APOE and Alzheimer's disease: advances in genetics, pathophysiology, and therapeutic approaches.

The APOE ε4 allele remains the strongest genetic risk factor for sporadic Alzheimer's disease and the APOE ε2 allele the strongest genetic protective factor after multiple large scale genome-wide association studies and genome-wide association meta-analyses. However, no therapies directed at APOE are currently available. Although initial studies causally linked APOE with amyloid-ß peptide aggregation and clearance, over the past 5 years our understanding of APOE pathogenesis has expanded beyond amyloid-ß peptide-centric mechanisms to tau neurofibrillary degeneration, microglia and astrocyte responses, and blood-brain barrier disruption. Because all these pathological processes can potentially contribute to cognitive impairment, it is important to use this new knowledge to develop therapies directed at APOE. Several therapeutic approaches have been successful in mouse models expressing human APOE alleles, including increasing or reducing APOE levels, enhancing its lipidation, blocking the interactions between APOE and amyloid-ß peptide, and genetically switching APOE4 to APOE3 or APOE2 isoforms, but translation to human clinical trials has proven challenging.

Exposure to traffic-generated air pollution promotes alterations in the integrity of the brain microvasculature and inflammation in female ApoE-/- mice.

Traffic-generated air pollutants have been correlated with alterations in blood-brain barrier (BBB) integrity, which is associated with pathologies in the central nervous system (CNS). Much of the existing literature investigating the effects of air pollution in the CNS has predominately been reported in males, with little known regarding the effects in females. As such, this study characterized the effects of inhalation exposure to mixed vehicle emissions (MVE), as well as the presence of female sex hormones, in the CNS of female ApoE-/- mice, which included cohorts of both ovariectomized (ov-) and ovary-intact (ov+) mice. Ov + and ov- were placed on a high-fat diet and randomly grouped to be exposed to either filtered-air (FA) or MVE (200 PM/m3: 50 µg PM/m3 gasoline engine + 150 µg PM/m3 from diesel engine emissions) for 6 h/d, 7d/wk, for 30d. MVE-exposure resulted in altered cerebral microvascular integrity and permeability, as determined by the decreased immunofluorescent expression of tight junction (TJ) proteins, occludin, and claudin-5, and increased IgG extravasation into the cerebral parenchyma, compared to FA controls, regardless of ovary status. Associated with the altered cerebral microvascular integrity, we also observed an increase in matrix metalloproteinases (MMPs) -2/9 activity in the MVE ov+, MVE ov-, and FA ov- groups, compared to FA ov+. There was also elevated expression of intracellular adhesion molecule (ICAM)-1, inflammatory interleukins (IL-1, IL-1ß), and tumor necrosis factor (TNF-α) mRNA in the cerebrum of MVE ov + and MVE ov- animals. IκB kinase (IKK) subunits IKKα and IKKß mRNA expressions were upregulated in the cerebrum of MVE ov- and FA ov- mice. Our findings indicate that MVE exposure mediates altered integrity of the cerebral microvasculature correlated with increased MMP-2/9 activity and inflammatory signaling, regardless of female hormones present.

Status and future directions of clinical trials in Alzheimer's disease.

Amyloid-ß (Aß) senile plaques and neurofibrillary tangles of tau are generally recognized as the culprits of Alzheimer's disease (AD) and related dementia. About 25 years ago, the amyloid cascade hypotheses postulated a direct correlation of plaques with the development of AD, and it has been the dominant theory since then. In this period, more than 200 clinical trials focused mainly on targeting components of the Aß cascade have dramatically failed, some of them in Phase III. With a greater than 99.6% failure rate at a cost of several billion from governments, industry, and private funders, therapeutic strategies targeting amyloid and tau are now under scrutiny. Therefore, it is time to reevaluate alternatives to targeting Aß and tau as effective therapeutic strategies for AD. The diagnosis of AD is currently based on medical examination of symptoms including tests to assess memory impairment, attention, language, and other thinking skills. This is complemented with brain scans, such as computed tomography, magnetic resonance imaging, or positron emission tomography with the help of imaging probes targeting Aß or tau deposits. This approach has contributed to the tunnel vision focus on Aß and tau as the main culprits of AD. However, events upstream of these proteopathies (age-related impaired neuronal bioenergetics, lysosome function, neurotrophic signaling, and neuroinflammation, among others) are almost surely where the development of alternative therapeutic interventions should be targeted. Here, we present the current status of therapeutic candidates targeting diverse mechanisms and strategies including Aß and tau, proteins involved in Aß production and trafficking (ApoE, α/ß/γ-secretases), neuroinflammation, neurotransmitters, neuroprotective agents antimicrobials, and gene and stem cell therapy. There are currently around 33 compounds in Phase III, 78 in Phase II, and 32 more in Phase I trials. With the current world health crisis of increased dementia in a rapidly aging population, effective AD therapies are desperately needed.

