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

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

Associations between Apolipoprotein E Genotype, Diet, Body Mass Index, and Serum Lipids in Lithuanian Adult Population

Background

Apolipoprotein E (APOE) polymorphism is associated with lipid levels. Some studies have reported that blood lipid response to diet or obesity varies depending on APOE genotypes. The aim of this study was to assess the effect of APOE genotypes, the intake of saturated fatty acids (SFA), and obesity on serum lipid levels in Lithuanian adult population.

Methodology/Principal Findings

A cross-sectional health survey was carried out in five municipalities of Lithuania. The random sample was obtained from lists of 25–64 year-old inhabitants registered at primary health care centres. The data from 996 subjects (416 men and 580 women) were analysed in this study. Two single-nucleotide polymorphisms (rs429358 and rs7412) were assessed using a real-time polymerase chain reaction. 24-hour recall and food frequency questionnaire were used for evaluation of dietary habits. Serum lipids were determined using enzymatic methods.Men and women with the APOE2 genotype had the lowest level of total cholesterol (TC) (p = 0.002 for men, and p = 0.02 for women) and low-density lipoprotein cholesterol (LDL-C) (p<0.001). Multivariate linear regression analysis showed that age, genotype APOE2, SFA intake, and body mass index (BMI) were significant determinants of TC and LDL-C level (with p values ranging from 0.043 to 0.001). Our data did not reveal any statistically significant interactions between APOE genotype and SFA intake or between APOE genotype and BMI regarding TC and LDL-C level (all p>0.05). However, the predictive power of the regression model for LDL-C improved when gene-BMI interaction and gene-BMI interaction plus gene-nutrient interaction were added (p = 0.04 and p = 0.032 for R² change, respectively).

Conclusions/Significance

APOE genotypes, SFA intake, and obesity were found to be associated with blood lipid levels in Lithuanian adult population. Analysis of gene-diet and gene-obesity interactions did not confirm that the effects of diet and obesity on TC and LDL-C level significantly depended on APOE genotype.     

Association Between Apolipoprotein E Gene Polymorphism and Myocardial Infarction

We investigated apolipoprotein E (APOE) genotypic influence on myocardial infarction risk in South India, where the disease is emerging as a major threat to the public health care system. The study included 412 subjects: 202 myocardial infarction patients and 210 age- and sex-matched controls. DNA was isolated, the polymorphism of the APOE gene was subjected to PCR, and lipid levels were evaluated. The prevalence of E3/E4 genotypes in patients (18.3%) was 1.5-fold that of controls (11.0%, p < 0.05), and the prevalence of E2/E3 genotypes was higher in controls (6.7%) than in patients (4%). The ε4 allele was significantly associated with myocardial infarction: χ ² = 12.4; OR 2.2 (CI 95%: 1.4–3.4), p < 0.004, for ε4 versus ε3 and χ ² = 5.7; OR 2.7 (CI 95%: 1.1–6.5), p > 0.01, for ε4 versus ε2. A significant association of the ε4 allele, especially the E3/E4 genotype, with myocardial infarction was observed.     

Lipid class composition of membrane and raft fractions from brains of individuals with Alzheimer's disease

Perturbation of the homeostasis of brain membrane lipids has been implicated in the pathomechanism of Alzheimer's disease (AD). The ε4 allele of the apolipoprotein E gene (APOE) confers an increased risk, in a dosage-dependent manner, for brain amyloid-β accumulation and the development of sporadic AD. An effect of the APOE genotype on brain lipid homeostasis may underlie the AD risk associated with the ε4 allele. In this research, we examined an effect of APOE ε4 on the lipid class composition of crude membranes and raft-enriched fractions of brains. We applied enzymatic reaction-based methods for the quantification of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidic acid, and sphingomyelin. Our results indicate that brain lipid class composition was neither significantly altered in AD subjects nor affected by the presence of the APOE ε4 allele.     

