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

Alzheimer's Disease and Alzheimer's Disease-Related Dementias in African Americans: Focus on Caregivers

Alzheimer's disease (AD) and Alzheimer's Disease-Related Dementias (ADRD) are chronic illnesses that are highly prevalent in African Americans (AA). AD and ADRD are caused by multiple factors, such as genetic mutations, modifiable and non-modifiable risk factors, and lifestyle. Histopathological, morphological, and cellular studies revealed how multiple cellular changes are implicated in AD and ADRD, including synaptic damage, inflammatory responses, hormonal imbalance, mitochondrial abnormalities, and neuronal loss, in addition to the accumulation of amyloid beta and phosphorylated tau in the brain. The contributions of race, ethnicity, location and socioeconomic status all have a significant impact on the care and support services available to dementia patients. Furthermore, disparities in health care are entangled with social, economic, and environmental variables that perpetuate disadvantages among different groups, particularly African Americans. As such, it remains important to understand how various racial and ethnic groups perceive, access, and experience health care. Considering that the mounting data shows AA may be more susceptible to AD than white people, the demographic transition creates significant hurdles in providing adequate care from family caregivers. Furthermore, there is growing recognition that AD and ADRD pose a significant stress on AA caregivers compared to white people. In this review, we examine the current literature on racial disparities in AD and ADRD, particularly concerning AA caregivers.

Relationship of Apolipoprotein E with Alzheimer's Disease and Other Neurological Disorders: An Updated Review

Alzheimer's disease (AD) and other neurodegenerative diseases, for which there is no effective cure, cause great social burden. Apolipoprotein E (APOE) is an important lipid transporter, which has been shown to have a close relationship with AD and other neurological disorders in an increasing number of studies, suggesting its potential as a therapeutic target. In this review, we summarize the recent advances in clinical and basic research on the role of APOE in the pathogenesis of multiple neurological diseases, with an emphasis on the new associations between APOE and AD, and between APOE and depression. The progress of APOE research in Parkinson's disease (PD) and some other neurological diseases is briefly discussed.

Systems Medicine as a Strategy to Deal with Alzheimer's Disease

The traits of Alzheimer's disease (AD) include amyloid plaques made of Aβ1-40 and Aβ1-42, and neurofibrillary tangles by the hyperphosphorylation of tau protein. AD is a complex disorder that is heterogenous in genetical, neuropathological, and clinical contexts. Current available therapeutics are unable to cure AD. Systems medicine is a strategy by viewing the body as a whole system, taking into account each individual's unique health profile, provide treatment and associated nursing care clinically for the patient, aiming for precision. Since the onset of AD can lead towards cognitive impairment, it is vital to intervene and diagnose early and prevent further progressive loss of neurons. Moreover, as the individual's brain functions are impaired due to neurodegeneration in AD, it is essential to reconstruct the neurons or brain cells to enable normal brain functions. Although there are different subtypes of AD due to varied pathological lesions, in the majority cases of AD, neurodegeneration and severe brain atrophy develop at the chronic stage. Novel approaches including RNA based gene therapy, stem cell based technology, bioprinting technology, synthetic biology for brain tissue reconstruction are researched in recent decades in the hope to decrease neuroinflammation and restore normal brain function in individuals of AD. Systems medicine include the prevention of disease, diagnosis and treatment by viewing the individual's body as a whole system, along with systems medicine based nursing as a strategy against AD that should be researched further.

Longitudinal changes in HDL-cholesterol concentration are associated with different risk factors in primiparous and nulliparous young women: The NHLBI Growth and Health Study (NGHS)

BACKGROUND

Previous studies report that first pregnancy is associated with persistent decreases in HDL-cholesterol (HDL-C) concentrations.

OBJECTIVE

This study evaluated factors associated with declines in HDL-C concentration in parous and nulliparous young women.

METHODS

This study leverages data from African-American and white women from the NHLBI Growth and Health Study. Parity-related changes in lipids, BMI and percent body fat were assessed longitudinally. A subset of primiparous and nulliparous women with paired lipid measurements were analyzed regarding changes in HDL-C concentrations.

RESULTS

Among 870 women in longitudinal analyses, African-American women had higher parity (p<0.0001), with baseline measurements of each parity group being similar. HDL-C concentration decreased significantly and remained lower after the first pregnancy, while BMI and percent body fat increased with increasing parity. In the subset of 401 women, HDL-C concentration decreased among primiparous women (-4.81 ± 0.93 mg/dl), with no overall change in nulliparous (p = 0.003). In both groups, greater HDL-C concentration declines were independently associated with higher initial HDL-C concentration and greater increases in BMI (both p<0.0001). Among primiparous women, younger delivery age (p = 0.0001) and birth control use (p = 0.004) were associated with greater HDL-C concentration decline. Nulliparous white women's HDL-C concentration increased over time, with no change in African-American women (p = 0.008); no racial difference was seen in primiparous women.

