The effect of the APOE polymorphism on HDL-C concentrations depends on the cholesterol ester transfer protein gene variation in a Southern European population

Penalized mediation models for multivariate data

Statistical methods to integrate multiple layers of data, from exposures to intermediate traits to outcome variables, are needed to guide interpretation of complex data sets for which variables are likely contributing in a causal pathway from exposure to outcome. Statistical mediation analysis based on structural equation models provide a general modeling framework, yet they can be difficult to apply to high-dimensional data and they are not automated to select the best fitting model. To overcome these limitations, we developed novel algorithms and software to simultaneously evaluate multiple exposure variables, multiple intermediate traits, and multiple outcome variables. Our penalized mediation models are computationally efficient and simulations demonstrate that they produce reliable results for large data sets. Application of our methods to a study of vascular disease demonstrates their utility to identify novel direct effects of single-nucleotide polymorphisms (SNPs) on coronary heart disease and peripheral artery disease, while disentangling the effects of SNPs on the intermediate risk factors including lipids, cigarette smoking, systolic blood pressure, and type 2 diabetes.

Causal association of circulating cholesterol levels with dementia: a mendelian randomization meta-analysis

Prospective studies have shown that abnormally circulating cholesterol is associated with the risk of dementia. However, whether the association is causal or not remains unclear. We attempt to infer the causal association in a MR meta-analysis by using ApoE gene polymorphisms as instrument variables. Studies with dementia risk (27 studies) or circulating lipid levels (7 studies) were included, with totally 3136 dementia patients and 3103 healthy controls. The analyses showed that carriers of ε2 allele significantly were of decreased risk of AD (OR = 0.70; 95% CI: 0.58-0.84; P < 0.01), whereas carriers of ε4 allele were of increased risk of AD (OR = 3.62; 95% CI: 3.03-4.32; P < 0.05), compared to these of ε3 allele. Circulating TC was significantly reduced in carriers of ε2 allele (WMD = - 0.29 mmol/L; 95% CI: -0.54 to -0.03; P < 0.05) and increased in carriers of ε4 allele (WMD = 0.42 mmol/l; 95% CI: 0.001-0.84; P < 0.05). In addition, carriers of ε4 allele had reduction in circulating HDL-C (WMD = - 0.04 mmol/L; 95% CI: - 0.07 to -0.001; P < 0.05). In comparing allele ε2 with ε3, the predicted OR of having AD for 1 mg/dL increment in circulating TC was 0.97 (95% CI: 0.86-0.98; P < 0.05). Comparing allele ε4 with ε3, the predicted OR for a 1 mg/dL increment in TC was 1.08 (95% CI: 1.05-17.58; P < 0.05), and reduction in HDL-C was 2.30 (95% CI: 1.51-43.99; P < 0.05). Our findings demonstrate that high circulating TC and reduced HDL-C levels might be potential risk factors of the development of AD.

Association between ApoE polymorphism and hypertension: A meta-analysis of 28 studies including 5898 cases and 7518 controls

Hypertension is one of the most common chronic diseases, constituting an independent risk factor for many diseases. Our study aimed to evaluate the association between apolipoprotein E (ApoE) genetic polymorphism and hypertension, and to provide evidence for the etiology of hypertension. Case-control studies of ApoE polymorphism and hypertension, which were included in PubMed, Embase, Web of Science, Medline, WanFang, Vip, and CNKI information databases, were selected and evaluated according to criteria of inclusion and exclusion. Eligible data were extracted and pooled, and were analyzed and assessed using Stata 12.0. Random-effect models were used when heterogeneity existed in between-study, and fixed-effect models were applied otherwise. A total of 28 studies that consisted of 5898 cases with hypertension and 7518 controls were selected. Alleles and genotypes of ApoE between cases and controls were compared. For ApoE alleles, we observed the contrast of ApoE ε2 versus ε3 allele yielded a pooled OR of 0.99 (95% CI: 0.87-1.11; P = 0.823), whereas the contrast of ε4 versus ε3 allele yielded a pooled OR of 1.95 (95% CI: 1.50-2.54; P < 0.001). For ApoE genotypes, compared with ε3/ε3 genotype, genotypes (ε2/ε2 and ε2/ε3) showed a possible association with hypertension (OR = 0.88; 95% CI: 0.79-0.99; P = 0.033), and genotypes (ε3/ε4 and ε4/ε4) had a 2.08-fold risk of developing hypertension (OR = 2.08; 95% CI: 1.58-2.74; P < 0.001). There is the association between ApoE polymorphism and hypertension: the genotypes carrying ε2 allele may be a protective factor, and the ApoE ε4 allele and the genotypes carrying ε4 allele may be risk factors for hypertension.

