Extensive association analysis between the CETP gene and coronary heart disease phenotypes reveals several putative functional polymorphisms and gene-environment interaction

Functional interaction between −629C/A, −971G/A and −1337C/T polymorphisms in the CETP gene is a major determinant of promoter activity and plasma CETP concentration in the REGRESS Study

Cholesteryl ester transfer protein (CETP) plays a key role in the determination of high-density lipoprotein (HDL) levels via its action on intravascular HDL metabolism. The TaqIB polymorphism of the CETP gene is associated with plasma CETP and high-density lipoprotein cholesterol (HDL-C) levels and with premature coronary artery disease. Such associations appear to result from linkage disequilibrium between TaqIB and other functional polymorphisms. To date, only one functional promoter variant, which may explain the effects of TaqIB, has been identified at position -629 in the CETP gene. Here we describe a C/T polymorphism located at position -1337 in the human CETP gene (C allele frequency: 0.684), which is significantly associated with plasma HDL-C and CETP levels (P=0.0001 and P<0.0001, respectively). Transient transfection of a reporter gene construct containing the CETP promoter from -1707/+28 in liver cells (HepG2) revealed that the -1337T allele was expressed to a significantly lower degree (-34%, P<0.0001) than the -1337C allele. In addition, we clearly demonstrated that the -971G/A polymorphism is functional and that its functionality is intimately linked to the presence of the -1337 site. In vitro evaluation of potential interaction between -1337C/T and other functional variants of the CETP gene (-971G/A and -629C/A) demonstrated that these three functional CETP promoter polymorphisms can interact together to determine the overall activity of the CETP gene and thus contribute significantly to variation in plasma CETP mass concentration.

Association of CETP TaqI and APOE polymorphisms with type II diabetes mellitus in North Indians: a case control study

BACKGROUND

Genetic variants of proteins involved in lipid metabolism may play an important role in determining the susceptibility for complications associated with type II diabetes mellitus (T2DM). Goal of the present study was to determine the association of cholesteryl ester transfer protein TaqI B, D442G, and APOE Hha I polymorphisms with T2DM and its complications.

METHODS

Study subjects were 136 patients and 264 healthy controls. All polymorphisms were detected using PCR-RFLP and statistical analysis done with chi2 test and ANOVA.

RESULTS

Although CETP TaqI B polymorphism was not associated with the T2DM, yet B1B2 genotype was significantly (p = 0.028) associated with high risk of hypertension in diabetic patients (OR = 3.068, 95% CI 1.183-7.958). In North Indians D442G variation in CETP gene was found to be absent. Frequency of APOE HhaI polymorphism was also not different between patients and controls. In diabetic patients having neuropathy and retinopathy significantly different levels of total-cholesterol [(p = 0.001) and (p = 0.029) respectively] and LDL-cholesterol [(p = 0.001) and (p = 0.001) respectively] were observed when compared to patients with T2DM only. However, lipid levels did not show any correlation with the CETP TaqI B and APOE Hha I genetic polymorphisms.

CONCLUSION

CETP TaqI B and APOE HhaI polymorphism may not be associated with type II diabetes mellitus in North Indian population, however CETP TaqI B polymorphism may be associated with hypertension along with T2DM.

Application of pooled genotyping to scan candidate regions for association with HDL cholesterol levels

Association studies are used to identify genetic determinants of complex human traits of medical interest. With the large number of validated single nucleotide polymorphisms (SNPs) currently available, two limiting factors in association studies are genotyping capability and costs. Pooled DNA genotyping has been proposed as an efficient means of screening SNPs for allele frequency differences in case-control studies and for prioritising them for subsequent individual genotyping analysis. Here, we apply quantitative pooled genotyping followed by individual genotyping and replication to identify associations with human serum high-density lipoprotein (HDL) cholesterol levels. The DNA from individuals with low and high HDL cholesterol levels was pooled separately, each pool was amplified by polymerase chain reaction in triplicate and each amplified product was separately hybridised to a high-density oligonucleotide array. Allele frequency differences between case and control groups with low and high HDL cholesterol levels were estimated for 7,283 SNPs distributed across 71 candidate gene regions spanning a total of 17.1 megabases. A novel method was developed to take advantage of independently derived haplotype map information to improve the pooled estimates of allele frequency differences. A subset of SNPs with the largest estimated allele frequency differences between low and high HDL cholesterol groups was chosen for individual genotyping in the study population, as well as in a separate replication population. Four SNPs in a single haplotype block within the cholesteryl ester transfer protein (CETP) gene interval were significantly associated with HDL cholesterol levels in both populations. Our study is among the first to demonstrate the application of pooled genotyping followed by confirmation with individual genotyping to identify genetic determinants of a complex trait.

Coronary heart disease and polymorphisms in genes affecting lipid metabolism and inflammation

Several biologic systems contribute to the pathophysiology of atherosclerosis and its complications, and within each of these systems many genes have been explored to establish the possible implication of their variability in coronary heart disease (CHD) risk. This report is focused on recent results pertaining to lipid and inflammatory genes, their variability, and their relationship with intermediate phenotypes and CHD. For both systems, there is no evidence at the present time that testing genetic polymorphisms might be of any benefit to the patient, for the diagnosis or prognosis of CHD, or for tailoring drug prescription. Understanding the genetics of complex traits like CHD will require a system approach that allows a modeling of the interaction among genes as well as between genetic and nongenetic sources of variation.