CONCLUSION

Persistent decreases in HDL-C concentration were associated with the first pregnancy, and were greater with higher initial HDL-C concentration. Racial differences in HDL-C concentration emerged over time in nulliparous women, but not primiparous women. Potential impacts of these findings on women's long-term cardiometabolic health should be evaluated.

"Association of APOE gene polymorphisms with primary open angle glaucoma in Brazilian patients"

Background: Primary open-angle glaucoma (POAG) is a multifactorial disease that affects 65.5 million people worldwide. In addition to the genetic variants already established as indicators of greater risk for POAG, the apolipoprotein (APOE) gene has been studied in some populations, with controversial results. The aim of this study is to investigate the frequency of the genetic variants of APOE in the Brazilian population, and to evaluate the association between these polymorphisms and the risk of POAG. Methods: APOE variants (rs429358; rs7412) were genotyped in 402 POAG patients and 401 controls. We evaluated the association between APOE genetic variants and the risk for POAG, as well as the correlation between the requirement of glaucoma surgery and the APOE polymorphisms. Results: Among the three APOE gene isoforms, we found a low frequency of APOE alleles ε2 (7.34%) and ε4 (11.76%), but a high frequency of ε3 (80.88%) in our population. When compared to ε3ε3 reference genotype, ε2 allele-carriers (OR = 1.516; p-value = 0.04) and ε2ε3 genotype (OR = 1.655; p-value = 0.02) were associated with a greater risk for POAG. An additive genetic model confirmed the influence of the ε2 allele in the risk of POAG in this sample of the Brazilian population (OR = 1.502; p-value = 0.04). There was no significant association between the analyzed genotypes and the requirement or number of glaucoma surgeries (p > .05). Conclusion: Brazilian individuals carrying the APOEε2 allele may be at an increased risk for the development of POAG.

Association between apolipoprotein E gene polymorphism and the risk of coronary artery disease in Hakka postmenopausal women in southern China

Background

Apolipoprotein E (APOE) is involved in the pathogenesis of atherosclerosis and conveys a higher risk of coronary artery disease (CAD). The aim of the present study was to investigate the possible association between APOE gene polymorphism and the risk of CAD in postmenopausal Hakka women in southern China.

Methods

The APOE genotypes of 653 CAD patients and 646 control participants were determined by the polymerase chain reaction (PCR) and hybridization to a Sinochip.

Results

The prevalence of each APOE genotype differed between CAD patients and control participants (P = 0.011). The E3/E3 genotype was the most common and the E2/E2 genotype was the least common in the study sample. Moreover, the presence of ε4 allele was associated with higher serum concentrations of triglycerides (TG), total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C), and lower concentration of high-density lipoprotein-cholesterol (HDL-C). Multiple logistic regression analysis revealed that participants with ε4 allele have a significantly higher risk of CAD after adjustment for the presence of diabetes mellitus and hypertension, and their serum uric acid, TC, and LDL-C concentrations (adjusted odds ratio (OR) 1.50, 95% confidence interval (CI) 1.10–2.05, P = 0.010).

Conclusions

The present results suggest that APOE polymorphism is associated with a higher risk of CAD in postmenopausal Hakka women in southern China.

Association study between DNA methylation and genetic variation of APOE gene with the risk of coronary artery disease

Coronary artery disease (CAD) is a common health problem with a high rate of disability and death. Dyslipidemia and altered metabolism of Apo-lipoproteins are involved in the CAD pathogenesis. The current study investigated two common polymorphisms (rs429358 and rs7412) and promoter DNA methylation status of APOE in the Iranian CAD patients and control subjects. Two hundred angiographically documented CAD patients and 200 control subjects were included in the study. The APOE polymorphism analysis was done by PCR-RFLP technique and DNA methylation status was evaluated by methylation specific PCR. The assay of lipid levels was conducted using standard colorimetric protocols. Results indicated that the frequency of ε3/ε4 and ε2/ε3 genotypes was significantly more common in CAD group compared with control group. Relative to wild type genotype (ε3/ε3), CAD patients with ε3/ε4 and ε2/ε3 genotypes displayed significantly higher concentration of total-cholesterol and LDL-cholesterol. The frequency of DNA methylation of APOE was similar between the two studied groups. However, the methylation frequency of APOE gene was significantly higher in triple stenotic vessels relative to single stenotic vessels (P=0.032). In conclusion The present study indicated that the rs429358 and rs7412 polymorphisms are significantly risk factors for development and severity of CAD. Also, APOE methylation status may be involved in the severity but not in the development of CAD.

