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Brusini I, MacNicol E, Kim E, Smedby Ö, Wang C, Westman E, Veronese M, Turkheimer F, Cash D. MRI-derived brain age as a biomarker of ageing in rats: validation using a healthy lifestyle intervention. Neurobiol Aging 2022; 109:204-215. [PMID: 34775211 DOI: 10.1016/j.neurobiolaging.2021.10.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 12/21/2022]
Abstract
The difference between brain age predicted from MRI and chronological age (the so-called BrainAGE) has been proposed as an ageing biomarker. We analyse its cross-species potential by testing it on rats undergoing an ageing modulation intervention. Our rat brain age prediction model combined Gaussian process regression with a classifier and achieved a mean absolute error (MAE) of 4.87 weeks using cross-validation on a longitudinal dataset of 31 normal ageing rats. It was then tested on two groups of 24 rats (MAE = 9.89 weeks, correlation coefficient = 0.86): controls vs. a group under long-term environmental enrichment and dietary restriction (EEDR). Using a linear mixed-effects model, BrainAGE was found to increase more slowly with chronological age in EEDR rats (p=0.015 for the interaction term). Cox regression showed that older BrainAGE at 5 months was associated with higher mortality risk (p=0.03). Our findings suggest that lifestyle-related prevention approaches may help to slow down brain ageing in rodents and the potential of BrainAGE as a predictor of age-related health outcomes.
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Affiliation(s)
- Irene Brusini
- Department of Biomedical Engineering and Health Systems,KTH Royal Institute of Technology, Stockholm, Sweden; Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden.
| | - Eilidh MacNicol
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Eugene Kim
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Örjan Smedby
- Department of Biomedical Engineering and Health Systems,KTH Royal Institute of Technology, Stockholm, Sweden
| | - Chunliang Wang
- Department of Biomedical Engineering and Health Systems,KTH Royal Institute of Technology, Stockholm, Sweden
| | - Eric Westman
- Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Stockholm, Sweden
| | - Mattia Veronese
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom; Department of Information Engineering, University of Padua, Padua, Italy
| | - Federico Turkheimer
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
| | - Diana Cash
- Department of Neuroimaging, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom
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Cole JH, Poudel RPK, Tsagkrasoulis D, Caan MWA, Steves C, Spector TD, Montana G. Predicting brain age with deep learning from raw imaging data results in a reliable and heritable biomarker. Neuroimage 2017; 163:115-124. [PMID: 28765056 DOI: 10.1016/j.neuroimage.2017.07.059] [Citation(s) in RCA: 403] [Impact Index Per Article: 57.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2017] [Revised: 07/20/2017] [Accepted: 07/28/2017] [Indexed: 01/02/2023] Open
Abstract
Machine learning analysis of neuroimaging data can accurately predict chronological age in healthy people. Deviations from healthy brain ageing have been associated with cognitive impairment and disease. Here we sought to further establish the credentials of 'brain-predicted age' as a biomarker of individual differences in the brain ageing process, using a predictive modelling approach based on deep learning, and specifically convolutional neural networks (CNN), and applied to both pre-processed and raw T1-weighted MRI data. Firstly, we aimed to demonstrate the accuracy of CNN brain-predicted age using a large dataset of healthy adults (N = 2001). Next, we sought to establish the heritability of brain-predicted age using a sample of monozygotic and dizygotic female twins (N = 62). Thirdly, we examined the test-retest and multi-centre reliability of brain-predicted age using two samples (within-scanner N = 20; between-scanner N = 11). CNN brain-predicted ages were generated and compared to a Gaussian Process Regression (GPR) approach, on all datasets. Input data were grey matter (GM) or white matter (WM) volumetric maps generated by Statistical Parametric Mapping (SPM) or raw data. CNN accurately predicted chronological age using GM (correlation between brain-predicted age and chronological age r = 0.96, mean absolute error [MAE] = 4.16 years) and raw (r = 0.94, MAE = 4.65 years) data. This was comparable to GPR brain-predicted age using GM data (r = 0.95, MAE = 4.66 years). Brain-predicted age was a heritable phenotype for all models and input data (h2 ≥ 0.5). Brain-predicted age showed high test-retest reliability (intraclass correlation coefficient [ICC] = 0.90-0.99). Multi-centre reliability was more variable within high ICCs for GM (0.83-0.96) and poor-moderate levels for WM and raw data (0.51-0.77). Brain-predicted age represents an accurate, highly reliable and genetically-influenced phenotype, that has potential to be used as a biomarker of brain ageing. Moreover, age predictions can be accurately generated on raw T1-MRI data, substantially reducing computation time for novel data, bringing the process closer to giving real-time information on brain health in clinical settings.