Increasing High-Density Lipoprotein Cholesterol in Dyslipidemia by Cholesteryl Ester Transfer Protein Inhibition

Reduced HDL cholesterol may be a risk factor comparable in importance to increased LDL cholesterol. Interventions that raise HDL are antiatherosclerotic, presumably through acceleration of reverse cholesterol transport and by antioxidant and antiinflammatory effects. In the hypercholesterolemic rabbit, HDL levels can be increased by >50% by inhibition of cholesteryl ester transfer protein (CETP), a molecule that plays a central role in HDL metabolism. This HDL-raising effect is antiatherosclerotic in moderately severe hyperlipidemia but appears to be ineffective in the presence of severe hypertriglyceridemia. In humans, mutations resulting in CETP inhibition have been associated with both reduced and increased risk of atherosclerosis. Proposed explanations for these apparently disparate observations are that the antiatherosclerotic effect of CETP inhibition varies with either the metabolic milieu or the degree of CETP inhibition. We now have pharmacological inhibitors of CETP that are capable of increasing HDL by as much as 50% to 100% in humans. The importance of this development is that reduced HDL is a risk factor independent of LDL and that these new agents alter HDL by a magnitude comparable to that of statins on LDL. Clinical trials, now beginning, will need to identify the patient subsets in which CETP inhibition may be more or less effective.

Polymorphisms of TNFα, IL1β, and IL1RN genes in chronic obstructive pulmonary disease

It is recognized that genetic factors play a role in the susceptibility to COPD. COPD is characterized by airflow limitation. Chronic inflammation causes small airway disease and parenchymal destruction, leading to the airflow limitation. Polymorphisms in pro-inflammatory cytokine genes may confer a risk for the development of COPD. A case-control association study was performed in Japanese population (88 COPD patients and 61 controls) and Egyptian population (106 patients and 72 controls). Genotype and allele frequencies of the TNFalpha -308 G/A and +489 G/A polymorphisms, the IL1beta -511 C/T, -31 T/C, and +3954 C/T polymorphisms, and a VNTR polymorphism in intron 2 of the IL1RN gene were investigated. In addition, pairwise haplotype frequencies were analyzed. When studied independently, none of the polymorphisms were associated with the development of COPD in both populations. However, in the Egyptian population, the distributions of the haplotype (IL1beta -31 T/C : IL1beta +3954 C/T) were significantly different between the COPD patients and the controls (p(corr)=0.0037). Our findings suggest that this haplotype within the IL1beta gene may be involved in the pathogenesis of COPD and that the genetic factors of COPD susceptibility might be different between different populations.

Exploration of multilocus effects in a highly polymorphic gene, the apolipoprotein (APOB) gene, in relation to plasma apoB levels

A detailed exploration of all the polymorphisms in candidate genes is required to better characterize the relationship between gene variability and complex traits. We propose a novel strategy for investigating the association between a highly polymorphic gene and a phenotype, by combining a multilocus genotype analysis and an haplotype analysis. For the multilocus genotype analysis, a data mining tool--termed DICE (Detection of Informative Combined Effects)--was developed to identify the best subset of polymorphisms that are associated--individually or in combination--with the phenotype. For the haplotype analysis, we used our recently developed method of haplotype-phenotype association to determine the most informative and parsimonious haplotype model fitting the data. We illustrate this strategy by investigating the association between twelve polymorphisms of the APOB gene and plasma apoB levels in 1442 European subjects. After exploring all main effects and interactions between polymorphisms, DICE identified the N4311S polymorphism as the most informative polymorphism in relation to apoB levels. Haplotype analysis led to the same conclusion. Additionally, DICE identified the E4154K (EcoRI) and the T2488T (XbaI) polymorphisms as potentially interesting. This selection was not modified by inclusion of the common APOE polymorphism in the analysis.

Inhibition of cholesteryl ester transfer protein activity: a new therapeutic approach to raising high-density lipoprotein

High-density lipoprotein (HDL) cholesterol levels are inversely associated with risk of atherosclerotic cardiovascular disease (ASCVD), leading to the concept that pharmacologic therapy to raise HDL cholesterol levels may reduce ASCVD risk. There is substantial interest in the concept of inhibition of the cholesteryl ester transfer protein (CETP) as a novel strategy for raising HDL cholesterol levels, as well as reducing levels of atherogenic lipoproteins. This article reviews the physiology of CETP in lipoprotein metabolism and the data in animals and humans that are relevant to the question of whether CETP inhibition may some day be part of the clinical armamentarium for treating dyslipidemia and atherosclerotic vascular disease.

CETP polymorphisms associated with HDL cholesterol may differ from those associated with cardiovascular disease

To better understand the role of cholesteryl ester transfer protein (CETP) in cardiovascular disease, nine polymorphisms spanning the gene from the upstream promoter region to beyond the 3'UTR were genotyped in 2553 individuals from multiple ethnic groups and with different cardiovascular disease profiles. The frequency of four of these SNPs varied by 40-300% between Caucasians and African Americans. SNPs in each ethnic group fell into two haploblocks with significant linkage disequilibrium within each block. SNPs in the 5' haploblock were significantly associated with HDL cholesterol while SNPs in the 3' haploblock were, at best, only weakly associated with HDL-C. One SNP in the 3' haploblock (rs1800774 in intron 12) was highly associated with history of myocardial infarction even though it was not associated with HDL-C. This association was driven by the effect in Caucasian women where 11.9% of the women with no history of MI are homozygous for the less common allele while 23.7% of those with a history of MI share this genotype. In addition, this SNP was highly associated with BMI among Caucasians (p < 0.0001). The association of HDL-C with CETP genotype was found to be independent of smoking or alcohol consumption. These results replicate some earlier findings and also help to explain some of the apparent contradictions in the literature surrounding the role of CETP in modulating HDL-C and cardiovascular disease.

Cholesteryl ester transfer protein TaqIB variant, high-density lipoprotein cholesterol levels, cardiovascular risk, and efficacy of pravastatin treatment: individual patient meta-analysis of 13,677 subjects

BACKGROUND

Several studies have reported that the cholesteryl ester transfer protein (CETP) TaqIB gene polymorphism is associated with HDL cholesterol (HDL-C) levels and the risk of coronary artery disease (CAD), but the results are inconsistent. In addition, an interaction has been implicated between this genetic variant and pravastatin treatment, but this has not been confirmed.

