explained by the GRS, biases in case-control ascertainment, and the limitations implicit to Mendelian randomization studies. Future studies should focus on larger LOAD datasets with longitudinal sampled peripheral lipid measures and other markers of lipid metabolism, which have been shown to be altered in LOAD. Please see later in the article for the Editors' Summary.

Alleles that increase risk for type 2 diabetes mellitus are not associated with increased risk for Alzheimer's disease.

Although epidemiological studies suggest that type 2 diabetes mellitus (T2DM) increases the risk of late-onset Alzheimer's disease (LOAD), the biological basis of this relationship is not well understood. The aim of this study was to examine the genetic comorbidity between the 2 disorders and to investigate whether genetic liability to T2DM, estimated by a genotype risk scores based on T2DM associated loci, is associated with increased risk of LOAD. This study was performed in 2 stages. In stage 1, we combined genotypes for the top 15 T2DM-associated polymorphisms drawn from approximately 3000 individuals (1349 cases and 1351 control subjects) with extracted and/or imputed data from 6 genome-wide studies (>10,000 individuals; 4507 cases, 2183 controls, 4989 population controls) to form a genotype risk score and examined if this was associated with increased LOAD risk in a combined meta-analysis. In stage 2, we investigated the association of LOAD with an expanded T2DM score made of 45 well-established variants drawn from the 6 genome-wide studies. Results were combined in a meta-analysis. Both stage 1 and stage 2 T2DM risk scores were not associated with LOAD risk (odds ratio = 0.988; 95% confidence interval, 0.972-1.004; p = 0.144 and odds ratio = 0.993; 95% confidence interval, 0.983-1.003; p = 0.149 per allele, respectively). Contrary to expectation, genotype risk scores based on established T2DM candidates were not associated with increased risk of LOAD. The observed epidemiological associations between T2DM and LOAD could therefore be a consequence of secondary disease processes, pleiotropic mechanisms, and/or common environmental risk factors. Future work should focus on well-characterized longitudinal cohorts with extensive phenotypic and genetic data relevant to both LOAD and T2DM.

The role of ABCA1 gene sequence variants on risk of Alzheimer's disease.

The ATP-binding cassette, sub-family A, member 1 gene (ABCA1) is a candidate risk gene for late onset Alzheimer's disease (LOAD) as a consequence of its role in cholesterol transport and metabolism, which is implicated in LOAD risk. ABCA1 has been shown in mouse models to enable the clearance of amyloid-ß peptide from the brain, through its role in the lipidation of apolipoprotein (APOE). Although recent large scale genome wide association studies (GWAS) have failed to find significant associations with common genetic variants in this gene and LOAD, rare variants in ABCA1 have been shown to influence plasma high-density lipoprotein cholesterol levels. Using next generation sequencing of pooled DNA samples, we sequenced all the coding regions of ABCA1 in 311 LOAD cases and 360 control individuals drawn from the Greek population to identify low frequency non-synonymous variation. There were a significantly higher proportion of rare non-synonymous variants in control individuals compared to AD cases, suggestive of a protective effect. These findings provide new evidence of an effect of ABCA1 variants on AD risk. In addition they highlight the importance of high throughput sequencing in the identification of rare variation undetected by GWAS, but with the potential to have a strong effect on risk of LOAD.

The deletion variant of α2b-adrenergic receptor is associated with decreased risk in Alzheimer's disease and mild cognitive impairment.

A common genetic polymorphism of the α2b-adrenergic receptor (ADRA2B) resulting in a deletion of three glutamic acids located on the third intracellular loop of the protein, has been associated with memory formation enhanced by emotional events. Additionally, there are several studies documenting the involvement of this polymorphism in other types of cognition, such as episodic memory. The aim of this study was to investigate the possible relationship of this genetic variance with a common memory affecting disease, Alzheimer's disease. Our study was carried out in a total number of 311 Greek subjects, including 119 sporadic AD patients, 95 MCI cases and 97 controls. Genomic DNA was extracted from whole blood and the fragments containing the polymorphism were amplified by PCR analysis. A genotypic analysis of the APOE polymorphism was also carried out. A significant difference in the frequency of the ADRA2B genetic variation among the three groups was observed. Specifically, the deletion variant is more prevalent in controls than in AD and MCI patients. Our data demonstrate for the first time an independent contribution of the ADRA2B genetic polymorphism to memory impairment and we further suggest a possible protective role of the deletion variant against the disease development.

Alzheimer's disease and age-related macular degeneration have different genetic models for complement gene variation.