Polymorphisms of the apolipoprotein B and E genes and their relationship to plasma lipid variables in healthy Chinese men

In this study we have analysed the apolipoprotein (Apo) E polymorphism and polymorphisms of the ApoB gene, including the ApoB/Xba I and ApoB/4311 diallelic polymorphisms and a hypervariable region (HVR) situated in the 3 region of the gene (ApoB/3HVR), in a sample of healthy male subjects from Taiyuan (northern People's Republic of China). In comparison to Caucasian populations, in the Chinese sample, the Xba I2 allele (presence of cutting site; frequency 6.1%; and 95% confidence interval, 3.3–8.9) and the long HVR alleles (9.4%; 6.0–12.8) were rare, whereas the ApoB/4311 (Ser) allele (70.8%; 65.4–76.2) and the 34-repeat allele of the HVR (HVR34; 62.4%; 56.8–68.0) were frequent. In subjects having none, one, or two HVR34 alleles, the mean levels of plasma triglycerides were 2.32±1.44 (SD), 1.45+0.74, and 1.75±1.07 g/l, respectively (P < 0.007). Similar trends were observed for very low density lipoprotein (VLDL) cholesterol, LpE:B, and LpCIII:B. The frequencies of the ApoE alleles were similar to those reported in other populations of Asian origin; E2 (7.4%; 4.2–10.6), E3 (84.4%; 80.2–88.6), and E4 (8.2%; 5.0–11.4). Individuals carrying the E2 allele had a lower mean level of ApoB than E33 individuals: 0.87±0.16 and 1.00±0.22 g/l, respectively (P < 0.007). Individuals carrying the E4 allele had higher levels of ApoE than E33 individuals: 0.140±0.084 and 0.094±0.052 g/l, respectively (P < 0.004); similar trends were observed for VLDL cholesterol, triglycerides, LpE:B, and LpCIII:B. The ApoB/ HVR34 and ApoE/E4 polymorphisms accounted for 10% to 15% of the variability of the plasma levels of VLDL cholesterol, ApoE, triglycerides, LpE:B, and LpCIII:B. Several lipid variables appeared to be favourably affected by specific forms of ApoB and ApoE that are particularly frequent in this Chinese population.     

Association of CELSR2, APOB100, ABCG5/8, LDLR,and APOE polymorphisms and their genetic risks with lipids among the Thai subjects

BackgroundHypercholesterolemia is a common cardiovascular risk factor. The aim of this study was to investigate the association of CELSR2 (rs629301), APOB100 (rs1367117), ABCG5/8 (rs6544713), LDLR (rs6511720), and APOE (rs429358, rs7412) polymorphisms, and their genetic risk scores with lipids among Thai subjects.MethodsA total of 459 study subjects (184 males, and 275 females) were enrolled. Blood pressure, serum lipids, and fasting blood sugar were measured. CELSR2 (rs629301), APOB100 (rs1367117), ABCG5/8 (rs6544713), and LDLR (rs6511720) polymorphisms were analyzed using PCR-HRM. APOE (rs429358, rs7412) polymorphism was analyzed using PCR-RFLP.ResultsTotal cholesterol (TC) levels were significantly higher in APOB100 AA genotype compared with GG, or AA + AG genotypes in total subjects. In addition, significantly higher concentrations of TC and low density lipoprotein cholesterol (LDL-C) were observed in APOE4 carriers compared to APOE2 carriers in total subjects, males, and females. The significantly higher concentrations of TC were observed in APOE4 carriers compared to APOE3 carriers in females. Moreover, the concentrations of TC, and LDL-C were significantly increased with genetic risk scores of APOB100, and APOE polymorphisms in total subjects, and females. There was no association between CELSR2 (rs629301), ABCG5/8 (rs6544713), and LDLR (rs6511720) polymorphisms and serum lipids.ConclusionAPOB100 (rs1367117), and APOE (rs429358, rs7412) but not CELSR2 (rs629301), ABCG5/8 (rs6544713), and LDLR (rs6511720) polymorphisms were associated with serum lipids. The cumulative risk alleles of APOB100 (rs1367117), and APOE (rs429358, rs7412) polymorphisms could enhance the elevated concentrations of TC, and LDL-C, and they may be used to predict severity of hypercholesterolemia among Thai subjects.     

