Apolipoprotein E isoform phenotyping methodology and population frequency with identification of apoE1 and apoE5 isoforms

Apolipoprotein E4 Effects a Distinct Transcriptomic Profile and Dendritic Arbor Characteristics in Hippocampal Neurons Cultured in vitro

The APOE gene is diversified by three alleles ε2, ε3, and ε4 encoding corresponding apolipoprotein (apo) E isoforms. Possession of the ε4 allele is signified by increased risks of age-related cognitive decline, Alzheimer's disease (AD), and the rate of AD dementia progression. ApoE is secreted by astrocytes as high-density lipoprotein-like particles and these are internalized by neurons upon binding to neuron-expressed apoE receptors. ApoE isoforms differentially engage neuronal plasticity through poorly understood mechanisms. We examined here the effects of native apoE lipoproteins produced by immortalized astrocytes homozygous for ε2, ε3, and ε4 alleles on the maturation and the transcriptomic profile of primary hippocampal neurons. Control neurons were grown in the presence of conditioned media from Apoe -/- astrocytes. ApoE2 and apoE3 significantly increase the dendritic arbor branching, the combined neurite length, and the total arbor surface of the hippocampal neurons, while apoE4 fails to produce similar effects and even significantly reduces the combined neurite length compared to the control. ApoE lipoproteins show no systemic effect on dendritic spine density, yet apoE2 and apoE3 increase the mature spines fraction, while apoE4 increases the immature spine fraction. This is associated with opposing effects of apoE2 or apoE3 and apoE4 on the expression of NR1 NMDA receptor subunit and PSD95. There are 1,062 genes differentially expressed across neurons cultured in the presence of apoE lipoproteins compared to the control. KEGG enrichment and gene ontology analyses show apoE2 and apoE3 commonly activate expression of genes involved in neurite branching, and synaptic signaling. In contrast, apoE4 cultured neurons show upregulation of genes related to the glycolipid metabolism, which are involved in dendritic spine turnover, and those which are usually silent in neurons and are related to cell cycle and DNA repair. In conclusion, our work reveals that lipoprotein particles comprised of various apoE isoforms differentially regulate various neuronal arbor characteristics through interaction with neuronal transcriptome. ApoE4 produces a functionally distinct transcriptomic profile, which is associated with attenuated neuronal development. Differential regulation of neuronal transcriptome by apoE isoforms is a newly identified biological mechanism, which has both implication in the development and aging of the CNS.

Genetic variation and intestinal cholesterol absorption in humans: A systematic review and a gene network analysis

Intestinal cholesterol absorption varies widely between individuals, which may translate into differences in responsiveness to cholesterol-lowering drugs or diets. Therefore, understanding the importance of genetic variation on cholesterol absorption rates and the complex intestinal cholesterol network is important. Based on a systematic review, genetic variants in seven genes (ABCG5, ABCG8, ABO, APOE, MTTP, NPC1L1, and LDLR) were identified that were associated with intestinal cholesterol absorption. No clear associations were found for variants in APOA4, APOB, CETP, CYP7A1, HMGCR, SCARB1, SLCO1B1, and SREBF1. The seven genes were used to construct an intestinal cholesterol absorption network. Finally, a network with fifteen additional genes (APOA1, APOA4, APOB, APOC2, APOC3, CETP, HSPG2, LCAT, LDLRAP1, LIPC, LRP1, OLR1, P4HB, SAR1B, and SDC1) was generated. The constructed network shows that cholesterol absorption is complex. Further studies are needed to validate and improve this network, which may ultimately lead to a better understanding of the wide inter-individual variability in intestinal cholesterol absorption and the development of personalized interventions.

NHE6 depletion corrects ApoE4-mediated synaptic impairments and reduces amyloid plaque load

Apolipoprotein E4 (ApoE4) is the most important and prevalent risk factor for late-onset Alzheimer’s disease (AD). The isoelectric point of ApoE4 matches the pH of the early endosome (EE), causing its delayed dissociation from ApoE receptors and hence impaired endolysosomal trafficking, disruption of synaptic homeostasis, and reduced amyloid clearance. We have shown that enhancing endosomal acidification by inhibiting the EE-specific sodium-hydrogen exchanger 6 (NHE6) restores vesicular trafficking and normalizes synaptic homeostasis. Remarkably and unexpectedly, loss of NHE6 (encoded by the gene Slc9a6) in mice effectively suppressed amyloid deposition even in the absence of ApoE4, suggesting that accelerated acidification of EEs caused by the absence of NHE6 occludes the effect of ApoE on amyloid plaque formation. NHE6 suppression or inhibition may thus be a universal, ApoE-independent approach to prevent amyloid buildup in the brain. These findings suggest a novel therapeutic approach for the prevention of AD by which partial NHE6 inhibition reverses the ApoE4-induced endolysosomal trafficking defect and reduces plaque load.

Absence of Apolipoprotein E is associated with exacerbation of prion pathology and promotes microglial neurodegenerative phenotype

Prion diseases or prionoses are a group of rapidly progressing and invariably fatal neurodegenerative diseases. The pathogenesis of prionoses is associated with self-replication and connectomal spread of PrP^Sc, a disease specific conformer of the prion protein. Microglia undergo activation early in the course of prion pathogenesis and exert opposing roles in PrP^Sc mediated neurodegeneration. While clearance of PrP^Sc and apoptotic neurons have disease-limiting effect, microglia-driven neuroinflammation bears deleterious consequences to neuronal networks. Apolipoprotein (apo) E is a lipid transporting protein with pleiotropic functions, which include controlling of the phagocytic and inflammatory characteristics of activated microglia in neurodegenerative diseases. Despite the significance of microglia in prion pathogenesis, the role of apoE in prionoses has not been established. We showed here that infection of wild type mice with 22L mouse adapted scrapie strain is associated with significant increase in the total brain apoE protein and mRNA levels and also with a conspicuous cell-type shift in the apoE expression. There is reduced expression of apoE in activated astrocytes and marked upregulation of apoE expression by activated microglia. We also showed apoE ablation exaggerates PrP^Sc mediated neurodegeneration. Apoe^−/− mice have shorter disease incubation period, increased load of spongiform lesion, pronounced neuronal loss, and exaggerated astro and microgliosis. Astrocytes of Apoe^−/− mice display salient upregulation of transcriptomic markers defining A1 neurotoxic astrocytes while microglia show upregulation of transcriptomic markers characteristic for microglial neurodegenerative phenotype. There is impaired clearance of PrP^Sc and dying neurons by microglia in Apoe^−/− mice along with increased level of proinflammatory cytokines. Our work indicates that apoE absence renders clearance of PrP^Sc and dying neurons by microglia inefficient, while the excess of neuronal debris promotes microglial neurodegenerative phenotype aggravating the vicious cycle of neuronal death and neuroinflammation.

Segmented Linear Mixed Model Analysis Reveals Association of the APOEɛ4 Allele with Faster Rate of Alzheimer's Disease Dementia Progression

Background:

APOEɛ4 allele carriers present with an increased risk for late-onset Alzheimer’s disease (AD), show cognitive symptoms at an earlier age, and are more likely to transition from mild cognitive impairment (MCI) to dementia but despite this, it remains unclear whether or not the ɛ4 allele controls the rate of disease progression.

Objective:

To determine the effects of the ɛ4 allele on rates of cognitive decline and brain atrophy during MCI and dementia stages of AD.

Methods:

A segmented linear mixed model was chosen for longitudinal modeling of cognitive and brain volumetric data of 73 ɛ3/ɛ3, 99 ɛ3/ɛ4, and 39 ɛ4/ɛ4 Alzheimer’s Disease Neuroimaging Initiative participants who transitioned during the study from MCI to AD dementia.