The ACTN3 R577X polymorphism affects the lipid profile and the prognosis of nutritional intervention in HIV-positive patients

The hypothesis of the present study is that the polymorphisms in the APOC3, CEPT, ACE, and ACTN3 genes can affect the outcome of nutritional intervention and the plasma lipid profile of HIV+ patients. To test the hypothesis, genetic material was collected from buccal cells, and serum was collected for biochemical analysis. Sixty-five patients were analyzed. The incorporation of protease inhibitor (PI) was more frequent in women (77% vs 33% in men). Nutritional intervention improved anthropometric parameters independent of the genotype. Patients with the RR genotype for the ACTN3 R577X polymorphism had lower glycemia (RR = 95.4 ± 6.5 mg/dL, RX = 102.6 ± 10.6 mg/dL, XX = 110.1 ± 16.3 mg/dL; P = .03) and a greater reduction in low-density lipoproteins (LDL) after intervention (LDL: RR = -23.7 ± 15.8 mg/dL, RX = 1.32 ± 5.13 mg/dL, XX = 30.21 ± 24.4 mg/dL; P = .01). Patients using PI had a negative response to dietary intervention regarding the levels of high-density lipoprotein (-2.4 ± 1.70 with PI, 2.56 ± 1.60 mg/dL without PI; P = .02), very low density lipoprotein (0.84 ± 2.73 with IP, -5.46 ± 3.37 mg/dL without PI; P = .03), and triglycerides (1.79 ± 13.22 with PI, -34.00 ± 17.67 mg/dL without PI; P = .052). This response was also independent of the genotype (P > 0.05) and suggested the need for oral lipid-lowering drugs in all HIV+ patients using PI. Our results indicate that the ACTN3 R577X polymorphism is a good predictor of both the lipid profile and the prognosis of nutritional intervention in reducing LDL in HIV+ patients.

Apolipoprotein E epsilon 2 allele and low serum cholesterol as risk factors for gastric cancer in a Chinese Han population

Apolipoprotein E (apoE) mediates lipid metabolism both in peripheral and in the brain. The human APOE gene has three polymorphic alleles that influence the risk for various types of cancer and neurodegenerative diseases. A potential association between APOE allele and the risk for gastric cancer has been implicated, but the specific allele involved and potential associations with the subtype and the grade of cancer malignancy need further clarification. We screened the APOE genotype in 550 gastric cancer patients and 550 non-cancer control individuals and found that the presence of the APOE ε2 and lower serum total cholesterol are associated with an increased risk for gastric cancer (all P ≤ 0.0005). Interestingly, APOE ε2 is also correlated with increased risk for both intestinal and diffuse histotypes but not with TN classification or stage in gastric cancer patients, suggesting that APOE polymorphic alleles are associated with the risk of development but unlikely the progression of gastric cancer. Since ε2 carriers have lower levels of serum total cholesterol than non-ε2 carriers, our findings suggest that the increased risk for gastric cancer by APOE ε2 allele might be mediated through lowered serum total cholesterol levels.

CardioGxE, a catalog of gene-environment interactions for cardiometabolic traits

Background

Genetic understanding of complex traits has developed immensely over the past decade but remains hampered by incomplete descriptions of contribution to phenotypic variance. Gene-environment (GxE) interactions are one of these contributors and in the guise of diet and physical activity are important modulators of cardiometabolic phenotypes and ensuing diseases.