METHODS AND RESULTS

A meta-analysis was performed on individual patient data from 7 large, population-based studies (each >500 individuals) and 3 randomized, placebo-controlled, pravastatin trials. Linear and logistic regression models were used to assess the relation between TaqIB genotype and HDL-C levels and CAD risk. After adjustment for study, age, sex, smoking, body mass index (BMI), diabetes, LDL-C, use of alcohol, and prevalence of CAD, TaqIB genotype exhibited a highly significant association with HDL-C levels, such that B2B2 individuals had 0.11 mmol/L (0.10 to 0.12, P<0.0001) higher HDL-C levels than did B1B1 individuals. Second, after adjustment for study, sex, age, smoking, BMI, diabetes, systolic blood pressure, LDL-C, and use of alcohol, TaqIB genotype was significantly associated with the risk of CAD (odds ratio=0.78 [0.66 to 0.93]) in B2B2 individuals compared with B1B1 individuals (P for linearity=0.008). Additional adjustment for HDL-C levels rendered a loss of statistical significance (P=0.4). Last, no pharmacogenetic interaction between TaqIB genotype and pravastatin treatment could be demonstrated.

CONCLUSIONS

The CETP TaqIB variant is firmly associated with HDL-C plasma levels and as a result, with the risk of CAD. Importantly, this CETP variant does not influence the response to pravastatin therapy.

Polymorphisms in Four Genes Related to Triglyceride and HDL-cholesterol Levels in the General Japanese Population in 2000

We studied the association of six common polymorphisms of four genes related to lipid metabolism with serum lipid levels. We selected single-nucleotide polymorphisms (SNPs) in the genes for cholesteryl ester transfer protein (CETP), lipoprotein lipase (LPL), hepatic lipase (LIPC), and apolipoprotein CIII (APOC3), and studied 2267 individuals randomly selected from the participants of Serum Lipid Survey 2000. There was a significant association of CETP polymorphism (D442G, Int14 +1 G --> A, and TaqIB), LPL polymorphism (S447X), and LIPC polymorphism (-514 --> CT) with HDL-cholesterol levels. We also found a significant association of LPL polymorphism (S447X) and APOC3 polymorphism (SstI) with triglyceride levels. This is the largest database showing the association of common genetic variants in lipid metabolism with serum lipid levels in the general Japanese population. Further study is necessary to elucidate the role of these gene polymorphisms in cardiovascular events.

Variations in high-density lipoprotein cholesterol in relation to physical activity and Taq 1B polymorphism of the cholesteryl ester transfer protein gene

The aim of the study was to determine any association of physical activity and Taq 1B polymorphism in the cholesteryl ester transfer protein gene on high-density lipoprotein (HDL) cholesterol. Five hundred and four subjects, 390 males and 114 females consisting of an equal number of age- and sex-matched healthy controls and patients with coronary artery disease, were included. The mean age (+/-SD) of the patients and controls were 57.5 +/- 10.6 years and 56.8 +/- 11.0 years, respectively. All the patients underwent coronary angiography; 33, 58, 63, and 98 patients had normal coronaries, single-, two-, or triple-vessel disease, respectively. A third of the patients had suffered from a myocardial infarction. The genotype distribution conforming to Hardy-Weinberg equilibrium was similar for cases and controls. The mean HDL cholesterol increased from B1B1 through B2B2 genotype in controls and sedentary male patients. Self-reported leisure time physical activity, consisting mostly of an hour of morning walk daily, was associated with a rise in mean HDL cholesterol in male controls (33.6 +/- 7.9 mg/dl to 36.2 +/- 8.9 mg/dl, p = 0.037) and patients (32.4 +/- 7.9 mg/dl to 35.7 +/- 11.0 mg/dl; p = 0.018). The exercise-associated rise in HDL cholesterol was most pronounced in controls (32.1 +/- 9.1 mg/dl to 36.8 +/- 9.3 mg/dl, p = 0.05) and male patients (30.5 +/- 7.4 mg/dl to 37.2 +/- 9.7 mg/dl, p = 0.007) with B1B1 rather than B1B2 or B2B2 genotype. The results suggest a possible gene-environment interaction in the regulation of HDL cholesterol that needs to be confirmed in other populations and larger samples to rule out a chance occurrence.

Molecular mechanisms of cholesteryl ester transfer protein deficiency in Japanese

Plasma cholesteryl ester transfer protein (CETP) facilitates the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to apolipoprotein B-containing lipoproteins. Since CETP regulates the plasma levels of HDL cholesterol and the size of HDL particles, CETP is considered to be a key protein in reverse cholesterol transport (RCT), a protective system against atherosclerosis. The importance of plasma CETP in lipoprotein metabolism was demonstrated by the discovery of CETP-deficient subjects with marked hyperalphalipoproteinemia (HALP). Genetic CETP deficiency is the most important and common cause of HALP in the Japanese. Ten mutations of the CETP gene have been demonstrated as causes of HALP, including two common mutations: an intron 14 splicing defect (Int14 + 1 G --> A) and an exon 15 missense mutation (D442G). The subjects with CETP deficiency show a variety of abnormalities in the concentration, composition, and function of both HDL and low density lipoprotein (LDL). CETP deficiency is considered a physiological state of impaired RCT, which may possibly lead to the development of atherosclerosis despite high HDL cholesterol levels. However, the pathophysiological significance of CETP in terms of atherosclerosis has been controversial. Epidemiological studies in Japanese-Americans living in Hawaii and Japanese in the Omagari area, where HALP subjects with an intron 14 splicing defect of the CETP gene are markedly frequent, have shown a relatively increased incidence of coronary atherosclerosis in CETP deficiency. On the other hand, the TaqIB polymorphism-B2 allele with low CETP mass and increased HDL cholesterol has been related to a decreased risk for coronary heart disease (CHD) in many studies, including the Framingham Offspring Study. The current review focused on the characterization of the Japanese subjects with CETP deficiency, including our recent findings.