Results:

ɛ4 carriers showed faster decline on MMSE, ADAS-11, CDR-SB, and MoCA scales, with the last two measures showing significant ɛ4 allele-dose effects after dementia transition but not during MCI. The ɛ4 effect was more prevalent in younger participants and in females. ɛ4 carriers also demonstrated faster rates of atrophy of the whole brain, the hippocampus, the entorhinal cortex, the middle temporal gyrus, and expansion of the ventricles after transitioning to dementia but not during MCI.

Conclusion:

Possession of the ɛ4 allele is associated with a faster progression of dementia due to AD. Our observations support the notion that APOE genotype not only controls AD risk but also differentially regulates mechanisms of neurodegeneration underlying disease advancement. Furthermore, our findings carry significance for AD clinical trial design.

Distribution of APOE gene polymorphism in the Chinese Uyghur children & its association with urolithiasis

BACKGROUND & OBJECTIVES

This study was to survey the apolipoprotein E (APOE) gene polymorphism distribution among Chinese Uyghur children and to explore the relationship between APOE gene polymorphism and the occurrence of urolithiasis.

METHODS

A total of 144 Uyghur children with urolithiasis and 274 without the history of urolithiasis were enrolled in this study. Venous blood samples were collected from all participants, and APOE genotyping, derived from rs429358 and rs7412, was performed using Sanger sequencing.

RESULTS

Among the 418 children, the most prevalent genotype was E3/3, accounting for 71.3 per cent in the urolithiasis group and 71.4 per cent in the control group, followed by E3/4 and E2/3. Higher frequencies of the ɛ2 and ɛ4 alleles and lower frequencies of the ɛ3 allele were observed in the test group, and the unusual allele ɛ1 was also found in them. However, there were no significant differences between cases and controls at both rs429358 and rs7412 genotype and allele frequencies [odds ratio (OR)=0.98, 95% confidence interval (CI): 0.57-1.67; 0.98 (0.59-1.63); 1.43 (0.75-2.74) and 1.40 (0.74-2.62), respectively]. Likewise, none of significant differences was found between cases and controls at both APOE genotype and allele frequencies [OR=0.88, 95% CI: 0.51-1.53; 0.74 (0.33-1.64); 1.10 (0.73-1.66); 1.13 (0.76-1.67) and 1.14 (0.76-1.70), respectively].

INTERPRETATION & CONCLUSIONS

The present study does not support any association between APOE genotyping and urolithiasis in Uyghur children.

Anticholinergic/Sedative Drug Burden and Subjective Cognitive Decline in Older Adults at Risk of Alzheimer's Disease

BACKGROUND

Anticholinergic/sedative drug use, measured by the Drug Burden Index (DBI), has been linked to cognitive impairment in older adults. Subjective cognitive decline (SCD) may be among the first symptoms patients with Alzheimer's disease (AD) experience. We examined whether DBI values are associated with SCD in older adults at risk of AD. We hypothesized that increased DBI would be associated with greater SCD at older ages.

METHOD

Two-hundred-six community-dwelling, English-speaking adults (age = 65 ± 9 years) at risk of AD (42% apolipoprotein ε4 carriers; 78% with AD family history) were administered a single question to ascertain SCD: "Do you feel like your memory is becoming worse?" Response options were "No"; "Yes, but this does not worry me"; and "Yes, this worries me." DBI values were derived from self-reported medication regimens using older adult dosing recommendations. Adjusting for relevant covariates (comorbidities and polypharmacy), we examined independent effects of age and DBI on SCD, as well as the moderating effect of age on the DBI-SCD association at mean ± 1 SD of age.

RESULTS

Both SCD and anticholinergic/sedative drug burden were prevalent. Greater drug burden was predictive of SCD severity, but age alone was not. A significant DBI*Age interaction emerged with greater drug burden corresponding to more severe SCD among individuals age 65 and older.

CONCLUSION

Anticholinergic/sedative drug exposure was associated with greater SCD in adults 65 and older at risk for AD. Longitudinal research is needed to understand if this relationship is a pre-clinical marker of neurodegenerative disease and predictive of future cognitive decline.

Association Between Elevated Depressive Symptoms and Cognitive Function Moderated by APOE4 Status: Framingham Offspring Study

BACKGROUND

Depression and Apolipoprotein E4 (APOE4) are associated with decreased cognitive function and differences in brain structure.

OBJECTIVE

This study investigated whether APOE4 status moderates the association between elevated depressive symptoms, cognitive function, and brain structure.

METHODS

Stroke- and dementia-free participants (n = 1,968) underwent neuropsychological evaluation, brain MRI, and depression screening. Linear and logistic regression was used to examine all associations. Secondary analyses were performed using interaction terms to assess effect modification by APOE4 status.

RESULTS

Elevated depressive symptoms were associated with lower cognitive performance in several domains. In stratified analyses, elevated depressive symptoms were associated with poorer visual short- and long-term memory performance for APOE4 + participants. Elevated depressive symptoms were not associated with any brain structure in this study sample.

CONCLUSION

Elevated depressive symptoms impact cognitive function in non-demented individuals. Having the APOE4 allele may exacerbate the deleterious effects of elevated depressive symptoms on visual memory performance. Screening for elevated depressive symptoms in both research studies and clinical practice may be warranted to avoid false positive identification of neurodegeneration, particularly among those who are APOE4 + .

The Association of rs1898830 in Toll-Like Receptor 2 with Lipids and Blood Pressure

BACKGROUND AND OBJECTIVE

Toll-like receptors (TLRs) are important components of the innate immune system, involved in establishing immunity to infections. Apart from being implicated in immunity, numerous studies have reported that many TLRs, including TLR2, are involved in the pathogenesis of cardiovascular diseases and their risk factors. Since rs1898830 is associated with TLR2-mediated cellular activation, we aimed to study its association with CVD risk factors, such as lipid levels and hypertension.

METHODS

A cross-sectional study was conducted on 460 individuals free from chronic diseases. Clinical and biological data were collected and DNA was extracted and genotyped using Kompetitive allele specific PCR (KASP™). Multiple logistic regression models, adjusted for six covariates, were used. A power calculation analysis was also performed.

RESULTS

We found that rs1898830 in TLR2 was positively associated with hypertension (OR = 2.18, p = 0.03) and negatively associated with high-density lipoprotein cholesterol (OR = 0.66, p = 0.05). In contrast, no relation was found with total cholesterol and low-density lipoprotein cholesterol.

CONCLUSION

The present results provide additional evidence supporting the implication of TLR2 in CVD risk factors.

Interaction effect of alcohol consumption and Alzheimer disease polygenic risk score on the brain cortical thickness of cognitively normal subjects

Alcohol consumption and genetic risk for Alzheimer disease (AD) are among many factors known to be associated with brain structure in cognitively healthy adults. It is unclear, however, whether the effect of alcohol consumption on brain structure varies depending on a person's level of genetic risk for AD. We hypothesized that there is an interaction effect of alcohol consumption and a 33-SNP AD polygenic risk score (PRS) on the cortical thickness of brain regions known to be affected early in the course of AD. Studying 6,213 cognitively healthy subjects from the UK Biobank, we found a significant interaction effect of the 33-SNP AD PRS and alcohol consumption on this AD Cortical Thickness Signature. Stratified, among those who consume 12-24 g/day of alcohol, the 33-SNP AD PRS had a significant, positive association with AD Cortical Thickness Signature, with high-risk subjects having the greatest AD Cortical Thickness Signature. There were no significant associations of the 33-SNP AD PRS with AD Cortical Thickness Signature among the nondrinker or <1, 1-6, 6-12, 24-48, or >48 g/day groups. It is unclear whether this interaction is due to a detrimental or beneficial effect of moderate alcohol consumption in those with the highest genetic risk for AD.