Analysis of the association of allelic variants of apolypoprotein E and interleukin 1 beta genes with multiple sclerosis in ethnic Tatars

Multiple sclerosis (MS) is a multifactorial disease of the central nervous system. The apolipoprotein E (APOE) and interleukin 1 β (IL1B) genes are considered to be candidate genes of MS. The aim of the study was to examine the hypothesis of the importance of APOE and IL1B gene polymorphisms in MS development in ethnic Tatars. DNA samples isolated by phenol-chloroform extraction from peripheral blood of 383 ethnic Tatars (120 MS patients and 263 healthy donors) were studied. 112C/R and 158R/C APOE gene polymorphisms as well as ?511T/C IL1B gene polymorphism were analyzed by polymerase chain reaction (PCR) followed by PCR product digestion by endonuclease. Odds ratio (OR) values were used for evaluation of the relative risk of alleles and(or) genotype combinations. It has been shown that APOE*2/*3 genotype is associated with low risk of the disease development (OR = 0.20) in women. A combined effect of APOE and IL1B allelic variants has been discovered indicating the increased risk of the disease development in the carriers of APOE*4 and IL1B*T/*T alleles (OR = 4.76).     

Apolipoprotein E genotype and LRP1 polymorphisms in patients with different clinical types of metachromatic leukodystrophy

Metachromatic leukodystrophy (MLD) is a severe, neurodegenerative, metabolic disease which is caused by deficient activity of arylsulfatase A (ARSA). Sulfatides and other substrates of ARSA are stored in central and peripheral nervous systems, and in some other organs. Accumulated sulfatides are especially toxic to oligodendrocytes and Schwann cells leading to progressive demyelination. The kind of apolipoprotein E (apoE) isoform is of essential significance for the modulation of sulfatide quantity in the brain as apoE4 contains more sulfatides than apoE3. Taking into consideration the fact that apoE4 leads to the loss of sulfatides in CSF of Alzheimer's disease patients, we examined if apoE isoforms display any impact on clinical outcome in patients with different forms of MLD in whom sulfatides accumulate. The significant association of age at the onset of MLD symptoms with APOE ε2/ε3/ε4 and LRP1 c.766C>T polymorphisms was shown in multivariate stepwise regression analysis, in which other factors known to affect age at onset of the disease, i.e. clinical type of MLD, family connection of the patient and sex were also analyzed. As expected, the clinical type of MLD explained about 80% of the variance of the dependent variable. The impact of both polymorphisms on age of onset of the disease was considerably lower: 2.0% in the case of APOE polymorphism and 1.0% in the case of LRP1 polymorphism. Thus, the clinical outcome in MLD patients is related principally to the genotype of the ARSA gene, while the polymorphisms in the APOE and LRP1 genes are only slightly modifying factors.     

Serum paraoxonase level and paraoxonase polymorphism in patients with acromegaly

Background: Acromegalic patients have increased cardiometabolic risk factors due to an elevation of growth hormone (GH) levels. Human serum paraoxonase (PON), a high-density lipoprotein (HDL)-related enzyme, is one of the major bioscavengers and decreases the oxidation of low-density lipoprotein (LDL), a key regulator in the pathogenesis of atherosclerosis. In this study, we investigated a potential relationship between serum PON levels or PON polymorphisms and acromegaly.

Methods: A total of 48 acromegalic patients and 44 healthy controls were included in this study. Serum GH levels, insulin-like growth factor-1 levels and lipid profiles were measured. Serum PON levels, as well as PON 1 L55M and Q192R gene polymorphisms, were examined.

Results: No significant differences were found in terms of age, gender, presence of diabetes, serum LDL cholesterol (LDL-C), HDL-C, or triglyceride levels between the case and control groups (P?>?0.05). A statistically significant difference was found in serum PON levels between the cases and controls (P?=?0.007). The median serum PON level was 101?±?63.36?U/l in the case group and 63?±?60.50?U/l in the control group. There was a significant correlation between serum PON levels and IGF-1 levels (P?=?0.004, r?=?0.319); however, no significant differences were found in PON1 L55M and PON Q192R polymorphisms between the patients and controls (P?=?0.607 and P?=?0.308, respectively). In addition, no significant differences were found in serum PON levels in acromegalic patients who were and were not in remission (P?=?0.385), nor between those with PON1 L55M and Q192R polymorphisms (P?=?0.161 and P?=?0.336, respectively).

Conclusions: Elevated serum PON levels were detected in acromegalic patients, independently of their remission status. This suggests protective effects for cardiometabolic risk parameters.     