A review of CETP and its relation to atherosclerosis

Although the atheroprotective role of HDL cholesterol (HDL-c) is well documented, effective therapeutics to selectively increase plasma HDL-c levels are not yet available. Recent progress in unraveling human HDL metabolism has fuelled the development of strategies to decrease the incidence and progression of coronary artery disease (CAD) by raising HDL-c. In this quest for novel drugs, cholesteryl ester transfer protein (CETP) represents a pivotal target. The role of this plasma protein in HDL metabolism is highlighted by the discovery that genetic CETP deficiency is the main cause of high HDL-c levels in Asian populations. The use of CETP inhibitors to effectively increase HDL-c concentration in humans was recently published and data with regard to the effect on human atherosclerosis are expected shortly. This review discusses the potential of CETP inhibitors to protect against atherosclerosis in the context of the current knowledge of CETP function in both rodents and humans.

CETP gene variation: relation to lipid parameters and cardiovascular risk

PURPOSE OF REVIEW

Over the past decade lowering of low-density lipoprotein-cholesterol levels has been established as the foundation for preventing coronary artery disease, but substantial additional risk reduction remains to be gained by modifying risk factors other than low-density lipoprotein-cholesterol. Raising high-density lipoprotein-cholesterol levels by inhibiting activity of the cholesteryl ester transfer protein (CETP) is a prime target. Research on naturally occurring variants in the CETP gene has yielded numerous insights that have been relevant for understanding lipoprotein metabolism, and crucial to the development of pharmacological CETP inhibition.

RECENT FINDINGS

This review discusses a number of recently published studies, including a haplotype analysis of the CETP promoter region confirming that the -629 C-->A variant, not the TaqIB variant, is instrumental in determining CETP activity, as previously suggested. In addition, we discuss a recent meta-analysis which confirms that the I405V and TaqIB variants are indeed associated with lower CETP activity and higher high-density lipoprotein-cholesterol levels. Also, we review two subanalyses of large randomized controlled pravastatin trials which found no evidence for a proposed pharmacogenetic interaction between the CETP TaqIB variant and pravastatin treatment.

SUMMARY

The currently available evidence suggests that several genetic variants in the CETP gene are associated with altered CETP plasma levels and activity, high-density lipoprotein-cholesterol plasma levels, low-density lipoprotein and high-density lipoprotein particle size, and perhaps the risk of coronary artery disease. No evidence exists for a pharmacogenetic interaction between the CETP TaqIB variant and pravastatin efficacy.

Variation in the lamin A/C gene: associations with metabolic syndrome

OBJECTIVE

Metabolic syndrome is associated with increased risk for cardiovascular disease and type 2 diabetes mellitus (T2DM). The lamin A/C (LMNA) gene, mutations of which cause rare syndromes of severe insulin resistance and dyslipidemia, is located on chromosome 1q21-q24, a region linked to T2DM in several genome wide scans, including in the Old Order Amish. To determine whether polymorphisms in LMNA influence susceptibility to metabolic syndrome and its constituent components.

METHODS AND RESULTS

We performed DNA sequence analysis of LMNA. Six single-nucleotide polymorphisms (SNPs) were identified: c.141889C>T (intron 3), c.141906G>T (intron 3), A287A (c.141253T>C; exon 5), c.140353G>A (intron 6), c.139418C>T (intron 8), and H566H (c. 138747C>T; exon 10). In 971 participants from the Amish Family Diabetes Study, the H566H polymorphism of LMNA was associated with metabolic syndrome diagnosed according to National Cholesterol Education Program ATP III criteria and also higher mean fasting triglyceride and lower mean high-density lipoprotein-cholesterol concentrations. However, no differences in allele frequencies were observed for any SNP among participants with T2DM or impaired glucose homeostasis (IGH) and normoglycemic controls. Haplotype analysis showed that >87% of individuals carried 1 of 2 common LMNA haplotypes. There were no significant differences in haplotype frequencies among subjects with metabolic syndrome T2DM, IGH, and controls.

CONCLUSIONS

Sequence variation in LMNA may confer modest susceptibility for development of metabolic syndrome and dyslipidemia in the Amish. To determine whether polymorphisms in LMNA influence susceptibility to metabolic syndrome and its constituent components, we performed DNA analysis of polymorphisms in LMNA. The H566H polymorphism was associated with metabolic syndrome and also higher mean fasting triglyceride and lower mean HDL-cholesterol concentrations in the Old Order Amish.

In-Depth Haplotype Analysis of ABCA1 Gene Polymorphisms in Relation to Plasma ApoA1 Levels and Myocardial Infarction

OBJECTIVE

By regulating the cellular cholesterol efflux from peripheral cells to high-density lipoprotein, the ABCA1 protein is suspected to play a key role in lipid homeostasis and atherosclerosis. Twenty-six polymorphisms of the ABCA1 gene were genotyped and tested for association with plasma levels of ApoA1 and myocardial infarction (MI) in the ECTIM study.

METHODS AND RESULTS

In addition to single-locus analysis, a systematic exploration of all possible haplotype effects was performed, with this exploration being performed on a minimal set of "tag" polymorphisms that define the haplotype structure of the gene. Two polymorphisms were associated with plasma levels of ApoA1, 1 in the promoter (C-564T) and 1 in the coding (R1587K) regions, whereas only 1 polymorphism (R219K) was associated with the risk of MI. However, no haplotype effect was detected on ApoA1 variability or on the risk of MI.

CONCLUSIONS

ABCA1 gene polymorphisms but not haplotypes are involved in the variability of plasma ApoA1 and the susceptibility to coronary artery disease.

Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia

In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.

Alcohol Consumption and Carotid Atherosclerosis in Older Adults

OBJECTIVE

The association of alcohol use with atherosclerosis is inconsistent in previous studies.