Associations Between the Apolipoprotein E ε4 Allele and Reduced Serum Levels of High Density Lipoprotein a Cognitively Normal Aging Han Chinese Population

Background: Previous studies have confirmed that APOE genotype is associated with lipid metabolism, but related studies are inconsistent. Therefore, we conducted this cross-sectional study to explore the associations between apolipoprotein E (APOE) genotypes and serum levels of fasting blood sugar, triglycerides, total cholesterol, high density lipoprotein, and low density lipoprotein in a cognitively normal aging Han Chinese population. Methods: One hundred sixty-nine community elders with normal cognitive function were included in the study. Based on multiplex amplification refractory mutation system polymerase chain reaction (PCR), these subjects were divided into three groups: (1) E2/2 or E2/3 (APOE E2); (2) E3/3 (APOE E3); and (3) E2/4, E3/4, or E4/4 (APOE E4). Correlations of serum levels of fasting blood sugar, triglycerides, total cholesterol, high density lipoprotein, and low density lipoprotein with APOE genotypes were assessed. Results: The results of Mann-Whitney analysis showed that the concentration of high density lipoprotein (HDL) in APOE E2 and E3 groups was higher than that in E4 groups (p < 0.05). Logistic regression analysis also suggested that a lower level of high density lipoprotein was associated with the E4 allele (adjusted odds ratio 0.164, 95% confidence interval 0.031~ 0.876, P = 0.034). Conclusion: APOE E4 is associated with decreased serum high density lipoprotein concentration in healthy elderly. However, the above conclusions need to be further verified.

Apolipoprotein E particle size is increased in Alzheimer's disease

Introduction

Apolipoprotein E4 (apoE4) is the predominant risk factor for late-onset Alzheimer's disease (AD), but the question of which structural differences might explain its effect remains unclear.

Methods

We compared high-density lipoprotein–like apoE particles from 12 AD and 10 control patients using size-exclusion chromatography.

Results

ApoE particles from patients genotyped as ε4/ε4 were 2.2 ± 0.3 times as massive as particles from ε3/ε3 control subjects and 1.4 ± 0.1 times as massive as particles from ε3/ε3 AD patients. The increased particle size was not because of incorporation of amyloid β or apoE proteolysis products. Particles from AD patients genotyped as ε3/ε3 were 1.59 ± 0.27 times as massive as ε3/ε3 control subjects.

Discussion

Increased particle size in AD is affected by APOE genotype and by disease-related differences in assembly or stability. These differences suggest that lipoprotein assembly or stability in AD brain plays an important role in determining apoE4 pathogenicity.

Reversal of ApoE4-induced recycling block as a novel prevention approach for Alzheimer's disease

ApoE4 genotype is the most prevalent and also clinically most important risk factor for late-onset Alzheimer’s disease (AD). Available evidence suggests that the root cause for this increased risk is a trafficking defect at the level of the early endosome. ApoE4 differs from the most common ApoE3 isoform by a single amino acid that increases its isoelectric point and promotes unfolding of ApoE4 upon endosomal vesicle acidification. We found that pharmacological and genetic inhibition of NHE6, the primary proton leak channel in the early endosome, in rodents completely reverses the ApoE4-induced recycling block of the ApoE receptor Apoer2/Lrp8 and the AMPA- and NMDA-type glutamate receptors that are regulated by, and co-endocytosed in a complex with, Apoer2. Moreover, NHE6 inhibition restores the Reelin-mediated modulation of excitatory synapses that is impaired by ApoE4. Our findings suggest a novel potential approach for the prevention of late-onset AD.

Alzheimer’s disease is a degenerative condition that destroys connections between brain cells leading to memory loss, confusion and difficulties in thinking. Apolipoprotein E is a protein that carries fatty substances called lipids and cholesterol around the brain, and plays an important role in repair mechanisms. There are three major forms of Apolipoprotein E, and individuals who carry a version known as ApoE4 are up to 10 times more likely to develop Alzheimer’s disease than those who carry other variations.

In nerve cells, or neurons, Apolipoprotein E binds to a specific family of receptors. One of these receptors, called Apoer2, is found in the synaptic gap between neurons, where it regulates their activities. Both Apolipoprotein E and Apoer2 are taken into the cell within compartments known as endosomal vesicles. Usually, the Apoer2 receptor is quickly recycled back to the surface of the cell, but this recycling process is delayed in individuals with the ApoE4 version of Apolipoprotein E.

Apoer2 is just one of many different receptors on the surface of neurons that are taken into vesicles before being recycled back to the cell surface. The fluid inside these vesicles becomes progressively more acidic as they move through the cell. This process helps to control the interaction of these receptors with their binding partners and to regulate their movement and recycling. Here, Xian, Pohlkamp et al. investigated whether changing the acidity of vesicles in rat neurons could overcome the block in recycling Apoer2 – and other receptors that travel with Apoer2 in the same compartments – in the presence of ApoE4.

A protein called NHE6 is embedded in the membrane of vesicles called early endosomes and acts to make the vesicles less acidic. Xian, Pohlkamp et al. used drugs to block the activity of NHE6, which led to the vesicles becoming more acidic and allowed Apoer2 to be recycled faster. Using a genetic approach known as siRNA knockdown to decrease the amount of NHE6 produced in neurons also had a similar effect on Apoer2 recycling.

Together these findings suggest that drugs that make vesicles in neurons more acidic may have the potential to help prevent individuals that carry the ApoE4 protein from developing Alzheimer’s disease. Current drugs that target NHE6 also affect other molecules, which can often lead to side effects. A next step will be to develop tailor-made, small molecule drugs that can enter the brain efficiently and selectively block NHE6.

Development of a new biochip array for APOE4 classification from plasma samples using immunoassay-based methods

BACKGROUND

Apolipoprotein E (APOE) is a key player in lipid transport and metabolism and exists in three common isoforms: APOE2, APOE3 and APOE4. The presence of the E4 allelic variant is recognized as a major genetic risk factor for dementia and other chronic (neuro)degenerative diseases. The availability of a validated assay for rapid and reliable APOE4 classification is therefore advantageous.

METHODS

Biochip array technology (BAT) was successfully applied to identify directly the APOE4 status from plasma within 3 h, through simultaneous immunoassay-based detection of both specific APOE4 and total APOE levels.

RESULTS

Samples (n=432) were first genotyped by polymerase chain reaction (PCR), and thereafter, using BAT, the corresponding plasma was identified as null, heterozygous or homozygous for the E4 allele by calculating the ratio of APOE4 to total APOE protein. Two centers based in Austria and Ireland correctly classified 170 and 262 samples, respectively, and achieved 100% sensitivity and specificity.

CONCLUSIONS

This chemiluminescent biochip-based sandwich immunoarray provides a novel platform to detect rapidly and accurately an individual's APOE4 status directly from plasma. The E4 genotype of individuals has been shown previously to affect presymptomatic risk, prognosis and treatment response for a variety of diseases, including Alzheimer's disease. The biochip's potential for being incorporated in quantitative protein biomarker arrays capable of analyzing disease stages makes it a superior alternative to PCR-based APOE genotyping and may deliver additional protein-specific information on a variety of diseases in the future.

A case of lipoprotein glomerulopathy with a rare apolipoprotein E isoform combined with neurofibromatosis type I

Lipoprotein glomerulopathy (LPG) is a rare inherited disease characterized by histopathological features of lipoprotein thrombi in dilated glomerular capillaries and type III like hyperlipoproteinemia with heterozygous mutation of the apolipoprotein (apo) E gene. We herein present the case of a 50-year-old woman with LPG complicated by neurofibromatosis type 1 (NF1). To the best of our knowledge, this is the first report of a case of LPG complicated by NF1. On the other hand, she had not only a heterozygous apoE-Sendai mutation, which is one of the most frequent apoE variants in LPG patients, but also a rare isoform of ApoE5 (Glu3Lys). Although apoE mutation has been recognized as having a principal role in the pathogenesis of LPG, some other factors are assumed to be present in the pathogenesis of LPG, because many asymptomatic carriers of apoE variants are recognized. The coexistence of NF1 or apoE5 (Glu3Lys) allele might play a role as an additional factor in the development of LPG.