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Affiliation(s)
- James H Cole
- Computational, Cognitive & Clinical Neuroimaging Laboratory, Division of Brain Sciences, Imperial College London, London, UK
| | - Rudra P K Poudel
- Department of Biomedical Engineering, King's College London, London, UK
| | | | - Matthan W A Caan
- Department of Radiology, Academic Medical Center, Amsterdam, The Netherlands
| | - Claire Steves
- Department of Twin Research & Genetic Epidemiology, King's College London, London, UK
| | - Tim D Spector
- Department of Twin Research & Genetic Epidemiology, King's College London, London, UK
| | - Giovanni Montana
- Department of Biomedical Engineering, King's College London, London, UK; Department of Mathematics, Imperial College London, London, UK.
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Sureshkumar R, Bharath S, Jain S, Prakash O, Purushottam M, Thennarasu K, Mukherjee O, Sivakumar PT, Varghese M. ApoE4 and late onset depression in Indian population. J Affect Disord 2012; 136:244-8. [PMID: 22226379 DOI: 10.1016/j.jad.2011.12.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/12/2011] [Accepted: 12/12/2011] [Indexed: 11/30/2022]
Abstract
OBJECTIVE ApoE4 is a 'risk factor' for cognitive disorders like Alzheimer's dementia, and Late Onset Depression (LOD) is a forerunner of dementia. There is thus a need to study the association between ApoE4 allele and LOD. METHOD The study assessed the frequency of ApoE4 allele in 31 cases of LOD above the age of 50 years and 31 matched controls. The subjects were assessed on various clinical parameters towards diagnosis. RESULTS There was a significant association between the ApoE4 allele and LOD in comparison to controls (Odd's ratio=4.7, Confidence Interval=1.12 to 19.79, P=0.035). ApoE4 allele had no association with the age of onset of depression, cognitive functions and severity of LOD. CONCLUSION Individuals with LOD have a significantly higher frequency of the ApoE4 allele. In other words, elderly in India with an ApoE4 allele have 4.7 times more risk of developing depression in old age. Within LOD group there is no difference between those with and without ApoE4 accordingly in age of onset of depression, cognitive functions and severity of LOD.
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Affiliation(s)
- R Sureshkumar
- Geriatric Clinic & Services, Department of Psychiatry, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India.
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Sodero AO, Trovò L, Iannilli F, Van Veldhoven P, Dotti CG, Martin MG. Regulation of tyrosine kinase B activity by the Cyp46/cholesterol loss pathway in mature hippocampal neurons: relevance for neuronal survival under stress and in aging. J Neurochem 2011; 116:747-55. [DOI: 10.1111/j.1471-4159.2010.07079.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Iannilli F, Sodero AO, Ledesma MD, Dotti CG. Oxidative stress activates the pro-survival TrkA pathway through membrane cholesterol loss. Neurobiol Aging 2009; 32:1033-42. [PMID: 19679377 DOI: 10.1016/j.neurobiolaging.2009.07.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 06/03/2009] [Accepted: 07/10/2009] [Indexed: 10/20/2022]
Abstract
Neuronal activity is a highly demanding energetic process, resulting in the gradual accumulation of reactive oxygen species (ROS). Despite comparatively weak anti-oxidant defence systems, neurons outlive the pressure of ROS by activating most robust anti-stress mechanisms. We recently showed that one such mechanism is the activation of the TrkB receptor pathway, in turn determined by the loss of membrane cholesterol. It is not known however what causes the loss of membrane cholesterol. We here show that in differentiated PC12 cells induction of ROS is paralleled by a moderate loss of membrane cholesterol and the activation of the pro-survival TrkA receptor. Pharmacological reduction of cholesterol in non-stressed cells triggers TrkA activation while cholesterol replenishment inhibits receptor activation induced by stress. Moreover, addition of a ROS inhibitor prevented cholesterol loss and receptor activation under stress. These results highlight cholesterol loss as a compensatory protective mechanism against acute stress.
