ApoE plasma levels and risk of cardiovascular mortality in old age

Does low birth weight affect the presence of cardiometabolic risk factors in overweight and obese children?

Recent findings suggest that low-birth-weight children with current obesity are more likely to have higher systolic blood pressure levels and impaired β-cell function than those who are obese with normal birth weight. It seems possible, however, that concurrent low birth weight with excess weight gain can exacerbate other risk factors for cardiometabolic diseases. The purpose of this study is to investigate the influence of birth weight on the lipid/apolipoprotein profile, visfatin levels, and insulin parameters in overweight/obese children. A cross-sectional study of 68 overweight/obese children was conducted. Among these children, 28 were identified with low birth weight and 40 were of normal birth weight. Blood lipid profile, apolipoproteins, visfatin, glucose, and insulin were measured. Our results show that systolic blood pressure (SBP) and diastolic blood pressure (DBP) levels, triglycerides (TG), very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDLc), apolipoprotein B and E, insulin, apolipoprotein B/A1 ratio, and homeostasis model assessment insulin resistance (HOMA-IR) were significantly elevated in overweight/obese low-birth-weight (LBW) children. There was a significant association of the SBP levels with TG (P=0.027), LDLc (P=0.001), HOMA-IR (P<0.001), apolipoprotein B (P=0.001), and apolipoprotein E (P=0.039).

CONCLUSION

Our findings suggest that LBW children with overweight or obesity have an additional risk factor for both atherogenic and insulinogenic profile.

Influence of genetic variation on plasma protein levels in older adults using a multi-analyte panel

Proteins, widely studied as potential biomarkers, play important roles in numerous physiological functions and diseases. Genetic variation may modulate corresponding protein levels and point to the role of these variants in disease pathophysiology. Effects of individual single nucleotide polymorphisms (SNPs) within a gene were analyzed for corresponding plasma protein levels using genome-wide association study (GWAS) genotype data and proteomic panel data with 132 quality-controlled analytes from 521 Caucasian participants in the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. Linear regression analysis detected 112 significant (Bonferroni threshold p = 2.44×10⁻⁵) associations between 27 analytes and 112 SNPs. 107 out of these 112 associations were tested in the Indiana Memory and Aging Study (IMAS) cohort for replication and 50 associations were replicated at uncorrected p<0.05 in the same direction of effect as those in the ADNI. We identified multiple novel associations including the association of rs7517126 with plasma complement factor H-related protein 1 (CFHR1) level at p<1.46×10⁻⁶⁰, accounting for 40 percent of total variation of the protein level. We serendipitously found the association of rs6677604 with the same protein at p<9.29×10⁻¹¹². Although these two SNPs were not in the strong linkage disequilibrium, 61 percent of total variation of CFHR1 was accounted for by rs6677604 without additional variation by rs7517126 when both SNPs were tested together. 78 other SNP-protein associations in the ADNI sample exceeded genome-wide significance (5×10⁻⁸). Our results confirmed previously identified gene-protein associations for interleukin-6 receptor, chemokine CC-4, angiotensin-converting enzyme, and angiotensinogen, although the direction of effect was reversed in some cases. This study is among the first analyses of gene-protein product relationships integrating multiplex-panel proteomics and targeted genes extracted from a GWAS array. With intensive searches taking place for proteomic biomarkers for many diseases, the role of genetic variation takes on new importance and should be considered in interpretation of proteomic results.

Lipidomics of familial longevity

Middle-aged offspring of nonagenarians, as compared to their spouses (controls), show a favorable lipid metabolism marked by larger LDL particle size in men and lower total triglyceride levels in women. To investigate which specific lipids associate with familial longevity, we explore the plasma lipidome by measuring 128 lipid species using liquid chromatography coupled to mass spectrometry in 1526 offspring of nonagenarians (59 years ± 6.6) and 675 (59 years ± 7.4) controls from the Leiden Longevity Study. In men, no significant differences were observed between offspring and controls. In women, however, 19 lipid species associated with familial longevity. Female offspring showed higher levels of ether phosphocholine (PC) and sphingomyelin (SM) species (3.5–8.7%) and lower levels of phosphoethanolamine PE (38:6) and long-chain triglycerides (TG) (9.4–12.4%). The association with familial longevity of two ether PC and four SM species was independent of total triglyceride levels. In addition, the longevity-associated lipid profile was characterized by a higher ratio of monounsaturated (MUFA) over polyunsaturated (PUFA) lipid species, suggesting that female offspring have a plasma lipidome less prone to oxidative stress. Ether PC and SM species were identified as novel longevity markers in females, independent of total triglycerides levels. Several longevity-associated lipids correlated with a lower risk of hypertension and diabetes in the Leiden Longevity Study cohort. This sex-specific lipid signature marks familial longevity and may suggest a plasma lipidome with a better antioxidant capacity, lower lipid peroxidation and inflammatory precursors, and an efficient beta-oxidation function.

Apolipoprotein E in VLDL and LDL with apolipoprotein C-III is associated with a lower risk of coronary heart disease

BACKGROUND

Low-density lipoprotein (LDL) with apolipoprotein C-III (apoC-III) is the lipoprotein species that most strongly predicts initial and recurring coronary heart disease (CHD) events in several cohorts. Thus, a large portion of the CHD risk conferred by LDL may be attributable to LDL that contains apoC-III. Very-low-density lipoprotein (VLDL) and LDL with apoC-III have varying amounts of apoE. We hypothesized that a high content of apoE lessens the adverse influence of apoC-III on the risk of CHD because it promotes the clearance of VLDL and LDL from plasma.

METHODS AND RESULTS

We studied 2 independent cohorts, the Nurses' Health Study, composed of women, and the Health Professionals Follow-up Study, composed of men. These cohorts contributed to this study 322 women and 418 men initially free of CVD who developed a fatal or nonfatal myocardial infarction during 10 to 14 years of follow-up and matched controls who remained free of CHD. The apoE content of LDL with apoC-III was inversely associated with CHD after multivariable adjustment (relative risk for top versus bottom quintile 0.53, 95% CI 0.35 to 0.80). The apoE content of VLDL with apoC-III had a similar inverse association with CHD. The highest risks were associated with a high apoB concentration and a low apoE content of LDL with apoC-III or of VLDL+LDL with apoC-III. The observed associations were in both male and female cohorts and independent of traditional CHD risk factors and of C-reactive protein.

CONCLUSIONS

An increased apoE content in VLDL and LDL with apoC-III was associated with a lower risk of CHD. Strategies to enrich VLDL and LDL in apoE are worth exploring for the prevention of CHD.

Brain regional correlation of amyloid-β with synapses and apolipoprotein E in non-demented individuals: potential mechanisms underlying regional vulnerability to amyloid-β accumulation

To reveal the underlying mechanisms responsible for the regional vulnerability to amyloid-β (Aβ) accumulation prior to the development of Alzheimer's disease, we studied distribution of Aβ, apolipoprotein E (apoE), synaptic markers, and other molecules involved in Aβ metabolism in multiple brain areas of non-demented individuals. Twelve brain regions including neocortical, limbic, and subcortical areas were dissected from brains of non-demented individuals and extracted according to increasing insolubility by a sequential three-step method. The levels of Aβ40, Aβ42, apoE, APP, APP-CTFβ, BACE1, presenilin-1, neprilysin, insulysin, LRP1, LDLR, synaptophysin, PSD95, GFAP, and lactate were determined by ELISAs or enzymatic assays. The regional distribution of apoE showed moderate-to-strong inverse correlation with levels of Aβ, especially insoluble Aβ40. On the other hand, the regional distributions of synaptic markers, particularly PSD95, showed moderate-to-strong positive correlation with levels of Aβ, especially soluble Aβ40. The regional correlations between Aβ and LRP1, GFAP, or lactate were mild-to-moderate. Moderate-to-strong positive regional correlations were observed between apoE and GFAP or lactate and between PSD95 and LRP1. No significant regional correlations were detected between Aβ and APP, APP-CTFβ, BACE1, or presenilin-1, those involved in Aβ production. There were no significant negative regional correlations between Aβ and two major Aβ degrading enzymes, neprilysin and insulysin. These regional correlations remained consistent regardless of the degree of Aβ accumulation. The regional vulnerability to Aβ accumulation may be due to a net balance between two competing processes: (1) synapses involved in promoting the initial Aβ accumulation and (2) astrocyte-derived apoE involved in preventing Aβ accumulation.