Specific patterns of whole-brain structural covariance of the anterior and posterior hippocampus in young APOE ε4 carriers

Apolipoprotein E (APOE) ε4 has been associated with smaller hippocampal volumes in healthy aging, while findings in young adults are inconclusive. Previous studies have mostly used univariate methods, and without considering potential anterior/posterior differences. Here, we used a multivariate method, partial least squares, and assessed whole-brain structural covariance of the anterior (aHC) and posterior (pHC) hippocampus in young adults (n=97) as a function of APOE ε4 status and sex. Two significant patterns emerged: (1) specific structural covariance of the aHC with frontal regions, temporal and occipital areas in APOE ε4 women, whereas the volume of both the aHC and pHC in all other groups co-varied with frontal, parietal and cerebellar areas; and (2) opposite structural covariance of the pHC in ε4 carriers compared to the aHC in non-carriers, with the pHC of ε4 carriers covarying with parietal and frontal areas, and the aHC of ε4 non-carriers covarying with motor areas and the middle frontal gyrus. APOE ε4 has in young adults been associated with better episodic and spatial memory, functions involving the aHC and pHC, respectively. We found no associations between structural covariance and performance, suggesting that other factors underlie the performance differences seen between carriers and non-carriers. Our findings indicate that APOE ε4 carriers and non-carriers differ in hippocampal organization and that there are differences as a function of sex and hippocampal segment. They stress the need to consider the hippocampus as a heterogeneous structure, and highlight the benefits of multivariate methods in assessing group differences in the brain.

APOE polymorphisms influence longitudinal lipid trends preceding intracerebral hemorrhage

Objective:

We sought to determine whether APOE genotype influences a previously observed decline in serum total cholesterol (TC) and low-density lipoprotein (LDL) levels preceding primary intracerebral hemorrhage (ICH), as a potential demonstration of nonamyloid mechanisms of APOE in ICH risk.

Methods:

We performed a single-center retrospective longitudinal analysis using patients with known APOE genotype drawn from an ongoing cohort study of ICH. Serum lipid measurements for TC, triglycerides (TGs), LDL, and high-density lipoprotein (HDL) collected within 2 years before and after index ICH were extracted from electronic medical records. Piecewise linear mixed-effects models were used to compare APOE allele–specific effects on temporal serum lipid trends in ICH. Demographics, medical history, medications, and health maintenance data were included as fixed effects. Inter- and intraindividual variations in lipid levels were modeled as random effects.

Results:

A total of 124 ICH cases were analyzed. APOE ε4 carriers had greater rates of decline in serum TC and LDL within 6 months preceding ICH (TC: −7.30 mg/dL/mo, p = 0.0035; LDL: −8.44 mg/dL/mo, p = 0.0001). Conversely, serum TC and LDL levels in APOE ε2 carriers were unchanged within the same time period. APOE genotype had no associations with serum HDL or TG trends.

Conclusions:

APOE allele status predicts serum TC and LDL changes preceding acute ICH. Our results have implications for ongoing efforts in dissecting the role of dyslipidemia in cerebrovascular disease risk. APOE genotype–specific influence on lipid trends provides a clue for one mechanism by which APOE may influence risk of ICH. Further characterization of the metabolic roles of APOE is needed to improve the understanding of APOE biology in cerebrovascular disease risk.

Direct analysis of VLDL by TOF-MS allows rapid definition of Apo E genotypes and facilitates characterisation of post translational changes

BACKGROUND

Apolipoprotein E (Apo E) is a glycoprotein which acts as a ligand facilitating the uptake of lipids. Three common isoforms of Apo E are recognised, E2, E3 and E4. E2 and E4 are associated with altered lipid metabolism and increased cardiovascular risk. We report a novel variant of Apo E (c.382G>A) predicting 110Asp→Asn identified by genotyping, we were prompted to investigate this further as the amino acid substitution produced a prospective N-glycosylation site in this novel variant.

METHODS

We present a new rapid approach to genotyping Apo E performed by electrospray TOF-MS, on the same sample analysed by ultracentrifugation. The analysis can be performed in <10min and requires minimal sample volume. Control samples were used to verify the analysis.

RESULTS

Spectra showed the expected mass for the E3 isoform at 34,237Da, E2 and E4 isoforms were identifiable by peaks at -53Da and +53Da respectively. Post translational glycosylation of the protein can also be identified. The novel isoform had a mass of 34,237Da without evidence of N-glycosylation. No significant effect on lipid metabolism was identified.

CONCLUSION

The electrospray TOF-MS approach potentially provides a rapid alternative method for genotyping Apo E and for the investigation of novel isoforms.

Cholesterol in brain disease: sometimes determinant and frequently implicated

Cholesterol is essential for neuronal physiology, both during development and in the adult life: as a major component of cell membranes and precursor of steroid hormones, it contributes to the regulation of ion permeability, cell shape, cell-cell interaction, and transmembrane signaling. Consistently, hereditary diseases with mutations in cholesterol-related genes result in impaired brain function during early life. In addition, defects in brain cholesterol metabolism may contribute to neurological syndromes, such as Alzheimer's disease (AD), Huntington's disease (HD), and Parkinson's disease (PD), and even to the cognitive deficits typical of the old age. In these cases, brain cholesterol defects may be secondary to disease-causing elements and contribute to the functional deficits by altering synaptic functions. In the first part of this review, we will describe hereditary and non-hereditary causes of cholesterol dyshomeostasis and the relationship to brain diseases. In the second part, we will focus on the mechanisms by which perturbation of cholesterol metabolism can affect synaptic function.

Etiology and pathogenesis of late-onset Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative condition that occurs in two forms, an early-onset form that is genetically determined and a far more common late-onset form that is not. In both cases, the disease results in severe cognitive dysfunction, among other problems, and the late-onset form of the disease is now considered to be the most common cause of dementia among the elderly. While a good deal of research has been focused on elucidating the etiology of the late-onset form for more than two decades, results to date have been modest and have not yet engendered useful therapeutic strategies for cure of the disease. In this review, we discuss the prevalent ideas that have governed this research for several years, and we challenge these ideas with alternative findings suggesting a multifactorial etiology. We review promising newer ideas that may prove effective as therapeutic interventions for late-onset AD, as well as providing reliable means of earlier and more specific diagnosis of the disease process. In the discussions included here, we reference relevant clinical and basic science literature underlying research into disease etiology and pathogenesis, and we highlight current reviews on the various topics addressed.

How proteomics reveals potential biomarkers in brain diseases

The brain is complex, and so are the proteomics studies of brain tissue and its diseases, including Alzheimer's Disease, Parkinson's Disease and schizophrenia. In this review, general considerations and strategies of proteomics technologies, the advantages and challenges as well as the special needs for brain tissue are described and summarized. In addition, the results of the first studies are presented including a quality evaluation of the candidate proteins for these diseases. A paragraph is dedicated to the efforts of standardization in this field.

Quantifying diet for nutrigenomic studies

The field of nutrigenomics shows tremendous promise for improved understanding of the effects of dietary intake on health. The knowledge that metabolic pathways may be altered in individuals with genetic variants in the presence of certain dietary exposures offers great potential for personalized nutrition advice. However, although considerable resources have gone into improving technology for measurement of the genome and biological systems, dietary intake assessment remains inadequate. Each of the methods currently used has limitations that may be exaggerated in the context of gene × nutrient interaction in large multiethnic studies. Because of the specificity of most gene × nutrient interactions, valid data are needed for nutrient intakes at the individual level. Most statistical adjustment efforts are designed to improve estimates of nutrient intake distributions in populations and are unlikely to solve this problem. An improved method of direct measurement of individual usual dietary intake that is unbiased across populations is urgently needed.

Central leptin and insulin administration modulates serum cytokine- and lipoprotein-related markers

In most obese patients there is an inflammatory state characterized by lipid abnormalities, hyperleptinemia and hyperinsulinemia.