Results

We mined the scientific literature to collect GxE interactions from 386 publications for blood lipids, glycemic traits, obesity anthropometrics, vascular measures, inflammation and metabolic syndrome, and introduce CardioGxE, a gene-environment interaction resource. We then analyzed the genes and SNPs supporting cardiometabolic GxEs in order to demonstrate utility of GxE SNPs and to discern characteristics of these important genetic variants. We were able to draw many observations from our extensive analysis of GxEs. 1) The CardioGxE SNPs showed little overlap with variants identified by main effect GWAS, indicating the importance of environmental interactions with genetic factors on cardiometabolic traits. 2) These GxE SNPs were enriched in adaptation to climatic and geographical features, with implications on energy homeostasis and response to physical activity. 3) Comparison to gene networks responding to plasma cholesterol-lowering or regression of atherosclerotic plaques showed that GxE genes have a greater role in those responses, particularly through high-energy diets and fat intake, than do GWAS-identified genes for the same traits. Other aspects of the CardioGxE dataset were explored.

Conclusions

Overall, we demonstrate that SNPs supporting cardiometabolic GxE interactions often exhibit transcriptional effects or are under positive selection. Still, not all such SNPs can be assigned potential functional or regulatory roles often because data are lacking in specific cell types or from treatments that approximate the environmental factor of the GxE. With research on metabolic related complex disease risk embarking on genome-wide GxE interaction tests, CardioGxE will be a useful resource.

The associations between high-density lipoprotein mean particle size and its fatty acid composition

AIM

High-density lipoprotein (HDL) particles are heterogeneous in their composition, structure and size and may differ in conferring protection against coronary artery disease. The aim of this study is to investigate the associations between HDL size and its fatty acid composition.

PATIENTS & METHODS

HDL mean particle size from 140 healthy men was detected by dynamic light scattering methodology and fatty acid composition of HDL was determined by gas chromatography.

RESULTS

HDL with smaller size had a higher proportion of saturated fatty acids and lower proportion of unsaturated fatty acids. HDL mean size indicated a negative correlation with palmitic acid (r = -0.17; p < 0.05) and a positive correlation with palmitoleic acid (r = 0.17; p < 0.05), oleic acid (r = 0.23; p < 0.01), arachidonic acid (r = 0.17; p < 0.05) and dihomogamalinoleic acid (r = -0.18; p < 0.05).

CONCLUSION

Saturated fatty acids of HDL are inversely assocaited and unsaturated fatty acids are directly associated with HDL mean size.

Distribution and effect of apo E genotype on plasma lipid and apolipoprotein profiles in overweight/obese and nonobese Chinese subjects

BACKGROUND

Apolipoprotein E (apo E) polymorphism has been reported to influence some lipid profile abnormalities in some ethnic groups. This study was conducted mainly to examine the possible association of apo E polymorphism with overweight/obesity in a South West Chinese population.

METHODS

Four hundred and fifty-four Han Chinese (282 overweight/obese and 172 normal weight control subjects) in Chengdu area were studied using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

The genotype and allele frequencies of apo E polymorphism in cases of overweight/obesity showed no significant statistical difference compared to those of controls. In the control group, both apo E4 and E3 allele carriers had the higher serum LDL-C and lower triglycerides (TGs) and apo E concentrations than those with apo E2 carriers, while apo E2 allele carriers had higher serum apo C-II levels than apo E3 carriers (P < 0.05). In overweight/obese group, genotype-related low density Lipoprotein-Cholesterol (LDL-C) variations were also evident, with the changes being in a same direction as the effect in the controls, and apo B100 levels were decreased and apo E increased in apo E2 allele carriers when compared with respective apo E4 and apo E4/apo E3 allele carriers (all P < 0.05).

CONCLUSION

Polymorphism of the apo E gene is associated with altered plasma LDL-C and TG, as well as apo B, apo C-II, and apo E concentrations. The effects on TG, apo B, and apo C-II levels are BMI dependent in Chinese population of Chengdu area.

CETP polymorphisms associate with brain structure, atrophy rate, and Alzheimer's disease risk in an APOE-dependent manner

Two alleles in cholesteryl ester transfer protein (CETP) gene polymorphisms have been disputably linked to enhanced cognition and decreased risk of Alzheimer's disease (AD): the V and A alleles of I405V and C-629A. This study investigates whether these polymorphisms affect brain structure in 188 elderly controls and 318 AD or mild cognitive impairment (MCI) subjects from the Alzheimer's Disease Neuroimaging Initiative cohort. Nominally signficant associations were dependent on APOE ε4 carrier status. In APOE ε4 carriers, the V and A alleles, both of which decrease CETP and increase HDL, associated with greater baseline cortical thickness and less 12-month atrophy in the medial temporal lobe. Conversely, in APOE ε4 non-carriers, the I allele, which increases CETP and decreases HDL, associated with greater baseline thickness, less atrophy and lower risk of dementia. These results suggest CETP may contribute to the genetic variability of brain structure and dementia susceptibility in an APOE-dependent manner.

