Increased intermediate M1-M2 macrophage polarization and improved cognition in mild cognitive impairment patients on ω-3 supplementation.

Monocyte/macrophages of patients with mild cognitive impairment (MCI) and Alzheimer disease (AD) are defective in phagocytosis and degradation amyloid ß1-42 (Aß1-42), but are improved by ω-3 fatty acids (ω-3s). The hypothesis of this study was that active Aß1-42 phagocytosis by macrophages prevents brain amyloidosis and thus maintains cognition. We studied the effects of self-supplementation with a drink with ω-3s, antioxidants, and resveratrol on Mini-Mental State Examination (MMSE) scores, macrophage M1M2 phenotype [the ratio of inflammatory cluster of differentiation (CD)54+CD80 and proresolution markers CD163+CD206], and Aß1-42 phagocytosis in patients initially diagnosed as having MCI or subjective cognitive impairment (SCI). At baseline, the median MMSE score in patients in both the apolipoprotein E (ApoE) ε3/ε3 and ApoE ε3/ε4 groups was 26.0 and macrophage Aß1-42 phagocytosis was defective. The MMSE rate of change increased in the ApoE ε3/ε3 group a median 2.2 points per year (P = 0.015 compared to 0) but did not change in the ApoE ε3/ε4 group (P = 0.014 between groups). In the ApoE ε3/ε3 group, all patients remained cognitively stable or improved; in the ApoE ε3/ε4 group, 1 recovered from dementia, but 3 lapsed into dementia. The macrophage phenotype polarized in patients bearing ApoE ε3/ε3 to an intermediate (green zone) M1-M2 type at the rate of 0.226 U/yr, whereas in patients bearing ApoE ε3/ε4, polarization was negative (P = 0.08 between groups). The baseline M1M2 type in the extreme M1 (red zone) or M2 (white zone) was unfavorable for cognitive outcome. Aß1-42 phagocytosis increased in both ApoE groups (P = 0.03 in each groups). In vitro, the lipidic mediator resolvin D1 (RvD1) down regulated the M1 type in patients with ApoE ε3/ε3 but in some patients with ε3/ε4, paradoxically up-regulated the M1 type. Antioxidant/ω-3/resveratrol supplementation was associated with favorable immune and cognitive responses in ApoE ε3/ε3 and individual patients bearing ApoE ε3/ε4, and brings into personalized clinical practice the immune benefits expected from ω-3 mediators called resolvins. The validity of this study is limited by its small size and uncontrolled design.-Famenini, S., Rigali, E. A., Olivera-Perez, H. M., Dang, J., Chang, M T., Halder, R., Rao, R. V., Pellegrini, M., Porter, V., Bredesen, D., Fiala, M. Increased intermediate M1-M2 macrophage polarization and improved cognition in mild cognitive impairment patients on ω-3 supplementation.

Association of DNA methylation in the brain with age in older persons is confounded by common neuropathologies.

DNA methylation plays a crucial role in the regulation of gene expression, cell differentiation and development. Previous studies have reported age-related alterations of methylation levels in the human brain across the lifespan, but little is known about whether the observed association with age is confounded by common neuropathologies among older persons. Using genome-wide DNA methylation data from 740 postmortem brains, we interrogated 420,132 CpG sites across the genome in a cohort of individuals with ages from 66 to 108 years old, a range of ages at which many neuropathologic indices become quite common. We compared the association of DNA methylation prior to and following adjustment for common neuropathologies using a series of linear regression models. In the simplest model adjusting for technical factors including batch effect and bisulfite conversion rate, we found 8156 CpGs associated with age. The number of CpGs associated with age dropped by more than 10% following adjustment for sex. Notably, after adjusting for common neuropathologies, the total number of CpGs associated with age was reduced by approximately 40%, compared to the sex-adjusted model. These data illustrate that the association of methylation changes in the brain with age is inflated if one does not account for age-related brain pathologies. This article is part of a Directed Issue entitled: Epigenetics dynamics in development and disease.