Identification of a functional apolipoprotein E promoter polymorphism regulating plasma apolipoprotein E concentration

OBJECTIVE

There is compelling evidence that the plasma apolipoprotein E (APOE) concentration, in addition to the APOE ε2/ε3/ε4 genotype, influences plasma lipoprotein levels, but the functional genetic variants influencing the plasma APOE concentration have not been identified.

APPROACH AND RESULTS

Genome-wide association studies in 2 cohorts of healthy, middle-aged subjects identified the APOE locus as the only genetic locus showing robust associations with the plasma APOE concentration. Fine-mapping of the APOE locus confirmed that the rs7412 ε2-allele is the primary genetic variant responsible for the relationship with plasma APOE concentration. Further mapping of the APOE locus uncovered that rs769446 (-427T/C) in the APOE promoter is independently associated with the plasma APOE concentration. Expression studies in 199 human liver samples demonstrated that the rs769446 C-allele is associated with increased APOE mRNA levels (P=0.015). Transient transfection studies and electrophoretic mobility shift assays in human hepatoma HepG2 cells corroborated the role of rs769446 in transcriptional regulation of APOE. However, no relationships were found between rs769446 genotype and plasma lipoprotein levels in 2 cohorts (n=1648 and n=1039) of healthy middle-aged carriers of the APOE ε3/ε3 genotype.

CONCLUSIONS

rs769446 is a functional polymorphism involved in the regulation of the plasma APOE concentration.

Protein kinase C controls vesicular transport and secretion of apolipoprotein E from primary human macrophages

Macrophage-specific apolipoprotein E (apoE) secretion plays an important protective role in atherosclerosis. However, the precise signaling mechanisms regulating apoE secretion from primary human monocyte-derived macrophages (HMDMs) remain unclear. Here we investigate the role of protein kinase C (PKC) in regulating basal and stimulated apoE secretion from HMDMs. Treatment of HMDMs with structurally distinct pan-PKC inhibitors (calphostin C, Ro-31-8220, Go6976) and a PKC inhibitory peptide all significantly decreased apoE secretion without significantly affecting apoE mRNA or apoE protein levels. The PKC activator phorbol 12-myristate 13-acetate (PMA) stimulated apoE secretion, and both PMA-induced and apoAI-induced apoE secretion were inhibited by PKC inhibitors. PKC regulation of apoE secretion was found to be independent of the ATP binding cassette transporter ABCA1. Live cell imaging demonstrated that PKC inhibitors inhibited vesicular transport of apoE to the plasma membrane. Pharmacological or peptide inhibitor and knockdown studies indicate that classical isoforms PKCα/β and not PKCδ, -ε, -θ, or -ι/ζ isoforms regulate apoE secretion from HMDMs. The activity of myristoylated alanine-rich protein kinase C substrate (MARCKS) correlated with modulation of PKC activity in these cells, and direct peptide inhibition of MARCKS inhibited apoE secretion, implicating MARCKS as a downstream effector of PKC in apoE secretion. Comparison with other secreted proteins indicated that PKC similarly regulated secretion of matrix metalloproteinase 9 and chitinase-3-like-1 protein but differentially affected the secretion of other proteins. In conclusion, PKC regulates the secretion of apoE from primary human macrophages.

Effect of fenofibrate and atorvastatin on VLDL apoE metabolism in men with the metabolic syndrome

We examined the effects of fenofibrate and atorvastatin on very low density lipoprotein (VLDL) apolipoprotein (apo)E metabolism in the metabolic syndrome (MetS). We studied 11 MetS men in a randomized, double-blind, crossover trial. VLDL-apoE kinetics were examined using stable isotope methods and compartmental modeling. Compared with placebo, fenofibrate (200 mg/day) and atorvastatin (40 mg/day) decreased plasma apoE concentrations (P < 0.05). Fenofibrate decreased VLDL-apoE concentration and production rate (PR) and increased VLDL-apoE fractional catabolic rate (FCR) compared with placebo (P < 0.05). Compared with placebo, atorvastatin decreased VLDL-apoE concentration and increased VLDL-apoE FCR (P < 0.05). Fenofibrate and atorvastatin had comparable effects on VLDL-apoE concentration. The increase in VLDL-apoE FCR with fenofibrate was 22% less than that with atorvastatin (P < 0.01). With fenofibrate, the change in VLDL-apoE concentration was positively correlated with change in VLDL-apoB concentration, and negatively correlated with change in VLDL-apoB FCR. In MetS, fenofibrate and atorvastatin decreased plasma apoE concentrations. Fenofibrate decreased VLDL-apoE concentration by lowering VLDL-apoE production and increasing VLDL-apoE catabolism. By contrast, atorvastatin decreased VLDL-apoE concentration chiefly by increasing VLDL-apoE catabolism. Our study provides new insights into the mechanisms of action of two different lipid-lowering therapies on VLDL-apoE metabolism in MetS.

High serum apolipoprotein E determines hypertriglyceridemic dyslipidemias, coronary disease and apoA-I dysfunctionality

The relevance of serum apolipoprotein E (apoE) levels to two hypertriglyceridemic dyslipidemias has not been clarified. We explored, in a cross-sectional (and short-term prospective) evaluation, the independent relationship of serum apoE to the atherogenic dyslipidemia, hypertriglyceridemia with elevated apoB (HtgB) and to apoA-I dysfunctionality, previously shown in Turkish adults to be independent of apoE genotype. Serum apoE concentrations were measured by immunonephelometry in 1,127 middle-aged adults. In multivariable regression analysis, apoE concentrations showed log-linear associations with apoB and apoA-I levels, waist circumference, independent of C-reactive protein (CRP), homeostatic model assessment (HOMA) index and other confounders. The likelihood of atherogenic dyslipidemia and of HtgB roughly tripled per 1-SD increment in apoE concentrations, additively to apoE genotype, HOMA, apoA-I, CRP concentrations and waist circumference; yet apoA-I, protective against atherogenic dyslipidemia, appeared to promote HtgB, a finding consistent with apoA-I dysfunctionality in this setting. Each 1-SD increment in the apoE level was moreover, associated in both genders with MetS (at OR 1.5), after adjustment for sex, age, apoB, apoA-I and CRP, or for apoE genotypes. Circulating apoE predicted in both genders age-adjusted prevalent and incident coronary heart disease (CHD), independent of apoE genotype and CRP (OR 1.32 [95 % CI 1.11; 1.58]). To conclude, in a general population prone to MetS, elevated apoE concentrations are strongly linked to HtgB and atherogenic dyslipidemia, irrespective of apoE genotype, are associated with MetS and CHD. Excess apoE reflects pro-inflammatory state and likely autoimmune activation.

Coronary disease risk prediction algorithm warranting incorporation of C-reactive protein in Turkish adults, manifesting sex difference

BACKGROUND AND AIM

An algorithm is needed for predicting coronary heart disease (CHD) risk in Turkish adults who have a high prevalence of metabolic syndrome (MetS).

METHODS AND RESULTS

Ten-year risk of CHD was estimated in 2232 middle-aged adults free of CHD at baseline, followed over 7.6-years. Cox proportional hazard regression was used to predict CHD. Discrimination was assessed with area under receiver operating characteristics curve (AROC). CHD developed in 302 subjects. In multivariable analysis, high-density lipoprotein (HDL)-cholesterol levels were borderline predictive in men; smoking status and HDL-and low-density lipoprotein (LDL)-cholesterol levels were not predictive in women. Age, presence of diabetes, systolic blood pressure and C-reactive protein (CRP) were predictors in both sexes, while smoking status and LDL-cholesterol were so in men only. AROC of the model was 0.789 in men, and 0.806 in women (p < 0.001 each). An algorithm using the stated seven variables was derived separately for each sex. After age adjustment, men and women in the highest quintile of risk score were significantly and 20-27-fold more likely to develop CHD than those in the lowest quintile.