A Validation Study of Vascular Cognitive Impairment Genetics Meta-Analysis Findings in an Independent Collaborative Cohort

Vascular cognitive impairment (VCI), including its severe form, vascular dementia (VaD), is the second most common form of dementia. The genetic etiology of sporadic VCI remains largely unknown. We previously conducted a systematic review and meta-analysis of all published genetic association studies of sporadic VCI prior to 6 July 2012, which demonstrated that APOE (ɛ4, ɛ2) and MTHFR (rs1801133) variants were associated with susceptibility for VCI. De novo genotyping was conducted in a new independent relatively large collaborative European cohort of VaD (nmax = 549) and elderly non-demented samples (nmax = 552). Where available, genotype data derived from Illumina's 610-quad array for 1210 GERAD1 control samples were also included in analyses of genes examined. Associations were tested using the Cochran-Armitage trend test: MTHFR rs1801133 (OR = 1.36, 95% CI 1.16-1.58, p = <0.0001), APOE rs7412 (OR = 0.62, 95% CI 0.42-0.90, p = 0.01), and APOE rs429358 (OR = 1.59, 95% CI 1.17-2.16, p = 0.003). Association was also observed with APOE epsilon alleles; ɛ4 (OR = 1.85, 95% CI 1.35-2.52, p = <0.0001) and ɛ2 (OR = 0.67, 95% CI 0.46-0.98, p = 0.03). Logistic regression and Bonferroni correction in a subgroup of the cohort adjusted for gender, age, and population maintained the association of APOE rs429358 and ɛ4 allele.

Vascular Contributions in Alzheimer's Disease-Related Neuropathological Changes: First Autopsy Evidence from a South Asian Aging Population

BACKGROUND

Evidence from various consortia on vascular contributions has been inconsistent in determining the etiology of sporadic Alzheimer's disease (AD).

OBJECTIVE

To investigate vascular risk factors and cerebrovascular pathologies associated in manifestation of AD-related neuropathological changes of an elderly population.

METHODS

Postmortem brain samples from 76 elderly subjects (≥50 years) were used to study genetic polymorphisms, intracranial atherosclerosis of the circle of Willis (IASCW), and microscopic infarcts in deep white matters. From this cohort, 50 brains (≥60 years) were subjected to neuropathological diagnosis using immunohistopathological techniques.

RESULTS

Besides the association with age, the apolipoprotein E ɛ4 allele was significantly and strongly associated with Thal amyloid-β phases ≥1 [odds ratio (OR) = 6.76, 95% confidence interval (CI) 1.37-33.45] and inversely with Braak neurofibrillary tangle (NFT) stages ≥III (0.02, 0.0-0.47). Illiterates showed a significant positive association for Braak NFT stages ≥IV (14.62, 1.21-176.73) and a significant negative association for microscopic infarcts (0.15, 0.03-0.71) in deep white matters. With respect to cerebrovascular pathologies, cerebral small vessel lesions (white matter hyperintensities and cerebral amyloid angiopathy) showed a higher degree of associations among them and with AD-related neuropathological changes (p < 0.05) compared to large vessel pathology (IASCW), which showed a significant association only with Braak NFT stages ≥I (p = 0.050).

CONCLUSION

These findings suggest that besides age, education, and genetic factors, other vascular risk factors were not associated with AD-related neuropathological changes and urge prompt actions be taken against cerebral small vessel diseases since evidence for effective prevention is still lacking.

Association of APOE gene polymorphism with lipid profile and coronary artery disease in Afro-Caribbeans

OBJECTIVES

Apolipoprotein E gene (APOE) polymorphism is associated with the lipid profile and cardio-vascular disease. However, these relationships vary between ethnic groups. We evaluated, for the first time in an Afro-Caribbean population, the distribution of APOE polymorphisms and their associations with coronary artery disease (CAD), the lipid profile and other cardio-metabolic risk factors.

METHODS

We studied 712 Afro-Caribbean subjects including 220 with documented CAD and 492 healthy subjects. TaqMan assays were performed to genotype rs7412 and rs429358, the two variants that determine the APOE alleles ε2, ε3 and ε4. The association between APOE genotype and the lipid profile was analysed by comparing ε2 carriers, ε3 homozygotes and ε4 carriers.

RESULTS

The frequencies of ε2, ε3 and ε4 in the overall sample were 8%, 70% and 22%, respectively. CAD was not associated with APOE polymorphism. The total cholesterol level was higher in ε4 carriers compared with ε2 carriers: 5.07 vs 4.59 mmol/L (P = 0.016). The LDL-cholesterol level was lower in APOE ε2 carriers compared with ε3 homozygotes and ε4 carriers: 2.65 vs 3.03 and 3.17 mmol/L, respectively (p = 0.002). The total cholesterol/HDL-cholesterol and LDL-cholesterol/HDL-cholesterol ratios were similar in the three allelic groups. APOE polymorphism was not associated with diabetes, hypertension, waist circumference or body mass index.

CONCLUSIONS

Our results indicate that APOE gene polymorphism is associated with the lipid profile but not with CAD in Afro-Caribbean people. This lack of association with CAD may be explained by the low atherogenic profile observed in ε4 carriers, which may warrant further investigation.

Attenuated age-impact on systemic inflammatory markers in the presence of a metabolic burden

BACKGROUND

The overall burden of chronic disease, inflammation and cardiovascular risk increases with age. Whether the relationship between age and inflammation is impacted by presence of an adverse metabolic burden is not known.