Dual functional liposomes carrying antioxidants against tau hyperphosphorylation and apoptosis of neurons.

Quercetin (QU) and rosmarinic acid (RA) were loaded in phosphatidic acid-liposomes (QU/RA-PA-liposomes) with surface apolipoprotein E (ApoE) using a process of thin-film hydration, followed by covalent crosslinking to activate biological pathways for penetrating the blood-brain barrier (BBB) and redeeming the neuronal apoptosis from attack of ß-amyloid 1-42 (Aß1-42) and neurofibrillary tangles. The conjugation of liposomes with PA improved the activity of QU and RA against neurotoxicity of Aß1-42. The fluorescent images of brain capillaries revealed that surface modification with ApoE improved the permeation ability of QU/RA-PA-ApoE-liposomes across the BBB. In addition, the highest therapeutic efficacy was obtained in the case of QU/RA-PA-ApoE-liposomes, compared to other QU/RA formulations studied using in vivo Aß1-42-insulted rats mimicking Alzheimer's disease (AD). The cellular and molecular evidence from AD rats included the decrease in Aß1-42 plaque formation and interleukin-6 secretion, increase in the neuronal count in Nissl staining, and reduction in the expression of phosphorylated extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, p38 kinase and tau protein at serine 202 as well as caspase-3. The use of PA-ApoE-liposomes as a dual targeting formulation enhances the QU and RA ability to infiltrate the BBB, docks Aß1-42 plaques and can be a potent approach to rescue degenerated neurons from AD.

Long-term exposure to ambient air pollution, APOE-ε4 status, and cognitive decline in a cohort of older adults in northern Manhattan.

BACKGROUND: There is mounting evidence that long-term exposure to air pollution is related to accelerated cognitive decline in aging populations. Factors that influence individual susceptibility remain largely unknown, but may involve the apolipoprotein E genotype E4 (APOE-ε4) allele. OBJECTIVES: We assessed whether the association between long-term exposure to ambient air pollution and cognitive decline differed by APOE-ε4 status and cognitive risk factors. METHODS: The Washington Heights Inwood Community Aging Project (WHICAP) is a prospective study of aging and dementia. Neuropsychological testing and medical examinations occur every 18-24 months. We used mixed-effects models to evaluate whether the association between markers of ambient air pollution (nitrogen dioxide [NO2]), fine [PM2.5], and coarse [PM10] particulate matter) and the rate of decline in global and domain-specific cognition differed across strata defined by APOE-ε4 genotypes and cognitive risk factors, adjusting for sociodemographic factors and temporal trends. RESULTS: Among 4821 participants with an average of 6 years follow-up, higher concentrations of ambient air pollution were associated with more rapid cognitive decline. This association was more pronounced among APOE-ε4 carriers (p < 0.001). A one interquartile range increase in NO2 was associated with an additional decline of 0.09 standard deviations (SD) (95%CI -0.1, -0.06) in global cognition across biennial visits among APOE-ε4 positive individuals and a 0.07 SD (95%CI -0.09, -0.05) decline among APOE-ε4 negative individuals. Results for PM2.5, PM10 and cognitive domains were similar. The association between air pollutants and rate of cognitive decline also varied across strata of race-ethnicity with the association strongest among White non-Hispanic participants. CONCLUSIONS: These results add to the body of evidence on the adverse impact of ambient air pollution on cognitive aging and brain health and provide new insights into the genetic and behavioral factors that may impact individual susceptibility.

Gut Colonization with Methanogenic Archaea Lowers Plasma Trimethylamine N-oxide Concentrations in Apolipoprotein e-/- Mice.