Obesity Modulates the Association among APOE Genotype,Insulin, and Glucose in Men

Objective: Obesity, insulin resistance, and apolipoprotein E (APOE) genotype have all been associated with coronary heart disease. We examined the interaction between obesity and APOE genotype in determining fasting insulin and glucose levels. Research Methods and Procedures: From 1991 to 1995, 3799 subjects underwent a clinical examination and fasting insulin and glucose measurement. APOE genotypes were determined on 3500 participants. Participants taking oral hypoglycemic drugs or insulin preparations or with the rare APOE2/4 genotype were excluded. Finally, 2929 individuals were included in the present analysis. Results: In men, we observed a statistically significant interaction between obesity and APOE genotype on insulin and glucose level (p = 0.003 and 0.008, respectively). Obese men with the APOE4 genotype presented with higher levels of insulin and glucose than obese men in the other genotype groups. No association between genotype and insulin or glucose in nonobese men was observed. Obesity was associated with higher insulin levels in the three APOE genotypes groups, whereas obesity was directly associated with glucose in those with the APOE4 genotype. In women, the effect of interaction between APOE genotype and obesity on fasting insulin and glucose was not statistically significant. Obesity was associated with higher levels of fasting insulin and glucose. APOE genotype was not associated with insulin or glucose. Discussion: Obesity modulates the association between the APOE genotype and fasting insulin and glucose levels in men. Although weight control is important in all people, it may be especially important in APOE4 men to modify potentially elevated fasting insulin and glucose levels.     

Genetic association study on in and around the APOE in late-onset Alzheimer disease in Japanese

The ?4 allele of APOE is a well-characterized genetic risk factor for late-onset Alzheimer disease (LOAD). Nevertheless, using high-density single nucleotide polymorphisms (SNPs), there have only been a few studies involving genetic association and linkage disequilibrium (LD) analyses of in and around the APOE. Here, we report fine mapping of a genomic region (about 200 kb) including the APOE in Japanese using 260 SNPs (mean intermaker distance, 0.77 kb). A case-control study demonstrated that 36 of these SNPs exhibited significance after adjustment for multiple testing. These SNPs are located in a genomic region including four genes, PVRL2, TOMM40, APOE and APOC1. Recombination rate estimation revealed that the associated region is firmly sandwiched between two recombination hotspots. Strong LD between these SNPs was observed (mean |D′| = 0.914). These data suggest that the three genes other than APOE, i.e. PVRL2, TOMM40 and APOC1, could also yield a predisposition to LOAD.     

Infectivity of Hepatitis C Virus Is Influenced by Association with Apolipoprotein E Isoforms

