Decreased prevalence of Alzheimer disease associated with 3-hydroxy-3-methyglutaryl coenzyme A reductase inhibitors

Inhibition of Cholesterol Biosynthesis Reduces γ-Secretase Activity and Amyloid-β Generation

Amyloid-β (Aβ) is one of major molecules contributing to the pathogenesis of Alzheimer's disease (AD). Aβ is derived from amyloid-β protein precursor (AβPP) through sequential cleavages by β- and γ-secretases. Regulation of these components is thought to be an important factor in Aβ generation during the pathogenesis of AD. AβPP, β-secretase, and γ-secretase reside in lipid rafts, where cholesterol regulates the integrity and flexibility of membrane proteins and Aβ is generated. However, the relationship between cholesterol and Aβ generation is controversial. In this study, we aimed to elucidate the direct effects of cholesterol depletion on AβPP processing using AY9944, which blocks the last step of cholesterol biosynthesis and thus minimizes the unknown side effects of upstream inhibitors, such as HMG-CoA reductase inhibitors. Treatment with AY9944 decreased γ-secretase activity and Aβ generation. These results suggested that changes in membrane composition by lowering cholesterol with AY9944 affected γ-secretase activity and Aβ generation, which is associated with AD pathogenesis.

Cholesterol, 24-Hydroxycholesterol, and 27-Hydroxycholesterol as Surrogate Biomarkers in Cerebrospinal Fluid in Mild Cognitive Impairment and Alzheimer's Disease: A Meta-Analysis

Abnormal cholesterol metabolism is an established feature of Alzheimer's disease (AD). Cerebrospinal fluid (CSF) is the fluid surrounding the central nervous system, and the protein and lipid content alterations in the CSF could be biomarkers for degenerative changes in the brain. The laboratory diagnosis of AD is limited to the analysis of three biomarkers in CSF: Aβ42, total tau, and phospho-tau. The purpose of this analysis is to systematically analyze the available data describing the biomarkers of cholesterol and its metabolites in the CSF of subjects with AD. MEDLINE, EMBASE, and the Cochrane Central database were systematically queried to collect studies that have evaluated the markers of cholesterol and its metabolites in the CSF of subjects with mild cognitive impairment (MCI) or AD and age-matched controls. Analysis of the published data shows that the levels of cholesterol are increased in MCI subjects; 24-hydroxycholesterol and 27-hydroxycholesterol are elevated in AD and MCI subjects compared to controls. There is a significant dysfunction of cholesterol metabolism in the CSF of AD subjects. This analysis indicates that in addition to the available biomarkers in the CSF, such as Aβ42, total tau, and phospho-tau, 24-hydroxycholesterol, 27-hydroxycholesterol, and cholesterol appear to be sensitive biomarkers for the evaluation of MCI and AD.

Simvastatin-Induced Decline in Cognition

Objective:

To describe a case of new-onset cognitive difficulties in an older patient after initiation of simvastatin therapy.

Case Summary:

A 64-year-old man developed cognitive difficulties within one week after starting simvastatin 40 mg/day. There was a 3 point decline from baseline in the Mini-Mental State Exam (MMSE) score 2 weeks after simvastatin was initiated, as well as declines in the Activities of Daily Living and Instrumental Activities of Daily Living scales. Simvastatin was discontinued, and the patient's cognition improved to baseline within 6 weeks. Rechallenge with simvastatin at half the original dose was attempted. His cognition deteriorated over a 2 week period. Simvastatin was stopped, and the patient's MMSE scores returned to baseline within 4 weeks.

Discussion:

This patient developed new-onset problems with short-term memory, long-term memory, and item misplacement in addition to the baseline problems with names and word-finding that had been present prior to beginning statin therapy. Decreased cognition identified with neuropsychological tests has been shown in clinical trials with simvastatin; however, as of August 23, 2006, this is the first report of cognitive and functional problems that have been documented using standardized instruments. The Naranjo probability scale revealed a highly probable adverse reaction of cognitive decline associated with simvastatin therapy.

Conclusions:

Statins are commonly used in the older population. Simvastatin appeared to be associated with worsened cognition in our patient, an older person with preexisting memory problems. Statins should be used with caution in this vulnerable population.

Tocotrienol Affects Oxidative Stress, Cholesterol Homeostasis and the Amyloidogenic Pathway in Neuroblastoma Cells: Consequences for Alzheimer's Disease

One of the characteristics of Alzheimer´s disease (AD) is an increased amyloid load and an enhanced level of reactive oxidative species (ROS). Vitamin E has known beneficial neuroprotective effects, and previously, some studies suggested that vitamin E is associated with a reduced risk of AD due to its antioxidative properties. However, epidemiological studies and nutritional approaches of vitamin E treatment are controversial. Here, we investigate the effect of α-tocotrienol, which belongs to the group of vitamin E, on AD-relevant processes in neuronal cell lines. In line with the literature, α-tocotrienol reduced the ROS level in SH-SY5Y cells. In the presence of tocotrienols, cholesterol and cholesterol esters, which have been shown to be risk factors in AD, were decreased. Besides the unambiguous positive effects of tocotrienol, amyloid-β (Aβ) levels were increased accompanied by an increase in the activity of enzymes responsible for Aβ production. Proteins and gene expression of the secretases and their components remained unchanged, whereas tocotrienol accelerates enzyme activity in cell-free assays. Besides enhanced Aβ production, tocotrienols inhibited Aβ degradation in neuro 2a (N2a)-cells. Our results might help to understand the controversial findings of vitamin E studies and demonstrate that besides the known positive neuroprotective properties, tocotrienols also have negative characteristics with respect to AD.

Towards onset prevention of cognition decline in adults with Down syndrome (The TOP-COG study): A pilot randomised controlled trial

BACKGROUND

Dementia is very common in Down syndrome (trisomy 21) adults. Statins may slow brain amyloid β (Aβ, coded on chromosome 21) deposition and, therefore, delay Alzheimer disease onset. One prospective cohort study with Down syndrome adults found participants on statins had reduced risk of incident dementia, but there are no randomised controlled trials (RCTs) on this issue. Evidence is sparse on the best instruments to detect longitudinal cognitive decline in older Down syndrome adults.

METHODS

TOP-COG was a feasibility/pilot, double-blind RCT of 12 months simvastatin 40 mg versus placebo for the primary prevention of dementia in Alzheimer disease in Down syndrome adults aged 50 years or older. Group allocation was stratified by age, apolipoprotein E (APOE) ε4 allele status, and cholesterol level. Recruitment was from multiple general community sources over 12 months. Adults with dementia, or simvastatin contraindications, were excluded. Main outcomes were recruitment and retention rates. Cognitive decline was measured with a battery of tests; secondary measures were adaptive behaviour skills, general health, and quality of life. Assessments were conducted pre randomisation and at 12 months post randomisation. Blood Aβ40/Aβ42 levels were investigated as a putative biomarker. Results were analysed on an intention-to-treat basis. A qualitative sub-study was conducted and analysed using the Framework Approach to determine recruitment motivators/barriers, and participation experience.