A mechanistic link between trimethylamine N-oxide (TMAO) and atherogenesis has been reported. TMAO is generated enzymatically in the liver by the oxidation of trimethylamine (TMA), which is produced from dietary choline, carnitine and betaine by gut bacteria. It is known that certain members of methanogenic archaea (MA) could use methylated amines such as trimethylamine as growth substrates in culture. Therefore, we investigated the efficacy of gut colonization with MA on lowering plasma TMAO concentrations. Initially, we screened for the colonization potential and TMAO lowering efficacy of five MA species in C57BL/6 mice fed with high choline/TMA supplemented diet, and found out that all five species could colonize and lover plasma TMAO levels, although with different efficacies. The top performing MA, Methanobrevibacter smithii, Methanosarcina mazei, and Methanomicrococcus blatticola, were transplanted into Apoe-/- mice fed with high choline/TMA supplemented diet. Similar to C57BL/6 mice, following initial provision of the MA, there was progressive attrition of MA within fecal microbial communities post-transplantation during the initial 3 weeks of the study. In general, plasma TMAO concentrations decreased significantly in proportion to the level of MA colonization. In a subsequent experiment, use of antibiotics and repeated transplantation of Apoe-/- mice with M. smithii, led to high engraftment levels during the 9 weeks of the study, resulting in a sustained and significantly lower average plasma TMAO concentrations (18.2 ± 19.6 µM) compared to that in mock-transplanted control mice (120.8 ± 13.0 µM, p < 0.001). Compared to control Apoe-/- mice, M. smithii-colonized mice also had a 44% decrease in aortic plaque area (8,570 µm [95% CI 19587-151821] vs. 15,369 µm [95% CI [70058-237321], p = 0.34), and 52% reduction in the fat content in the atherosclerotic plaques (14,283 µm [95% CI 4,957-23,608] vs. 29,870 µm [95% CI 18,074-41,666], p = 0.10), although these differences did not reach significance. Gut colonization with M. smithii leads to a significant reduction in plasma TMAO levels, with a tendency for attenuation of atherosclerosis burden in Apoe-/- mice. The anti-atherogenic potential of MA should be further tested in adequately powered experiments.

Apolipoprotein E, Receptors, and Modulation of Alzheimer's Disease.

Apolipoprotein E (apoE) is a lipid carrier in both the peripheral and the central nervous systems. Lipid-loaded apoE lipoprotein particles bind to several cell surface receptors to support membrane homeostasis and injury repair in the brain. Considering prevalence and relative risk magnitude, the ε4 allele of the APOE gene is the strongest genetic risk factor for late-onset Alzheimer's disease (AD). ApoE4 contributes to AD pathogenesis by modulating multiple pathways, including but not limited to the metabolism, aggregation, and toxicity of amyloid-ß peptide, tauopathy, synaptic plasticity, lipid transport, glucose metabolism, mitochondrial function, vascular integrity, and neuroinflammation. Emerging knowledge on apoE-related pathways in the pathophysiology of AD presents new opportunities for AD therapy. We describe the biochemical and biological features of apoE and apoE receptors in the central nervous system. We also discuss the evidence and mechanisms addressing differential effects of apoE isoforms and the role of apoE receptors in AD pathogenesis, with a particular emphasis on the clinical and preclinical studies related to amyloid-ß pathology. Finally, we summarize the current strategies of AD therapy targeting apoE, and postulate that effective strategies require an apoE isoform-specific approach.

Apolipoprotein E as a novel therapeutic neuroprotection target after traumatic spinal cord injury.