OBJECTIVE

The objective was to identify mechanisms involved in leptin's role in the attenuation of the response to insulin using a proteomic approach.

MATERIAL/METHODS

We studied the serum proteomic profile of rats treated by central leptin infusion followed by an injection of insulin. We analyzed the relationship between these proteins and serum cytokine and apolipoprotein levels.

RESULTS

Out of 81 protein spots, intensity differences were found in 11, corresponding to 5 proteins: three isoforms of α1 macroglobulin; three of haptoglobin and serum amyloid P component-precursor. All of these are acute-phase proteins involved in inflammation and are correlated with cytokine levels. Additionally, two apolipoprotein E and two apolipoprotein A1 isoforms were identified and were found to correlate with LDL and HDL.

CONCLUSIONS

Our results indicate that increased leptin and insulin levels change these circulating proteins, thus promoting systemic inflammation and changing lipid metabolism.

The ε4 allele of the APOE gene is associated with more severe peripheral neuropathy in type 2 diabetic patients

We examined the association between the ε4 allele of the apolipoprotein E gene and severity of peripheral neuropathy in 234 patients with type 2 diabetes mellitus (T2DM). Based on the Neuropathy Disability Score (NDS), patients were divided into group A (NDS ≤ 6: mild or no neuropathy) and group B (NDS > 6: severe neuropathy). In each group, patients were further divided into ε4 carriers and non-ε4 carriers. In multivariate analysis, a more than 5-fold increased risk of severe neuropathy was associated with ε4 carrier status (adjusted odds ratio [aOR]: 5.26, 95% confidence interval [CI]: 2.24-12.31, P = .0001). The other significant risk factors for severe neuropathy included male gender (aOR: 2.08, 95% CI: 1.05-4.14, P = .036), diabetes duration (aOR: 1.05, 95% CI: 1.00-1.09, P = .039), and hemoglobin A1c (aOR: 1.32, 95% CI: 1.05-1.66, P = .020). In conclusion, the ε4 carrier status appears to be associated with severe peripheral neuropathy in T2DM.

Non-replication of an association of Apolipoprotein E2 with sinistrality

A recent report found that left-handed adolescents were more than three times more likely to have an Apolipoprotein (APOE) ϵ2 allele. This study was unable to replicate this association in young adults (N=166). A meta-analysis of nine other datasets (N=360 to 7559, Power > 0.999) including that of National Alzheimer's Coordinating Center also failed to find an over-representation of ϵ2 among left-handers indicating that this earlier outcome was most likely a statistical artefact.

Diabetes mellitus and Alzheimer's disease: shared pathology and treatment?

Epidemiological and basic science evidence suggest a possible shared pathophysiology between type 2 diabetes mellitus (T2DM) and Alzheimer's disease (AD). It has even been hypothesized that AD might be 'type 3 diabetes'. The present review summarizes some of the evidence for the possible link, putative biochemical pathways and ongoing clinical trials of antidiabetic drugs in AD patients. The primary and review literature were searched for articles published in peer-reviewed sources that were related to a putative connection between T2DM and AD. In addition, public sources of clinical trials were searched for the relevant information regarding the testing of antidiabetic drugs in AD patients. The evidence for a connection between T2DM and AD is based upon a variety of diverse studies, but definitive biochemical mechanisms remain unknown. Additional study is needed to prove the existence or the extent of a link between T2DM and AD, but sufficient evidence exists to warrant further study. Presently, AD patients might benefit from treatment with pharmacotherapy currently used to treat T2DM and clinical trials of such therapy are currently underway.

Interactions of Npc1 and amyloid accumulation/deposition in the APP/PS1 mouse model of Alzheimer's

Although Niemann-Pick C1 disease has frequently been called "juvenile Alzheimer's", the effects of introducing Npc1 mutations into a mouse model of Alzheimer's have not previously been performed. We have crossed Npc1 (+/-) mice with APP/PS1 "Alzheimer's" mice and studied Aβ42 accumulation and amyloid plaque formation. Mice heterozygous for Npc1 and positive for the APP and PS1 transgenes accumulated Aβ42 more rapidly than the APP/PS1 controls and this correlated, as expected, with the area of amyloid plaques. We conclude that the alterations of intracellular cholesterol present in Npc1 (+/-) mice can influence the progress of Alzheimer's disease in the APP/PS1 mouse model.

Association between hepatic lipase -514 C/T promoter polymorphism and myocardial infarction is modified by history of hypercholesterolemia and waist circumference

BACKGROUND AND AIMS

To examine whether the association between the -514 C/T polymorphism of the hepatic lipase gene and myocardial infarction (MI) is modified by history of hypercholesterolemia and increased waist circumference.

METHODS AND RESULTS

A total of 1940 pairs of nonfatal MI cases and population-based controls were genotyped. Multiple conditional logistic regression was used for data analyses. The -514T variant was not associated with MI in the whole population. However, among people with history of hypercholesterolemia the T allele increased MI risk for heterozygous and homozygous carriers, respectively [OR=1.25 (95%CI=0.92-1.70) and OR=1.59 (95%CI=1.09-2.32). In contrast, the T allele decreased MI risk among people with no history of hypercholesterolemia [OR=0.85 (95%CI=0.70-1.03) and OR=0.76 (95%CI=0.60-0.97)], p for interaction=0.004. Among subjects with normal waist circumference there was no association between the -514T allele and MI for heterozygous and homozygous carriers, respectively [OR=1.04 (95%CI=0.86-1.25) and OR=0.96 (95%CI=0.77-1.21)], while among subjects with waist circumference above the limits of the metabolic syndrome definition there was a protective association [OR=0.63 (95%CI=0.45-0.90) and OR=0.81 (95%CI=0.53-1.25) p for interaction=0.04].

CONCLUSION

The -514T allele is associated with MI in opposite directions depending on the background of the studied population. This could explain what seem like inconsistent results across studies.

Apolipoprotein E genotype and hepatitis C, HIV and herpes simplex disease risk: a literature review

Apolipoprotein E is a polymorphic and multifunctional protein with numerous roles in lipoprotein metabolism. The three common isoforms apoE2, apoE3 and apoE4 show isoform-specific functional properties including different susceptibilities to diseases. ApoE4 is an accepted risk factor for Alzheimer's disease and cardiovascular disorders. Recently, associations between apoE4 and infectious diseases have been demonstrated. This review summarises how apoE4 may be involved in the infection incidence and associated pathologies of specific infectious diseases, namely hepatitis C, human immunodeficiency virus disease and herpes simplex.ApoE4 seems to be protective against chronic hepatitis C virus infection and retards fibrosis progression. In contrast apoE4 enhances the fusion rate of human immunodeficiency virus with target cell membranes, resulting in accelerated cell entry and faster disease progression. Its association with human immunodeficiency virus-associated dementia remains controversial. Regarding herpes simplex virus infection, apoE4 intensifies virus latency and is associated with increased oxidative damage of the central nervous system, and there is some evidence that herpes simplex virus infection in combination with the apoE4 genotype may be associated with an increased risk of Alzheimer's disease. In addition to reviewing available data from human trials, evidence derived from a variety of cell culture and animal models are considered in this review in order to provide mechanistic insights into observed association between apoE4 genotype and viral disease infection and pathology.

APOE distribution in world populations with new data from India and the UK

BACKGROUND

The APOE gene and its protein product is associated with a number of plasma proteins like very-low density lipoprotein (VLDL), high density lipoprotein (HDL) chylomicrons, chylomicron remnants, and plays a crucial role in lipid metabolism. The APOE gene is polymorphic and common alleles (*E2, *E3 and *E4) have been associated with a number of common and complex diseases in different populations. Due to their crucial role in metabolism and clinical significance, it is imperative that allelic variation in different populations is analysed to evaluate the usage of APOE in an evolutionary and clinical context.

