Impact Of apoE Polymorphism Research Articles

Apolipoprotein E Polymorphism and Oxidative Stress in Human Peripheral Blood Cells: Can Physical Activity Reactivate the Proteasome System through Epigenetic Mechanisms?

Alzheimer's disease (AD) is characterized by proteasome activity impairment, oxidative stress, and epigenetic changes, resulting in β-amyloid (Aβ) production/degradation imbalance. Apolipoprotein E (ApoE) is implicated in Aβ clearance, and particularly, the ApoE ε4 isoform predisposes to AD development. Regular physical activity is known to reduce AD progression. However, the impact of ApoE polymorphism and physical exercise on Aβ production and proteasome system activity has never been investigated in human peripheral blood cells, particularly in erythrocytes, an emerging peripheral model used to study biochemical alteration. Therefore, the influence of ApoE polymorphism on the antioxidant defences, amyloid accumulation, and proteasome activity was here evaluated in human peripheral blood cells depending on physical activity, to assess putative peripheral biomarkers for AD and candidate targets that could be modulated by lifestyle. Healthy subjects were enrolled and classified based on the ApoE polymorphism (by the restriction fragment length polymorphism technique) and physical activity level (Borg scale) and grouped into ApoE ε4/non-ε4 carriers and active/non-active subjects. The plasma antioxidant capability (AOC), the erythrocyte Aβ production/accumulation, and the nuclear factor erythroid 2-related factor 2 (Nrf2) mediated proteasome functionality were evaluated in all groups by the chromatographic and immunoenzymatic assay, respectively. Moreover, epigenetic mechanisms were investigated considering the expression of histone deacetylase 6, employing a competitive ELISA, and the modulation of two key miRNAs (miR-153-3p and miR-195-5p), through the miRNeasy Serum/Plasma Mini Kit. ApoE ε4 subjects showed a reduction in plasma AOC and an increase in the Nrf2 blocker, miR-153-3p, contributing to an enhancement of the erythrocyte concentration of Aβ. Physical exercise increased plasma AOC and reduced the amount of Aβ and its precursor, involving a reduced miR-153-3p expression and a miR-195-5p enhancement. Our data highlight the impact of the ApoE genotype on the amyloidogenic pathway and the proteasome system, suggesting the positive impact of physical exercise, also through epigenetic mechanisms.

Impact of ApoE Polymorphism and Physical Activity on Plasma Antioxidant Capability and Erythrocyte Membranes.

The allele epsilon 4 (ε4) of apolipoprotein E (ApoE) is the strongest genetic risk factor for Alzheimer’s disease (AD). ApoE protein plays a pivotal role in the synthesis and metabolism of amyloid beta (Aβ), the major component of the extracellular plaques that constitute AD pathological hallmarks. Regular exercise is an important preventive/therapeutic tool in aging and AD. Nevertheless, the impact of physical exercise on the well-being of erythrocytes, a good model of oxidative stress and neurodegenerative processes, remains to be investigated, particularly depending on ApoE polymorphism. Herein, we evaluate the oxidative status, Aβ levels, and the membrane’s composition of erythrocytes in a cohort of human subjects. In our hands, the plasma antioxidant capability (AOC), erythrocytes membrane fluidity, and the amount of phosphatidylcholine (PC) were demonstrated to be significantly decreased in the ApoE ε4 genotype and non-active subjects. In contrast, erythrocyte Aβ content and lipid peroxidation increased in ε4 carriers. Regular physical exercise was associated with an increased plasma AOC and membrane fluidity, as well as to a reduced amount of erythrocytes Aβ. Altogether, these data highlight the influence of the ApoE genotype on erythrocytes’ well-being and confirm the positive impact of regular physical exercise.

Impact of Apolipoprotein E gene polymorphism during normal and pathological conditions of the brain across the lifespan.