Apolipoprotein E (apoE), a plasma lipoprotein well known for its important role in lipid and cholesterol metabolism, has also been implicated in many neurological diseases. In this study, we examined the effect of apoE on the pathophysiology of traumatic spinal cord injury (SCI). ApoE-deficient mutant (apoE-/-) and wild-type mice received a T9 moderate contusion SCI and were evaluated using histological and behavioral analyses after injury. At 3days after injury, the permeability of spinal cord-blood-barrier, measured by extravasation of Evans blue dye, was significantly increased in apoE-/- mice compared to wild type. The inflammation and spared white matter was also significantly increased and decreased, respectively, in apoE-/- mice compared to the wild type ones. The apoptosis of both neurons and oligodendrocytes was also significantly increased in apoE-/- mice. At 42days after injury, the inflammation was still robust in the injured spinal cord in apoE-/- but not wild type mice. CD45+ leukocytes from peripheral blood persisted in the injured spinal cord of apoE-/- mice. The spared white matter was significantly decreased in apoE-/- mice compared to wild type ones. Locomotor function was significantly decreased in apoE-/- mice compared to wild type ones from week 1 to week 8 after contusion. Treatment of exogenous apoE mimetic peptides partially restored the permeability of spinal cord-blood-barrier in apoE-/- mice after SCI. Importantly, the exogenous apoE peptides decreased inflammation, increased spared white matter and promoted locomotor recovery in apoE-/- mice after SCI. Our results indicate that endogenous apoE plays important roles in maintaining the spinal cord-blood-barrier and decreasing inflammation and spinal cord tissue loss after SCI, suggesting its important neuroprotective function after SCI. Our results further suggest that exogenous apoE mimetic peptides could be a novel and promising neuroprotective reagent for SCI.

Silencing of Anticoagulant Protein C Evokes Low-Incident but Spontaneous Atherothrombosis in Apolipoprotein E-Deficient Mice-Brief Report.

OBJECTIVE: Murine atherosclerosis models do not spontaneously develop atherothrombotic complications. We investigated whether disruption of natural anticoagulation allows preexisting atherosclerotic plaques to progress toward an atherothrombotic phenotype. APPROACH AND RESULTS: On lowering of plasma protein C levels with small interfering RNA (siProc) in 8-week Western-type diet-fed atherosclerotic apolipoprotein E-deficient mice, 1 out of 4 mice displayed a large, organized, and fibrin- and leukocyte-rich thrombus on top of an advanced atherosclerotic plaque located in the aortic root. Although again at low incidence (3 in 25), comparable thrombi at the same location were observed during a second independent experiment in 9-week Western-type diet-fed apolipoprotein E-deficient mice. Mice with thrombi on their atherosclerotic plaques did not show other abnormalities and had equally lowered plasma protein C levels as siProc-treated apolipoprotein E-deficient mice without thrombi. Fibrinogen and thrombin-antithrombin concentrations and blood platelet numbers were also comparable, and plaques in siProc mice with thrombi had a similar composition and size as plaques in siProc mice without thrombi. Seven out of 25 siProc mice featured clots in the left atrium of the heart. CONCLUSIONS: Our findings indicate that small interfering RNA-mediated silencing of protein C in apolipoprotein E-deficient mice creates a condition that allows the occurrence of spontaneous atherothrombosis, albeit at a low incidence. Lowering natural anticoagulation in atherosclerosis models may help to discover factors that increase atherothrombotic complications.

Association of Apolipoprotein E Polymorphism with Intravitreal Ranibizumab Treatment Outcomes in Age-Related Macular Degeneration.

PURPOSE: Genetic factors are known to influence the response to anti-vascular endothelial growth factor (VEGF) treatment in exudative age-related macular degeneration (AMD). The current study was conducted to investigate the association of Apolipoprotein E (ApoE) polymorphism with the treatment response to ranibizumab for exudative AMD. METHODS: One hundred nine eyes (109 patients, 59.6% male, mean age 63.84 ± 7.22 years) treated with intravitreal ranibizumab injections were included in the analysis. Smoking status and lesion type were recorded. Patients were categorized into three groups according to visual acuity (VA) change at 6 months after the first injection: VA loss >5 Early Treatment Diabetic Retinopathy Study (ETDRS) letters (Group 1); VA change between five ETDRS letters gain and loss (Group 2); VA improvement >5 ETDRS letters (Group 3). The association of ApoE gene polymorphisms with the three groups was evaluated. RESULTS: Both smoking status and lesion type showed no significant association with VA change (p = 0.12 and p = 0.64, respectively). A lower frequency of ɛ2 and a higher frequency of ɛ4 were observed in Group 3 (2.9 and 25.7%, respectively). VA improvement with more than five ETDRS letters was significantly associated with the presence of the ɛ4 genotype (p = 0.01). CONCLUSIONS: This study demonstrated that carriers of the ApoE ɛ4 polymorphism genotype show demonstrable improvement in VA after treatment with ranibizumab in exudative AMD. ApoE polymorphism identification may be used as a genetic screening to tailor individualized therapeutic approach for optimal treatment in neovascular AMD.