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Affiliation(s)
- Francesca Iannilli
- Department of Molecular and Developmental Genetics, VIB, Herestraat 49, 3000 Leuven, Belgium
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Cacabelos R. Pharmacogenetic basis for therapeutic optimization in Alzheimer's disease. Mol Diagn Ther 2008; 11:385-405. [PMID: 18078356 DOI: 10.1007/bf03256262] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Alzheimer's disease is a major health problem in developed countries. Approximately 10-15% of direct costs in dementia are attributed to pharmacological treatment, and only 10-20% of the patients are moderate responders to conventional antidementia drugs, with questionable cost effectiveness. The phenotypic expression of Alzheimer's disease is characterized by amyloid deposition in brain tissue and vessels (amyloid angiopathy), intracellular neurofibrillary tangle formation, synaptic and dendritic loss, and premature neuronal death. Primary pathogenic events underlying this neurodegenerative process include genetic factors involving more than 200 different genes distributed across the human genome, accompanied by progressive cerebrovascular dysfunction, and diverse environmental factors. Mutations in genes directly associated with the amyloid cascade (APP, PSEN1, PSEN2) are present in less than 5% of the Alzheimer's disease population; however, the presence of the epsilon4 allele of the apolipoprotein E gene (APOE) represents a major risk factor for more than 40% of patients with dementia. Genotype-phenotype correlation studies and functional genomics studies have revealed the association of specific mutations in primary loci and/or APOE-related polymorphic variants with the phenotypic expression of biological traits. It is estimated that genetics accounts for between 20% and 95% of the variability in drug disposition and pharmacodynamics. Recent studies indicate that the therapeutic response in Alzheimer's disease is genotype specific, depending on genes associated with Alzheimer's disease pathogenesis and/or genes responsible for drug metabolism (e.g. cytochrome P450 [CYP] genes). In monogenic studies, APOEepsilon4/epsilon4 genotype carriers are the worst responders to conventional treatments. Some cholinesterase inhibitors currently being use in the treatment of Alzheimer's disease are metabolized via CYP-related enzymes. These drugs can interact with many other drugs that are substrates, inhibitors or inducers of the CYP system, this interaction eliciting liver toxicity and other adverse drug reactions. CYP2D6 enzyme isoforms are involved in the metabolism of more than 20% of drugs used in CNS disorders. The distribution of the CYP2D6 genotypes in the European population of the Iberian peninsula differentiates four major categories of CYP2D6-related metabolizer types: (i) extensive metabolizers (EM) [51.61%]; (ii) intermediate metabolizers (IM) [32.26%]; (iii) poor metabolizers (PM) [9.03%]; and (iv) ultra-rapid metabolizers (UM) [7.10%]. PMs and UMs tend to show higher transaminase activity than EMs and IMs. EMs and IMs are the best responders, and PMs and UMs are the worst responders to pharmacologic treatments in Alzheimer's disease. At this early stage of the development of pharmacogenomic/pharmacogenetic procedures in Alzheimer's disease therapeutics, it seems very plausible that the pharmacogenetic response in Alzheimer's disease depends on the interaction of genes involved in drug metabolism and genes associated with Alzheimer's disease pathogenesis.
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Affiliation(s)
- Ramón Cacabelos
- EuroEspes Biomedical Research Center, Institute for CNS Disorders, Bergondo, Coruña, Spain.