RESULTS

We identified 181 (78 %) of the likely eligible Down syndrome population, and recruited 21 (11.6 %), from an area with a general population size of 3,135,974. Recruitment was highly labour-intensive. Thirteen (62 %) participants completed the full year. Results favoured the simvastatin group. The most appropriate cognitive instrument (regarding ease of completion and detecting change over time) was the Memory for Objects test from the Neuropsychological Assessment of Dementia in Individuals with Intellectual Disabilities battery. Cognitive testing appeared more sensitive than proxy-rated adaptive behaviour, quality of life, or general health scores. Aβ40 levels changed less for the simvastatin group (not statistically significant). People mostly declined to participate because of not wanting to take medication, and not knowing if they would receive simvastatin or placebo. Participants reported enjoying taking part.

CONCLUSION

A full-scale RCT is feasible. It will need 37 % UK population coverage to recruit the required 160 participants. Information/education about the importance of RCT participation is needed for this population.

TRIAL REGISTRATION

ISRCTN67338640 .

Risk factors for dementia diagnosis in German primary care practices

BACKGROUND

Dementia is a psychiatric condition the development of which is associated with numerous aspects of life. Our aim was to estimate dementia risk factors in German primary care patients.

METHODS

The case-control study included primary care patients (70-90 years) with first diagnosis of dementia (all-cause) during the index period (01/2010-12/2014) (Disease Analyzer, Germany), and controls without dementia matched (1:1) to cases on the basis of age, sex, type of health insurance, and physician. Practice visit records were used to verify that there had been 10 years of continuous follow-up prior to the index date. Multivariate logistic regression models were fitted with dementia as a dependent variable and the potential predictors.

RESULTS

The mean age for the 11,956 cases and the 11,956 controls was 80.4 (SD: 5.3) years. 39.0% of them were male and 1.9% had private health insurance. In the multivariate regression model, the following variables were linked to a significant extent with an increased risk of dementia: diabetes (OR: 1.17; 95% CI: 1.10-1.24), lipid metabolism (1.07; 1.00-1.14), stroke incl. TIA (1.68; 1.57-1.80), Parkinson's disease (PD) (1.89; 1.64-2.19), intracranial injury (1.30; 1.00-1.70), coronary heart disease (1.06; 1.00-1.13), mild cognitive impairment (MCI) (2.12; 1.82-2.48), mental and behavioral disorders due to alcohol use (1.96; 1.50-2.57). The use of statins (OR: 0.94; 0.90-0.99), proton-pump inhibitors (PPI) (0.93; 0.90-0.97), and antihypertensive drugs (0.96, 0.94-0.99) were associated with a decreased risk of developing dementia.

CONCLUSIONS

Risk factors for dementia found in this study are consistent with the literature. Nevertheless, the associations between statin, PPI and antihypertensive drug use, and decreased risk of dementia need further investigations.

Linking multiple pathogenic pathways in Alzheimer’s disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder presenting as progressive cognitive decline with dementia that does not, to this day, benefit from any disease-modifying drug. Multiple etiologic pathways have been explored and demonstrate promising solutions. For example, iron ion chelators, such as deferoxamine, are a potential therapeutic solution around which future studies are being directed. Another promising domain is related to thrombin inhibitors. In this minireview, a common pathophysiological pathway is suggested for the pathogenesis of AD to prove that all these mechanisms converge onto the same cascade of neuroinflammatory events. This common pathway is initiated by the presence of vascular risk factors that induce brain tissue hypoxia, which leads to endothelial cell activation. However, the ensuing hypoxia stimulates the production and release of reactive oxygen species and pro-inflammatory proteins. Furthermore, the endothelial activation may become excessive and dysfunctional in predisposed individuals, leading to thrombin activation and iron ion decompartmentalization. The oxidative stress that results from these modifications in the neurovascular unit will eventually lead to neuronal and glial cell death, ultimately leading to the development of AD. Hence, future research in this field should focus on conducting trials with combinations of potentially efficient treatments, such as the combination of intranasal deferoxamine and direct thrombin inhibitors.

Endocrine Risk Factors for Cognitive Impairment

Cognitive impairment, including Alzheimer's disease and other kinds of dementia, is a major health problem in older adults worldwide. Although numerous investigators have attempted to develop effective treatment modalities or drugs, there is no reasonably efficacious strategy for preventing or recovering from cognitive impairment. Therefore, modifiable risk factors for cognitive impairment have received attention, and the growing literature of metabolic risk factors for cognitive impairment has expanded from epidemiology to molecular pathogenesis and therapeutic management. This review focuses on the epidemiological evidence for the association between cognitive impairment and several endocrine risk factors, including insulin resistance, dyslipidemia, thyroid dysfunction, vitamin D deficiency, and subclinical atherosclerosis. Researches suggesting possible mechanisms for this association are reviewed. The research investigating modifiable endocrine risk factors for cognitive impairment provides clues for understanding the pathogenesis of cognitive impairment and developing novel treatment modalities. However, so far, interventional studies investigating the beneficial effect of the "modification" of these "modifiable risk factors" on cognitive impairment have reported variable results. Therefore, well-designed, randomized prospective interventional studies are needed.

Statins and Risk of Bleeding: An Analysis to Evaluate Possible Bias Due to Prevalent Users and Healthy User Aspects

Statins are said to protect against a wide range of diseases. We studied to what extent potential bias influences the results of studies on beneficial side effects of statins. We selected 8,188 atrial fibrillation patients who started treatment with anticoagulants at the Leiden Anticoagulation Clinic in the Netherlands between 2003 and 2009 and experienced 1,683 minor and 451 major bleeds during 18,105 person-years of follow-up. Statins were associated with a risk reduction of 9% for bleeds (hazard ratio = 0.91, 95% confidence interval: 0.82, 1.00). Additionally, analyses were stratified by age, incident users (patients who started statins during follow-up, i.e., an inception cohort), and prevalent statin users (statin users at baseline), as restriction to incident users avoids overoptimistic risk estimates. After stratification, the protective associations disappeared or reversed (range of hazard ratios = 0.99-3.22), except for patients aged 75 years or older. This remaining association could be due to another bias as, according to guidelines, in the elderly, statins should be prescribed only to those with a reasonable life expectancy. This could have resulted in a comparison of fit statin users with less fit nonstatin users (healthy user effect). The apparent protective association of statins on bleeds may be due to bias. We recommend stratification by age and incident and prevalent statin use when studying associations of statins with disease outcomes to avoid overoptimistic risk estimates.