The central nervous system (CNS) is the cellular substrate for the integration of complex, dynamic, constant, and simultaneous interactions among endogenous and exogenous stimuli across the entire human lifespan. Numerous studies on aging-related brain diseases show that some genes identified as risk factors for some of the most common neurodegenerative diseases - such as the allele 4 of APOE gene (APOE4) for Alzheimer’s disease (AD) - have a much earlier neuro-anatomical and neuro-physiological impact. The impact of APOE polymorphism appears in fact to start as early as youth and early-adult life. Intriguingly, though, those same genes associated with aging-related brain diseases seem to influence different aspects of the brain functioning much earlier actually, that is, even from the neonatal periods and earlier. The APOE4, an allele classically associated with later-life neurodegenerative disorders as AD, seems in fact to exert a series of very early effects on phenomena of neuroplasticity and synaptogenesis that begin from the earliest periods of life such as the fetal ones.We reviewed some of the findings supporting the hypothesis that APOE polymorphism is an early modifier of various neurobiological aspects across the entire human lifespan - from the in-utero to the centenarian life - during both normal and pathological conditions of the brain.

Apolipoprotein E polymorphism is associated with both number of diseased vessels and extent of coronary artery disease in Czech patients with CAD

The impact of ApoE polymorphism on angiographic parameters was assessed in patients referred for coronary angiography. Elective coronary angiography was performed in 671 subjects (525 men, 146 women, mean age 60 ± 10 years) with symptoms of ischemic heart disease. The patients were divided into: no CAD group (smooth coronary vessels, n=83), one-vessel (n=155), two-vessel (n=170) and three-vessel disease (n=196). Patients with stenoses 0-50% were excluded. Within patients with CAD, we evaluated overall extent of CAD measured by the number of stenotic segments according to AHA (1 segment vs. 2-3 vs. ≥4), and the severity of the most serious stenosis (in percent). ApoE genotype was determined using real-time PCR. The frequency of ε2/ε3 genotype (n=56) was lower in the three-vessel disease group compared to one-vessel disease (OR=0.25, P=0.0019), two-vessel disease (OR=0.31, P=0.0114) or no CAD group (OR=0.24, P=0.0057). Frequency of ε2/ε3 decreased with the number of affected segments (1 vs. ≥4: OR=0.35, P=0.0143). The ε3/ε4+ε4/ε4 genotypes (n=123) were more frequent in CAD patients altogether compared with no CAD group (OR=2.30, P=0.019), while no impact of the ε4 allele on angiographic parameters within the CAD patients was detected. In ε2/ε3 carriers with CAD, lower LDL-cholesterol, total cholesterol and lower use of lipid-lowering drugs were observed. The results show predominantly focal form of CAD in patients with ε2/ε3 genotype. Lower LDL-cholesterol and total cholesterol may play the key role, although other contributing factors are discussed.

ApoE and cholesterol in schizophrenia and bipolar disorder: comparison of grey and white matter and relation with APOE genotype

Apolipoprotein E (apoE) and cholesterol play a critical role in synapse and myelin maintenance and integrity and are thus appealing candidates in the pathogenesis of schizophrenia and bipolar disorder. To explore the role of these 2 molecules, we quantified cholesterol and apoE levels in prefrontal grey and white matter in patients with schizophrenia, bipolar disorder and healthy controls. Furthermore, we investigated the relations between apoE and cholesterol levels and the APOE genotype. We obtained dorsolateral prefrontal grey and white matter from the Stanley Medical Research Institute Brain Collection (schizophrenia n = 35, bipolar disorder n = 35 and controls n = 35). Cholesterol levels were quantified using high-pressure liquid chromatography, whereas apoE was measured by enzyme-linked immunosorbent assay. We found no significant differences in cholesterol or apoE levels among the groups. ApoE levels were higher in grey matter than in white matter in all groups; conversely, levels of cholesterol were higher in white matter than in grey matter. We observed a significant inverse correlation between apoE and cholesterol levels in both grey and white matter. Furthermore, in grey matter, apoE levels were significantly higher in APOE ε2 carriers compared with APOE ε3 or APOE ε4 carriers, with cholesterol levels following the opposite trend. LIMITATIONS of our study include our inability to control for potential confounding variables and the small numbers of APOE ε2 and ε4 carriers in each group. Although large amounts of cholesterol are present in white matter, apoE expression is limited. The APOE genotype may play a role in the regulation of both cholesterol and apoE levels in grey matter. The impact of APOE polymorphisms on lipid homeostasis in people with psychiatric disorders warrants further investigation.