Potential peripheral biomarkers for the diagnosis of Alzheimer's disease

Advances in the discovery of a peripheral biomarker for the diagnosis of Alzheimer's would provide a way to better detect the onset of this debilitating disease in a manner that is both noninvasive and universally available. This paper examines the current approaches that are being used to discover potential biomarker candidates available in the periphery. The search for a peripheral biomarker that could be utilized diagnostically has resulted in an extensive amount of studies that employ several biological approaches, including the assessment of tissues, genomics, proteomics, epigenetics, and metabolomics. Although a definitive biomarker has yet to be confirmed, advances in the understanding of the mechanisms of the disease and major susceptibility factors have been uncovered and reveal promising possibilities for the future discovery of a useful biomarker.

Aerobic exercise improves reverse cholesterol transport in cholesteryl ester transfer protein transgenic mice

We analyzed the effect of a 6-week aerobic exercise training program on the in vivo macrophage reverse cholesterol transport (RCT) in human cholesteryl ester transfer protein (CETP) transgenic (CETP-tg) mice. Male CETP-tg mice were randomly assigned to a sedentary group or a carefully supervised exercise training group (treadmill 15 m/min, 30 min sessions, five sessions per week). The levels of plasma lipids were determined by enzymatic methods, and the lipoprotein profile was determined by fast protein liquid chromatography (FPLC). CETP activity was determined by measuring the transfer rate of ¹⁴C-cholesterol from HDL to apo-B containing lipoproteins, using plasma from CETP-tg mice as a source of CETP. The reverse cholesterol transport was determined in vivo by measuring the [³H]-cholesterol recovery in plasma and feces (24 and 48 h) and in the liver (48 h) following a peritoneal injection of [³H]-cholesterol labeled J774-macrophages into both sedentary and exercise trained mice. The protein levels of liver receptors were determined by immunoblot, and the mRNA levels for liver enzymes were measured using RT-PCR. Exercise training did not significantly affect the levels of plasma lipids or CETP activity. The HDL fraction assessed by FPLC was higher in exercise-trained compared to sedentary mice. In comparison to the sedentary group, a greater recovery of [³H]-cholesterol from the injected macrophages was found in the plasma, liver and feces of exercise-trained animals. The latter occurred even with a reduction in the liver CYP7A1 mRNA level in exercised trained animals. Exercise training increased the liver LDL receptor and ABCA-1 protein levels, although the SR-BI protein content was unchanged. The RCT benefit in CETP-tg mice elicited by exercise training helps to elucidate the role of exercise in the prevention of atherosclerosis in humans.

Genetic causes of high and low serum HDL-cholesterol

Plasma levels of HDL cholesterol (HDL-C) have a strong inherited basis with heritability estimates of 40-60%. The well-established inverse relationship between plasma HDL-C levels and the risk of coronary artery disease (CAD) has led to an extensive search for genetic factors influencing HDL-C concentrations. Over the past 30 years, candidate gene, genome-wide linkage, and most recently genome-wide association (GWA) studies have identified several genetic variations for plasma HDL-C levels. However, the functional role of several of these variants remains unknown, and they do not always correlate with CAD. In this review, we will first summarize what is known about HDL metabolism, monogenic disorders associated with both low and high HDL-C levels, and candidate gene studies. Then we will focus this review on recent genetic findings from the GWA studies and future strategies to elucidate the remaining substantial proportion of HDL-C heritability. Comprehensive investigation of the genetic factors conferring to low and high HDL-C levels using integrative approaches is important to unravel novel pathways and their relations to CAD, so that more effective means of diagnosis, treatment, and prevention will be identified.

Lack of association of the APOE epsilon 4 allele with the risk of obstructive sleep apnea: meta-analysis and meta-regression

STUDY OBJECTIVES

Reports on the association of polymorphisms in the gene encoding apolipoprotein E (APOE)--a vital macromolecule in cholesterol metabolism--with obstructive sleep apnea (OSA) have provided conflicting results. Our objective was to meta-analytically synthesize the existing evidence for the association of the APOE epsilon4 allele with the risk of OSA.