Pleiotropic effects of statins: new therapeutic targets in drug design

The HMG Co-enzyme inhibitors and new lipid-modifying agents expand their new therapeutic target options in the field of medical profession. Statins have been described as the most effective class of drugs to reduce serum cholesterol levels. Since the discovery of the first statin nearly 30 years ago, these drugs have become the main therapeutic approach to lower cholesterol levels. The present scientific research demonstrates numerous non-lipid modifiable effects of statins termed as pleiotropic effects of statins, which could be beneficial for the treatment of various devastating disorders. The most important positive effects of statins are anti-inflammatory, anti-proliferative, antioxidant, immunomodulatory, neuroprotective, anti-diabetes, and antithrombotic, improving endothelial dysfunction and attenuating vascular remodeling besides many others which are discussed under the scope of this review. In particular, inhibition of Rho and its downstream target, Rho-associated coiled-coil-containing protein kinase (ROCK), and their agonistic action on peroxisome proliferator-activated receptors (PPARs) can be viewed as the principle mechanisms underlying the pleiotropic effects of statins. With gradually increasing knowledge of new therapeutic targets of statins, their use has also been advocated in chronic inflammatory disorders for example rheumatoid arthritis (RA) and in systemic lupus erythematosus (SLE). In the scope of review, we highlight statins and their pleiotropic effects with reference to their harmful and beneficial effects as a novel approach for their use in the treatment of devastating disorders. Graphical abstract Pleiotropic effect of statins.

[Influence of lifestyle on neurodegenerative diseases]

Lifestyle factors in midlife have an important influence on the risk of developing a neurodegenerative disease during later life. Data on lifestyle factors exist for Alzheimer's disease and Parkinson's disease. Continuous physical and cognitive activity, a balanced or Mediterranean diet with a high proportion of unsaturated fatty acids, the pharmacological treatment of arterial hypertension, sufficient and unfragmented sleep and possibly treatment with lipophilic statins reduce the risk of developing dementia later in life. Several studies in recent years have provided evidence that during the last decades the age-adjusted incidence of dementia has decreased. This is probably due to a healthier lifestyle and the treatment of risk factors. Continuous physical activity also decreases the likelihood of developing Parkinson's disease. Whether lifestyle factors also have an influence on the course and the progression of Alzheimer's and Parkinson's diseases in the symptomatic stages is unknown.

Simvastatin enhances NMDA receptor GluN2B expression and phosphorylation of GluN2B and GluN2A through increased histone acetylation and Src signaling in hippocampal CA1 neurons

Simvastatin (SV) can improve cognitive deficits in Alzheimer's disease patients and mice. Herein, we report that the administration of SV (20 mg/kg) for 5 days in mice (SV-mice) or the treatment of slices with SV (10 μM) for 4 h (SV-slices) could increase the density of NMDA-evoked inward currents (INMDA) in hippocampal CA1 pyramidal cells, which were blocked by farnesol (FOH) that converts farnesyl pyrophosphate (FPP), but not geranylgeraniol (GGOH) that increases geranylgeranylpyrophosphate (GGPP). Sensitivity of INMDA to ifenprodil in SV-mice or SV-slices was significantly increased. The levels of hippocampal GluN2B and GluN2A or Src phosphorylation in SV-mice or SV-slices were higher than controls, which were sensitive to FOH. The Src inhibitor PP2 could inhibit the SV-enhanced phosphorylation of GluN2B and GluN2A and SV-augmented INMDA, but PI3K inhibitor LY294002 did not. The levels of GluN2B mRNA and protein were elevated in SV-mice, which was abolished by FOH, but not by GGOH or PP2. Furthermore, the histone H3K9 and H3K27 acetylation of GluN2B promoter was increased in SV-mice, which was suppressed by FOH rather than GGOH or PP2. In control mice and slices, the reduction of FPP by farnesyl transferase inhibitor could increase the levels of GluN2B expression, the histone H3K9 and H3K27 acetylation and enhance the phosphorylation of GluN2B, GluN2A and Src. The findings indicate that the administration of SV can enhance GluN2B expression and GluN2B and GluN2A phosphorylation leading to augmentation of NMDAR activity through reducing FPP to increase histone acetylation of GluN2B and Src signaling.

Could drugs inhibiting the mevalonate pathway also target cancer stem cells?

Understanding the connection between metabolic pathways and cancer is very important for the development of new therapeutic approaches based on regulatory enzymes in pathways associated with tumorigenesis. The mevalonate cascade and its rate-liming enzyme HMG CoA-reductase has recently drawn the attention of cancer researchers because strong evidences arising mostly from epidemiologic studies, show that it could promote transformation. Hence, these studies pinpoint HMG CoA-reductase as a candidate proto-oncogene. Several recent epidemiological studies, in different populations, have proven that statins are beneficial for the treatment-outcome of various cancers, and may improve common cancer therapy strategies involving alkylating agents, and antimetabolites. Cancer stem cells/cancer initiating cells (CSC) are key to cancer progression and metastasis. Therefore, in the current review we address the different effects of statins on cancer stem cells. The mevalonate cascade is among the most pleiotropic, and highly interconnected signaling pathways. Through G-protein-coupled receptors (GRCP), it integrates extra-, and intracellular signals. The mevalonate pathway is implicated in cell stemness, cell proliferation, and organ size regulation through the Hippo pathway (e.g. Yap/Taz signaling axis). This pathway is a prime preventive target through the administration of statins for the prophylaxis of obesity-related cardiovascular diseases. Its prominent role in regulation of cell growth and stemness also invokes its role in cancer development and progression. The mevalonate pathway affects cancer metastasis in several ways by: (i) affecting epithelial-to-mesenchymal transition (EMT), (ii) affecting remodeling of the cytoskeleton as well as cell motility, (iii) affecting cell polarity (non-canonical Wnt/planar pathway), and (iv) modulation of mesenchymal-to-epithelial transition (MET). Herein we provide an overview of the mevalonate signaling network. We then briefly highlight diverse functions of various elements of this mevalonate pathway. We further discuss in detail the role of elements of the mevalonate cascade in stemness, carcinogenesis, cancer progression, metastasis and maintenance of cancer stem cells.

Simvastatin and atorvastatin facilitates amyloid β-protein degradation in extracellular spaces by increasing neprilysin secretion from astrocytes through activation of MAPK/Erk1/2 pathways

One of the major neuropathological hallmarks of Alzheimer's disease (AD) is the deposition of amyloid β-protein (Aβ) in the brain. Aβ accumulation seems to arise from an imbalance between Aβ production and clearance. Neprilysin (NEP) and insulin-degrading enzyme (IDE) are the important Aβ-degrading enzymes in the brain, and deficits in their expression may promote Aβ deposition in patients with sporadic late-onset AD. Statins, which are used clinically for reducing cholesterol levels, can exert beneficial effects on AD. Therefore, we examined whether various statins are associated with Aβ degradation by inducing NEP and IDE expression, and then evaluating the relation between activation of intracellular signaling transduction, inhibition of cholesterol production, and morphological changes to astrocytes. Treating cultured rat astrocytes with simvastatin and atorvastatin significantly decreased the expression of NEP but not IDE in a concentration- and time-dependent manner. The decrease in NEP expression was a result of activation of extracellular signal-regulated kinase (ERK) but not the reduction of cholesterol synthesis pathway. This NEP reduction was achieved by the release to the extracellular space of cultured astrocytes. Furthermore, the cultured medium prepared from simvastatin- and atorvastatin-treated astrocytes significantly induced the degradation of exogenous Aβ. These results suggest that simvastatin and atorvastatin induce the increase of Aβ degradation of NEP on the extracellular of astrocytes by inducing ERK-mediated pathway activity and that these reagents regulate the differential mechanisms between the secretion of NEP, the induction of cholesterol reduction, and the morphological changes in the cultured astrocytes.