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Abstract
Dementia is a major problem of health in developed countries. Alzheimer's disease (AD) is the main cause of dementia, accounting for 50-70% of the cases, followed by vascular dementia (30-40%) and mixed dementia (15-20%). Approximately 10-15% of direct costs in dementia are attributed to pharmacological treatment, and only 10-20% of the patients are moderate responders to conventional anti-dementia drugs, with questionable cost-effectiveness. Primary pathogenic events underlying the dementia process include genetic factors in which more than 200 different genes distributed across the human genome are involved, accompanied by progressive cerebrovascular dysfunction and diverse environmental factors. Mutations in genes directly associated with the amyloid cascade (APP, PS1, PS2) are only present in less than 5% of the AD population; however, the presence of the APOE-4 allele in the apolipoprotein E (APOE) gene represents a major risk factor for more than 40% of patients with dementia. Genotype-phenotype correlation studies and functional genomics studies have revealed the association of specific mutations in primary loci (APP, PS1, PS2) and/or APOE-related polymorphic variants with the phenotypic expression of biological traits. It is estimated that genetics accounts for 20-95% of variability in drug disposition and pharmacodynamics. Recent studies indicate that the therapeutic response in AD is genotype-specific depending upon genes associated with AD pathogenesis and/or genes responsible for drug metabolism (CYPs). In monogenic-related studies, APOE-4/4 carriers are the worst responders. In trigenic (APOE-PS1-PS2 clusters)-related studies the best responders are those patients carrying the 331222-, 341122-, 341222-, and 441112- genomic profiles. The worst responders in all genomic clusters are patients with the 441122+ genotype, indicating the powerful, deleterious effect of the APOE-4/4 genotype on therapeutics in networking activity with other AD-related genes. Cholinesterase inhibitors of current use in AD are metabolized via CYP-related enzymes. These drugs can interact with many other drugs which are substrates, inhibitors or inducers of the cytochrome P-450 system; this interaction elicits liver toxicity and other adverse drug reactions. CYP2D6-related enzymes are involved in the metabolism of more than 20% of CNS drugs. The distribution of the CYP2D6 genotypes differentiates four major categories of CYP2D6-related metabolyzer types: (a) Extensive Metabolizers (EM)(*1/*1, *1/*10)(51.61%); (b) Intermediate Metabolizers (IM) (*1/*3, *1/*4, *1/*5, *1/*6, *1/*7, *10/*10, *4/*10, *6/*10, *7/*10) (32.26%); (c) Poor Metabolizers (PM) (*4/*4, *5/*5) (9.03%); and (d) Ultra-rapid Metabolizers (UM) (*1xN/*1, *1xN/*4, Dupl) (7.10%). PMs and UMs tend to show higher transaminase activity than EMs and IMs. EMs and IMs are the best responders, and PMs and UMs are the worst responders to pharmacological treatments in AD. It seems very plausible that the pharmacogenetic response in AD depends upon the interaction of genes involved in drug metabolism and genes associated with AD pathogenesis. The establishment of clinical protocols for the practical application of pharmacogenetic strategies in AD will foster important advances in drug development, pharmacological optimization and cost-effectiveness of drugs, and personalized treatments in dementia.
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Affiliation(s)
- Ramón Cacabelos
- EuroEspes Biomedical Research Center, Institute for CNS Disorders, 15166-Bergondo, Coruña, Spain.
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Abstract
Pharmacological treatment in Alzheimer's disease (AD) accounts for 10-20% of direct costs, and fewer than 20% of AD patients are moderate responders to conventional drugs (donepezil, rivastigmine, galantamine, memantine), with doubtful cost-effectiveness. Both AD pathogenesis and drug metabolism are genetically regulated complex traits in which hundreds of genes cooperatively participate. Structural genomics studies demonstrated that more than 200 genes might be involved in AD pathogenesis regulating dysfunctional genetic networks leading to premature neuronal death. The AD population exhibits a higher genetic variation rate than the control population, with absolute and relative genetic variations of 40-60% and 0.85-1.89%, respectively. AD patients also differ in their genomic architecture from patients with other forms of dementia. Functional genomics studies in AD revealed that age of onset, brain atrophy, cerebrovascular hemodynamics, brain bioelectrical activity, cognitive decline, apoptosis, immune function, lipid metabolism dyshomeostasis, and amyloid deposition are associated with AD-related genes. Pioneering pharmacogenomics studies also demonstrated that the therapeutic response in AD is genotype-specific, with apolipoprotein E (APOE) 4/4 carriers the worst responders to conventional treatments. About 10-20% of Caucasians are carriers of defective cytochrome P450 (CYP) 2D6 polymorphic variants that alter the metabolism and effects of AD drugs and many psychotropic agents currently administered to patients with dementia. There is a moderate accumulation of AD-related genetic variants of risk in CYP2D6 poor metabolizers (PMs) and ultrarapid metabolizers (UMs), who are the worst responders to conventional drugs. The association of the APOE-4 allele with specific genetic variants of other genes (e.g., CYP2D6, angiotensin-converting enzyme [ACE]) negatively modulates the therapeutic response to multifactorial treatments affecting cognition, mood, and behavior. Pharmacogenetic and pharmacogenomic factors may account for 60-90% of drug variability in drug disposition and pharmacodynamics. The incorporation of pharmacogenetic/pharmacogenomic protocols to AD research and clinical practice can foster therapeutics optimization by helping to develop cost-effective pharmaceuticals and improving drug efficacy and safety.