[Rapid determination of 28 pesticides and tetramine in whole blood by online gel permeation chromatography coupled with gas chromatography-mass spectrometry].

OBJECTIVE: To study the influences of carbon disulfide (CS2) exposureon fatty acid metabolism in apolipoprotein E (ApoE) knockout mice and C57BL/6J mice. METHODS: Twenty-four male ApoE knockout mice were randomly and equally divided into four groups: a CS2-exposed normal diet group, a CS2-unexposed normal diet group, a CS2-exposed high-fat diet group, and a CS2-unexposed high-fat diet group. Twenty-four C57BL/6J male mice were divided into four groups in the same way. The CS2-exposed groups were exposed to CS2 (1 g/m³) by static inhalation for 5 hours a day, 5 days a week. After two weeks, the whole blood of mice was collected. Methyl ester derivatization of fatty acids was performed using an acid-catalyzed method. Fatty acid contents before and after exposure were compared by gas chromatography-mass spectroscopy. RESULTS: There were significant differences in fatty acid contents of mice between the four groups. For the C57BL/6J mice, the arachidic acid contents in the CS2-exposed high-fat diet group were significantly lower than those in the CS2-unexposed high-fat diet group (P = 0.0450). For the ApoE knockout mice, the arachidonic acid contents in the CS2-exposed normal diet group were significantly lower than those in the CS2-unexposed control diet group (P = 0.0452). For the ApoE knockout mice, the γ-linolenic acid contents in the CS2-exposed high-fat diet group were significantly higher than those in the unexposed high-fat diet group (P = 0.0447). CONCLUSION: Exposure to CS2 can induce fatty acid metabolism disorder in mice, indicating that CS2 may increase the risk of atherosclerosis and other cardiovascular diseases.

Strong improvement of apolipoprotein E/low-density lipoprotein receptor signals by telmisartan in poststroke spontaneously hypertensive stroke resistant.

BACKGROUND: Telmisartan, an angiotensin receptor blocker also called metabosartan, is a promising solution for preventing cognitive decline or the incidence of dementia. METHODS: We examined the effects of telmisartan on cholesterol transport-related proteins (apolipoprotein E [ApoE]/low-density lipoprotein receptor [LDL-R]) and microtubule-associated protein 2 (MAP2) in the brain of spontaneously hypertensive stroke resistant (SHR-SR). SHR-SR received transient middle cerebral artery occlusion (tMCAO) for 90 minutes at 12 weeks of age and then was divided into 3 experiment groups including a vehicle, low-dose telmisartan (.3 mg/kg/day), and high-dose telmisartan (3 mg/kg/day). RESULTS: The low dose served to improve the metabolic syndrome of SHR-SR without lowering the blood pressure (BP) whereas the high dose was used to improve metabolic syndrome while lowering BP. Immunohistologic analysis showed that ApoE expression of cortical neurons was strong in the vehicle group at 6, 12, and 18 months of age, and that this ApoE expression pattern was very similar between the ipsilateral and contralateral sides of cerebral ischemia. On the other hand, LDL-R expression of cortical neurons was transiently increased at 6 months of age only on the ipsilateral side. Telmisartan dramatically suppressed the expression of ApoE/LDL-R at both doses. There was no remarkable difference in neuronal MAP2 staining between the 3 groups. CONCLUSIONS: These findings suggest that both low and high doses of telmisartan prevented the activation of ApoE/LDL-R in SHR-SR after tMCAO, and that the antimetabolic effect was regarded as the most important mechanism with few additional benefits by lowering BP in this transient stroke model.

Strong reduction of low-density lipoprotein receptor/apolipoprotein E expressions by telmisartan in cerebral cortex and hippocampus of stroke resistant spontaneously hypertensive rats.