METHODS AND RESULTS

For the Cardiovascular Health Study, 5888 adults aged 65 years and older underwent a standardized interview and examination. They reported beer, wine, and liquor use individually and underwent B-mode ultrasonography to determine internal and common carotid intima-media thickness (IMT). We compared composite carotid IMT values cross-sectionally using linear regression to adjust for demographic and clinical characteristics. Among 4247 participants free of cardiovascular disease, consumers of 1 to 6 drinks per week had 0.07+/-0.04-mm lower composite IMT and consumers of 14 or more drinks per week had 0.07+/-0.05-mm higher IMT than abstainers (P quadratic trend=0.02). We found similar relationships using internal and common carotid thickness measures and among men and women. The higher IMT associated with heavier alcohol use was particularly strong among 1592 participants with confirmed cardiovascular disease (0.24+/-0.09 mm greater than abstainers). Controlling for HDL cholesterol levels reduced the effect on composite IMT among consumers of 1 to 6 drinks per week by 22%.

CONCLUSIONS

Relative to older adults who abstain from alcohol, consumption of 1 to 6 drinks per week had an inverse association with carotid atherosclerosis whereas consumption of 14 or more drinks had a positive association.

Automated detection of informative combined effects in genetic association studies of complex traits

There is a growing body of evidence suggesting that the relationships between gene variability and common disease are more complex than initially thought and require the exploration of the whole polymorphism of candidate genes as well as several genes belonging to biological pathways. When the number of polymorphisms is relatively large and the structure of the relationships among them complex, the use of data mining tools to extract the relevant information is a necessity. Here, we propose an automated method for the detection of informative combined effects (DICE) among several polymorphisms (and nongenetic covariates) within the framework of association studies. The algorithm combines the advantages of the regressive approaches with those of data exploration tools. Importantly, DICE considers the problem of interaction between polymorphisms as an effect of interest and not as a nuisance effect. We illustrate the method with three applications on the relationship between (1). the P-selectin gene and myocardial infarction, (2). the cholesteryl ester transfer protein gene and plasma high-density-lipoprotein cholesterol concentration, and (3). genes of the renin-angiotensin-aldosterone system and myocardial infarction. The applications demonstrated that the method was able to recover results already found using other approaches, but in addition detected biologically sensible effects not previously described.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

No physical activity x CETP 1b.-629 interaction effects on lipid profile

INTRODUCTION/PURPOSE

Being physically active may improve the lipid profile by increasing high-density lipoprotein (HDL) cholesterol (HDL-C) concentrations. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from HDL to lipoproteins of lower density. The potential interactive effects of physical activity and the CETP A-C polymorphism on exon 1b.-629 (CETP 1b.-629) with lipid profile were investigated in a population-based cross-sectional survey.

METHODS

1720 men and women, ages 35-74 yr, were randomly selected from the general adult population of Geneva, Switzerland, throughout 1999-2000. A validated physical activity questionnaire measured total energy expenditure and the percentage thereof used in high-intensity activities (% high-intensity activity, e.g., brisk walking, sports). CETP 1b.-629 was assayed with PCR and allele-specific oligonucleotide hybridization. The study had 80% power to detect lipid profile differences from 0.10 to 0.15 mmol x L-1 ( approximately 4-6 mg x dL-1) between gender-specific (CETP genotype x % high-intensity activity) subgroups.

RESULTS

HDL-C (mmol x L-1) was higher in men and women with the AA genotype (respectively, 1.26 and 1.56) versus those with CC (1.14 and 1.46) (P < 0.0001, P < 0.002). Before stratification into CETP subgroups, a greater % high-intensity activity (upper tertile) was associated with higher HDL-C only in men (1.24 vs 1.19 in lower tertile, P < 0.0005). However, no statistically significant (CETP 1b.-629 x % high-intensity activity) interactions with lipid profile were detected in either gender.

CONCLUSION

The effects of the CETP 1b.-629 A-C polymorphism on blood lipid concentrations appear to be unchanged by the different observed physical activity levels in a mostly sedentary population.

Common genetic variation of the cholesteryl ester transfer protein gene strongly predicts future cardiovascular death in patients with coronary artery disease

OBJECTIVES

We sought to evaluate the association between cholesteryl ester transfer protein (CETP) genotypes and the risk of future cardiovascular mortality in patients with coronary artery disease (CAD).

BACKGROUND

Polymorphisms of the CETP gene influence CETP activity and high-density lipoprotein (HDL) cholesterol concentration and might affect the long-term prognosis and response to statin therapy in patients with CAD.

METHODS

We used serum samples and deoxyribonucleic acid collected at baseline from a prospective cohort of 1,211 patients with CAD prospectively followed up (median follow-up of 4.1 years), 82 of whom experienced a fatal cardiovascular event. The CETP/C-629A and I405V polymorphisms, CETP activity, and HDL cholesterol were determined.

RESULTS

Patients carrying the -629A allele had significantly lower CETP activity and higher HDL cholesterol levels. There was a significant association between this polymorphism and the risk of future cardiovascular death. Mortality decreased from 10.8% in CC homozygotes to 4.6% in CA heterozygotes and 4.0% in AA homozygotes (p < 0.0001). This association was independent of potential confounders, particularly HDL cholesterol and CETP activity levels. The clinical benefit of statin therapy was restricted to CC homozygotes, in whom cardiovascular mortality was divided by half (p = 0.01 for treatment x genotype interaction). Similar trends were observed with the CETP/I405V polymorphism, but these effects seemed to be mainly the consequence of linkage disequilibrium with the CETP/C-629A polymorphism.

CONCLUSIONS

In patients with CAD, the CETP/-629A allele had a strong protective effect on future mortality from cardiovascular causes, independent of its role on HDL cholesterol and CETP activity levels. Additionally, this common polymorphism appeared to predict which patients with CAD will experience a survival benefit from statin therapy.