METHODS

We determined inflammatory markers in humans (336 Caucasians and 224 African Americans) and in mice, representing a spectrum of age, weight and metabolic burden.

RESULTS

In humans, levels of inflammatory markers increased significantly with age in subjects without the metabolic syndrome, (P=0.009 and P=0.037 for C-reactive protein, P<0.001 and P=0.001 for fibrinogen, P<0.001 and P=0.005 for serum amyloid-A, for Caucasians and African Americans, respectively). In contrast, trend patterns of inflammatory markers did not change significantly with age in subjects with metabolic syndrome in either ethnic group, except for fibrinogen in Caucasians. A composite z-score for systemic inflammation increased significantly with age in subjects without metabolic syndrome (P=0.004 and P<0.006 for Caucasians and African Americans, respectively) but not in subjects with metabolic syndrome (P=0.009 for difference in age trend between metabolic syndrome and non-metabolic syndrome). In contrast, no similar age trend was found in vascular inflammation. The findings in humans were paralleled by results in mice as serum amyloid-A levels increased across age (range 2-15 months, P<0.01) and were higher in ob/ob mice compared to control mice (P<0.001).

CONCLUSIONS

Presence of a metabolic challenge in mice and humans influences levels of inflammatory markers over a wide age range. Our results underscore that already at a young age, presence of a metabolic burden enhances inflammation to a level that appears to be similar to that of decades older people without metabolic syndrome.

Significant associations between lipoprotein(a) and corrected apolipoprotein B-100 levels in African-Americans

OBJECTIVES

Lipoprotein(a), Lp(a), represents an apolipoprotein (apo) B-carrying lipoprotein, yet the relationship between Lp(a) and apoB levels has not been fully explored.

METHODS

We addressed the relationship between Lp(a) and apoB-containing lipoprotein levels in 336 Caucasians and 224 African-Americans. Our approach takes unique molecular properties of Lp(a) as well as contribution of Lp(a) to the levels of these lipoproteins into account.

RESULTS

Levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), apoB and apoB/apoA-1 did not differ across ethnicity. African-Americans had higher levels of Lp(a) and high-density lipoprotein cholesterol and lower triglyceride levels compared to Caucasians. Lp(a) levels were correlated with levels of TC (p < 0.005), LDL-C (p < 0.001), apoB (p < 0.05) or apoB/apoA-1 (p < 0.05) in both ethnic groups. These associations remained significant only in African-Americans after adjustments for the contribution of Lp(a)-cholesterol or Lp(a)-apoB. Furthermore, taking Lp(a)-apoB into account, allele-specific apo(a) levels were significantly associated with apoB levels and the apoB/apoA-1 ratio in African-Americans. The latter associations in African-Americans remained significant for allele-specific apo(a) levels for smaller apo(a) sizes (<26 K4 repeats), after controlling for the effects of age, sex, and BMI.

CONCLUSIONS

Although TC, LDL-C, and apoB levels were comparable between African-Americans and Caucasians, the associations of these parameters with Lp(a) and allele specific apo(a) levels differed between these two ethnic groups. In African-Americans, apoB and apoB/apoA-1 remained consistently and positively associated with both Lp(a) and allele-specific apo(a) levels after adjustments for the contribution of Lp(a)-apoB. The findings suggest an interethnic difference with a closer relationship between Lp(a) and apoB among African-Americans.

Interactive effects of ApoE polymorphism, alcohol and smoking on age-related trends of blood pressure levels in elderly men: the Bambuì Cohort Study of Ageing (1997-2008)

Data from a population-based prospective study were used to examine longitudinal changes in blood pressure (BP) and seek interactions between apolipoprotein E (ApoE) genotypes, smoking and alcohol in a cohort of 557 elderly Brazilian men. Repeated BP measurements were obtained in four waves, and multi-level random-effects pattern-mixture models were used to evaluate age-related BP trajectories while accounting for non-ignorable dropouts/deaths and handling heterogeneities as random parameter variations. Alcohol was associated with high systolic BP in ε2 carriers and those with the ε3/3 genotype, but not in ε4 carriers. This was dependent on age and smoking habits: at the age of 60, expected systolic BP in alcohol drinking ε2 carriers was 16.5 mm Hg higher than in the reference group of non-smokers/non-drinkers if they were not smokers (P=0.049), and 28.6 mm Hg higher if they were also smokers (P=0.004). The youngest smoking/non-drinking ε2 carriers had lower systolic BP, but it increased rapidly and led to higher expected levels among older carriers. Alcohol consumption, alone or together with smoking, interacts with the effects of ApoE genotype on systolic BP, probably nullifying the more favourable lipid profile of ε2 carriers. The interactions of gene-modifiable risk factors have major public health implications.

Apo E4 and lipoprotein-associated phospholipase A2 synergistically increase cardiovascular risk

OBJECTIVE

Apolipoprotein E (apoE) has been implicated as conveying increased risk for coronary artery disease (CAD). Previous studies suggest a role of apoE as a modulator of immune response and inflammatory properties. We hypothesized that the presence of apo E4 is associated with an increased inflammatory burden in subjects with CAD as compared to subjects without CAD.