CONCLUSIONS

In a population with prevalent MetS, low-grade inflammation is independently relevant for CHD, as are serum lipoproteins and smoking status. The derived algorithm is effective in estimating CHD risk among Turkish adults.

Apolipoprotein E predicts incident cardiovascular disease risk in women but not in men with concurrently high levels of high-density lipoprotein cholesterol and C-reactive protein

Although there is great interest in the notion that dysfunctional transformation of high-density lipoprotein (HDL) facilitates development of atherosclerosis and cardiovascular disease (CVD), few studies in human populations directly address this issue. As apolipoprotein E (apoE) is a constituent of HDL thought to be important for HDL antiatherogenic function, we sought to assess the role of apoE in CVD risk in subjects likely to display dysfunctional transformation of HDL. Association of apoE levels with incident CVD risk was investigated using Cox multivariable proportional hazards modeling. Analyses were performed in subgroups of women and men likely to display dysfunctional transformation of HDL deriving from previous subgroup identification based upon defining characteristics of concurrently high levels of HDL cholesterol and systemic inflammation as reflected by high C-reactive protein levels. Results revealed apoE levels (dichotomized as highest quartile vs combined 3 lowest quartiles) as predicting subgroup risk in women (hazard ratio, 4.52; 95% confidence interval, 1.07-19.12; P = .040) but not in men. Further sex differences were manifested in terms of the relationship of apoE levels with age. Analysis revealed positive correlation of apoE levels with age in women (r = 0.47, P < .0001) but not in men (r = 0.04, P = .43). Apolipoprotein E levels predict incident CVD risk in women with high levels of HDL cholesterol and C-reactive protein but not in men. Future studies should be oriented toward investigations of apoE as related to multiplicity of HDL functionality and toward assessment of potential roles for apoE in dysfunctional transformation of HDL.

In vivo human apolipoprotein E isoform fractional turnover rates in the CNS

Apolipoprotein E (ApoE) is the strongest genetic risk factor for Alzheimer's disease and has been implicated in the risk for other neurological disorders. The three common ApoE isoforms (ApoE2, E3, and E4) each differ by a single amino acid, with ApoE4 increasing and ApoE2 decreasing the risk of Alzheimer's disease (AD). Both the isoform and amount of ApoE in the brain modulate AD pathology by altering the extent of amyloid beta (Aβ) peptide deposition. Therefore, quantifying ApoE isoform production and clearance rates may advance our understanding of the role of ApoE in health and disease. To measure the kinetics of ApoE in the central nervous system (CNS), we applied in vivo stable isotope labeling to quantify the fractional turnover rates of ApoE isoforms in 18 cognitively-normal adults and in ApoE3 and ApoE4 targeted-replacement mice. No isoform-specific differences in CNS ApoE3 and ApoE4 turnover rates were observed when measured in human CSF or mouse brain. However, CNS and peripheral ApoE isoform turnover rates differed substantially, which is consistent with previous reports and suggests that the pathways responsible for ApoE metabolism are different in the CNS and the periphery. We also demonstrate a slower turnover rate for CSF ApoE than that for amyloid beta, another molecule critically important in AD pathogenesis.

ApoE genotype: from geographic distribution to function and responsiveness to dietary factors

ApoE is a key protein in lipid metabolism with three major isoforms.ApoEallele frequencies show non-random global distribution especially in Europe with highapoEε3frequency in the Mediterranean area, whereas theapoEε4genotype is enriched in Northern Europe. TheapoEε4genotype is one of the most important genetic risk factors for age-dependent chronic diseases, including CVD and Alzheimer's disease (AD). The apoE polymorphism has been shown to impact on blood lipids, biomarkers of oxidative stress and chronic inflammation, which all may contribute to the isoform-dependent disease risk. Studies in mice and human subjects indicate that theapoEε3but not theapoEε4genotype may significantly benefit from dietary flavonoids (e.g. quercetin) andn-3 fatty acids. Metabolism of lipid soluble vitamins E and D is likewise differentially affected by theapoEgenotype. Epidemiological and experimental evidence suggest a better vitamin D status inapoEε4than ε3subjects indicating a certain advantage of ε4over ε3. The present review aims at evaluation of current data available on interactions between apoE polymorphism and dietary responsiveness to flavonoids, fat soluble vitamins andn-3 fatty acids. Likewise, distinct geographic distribution and chronic disease risk of the different apoE isoforms are addressed.

Targeted In Situ Gene Correction of Dysfunctional APOE Alleles to Produce Atheroprotective Plasma ApoE3 Protein

Cardiovascular disease is the leading worldwide cause of death. Apolipoprotein E (ApoE) is a 34-kDa circulating glycoprotein, secreted by the liver and macrophages with pleiotropic antiatherogenic functions and hence a candidate to treat hypercholesterolaemia and atherosclerosis. Here, we describe atheroprotective properties of ApoE, though also potential proatherogenic actions, and the prevalence of dysfunctional isoforms, outline conventional gene transfer strategies, and then focus on gene correction therapeutics that can repair defective APOE alleles. In particular, we discuss the possibility and potential benefit of applying in combination two technical advances to repair aberrant APOE genes: (i) an engineered endonuclease to introduce a double-strand break (DSB) in exon 4, which contains the common, but dysfunctional, ε2 and ε4 alleles; (ii) an efficient and selectable template for homologous recombination (HR) repair, namely, an adeno-associated viral (AAV) vector, which harbours wild-type APOE sequence. This technology is applicable ex vivo, for example to target haematopoietic or induced pluripotent stem cells, and also for in vivo hepatic gene targeting. It is to be hoped that such emerging technology will eventually translate to patient therapy to reduce CVD risk.

HDL Mimetic Peptide Administration Improves Left Ventricular Filling and Cardiac output in Lipopolysaccharide-Treated Rats

AIMS: Cardiac dysfunction is a complication of sepsis and contributes to morbidity and mortality. Since raising plasma apolipoprotein (apo) A-I and high density lipoprotein (HDL) concentration reduces sepsis complications, we tested the hypothesis that the apoA-I mimetic peptide 4F confers similar protective effects in rats treated with lipopolysaccharide (LPS). METHODS AND RESULTS: Male Sprague-Dawley (SD) rats were randomized to receive saline vehicle (n=13), LPS (10 mg/kg: n=16) or LPS plus 4F (10 mg/kg each: n=13) by intraperitoneal injection. Plasma cytokine and chemokine levels were significantly elevated 24 hrs after LPS administration. Echocardiographic studies revealed changes in cardiac dimensions that resulted in a reduction in left ventricular end-diastolic volume (LVEDV), stroke volume (SV) and cardiac output (CO) 24 hrs after LPS administration. 4F treatment reduced plasma levels of inflammatory mediators and increased LV filling, resulting in improved cardiac performance. Chromatographic separation of lipoproteins from plasma of vehicle, LPS and LPS+4F rats revealed similar profiles. Further analyses showed that LPS treatment reduced the agarose electrophoretic mobility of isolated HDL fractions. HDL-associated proteins were characterized by SDSPAGE and mass spectrometry. ApoA-I and apoA-IV were reduced while apoE content was increased in LPStreated rats. 4F treatment in vivo attenuated changes in HDL-associated apolipoproteins and increased the electrophoretic mobility of the particle. CONCLUSIONS: The ability of 4F to reduce inflammation and improve cardiac performance in LPS-treated rats may be due to its capacity to neutralize endotoxin and prevent adverse changes in HDL composition and function.