How proteomic ApoE serotyping could impact Alzheimer's disease risk assessment: genetic testing by proteomics.

Humans have three major apolipoprotein E (ApoE) alleles (APOE; ε2, ε3 and ε4) that produce three ApoE protein isoforms. The ε2 allele encodes the ApoE2 isoform (Cys112, Cys158), whereas ε3 encodes the wild-type ApoE3 isoform (Cys112, Arg158) and ε4 encodes the ApoE4 isoform (Arg112, Arg158). Because the type of ApoE expressed is related to sporadic Alzheimer's disease risk and familial hyperlipidemia, many clinical studies have utilized ApoE typing in recent years. ApoE serotyping is based on the correlation between ApoE genotype and isoform; it is therefore possible to determine the genotype from the blood ApoE isoform combination. Serotyping ApoE using mass spectrometry promises highly accurate results while requiring minimal amounts of blood and reagents, resulting in lower costs, which suggest that proteomic-based ApoE serotyping may eventually become a routine clinical laboratory test. Not limited to ApoE, proteomic analysis of human samples could be used to intentionally determine - and perhaps unintentionally reveal - personal genetic information.

Sex modifies the APOE-related risk of developing Alzheimer disease.

OBJECTIVE: The APOE4 allele is the strongest genetic risk factor for sporadic Alzheimer disease (AD). Case-control studies suggest the APOE4 link to AD is stronger in women. We examined the APOE4-by-sex interaction in conversion risk (from healthy aging to mild cognitive impairment (MCI)/AD or from MCI to AD) and cerebrospinal fluid (CSF) biomarker levels. METHODS: Cox proportional hazards analysis was used to compute hazard ratios (HRs) for an APOE-by-sex interaction on conversion in controls (n = 5,496) and MCI patients (n = 2,588). The interaction was also tested in CSF biomarker levels of 980 subjects from the Alzheimer's Disease Neuroimaging Initiative. RESULTS: Among controls, male and female carriers were more likely to convert to MCI/AD, but the effect was stronger in women (HR = 1.81 for women; HR = 1.27 for men; interaction: p = 0.011). The interaction remained significant in a predefined subanalysis restricted to APOE3/3 and APOE3/4 genotypes. Among MCI patients, both male and female APOE4 carriers were more likely to convert to AD (HR = 2.16 for women; HR = 1.64 for men); the interaction was not significant (p = 0.14). In the subanalysis restricted to APOE3/3 and APOE3/4 genotypes, the interaction was significant (p = 0.02; HR = 2.17 for women; HR = 1.51 for men). The APOE4-by-sex interaction on biomarker levels was significant for MCI patients for total tau and the tau-to-Aß ratio (p = 0.009 and p = 0.02, respectively; more AD-like in women). INTERPRETATION: APOE4 confers greater AD risk in women. Biomarker results suggest that increased APOE-related risk in women may be associated with tau pathology. These findings have important clinical implications and suggest novel research approaches into AD pathogenesis.

Impact of the apolipoprotein E polymorphism, age and sex on neurogenesis in mice: pathophysiological relevance for Alzheimer's disease?

Apolipoprotein E (ApoE) is found in three different forms in humans (ApoE2, ApoE3 and ApoE4), and ApoE polymorphism is recognized as a major risk factor for Alzheimer's disease (AD). ApoE is involved in lipid and cholesterol transport, cell repair, and amyloid-ß deposition and certain studies suggest potential implications in neurogenesis. In this regard, we investigated the possible impact of the three different human ApoE isoforms on neurogenesis. We used ApoE knock-in mice of different ages and sex, and quantified newborn cells in the hippocampus by flow cytometry. Young adult ApoE4 mice (10-12 week-old) from both sexes displayed reduced neurogenesis compared with wild-types and the other genotypes. In addition, young adult ApoE2 female mice showed improved hippocampal progenitor cell proliferation. In older mice (1 year), hippocampal neurogenesis was globally decreased, particularly in females, and the difference between ApoE4 and the other genotypes observed in young animals disappeared for the two sexes, except for aged ApoE3 females. Indeed, a surprising protective effect of the ApoE3 genotype was observed in aged females. Our study highlights the role of ApoE in neurogenesis, and shows for the first time an early inequality between the ApoE genotypes. The reduced neurogenesis observed for the ApoE4 genotype and the improved results obtained in young ApoE2 females support the idea of a difference in the balance between neuronal birth and death modulated by the ApoE polymorphism in young animals. The maintenance of this balance and its modulation can influence pathophysiological mechanisms predisposing to neurodegenerative diseases like AD.