DESIGN

Random effects meta-analysis and meta-regression.

SETTING

Genetic epidemiological studies reporting the association of APOE epsilon4 allele with OSA susceptibility.

PATIENTS OR PARTICIPANTS

Synthesis of APOE epsilon4 allele data from 6,508 subjects including 1,901 cases of OSA and 4,607 controls.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Eight studies were included in the random effects meta-analysis; the summary effect size measured as odds ratio (OR) for association of the APOE epsilon4 allele with the risk of OSA was found to be 1.13 (95% confidence interval 0.86-1.47). There was a statistically significant heterogeneity (I2 = 72%, P = 0.001) across study results that was not explained by the mean age, proportion of males, or the proportion possessing the APOE epsilon4 allele or when grouped based on the geographic location of the study.

CONCLUSIONS

The hypothesis that the APOE epsilon4 allele may be causally associated with OSA cannot be supported on the basis of published literature.

The effect of a novel intergenic polymorphism (rs11774572) on HDL-cholesterol concentrations depends on TaqIB polymorphism in the cholesterol ester transfer protein gene

BACKGROUND AND AIMS

Several genes have been shown to individually affect plasma lipoprotein metabolism in humans. Studies on gene-gene interactions could offer more insight into how genes affect lipid metabolism and may be useful in predicting lipid concentrations. We tested for gene-gene interactions between TaqIB SNP in the cholesterol ester transfer protein (CETP) and three novel single nucleotide polymorphisms (SNPs), namely rs11774572, rs7819412 and rs6995374 for their effect on metabolic syndrome (MetS) components and related traits.

METHODS AND RESULTS

The aforementioned SNPs were genotyped in 1002 subjects who participated in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study. Lipids were measured by standard procedures and lipoprotein subfractions, by proton nuclear magnetic resonance spectroscopy. Polymorphism rs11774572 was significantly associated with MetS (P=0.020), mainly driven by the association of the C allele with lower HDL-C (P=0.043) and higher triglycerides (P=0.049) and insulin (P=0.040) concentrations than TT subjects. A significant interaction between SNPs rs11774572 and CETP-TaqIB SNPs was found for HDL-C concentrations (P=0.006) and for HDL (P=0.008) and LDL particle sizes (P=0.009), small LDL (P=0.004), and VLDL concentrations (P=0.021), in which TT homozygotes displayed higher HDL-C concentrations and for HDL and LDL particle sizes, and lower small LDL and VLDL concentrations than C carriers, if they were CETP B2 allele carriers (P values ranging from <0.001 to 0.001).

CONCLUSIONS

The rs11774572 polymorphism may play a role in the dyslipidemia that characterizes MetS. The interaction between rs11774572 and CETP-TaqIB SNPs on HDL-C concentrations provides some insights into the underlying mechanisms.

Plasma biomarkers for mild cognitive impairment and Alzheimer's disease

PURPOSE OF REVIEW

With the move toward development of disease modifying treatments, there is a need for more specific diagnosis of early Alzheimer's disease (AD) and mild cognitive impairment (MCI), plasma biomarkers are likely to play an important role in this. We review the current state of knowledge on plasma biomarkers for MCI and AD, including unbiased proteomics and very recent longitudinal studies.

RECENT FINDINGS

With the use of proteomics methodologies, some proteins have been identified as potential biomarkers in plasma and serum of AD patients, including alpha-1-antitrypsin, complement factor H, alpha-2-macroglobulin, apolipoprotein J, apolipoprotein A-I. The findings of cross-sectional studies of plasma amyloid beta (A beta) levels are conflicting, but some recent longitudinal studies have shown that low plasma A beta 1-42 or A beta 1-40 levels, or A beta 1-42/A beta 1-40 ratio may be markers of cognitive decline. Other potential biomarkers for MCI and AD reflecting a variety of pathophysiological processes have been assessed, including isoprostanes and homocysteine (oxidative stress), total cholesterol and ApoE4 allele (lipoprotein metabolism), and cytokines and acute phase proteins (inflammation). A panel of 18 signal proteins was reported as markers of MCI and AD.

SUMMARY

A variety of potential plasma biomarkers for AD and MCI have been identified, however the findings need replication in longitudinal studies. This area of research promises to yield interesting results in the near future.