Apolipoproteins: metabolic role and clinical biochemistry applications

Lipoprotein metabolism is dependent on apolipoproteins, multifunctional proteins that serve as templates for the assembly of lipoprotein particles, maintain their structure and direct their metabolism through binding to membrane receptors and regulation of enzyme activity. The three principal functions of lipoproteins are contribution to interorgan fuel (triglyceride) distribution (by means of the fuel transport pathway), to the maintenance of the extracellular cholesterol pool (by means of the overflow pathway) and reverse cholesterol transport. The most important clinical application of apolipoprotein measurements in the plasma is in the assessment of cardiovascular risk. Concentrations of apolipoprotein B and apolipoprotein AI (and their ratio) seem to be better markers of cardiovascular risk than conventional markers such as total cholesterol and LDL-cholesterol. Apolipoprotein measurements are also better standardized than the conventional tests. We suggest that measurements of apolipoprotein AI and apolipoprotein B are included as a part of the specialist lipid profile. We also suggest that lipoprotein (a) should be measured as part of the initial assessment of dyslipidaemias because of its consistent association with cardiovascular risk. Genotyping of apolipoprotein E isoforms remains useful in the investigation of mixed dyslipidaemias. Lastly, the role of postprandial metabolism is increasingly recognized in the context of atherogenesis, obesity and diabetes. This requires better markers of chylomicrons, very-low-density lipoproteins and remnant particles. Measurements of apolipoprotein B48 and remnant lipoprotein cholesterol are currently the key tests in this emerging field.

A QTL for genotype by sex interaction for anthropometric measurements in Alaskan Eskimos (GOCADAN Study) on chromosome 19q12-13

Variation in anthropometric measurements due to sexual dimorphism can be the result of genotype by sex interactions (G×S). The purpose of this study was to examine the sex-specific genetic architecture in anthropometric measurements in Alaskan Eskimos from the Genetics of Coronary Artery Disease in Alaska Natives (GOCADAN) study. Maximum likelihood-based variance components decomposition methods, implemented in SOLAR, were used for G×S analyses. Anthropometric measurements included BMI, waist circumference (WC), waist/height ratio, percent body fat (%BF), and subscapular and triceps skinfolds. Except for WC, mean values of all phenotypes were significantly different in men and women (P < 0.05). All anthropometric measures were significantly heritable (P < 0.001). In a preliminary analysis not allowing for G×S interaction, evidence of linkage was detected between markers D19S414 and D19S220 on chromosome 19 for WC (logarithm of odds (lod) = 3.5), %BF (lod = 1.7), BMI (lod = 2.4), waist/height ratio (lod = 2.5), subscapular (lod = 2.1), and triceps skinfolds (lod = 1.9). In subsequent analyses which allowed for G×S interaction, linkage was again found between these traits and the same two markers on chromosome 19 with significantly improved lod scores for: WC (lod = 4.5), %BF (lod = 3.8), BMI (lod = 3.5), waist/height ratio (lod = 3.2), subscapular (lod = 3.0), and triceps skinfolds (lod = 2.9). These results support the evidence of a G×S interaction in the expression of genetic effects resulting in sexual dimorphism in anthropometric phenotypes and identify the chromosome 19q12-13 region as important for adiposity-related traits in Alaskan Eskimos.

Genome-wide association study identifies a single major locus contributing to survival into old age; the APOE locus revisited

By studying the loci that contribute to human longevity, we aim to identify mechanisms that contribute to healthy aging. To identify such loci, we performed a genome-wide association study (GWAS) comparing 403 unrelated nonagenarians from long-living families included in the Leiden Longevity Study (LLS) and 1670 younger population controls. The strongest candidate SNPs from this GWAS have been analyzed in a meta-analysis of nonagenarian cases from the Rotterdam Study, Leiden 85-plus study, and Danish 1905 cohort. Only one of the 62 prioritized SNPs from the GWAS analysis (P < 1 × 10⁻⁴) showed genome-wide significance with survival into old age in the meta-analysis of 4149 nonagenarian cases and 7582 younger controls [OR = 0.71 (95% CI 0.65–0.77), P = 3.39 × 10⁻¹⁷]. This SNP, rs2075650, is located in TOMM40 at chromosome 19q13.32 close to the apolipoprotein E (APOE) gene. Although there was only moderate linkage disequilibrium between rs2075650 and the ApoE ε4 defining SNP rs429358, we could not find an APOE-independent effect of rs2075650 on longevity, either in cross-sectional or in longitudinal analyses. As expected, rs429358 associated with metabolic phenotypes in the offspring of the nonagenarian cases from the LLS and their partners. In addition, we observed a novel association between this locus and serum levels of IGF-1 in women (P = 0.005). In conclusion, the major locus determining familial longevity up to high age as detected by GWAS was marked by rs2075650, which tags the deleterious effects of the ApoE ε4 allele. No other major longevity locus was found.

Lipid metabolism in long-lived families: the Leiden Longevity Study

Mechanisms underlying the variation in human life expectancy are largely unknown, but lipid metabolism and especially lipoprotein size was suggested to play an important role in longevity. We have performed comprehensive lipid phenotyping in the Leiden Longevity Study (LLS). By applying multiple logistic regression analysis we tested for the first time the effects of parameters in lipid metabolism (i.e., classical serum lipids, lipoprotein particle sizes, and apolipoprotein E levels) on longevity independent of each other. Parameters in lipid metabolism were measured in offspring of nonagenarian siblings from 421 families of the LLS (n = 1,664; mean age, 59 years) and in the partners of the offspring as population controls (n = 711; mean age, 60 years). In the initial model, where lipoprotein particles sizes, classical serum lipids and apolipoprotein E were included, offspring had larger low-density lipoprotein (LDL) particle sizes (p = 0.017), and lower triglyceride levels (p = 0.026), indicating that they displayed a more beneficial lipid profile. After backwards regression only LDL size (p = 0.014) and triglyceride levels (p = 0.05) were associated with offspring from long-lived families. Sex-specific backwards regression analysis revealed that LDL particle sizes were associated with male longevity (increase in log odds ratio (OR) per unit = 0.21; p = 0.023). Triglyceride levels (decrease OR per unit = 0.22; p = 0.01), but not LDL particle size, were associated with female longevity. Due to the analysis of a comprehensive lipid profile, we confirmed an important role of lipid metabolism in human longevity, with LDL size and triglyceride levels as major predicting factors.

The APOE -219G/T and +113G/C polymorphisms affect insulin resistance among Turks

The -219G/T (rs405509) and +113G/C (rs440446) polymorphisms within the regulatory region of the apolipoprotein E (APOE) gene have been related to the transcriptional activity of the gene. We examined the effect of the stated polymorphisms and their construct haplotypes with the APOE ɛ2/ɛ3/ɛ4 polymorphism on lipid levels and insulin resistance in the Turkish Adult Risk Factor Study. Randomly selected 1774 adults (mean age, 55.0 ± 11.7 years; 51.2% women) participating in the population-based Turkish Adult Risk Factor Study were cross-sectionally analyzed for the -219G/T, +113G/C, and ɛ2/ɛ3/ɛ4 polymorphisms as well as their haplotypes. Insulin resistance was defined as the 70th percentile in the sample (>2.51) of the homeostatic model assessment (HOMA). The frequencies of the -219T and +113C alleles were 0.477 and 0.423, respectively; and those of haplotype 1 (GGɛ3) and haplotype 2 (TCɛ3) were 44.1% and 41.9%, respectively. The -219G/T and +113G/C genotypes (both P < .04) and diplotypes of haplotype 2 (TCɛ3) (P < .014) were inversely related to serum fasting insulin and the HOMA index, even after controlling for 8 relevant covariates, but not to serum lipids. Within the APOE3 group, haplotype 2 (TC-/TC+) heterozygotes had an odds ratio of 0.66 (95% confidence interval, 0.42-0.99) for HOMA of insulin resistance after adjusting for 8 covariates. APOE promoter polymorphisms and their diplotypes are independently related with serum fasting insulin levels and HOMA index among Turks.

Apolipoprotein E epsilon-4 polymorphism is associated with younger age at referral to a lipidology clinic and a poorer response to lipid-lowering therapy

Background

The risk of coronary heart disease (CHD) is related to environmental factors and genetic variants. Apolipoprotein E (apoE) polymorphisms are heritable determinants of total and low-density lipoprotein cholesterol, with some authors suggesting an association between the ε4 allele and CHD. We investigated the relationship between apoE genotype and age at referral to a specialized lipid clinic by the primary care physician and whether the benefits of treatment with statin differed between genotypes.