Statins for the prevention of dementia

BACKGROUND

This is an update of a Cochrane review first published in 2001 and then updated in 2009. Vascular risk factors including high cholesterol levels increase the risk of dementia due to Alzheimer's disease and of vascular dementia. Some observational studies have suggested an association between statin use and lowered incidence of dementia.

OBJECTIVES

To evaluate the efficacy and safety of statins for the prevention of dementia in people at risk of dementia due to their age and to determine whether the efficacy and safety of statins for this purpose depends on cholesterol level, apolipoprotein E (ApoE) genotype or cognitive level.

SEARCH METHODS

We searched ALOIS (the Specialized Register of the Cochrane Dementia and Cognitive Improvement Group), The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL, LILACS, ClinicalTrials.gov and the World Health Organization (WHO) Portal on 11 November 2015.

SELECTION CRITERIA

We included double-blind, randomised, placebo-controlled trials in which statins were administered for at least 12 months to people at risk of dementia.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included two trials with 26,340 participants aged 40 to 82 years of whom 11,610 were aged 70 or older. All participants had a history of, or risk factors for, vascular disease. The studies used different statins (simvastatin and pravastatin). Mean follow-up was 3.2 years in one study and five years in one study. The risk of bias was low. Only one study reported on the incidence of dementia (20,536 participants, 31 cases in each group; odds ratio (OR) 1.00, 95% confidence interval (CI) 0.61 to 1.65, moderate quality evidence, downgraded due to imprecision). Both studies assessed cognitive function, but at different times using different scales, so we judged the results unsuitable for a meta-analysis. There were no differences between statin and placebo groups on five different cognitive tests (high quality evidence). Rates of treatment discontinuation due to non-fatal adverse events were less than 5% in both studies and there was no difference between statin and placebo groups in the risk of withdrawal due to adverse events (26,340 participants, 2 studies, OR 0.94, 95% CI 0.83 to 1.05).

AUTHORS' CONCLUSIONS

There is good evidence that statins given in late life to people at risk of vascular disease do not prevent cognitive decline or dementia. Biologically, it seems feasible that statins could prevent dementia due to their role in cholesterol reduction and initial evidence from observational studies was very promising. However, indication bias may have been a factor in these studies and the evidence from subsequent RCTs has been negative. There were limitations in the included studies involving the cognitive assessments used and the inclusion of participants at moderate to high vascular risk only.

Role of Liver X Receptor in AD Pathophysiology

Alzheimer's disease (AD) is the major cause of dementia worldwide. The pharmacological activation of nuclear receptors (Liver X receptors: LXRs or Retinoid X receptors: RXR) has been shown to induce overexpression of the ATP-Binding Cassette A1 (ABCA1) and Apolipoprotein E (ApoE), changes that are associated with improvement in cognition and reduction of amyloid beta pathology in amyloidogenic AD mouse models (i.e. APP, PS1: 2tg-AD). Here we investigated whether treatment with a specific LXR agonist has a measurable impact on the cognitive impairment in an amyloid and Tau AD mouse model (3xTg-AD: 12-months-old; three months treatment). The data suggests that the LXR agonist GW3965 is associated with increased expression of ApoE and ABCA1 in the hippocampus and cerebral cortex without a detectable reduction of the amyloid load. We also report that most cells overexpressing ApoE (86±12%) are neurons localized in the granular cell layer of the hippocampus and entorhinal cortex. In the GW3965 treated 3xTg-AD mice we also observed reduction in astrogliosis and increased number of stem and proliferating cells in the subgranular zone of the dentate gyrus. Additionally, we show that GW3965 rescued hippocampus long term synaptic plasticity, which had been disrupted by oligomeric amyloid beta peptides. The effect of GW3965 on synaptic function was protein synthesis dependent. Our findings identify alternative functional/molecular mechanisms by which LXR agonists may exert their potential benefits as a therapeutic strategy against AD.

Effects of rs3846662 Variants on HMGCR mRNA and Protein Levels and on Markers of Alzheimer's Disease Pathology

3-Hydroxy-3-methyglutaryl coenzyme A reductase (HMGCR) is a cholesterol-regulating gene with statin relevance. rs3846662 being involved in regulation of HMGCR alternative splicing, we explored its impact on HMGCR messenger RNA (mRNA) and protein levels in the brain and the associations between those levels and levels of Alzheimer's disease pathological markers. We used brain samples derived from a cohort of 33 non-demented controls and 90 Alzheimer's disease autopsied-confirmed cases. HMGCR mRNA levels were determined in the frontal cortex (n = 114) and cerebellum (n = 110) using Taqman-qPCR, and HMGCR protein levels were determined in the frontal cortex (n = 117) using a commercial enzyme immunoassay. While densities of neurofibrillary tangles and senile plaques were determined in the frontal cortex (n = 74), total tau, phosphorylated Tau, and beta-amyloid 1-42 levels were determined in the frontal cortex (n = 94) and cerebellum (n = 91) using commercial enzyme immunoassays. Despite an increase in full-length HMGCR mRNA ratio in the frontal cortex of women carrying the AA genotype, there were no associations between rs3846662 and HMGCR mRNA or protein levels. An increased Δ13 HMGCR mRNA ratio was associated with increased levels of HMGCR proteins and neurofibrillary tangles in the frontal cortex but with reduced beta-amyloid 1-42 levels in the cerebellum, suggesting a brain cell type- or a disease progression-dependent association.

Potential of tocotrienols in the prevention and therapy of Alzheimer's disease

Currently there is no cure for Alzheimer's disease (AD); clinical trials are underway to reduce amyloid generation and deposition, a neuropathological hallmark in brains of AD patients. While genetic factors and neuroinflammation contribute significantly to AD pathogenesis, whether increased cholesterol level is a causative factor or a result of AD is equivocal. Prenylation of proteins regulating neuronal functions requires mevalonate-derived farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). The observation that the levels of FPP and GGPP, but not that of cholesterol, are elevated in AD patients is consistent with the finding that statins, competitive inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, reduce FPP and GGPP levels and amyloid β protein production in preclinical studies. Retrospective studies show inverse correlations between incidence of AD and the intake and serum levels of the HMG CoA reductase-suppressive tocotrienols; tocopherols show mixed results. Tocotrienols, but not tocopherols, block the processing and nuclear localization of sterol regulatory element binding protein-2, the transcriptional factor for HMG CoA reductase and FPP synthase, and enhance the degradation of HMG CoA reductase. Consequently, tocotrienols deplete the pool of FPP and GGPP and potentially blunt prenylation-dependent AD pathogenesis. The antiinflammatory activity of tocotrienols further contributes to their protection against AD. The mevalonate- and inflammation-suppressive activities of tocotrienols may represent those of an estimated 23,000 mevalonate-derived plant secondary metabolites called isoprenoids, many of which are neuroprotective. Tocotrienol-containing plant foods and tocotrienol derivatives and formulations with enhanced bioavailability may offer a novel approach in AD prevention and treatment.