Hepatitis C virus (HCV) is a causative agent of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. HCV in circulating blood associates with lipoproteins such as very low density lipoprotein (VLDL) and low-density lipoprotein (LDL). Although these associations suggest that lipoproteins are important for HCV infectivity, the roles of lipoproteins in HCV production and infectivity are not fully understood. To clarify the roles of lipoprotein in the HCV life cycle, we analyzed the effect of apolipoprotein E (ApoE), a component of lipoprotein, on virus production and infectivity. The production of infectious HCV was significantly reduced by the knockdown of ApoE. When an ApoE mutant that fails to be secreted into the culture medium was used, the amount of infectious HCV in the culture medium was dramatically reduced; the infectious HCV accumulated inside these cells, suggesting that infectious HCV must associate with ApoE prior to virus release. We performed rescue experiments in which ApoE isoforms were ectopically expressed in cells depleted of endogenous ApoE. The ectopic expression of the ApoE2 isoform, which has low affinity for the LDL receptor (LDLR), resulted in poor recovery of infectious HCV, whereas the expression of other isoforms, ApoE3 and ApoE4, rescued the production of infectious virus, raising it to an almost normal level. Furthermore, we found that the infectivity of HCV required both the LDLR and scavenger receptor class B, member I (SR-BI), ligands for ApoE. These findings indicate that ApoE is an essential apolipoprotein for HCV infectivity.Hepatitis C virus (HCV) infection is a major global health problem. More than 170 million people worldwide are infected with HCV. HCV causes chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (18). A member of the family Flaviviridae, HCV has a positive-sense, single-stranded RNA genome that is packaged into an enveloped viral particle. The genome encodes a large precursor polyprotein, which is cleaved by host and viral proteases to generate at least 10 functional viral proteins: core, envelope protein 1 (E1), E2, p7, nonstructural protein 2 (NS2), NS3, NS4A, NS4B, NS5A, and NS5B (12, 13). Core associates with the lipid droplet (LD). The role of this association remained elusive until robust HCV replication systems became available (32). We previously showed that the LD is an important organelle for HCV production (23). In hepatocytes, the LD is physiologically important as a lipid source for the production of lipoproteins such as very low density lipoprotein (VLDL) (11). VLDL is synthesized in the liver as a triglyceride/cholesterol ester-rich particle (diameter, 30 to 100 nm) surrounded by apolipoproteins such as apolipoprotein B100 (abbreviated as ApoB throughout), ApoC''s, and ApoE. VLDL is released into blood vessels to be delivered as a lipid source to peripheral cells, and it is also readsorbed by liver cells after processing (5).HCV particles circulating in the blood of HCV carriers associate with lipoproteins, such as low-density lipoprotein (LDL), VLDL, and chylomicrons; thus, these are termed lipo-viro particles (LVPs) (1, 26). Purified LVPs from circulating blood contain triglyceride, ApoB, ApoB48, ApoCII, ApoCIII, ApoE, and virus components such as HCV RNA and core (8), indicating that the LVP has dual viral and lipoprotein characteristics. The HCVcc strain, which contains a chimeric HCV-2a genome with a structural region from HCV-J6 and nonstructural/noncoding regions from an infectious JFH1 virus, can establish long-term infection in chimpanzees. Viruses recovered from the chimpanzee contain infectious virus particles with a slightly low density, suggesting that an in vivo association with low-density factors influences infectivity (19). However, the role of a lipoprotein-like component of LVPs in virus replication is not clear. Moreover, the mechanism by which LVPs are generated during HCV production is unknown.When HCV-producing cells are treated with an inhibitor of microsomal triglyceride transfer protein (MTP) or with ApoB-specific small interfering RNA (siRNA), the production of HCV particles is suppressed (10, 14, 25). Therefore, lipoprotein biosynthesis appears to play an important role in the production of infectious HCV and its egress from infected cells. ApoB, ApoC1, and ApoE associate with infectious virus particles in the HCVcc infection/replication system (4, 6, 15, 22, 27). Furthermore, ApoE depletion suppresses the production of infectious HCV (4, 6, 15, 27). These reports strongly suggest the importance of lipoprotein function to the HCV life cycle. However, the precise roles of lipoproteins and apolipoproteins in virus production and infectivity are not fully understood.We analyzed the production of HCV from cells in which apolipoprotein production was knocked down with siRNA. We found that ApoE is required for the infectivity of HCV, a finding consistent with other reports (4, 6, 15). ApoE is a polymorphic protein with three major isoforms: ApoE2, ApoE3, and ApoE4. The three isoforms differ by amino acid substitutions at one or two sites (residues 130 and 176) on the 317-amino-acid chain of the ApoE molecule. The polymorphism of ApoE influences its multiple functions due to isoform-dependent differences in receptor-binding activity and lipoprotein association preference. For example, ApoE2 has drastically lower LDL receptor (LDLR) binding activity than ApoE3 and ApoE4 (7). In the present study, we investigated the role of ApoE isoforms in virus production and infectivity.(Part of this study was presented at the 16th International Symposium on Hepatitis C Virus and Related Viruses, Nice, France, 3 to 7 October 2009.)     

Associations between APOE Genotypes and Disease Susceptibility,Joint Damage and Lipid Levels in Patients with Rheumatoid Arthritis

Objective

Apolipoprotein E (APOE) genotypes are associated with cardiovascular disease (CVD) and lipid levels. In rheumatoid arthritis (RA), an association has been found with disease activity. We examined the associations between APOE genotypes and disease susceptibility and markers of disease severity in RA, including radiographic joint damage, inflammatory markers, lipid levels and cardiovascular markers.