BACKGROUND: Telmisartan is a unique angiotensin II type 1 receptor blocker with a partial peroxisome proliferator-activated receptor-γ (PPARγ) agonistic property to exert not only antihypertensive effect but also antimetabolic syndrome effect. METHODS: We examined the long-term effect of telmisartan on cholesterol transport-related proteins (low-density lipoprotein receptor [LDL-R]/apolipoprotein E [ApoE]) and microtubule-associated proteins 2 (MAP2) in the brains of stroke resistant spontaneously hypertensive rats (SHR-SRs), which were divided into 3 experiment groups including vehicle group (SHR/Ve), low-dose telmisartan group (SHR/Low, .3 mg/kg/day), and high-dose telmisartan group (SHR/High, 3 mg/kg/day). RESULTS: The numbers of LDL-R- and immuno-ApoE-positive neurons increased in both cerebral cortex and hippocampus of SHR/Ve throughout 6, 12, and 18 months of age, compared with age-matched normotensive Wistar rats. On the other hand, telmisartan significantly reduced the numbers of LDL-R- and ApoE immuno-positive neurons in both cerebral cortex and hippocampus, with similar effectiveness in the SHR/Low group without blood pressure (BP) lowering to BP lowering (SHR/High). The decrease of MAP2-positive neuron in SHR/Ve was recovered by telmisartan in both cerebral cortex and hippocampus. CONCLUSIONS: These findings suggest that a long-term treatment with telmisartan directly improved neuronal lipid metabolism in the cerebral cortex and hippocampus of SHR-SR, mainly improving LDL-R and ApoE metabolism (SHR/Low) with a small additive benefit by BP lowering (SHR/High), which could provide a preventative approach in patients with hypertension at risk of Alzheimer disease.

Apolipoprotein E in Alzheimer's disease: an update.

The vast majority of Alzheimer's disease (AD) cases are late onset (LOAD), which is genetically complex with heritability estimates up to 80%. Apolipoprotein E (APOE) has been irrefutably recognized as the major genetic risk factor, with semidominant inheritance, for LOAD. Although the mechanisms that underlie the pathogenic nature of APOE in AD are still not completely understood, emerging data suggest that APOE contributes to AD pathogenesis through both amyloid-ß (Aß)-dependent and Aß-independent pathways. Given the central role for APOE in the modulation of AD pathogenesis, many therapeutic strategies have emerged, including converting APOE conformation, regulating APOE expression, mimicking APOE peptides, blocking the APOE/Aß interaction, modulating APOE lipidation state, and gene therapy. Accumulating evidence also suggests the utility of APOE genotyping in AD diagnosis, risk assessment, prevention, and treatment response.

Suppressive effects of cacao polyphenols on the development of atherosclerosis in apolipoprotein E-deficient mice.

Previous studies in humans have shown that the cacao polyphenols, (-)-epicatechin and its oligomers, prevent in vitro and ex vivo low-density lipoprotein oxidation mediated by free radical generators and metal ions and also reduce plasma LDL-cholesterol levels. The aim of this study was to examine the effects of cacao polyphenols on the development of atherosclerosis in apolipoprotein E-deficient (-/-) mice. Mice aged 8 weeks (n = 90) were randomized into three groups, and fed either normal mouse chow (controls) or chow supplemented with 0.25 or 0.40 % cacao polyphenols for 16 weeks. The mean plaque area in cross-sections of the brachiocephalic trunk was measured and found to be lower in the 0.25 % cacao polyphenol group than in the control group (p < 0.05). Pathological observations showed that accumulation of cholesterol crystals in the plaque area was greater in the control group compared with the 0.40 % cacao polyphenol group (p < 0.05). Immunochemical staining in the 0.25 and 0.40 % groups showed that expression of the cell adhesion molecules (VCAM-1 and ICAM-1) and production of oxidative stress markers (4-hydroxynonenal, hexanoyl-lysine, and dityrosine) were reduced in cross-sections of the brachiocephalic trunk. These results suggest that cacao polyphenols inhibit the development of atherosclerosis in apolipoprotein E-deficient (-/-) mice by reducing oxidative stress and inflammatory responses.

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.

Betaine supplementation attenuates atherosclerotic lesion in apolipoprotein E-deficient mice.