Statins induce insulin-degrading enzyme secretion from astrocytes via an autophagy-based unconventional secretory pathway

Background

Insulin degrading enzyme (IDE) is a major protease of amyloid beta peptide (Aβ), a prominent toxic protein in Alzheimer’s disease (AD) pathogenesis. Previous studies suggested that statins promote IDE secretion; however, the underlying mechanism is unknown, as IDE has no signal sequence.

Results

In this study, we found that simvastatin (0.2 μM for 12 h) induced the degradation of extracellular Aβ₄₀, which depended on IDE secretion from primary astrocytes. In addition, simvastatin increased IDE secretion from astrocytes in a time- and dose-dependent manner. Moreover, simvastatin-mediated IDE secretion was mediated by an autophagy-based unconventional secretory pathway, and autophagic flux regulated simvastatin-mediated IDE secretion. Finally, simvastatin activated autophagy via the LKB1-AMPK-mTOR signaling pathway in astrocytes.

Conclusions

These results demonstrate a novel pathway for statin-mediated IDE secretion from astrocytes. Modulation of this pathway could provide a potential therapeutic target for treatment of Aβ pathology by enhancing extracellular clearance of Aβ.

Electronic supplementary material

The online version of this article (doi:10.1186/s13024-015-0054-3) contains supplementary material, which is available to authorized users.

Statins and cognitive function: an updated review

Ischemic heart disease remains the leading cause of death in the USA. Statins have substantially contributed to the decline in mortality due to heart disease. Historically, statins are hypothesized to be neuroprotective and beneficial in dementia, but recent reports have suggested an association with transient cognitive decline. We have critically appraised the relationship between statins and cognitive function in this review. Most of the data are observational and reported a protective effect of statins on dementia and Alzheimer's disease in patients with normal cognition at baseline. Few studies, including two randomized control trials, were unable to find a statistically significant decrease in the risk or improvement in patients with established dementia or decline in cognitive function with statin use. As more randomized control trials are required to definitively settle this, cardiovascular benefits of statins must be weighed against the risks of cognitive decline on an individual basis.

Statins Reduces the Risk of Dementia in Patients with Late-Onset Depression: A Retrospective Cohort Study

Objective

Patients with late-onset depression (LOD) have been reported to run a higher risk of subsequent dementia. The present study was conducted to assess whether statins can reduce the risk of dementia in these patients.

Methods

We used the data from National Health Insurance of Taiwan during 1996–2009. Standardized Incidence Ratios (SIRs) were calculated for LOD and subsequent dementia. The criteria for LOD diagnoses included age ≥65 years, diagnosis of depression after 65 years of age, at least three service claims, and treatment with antidepressants. The time-dependent Cox proportional hazards model was applied for multivariate analyses. Propensity scores with the one-to-one nearest-neighbor matching model were used to select matching patients for validation studies. Kaplan-Meier curve estimate was used to measure the group of patients with dementia living after diagnosis of LOD.

Results

Totally 45,973 patients aged ≥65 years were enrolled. The prevalence of LOD was 12.9% (5,952/45,973). Patients with LOD showed to have a higher incidence of subsequent dementia compared with those without LOD (Odds Ratio: 2.785; 95% CI 2.619–2.958). Among patients with LOD, lipid lowering agent (LLA) users (for at least 3 months) had lower incidence of subsequent dementia than non-users (Hazard Ratio = 0.781, 95% CI 0.685–0.891). Nevertheless, only statins users showed to have reduced risk of dementia (Hazard Ratio = 0.674, 95% CI 0.547–0.832) while other LLAs did not, which was further validated by Kaplan-Meier estimates after we used the propensity scores with the one-to-one nearest-neighbor matching model to control the confounding factors.

Conclusions

Statins may reduce the risk of subsequent dementia in patients with LOD.

Impact on cognitive function-are all statins the same?

Dementia is a major public health concern, affecting an estimated 7% of the population over 65 and 30% over 80 years of age. There is mounting evidence in the literature from meta-analyses of high-quality prospective cohort studies that statins may have a positive impact in reducing the incidence of dementia. Little is known, however, on whether certain types of statins are more impactful than others. This narrative review specifically explores the various properties of different statin types and whether these differences lead to a clinically significant differential impact on cognitive function. We critically evaluate the literature, emphasizing interesting and important new findings, and overall aim to bring the reader up-to-date on evidence-based recommendations.

Potential role of statins in the intracerebral hemorrhage and subarachnoid hemorrhage

Statins are used in primary and secondary prevention of cardiovascular episodes. Most of recent studies regard ischemic stroke. There are more emerging results of studies suggesting usefulness of these drugs in the other types of stroke e.g. intracerebral hemorrhage (ICH) and subarachnoid hemorrhage (SAH). Searching for new methods of treatment is important, because both ICH and SAH lead to poor prognosis and severe psychomotor disability. The unquestionable role of inflammatory factors in the pathogenesis of these disorders justifies considering statin treatment. Previous results are contradictory, thus in present study we review results of studies and try to explain the potential pathomechanism of statin use in hemorrhagic strokes.

Metabolic Risk Factors of Sporadic Alzheimer's Disease: Implications in the Pathology, Pathogenesis and Treatment

Alzheimer's disease (AD), the major cause of dementia among the elderly world-wide, manifests in familial and sporadic forms, and the latter variety accounts for the majority of the patients affected by this disease. The etiopathogenesis of sporadic AD is complex and uncertain. The autopsy studies of AD brain have provided limited understanding of the antemortem pathogenesis of the disease. Experimental AD research with transgenic animal or various cell based models has so far failed to explain the complex and varied spectrum of AD dementia. The review, therefore, emphasizes the importance of AD related risk factors, especially those with metabolic implications, identified from various epidemiological studies, in providing clues to the pathogenesis of this complex disorder. Several metabolic risk factors of AD like hypercholesterolemia, hyperhomocysteinemia and type 2 diabetes have been studied extensively both in epidemiology and experimental research, while much less is known about the role of adipokines, pro-inflammatory cytokines and vitamin D in this context. Moreover, the results from many of these studies have shown a degree of variability which has hindered our understanding of the role of AD related risk factors in the disease progression. The review also encompasses the recent recommendations regarding clinical and neuropathological diagnosis of AD and brings out the inherent uncertainty and ambiguity in this area which may have a distinct impact on the outcome of various population-based studies on AD-related risk factors.

HMGCR is a genetic modifier for risk, age of onset and MCI conversion to Alzheimer's disease in a three cohorts study

Several retrospective epidemiological studies report that utilization of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) inhibitors called statins at mid-life can reduce the risk of developing sporadic Alzheimer's disease (AD) by as much as 70%. Conversely, the administration of these inhibitors in clinically diagnosed subjects with AD confers little or no benefits over time. Here, we investigated the association between AD and HMGCR rs3846662, a polymorphism known to be involved in the regulation of HMGCR exon 13 skipping, in a founder population and in two distinct mixed North American populations of converting mild cognitively impaired (MCI) subjects (Alzheimer's disease Cooperative study (ADCS) and Alzheimer's disease Neuroimaging Initiative (ADNI) cohorts). Targeting more specifically women, the G allele negative (G-) AD subjects exhibit delayed age of onset of AD (P=0.017) and significantly reduced risk of AD (OR: 0.521; P=0.0028), matching the effect size reported by the apolipoprotein E type 2 variant. Stratification for APOE4 in a large sample of MCI patients from the ADCS cohort revealed a significant protective effect of G negative carriers on AD conversion 3 years after MCI diagnosis (odds ratio (OR): 0.554; P=0.041). Conversion rate among APOE4 carriers with the HMGCR's G negative allele was markedly reduced (from 76% to 27%) to levels similar to APOE4 non-carriers (27.14%), which strongly indicate protection. Conversion data from the independent ADNI cohort also showed significantly reduced MCI or AD conversion among APOE4 carriers with the protective A allele (P=0.005). In conclusion, HMGCR rs3846662 acts as a potent genetic modifier for AD risk, age of onset and conversion.