Apolipoprotein E Polymorphism and Age at Onset of Alzheimer’s Disease in a Quadriethnic Sample

Background: The relationship between the apolipoprotein E (ApoE) genotype and the risk for developing Alzheimer’s disease (AD) or age at onset of AD is relatively well established in Caucasians, but less established in other ethnicities. We examined the association between the ApoE genotype and age at onset of AD in a quadriethnic group of community-dwelling AD patients. Methods: AD patients were evaluated at 2 university-based outpatient memory disorder clinics. The ethnic distribution was as follows: Caucasians (n = 1,083), Hispanics (n = 55), African Americans (n = 84) and Koreans (n = 87). All were diagnosed with probable AD according to NINCDS-ADRDA diagnostic criteria. Results: After adjusting for ethnicity, the Ε4 allele was significantly associated with earlier age at onset (p < 0.0001) for the combined group. Within ethnic groups, the effect of Apo Ε4 on age at onset was significant in Caucasians (p < 0.0001) and African Americans (p < 0.05), but nonsignificant in Koreans (p = 0.43) and in the smaller Hispanic (p = 0.07) group. Conclusions: The association between Apo Ε4 and younger age at onset was significant in Caucasians and African Americans, where the Ε4 allele was also most frequent. This study suggests that the impact of ApoE polymorphism on age at onset of AD may be different among distinct ethnic groups.

Apolipoprotein A5: An Emerging Paradigm For Genetic Associations And Interactions In Lipoprotein And Cardiovascular Research

For decades, apolipoprotein (Apo)E has reigned as the undisputed leader of lipoprotein genetics [1]. For many years, the impact of ApoE polymorphisms on plasma low-density lipoprotein (LDL)-cholesterol concentrations has been demonstrated in a reproducible fashion [2,3]. Moreover, several population studies have also shown how this genetic variability could be used to predict disease risk above and beyond traditional risk factors [4]. The interest in ApoE polymorphisms increased further when this major regulator of lipid metabolism was first implicated in the risk for neurological disorders and then for all types of chronic disorders (i.e., cancer and osteoporosis). Moreover, consistent with the knowledge that, for the population at large, the individual cardiovascular disease (CVD) risk is neither 100% genetic or environmental, ApoE has repeatedly shown significant gene–environment interactions modulating its association with plasma lipid parameters as well as CVD risk [5]. Thus, the ApoE gene has been considered as the paradigm of genetic associations and interactions within the lipid and CVD fields.

Protective effect of apolipoprotein E2 on coronary artery disease in African Americans is mediated through lipoprotein cholesterol

We studied the relationship of apolipoprotein E (apoE) isoforms and coronary artery disease (CAD) in 224 African Americans and 326 Caucasians undergoing diagnostic coronary angiography. The presence of CAD was defined as >50% stenosis in at least one artery. ApoE allele frequencies were 0.12, 0.62, and 0.26 for epsilon 2, epsilon 3, and epsilon 4, respectively, in African Americans and 0.08, 0.78, and 0.14 for epsilon 2, epsilon 3, and epsilon 4, respectively, in Caucasians. Among African Americans, CAD was present in 9 of 34 epsilon 2 carriers (26%), significantly smaller (P < 0.05) in proportion compared with 39 of 82 epsilon 3 carriers and 43 of 92 epsilon 4 carriers (48% and 47%, respectively), suggesting a protective effect of the epsilon 2 allele. No such difference was seen in Caucasians. In African Americans but not Caucasians, LDL cholesterol was lower in epsilon 2 carriers than in epsilon 3 and epsilon 4 carriers (106 vs. 127 and 134 mg/dl, respectively; P < 0.005). After adjusting for lipid levels, the association between apoE2 and CAD was no longer significant. Thus, the protective effect of apoE2 seen in African Americans could be explained by a favorable lipid profile in epsilon 2 carriers, whereas in Caucasians, the absence of such a protective effect could be attributable to the lack of effect of apoE2 on the lipid profile.