Association between apolipoprotein E polymorphism, lipids, and coronary artery disease in Tunisian type 2 diabetes

BACKGROUND

The relationship between apolipoprotein E (ApoE) polymorphism, fasting lipid parameters, and coronary artery disease (CAD) is controversial.

METHODS

We studied this relationship, for the first time, in Tunisian type 2 diabetic patients. The studied population comprised 157 type 2 diabetic patients (145 of them were not on any lipid-lowering drugs). Fasting lipids were measured by enzymatic methods and ApoE genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

Our results showed that the alleles E2, E3, and E4 were found in 4%, 88%, and 8% of patients, respectively. In the total type 2 diabetic population, no association was found between ApoE polymorphism, lipid parameters, and CAD. However, the E4 allele was associated with elevated low-density lipoprotein cholesterol concentration and with CAD in type 2 diabetic men.

CONCLUSION

The effect of ApoE polymorphism on CAD is gender-dependent in the Tunisian type 2 diabetic population. ApoE 4 allele may enhance atherogenesis indirectly by a strong effect on low-density lipoprotein cholesterol.

Health-protective and adverse effects of the apolipoprotein E epsilon2 allele in older men

OBJECTIVES

To reexamine a health-protective role of the common apolipoprotein E (APOE) polymorphism focusing on connections between the APOE epsilon2-containing genotypes and impairments in instrumental activities of daily living (IADLs) in older (> or = 65) men and women and to examine how diagnosed coronary heart disease (CHD), Alzheimer's disease, colorectal cancer, macular degeneration, and atherosclerosis may mediate these connections.

DESIGN

Retrospective cross-sectional study.

SETTING

The unique disability-focused data from a genetic subsample of the 1999 National Long Term Care Survey linked with Medicare service use files.

PARTICIPANTS

One thousand seven hundred thirty-three genotyped individuals interviewed regarding IADL disabilities.

MEASUREMENTS

Indicators of IADL impairments, five geriatric disorders, and epsilon2-containing genotypes.

RESULTS

The epsilon2/3 genotype is a major contributor to adverse associations between the epsilon2 allele and IADL disability in men (odds ratio (OR)=3.09, 95% confidence interval (CI)=1.53-6.26), although it provides significant protective effects for CHD (OR=0.55, 95% CI=0.33-0.92), whereas CHD is adversely associated with IADL disability (OR=2.18, 95% CI=1.28-3.72). Adjustment for five diseases does not significantly alter the adverse association between epsilon2-containing genotypes and disability. Protective effects of the epsilon2/3 genotype for CHD (OR=0.52, 95% CI=0.27-0.99) and deleterious effects for IADLs (OR=3.50, 95% CI=1.71-7.14) for men hold in multivariate models with both these factors included. No significant associations between the epsilon2-containing genotypes and IADL are found in women.

CONCLUSION

The epsilon2 allele can play a dual role in men, protecting them against some health disorders, while promoting others. Strong adverse relationships with disability suggest that epsilon2-containing genotypes can be unfavorable factors for the health and well-being of aging men.

Genetic determinants of plasma lipoproteins

The search for common genetic determinants of plasma lipoproteins began in the early 1980s. Despite some exceptions, these efforts have not yet yielded a set of biological markers that can be used in clinical practice. By contrast, successes in defining the molecular basis of rare single-gene disorders, such as familial hypoalphalipoproteinemia, have shown the value of experimental designs that focus on genomic analysis of individuals within the tails of Gaussian distributions of quantitative lipoprotein traits. For example, this strategy showed that a small but relevant proportion of individuals within the <5% tail of plasma HDL-cholesterol distribution have mutations in genes that cause familial hypoalphalipoproteinemia. The value of clinical testing for genomic variants as an adjunct to a biochemical measurement of plasma lipoproteins, however, is at best questionable. A more direct impact of genetic studies is that definitions of 'common' and 'large genetic effects' have become more tempered, reflecting perhaps the biological reality that plasma lipoproteins are probably determined by the aggregate of numerous modest and occasional large genetic effects in addition to environmental factors. Here, we review recent progress on genomic variants and cholesterol metabolism, and discuss the impact these genetic studies will have on clinical cardiology.