Lovastatin Differentially Affects Neuronal Cholesterol and Amyloid-β Production in vivo and in vitro

BACKGROUND AND AIMS

Epidemiological and experimental studies indicate that high cholesterol may increase susceptibility to age-associated neurodegenerative disorders, such as Alzheimer's disease (AD). Thus, it has been suggested that statins, which are inhibitors of the enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), may be a useful therapeutic tool to diminish the risk of AD. However, several studies that analyzed the therapeutic benefits of statins have yielded conflicting results. Herein, we investigated the role of lovastatin on neuronal cholesterol homeostasis and its effects on amyloid β protein production in vivo and in vitro.

METHODS AND RESULTS

Lovastatin effects were analyzed in vitro using differentiated human neuroblastoma cells and in vivo in a lovastatin-fed rat model. We demonstrated that lovastatin can differentially affect the expression of APP and Aβ production in vivo and in vitro. Lovastatin-induced HMGCR inhibition was detrimental to neuronal survival in vitro via a mechanism unrelated to the reduction of cholesterol. We found that in vivo, dietary cholesterol was associated with increased Aβ production in the cerebral cortex, and lovastatin was not able to reduce cholesterol levels. However, lovastatin induced a remarkable increase in the mature form of the sterol regulatory element-binding protein-2 (SREBP-2) as well as its target gene HMGCR, in both neuronal cells and in the brain.

CONCLUSIONS

Lovastatin modifies the mevalonate pathway without affecting cholesterol levels in vivo and is able to reduce Aβ levels only in vitro.

Cholesterol-induced astrocyte activation is associated with increased amyloid precursor protein expression and processing

Cholesterol is essential for maintaining lipid raft integrity and has been regarded as a crucial regulatory factor for amyloidogenesis in Alzheimer's disease (AD). The vast majority of studies on amyloid precursor protein (APP) metabolism and amyloid β-protein (Aβ) production have focused on neurons. The role of astrocytes remains largely unexplored, despite the presence of activated astrocytes in the brains of most patients with AD and in transgenic models of the disease. The role of cholesterol in Aβ production has been thoroughly studied in neurons and attributed to the participation of lipid rafts in APP metabolism. Thus, in this study, we analyzed the effect of cholesterol loading in astrocytes and analyzed the expression and processing of APP. We found that cholesterol exposure induced astrocyte activation, increased APP content, and enhanced the interaction of APP with BACE-1. These effects were associated with an enrichment of ganglioside GM1-cholesterol patches in the astrocyte membrane and with increased ROS production. GLIA 2015;63:2010-2022.

Statins and the risk of dementia in patients with atrial fibrillation: A nationwide population-based cohort study

BACKGROUND

Atrial fibrillation (AF) is associated with cognitive decline and may contribute to an increased risk of dementia. The goal of the present study was to investigate whether statin use prevented non-vascular dementia in subjects with AF.

METHODS

Data from the National Health Insurance Research Database of Taiwan were used in this study. The study group comprised 51,253 AF subjects aged ≥ 60 years who had received statin treatment. For each study patient, four age- and sex-matched AF subjects without statin exposure were selected as the control group (n=205,012). The risk of non-vascular dementia was compared between the statin and control groups.

RESULTS

During the follow-up period, 17,201 patients experienced non-vascular dementia. The annual incidence of non-vascular dementia was lower in the statin group than in the control group (1.89% vs. 2.20%; p<0.001). Statin use exhibited a protective effect on the occurrence of non-vascular dementia, with an adjusted hazard ratio (HR) of 0.832 (95% confidence interval=0.801-0.864). Among statin types, the use of rosuvastatin was associated with the largest risk reduction (adjusted HR=0.661). Statin exposure duration was related inversely to the risk of non-vascular dementia.

CONCLUSIONS

In this large-scale nationwide cohort study, statin use was associated with a lower risk of non-vascular dementia in AF. Use of more potent statin and longer exposure time may be associated with greater benefits.

[Oxidative stress and its effect on cells functional activity of alzheimer's disease]

The paper summarizes literature data on the importance of oxidative stress as one of the pathogenetic mechanisms in Alzheimer's disease. The paper describes the main specific and nonspecific ways of reactive oxygen species generation in the course of the disease development. The effect of reactive oxygen species generated by the functional activity of cells, i.e. apoptosis and mitotic cycle, is shown. The role of the regulatory system of nodal cells is performed by phosphorylation/dephosphorylation process which is associated with intense phosphorylation of tau protein and mitosis-specific proteins. In Alzheimer's disease, the regulating function of peptidyl-prolyl isomerases in particular of Pin1 associated with maintaining a balanced state of phosphorylation/dephosphorylation processes is disturbed. Taking into consideration the multifactorial impairment of the cell cycle control, this process should be considered from the standpoint of the general state of metabolic processes, and oxidative stress has one of the key positions in aging.

Atorvastatin prevents Aβ oligomer-induced neurotoxicity in cultured rat hippocampal neurons by inhibiting Tau cleavage

AIM

The proteolytic cleavage of Tau is involved in Aβ-induced neuronal dysfunction and cell death. In this study, we investigated whether atorvastatin could prevent Tau cleavage and hence prevent Aβ1-42 oligomer (AβO)-induced neurotoxicity in cultured cortical neurons.

METHODS

Cultured rat hippocampal neurons were incubated in the presence of AβOs (1.25 μmol/L) with or without atorvastatin pretreatment. ATP content and LDH in the culture medium were measured to assess the neuronal viability. Caspase-3/7 and calpain protease activities were detected. The levels of phospho-Akt, phospho-Erk1/2, phospho-GSK3β, p35 and Tau proteins were measured using Western blotting.

RESULTS

Treatment of the neurons with AβO significantly decreased the neuronal viability, induced rapid activation of calpain and caspase-3/7 proteases, accompanied by Tau degradation and relatively stable fragments generated in the neurons. AβO also suppressed Akt and Erk1/2 kinase activity, while increased GSK3β and Cdk5 activity in the neurons. Pretreatment with atorvastatin (0.5, 1, 2.5 μmol/L) dose-dependently inhibited AβO-induced activation of calpain and caspase-3/7 proteases, and effectively diminished the generation of Tau fragments, attenuated synaptic damage and increased neuronal survival. Atorvastatin pretreatment also prevented AβO-induced decreases in Akt and Erk1/2 kinase activity and the increases in GSK3β and Cdk5 kinase activity.