AIM

We report allelic variation at the APOE locus in three European and four Indian populations and evaluate global patterns of genetic variation at this locus. The large, intricate and unexpected heterogeneity of this locus in its global perspective may have insightful consequences, which we have explored in this paper.

SUBJECT AND METHODS

Apolipoprotein E genotypes were determined in four population groups (Punjabi Sikhs, Punjabi Hindus, Maria Gonds and Koch, total individuals = 497) of India and three regionally sub-divided British populations (Nottinghamshire, East Midlands and West Midlands, total individuals = 621). The extent and distribution of APOE allele frequencies were compared with 292 populations of the world using a variety of multivariate methods.

RESULTS

Three alleles, APOE*E2, APOE*E3 and APOE*E4, were observed with contrasting variation, although *E4 was absent in the tribal population of Koch. Higher heterozygosities (>43%) in British populations reflected their greater genetic diversity at this locus. The overall pattern of allelic diversity among these populations is comparable to many European and Indian populations. At a global level, higher frequencies of the *E2 allele were observed in Africa and Oceania (0.099 +/- 0.083 and 0.111 +/- 0.052, respectively). Similarly, *E4 allele averages were higher in Oceania (0.221 +/- 0.149) and Africa (0.209 +/- 0.090), while Indian and Asian populations showed the highest frequencies of *E3 allele. The coefficient of gene differentiation was found to be highest in South America (9.6%), although the highest genetic diversity was observed in Oceania (48.7%) and Africa (46.3%). APOE*E2 revealed a statistically significant decreasing cline towards the north in Asia (r = -0.407, d.f. = 70, p < 0.05), which is not compatible with the coronary heart disease statistics in this continent. APOE*E4 showed a significant increasing cline in North European populations. Spatial autocorrelation analysis shows that the variation at this locus is influenced by 'isolation by distance' with a strong positive correlation for lower distances up to 1313 km.

CONCLUSION

Overall APOE allelic variation in UK and Indian populations is comparable to previous studies but in tribal populations *E4 allele frequency was very low or absent. At a global level allelic variation shows that geography, isolation by distance, genetic drift and possibly pre-historical selection are responsible for shaping the spectrum of genetic variation at the APOE gene. Overall, APOE is a good anthropogenetic and clinical diagnostic marker.

Admixture mapping of quantitative trait loci for blood lipids in African-Americans

Blood lipid levels, including low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG), are highly heritable traits and major risk factors for atherosclerotic cardiovascular disease (CVD). Using individual ancestry estimates at marker locations across the genome, we present a novel quantitative admixture mapping analysis of all three lipid traits in a large sample of African-Americans from the Family Blood Pressure Program. Regression analysis was performed with both total and marker-location-specific European ancestry as explanatory variables, along with demographic covariates. Robust permutation analysis was used to assess statistical significance. Overall European ancestry was significantly correlated with HDL-C (negatively) and TG (positively), but not with LDL-C. We found strong evidence for a novel locus underlying HDL-C on chromosome 8q, which correlated negatively with European ancestry (P = .0014); the same location also showed positive correlation of European ancestry with TG levels. A region on chromosome 14q also showed significant negative correlation between HDL-C levels and European ancestry. On chromosome 15q, a suggestive negative correlation of European ancestry with TG and positive correlation with HDL-C was observed. Results with LDL-C were less significant overall. We also found significant evidence for genome-wide ancestry effects underlying the joint distribution of HDL-C and TG, not fully explained by the locus on chromosome 8. Our results are consistent with a genetic contribution to and may explain the healthier HDL-C and TG profiles found in Blacks versus Whites. The identified regions provide locations for follow-up studies of genetic variants underlying lipid variation in African-Americans and possibly other populations.

Genetic influences on blood lipids and cardiovascular disease risk: tools for primary prevention

Genetic polymorphism in human populations is part of the evolutionary process that results from the interaction between the environment and the human genome. Recent changes in diet have upset this equilibrium, potentially influencing the risk of most common morbidities such as cardiovascular diseases, obesity, diabetes, and cancer. Reduction of these conditions is a major public health concern, and such a reduction could be achieved by improving our ability to detect disease predisposition early in life and by providing more personalized behavioral recommendations for successful primary prevention. In terms of cardiovascular diseases, polymorphisms at multiple genes have been associated with differential effects in terms of lipid metabolism; however, the connection with cardiovascular disease has been more elusive, and considerable heterogeneity exists among studies regarding the predictive value of genetic markers. This may be because of experimental limitations, the intrinsic complexity of the phenotypes, and the aforementioned interactions with environmental factors. The integration of genetic and environmental complexity into current and future research will drive the field toward the implementation of clinical tools aimed at providing dietary advice optimized for the individual's genome. This may imply that dietary changes are implemented early in life to gain maximum benefit. However, it is important to highlight that most reported studies have focused on adult populations and to extrapolate these findings to children and adolescents may not be justified until proper studies have been carried out in these populations and until the ethical and legal issues associated with this new field are adequately addressed.

Genotype-phenotype associations: modulation by diet and obesity

Changes in diet are likely to reduce chronic disorders, but after decades of active research and heated discussion, the question still remains: what is the optimal diet to achieve this elusive goal? Is it a low-fat diet, as traditionally recommended by multiple medical societies? Or a high monounsaturated fat (MUFA) diet as predicated by the Mediterranean diet? Perhaps a high polyunsaturated fat (PUFA) diet based on the cholesterol-lowering effects? The right answer may be all of the above but not for everybody. A well-known phenomenon in nutrition research and practice is the dramatic variability in interindividual response to any type of dietary intervention. There are many other factors influencing response, and they include, among many others, age, sex, physical activity, alcohol, and smoking as well as genetic factors that will help to identify vulnerable populations/individuals that will benefit from a variety of more personalized and mechanistic-based dietary recommendations. This potential could and needs to be developed within the context of nutritional genomics that in conjunction with systems biology may provide the tools to achieve the holy grail of dietary prevention and therapy of chronic diseases and cancer. This approach will break with the traditional public health approach of "one size fits all." The current evidence based on nutrigenetics has begun to identify subgroups of individuals who benefit more from a low-fat diet, whereas others appear to benefit more from high MUFA or PUFA diets. The continuous progress in nutrigenomics will allow some time in the future to provide targeted gene-based dietary advice.

Variation in NPC1, the gene encoding Niemann-Pick C1, a protein involved in intracellular cholesterol transport, is associated with Alzheimer disease and/or aging in the Polish population

There is abundant evidence that cholesterol metabolism, especially as mediated by the intercellular transporter APOE, is involved in the pathogenesis of sporadic, late-onset Alzheimer disease (SLAD). Identification of other genes involved in SLAD pathogenesis has been hampered since gene association studies, whether individual or genome-wide, experience difficulty in finding appropriate controls in as much as 25% or more of normal adults will develop SLAD. Using 152 centenarians as additional controls and 120 "regular", 65-75-year-old controls, we show an association of genetic variation in NPC1 with SLAD and/or aging. In this preliminary study, we find gradients of two non-synonymous SNP's allele frequencies in NPC1 from centenarians through normal controls to SLAD in this non-stratified Polish population. An intervening intronic SNP is not in Hardy-Weinberg equilibria and differs between centenarians and controls/SLAD. Haplotypes frequencies determined by fastPHASE were somewhat different, and the predicted genotype frequencies were very different between the three groups. These findings can also be interpreted as indicating a role for NPC1 in aging, a role also suggested by NPC1's role in Dauer formation (hibernation, a longevity state) in Caenorhabditis elegans.