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Affiliation(s)
- Ramón Cacabelos
- EuroEspes Biomedical Research Center, Institute for CNS Disorders, Bergondo, Coruña, Spain
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Shimada A, Keino H, Kawamura N, Chiba Y, Hosokawa M. Limbic structures are prone to age-related impairments in proteasome activity and neuronal ubiquitinated inclusions in SAMP10 mouse: a model of cerebral degeneration. Neuropathol Appl Neurobiol 2007; 34:33-51. [PMID: 17973906 DOI: 10.1111/j.1365-2990.2007.00878.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
AIMS Neurodegenerative diseases are characterized by ubiquitinated inclusions in selective brain regions. Here we investigated whether the dysfunction of the ubiquitin proteasome system might be involved in the pathogenesis and regional selectivity of neuronal ubiquitinated inclusions using the SAMP10 strain of mouse, an inbred model of age-related cerebral degeneration. METHODS By comparing SAMP10 mice at various ages with SAMR1 and C57BL mice as normal brain ageing controls, we studied morphological features and distribution of inclusions. We measured tissue proteasome activity in different brain regions of mice at various ages by fluorogenic substrate assays. We induced inclusions in cultured neurones by inhibiting the proteasome and analysed changes in the dendritic morphology. RESULTS Inclusions were formed in association with lipofuscin in neuronal perikarya and occurred most frequently in the limbic-related forebrain structures. There were sparse inclusion-bearing neurones in the non-limbic forebrain. In aged SAMR1 and C57BL, there were far fewer inclusions in the limbic-related forebrain than in aged SAMP10. The proteasome activity in the limbic-related forebrain decreased much more rapidly and remarkably upon ageing (26% activity was detected in 17-month-old compared with 3-month-old mice) in SAMP10 than in SAMR1. The proteasome activity in the non-limbic forebrain did not change significantly with advancing age in either SAMP10 or SAMR1. Proteasomal inhibition enhanced the formation of ubiquitinated inclusions in cultured neurones. Neurones bearing inclusions had shortened neurites. CONCLUSIONS We propose that the regional selectivity of proteasomal impairment is causally related to the selectivity of inclusion formation and associated dendritic degeneration in neurones of ageing SAMP10 mice.
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Affiliation(s)
- A Shimada
- Department of Pathology, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi, Japan.
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Kivipelto M, Solomon A. Cholesterol as a risk factor for Alzheimer's disease - epidemiological evidence. Acta Neurol Scand 2006; 185:50-7. [PMID: 16866911 DOI: 10.1111/j.1600-0404.2006.00685.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Although dementia is usually a late-life syndrome, it is now well known that pathological changes begin quite early in adulthood, outside the classical age borders of geriatric specialties. In order to design effective preventive strategies, adequate information can only be gathered by taking a life-long view of Alzheimer's disease (AD). Dementia risk is the result of exposure to both harmful and protective factors along the life course, and these factors, as well as their impact on the individual's health status, change over time. This review aims at presenting current epidemiological data on serum cholesterol levels and dietary fat intake as risk factors for dementia/AD, and at discussing the reasons and significance of contradictions between various studies. Reducing dementia risk may be possible by influencing the serum lipid profile. A more detailed characterization of the mechanisms behind the association of cholesterol (in both serum and brain) with dementia/AD, mechanisms about which little is currently known, would allow a better translation of research findings into clinical practice.
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Affiliation(s)
- M Kivipelto
- Department of Clinical Geriatrics, Karolinska Institutet, Stockholm, Sweden.