METHODS

ApoE genotypes, systemic (C-reactive protein [CRP], fibrinogen, serum amyloid-A [SAA]) and vascular inflammatory markers (Lipoprotein-associated phospholipase A(2) [Lp-PLA(2)] and pentraxin-3 [PTX-3]) were assessed in 324 Caucasians and 208 African Americans, undergoing coronary angiography.

RESULTS

For both ethnic groups, Lp-PLA(2) index, an integrated measure of Lp-PLA(2) mass and activity, increased significantly and stepwise across apoE isoforms (P = 0.009 and P = 0.026 for African Americans and Caucasians respectively). No differences were found for other inflammatory markers tested (CRP, fibrinogen, SAA and PTX-3). For the top cardiovascular score tertile, apo E4 carriers had a significantly higher level of Lp-PLA(2) index in both ethnic groups (P = 0.027 and P = 0.010, respectively).

CONCLUSION

The presence of the apo E4 isoform was associated with a higher level of Lp-PLA(2) index, a marker of vascular inflammation. Our results suggest that genetic variation at the apoE locus may impact cardiovascular disease risk through enhanced vascular inflammation.

The association of apolipoprotein E polymorphism and lipid levels in children with a family history of premature coronary artery disease

BACKGROUND

Polymorphisms in the apolipoprotein E (apoE) gene may modulate lipoprotein metabolism and influence plasma lipid levels. Thus, they have been associated with relative risk of coronary artery disease (CAD).

OBJECTIVE

To evaluate the association of apolipoprotein E polymorphism and lipid levels in children with family history of premature coronary artery disease.

METHODS

The apoE genotypes, allele frequencie,s and plasma lipid levels were analyzed in 137 children. Among these children, 70 (study group) had and 67 (control group) did not have a parental history of premature CAD RESULTS: Total cholesterol (Tc) levels were greater in the study group (P = .04). The frequencies of ɛ3ɛ4 genotype and ɛ4 allele were significantly greater in the study group (P = 005 for both), Thɛ ɛ2 allele correlated negatively with Tc and low-density lipoprotein cholesterol levels, and ɛ4 had a positive correlation with Tc and low-density lipoprotein cholesterol levels.

CONCLUSIONS

Tc levels are influenced by apoE genotypes in childhood. Also, the frequency of the ɛ4 allele is greater in children with family history of premature CAD. The ɛ4 allele may be associated with an increased risk for development of atherosclerosis by elevated levels of Tc in children with family history of CAD. The evaluation of apoE gene polymorhisms may contribute to the assessment of cardiovascular risk in children with a family history of CAD.

Age as a modulator of inflammatory cardiovascular risk factors

OBJECTIVE

Levels of acute phase reactants are affected by age. The extent to which cardiovascular risk associated with aging is due to an increase in the inflammatory burden is not known. We assessed the relationship with age of inflammatory markers, representing (1) systemic (C-reactive protein, fibrinogen, and serum amyloid-A) and (2) vascular (lipoprotein-associated phospholipase A(2) and pentraxin-3) inflammation.

METHODS AND RESULTS

We determined lipoprotein-associated phospholipase A(2) mass and activity, C-reactive protein, fibrinogen, serum amyloid-A, and pentraxin-3 levels and other cardiovascular disease risk factors in 336 whites and 224 African Americans. Levels of systemic inflammatory markers increased significantly with age in both ethnic groups (P<0.05 for all), whereas trend patterns of vascular inflammatory markers did not change significantly with age for either group. In multivariate regression models adjusting for confounding variables, age remained independently associated with a composite Z score for systemic but not vascular inflammation (β=0.250, P<0.001, and β=0.276, P<0.001, for whites and African Americans, respectively).

CONCLUSIONS

We report an increase in the systemic but not vascular inflammatory burden with age. Levels of both categories of inflammatory markers with age were similar across ethnicity after adjustment for confounders. Our results underscore the importance of age in evaluating inflammatory markers to assess cardiovascular risk.

Integrated role of two apoliprotein E polymorphisms on apolipoprotein B levels and coronary artery disease in a biethnic population

BACKGROUND

Apolipoprotein E (ApoE) plays a major role in lipoprotein metabolism and genetic variability of ApoE confers susceptibility to coronary artery disease (CAD). Beyond variability in the coding region, promoter polymorphisms in the ApoE gene impact on ApoE transcription.

METHODS

We determined the ApoE - 491 A/T promoter polymorphism, ApoE isoforms, lipid and lipoprotein levels, and CAD risk factors in 313 Caucasians and 215 African Americans.