Alzheimer's disease (AD) and age-related macular degeneration (AMD) are both neurodegenerative disorders which share common pathological and biochemical features of the complement pathway. The aim of this study was to investigate whether there is an association between well replicated AMD genetic risk factors and AD. A large cohort of AD (n = 3898) patients and controls were genotyped for single nucleotide polymorphisms (SNPs) in the complement factor H (CFH), the Age-related maculopathy susceptibility protein 2 (ARMS2) the complement component 2 (C2), the complement factor B (CFB), and the complement component 3 (C3) genes. While significant but modest associations were identified between the complement factor H, the age-related maculopathy susceptibility protein 2, and the complement component 3 single nucleotide polymorphisms and AD, these were different in direction or genetic model to that observed in AMD. In addition the multilocus genetic model that predicts around a half of the sibling risk for AMD does not predict risk for AD. Our study provides further support to the hypothesis that while activation of the alternative complement pathway is central to AMD pathogenesis, it is less involved in AD.

Detection of elevated antibodies against SR protein kinase 1 in the serum of Alzheimer's disease patients.

Autoantibodies targeting specific cellular antigens are often present in sera and cerebrospinal fluids (CSFs) of patients with Alzheimer's disease (AD) and could play a role in the onset and/or progression of the disease. In this study we identified SR Protein Kinase 1 (SRPK1) as a new autoantigen elevated in AD. SRPK1, the prototype of the serine/arginine family of kinases, has been implicated in the regulation of multiple cellular processes such as pre-mRNA splicing, cell proliferation, chromatin structure, nuclear import and germ cell development. Using an ELISA assay, anti-SRPK1 antibodies, targeting mainly the first catalytic domain of the kinase, were detected in sera of patients with AD, at significantly elevated levels as compared to control subjects. The findings of this study document for the first time the existence of antibodies targeting SRPK1 in human sera and are indicative of a correlation between the levels of a-SRPK1 antibodies and the incidence of AD.

The ratio of SRPK1/SRPK1a regulates erythroid differentiation in K562 leukaemic cells.

SRPK1, the prototype of the serine/arginine family of kinases, has been implicated in the regulation of multiple cellular processes such as pre-mRNA splicing, chromatin structure, nuclear import and germ cell development. SRPK1a is a much less studied isoform of SRPK1 that contains an extended N-terminal domain and so far has only been detected in human testis. In the present study we show that SRPK1 is the predominant isoform in K562 cells, with the ratio of the two isoforms being critical in determining cell fate. Stable overexpression of SRPK1a induces erythroid differentiation of K562 cells. The induction of globin synthesis was accompanied by a marked decrease in proliferation and a significantly reduced clonogenic potential. Small interfering RNA-mediated down-regulation of SRPK1 in K562 cells results similarly in a decrease in proliferative capacity and induction of globin synthesis. A decreased SRPK1/SRPK1a ratio is also observed upon hemin/DMSO-induced differentiation of K562 cells as well as in normal human erythroid progenitor cells. Mass spectrometric analysis of SRPK1a-associated proteins identified multiple classes of RNA-binding proteins including RNA helicases, heterogeneous nuclear ribonucleoproteins, ribosomal proteins, and mRNA-associated proteins. Several of the SRPK1a-copurifying proteins have been previously identified in ribosomal and pre-ribosomal complexes, thereby suggesting that SRPK1a may play an important role in linking ribosomal assembly and/or function to erythroid differentiation in human leukaemic cells.

Association study of cholesterol-related genes in Alzheimer's disease.

Alzheimer's disease (AD) is a genetically complex disorder, and several genes related to cholesterol metabolism have been reported to contribute to AD risk. To identify further AD susceptibility genes, we have screened genes that map to chromosomal regions with high logarithm of the odds scores for AD in full genome scans and are related to cholesterol metabolism. In a European screening sample of 115 sporadic AD patients and 191 healthy control subjects, we analyzed single nucleotide polymorphisms in 28 cholesterol-related genes for association with AD. The genes HMGCS2, FDPS, RAFTLIN, ACAD8, NPC2, and ABCG1 were associated with AD at a significance level of P < or = 0.05 in this sample. Replication trials in five independent European samples detected associations of variants within HMGCS2, FDPS, NPC2, or ABCG1 with AD in some samples (P = 0.05 to P = 0.005). We did not identify a marker that was significantly associated with AD in the pooled sample (n = 2864). Stratification of this sample revealed an APOE-dependent association of HMGCS2 with AD (P = 0.004). We conclude that genetic variants investigated in this study may be associated with a moderate modification of the risk for AD in some samples.