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Espeseth T, Greenwood PM, Reinvang I, Fjell AM, Walhovd KB, Westlye LT, Wehling E, Lundervold A, Rootwelt H, Parasuraman R. Interactive effects of APOE and CHRNA4 on attention and white matter volume in healthy middle-aged and older adults. COGNITIVE AFFECTIVE & BEHAVIORAL NEUROSCIENCE 2006; 6:31-43. [PMID: 16869227 DOI: 10.3758/cabn.6.1.31] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the present study, we investigated age-related changes in interactions between efficiency of neuronal repair mechanisms and efficiency of cholinergic neurotransmission in the context of attentional orienting. In addition, we explored white matter volume changes as possible neuronal underpinnings. A sample of 230 healthy middle-aged (53-64 years) and older (65-75 years) adults was genotyped for polymorphisms of APOE and CHRNA4, a nicotinic receptor subunit gene. Participants were administered a visuospatial attention task involving letter discrimination with location cues of varying validity. Genotype effects on white matter volume were also investigated in a subset of participants who received MRI scans. APOE interacted with CHRNA4, such that APOE-epsilon4 carriers who were also CHRNA4 TT homozygotes showed disproportionately slowed reaction time (RT) following invalid location cues. The interaction was stronger in the middle-aged participants than in the older participants. There was also a trend for individuals with combined APOE-epsilon4/CHRNA4 TT genotypes to show both lower white matter volume and slower overall RT on the attention task The interaction of a neurotransmission gene (CHRNA4) and a susceptibility gene (APOE) suggests that the efficiency of neuronal repair mechanisms may modulate the cholinergic system to influence attentional function.
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Liets LC, Eliasieh K, van der List DA, Chalupa LM. Dendrites of rod bipolar cells sprout in normal aging retina. Proc Natl Acad Sci U S A 2006; 103:12156-60. [PMID: 16880381 PMCID: PMC1524926 DOI: 10.1073/pnas.0605211103] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The aging nervous system is known to manifest a variety of degenerative and regressive events. Here we report the unexpected growth of dendrites in the retinas of normal old mice. The dendrites of many rod bipolar cells in aging mice were observed to extend well beyond their normal strata within the outer plexiform layer to innervate the outer nuclear layer where they appeared to form contacts with the spherules of rod photoreceptors. Such dendritic sprouting increased with age and was evident at all retinal eccentricities. These results provide evidence of retinal plasticity associated with normal aging.
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Affiliation(s)
| | | | | | - Leo M. Chalupa
- *Section of Neurobiology, Physiology, and Behavior and
- Department of Ophthalmology and Vision Science, School of Medicine, University of California, Davis, CA 95616
- To whom correspondence should be addressed at:
Section of Neurobiology, Physiology, and Behavior, University of California, One Shields Avenue, Davis, CA 95616. E-mail:
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Abstract
Ageing causes changes to the brain size, vasculature, and cognition. The brain shrinks with increasing age and there are changes at all levels from molecules to morphology. Incidence of stroke, white matter lesions, and dementia also rise with age, as does level of memory impairment and there are changes in levels of neurotransmitters and hormones. Protective factors that reduce cardiovascular risk, namely regular exercise, a healthy diet, and low to moderate alcohol intake, seem to aid the ageing brain as does increased cognitive effort in the form of education or occupational attainment. A healthy life both physically and mentally may be the best defence against the changes of an ageing brain. Additional measures to prevent cardiovascular disease may also be important.
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Affiliation(s)
- R Peters
- Care of the Elderly, Imperial College Faculty of Medicine, Hammersmith campus, Du Cane Road, London W12 0NN, UK.
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Cacabelos R. Pharmacogenomics, nutrigenomics and therapeutic optimization in Alzheimer’s disease. ACTA ACUST UNITED AC 2005. [DOI: 10.2217/1745509x.1.2.303] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The molecular neuropharmacology of Alzheimer’s disease (AD) is still at an early stage. During the past 20 years, only five drugs, four cholinesterase inhibitors (tacrine, donepezil, rivastigmine and galantamine) and one NMDA receptor partial antagonist (memantine), with poor cost-effectiveness, have been approved for the treatment of AD. Patients with dementia receive many different drugs daily to palliate cognitive and noncognitive symptoms, as well as for the treatment of concomitant disorders present in the elderly population. Polypharmacy, drug–drug interactions and adverse events may combine to deteriorate the frail condition of AD patients. In recent times, the partial elucidation of the pathogenic mechanisms underlying AD-related neurodegeneration, in which many different genes are involved, has helped to foster the development of novel drugs and pharmacogenomics studies. Functional genomics studies have revealed the association of specific mutations in primary loci (APP,PS1, PS2) and/or apolipoprotein (APO)-E-related polymorphic variants with the phenotypic expression of biological traits (e.g., age at onset, brain atrophy, cognitive decline rate, β-amyloid deposition, lipid metabolism dysfunction, immunologic dysregulation or therapeutic outcome). In most pharmacogenomics studies, patients harboring the APOE-4 allele (especially homozygotes) are the worst responders. Genetic clusters integrating 3–4 AD-related genes, representing 25–30% of the AD population, have allowed the identification of selective genotype clusters of good responders. Furthermore, approximately 15% of the European population with AD show mutant CYP2D6 alleles (poor and ultrarapid metabolizers) potentially responsible for efficacy and safety problems with cholinesterase inhibitors and psychotropic drugs. Nutritional factors may also contribute to the deterioration of cognition and brain function in dementia. Novel nutraceutical products obtained from marine sources with biotechnologic procedures have demonstrated atheroprotective properties and lipid-lowering effects and are devoid of hepatotoxic activity. Some of these nutraceuticals exhibit a genotype-dependent therapeutic effect, reflecting a nutrigenomic profile. Nutrigenetics/nutrigenomics- and pharmacogenetics/pharmacogenomics-associated factors may represent major determinants of drug efficacy and safety and therapeutics optimization in dementia and other CNS disorders.