Natural genetic variation as a tool in understanding the role of CETP in lipid levels and disease

Since the identification of cholesteryl ester transfer protein (CETP), its role in the modulation of HDL levels and cardiovascular disease has been debated. With the early detection of genetic variants followed by the finding of families deficient in CETP, genetic studies have played a large role in the attempts to understand the association of CETP with lipids and disease; however, results of these studies have often led to disparate conclusions. With the availability of a greater variety of genetic polymorphisms and larger studies in which disease has been examined, it is now possible to compare the breadth of CETP genetic studies and draw better conclusions. The most broadly studied polymorphism is TaqIB for which over 10,000 individuals have been genotyped and had HDL levels determined. When these studies are subjected to a meta-analysis, the B2B2 homozygotes are found to have higher HDL levels than B1B1 homozygotes (0.12 mmol/l, 95% CI = 0.11-0.13, P < 0.0001). A similar analysis of the I405V polymorphism yields 0.05 mmol/l higher HDL levels in 405VV homozygotes than in 405II homozygotes (95% CI = 0.03-0.07, P < 0.0001). The implications of these studies for cardiovascular disease will be addressed.

The human cholesteryl ester transfer protein I405V polymorphism is associated with plasma cholesterol concentration and its reduction by dietary phytosterol esters

We examined the relationships of I405V cholesteryl ester transfer protein (CETP), Taq1B CETP and apolipoprotein (apo)E polymorphisms with the pattern of response to dietary plant sterol ester (PSE) by plasma lipids and CETP concentrations as well as lecithin-cholesterol acyltransferase (LCAT) activity. Subjects with moderate primary hypercholesterolemia (20-60 y old; 50 women; 10 men) consumed margarine (20 g/d) without (placebo) or with PSE (2.8 g/d = 1.68 g/d phytosterols) for 4 wk each period, in a crossover, double-blind study. Plasma CETP concentration was measured by ELISA; endogenous LCAT activity was expressed as the percentage of esterification (30 min incubation) of the subjects' (14)C-unesterified cholesterol HDL. PSE reduced concentrations of plasma total cholesterol (TC) (10%) and LDL cholesterol (LDL-C) (12%). In relation to the I405V CETP polymorphism, the percentage reductions in TC with consumption of PSE for the II, IV and VV phenotypes were 7.2, 4.2 and not significant, respectively, whereas LDL-C significant reductions occurred only for II (9.5%). However, the CETP concentration diminished only in the II phenotype.

Haplotype analyses of cholesteryl ester transfer protein gene promoter: a clue to an unsolved mystery of TaqIB polymorphism

Cholesteryl ester transfer protein (CETP) mediates the transfer of cholesteryl esters from HDL to triglyceride-rich lipoproteins. TaqIB polymorphism (B2 allele) identified in intron 1 is associated with lower plasma CETP concentrations and higher HDL cholesterol levels and may play an antiatherogenic role in humans. However, its molecular mechanism remains unclear. To evaluate the association between the promoter polymorphisms and CETP/HDL cholesterol levels, ten novel and three previously reported polymorphisms located within 3.3 kb of the CETP gene promoter were investigated in a sample of 357 elderly Japanese men. All the promoter polymorphisms were in linkage disequilibrium with each other and with TaqIB. The -2505A allele, the "S" allele of the [gaaa](n) repeat ("S" denotes [gaaa](n)=329 bp and longer, "L" denotes >329 bp) and TaqIB2 allele were significantly associated with both lower plasma CETP concentrations and higher HDL cholesterol levels whereas -971G/A and -629A/C were significantly associated with CETP concentrations but not with HDL-C levels. The 12-polymorphism haplotypes consisting of -2804, -2505, [gaaa](n), -1930, -1674, -1129, -1046, -971, -875, -827, -629, and TaqIB were analyzed. These 12 polymorphisms generated eight main haplotypes, accounting for 86% of the observed haplotypes. The G/A/S/T/T/C/T/A/C/C/A/B2 haplotype was significantly associated with lower CETP concentrations (2.0+/-0.6 micro g/ml) and higher HDL cholesterol levels (55.1+/-12.7 mg/dl) than the other seven main haplotypes. The 5- and 3-polymorphism haplotype analyses consisting of -2505 and the [gaaa](n) repeat indicated the -2505C/A polymorphism might explain the variation in the CETP concentrations best, and the [gaaa](n) repeat and/or the -2505C/A polymorphism may independently determine the variation in HDL cholesterol levels, whereas the -629A/C and TaqIB polymorphisms were not instrumental in determining CETP concentrations as well as HDL cholesterol levels, although the latter has been frequently examined in many association studies.

Polymorphisms in the CETP gene and association with CETP mass and HDL levels

The cholesteryl ester transfer protein (CETP) gene has been implicated in the variation of HDL levels but most studies have focused on only one or a few genetic variations. In order to properly understand the role of CETP in determining phenotype, it is necessary to examine the entire gene and all its common polymorphisms. The coding regions, adjacent introns, and proximal 5' and 3' regions were resequenced from an ethnically diverse population. Novel and previously known polymorphisms were then characterized and associations with HDL and CETP mass levels determined. The polymorphism most highly associated with CETP was 629 bp upstream of the transcription start site while the polymorphism most highly associated with HDL was a VNTR 1946 bp upstream of the transcription start site. Genetic variation in the CETP gene is associated with protective HDL levels. The ethnic diversity of some SNPs and complex interplay among them dictate careful analysis of the whole gene prior to conclusions about the role of individual polymorphisms.

Common cholesteryl ester transfer protein gene polymorphisms and the effect of atorvastatin therapy in type 2 diabetes

OBJECTIVE

The cholesteryl ester transfer protein (CETP) plays a key role in the remodeling of triglyceride (TG)-rich and HDL particles. Sequence variations in the CETP gene may interfere with the effect of lipid-lowering treatment in type 2 diabetes.

RESEARCH DESIGN AND METHODS

We performed a 30-week randomized double-blind placebo-controlled trial with atorvastatin 10 mg (A10) and 80 mg (A80) in 217 unrelated patients with diabetes.