Cerebrovascular effects of apolipoprotein E: implications for Alzheimer disease.

Human apolipoprotein E (apoE) has 3 isoforms: apoE2, apoE3, and apoE4. APOE4 is a major genetic risk factor for Alzheimer disease and is associated with dementia in Down syndrome and poor neurological outcome after traumatic brain injury, cerebral hemorrhage, and other neuropathological disorders. While apoE4 can induce neuropathology by participating in various cellular and molecular pathways, herein I review data supporting the hypothesis that apoE4 has direct toxic effects on the cerebrovascular system that in turn can lead to secondary neuronal dysfunction and degeneration as well as accumulation of neurotoxins in brain such as ß-amyloid (Aß) in Alzheimer disease. I review Aß-independent cerebrovascular effects of apoE, particularly activation of a proinflammatory cyclophilin A-mediated pathway in brain vascular pericytes by apoE4 that has recently been shown to lead to a loss of cerebrovascular integrity and blood-brain barrier breakdown causing neuronal injury. I also review Aß-dependent cerebrovascular effects of apoE such as faulty Aß clearance from brain to circulation by apoE4. Finally, I discuss isoform-specific interactions of apoE with low-density lipoprotein receptor-related protein 1 on brain vascular cells (ie, endothelial cells, pericytes), which play an important role in Aß-independent and Aß-dependent effects of apoE on cerebral vasculature.

Apolipoprotein E gene (APOE) genotype in Wilson's disease: impact on clinical presentation.

BACKGROUND: Wilson's disease (WD), an inherited copper metabolism disorder that leads to pathological tissue copper accumulation and secondary organ damage, is caused by mutations in the ATP-ase 7B gene (ATP7B). The apolipoprotein E gene (APOE) alleles ε2, ε3, and ε4 produce three different apoE isoforms with different biological effects, which can determine risks of many human diseases, including neurodegenerative and liver disease. This study aimed to evaluate the impact of APOE genotype on the variability of WD phenotypic expression. METHODS: We analyzed data on 383 WD consecutive patients in the WD registry. The APOE genotypes (APOE ε3/ε3 (wild-type), APOE ε2-positive, and APOE ε4-positive) were determined and the APOE genotype effect on the phenotypic WD presentation was assessed in all symptomatic WD patients, as well as in patient subgroups divided according to sex and ATP7B genotype. RESULTS: APOE genotype had no impact on WD presentation in the general population of symptomatic patients. However, APOE ε4-positive women tended to present WD symptoms earlier than women possessing the wild-type APOE ε3/ε3 genotype (24.2 vs. 27.9 years; p = 0.08). The effect of the APOE ε4-positive genotype was more pronounced in ATP7B p.H1069Q homozygous women, in whom disease symptoms started almost 6 years earlier (23.6 vs. 29.9 years; p < 0.05) than in APOE ε3/ε3 women. CONCLUSIONS: In women, APOE ε4-positive genotype is associated with earlier onset of WD symptoms, particularly among ATP7B p.H1069Q homozygous patients. Further studies are needed to understand the mechanisms of these gender-dependent phenotypic effects.

Some evolutionary perspectives on Alzheimer's disease pathogenesis and pathology.