Maternal and fetal variation in genes of cholesterol metabolism is associated with preterm delivery

OBJECTIVE

To examine the contribution of variants in fetal and maternal cholesterol metabolism genes in preterm delivery (PTD).

STUDY DESIGN

A total of 40 single-nucleotide polymorphisms (SNPs) in 16 genes related to cholesterol metabolism were examined for 414 preterm infants (gestational ages 22 to 36 weeks; comprising 305 singletons and 109 twins) and at least 1 parent. Fetal effects were assessed using the transmission disequilibrium test (TDT) for each SNP, followed by a log linear model-based approach to utilize families with missing parental genotypes for those SNPs showing significance under TDT. Genetic variant effects were examined for a role in PTD, gestational age and birth weight. Maternal effects were estimated using a log linear model-based approach.

RESULT

Among singleton gestations, suggestive association (P<0.01 without adjusting for multiple comparisons) was found between birth weight and fetal DHCR7 gene/SNP combinations (rs1630498, P=0.002 and rs2002064, P=0.003). Among all gestations, suggestive associations were found between PTD and fetal HMGCR (rs2303152, P=0.002) and APOA1 (rs 5070, P=0.004). The result for HMGCR was further supported by the log linear model-based test in the single births (P=0.007) and in all births (P=0.006). New associations (APOE and ABCA1) were observed when birth weight was normalized for gestational age suggesting independent effects of variants on birth weight separate from effects on PTD. Testing for maternally mediated genetic effects has identified suggestive association between ABCA1 (rs4149313, P=0.004) and decreased gestational age.

CONCLUSION

Variants in maternal and fetal genes for cholesterol metabolism were associated with PTD and decreased birth weight or gestational age in this study. Genetic markers may serve as one mechanism to identify high-risk mothers and fetuses for targeted nutritional treatment and/or prevention of low birth weight or PTD.

Sex-specific interaction between APOE and APOA5 variants and determination of plasma lipid levels

The APOA5 and APOE genes play an important role in determination of plasma levels of triglycerides (TG) and total cholesterol (TC). We have analyzed APOA5 (T-1131>C and Ser19>Trp) and APOE (e2/e3/e4) variants in 2500 representatively selected Caucasians (1168 men, 1332 women). In female subjects (but not in male) an association between APOE polymorphism and TC was observed on the background of the common APOA5 haplotype (TT-1131/SerSer19) - APOE2 carriers have the lowest (5.12 (1.15) mmol/l) and the APOE4 carriers have the highest (6.05 (1.06) mmol/l) levels of plasma TC (P<0.001). If at least one APOA5 C-1131 or Trp19 allele was present, APOE exhibits no significant effect on plasma TC. APOA5 did not affect plasma TG levels, if APOE4 allele was present. In the presence of APOE2 or APOE3, carriers of the APOA5 alleles, C-1131 and/or Trp19, have higher TG levels (1.64 (1.05) mmol/l) than others (1.37 (0.75) mmol/l) (P<0.01). In male subjects, the same, but non-significant trend was observed. In female subjects, we have detected an interaction between APOE and APOA5 variants and plasma lipid levels.

Genetic factors affecting HDL levels, structure, metabolism and function

PURPOSE OF REVIEW

HDL is a recognized negative risk factor for the cardiovascular diseases. Establishing the genetic determinants of HDL concentration and functions would add to the prediction of cardiovascular risk and point to the biochemical mechanisms underlying this risk. The present review focuses on various approaches to establish genetic determinants of the HDL concentration, structure and function.

RECENT FINDINGS

While many genes contribute to the HDL concentration and collectively account for half of the variability, polymorphism of individual candidate genes contributes little. There are strong interactions between environmental and genetic influences. Recent findings have confirmed that APOA1 and ABCA1 exert the strongest influence on HDL concentrations and risk of atherosclerosis. CETP and lipases also affect the HDL concentration and functionality, but their connection to the atherosclerosis risk is conditional on the interaction between environmental and genetic factors.

SUMMARY

Analysis of genetic determinants of HDL-cholesterol in patients with specific disease states or in response to the environmental condition may be a more accurate way to assess variations in HDL concentration. This may result in defining the rules of interaction between genetic and environmental factors and lead to understanding the mechanisms responsible for the variations in HDL concentration and functionality.