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Affiliation(s)
- Ramón Cacabelos
- EuroEspes Biomedical Research Center, Institute for CNS Disorders, 15166-Bergondo, Coruña, Spain
- EuroEspes Chair of Biotechnology and Genomics, Camilo José Cela University, Madrid, Spain
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de Magalhães JP, Sandberg A. Cognitive aging as an extension of brain development: A model linking learning, brain plasticity, and neurodegeneration. Mech Ageing Dev 2005; 126:1026-33. [PMID: 15946728 DOI: 10.1016/j.mad.2005.04.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 04/27/2005] [Accepted: 04/27/2005] [Indexed: 01/24/2023]
Abstract
Differences in cognitive aging rates among mammals suggest that the pace of brain aging is genetically determined. In this work, we investigate the possibility that brain aging is an extension of brain development. It is possible that a subset of developmental mechanisms are extreme cases of antagonistic pleiotropy in that they are necessary for reaching adulthood and yet later cause age-related diseases. We derive a model linking development and brain aging in which childhood events essential for brain development later result in neurodegeneration. The hypothesis presented herein involves brain plasticity in which the same mechanisms that shape the adult phenotype continue at later ages contributing to cognitive dysfunction and eventually dementia. The same genetic program that decreases brain plasticity at early ages to focus our mind to the surrounding environment may continue in adulthood resulting in cognitive aging. Experimental implications for understanding neurodegeneration in this context are also discussed.
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Affiliation(s)
- João Pedro de Magalhães
- Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur, Room 238, Boston, MA 02115, USA.
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Wellnitz S, Friedlein A, Bonanni C, Anquez V, Goepfert F, Loetscher H, Adessi C, Czech C. A 13 kDa carboxy-terminal fragment of ApoE stabilizes Abeta hexamers. J Neurochem 2005; 94:1351-60. [PMID: 16011742 DOI: 10.1111/j.1471-4159.2005.03295.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The pathological role of ApoE4 in Alzheimer's disease (AD) is not fully elucidated yet but there is strong evidence that ApoE is involved in Abeta deposition, which is an early hallmark of AD neuropathology. Overexpression of ApoE in neuroblastoma cells (Neuro2a) leads to the generation of an intracellular 13 kDa carboxy-terminal fragment of ApoE comparable to fragments seen in brains of AD patients. ApoE4 generates more of this fragment than ApoE2 and E3 suggesting a potential pathological role of these fragments in Alzheimer's disease. Analysis of this intracellular ApoE4 fragment by protease digest followed by MALDI-TOF mass spectrometry showed the proteolytic cleavage site close to residue 187 of ApoE. We have engineered and expressed the corresponding ApoE fragments in vitro. The recombinant 13 kDa carboxy-terminal fragment inhibited fibril formation of Abeta; this contrasts with the full-length ApoE and the corresponding amino-terminal ApoE fragment. Moreover, we show that the 13 kDa carboxy-terminal fragment of ApoE stabilizes the formation of Abeta hexamers. Complexes of Abeta with the 13 kDa carboxy-terminal ApoE fragment show toxicity in PC12 cells comparable to Abeta fibrils. These data suggest that cleavage of ApoE, leading to the generation of this fragment, contributes to the pathogenic effect of ApoE4 in AD.
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Affiliation(s)
- Sabine Wellnitz
- F. Hoffmann-La Roche, CNS Research and Roche Center for Medical Genomics, 4070 Basel, Switzerland
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