There is increasing urgency to develop effective prevention and treatment for Alzheimer's disease (AD) as the aging population swells. Yet, our understanding remains limited for the elemental pathophysiological mechanisms of AD dementia that may be causal, compensatory, or epiphenomenal. To this end, we consider AD and why it exists from the perspectives of natural selection, adaptation, genetic drift, and other evolutionary forces. We discuss the connection between the apolipoprotein E (APOE) allele and AD, with special consideration to APOE ɛ4 as the ancestral allele. The phylogeny of AD-like changes across species is also examined, and pathology and treatment implications of AD are discussed from the perspective of evolutionary medicine. In particular, amyloid-ß (Aß) neuritic plaques and paired helical filament tau (PHFtau) neurofibrillary tangles have been traditionally viewed as injurious pathologies to be targeted, but may be preservative or restorative processes that mitigate harmful neurodegenerative processes or may be epiphenoma of the essential processes that cause neurodegeneration. Thus, we raise fundamental questions about current strategies for AD prevention and therapeutics.

Isoform-specific proteolysis of apolipoprotein-E in the brain.

Apolipoprotein-E (apoE) plays important roles in neurobiology and the apoE4 isoform increases risk for Alzheimer's disease (AD). ApoE peptides are biologically active and may be produced in the brain. It is unclear if apoE proteolysis is dependent on isoform or AD status and this was addressed here. Hippocampus, frontal cortex, occipital lobe and cerebellum samples were homogenized into fractions that were soluble in Tris-buffered saline (TBS), Triton X-100 or guanidine hydrochloride and analysed for apoE fragmentation by Western blotting. Approximately 20% of apoE3 was detected as fragments and this was predominantly as a 25 kDa peptide in TBS-soluble fractions. The concentration of TBS-soluble apoE fragments was two- to three-fold higher in apoE3 compared to apoE4 subjects. This difference was observed in all areas of the brain examined and was not related to AD status. Cathepsin-D treatment generated apoE fragments that were very similar to those detected in brain, however, no apoE isoform-specific differences in susceptibility to cathepsin-D proteolysis were detected. This indicates that proteolytic processing of apoE to form soluble fragments in the human brain is dependent on apoE isoform but not AD status.

Neuropsychiatric symptoms and the APOE genotype in Alzheimer's disease.

The study aimed to characterize neuropsychiatric symptomatology in Alzheimer's disease (AD) and investigate the role of APOE genotype and other clinical variables in the onset of neuropsychiatric disorders. Moreover, an attempt to study the evolution of behavioral and psychiatric symptoms was made. Fifty-three consecutive outpatients with AD were enrolled. Twenty-four were followed longitudinally for 1 year. MMSE was used to evaluate cognitive functions. The neuropsychiatric inventory (NPI) was administered to assess behavioral and psychiatric symptoms. Genotyping was determined through laboratory testing. At baseline, no specific neuropsychiatric disorder was significantly associated with ApoE genotype, but associated with a peculiar neuropsychiatric profile. Patients with epsilon(4) allele showed a wider range of neuropsychiatric disturbances when compared to non-carriers and higher scores for hallucinations and aberrant motor behaviors. The longitudinal results suggest different trends in both groups: over time, epsilon(4) carriers showed an increase/delayed onset in some symptoms and a parallel decrease in others, while non-carriers presented an undifferentiated worsening of symptomatology. Clear relations with other clinical and demographic variables were also found. APOE epsilon(4) allele is associated to a peculiar neuropsychiatric profile characterizing the onset and evolution of Alzheimer's disease.

Human APOE isoform-dependent effects on brain beta-amyloid levels in PDAPP transgenic mice.