RESULTS

Caucasians had a lower ApoE T allele frequency compared to African Americans (18.1% vs. 32.3%, P < 0.05). Among T/* carriers, ApoB levels were significantly lower in Caucasians, but significantly higher among African Americans, in both cases compared to A/A homozygotes (P = 0.017, and P = 0.012). For a given -491A/T genotype, levels of atherogenic lipoproteins differed across ApoE2/E3/E4 isoforms among African Americans, but not Caucasians, as T/* carriers with ApoE4 had significantly higher ApoB levels compared to T/* carriers with ApoE2 (P = 0.010). Among patients with CAD, Caucasian A/A homozygotes and African American T/* carriers had higher ApoB levels compared to the same genotype without CAD (P = 0.007, P = 0.049, respectively).

CONCLUSIONS

We observed an ethnicity-specific variability in ApoB levels across the ApoE - 491 A/T polymorphism and a modulatory impact on this pattern by ApoE2/E3/E4 isoforms.

The vascular contribution to Alzheimer's disease

AD (Alzheimer's disease) is a progressive neurodegenerative disease of unknown origin. Despite questions as to the underlying cause(s) of this disease, shared risk factors for both AD and atherosclerotic cardiovascular disease indicate that vascular mechanisms may critically contribute to the development and progression of both AD and atherosclerosis. An increased risk of developing AD is linked to the presence of the apoE4 (apolipoprotein E4) allele, which is also strongly associated with increased risk of developing atherosclerotic cardiovascular disease. Recent studies also indicate that cardiovascular risk factors, including elevated blood cholesterol and triacylglycerol (triglyceride), increase the likelihood of AD and vascular dementia. Lipids and lipoproteins in the circulation interact intimately with the cerebrovasculature, and may have important effects on its constituent brain microvascular endothelial cells and the adjoining astrocytes, which are components of the neurovascular unit. The present review will examine the potential mechanisms for understanding the contributions of vascular factors, including lipids, lipoproteins and cerebrovascular Abeta (amyloid beta), to AD, and suggest therapeutic strategies for the attenuation of this devastating disease process. Specifically, we will focus on the actions of apoE, TGRLs (triacylglycerol-rich lipoproteins) and TGRL lipolysis products on injury of the neurovascular unit and increases in blood-brain barrier permeability.

Association of lipoprotein-associated phospholipase A2 with coronary artery disease in African-Americans and Caucasians

CONTEXT

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is bound predominately to low-density lipoprotein and has been implicated as a risk factor for coronary artery disease (CAD).

OBJECTIVE

We investigated the association between Lp-PLA(2) and CAD in a biethnic African-American and Caucasian population.

DESIGN

Lp-PLA(2) mass, activity, and index, an integrated measure of mass and activity, and other cardiovascular risk factors were determined in 224 African-Americans and 336 Caucasians undergoing coronary angiography.

MAIN OUTCOME MEASURES

We assessed the distribution of Lp-PLA(2) levels and determined the predictive role of Lp-PLA(2) as a risk factor for CAD.

RESULTS

Levels of Lp-PLA(2) mass and activity were higher among Caucasians compared with African-Americans (293 +/- 75 vs. 232 +/- 76 ng/ml, P < 0.001 for mass and 173 +/- 41 vs. 141 +/- 39 nmol/min/ml, P < 0.001 for activity, respectively). However, Lp-PLA(2) index was similar in the two groups (0.61 +/- 0.17 vs. 0.64 +/- 0.19, P = NS). In both ethnic groups, Lp-PLA(2) activity and index was significantly higher among subjects with CAD. African-American subjects with CAD had significantly higher Lp-PLA(2) index than corresponding Caucasian subjects (0.69 +/- 0.20 vs. 0.63 +/- 0.18, P = 0.028). In multivariate regression analyses, after adjusting for other risk factors, Lp-PLA(2) index was independently (odds ratio 6.7, P = 0.047) associated with CAD in African-Americans but not Caucasians.

CONCLUSIONS

Lp-PLA(2) activity and index was associated with presence of CAD among African-Americans and Caucasians undergoing coronary angiography. The findings suggest an independent impact of vascular inflammation among African-Americans as contributory to CAD risk and underscore the importance of Lp-PLA(2) as a cardiovascular risk factor.

ApoE and ApoC-I polymorphisms: association of genotype with cardiovascular disease phenotype in African Americans

Apolipoproteins (apo) E and C-I are components of triglyceride (TG)-rich lipoproteins and impact their metabolism. Functional polymorphisms have been established in apoE but not in apoC-I. We studied the relationship between apoE and apoC-I gene polymorphisms and plasma lipoproteins and coronary artery disease (CAD) in 211 African Americans and 306 Caucasians. In African Americans but not in Caucasians, apoC-I H2-carriers had significantly lower total and LDL cholesterol and apoB levels, and higher glucose, insulin, and HOMA-IR levels compared with H1 homozygotes. Differences across CAD phenotypes were seen for the apoC-I polymorphism. African-American H2-carriers without CAD had significantly lower total cholesterol (P < 0.001), LDL cholesterol (P < 0.001), and apoB (P < 0.001) levels compared with H1 homozygotes, whereas no differences were found across apoC-I genotypes for African Americans with CAD. Among African-American apoC-I H1 homozygotes, subjects with CAD had a profile similar to the metabolic syndrome (i.e., higher triglyceride, glucose, and insulin) compared with subjects without CAD. For African-American H2-carriers, subjects with CAD had a pro-atherogenic lipid pattern (i.e., higher LDL cholesterol and apoB levels), compared with subjects without CAD. ApoC-I genotypes showed an ethnically distinct phenotype relationship with regard to CAD and CAD risk factors.