Methods

We assessed individual apoE genotypes and lipid blood profile in a total of 463 patients followed at a specialized lipid clinic due to dyslipidemia, with a 3-year median follow-up time. The primary care physician at the time of the referral had no access to the apoE genotyping results. Carriers of apoE ε4/ε2 genotype were excluded.

Results

The frequencies of ε2, ε3 and ε4 alleles were 7.8, 78.9 and 13.3%, respectively. There were no significant differences between genders. Although with similar lipid profiles and antidyslipidemic drug usage at baseline, ε4-carriers were referred to the clinic at a younger age (44.2 ± 14.7 years) compared with non-ε4 carriers (50.6 ± 13.8 years) (p < 0.001), with a substantially younger age of referral for homozygous E4/4 and for all genotypes with at least one copy of the ε4 allele (p < 0.001 for trend). Although both ε4 and non-ε4 carriers achieved significant reductions in total cholesterol during follow-up (p < 0.001 vs. baseline), the mean relative decrease in total cholesterol levels was higher in non-ε4 carriers (-19.9 ± 2.3%) compared with ε4 carriers (-11.8 ± 2.3%), p = 0.003.

Conclusion

Our findings support the concept that there is a reduced response to anti-dyslipidemic treatment in ε4 carriers; this can be a contributing factor for the earlier referral of these patients to our specialized lipid clinic and reinforces the usefulness of apoE genotyping in predicting patients response to lipid lowering therapies.

Complement C3 and cleavage products in cardiometabolic risk

This review summarizes available evidence on the role of serum complement component 3 (C3), produced by liver, adipocytes and activated macrophages at inflammation sites, and C3 cleavage products linking lipoproteins and metabolism to immunity. C3 and cleavage products are modified in several associated metabolic disorders including obesity, insulin resistance, type-2 diabetes, dyslipidemia, and cardiovascular diseases. Circulating C3 is independently and linearly associated with serum triglycerides, C-reactive protein (CRP), waist circumference and in some populations inversely with current smoking. The complement cascade is activated during myocardial ischemia and likely mediates immune and inflammatory responses in ischemic myocardium. Serum complement activation is elevated in unstable rather than stable angina pectoris suggesting added contribution to damage extension in acute coronary syndromes. In logistic regression models for incident metabolic syndrome (MetS), increasing C3 concentrations predicted MetS in women, after adjusting for continuous values of 3 major MetS components and other confounders, with a relative risk similar in magnitude to an established component suggesting elevated C3 likely constitutes part of the cluster of MetS in women. C3 interacts with MetS in men for independently conferring risk of incident type-2 diabetes and coronary heart disease (CHD). In women, though C3 is equally predictive of cardiometabolic risk, it is less so additively to MetS components or to CRP. Evidence suggests that circulating C3 might serve as a signal for an immune process that enhances - via mediation of increased apolipoprotein (apo) E levels - the development of dysfunctional apoA-I particles rendering them diabetogenic and atherogenic in populations prone to MetS or subsets of populations harboring impaired glucose tolerance. C3 activation also leads to production of chemoattractants C3a and C5a, and acylation stimulating protein (ASP, C3adesArg), a lipogenic hormone, which contribute additionally to the metabolic phenotypes generated. These observations have clinical and public health implications.

Imbalance of peroxisome proliferator-activated receptor gamma and adiponectin predisposes Kawasaki disease patients to developing atherosclerosis

BACKGROUND

It remains controversial whether Kawasaki disease (KD) is a risk factor for the onset of atherosclerosis. An imbalance of peroxisome proliferator-activated receptor γ (PPARγ) and adiponectin appears to play a role in the onset of atherosclerosis in adults, and we therefore examined PPARγ mRNA expression and adiponectin profiles in the peripheral white blood cells obtained from KD patients.

METHODS

A total of 50 subjects were studied: nine patients with acute KD, 20 patients with convalescent KD, and 21 age-matched controls. The gene expression of PPARγ, monocyte chemoattractant protein-1, and CC chemokine receptor 2 present in the blood were quantified. The relative gene expression, adiponectin levels, and the three adiponectin isoforms were compared among the subjects.

RESULTS

The abundance of PPARγ and CC chemokine receptor 2 mRNA was significantly increased in convalescent KD patients. The monocyte chemoattractant protein-1 level was also increased in convalescent KD patients. The level of high-molecular-weight adiponectin was significantly lower in convalescent patients compared to controls. The PPARγ transcription levels negatively correlated with apolipoprotein A-I levels in acute KD patients.

CONCLUSIONS

The transcript abundance of PPARγ and low levels of high-molecular-weight adiponectin in KD patients may have important clinical implications on the development of premature atherosclerosis. Because the potential risk for developing atherosclerosis has not yet been verified, long-term observation is important, even in convalescent KD patients without coronary artery lesions.

Apolipoprotein E-related all-cause mortality in hospitalized elderly patients

The most common apolipoprotein E (APOE) allelic variation is implicated in many age-related diseases and human longevity with controversial findings. We investigated the effect of APOE gene polymorphism on all-cause mortality in elderly patients taking into consideration the functional disability, cognitive impairment, malnutrition, and the occurrence of common age-related diseases. APOE genotypes were determined in 2,124 geriatric hospitalized patients (46.5% men and 53.5% women; mean age, 78.2 +/- 7.1 years; range, 65-100 years). At hospital admission, all patients underwent a comprehensive geriatric assessment to evaluate functional disability, cognitive status, nutritional status, and comorbidity. The main and secondary diagnoses at hospital discharge were also recorded. Mortality status was evaluated in all patients after a maximum follow-up of 5 years (range, from 1.26 to 5.23 years; median, 2.86 years). During the study period, 671 patients died (32.0%). At hospital admission, these patients showed a significant higher prevalence of cardiovascular diseases (56.3% vs 53.4%; p = 0.007), neoplasias (32.3% vs 13.7%; p < 0.001), and lower prevalence of neurodegenerative diseases (17.7% vs 20.7%; p < 0.001) than survived patients. Moreover, they also showed an higher prevalence of disability (52.0% vs 25.6%; p < 0.001), cognitive impairment (31.0% vs 18.8%; p < 0.001), and malnutrition (74.0% vs 46.1%; p < 0.001) than survived patients. In the overall study population, the APOE epsilon2 allele was significantly associated to neurodegenerative diseases (odds ratio = 0.59; 95% confidence interval (CI), 0.37-0.94). No significant association between the APOE polymorphism and disability, malnutrition, co-morbidity status, and with all-cause mortality was observed. In patients with cardiovascular diseases, however, a decreased risk of all-cause mortality was found in the epsilon2 allele carriers (hazard ratio = 0.56; 95% CI, 0.36-0.88). In this population, APOE allele variants might play a role on cardiovascular disease-related mortality.

Apolipoprotein E Genotype and Cardiovascular Diseases in the Elderly

The apolipoprotein E (APOE) genotype is a genetic risk factor for dementia, Alzheimer’s disease, and cardiovascular disease (CVD). It includes three alleles (e2, e3, e4) that are located on chromosome 19q3.2. The e3 allele is the most common and is more common in people of Northern European ancestry and less common in those of Asian ancestry. Those with at least one e4 allele are at increased risk for CVD outcomes. It is well established that the presence of an e4 allele is linked to higher low-density lipoprotein cholesterol levels, even at young ages. Even though most CVD occurs in older people, there are few studies of the effects of APOE on CVD in older people. This review addresses recent research on the links between APOE, CVD, and vascular mechanisms by which APOE may affect CVD in the elderly.