RESULTS

CETP TaqIB and A-629C polymorphisms were tightly concordant (P < 0.001). At baseline, B1B1 carriers had lower plasma HDL cholesterol (0.99 +/- 0.2 vs. 1.11 +/- 0.2 mmol/l, P < 0.05), higher CETP mass (2.62 +/- 0.8 vs. 2.05 +/- 0.4 mg/l, P < 0.001), and slightly increased, though not significant, plasma TGs (2.7 +/- 1.05 vs. 2.47 +/- 0.86, P = 0.34) compared with B2B2 carriers. Atorvastatin treatment significantly reduced CETP mass dose-dependently by 18% (A10) and 29% (A80; both vs. placebo P < 0.001, A10-A80 P < 0.001). CETP mass and activity were strongly correlated (r = 0.854, P < 0.0001). CETP TaqIB polymorphism appeared to modify the effect of atorvastatin on HDL cholesterol elevation (B1B1 7.2%, B1B2 6.1%, B2B2 0.5%; P < 0.05), TG reduction (B1B1 39.7%, B1B2 38.4%, B2B2 18.4%; P = 0.08), and CETP mass reduction (B1B1 32.1%, B1B2 29.6%, B2B2 21.9%; P = 0.27, NS). Similar results were obtained for the A-629C polymorphism.

CONCLUSIONS

In conclusion, the B1B1/CC carriers of the CETP polymorphisms have a more atherogenic lipid profile, including low HDL, and they respond better to statin therapy. These results favor the hypothesis that CETP polymorphisms modify the effect of statin treatment and may help to identify patients who will benefit most from statin therapy.

Cholesteryl ester transfer protein: a novel target for raising HDL and inhibiting atherosclerosis

Cholesteryl ester transfer protein (CETP) promotes the transfer of cholesteryl esters from antiatherogenic HDLs to proatherogenic apolipoprotein B (apoB)-containing lipoproteins, including VLDLs, VLDL remnants, IDLs, and LDLs. A deficiency of CETP is associated with increased HDL levels and decreased LDL levels, a profile that is typically antiatherogenic. Studies in rabbits, a species with naturally high levels of CETP, support the therapeutic potential of CETP inhibition as an approach to retarding atherogenesis. Studies in mice, a species that lacks CETP activity, have provided mixed results. Human subjects with heterozygous CETP deficiency and an HDL cholesterol level >60 mg/dL have a reduced risk of coronary heart disease. Evidence that atherosclerosis may be increased in CETP-deficient subjects whose HDL levels are not increased is difficult to interpret and may reflect confounding or bias. Small-molecule inhibitors of CETP have now been tested in human subjects and shown to increase the concentration of HDL cholesterol while decreasing that of LDL cholesterol and apoB. Thus, it seems important and timely to test the hypothesis in randomized trials of humans that pharmacological inhibition of CETP retards the development of atherosclerosis.

The association of cholesteryl ester transfer protein polymorphism with high-density lipoprotein cholesterol and coronary artery disease in Koreans

Cholesteryl ester transfer protein (CETP) is a key protein involved in high-density lipoprotein cholesterol (HDL-C) metabolism. It is known to affect plasma HDL-C levels, and its genetic regulation may be involved in the development of coronary artery disease (CAD). The aim of this study was to determine the frequency of the CETP Taq1B polymorphism in Koreans, and to investigate its relationship with plasma HDL-C levels and CAD. One-hundred and nineteen patients with significant CAD and 106 controls were examined with respect to their genotypes, lipid profiles and other risk factors of CAD. The genotype frequencies of B1B1:B1B2:B2B2 in males and females were 35.5%:50%:14.5% and 34.7%:42.6%:22.7%, respectively, which is comparable to previous reports in other ethnic groups. The B1B1 homozygote was associated with significantly lower HDL-C levels in females (p = 0.049) and non-smoking males (p = 0.037). After controlling for gender, body mass index (BMI) and smoking, the TaqIB polymorphism was still significantly associated with HDL-C levels (p = 0.046) and explained 5.4% of the HDL-C variation in this study. By univariate analysis, the B1B1 homozygote was a significant predictor of CAD (p = 0.043), and this was confirmed by multivariate analysis with traditional risk factors, i.e. the B1B1 homozygote was an independent predictor of CAD (p = 0.026, odds ratio = 1.97, 95% confidence interval: 1.08-3.57). In conclusion, the B1B1 homozygote of the CETP Taq1B polymorphism is associated with low HDL-C levels in females and non-smoking males, and may be an independent genetic risk factor of CAD in the Korean population.

Association testing by DNA pooling: an effective initial screen

With an ever-increasing resource of validated single-nucleotide polymorphisms (SNPs), the limiting factors in genome-wide association analysis have become genotyping capacity and the availability of DNA. We provide a proof of concept of the use of pooled DNA as a means of efficiently screening SNPs and prioritizing them for further study. This approach reduces the final number of SNPs that undergo full, sample-by-sample genotyping as well as the quantity of DNA used overall. We have examined 15 SNPs in the cholesteryl ester transfer protein (CETP) gene, a gene previously demonstrated to be associated with serum high-density lipoprotein cholesterol levels. The SNPs were amplified in two pools of DNA derived from groups of individuals with extremely high and extremely low serum high-density lipoprotein cholesterol levels, respectively. P values <0.05 were obtained for 14 SNPs, supporting the described association. Genotyping of the individual samples showed that the average margin of error in frequency estimate was approximately 4% when pools were used. These findings clearly demonstrate the potential of pooling techniques and their associated technologies as an initial screen in the search for genetic associations.

Gene-environment interaction: a central concept in multifactorial diseases

Unlike the rare and severe genetic defects that cause monogenic diseases, the genetic factors that modulate the individual susceptibility to multifactorial diseases (cardiovascular diseases, cancers, diabetes, etc.) are common, functionally different, forms of genes (polymorphisms), which generally have a modest effect at an individual level but, because of their high frequency in the population, can be associated with a high attributable risk. Environmental factors can reveal or facilitate the phenotypic expression of such susceptibility genes. Indeed, in common diseases genetic effects can be considerably amplified in the presence of triggering factors. There is now accumulating evidence that most of the susceptibility genes for common diseases do not have a primary aetiological role in predisposition to disease, but rather act as response modifiers to exogenous factors such as stress, environment, disease, drug intake. A better characterisation of the interactions between environmental and genetic factors constitute a key issue in the understanding of the pathogenesis of multifactorial diseases. The present paper will review three examples of gene-environment interactions in the field of CHD.