BACKGROUND: Betaine serves as a methyl donor in a reaction converting homocysteine to methionine. It is commonly used for the treatment of hyperhomocysteinemia in humans, which indicates it may be associated with reduced risk of atherosclerosis. However, there have been few data regarding its vascular effect. AIM OF THE STUDY: To investigate the effect of betaine supplementation on atherosclerotic lesion in apolipoprotein (apo) E-deficient mice. METHODS: Four groups of apoE-deficient mice were fed AIN-93G diets supplemented with 0, 1, 2, or 4 g betaine/100 g diet (no, 1, 2, and 4% betaine, respectively). Wild-type C57BL/6 J mice were fed AIN-93G diet (wild-type). Mice were sacrificed after 0, 7, or 14 weeks of the experimental diets. Atherosclerotic lesion area in the aortic sinus, levels of tumor necrosis factor (TNF)-alpha and monocyte chemoattractant protein (MCP)-1 in aorta and serum, serum lipids, and methylation status of TNF-alpha promoter in aorta were determined. RESULTS: Linear regression analysis showed that the higher dose of betaine was related to smaller atherosclerotic lesion area (beta = -11.834, P < 0.001). Compared with no-betaine mice after 14 weeks, mice receiving 1%, 2%, or 4% betaine had 10.8, 41, and 37% smaller lesion area, respectively. Betaine supplementation also reduced aortic expression of TNF-alpha in a dose-dependent way in four groups of apoE-deficient mice, and Pearson correlation revealed that atherosclerotic lesion area was positively associated with aortic TNF-alpha level (r = 0.777, P < 0.001). Although serum TNF-alpha levels were lower in betaine-supplemented mice than in no-betaine mice after fourteen weeks of treatment (P < 0.001), we did not observe a significant dosage effect (P = 0.11). However, methylation level of TNF-alpha promoter did not differ among groups at any time. In this study, apoE-deficient mice receiving betaine supplementation for 14 weeks had higher concentrations of serum total cholesterol (P < 0.01), LDL cholesterol (P < 0.05), and lower body weight (P < 0.05) than no-betaine mice. CONCLUSIONS: These data suggest that despite exacerbating hyperlipidemia in apoE-deficient mice, betaine may exert its anti-atherogenic effect by inhibiting aortic inflammatory response mediated by TNF-alpha.

Genetic testing for heart disease susceptibility: potential impact on motivation to quit smoking.

As genetic tests for common gene variants and multifactorial, lifestyle-related conditions become available, it will be increasingly important to determine the psychological and behavioral impact of this emerging class of genetic tests. Our aim was to examine the potential impact of genetic testing for heart disease susceptibility on psychological predictors of smoking cessation. Two hundred and sixty-one smokers were asked to imagine that they had undergone a test for heart disease risk. They were randomly assigned to a genetic test scenario (low- or high-risk result) or an oxidative test scenario (high-risk result). Smokers in the genetic test-high risk group reported greater intention to quit smoking than smokers in the oxidative test-high risk group (p = 0.009); 30% of this was mediated by their holding stronger beliefs that quitting would reduce their heart disease risk (outcome expectations) (p = 0.011). The effect of genetic test-high risk feedback on outcome expectations was greatest amongst smokers with no heart disease family history (p = 0.038). The results suggest that genetic testing for heart disease risk may enhance interventions designed to improve health via increasing smoking cessation rates. Whether the findings hold true in studies that use real rather than hypothetical genetic tests remains to be seen.

Chronic thrombin exposure results in an increase in apolipoprotein-E levels.

Studies have shown that individuals with both a history of traumatic brain injury and inheritance of apolipoprotein E-4 (ApoE4) allele are associated with a poor neurologic outcome and an increased risk for Alzheimer's disease. We assessed the hypothesis that thrombin released during brain injury causes an increase in apolipoprotein-E levels and such increase in the levels of apolipoprotein-E4 isoform may have amyloidogenic effects. Rats received either thrombin (100 nm, 0.25 microl/hr, 28 days) or vehicle via intracerebroventricular (i.c.v.) infusion. Thrombin treatment increased apolipoprotein-E levels in hippocampus as compared to vehicle treatment (P < 0.001). Infusion of human apolipoprotein-E4 (0.6 ng/hr, i.c.v., 56 days) into rats resulted in beta-amyloid deposition and increased the number of GFAP-positive astrocytes. ApoE4 infusion also resulted in significant spatial memory deficits. These findings suggest that thrombin released during brain injury may contribute to an increase in apolipoprotein-E levels. Such increase in Apolipoprotein-E4 isoform facilitates beta-amyloid deposition and cognitive deficits.