Glycosylation and sialylation of macrophage-derived human apolipoprotein E analyzed by SDS-PAGE and mass spectrometry: evidence for a novel site of glycosylation on Ser290

Apolipoprotein E (apoE) is a 34-kDa glycoprotein secreted from various cells including hepatocytes and macrophages and plays an important role in remnant lipoprotein clearance, immune responses, Alzheimer disease, and atherosclerosis. Cellular apoE and plasma apoE exist as multiple glycosylated and sialylated glycoforms with plasma apoE being less glycosylated/sialylated than cell-derived apoE. Some of the glycan structures on plasma apoE are characterized; however, the more complicated structures on plasma and cellular/secreted apoE remain unidentified. We investigated glycosylation and sialylation of cellular and secreted apoE from primary human macrophages by one- and two-dimensional gel electrophoresis and mass spectrometry. Our results identify eight different glycoforms with (HexNAc)(2)-Hex(2)-(NeuAc)(2) being the most complex glycan detected on Thr(194) in both cellular and secreted apoE. Four additional glycans were identified on apoE(283-299), and using beta-elimination/alkylation by methylamine in vitro, we identified Ser(290) as a novel site of glycan attachment. Comparison of plasma and cellular/secreted apoE from the same donor confirmed that cell-derived apoE is more extensively sialylated than plasma apoE. Given the importance of the C terminus of apoE in regulating apoE solubility, stability, and lipid binding, these results may have important implications for our understanding of apoE biochemistry.

APOE polymorphism and its effect on plasma C-reactive protein levels in a large general population sample

The published data remain inconsistent on association between apolipoprotein E (APOE) gene variations and plasma levels of C-reactive protein (CRP), mainly because of low statistical power of previous studies. To clarify this question, we analyzed data from large population sample of randomly selected individuals from seven Czech towns (2,886 males and 3,344 females, the HAPIEE [Health, Alcohol, and Psychosocial factors In Eastern Europe] study). In both males and females, the lowest levels of plasma hsCRP were observed in the carriers of the APOE epsilon 4 epsilon 4 and epsilon 4 epsilon 3 genotypes. The median (interquartile range, IQR) concentration of hsCRP in carriers of the most common APOE epsilon 3 epsilon 3 genotype (two-thirds of participants) was 1.13 mg/l (IQR, 0.56-2.33) in men and 1.23 mg/l (IQR, 0.61-2.65) in women, compared with 0.72 mg/l (IQR, 0.61-0.86) in male and 0.72 mg/l (IQR, 0.61-0.85) in female carriers of APOE epsilon 4 epsilon 3/epsilon 4 epsilon 4 genotypes; the differences were statistically significant (p < 0.001). The association between APOE and CRP was not materially affected by adjustment for age, sex, history of cardiovascular disease, or cardiovascular risk factors. This study, the largest to date, provides robust evidence of an association between plasma hsCRP and the APOE genotype, an association not explained by history of cardiovascular disease nor its risk factors.

Parental history of Alzheimer disease associated with lower plasma apolipoprotein E levels

BACKGROUND

Variation in APOE genotype is a determinant of Alzheimer disease (AD), but the risk associated with variation in plasma apoE levels has yet to be determined. Here, we studied offspring with and without a parental history of AD to identify the effect of plasma apoE levels at middle age on the risk of late-onset AD.

METHODS

Some 203 offspring from 92 families with a parental history of AD were compared with 197 offspring from 97 families without a parental history of AD. APOE genotypes and plasma apoE levels were assessed in all offspring. Difference in plasma apoE level between subjects with and without a parental history of AD was calculated using robust linear regression, both stratified and adjusted for APOE genotype.

RESULTS

Offspring with a parental history of AD were more likely to be an APOE epsilon4 allele carrier (46% vs 21%, p < 0.001) than offspring without such a parental history. Mean plasma apoE levels strongly decreased from epsilon2 to epsilon3epsilon3 to epsilon4 carriers (p < 0.001). Offspring with a parental history of AD had lower plasma apoE levels than subjects without such a history, both in analyses adjusted for APOE genotype (difference: -0.21 mg/dL, p = 0.02) and when using standardized Z scores, when stratified for APOE genotype (difference: -0.22, p = 0.009).

CONCLUSIONS

Our findings suggest that lower plasma apoE levels in middle age could be a risk factor for Alzheimer disease in old age, independent of APOE genotype.

Comparative study of apolipoprotein-E polymorphism and plasma lipid levels in dyslipidemic and asymptomatic subjects, and their implication in cardio/cerebro-vascular disorders

Polymorphisms in the apolipoprotein-E (apoE) gene may modulate lipoprotein metabolism at different steps and influence total and low density lipoprotein (LDL) cholesterol (LDLc) levels, as well as other lipid features. Population studies have documented significant differences in the frequency of apoE alleles which are related to the prevalence of various cardio-vascular and neuro-psychiatric diseases. In this study, the apoE genotypes and allele frequencies were analyzed in 216 individuals (109 dyslipidemic and 107 normo-lipidic subjects), and the relative contribution of apoE polymorphism on plasma lipid and lipoprotein levels, as well as risk factors was evaluated. In normo-lipidic volunteers, the frequencies of epsilon2, epsilon3 and epsilon4 alleles were 0.042, 0.832 and 0.126, while in dyslipidemic subjects 0.046, 0.835 and 0.119, respectively. No significant difference was observed among epsilon2, epsilon3 or epsilon4 and plasma lipid-lipoprotein levels in the dyslipidemic group. In normo-lipidemics, however, total cholesterol, LDLc and non-HDLc plasma levels were significantly lower in epsilon2 subjects when compared to epsilon3 and epsilon4 individuals. The allelic frequencies of apoE epsilon2, epsilon3 and epsilon4 were similar in dyslipidemic and normo-lipemic subjects, suggesting that apoE polymorphisms have no effect on plasma lipid-lipoprotein levels in dyslipidemic subjects. In contrast, in normo-lipemic subjects the epsilon2 allele showed to be associated with lower total cholesterol and LDLc levels, the mark of a better lipid profile. Depending on other co-existing factors, the epsilon2 allele, therefore, may play either a protective or pathogenic role. This elementary knowledge is a fundamental prerequisite for a possible diagnostic application of these lipoproteins as biomarkers to predict adverse cardio-vascular and/or neuro-psychiatric maladies.

The role of apolipoprotein E in Alzheimer's disease

The epsilon4 allele of apolipoprotein E (APOE) is the major genetic risk factor for Alzheimer's disease (AD). Although there have been numerous studies attempting to elucidate the underlying mechanism for this increased risk, how apoE4 influences AD onset and progression has yet to be proven. However, prevailing evidence suggests that the differential effects of apoE isoforms on Abeta aggregation and clearance play the major role in AD pathogenesis. Other potential mechanisms, such as the differential modulation of neurotoxicity and tau phosphorylation by apoE isoforms as well as its role in synaptic plasticity and neuroinflammation, have not been ruled out. Inconsistent results among studies have made it difficult to define whether the APOE epsilon4 allele represents a gain of toxic function, a loss of neuroprotective function, or both. Therapeutic strategies based on apoE propose to reduce the toxic effects of apoE4 or to restore the physiological, protective functions of apoE.

HDL-ApoE content regulates the displacement of hepatic lipase from cell surface proteoglycans

Human hepatic lipase (HL) is an interfacial enzyme that must be liberated from cell surface proteoglycans to hydrolyze lipoprotein triglyceride. Both high-density lipoprotein (HDL) and apolipoprotein (apo)A-I can displace HL from cell surface proteoglycans, much like heparin. HL displacement is inhibited by HDL-apoE content. Postprandial HDL is approximately twofold better at displacing HL than is fasting HDL, but only has approximately one-half the apoE content. Enriching native HDL with triglyceride decreases HDL-apoE content and increases HL displacement. Incubation of HDL with the anti-apoE antibody, 6C5, also increases HL displacement. In contrast, enrichment of synthetic HDL with apoE significantly inhibits HL displacement. HDL from fasted female normolipidemic subjects displaces HL approximately twofold better than HDL from male subjects. HDL from female subjects also has significantly less apoE than HDL from males. Normolipidemic females have increased circulating HDL-bound HL. Hyperlipidemia has little effect on the HL displacement ability of HDL from men, whereas HDL from hypercholesterolemic females exhibits impaired HL displacement. HL displacement from liver heparan sulfate proteoglycans therefore appears to be linked to interlipoprotein apoE exchange. Decreased HL displacement is associated with higher HDL-apoE levels and may therefore affect vascular triglyceride hydrolysis.