To investigate the role of human apolipoprotein E (apoE) on Abeta deposition in vivo, we crossed PDAPP mice lacking mouse Apoe to targeted replacement mice expressing human apoE (PDAPP/TRE2, PDAPP/TRE3, or PDAPP/TRE4). We then measured the levels of apoE protein and Abeta peptides in plasma, CSF, and brain homogenates in these mice at different ages. We also quantified the amount of brain Abeta and amyloid burden in 18-month-old mice. In young PDAPP/TRE4 mice that were analyzed at an age before brain Abeta deposition, we observed a significant decrease in the levels of apoE in CSF and brain when compared with age-matched mice expressing either human E2 or E3. The brain levels of Abeta42 in PDAPP/TRE4 mice were substantially elevated even at this very early time point. In older PDAPP/TRE4 mice, the levels of insoluble apoE protein increased in parallel to the dramatic rise in brain Abeta burden, and the majority of apoE was associated with Abeta. In TRE4 only mice, we also observed a significant decrease in the level of apoE in brain homogenates. Since the relative level of apoE mRNA was equivalent in PDAPP/TRE and TRE only mice, it appears that post-translational mechanisms influence the levels of apoE protein in brain (E4 < E3 << E2), resulting in early and dramatic apoE isoform-dependent effects on brain Abeta levels (E4 >> E3 > E2) that increase with age. Therapeutic strategies aimed at increasing the soluble levels of apoE protein, regardless of isoform, may effectively prevent and (or) treat Alzheimer's disease.

Genetic studies of A2M and BACE1 genes in Chinese Han Alzheimer's disease patients.

We investigated insertion (Ins)/deletion(Del) polymorphism in alpha-2-macroglobulin (A2M), G/C variant in the beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1) and apolipoprotein E (APOE) gene epsilon2/epsilon3/epsilon4 polymorphism in 387 Chinese Han ethnic patients with Alzheimer's disease and healthy study participants. After stratification for APOEepsilon4 status, only the BACE1-G allele with APOEepsilon4 was significantly associated with Alzheimer's disease. Through meta-analysis of the Del or G allele by pooling Asian studies, only BACE1-G allele appeared to increase risk of developing Alzheimer's disease. Through combination-analysis of the data about the A2M-I/D and the A2M-Ile1000Val variants, the A2M gene was suggested to be associated with Alzheimer's disease.

Update on risk factors for atherosclerosis: the role of inflammation and apolipoprotein E.

Over 1 million adults will have a new or recurrent myocardial infarction this year. Traditional risk factor assessment predicts less than one-half of all future cardiovascular events, and many patients develop atherosclerosis in the absence of these factors. Alternative risk factors, including genotype and the inflammatory response, are presented, along with intervention considerations for the medical-surgical nurse.

Interaction of herpesviridae, APOE gene, and education in cognitive impairment.

While high age, low level of education and APOE epsilon4 allele are known to predict dementia, there is recent data suggesting that certain viruses and subtypes of APOE epsilon3 could be involved, too. We investigated these relationships in a home-dwelling cohort of 357 elderly people with various cardiovascular diseases (DEBATE study). MMSE score below 24 was used to define cognitive impairment (n = 58). When adjusted for age and the presence of diabetes, multivariate analysis demonstrated maximally increased risk of cognitive impairment in association with a combination of three factors: seropositivity for herpesviridae, presence of APOE epsilon4, and low education (risk ratio 6.1, 95% CI 2.4-15.2). In the subcohort of APOE3/3 individuals (n = 216) homozygosity for the -219G epsilon3 haplotype showed a similar association (risk ratio 8.8, 95% CI 2.6-29.8). These results demonstrate an interaction of specific genetic (APOE) and environmental (education and herpesviridae) risk factors in the development of cognitive impairment and indicate that not only the epsilon4 allele of APOE but also the epsilon3 haplotype is a risk factor for dementia.

Neuropsychiatric associations of apolipoprotein E alleles in subjects with combat-related posttraumatic stress disorder.

Previous studies have reported associations between apolipoprotein E (APOE) genotype, cognitive function, and psychopathology in psychiatric populations. The authors investigated the associations between APOE allele status, memory function, and posttraumatic stress disorder (PTSD) symptom severity in PTSD subjects. Presence of the APOE 2 allele was associated with significantly worse reexperiencing symptoms and impaired memory function in this population.