Apolipoprotein E gene polymorphism and serum lipid levels in the Guangxi Hei Yi Zhuang and Han populations

Hei Yi Zhuang is an isolated subgroup of the Zhuang minority in China. Little is known about the distribution of apolipoprotein (apo) E genetic variations and its role in lipid metabolism in this population. The present study was undertaken to compare the effect of apoE gene polymorphism on serum lipid levels between the Guangxi Hei Yi Zhuang and Han populations. A total of 873 subjects of Hei Yi Zhuang and 867 participants of Han Chinese were surveyed by a stratified randomized cluster sampling. Genotyping of apoE was performed using polymerase chain reaction and restriction fragment length polymorphism. The frequencies of 2, 3, and 4 alleles were 15.23%, 79.84%, and 4.93% in Hei Yi Zhuang, and 9.23%, 81.43%, and 9.34% in Han (P < 0.001); respectively. The frequencies of 2/ 2, 2/ 3, 2/ 4, 3/ 3, 3/ 4, and 4/ 4 genotypes were 4.70%, 17.86%, 3.21%, 68.16%, 5.50%, and 0.57% in Hei Yi Zhuang, and 2.54%, 9.23%, 4.15%, 70.70%, 12.23%, and 1.15% in Han (P < 0.001); respectively. Total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and apoB levels were lower in Hei Yi Zhuang than in Han (P < 0.01-0.001), but high-density lipoprotein cholesterol (HDL-C) levels and the ratio of apoA-I to apoB were higher in Hei Yi Zhuang than in Han (P < 0.001 for each). There were significant differences in TC, HDL-C, LDL-C, and apoB levels among the six genotypes in both ethnic groups (P < 0.01-0.001). Hyperlipidemia was positively correlated with age, body mass index, hypertension, alcohol consumption, and apoE allele in both populations (P < 0.05-0.001). TC, LDL-C, and apoB levels were positively correlated, and HDL-C levels were negatively associated with apoE genotypes in both ethnic groups (P < 0.001 for all). The differences in the lipid profiles between Hei Yi Zhuang and Han Chinese might partly attribute to the differences in apoE genotypic and allelic frequencies.

Testing informative missingness in genetic studies using case-parent triads

In genetic studies, the transmission/disequilibrium test (TDT) using case-parent triads has gained popularity attributable to its robustness to population admixture. Several extensions have been proposed to accommodate incomplete triads. Some strategies assume that parental genotypes are missing completely at random (MCAR) to insure an unbiased conclusion and some methods allow parental genotypes to be missing informatively, resulting in reduced power when the missing data pattern is indeed MCAR. However, these tests assumed that offspring genotypes were MCAR. Recently, Guo indicated that when offspring genotypes were missing informatively, an occurrence that can be considered as ascertainment bias, inflated type-I error and/or reduced power may occur using the TDT when incomplete triads are excluded. In an effort to avoid an erroneous conclusion, we propose a strategy called testing informative missingness (TIM) that compares conditional distributions of parental genotypes among complete triads and incomplete data with only one parent to examine the missing data pattern. Through computer simulations, TIM has decent power to detect informative missingness and is robust to population admixture. In addition, we illustrate TIM with an application to the Framingham Heart Study.

Gender, a significant factor in the cross talk between genes, environment, and health

BACKGROUND

Although men and women share most genetic information, they have significantly different disease susceptibilities that go well beyond the expected gender-specific diseases. Sex influences the risk of nearly all common diseases that affect both men and women, including atherosclerosis and diabetes and their preceding risk factors (eg, hyperlipidemia, insulin resistance, and obesity).

OBJECTIVE

The goal of this article was to examine the interplay between genes, gender, and disease susceptibility, and assess it in the context of the added complexity of environmental factors (ie, dietary habits, smoking, alcohol consumption) in the modulation of the balance between health and disease.

METHODS

Original and review articles published by the author were reexamined for evidence of gene-gender interactions.

RESULTS

Evidence from some key factors in lipid metabolism (apolipoprotein E [APOE])and obesity (perilipin [PLIN]) indicates that the interplay between genes, gender, and environmental factors modulates disease susceptibility. In the Framingham Heart Study, complex interactions have been shown between a promoter polymorphism at the apolipoprotein A1 gene, gender, and dietary poly-unsaturated fatty acid intake that modulate plasma concentrations of high-density lipoprotein cholesterol. Likewise, highly and clinically relevant interactions have been observed between the APOE gene common alleles APOE2 , APOE3, and APOE4 , gender, and smoking that determine cardiovascular disease risk. Most interesting is the gender-dependent association between common polymorphisms at the PLIN locus and obesity risk that has been replicated in several populations around the world.

CONCLUSIONS

These data support the idea that gender-specific differences in morbidity and mortality may be mediated in part by genetic factors and by their differential response to the environment. The new knowledge generated by a more careful and complete elucidation of the complex interactions predisposing to common diseases will result in an increased ability to provide successful personalized behavioral recommendations to prevent chronic disorders.

Apolipoprotein E4 enhances attachment of Chlamydophila (Chlamydia) pneumoniae elementary bodies to host cells

Chlamydophila (Chlamydia) pneumoniae is an intracellular respiratory pathogen known to cause community-acquired pneumonia. Infection with this organism has been associated with atherosclerosis, inflammatory arthritis, and other chronic diseases, many of which also have been associated with possession of the epsilon4 allele at the APOE locus on (human) chromosome 19. An earlier study from this laboratory suggested that some relationship exists between apolipoprotein E4 (apoE4), the product of the epsilon4 allele, and the pathobiology of C. pneumoniae. A standard attachment assay and real time PCR targeting a sequence on the C. pneumoniae chromosome were used to monitor host cell binding of elementary bodies (EB) of that organism. Our data indicate that 3-fold more EB of strain AR-39 attach to an epsilon3 homozygous human cell line transfected with a plasmid expressing the epsilon4 coding sequence than to the same cell line harboring empty vector, vector containing an irrelevant insert sequence, or vector containing the DNA sequence encoding apoE3. The quantitative real time data were confirmed by immunolabeling of chlamydial inclusions in parallel attachment and infection assays. Experiments using Chlamydophila trachomatis EB showed no enhancement of attachment in the presence of the epsilon4 allele in any assays. These observations indicate that apoE4 enhances attachment of C. pneumoniae EB, but not those of C. trachomatis, to target host cells.

A genome-wide association study for blood lipid phenotypes in the Framingham Heart Study

BACKGROUND

Blood lipid levels including low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG) are highly heritable. Genome-wide association is a promising approach to map genetic loci related to these heritable phenotypes.

METHODS

In 1087 Framingham Heart Study Offspring cohort participants (mean age 47 years, 52% women), we conducted genome-wide analyses (Affymetrix 100K GeneChip) for fasting blood lipid traits. Total cholesterol, HDL-C, and TG were measured by standard enzymatic methods and LDL-C was calculated using the Friedewald formula. The long-term averages of up to seven measurements of LDL-C, HDL-C, and TG over a approximately 30 year span were the primary phenotypes. We used generalized estimating equations (GEE), family-based association tests (FBAT) and variance components linkage to investigate the relationships between SNPs (on autosomes, with minor allele frequency > or =10%, genotypic call rate > or =80%, and Hardy-Weinberg equilibrium p > or = 0.001) and multivariable-adjusted residuals. We pursued a three-stage replication strategy of the GEE association results with 287 SNPs (P < 0.001 in Stage I) tested in Stage II (n approximately 1450 individuals) and 40 SNPs (P < 0.001 in joint analysis of Stages I and II) tested in Stage III (n approximately 6650 individuals).

RESULTS

Long-term averages of LDL-C, HDL-C, and TG were highly heritable (h2 = 0.66, 0.69, 0.58, respectively; each P < 0.0001). Of 70,987 tests for each of the phenotypes, two SNPs had p < 10(-5) in GEE results for LDL-C, four for HDL-C, and one for TG. For each multivariable-adjusted phenotype, the number of SNPs with association p < 10(-4) ranged from 13 to 18 and with p < 10(-3), from 94 to 149. Some results confirmed previously reported associations with candidate genes including variation in the lipoprotein lipase gene (LPL) and HDL-C and TG (rs7007797; P = 0.0005 for HDL-C and 0.002 for TG). The full set of GEE, FBAT and linkage results are posted at the database of Genotype and Phenotype (dbGaP). After three stages of replication, there was no convincing statistical evidence for association (i.e., combined P < 10(-5) across all three stages) between any of the tested SNPs and lipid phenotypes.