CONCLUSION

Atorvastatin prevents AβO-induced neurotoxicity in cultured rat hippocampal neurons by inhibiting calpain- and caspase-mediated Tau cleavage.

Liver X receptors and cholesterol metabolism: role in ventral midbrain development and neurodegeneration

The development of the ventral midbrain is orchestrated by a number of cell-extrinsic and -intrinsic factors that control critical processes, such as the patterning of the neural tube along the main body axis and the specification of diverse neuronal cell types in distinct positions of the neural tube. Subsequently, the regulation of neurogenesis and survival— acquire particular relevance in order to define the final size of diverse neuronal populations. In a series of studies during the last few years, we have identified liver X receptors (LXRs) as critical regulators of ventral midbrain development. Moreover, specific cholesterol derivatives present in the midbrain or in the cerebrospinal fluid were identified as LXR ligands, capable of specifically and selectively regulating neurogenesis and the survival of distinct neuronal populations, including midbrain dopamine neurons. These studies have shown that cholesterol derivatives are an entirely new class of factors capable of regulating both neuronal survival and neurogenesis, thus providing a direct link between cholesterol metabolism and brain development. In addition, LXRs and cholesterol metabolism were found to play a critical role in regulating the balance between neuronal survival and death in diverse midbrain neuronal populations. In this review, we will focus on these two aspects and on the possible role of cholesterol metabolism and LXRs in neurodegeneration.

Statins and memory loss: An Australian experience

BACKGROUND

Statins are a first-line drug treatment for hypercholesterolaemia. Recently there has been general public and media interest surrounding uses and side effects of statins, including memory loss.

AIMS

We analysed an Australian experience in statin usage in an attempt to improve understanding of the relationship between statins and memory-related adverse events.

METHODS

Total adverse events (TAE) and adverse events with single suspected medicines (SSM) for memory loss and other memory-related adverse events were searched for statin compounds from January 1992 to May 2013, using the Medicare Australia and Pharmaceutical Benefits Scheme (PBS) websites and Therapeutic Goods Administration (TGA) adverse events data. TAE and SSM were compared to the number of prescriptions by item number searched using the PBS. The process was repeated for non-statin cholesterol-lowering drugs.

RESULTS

The most common adverse event was amnesia (167 events for statins and six for non-statins). There were 239 TAE (incidence rate=0.88) listed for statins and 10 for non-statins (incidence rate=0.53). There were 217 SSM events listed for the statins (incidence rate = 0.08) and eight for the alternatives (incident rate=0.04). The differences between TAE and SSM incidence rates between statins and non-statins drugs were not significant (both p values >0.05).

CONCLUSION

We found that there were no differences in memory-related adverse events between statins and other cholesterol-lowering medications using Australian PBS and TGA adverse events data.

α-Synuclein-induced synapse damage in cultured neurons is mediated by cholesterol-sensitive activation of cytoplasmic phospholipase A2

The accumulation of aggregated forms of the α-synuclein (αSN) is associated with the pathogenesis of Parkinson's disease (PD) and Dementia with Lewy Bodies. The loss of synapses is an important event in the pathogenesis of these diseases. Here we show that aggregated recombinant human αSN, but not βSN, triggered synapse damage in cultured neurons as measured by the loss of synaptic proteins. Pre-treatment with the selective cytoplasmic phospholipase A2 (cPLA2) inhibitors AACOCF3 and MAFP protected neurons against αSN-induced synapse damage. Synapse damage was associated with the αSN-induced activation of synaptic cPLA2 and the production of prostaglandin E2. The activation of cPLA2 is the first step in the generation of platelet-activating factor (PAF) and PAF receptor antagonists (ginkgolide B or Hexa-PAF) also protect neurons against αSN-induced synapse damage. αSN-induced synapse damage was also reduced in neurons pre-treated with the cholesterol synthesis inhibitor (squalestatin). These results are consistent with the hypothesis that αSN triggered synapse damage via hyperactivation of cPLA2. They also indicate that αSN-induced activation of cPLA2 is influenced by the cholesterol content of membranes. Inhibitors of this pathway that can cross the blood brain barrier may protect against the synapse damage seen during PD.

Statins enhance cognitive performance in object location test in albino Swiss mice: involvement of beta-adrenoceptors

Statins are inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, thereby inhibiting cell synthesis of cholesterol and isoprenoids. Moreover, several studies have been evaluating pleiotropic effects of statins, mainly because they present neuroprotective effects in various pathological conditions. However, knowledge about behavioral effects of statins per se is relatively scarce. Considering these facts, we aimed to analyze behavioral responses of atorvastatin or simvastatin-treated mice in the open field test, elevated plus maze and object location test. Atorvastatin treatment for 7 consecutive days at 1 mg/kg or 10 mg/kg (v.o.) or simvastatin 10 mg/kg or 20 mg/kg enhanced cognitive performance in object location test when compared to control group (saline-treated mice). Simvastatin effects on mice performance in the object location test was abolished by post-training infusion of the beta-adrenoceptor antagonist propranolol. Atorvastatin and simvastatin did not change the behavioral response in open field and elevated plus-maze (EPM) tests in any of the used doses. These data demonstrate the positive effects of both statins in cognitive processes in mice, without any alteration in locomotor parameters in the open field test or anxiolytic-like behavior in EPM. In conclusion, we demonstrate that atorvastatin and simvastatin per se improve the cognitive performance in a rodent model of spatial memory and this effect is related to beta-adrenergic receptors modulation.

Lipids in Amyloid-β Processing, Aggregation, and Toxicity

Aggregation of amyloid-beta (Aβ) peptide is the major event underlying neuronal damage in Alzheimer's disease (AD). Specific lipids and their homeostasis play important roles in this and other neurodegenerative disorders. The complex interplay between the lipids and the generation, clearance or deposition of Aβ has been intensively investigated and is reviewed in this chapter. Membrane lipids can have an important influence on the biogenesis of Aβ from its precursor protein. In particular, increased cholesterol in the plasma membrane augments Aβ generation and shows a strong positive correlation with AD progression. Furthermore, apolipoprotein E, which transports cholesterol in the cerebrospinal fluid and is known to interact with Aβ or compete with it for the lipoprotein receptor binding, significantly influences Aβ clearance in an isoform-specific manner and is the major genetic risk factor for AD. Aβ is an amphiphilic peptide that interacts with various lipids, proteins and their assemblies, which can lead to variation in Aβ aggregation in vitro and in vivo. Upon interaction with the lipid raft components, such as cholesterol, gangliosides and phospholipids, Aβ can aggregate on the cell membrane and thereby disrupt it, perhaps by forming channel-like pores. This leads to perturbed cellular calcium homeostasis, suggesting that Aβ-lipid interactions at the cell membrane probably trigger the neurotoxic cascade in AD. Here, we overview the roles of specific lipids, lipid assemblies and apolipoprotein E in Aβ processing, clearance and aggregation, and discuss the contribution of these factors to the neurotoxicity in AD.