ApoE genotype accounts for the vast majority of AD risk and AD pathology.

In this review, evidence is provided that apolipoprotein E (apoE) genotype accounts for the majority of Alzheimer's disease (AD) risk and pathology. The three major human isoforms, apoE2, apoE3, and apoE4, are encoded by different alleles (2, 3, 4) and regulate lipid metabolism and redistribution. ApoE isoforms differ in their effects on AD risk and pathology. Clinical and epidemiological data have indicated that the 4 allele may account for 50% of AD in the United States. Further, the rarity of AD among carriers of the 2 allele suggests that allelic variations in the gene encoding this protein may account for over 95% of AD cases. ApoE4 disrupts memory function in rodents. Further studies have indicated that fragments of apoE may contribute to both plaque and tangle formation. Thus, the epidemiologic and basic science evidence suggest that apoE genotype accounts for the vast majority of AD risk and pathology.

Apolipoprotein E -491 promoter polymorphism is an independent risk factor for Alzheimer's disease in the Chinese population.

Polymorphisms at positions -491, -427 and -219 in the promoter region of the Apolipoprotein E APOE gene have been variously reported to confer an increased risk of developing Alzheimer's disease (AD) independent of the effect of epsilon 2, 3 or 4 alleles in exon 4. In order to assess APOE promoter polymorphisms as independent risk factors in AD we have compared results in 183 definite or probable AD cases with 133 controls. We assayed markers at sites -491, -427, -219, and +113 in APOE gene and a polymorphic Hha1 site in the nearby APOC1 gene. We found that APOE promoter polymorphisms and APOC1 insertion alleles were significantly associated with AD. However, after stratification for epsilon 4 allele, only the A allele at -491 in APOE remained significantly associated with AD. The effects of the other markers depended almost entirely upon linkage disequilibrium with epsilon 4 allele, and only trends remained when cases and controls were stratified for the presence or absence of epsilon 4 allele. This occurred irrespective of whether markers were examined separately or together as haplotypes. So in the Chinese population only APOE -491 promoter alleles confer significant risk of AD independent of epsilon 4 status.

Accelerated memory decline in Alzheimer's disease with apolipoprotein epsilon4 allele.

To investigate a possible effect of the apolipoprotein (APOE) epsilon4 allele on memory decline in Alzheimer's disease (AD), we examined 64 AD patients with the APOE epsilon3/3, epsilon3/4, or epsilon4/4 allele using the Alzheimer Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and its subtests at the initial examination and at the 1-year follow-up visit. One-year changes in the scores of the Word Recall subtest, Word Recognition subtest, and total ADAS-Cog were significantly correlated with the number of APOE epsilon4 alleles after controlling for the effects of age, sex, education, test interval, and baseline scores. Findings revealed that APOE epsilon4 allele is related to an accelerated memory decline in AD.

The 129 codon polymorphism of the prion protein gene influences earlier cognitive performance in Down syndrome subjects.

Recently, a frequent prion protein gene (PRNP) polymorphism consisting of a methionine (M) for valine (V) substitution at codon 129 has been associated with cognitive impairment in elderly individuals. Down syndrome (DS) is associated with mental retardation and development of Alzheimer-like brain abnormalities. In the present study, we investigated the role of the PRNP polymorphism in 122 relatively young Italian DS patients. Allele frequencies of DS subjects did not differ from those in the general population. However, we found a significantly faster rate of decline in intellectual ability in the subgroup of DS patients carrying at least one V allele compared with the M/M DS subjects. An additive deleterious effect of apolipoprotein E epsilon 4 allele was detected after stratifying by APOE gene status. Our findings provide evidence that variability of the PRNP gene at codon 129 might contribute to accelerating the rate of earlier cognitive decline in DS subjects.