Additive effect of LRP8/APOER2 R952Q variant to APOE epsilon2/epsilon3/epsilon4 genotype in modulating apolipoprotein E concentration and the risk of myocardial infarction: a case-control study

BACKGROUND

The R952Q variant in the low density lipoprotein receptor-related protein 8 (LRP8)/apolipoprotein E receptor 2 (ApoER2) gene has been recently associated with familial and premature myocardial infarction (MI) by means of genome-wide linkage scan/association studies. We were interested in the possible interaction of the R952Q variant with another established cardiovascular genetic risk factor belonging to the same pathway, namely apolipoprotein E (APOE) epsilon2/epsilon3/epsilon4 genotype, in modulating apolipoprotein E (ApoE) plasma levels and risk of MI.

METHODS

In the Italian cohort used to confirm the association of the R952Q variant with MI, we assessed lipid profile, apolipoprotein concentrations, and APOE epsilon2/epsilon3/epsilon4 genotype. Complete data were available for a total of 681 subjects in a case-control setting (287 controls and 394 patients with MI).

RESULTS

Plasma ApoE levels decreased progressively across R952Q genotypes (mean levels +/- SD = RR: 0.045 +/- 0.020, RQ: 0.044 +/- 0.014, QQ: 0.040 +/- 0.008 g/l; P for trend = 0.047). Combination with APOE genotypes revealed an additive effect on ApoE levels, with the highest level observed in RR/non-carriers of the E4 allele (0.046 +/- 0.021 g/l), and the lowest level in QQ/E4 carriers (0.035 +/- 0.009 g/l; P for trend = 0.010). QQ/E4 was also the combined genotype with the most significant association with MI (OR 3.88 with 95%CI 1.08-13.9 as compared with RR/non-carriers E4).

CONCLUSION

Our data suggest that LRP8 R952Q variant may have an additive effect to APOE epsilon2/epsilon3/epsilon4 genotype in determining ApoE concentrations and risk of MI in an Italian population.

Pharmacogenetics of apolipoprotein E gene during lipid-lowering therapy: lipid levels and prevention of coronary heart disease

A non-optimal plasma concentration of lipids is among the major modifiable risk factors of atherosclerosis. Therefore, the prevention of cardiovascular disease by means of lipid-lowering therapy with statins and other agents is of great importance for patient groups where a lifestyle change, for example, diet modification, does not lead to adequately reduced lipid levels. The response of low-density-lipoprotein cholesterol (LDL-C) levels to statin therapy is highly variable. This is partly attributed to hereditary variation in genes involved in pharmacokinetics, pharmacodynamics and lipid metabolism. The pharmacogenetics of lipid-lowering therapy have been investigated for more than 40 different genes. The gene for apolipoprotein E (APOE) has been the most frequently studied, particularly regarding the epsilon2/epsilon3/epsilon4 polymorphism. Those with the epsilon4 allele seem to have the poorest and those with the epsilon2 allele the strongest response to statins with regards to LDL-C levels. In addition, the epsilon2 carriers may reach the LDL-C treatment goals more frequently than epsilon4 carriers. Few studies have investigated the interaction of the APOE epsilon2/epsilon3/epsilon4 polymorphism and lipid-lowering therapy in relation to the course of coronary heart disease; the results are contradictory and so far inconclusive. This review summarizes the pharmacogenetic findings related to the influence of APOE gene variation on lipid responses and the prevention of coronary heart disease during lipid-lowering therapy.

Genes encoding longevity: from model organisms to humans

Ample evidence from model organisms has indicated that subtle variation in genes can dramatically influence lifespan. The key genes and molecular pathways that have been identified so far encode for metabolism, maintenance and repair mechanisms that minimize age-related accumulation of permanent damage. Here, we describe the evolutionary conserved genes that are involved in lifespan regulation of model organisms and humans, and explore the reasons of discrepancies that exist between the results found in the various species. In general, the accumulated data have revealed that when moving up the evolutionary ladder, together with an increase of genome complexity, the impact of candidate genes on lifespan becomes smaller. The presence of genetic networks makes it more likely to expect impact of variation in several interacting genes to affect lifespan in humans. Extrapolation of findings from experimental models to humans is further complicated as phenotypes are critically dependent on the setting in which genes are expressed, while laboratory conditions and modern environments are markedly dissimilar. Finally, currently used methodologies may have only little power and validity to reveal genetic variation in the population. In conclusion, although the study of model organisms has revealed potential candidate genetic mechanisms determining aging and lifespan, to what extent they explain variation in human populations is still uncertain.

Associations of apolipoprotein E gene with ischemic stroke and intracranial atherosclerosis

The apolipoprotein E (APOE) epsilon4 allele is associated with elevated cholesterol and risk of atherosclerosis. However, its role in ischemic stroke (IS) remains controversial. We investigated a possible link between IS or the severity of intracranial atherosclerosis and the APOE promoter polymorphisms -219G/T and +113G/C, involved in regulating APOE transcription. We genotyped subjects from a multicentric Belgian case-control study, including 237 middle-aged patients with IS due to small- or large-vessel atherosclerotic stroke and 326 ethnicity- and gender-matched controls and a Finnish autopsy series of 1004 non-stroke cases, who had received a quantitative score of atherosclerosis in the circle of Willis. The APOE epsilon4+ genotype did not associate with IS, but was related to more severe intracranial atherosclerosis score in men (5.4 vs 4.6, P=0.044). Within the most common APOE epsilon3/epsilon3 genotype group, the risk of IS associated with the G-allele of the tightly linked -219G/T (OR=6.2; 95% CI: 1.6-24.3, P=0.009) and +113G/C (OR=7.1; 95% CI: 1.7-29.9, P=0.007) promoter polymorphisms. There was no difference in the severity of intracranial atherosclerosis between -219G/G genotype carriers and non-carriers. This study suggests a multifaceted role of apoE on the risk of cerebrovascular diseases. The APOE epsilon4+ genotype did not predict the risk of IS but was associated with severity of subclinical intracranial atherosclerosis in men on the autopsy study. In contrast, the promoter variants were significant predictors of IS, suggesting that quantitative rather than qualitative variation of apoE is related to IS.

Lipoproteins, vascular-related genetic factors, and human longevity

The relationships among lipoprotein metabolism, genetic vascular factors, vascular disease, and Alzheimer's disease suggest that the examination of centenarian populations in relation to certain genes or lipoprotein metabolism provide insights into human longevity. The findings on the higher frequency of the apolipoprotein E epsilon4 allele in middle-aged subjects than in centenarians were substantially confirmed. On the contrary, recent findings did not confirm previous data on increased prevalence of the high-risk angiotensin I converting enzyme D allele in French centenarians. The variability in the strength of association between angiotensin I converting enzyme polymorphism and longevity could be related to regional differences in angiotensin I converting enzyme D allele frequency in Europe recently showed, as also recently reported for apolipoprotein Eepsilon2 and epsilon4 allele in centenarians. Indeed some studies of lipoprotein profiles in centenarians have also had contradictory outcomes, with evidence of lower serum levels of high-density lipoprotein cholesterol, with higher high-density lipoprotein 2 cholesterol subfraction, larger high-density lipoprotein and low-density lipoprotein particle sizes, and higher lipoprotein(a) concentration in centenarians, which is apparently disadvantageous for human longevity. Elevated lipoprotein(a) serum levels, increasing the risk for cerebrovascular disease, may play a role in determining clinical Alzheimer's disease, but lipoprotein(a) elevation in centenarians, in the absence of other coronary artery disease risk factors, appears as a positive survival factor. In different populations, there are significant trends in the reduction of serum apolipoprotein E levels from apolipoprotein E epsilon2- to epsilon4-carriers and significant differences in serum apolipoprotein E levels with respect to age in epsilon4-carriers but only after adjustment for high-density lipoprotein cholesterol. While further studies are needed to confirm the possible role of apolipoprotein E concentration as putative longevity factor this paper provides an overview of many of the investigated vascular factors with respect to longevity.