Apolipoprotein E polymorphism and age of onset for Alzheimer's disease in a bi-ethnic sample

This study examined the association between the Apolipoprotein-E epsilon4 allele (APOE epsilon4) and age of disease onset in a bi-ethnic sample of community dwelling Alzheimer's disease (AD) patients. Cross-sectional study of AD patients evaluated at a University-affiliated outpatient memory disorders clinic. A clinic-based cohort of white non-Hispanic (WNH; n=601) and white Hispanic (WH; n = 359) patients diagnosed with possible or probable AD according to NINCDS-ADRDA diagnostic criteria. Global cognitive functioning of the subjects was evaluated using the Mini-mental State Exam. The age of onset of AD was calculated from the patient's current age minus the reported duration of disease obtained from a knowledgeable family member. A significant relationship was discovered between APOE epsilon4 and age of onset for WNH, with lower ages of onset among patients carrying the epsilon4/epsilon4 and epsilon3/epsilon4 genotypes in relation to patients with the epsilon3/epsilon3 genotype. The results revealed a more modest effect for APOE genotype in the WH cohort, with a lower age of onset witnessed among epsilon4 positive patients (epsilon2/epsilon4, epsilon3/epsilon4 and epsilon4/epsilon4 genotypes) in comparison to epsilon4 negative patients (epsilon2/epsilon2, epsilon2/epsilon3 and epsilon3/epsilon3 genotypes). The association between the epsilon4 allele and earlier age of onset was more pronounced in WNH compared to WH patients, suggesting the impact of APOE polymorphism on clinical phenotype may be different for distinct ethnic groups in the U.S.

Meta-analysis: apolipoprotein E genotypes and risk for coronary heart disease.

Apolipoprotein E (apoE) genotypes play critical roles in lipid metabolism and are believed to influence risk for coronary heart disease (CHD). Despite many population studies, however, the impact of apoE polymorphism on risk for CHD remains uncertain. To qualitatively and quantitatively assess the evidence regarding the relation of apoE polymorphism to CHD risk. All relevant reports and references from original and review papers published from 1966 to January 2004. Predefined criteria were used to identify 48 relevant studies. A summary database that contained variables of study design, study sample and ethnicity, sex, apoE genotypes, CHD end points, plasma lipid levels, and other CHD risk factors was developed. The authors qualitatively evaluated many potential sources of heterogeneity. To quantify the extent of heterogeneity and assess the consistency of apoE-CHD associations, stratified analyses were conducted using the classic random-effects model. To further incorporate uncertainty due to between-study variation, the pooled odds ratios (ORs) and 95% credible intervals (CrIs) were estimated by using a Bayesian hierarchical model. Finally, the robustness of the pooled estimates was tested in multiple sensitivity analyses. Compared with individuals with the epsilon3/3 genotype, carriers of the apoE epsilon4 allele had a 42% higher risk for CHD (OR, 1.42 [95% CrI, 1.26 to 1.61]). The epsilon2 allele had no significant association with CHD risk (OR, 0.98 [CrI, 0.66 to 1.46]). This meta-analysis did not include unpublished data or studies published in languages other than English. Inadequate statistical power, differences in geographic and ethnic background, allele frequency, sex, CHD phenotypes, study design, and potential gene-environment interactions may have contributed to the conflicting results of previous studies. The apoE epsilon4 allele is a significant risk factor for CHD.