Comparison of C-reactive protein and metabolic syndrome as cardiovascular risk factors in African-Americans and European-Americans

The aim of this study was to investigate the association of C-reactive protein (CRP) with the metabolic syndrome (MS) and its components, and their association with coronary artery disease (CAD) in African Americans and European Americans. MS was defined using revised National Cholesterol Education Program Adult Treatment Panel III criteria in 224 African Americans and 304 European Americans who underwent coronary angiography; CAD was defined as > or =50% stenosis in any segment or as a composite cardiovascular score (0 to 75). The relative frequencies of MS and CAD were significantly higher in African Americans with high (> or =3 mg/L) versus low (<3 mg/L) CRP levels (76% vs 24%, p <0.001, for MS and 70% vs 30%, p = 0.001, for CAD). Composite scores were higher in subjects with high (> or =3 mg/L) versus low (<3 mg/L) CRP levels in African Americans (16.9 vs 11.2, p = 0.038) and European Americans (18.5 vs 14.5, p = 0.002). Furthermore, in the 2 ethnic groups, cardiovascular scores were higher in subjects with MS, irrespective of CRP levels. Adjusting for other risk factors, multiple regression analysis demonstrated an association of MS, but not CRP, with CAD in European Americans but not African Americans (r(2) = 0.533, p <0.001). In conclusion, MS was independently associated with CAD in European Americans and African Americans, whereas CRP did not add prognostic information beyond established cardiovascular risk factors in either ethnic group.

Synergistic role of inflammation and insulin resistance as coronary artery disease risk factors in African Americans and Caucasians

The separate roles of inflammation and insulin resistance (IR) in the pathogenesis of cardiovascular disease (CVD) are well recognized. We investigated whether presence of inflammation would modify coronary artery disease (CAD) risk prediction in subjects with or without IR. Insulin, glucose, CRP and fibrinogen levels were determined in 317 Caucasians and 222 African Americans undergoing diagnostic coronary angiography. Extent of CAD was defined by a composite score (0-75). The overall prevalence of IR (HOMA-IR>or=3.0) in Caucasians and African Americans was 32.5% and 22.9%, respectively (P<0.05). The degree of CAD (composite score) was higher in subjects with IR (20.7 vs. 14.5, P=0.014 and 20.1 vs. 13.1, P=0.031 for Caucasians and African Americans, respectively), and in a multiple regression model IR was an independent predictor for CAD in both groups. In both ethnic groups, subjects with a combination of IR and high CRP (>or=3mg/l) had significantly higher composite score compared to those with no IR and low CRP (<3mg/l) (21.2 vs. 13.9, P<0.05 and 20.9 vs. 10.2, P<0.05 for Caucasians and African Americans, respectively). Similarly, the composite score was significantly higher in subjects with IR and high fibrinogen (>or=340 mg/dl) compared to those with no IR and low fibrinogen. In conclusion, elevated levels of inflammatory markers were positively associated with IR. Further, a combination of IR and inflammation resulted in a higher degree of CAD in both Caucasians and African Americans. The results suggest that inflammation may potentiate the cardiovascular risk factor role of IR.

APOE genotype affects black-white responses of high-density lipoprotein cholesterol subspecies to aerobic exercise training

The objective of the study was to determine whether ethnicity interacts with the APOE genotype to influence conventionally measured high-density lipoprotein cholesterol (HDL-C) subfraction levels and nuclear magnetic resonance-measured (HDL(NMR)-C) particle size at baseline and after training, and the changes with training. After a 6-week dietary stabilization period, men and postmenopausal women 50 to 75 years old underwent baseline testing (NMR lipid, maximum oxygen consumption, body composition, and genotyping assessments). Tests were repeated after completing 24 weeks of endurance exercise training. At baseline, APOE2/3 blacks had significantly larger particle size (P < .001) and higher total HDL(NMR)-C particle concentration (P = .006) than whites. After 6 months of endurance exercise training, APOE2/3 blacks maintained a significantly larger HDL(NMR)-C particle size (P < .001) and particle concentration of the large HDL(NMR)-C than APOE2/3 whites (P < .001). In multivariate analyses of variance adjusted for demographic and environmental confounding factors and for training-induced changes in lean body mass and intraabdominal fat, the model explained approximately 33% of the observed variability in training-induced improvements in HDL(NMR)-C particle size (P = .002), with APOE2/3 blacks having a greater increase in training-induced changes in HDL(NMR)-C particle size. In a separate but similarly adjusted model for conventionally measured HDL(2)-C, the model explained approximately 49% of the observed variability in training-induced changes in HDL(2)-C. Ethnicity interacted with the E2/3 genotype at the APOE gene locus to influence higher baseline and after-training levels, and greater exercise training-induced improvements in the advantageous HDL-C subfractions in blacks than in whites. APOE2/3 blacks may benefit more from aerobic fitness to reduce cardiovascular risk.