Transcriptional response to aging and caloric restriction in heart and adipose tissue

Sustained caloric restriction (CR) extends lifespan in animal models but the mechanism and primary tissue target(s) have not been identified. Gene expression changes with aging and CR were examined in both heart and white adipose tissue (WAT) of Fischer 344 (F344) male rats using Affymetrix RAE 230 arrays and validated by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) on 18 genes. As expected, age had a substantial effect on transcription on both tissues, although only 21% of cardiac age-associated genes were also altered in WAT. Gene set enrichment analysis revealed coordinated small magnitude changes in ribosomal, proteasomal, and mitochondrial genes with similarities in aging between heart and WAT. CR had very different effects on these two tissues at the transcriptional level. In heart, very few age-associated expression changes were affected by CR, while in WAT, CR suppressed a substantial subset of the age-associated changes. Genes unaltered by aging but altered by CR were identified in WAT but not heart. Most interestingly, we identified a gene expression signature associated with mammalian target of rapamycin (mTOR) activity that was down-regulated with age but preserved by CR in both WAT and heart. In addition, lipid metabolism genes, particularly those associated with peroxisome proliferator-activated receptor gamma (PPARgamma)-mediated adipogenesis were reduced with age but preserved with CR in WAT. These results highlight tissue-specific differences in the gene expression response to CR and support a role for CR-mediated preservation of mTOR activity and adipogenesis in aging WAT.

Apolipoprotein E polymorphism, age and coronary heart disease

Plasma concentrations of lipids, lipoproteins, and apolipoproteins (apo) are established risk factors for coronary heart disease (CHD). The knowledge of lipid profile may predict the potential victims of cardiovascular disease before its initiation and progression and offer the opportunity for primary prevention. The most common apo E polymorphism has been found to influence blood lipid concentrations and its correlation with CHD has been extensively investigated in the last decade. At younger ages, death from CHD is influenced by genetic factors, while the genetic effect decreases at older ages where environmental factors may play a more prominent role. If apo E polymorphism is an important genetic factor in the pathogenesis of atherosclerosis, it could affect the age of CHD onset. This review analyses the influence of apo E polymorphism on blood lipids and CHD in respect to age.

Secretion of apolipoprotein E from macrophages occurs via a protein kinase A and calcium-dependent pathway along the microtubule network

Macrophage-specific expression of apolipoprotein (apo)E protects against atherosclerosis; however, the signaling and trafficking pathways regulating secretion of apoE are unknown. We investigated the roles of the actin skeleton, microtubules, protein kinase A (PKA) and calcium (Ca2+) in regulating apoE secretion from macrophages. Disrupting microtubules with vinblastine or colchicine inhibited basal secretion of apoE substantially, whereas disruption of the actin skeleton had no effect. Structurally distinct inhibitors of PKA (H89, KT5720, inhibitory peptide PKI(14-22)) all decreased basal secretion of apoE by between 50% to 80% (P<0.01). Pulse-chase experiments demonstrated that inhibition of PKA reduced the rate of apoE secretion without affecting its degradation. Confocal microscopy and live cell imaging of apoE-green fluorescent protein-transfected RAW macrophages identified apoE-green fluorescent protein in vesicles colocalized with the microtubular network, and inhibition of PKA markedly inhibited vesicular movement. Chelation of intracellular calcium ([Ca2+]i) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate-acetoxymethyl ester (BAPTA-AM) inhibited apoE secretion by 77.2% (P<0.01). Injection of c57Bl6 apoE+/+ bone marrow-derived macrophages into the peritoneum of apoE-/- C57Bl6 mice resulted in time-dependent secretion of apoE into plasma, which was significantly inhibited by transient exposure of macrophages to BAPTA-AM and colchicine and less effectively inhibited by H89. We conclude that macrophage secretion of apoE occurs via a PKA- and calcium-dependent pathway along the microtubule network.

Plasma levels of apolipoprotein E and risk of stroke in old age

Recently, high plasma apoE levels have been shown to be related to increased cardiovascular mortality, independent of APOE genotype. Here we studied the association of plasma apoE levels with risk of stroke. Within the Leiden 85-plus Study, a prospective population-based study of 561 subjects aged 85 years, we measured plasma apoE level and determined APOE genotype at base line. The presence of stroke in the medical history and the incidence of stroke during a 5-year follow-up period were assessed by interviewing treating physicians. At base line, an increase of one standard deviation (SD) of plasma apoE level associated with a 1.47-fold higher risk of a history of stroke (P = 0.025). During follow-up, an increase of one SD of plasma apoE level associated with an increased risk of stroke (risk of stroke: 1.58, P = 0.010). This association was also observed in epsilon3epsilon3- (1.95, P = 0.002) and epsilon3epsilon4 carriers (3.01, P = 0.008), but not in epsilon2epsilon3 carriers (0.62, P = 0.440). In conclusion, in old age, except for epsilon2-allele carriers, high plasma apoE levels are associated with a higher risk of stroke, independent of APOE genotype, plasma levels of lipids, and other cardiovascular risk factors.

Plasma levels of apolipoprotein E and cognitive function in old age

The relationship between structural variants of the apolipoprotein E gene, APOE epsilon2/epsilon3/epsilon4, and dementia is well established, whereas the relationship of plasma apoE levels with dementia is less clear. Plasma apoE levels are under tight genetic control but vary widely within the various genotypes indicating that the APOE epsilon2/epsilon3/epsilon4 locus explains only a small fraction of this variation. Here we studied the association of plasma apolipoprotein E (apoE) levels with cognitive function in the elderly population at large. Within the Leiden 85-plus Study, a prospective population-based study of subjects aged 85 years, we measured plasma apoE level and genotype at base line. During a 5-year follow-up period, cognitive function was annually assessed using the Mini Mental State Examination (MMSE) and a standardized neuropsychological test battery. Among epsilon3epsilon3 carriers (n = 324), high plasma apoE levels associated with impaired global cognitive function (-1.10 points change in MMSE score per one standard deviation increase of plasma apoE level, P = 0.001), as well as lower attention (P = 0.064), speed and memory function (all P < 0.05). Adjustment for cardiovascular risk factors and exclusion of all subjects who suffered a stroke did not materially change the associations. Similar estimates were obtained in epsilon3epsilon4 carriers (n = 100), but not in epsilon2epsilon3 carriers (n = 90). We conclude that in old age, in non-epsilon2-allele carriers, high plasma apoE levels are associated with cognitive impairments, independent of genotype, cardiovascular risk factors, and stroke.

Liver X Receptor Alpha Associates With Human Life Span

In the nematode Caenorhabditis elegans, nuclear hormone receptor DAF-12 regulates the decision to go into a resistant dauer diapause, in which the worm exhibits a decreased rate of aging. Using sequence similarity searches, we previously identified the liver X receptor alpha (LXRalpha) as one of the human nuclear hormone receptors the protein sequence of which is most similar to C. elegans DAF-12. Here, we studied whether variation in the gene encoding LXRalpha associates with human life span. In the Leiden 85-Plus Study, a population-based prospective follow-up study, we genotyped four polymorphisms spanning the gene coding for LXRalpha (NR1H3) and tagged four common haplotypes. Among 563 participants, haplotype 2 associated with reduced mortality during the 7-year follow-up (hazard ratio 0.78; p =.015), predominantly caused by reduced mortality from infectious disease (hazard ratio 0.31; p =.023). Haplotype 2 also associated with higher levels of plasma apolipoprotein E, a target gene of the LXRalpha (p =.018), and higher levels of triglycerides (p =.041). Genetic variation in the gene coding for the LXRalpha (NR1H3) associates with human life span.

Apolipoprotein E and coronary disease: a puzzling paradox

Reilly and Rader discuss a new study in PLoS Medicine that shows an association between apoE levels and cardiovascular disease mortality.