Method

A Norwegian cohort of 945 RA patients and 988 controls were genotyped for two APOE polymorphisms. We examined longitudinal associations between APOE genotypes and C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) as well as hand radiographs (van der Heijde Sharp Score(SHS)) in 207 patients with 10 year longitudinal data. Lipid levels, cardiovascular markers and history of CVD were compared across genotypes in a cross sectional study of 136 patients. Longitudinal radiological data of cohorts from Lund and Leiden were available for replication. (N = 935, with 4799 radiographs).

Results

In the Norwegian cohort, associations between APOE genotypes and total cholesterol (TC) and low-density lipoproteins (LDL) were observed (ε2<ε3/ε3<ε4, p = 0.03 and p = 0.02, respectively). No association was present for acute phase reactant or CVD markers, but a longitudinal linear association between APOE genotypes and radiographic joint damage was observed (p = 0.007). No association between APOE genotypes and the severity of joint destruction was observed in the Lund and Leiden cohorts, and a meta- analysis combining all data was negative.

Conclusion

APOE genotypes are associated with lipid levels in patients with RA, and may contribute to dyslipidemia in some patients. APOE genotypes are not consistently associated with markers of inflammation or joint destruction in RA.     

APOE genotype and cardio-respiratory fitness interact to determine adiposity in 8-year-old children from the Tasmanian Infant Health Survey

APOE plays a well established role in lipid metabolism. Animal model evidence suggests APOE may also be associated with adiposity, but this has not been thoroughly investigated in humans. We measured adiposity (BMI, truncal fat mass, waist circumference), physical activity (PA), cardiorespiratory fitness and APOE genotype (E2, E3, E4) in 292 8-year-old children from the Tasmanian Infant Health Survey (TIHS), an Australian population-based prospective birth cohort. Our aims were to examine the association of APOE with child adiposity, and to examine the interplay between this association and other measured factors. We found that APOE was associated with child lipid profiles. APOE was also associated with child adiposity measures. The association was E4 allele-specific, with adiposity lower in the E4-containing group (BMI: Mean difference -0.90 kg/m²; 95% confidence intervals (CI) -1.51, -0.28; p = 0.004). The association of APOE4 with lower BMI differed by fitness status (difference in effect p = 0.002), and was more evident among the less fit (mean difference -1.78 kg/m²; 95% CI -2.74, -0.83; p<0.001). Additionally, associations between BMI and lipids were only apparent in those of lower fitness who did not carry APOE4. Similar overall findings were observed when truncal fat mass and waist circumference were used as alternative adiposity measures. APOE4 and cardiorespitatory fitness could interact to influence child adiposity. In studies addressing the genetic determinants of childhood obesity, the context of child fitness should also be taken into account.     

Serum vitamins A and E as modifiers of lipid trait genetics in the National Health and Nutrition Examination Surveys as part of the Population Architecture using Genomics and Epidemiology (PAGE) study

Both environmental and genetic factors impact lipid traits. Environmental modifiers of known genotype–phenotype associations may account for some of the “missing heritability” of these traits. To identify such modifiers, we genotyped 23 lipid-associated variants identified previously through genome-wide association studies (GWAS) in 2,435 non-Hispanic white, 1,407 non-Hispanic black, and 1,734 Mexican-American samples collected for the National Health and Nutrition Examination Surveys (NHANES). Along with lipid levels, NHANES collected environmental variables, including fat-soluble macronutrient serum levels of vitamin A and E levels. As part of the Population Architecture using Genomics and Epidemiology (PAGE) study, we modeled gene–environment interactions between vitamin A or vitamin E and 23 variants previously associated with high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels. We identified three SNP?×?vitamin A and six SNP?×?vitamin E interactions at a significance threshold of p?<?2.2?×?10^?3. The most significant interaction was APOB rs693?×?vitamin E (p?=?8.9?×?10^?7) for LDL-C levels among Mexican-Americans. The nine significant interaction models individually explained 0.35–1.61?% of the variation in any one of the lipid traits. Our results suggest that vitamins A and E may modify known genotype–phenotype associations; however, these interactions account for only a fraction of the overall variability observed for HDL-C, LDL-C, and TG levels in the general population.     