High levels of inflammatory biomarkers are associated with increased allele-specific apolipoprotein(a) levels in African-Americans

BACKGROUND

A role of inflammation for cardiovascular disease (CVD) is established. Lipoprotein(a) [Lp(a)] is an independent CVD risk factor where plasma levels are determined by the apolipoprotein(a) [apo(a)] gene, which contains inflammatory response elements.

DESIGN

We investigated the effect of inflammation on allele-specific apo(a) levels in African-Americans and Caucasians. We determined Lp(a) levels, apo(a) sizes, allele-specific apo(a) levels, fibrinogen and C-reactive protein (CRP) levels in 167 African-Americans and 259 Caucasians.

RESULTS

Lp(a) levels were increased among African-Americans with higher vs. lower levels of CRP [<3 vs. > or =3 mg/liter (143 vs. 108 nmol/liter), P = 0.009] or fibrinogen (<340 vs. > or =340 mg/liter, P = 0.002). We next analyzed allele-specific apo(a) levels for different apo(a) sizes. No differences in allele-specific apo(a) levels across CRP or fibrinogen groups were seen among African-Americans or Caucasians for small apo(a) sizes (<22 kringle 4 repeats). Allele-specific apo(a) levels for medium apo(a) sizes (22-30 kringle 4 repeats) were significantly higher among African-Americans, with high levels of CRP or fibrinogen compared with those with low levels (88 vs. 67 nmol/liter, P = 0.014, and 91 vs. 59 nmol/liter, P < 0.0001, respectively). No difference was found for Caucasians.

CONCLUSIONS

Increased levels of CRP or fibrinogen are associated with higher allele-specific medium-sized apo(a) levels in African-Americans but not in Caucasians. These findings indicate that proinflammatory conditions result in a selective increase in medium-sized apo(a) levels in African-Americans and suggest that inflammation-associated events may contribute to the interethnic difference in Lp(a) levels between African-Americans and Caucasians.

Metabolic syndrome components in african-americans and European-american patients and its relation to coronary artery disease

A number of factors used to define the metabolic syndrome (MS) differ between African-American and European-American patients, which raises the question whether the individual constellation of MS components would impact cardiovascular risk. Our objectives were to assess the association between the MS and coronary artery disease (CAD) across ethnicities and to explore whether the constellation used to define the syndrome would impact any such association. We studied the distribution of the MS and its relation to CAD in 304 European-American subjects and 224 African-American subjects undergoing diagnostic coronary angiography. The overall prevalence of the MS in European-American and African-American subjects were 65.5% and 49.1%, respectively. Compared with European-American subjects, the lipid components of the syndrome were less frequent among African-American subjects (44% vs 64% [p <0.001] for high-density lipoprotein [HDL] cholesterol and 21% vs 51% [p <0.001] for triglyceride, respectively). The prevalence of CAD was significantly higher in subjects with MS across ethnicity (71.1% of European-American subjects and 56.6% of African-American subjects, p = 0.017 and p = 0.046, respectively). Multiple regression analyses demonstrated an association of blood pressure and HDL cholesterol with CAD among European-American subjects, which remained significant taking other risk factors into account (r(2) = 0.542, p <0.001). In conclusion, presence of CAD was more common among subjects with MS independently of ethnicity. Of the MS components, blood pressure was associated with CAD among European-American subjects. Although our findings may not be directly extrapolated to the population at large, they illustrate the importance of a high-risk metabolic environment as a cardiovascular risk factor.

Adiponectin levels are associated with coronary artery disease across Caucasian and African-American ethnicity

The hypothesis was tested that plasma levels of adiponectin would be associated with coronary artery disease (CAD) across African-American and Caucasian ethnicity and gender. Adiponectin levels, cardiovascular risk factors, and extent of CAD were measured in 453 subjects (173 African-American and 280 Caucasian men and women). The distribution of adiponectin levels differed significantly between African-Americans and Caucasians (P<0.0001). Among African-Americans, the adiponectin distribution was skewed toward lower levels. For women, adiponectin levels were higher among Caucasians compared with African-Americans (P<0.001), whereas no interethnic difference was observed for men. Irrespective of ethnic group, subjects with CAD had lower levels of adiponectin than did subjects without CAD. Adiponectin was negatively and significantly associated with waist-hip ratio, body mass index, diastolic blood pressure, insulin level, and homeostasis model assessment-insulin resistance in both ethnic groups. Among lipid parameters, total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels were negatively correlated with adiponectin, whereas the high-density lipoprotein cholesterol level correlated positively for both African-Americans and Caucasians. In a multiple regression model, controlling for gender, ethnicity, and other CAD risk factors, adiponectin levels were negatively associated with CAD (P<0.05). The results indicate that, across gender and ethnicity, low adiponectin levels may be an independent risk factor for CAD.