CONCLUSION

Using a 100K genome-wide scan, we have generated a set of putative associations for common sequence variants and lipid phenotypes. Validation of selected hypotheses in additional samples did not identify any new loci underlying variability in blood lipids. Lack of replication may be due to inadequate statistical power to detect modest quantitative trait locus effects (i.e., <1% of trait variance explained) or reduced genomic coverage of the 100K array. GWAS in FHS using a denser genome-wide genotyping platform and a better-powered replication strategy may identify novel loci underlying blood lipids.

Role of apolipoprotein E genotype in coronary artery disease

Recent gene-targeting technology has provided good animal models that provide insight into the pathology of complex diseases such as atherosclerosis. The apolipoprotein E gene polymorphism is one of the most extensively studied in cardiovascular medicine. The scope of the present review is to briefly outline the biochemical characteristics and the genetic variation of apolipoprotein E. Apolipoprotein E is best known for its role in modulating lipoprotein metabolism as a ligand for cellular receptors. Other functions unrelated to lipid transport are becoming known, including reverse cholesterol transport, immunoregulation and modulation of cell growth. This review will examine recent work that addresses how apolipoprotein E participates in atherosclerosis. Genotypic variation of apolipoprotein E has been associated with certain phenotypes regarding vascular disease, such as the presence of atherosclerosis and coronary heart disease outcomes. This article will also review evidence regarding the association between apolipoprotein E gene polymorphisms and coronary artery disease based upon experimental and clinical studies.

Informative-Transmission Disequilibrium Test (i-TDT): combined linkage and association mapping that includes unaffected offspring as well as affected offspring

To date, there is no test valid for the composite null hypothesis of no linkage or no association that utilizes transmission information from heterozygous parents to their unaffected offspring as well as the affected offspring from ascertained nuclear families. Since the unaffected siblings also provide information about linkage and association, we introduce a new strategy called the informative-transmission disequilibrium test (i-TDT), which uses transmission information from heterozygous parents to all of the affected and unaffected offspring in ascertained nuclear families and provides a valid chi-square test for both linkage and association. The i-TDT can be used in various study designs and can accommodate all types of independent nuclear families with at least one affected offspring. We show that the transmission/disequilibrium test (TDT) (Spielman et al. [1993] Am. J. Hum. Genet. 52:506-516) is a special case of the i-TDT, if the study sample contains only case-parent trios. If the sample contains only affected and unaffected offspring without parental genotypes, the i-TDT is equivalent to the sibship disequilibrium test (SDT) (Horvath and Laird [1998] Am. J. Hum. Genet. 63:1886-1897. In addition, the test statistic of i-TDT is simple, explicit and can be implemented easily without intensive computing. Through computer simulations, we demonstrate that power of the i-TDT can be higher in many circumstances compared to a method that uses affected offspring only. Applying the i-TDT to the Framingham Heart Study data, we found that the apolipoprotein E (APOE) gene is significantly linked and associated with cross-sectional measures and longitudinal changes in total cholesterol.

Distribution of apolipoprotein E alleles in a Scottish healthy newborn population

The different alleles of the human apolipoprotein E polymorphism, ApoE epsilon2, epsilon3, epsilon4, have important implications for systemic lipid metabolism, immunological function and for the brain in maintenance and in response to injury. Few studies have focussed on their role in early life. The ApoE alleles and genotypes were ascertained in the cord blood of 371 full-term and normal Scottish newborn infants using PCR methodology. The results were compared to previously published data for Scottish adults in late middle age. There was a marginally significant over-representation of epsilon4 and under-representation of epsilon3 alleles in healthy infants as compared with adults. Inspection of the individual genotypes confirms the over-representation of ApoE 4/4 and 2/4 with a reduction in ApoE 2/3 and 3/3 when compared with Scottish adults. Although these results may have occurred by chance, the ApoE epsilon4 allele may confer an increased risk of premature death.

Can a herpes simplex virus type 1 neuroinvasive score be correlated to other risk factors in Alzheimer's disease?

Herpes simplex virus type 1 (HSV-1) is latent in the nervous system of most humans. Ball [Can J Neurol Sci 9 (1982) 303] first suggested the hypothesis that HSV-1 could be involved in the pathogenesis of Alzheimer's Disease (AD) by noting that regions of the brain particularly and earliest affected in AD were the same as those most damaged during HSV encephalitis. Data from Itzhaki's research suggests that HSV-1 in the brain and the carriage of an apolipoprotein E allele 4 (ApoE e4) together confer risk for AD [J Pathol 97 (2002) 395], [Mol Chem Neuropathol 28 (1996) 135], [Alzheimer's Rep 1 (1998) 173], [Biochem Soc Trans 26 (1998) 273]. Of the two other studies based on Itzhaki's findings, one showed similar results [Lancet 349 (1997) 1102], and the other showed a similar trend [Lancet 351 (1998) 1330], [Lancet 352 (1998) 1312]. To further examine the role of HSV-1 in the etiology of AD, we have formulated a Neuroinvasive Score that quantifies the presence and viral load of HSV-1 in eight brain regions. These regions are: entorhinal cortex, hippocampus, pons, cerebellum, and neocortex (temporal, parietal, occipital, and frontal). We hypothesize that the Neuroinvasive Score that encompasses the presence, amount, and extent of HSV-1 spreading (neuroinvasiveness), will correlate with the genetic risk factor, ApoE e4, in the assessment of autopsy samples from AD patients. If the neuroinvasive score can be directly correlated to the different stages of AD (mild, moderate, severe), this will strengthen the hypothesis that HSV-1 is involved in AD and that ApoE e4 also confers risk for the development and progression of AD.

Statins lower the risk of developing Alzheimer’s disease by limiting lipid raft endocytosis and decreasing the neuronal spread of Herpes simplex virus type 1

Many possible risk factors for Alzheimer's disease (AD) have been investigated, with only a very few showing positive associations and none defining the etiology of the neurodegenerative disease. The presence of herpes simplex virus type 1 (HSV-1) DNA in the brain, coupled with apolipoprotein E allele e4 (ApoE e4), has been suggested to confer an increased risk for AD. Studies have shown that pathogens, including viruses, utilize clathrin-independent endocytosis, i.e., lipid rafts that contain cholesterol, as part of their structure. Moreover, cholesterol-lowering statins have recently been linked with a reduced risk of developing Alzheimer's dementia. We, therefore, posit that long-term statin therapy protects individuals from AD by reducing the neuronal spread of HSV-1 via lipid raft domain pathways. Although the mechanism by which statins reduce AD risk is unknown, they reduce the amount of cholesterol in the plasma membrane and, thus, may decrease the availability of lipid raft pathways to spread HSV-1 within the brain.

Nutritional genomics

Nutritional genomics has tremendous potential to change the future of dietary guidelines and personal recommendations. Nutrigenetics will provide the basis for personalized dietary recommendations based on the individual's genetic make up. This approach has been used for decades for certain monogenic diseases; however, the challenge is to implement a similar concept for common multifactorial disorders and to develop tools to detect genetic predisposition and to prevent common disorders decades before their manifestation. The preliminary results involving gene-diet interactions for cardiovascular diseases and cancer are promising, but mostly inconclusive. Success in this area will require the integration of different disciplines and investigators working on large population studies designed to adequately investigate gene-environment interactions. Despite the current difficulties, preliminary evidence strongly suggests that the concept should work and that we will be able to harness the information contained in our genomes to achieve successful aging using behavioral changes; nutrition will be the cornerstone of this endeavor.