Independent associations of TOMM40 and APOE variants with body mass index

The TOMM40‐APOE variants are known for their strong, antagonistic associations with Alzheimer's disease and body weight. While a stronger role of the APOE than TOMM40 variants in Alzheimer's disease was suggested, comparative contribution of the TOMM40‐APOE variants in the regulation of body weight remains elusive. We examined additive effects of rs2075650 and rs157580 TOMM40 variants and rs429358 and rs7412 APOE variants coding the ε2/ε3/ε4 polymorphism on body mass index (BMI) in age‐aggregated and age‐stratified cohort‐specific and cohort‐pooled analysis of 27,863 Caucasians aged 20–100 years from seven longitudinal studies. Minor alleles of rs2075650, rs429358, and rs7412 were individually associated with BMI (β = ?1.29, p = 3.97 × 10^?9; β = ?1.38, p = 2.78 × 10^?10; and β = 0.58, p = 3.04 × 10^?2, respectively). Conditional analysis with rs2075650 and rs429358 identified independent BMI‐lowering associations for minor alleles (β = ?0.63, p = 3.99 × 10^?2 and β = ?0.94, p = 2.17 × 10^?3, respectively). Polygenic mega‐analysis identified additive effects of the rs2075650 and rs429358 heterozygotes (β = ?1.68, p = 3.00 × 10^?9), and the strongest BMI‐lowering association for the rs2075650 heterozygous and rs429358 minor allele homozygous carriers (β = ?4.11, p = 2.78 × 10^?3). Conditional analysis with four polymorphisms identified independent BMI‐lowering (rs2075650, rs157580, and rs429358) and BMI‐increasing (rs7412) associations of heterozygous genotypes with BMI. Age‐stratified conditional analysis revealed well‐powered support for a differential and independent association of the rs429358 heterozygote with BMI in younger and older individuals, β = 0.58, 95% confidence interval (CI) = ?1.18, 2.35, p = 5.18 × 10^?1 for 3,068 individuals aged ≤30 years and β = ?4.28, CI = ?5.65, ?2.92, p = 7.71 × 10^?10 for 6,052 individuals aged >80 years. TOMM40 and APOE variants are independently and additively associated with BMI. The APOE ε4‐coding rs429358 polymorphism is associated with BMI in older individuals but not in younger individuals.     

Association of APOE, GCPII and MMP9 polymorphisms with common diseases and lipid levels in an older adult/elderly cohort

Background and aims

The characterization of candidate gene polymorphisms in elderly populations is an important tool for the identification of risk factors for age-related diseases and conditions. We aimed to genotype the APOE polymorphisms (rs429358 and rs7412), rs61886492 (1561C>T) and rs202720 of GCPII gene and rs3918242 (− 1562C>T) of MMP9 gene in an older-adult/elderly cohort from Cuiabá city, Mato Grosso Brazil as well as to characterize risk factors for morbidities and conditions affecting this cohort.

Methods

The studied population consisted of 570 subjects from Cuiabá city, Brazil, who were subjected to clinical interviews and blood collection for laboratory examinations and DNA extraction. Restriction Fragment Length Polymorphism Polymerase Chain Reaction (RFLP-PCR), sequence-specific primer PCR (SSP-PCR) and TaqMan® allelic discrimination assay were used for genotyping.

Results

The frequencies of APOE ε2 and ε4 were 6.6% and 14.8%, respectively, and the frequencies of GCPII rs61886492 T allele, GCPII rs202720 C allele and MMP9 rs3918242 T allele were, respectively, 3.0%, 26.6% and 10.1%. Significant associations between APOE ε2 allele with lower total cholesterol and LDL-cholesterol were found. In addition, MMP9 rs3918242 T allele was associated with higher LDL-cholesterol levels, suggesting a link between lipid metabolism alteration and cardiovascular disease.

Conclusions

The present findings contributed to characterize risk factors specific for the studied population and to better understand the molecular physiopathology of common morbidities and conditions affecting older-adult/elderly people.     

Allelic variation within the major APOE CpG island affects its methylation in the brain of targeted replacement mice expressing human APOE

• •The number of cytosine-phosphate-guanine (CpG) sites differs due to sequence variation in the human apolipoprotein E (APOE) gene.
• •APOE DNA methylation is allele-dependently altered corresponding to the total number of CpG pairs in the brain of APOE targeted replacement mice (APOE εpsilon 4 > εpsilon 3 > εpsilon 2).
• •Binding of the methyl-CpG binding protein 2 to genomic APOE was in trend less pronounced in the brain of APOE4 mice.