Statin use and cognitive function: population-based observational study with long-term follow-up

We aimed to evaluate the association between statin use and cognitive function. Cognitive function was measured with the Ruff Figural Fluency Test (RFFT; worst score, 0; best score, 175 points) and the Visual Association Test (VAT; low performance, 0-10; high performance, 11-12 points) in an observational study that included 4,095 community-dwelling participants aged 35-82 years. Data on statin use were obtained from a computerized pharmacy database. Analysis were done for the total cohort and subsamples matched on cardiovascular risk (N = 1232) or propensity score for statin use (N = 3609). We found that a total of 904 participants (10%) used a statin. Statin users were older than non-users: mean age (SD) 61 (10) vs. 52 (11) years (p<0.001). The median duration of statin use was 3.8 (interquartile range, 1.6-4.5) years. Unadjusted, statin users had worse cognitive performance than non-users. The mean RFFT score (SD) in statin users and non-users was 58 (23) and 72 (26) points, respectively (p<0.001). VAT performance was high in 261 (29%) statin users and 1351 (43%) non-users (p<0.001). However, multiple regression analysis did not show a significant association of RFFT score with statin use (B, -0.82; 95%CI, -2.77 to 1.14; p = 0.41) nor with statin solubility, statin dose or duration of statin use. Statin users with high doses or long-term use had similar cognitive performance as non-users. This was found in persons with low as well as high cardiovascular risk, and in younger as well as older subjects. Also, the mean RFFT score per quintile of propensity score for statin use was comparable for statin users and non-users. Similar results were found for the VAT score as outcome measure. In conclusion, statin use was not associated with cognitive function. This was independent of statin dose or duration of statin use.

Regulation of Calcium-Independent Phospholipase A2 Expression by Adrenoceptors and Sterol Regulatory Element Binding Protein-Potential Crosstalk Between Sterol and Glycerophospholipid Mediators

Calcium-independent phospholipase A2 (iPLA2) is an 85-kDa enzyme that releases docosahexaenoic acid (DHA) from glycerophospholipids. DHA can be metabolized to resolvins and neuroprotectins that have anti-inflammatory properties and effects on neural plasticity. Recent studies show an important role of prefrontal cortical iPLA2 in hippocampo-prefrontal cortical LTP and antidepressant-like effect of the norepinephrine reuptake inhibitor (NRI) antidepressant, maprotiline. In this study, we elucidated the cellular mechanisms through which stimulation of adrenergic receptors could lead to increased iPLA2 expression. Treatment of SH-SY5Y neuroblastoma cells with maprotiline, another tricyclic antidepressant with noradrenaline reuptake inhibiting properties, nortriptyline, and the adrenergic receptor agonist, phenylephrine, resulted in increased iPLA2β mRNA expression. This increase was blocked by inhibitors to alpha-1 adrenergic receptor, mitogen-activated protein (MAP) kinase or extracellular signal-regulated kinase (ERK) 1/2, and sterol regulatory element-binding protein (SREBP). Maprotiline and phenylephrine induced binding of SREBP-2 to sterol regulatory element (SRE) region on the iPLA2 promoter, as determined by electrophoretic mobility shift assay (EMSA). Together, results indicate that stimulation of adrenoreceptors causes increased iPLA2 expression via MAP kinase/ERK 1/2 and SREBP, and suggest a possible mechanism for effect of CNS noradrenaline on neural plasticity and crosstalk between sterol and glycerophospholipid mediators, that may play a role in physiological or pathophysiological processes in the brain and other organs.

Statin use and risk of depression: a Swedish national cohort study

BACKGROUND

Statin medications, used to prevent heart disease by reducing cholesterol, also reduce inflammation and protect against oxidative damage. As inflammation and oxidative stress occur in depression, there is interest in their potential to reduce depression risk. We investigated whether use of statin medications was associated with a change in the risk of developing depression in a very large Swedish national cohort (n = 4,607,990).

METHODS

National register data for adults ≥40yr was analyzed to obtain information about depression diagnoses and prescriptions of statin medications between 2006 and 2008. Associations were tested using logistic regression.

RESULTS

Use of any statin was shown to reduce the odds of depression by 8% compared to individuals not using statin medications (OR = 0.92, 95% CI, 0.89-0.96; p < 0.001). Simvastatin had a protective effect (OR = 0.93, 95% CI, 0.89-0.97; p = 0.001), whereas atorvastatin was associated with increased risk of depression (OR = 1.11, 95% CI, 1.01-1.22; p = 0.032). There was a stepwise decrease in odds ratio with increasing age (OR ≥ 40 years = 0.95, OR ≥ 50 years = 0.91, OR ≥ 60 years = 0.85, OR ≥ 70 years = 0.81).

CONCLUSIONS

The use of any statin was associated with a reduction in risk of depression in individuals over the age of 40. Clarification of the strength of these protective effects, the clinical relevance of these effects and determination of which statins are most effective is needed.

Primary Prevention and Delay of Onset of AD/Dementia

Prevention in Alzheimer's disease and other dementias (AD/dementia) is defined on the basis of clinical states and their expressed symptoms. Primary prevention refers to delaying the development of the full-blown state of clinically expressed disease in normal individuals. Current primary prevention research is driven by evidence of AD/dementia protective factors that have emerged from epidemiological studies. The first randomized controlled trials (RCTs) of primary AD/dementia prevention have been designed to test the efficacy and safety of NSAIDs, hormonal therapy, antihypertensive drugs and antioxidants. The experience of these trials has indicated safety concerns as a key issue and highlighted significant design challenges in this type of research. These trials have required large sample sizes and unsustainable costs. There should be consideration given in future trials to enriching study samples with risk factors to increase progression rates to AD/dementia. Innovative strategies will also be needed to recruit and retain subjects given the long follow-up periods, modest perceived benefit and the potential for the risk-benefit ratio to change during the trial. It is foreseeable that regulatory authorities will be presented with primary prevention RCTs for approval and labelling, and that criteria to evaluate such evidence still need to be developed.

Cholesterol balance in prion diseases and Alzheimer's disease

Prion diseases are transmissible and fatal neurodegenerative disorders of humans and animals. They are characterized by the accumulation of PrP^Sc, an aberrantly folded isoform of the cellular prion protein PrP^C, in the brains of affected individuals. PrP^C is a cell surface glycoprotein attached to the outer leaflet of the plasma membrane by a glycosyl-phosphatidyl-inositol (GPI) anchor. Specifically, it is associated with lipid rafts, membrane microdomains enriched in cholesterol and sphinoglipids. It has been established that inhibition of endogenous cholesterol synthesis disturbs lipid raft association of PrP^C and prevents PrP^Sc accumulation in neuronal cells. Additionally, prion conversion is reduced upon interference with cellular cholesterol uptake, endosomal export, or complexation at the plasma membrane. Altogether, these results demonstrate on the one hand the importance of cholesterol for prion propagation. On the other hand, growing evidence suggests that prion infection modulates neuronal cholesterol metabolism. Similar results were reported in Alzheimer’s disease (AD): whereas amyloid β peptide formation is influenced by cellular cholesterol, levels of cholesterol in the brains of affected individuals increase during the clinical course of the disease. In this review, we summarize commonalities of alterations in cholesterol homeostasis and discuss consequences for neuronal function and therapy of prion diseases and AD.