Abundant raw material for cis-regulatory evolution in humans

Changes in gene expression and regulation--due in particular to the evolution of cis-regulatory DNA sequences--may underlie many evolutionary changes in phenotypes, yet little is known about the distribution of such variation in populations. We present in this study the first survey of experimentally validated functional cis-regulatory polymorphism. These data are derived from more than 140 polymorphisms involved in the regulation of 107 genes in Homo sapiens, the eukaryote species with the most available data. We find that functional cis-regulatory variation is widespread in the human genome and that the consequent variation in gene expression is twofold or greater for 63% of the genes surveyed. Transcription factor-DNA interactions are highly polymorphic, and regulatory interactions have been gained and lost within human populations. On average, humans are heterozygous at more functional cis-regulatory sites (>16,000) than at amino acid positions (<13,000), in part because of an overrepresentation among the former in multiallelic tandem repeat variation, especially (AC)(n) dinucleotide microsatellites. The role of microsatellites in gene expression variation may provide a larger store of heritable phenotypic variation, and a more rapid mutational input of such variation, than has been realized. Finally, we outline the distinctive consequences of cis-regulatory variation for the genotype-phenotype relationship, including ubiquitous epistasis and genotype-by-environment interactions, as well as underappreciated modes of pleiotropy and overdominance. Ordinary small-scale mutations contribute to pervasive variation in transcription rates and consequently to patterns of human phenotypic variation.

A prospective study of TaqIB polymorphism in the gene coding for cholesteryl ester transfer protein and risk of myocardial infarction in middle-aged men

BACKGROUND

Molecular variations in the gene coding for the cholesteryl ester transfer protein (CETP) such as the TaqIB polymorphism are associated with higher plasma high-density lipoprotein (HDL) concentration. However, whether this polymorphism is associated with risk of myocardial infarction (MI) is uncertain.

METHODS AND RESULTS

In a prospective cohort of 14916 apparently healthy men enrolled in the Physicians' Health Study, allelic status for the TaqIB polymorphism in the CETP gene was determined among 384 participants who subsequently developed a first MI (cases) and among an equal number of age and smoking-matched participants who remained free of cardiovascular disease during follow-up (controls). Overall, the B2B2 genotype was present in 17% of the study participants and was associated with higher HDL cholesterol levels (mean mg/dl [+/- S.D.], 45 +/- 11 for the B1B1 genotype, 48 +/- 13 for the B1B2 genotype and 50 +/- 12 for the B2B2 genotype; P=0.01). However, the risk of developing MI did not differ significantly across these three genotypes. After adjustment for coronary risk factors (but not HDL), the relative risks for future MI were 1.12(95% CI 0.74-1.70) for the B1B2 genotype and 0.95(95% CI 0.54-1.66) for the B2B2 genotype, compared with the B1B1 genotype. In subgroup analysis of individuals with low HDL levels, B2B2 genotype appeared to have a lower risk of MI compared with the B1B1 genotype. However, participants with high HDL were at lower risk of developing MI regardless of their CETP genotype.

CONCLUSIONS

In this prospective study of apparently healthy middle-aged US men, carriers of the B2 allele of the TaqIB in the CETP gene had higher HDL concentrations, but did not have lower risk of MI.

CONDENSED ABSTRACT

In a cohort of apparently healthy middle-aged US men, the relation between CETP genotype and MI risk was prospectively examined in a nested case-control study. After adjusting for coronary risk factors (but not HDL), the 9-year risk of developing MI did not differ significantly by genotype. Comparing to the B1B1 genotype, the relative risks for future MI were 1.12 (95% CI 0.74-1.70) for the B1B2 genotype and 0.95 (95% CI 0.54-1.66) for the B2B2 genotype.

A novel cholesteryl ester transfer protein promoter polymorphism (-971G/A) associated with plasma high-density lipoprotein cholesterol levels. Interaction with the TaqIB and -629C/A polymorphisms

The plasma cholesteryl ester transfer protein (CETP) plays a key role in reverse cholesterol transport (RCT) by mediating the transfer of cholesteryl ester (CE) from high-density lipoprotein (HDL) to atherogenic ApoB-containing lipoproteins, including VLDL, IDL and LDL. We describe a new polymorphism located at position -971 in the human CETP gene promoter, which corresponds to a G/A substitution at a potential AvaI restriction site. The relationship between the -971G/A polymorphism, plasma lipid parameters and plasma CETP concentration was evaluated in the Etude Cas-Témoins de l'Infarctus du Myocarde (control-myocardial infarction cases) cohort, and revealed that the -971G/A polymorphism (A allele frequency: 0.491) was significantly associated with both plasma high-density lipoprotein cholesterol (HDL-C) levels and CETP concentration (P=0.006 and 0.009, respectively). Subjects with genotype -971GG displayed both low HDL-C levels and high plasma CETP concentration, while genotype -971AA subjects displayed the inverse relationship. Evaluation of potential interactions between the -971G/A and the -629C/A or TaqIB polymorphisms demonstrated that the -971G/A polymorphism interacts significantly with the functional -629C/A site and the TaqIB polymorphism with respect to plasma HDL-C levels (P=0.0014 and 0.012, respectively), but does not affect plasma CETP concentration. These results clearly suggest that the interaction between the 971G/A polymorphism and either the -629C/A or the TaqIB polymorphism on plasma CETP concentration is different than that implicated in HDL-C levels. Transient transfection of HepG2 cells revealed that the -971G/A polymorphism did not modulate transcriptional activity of the human CETP gene promoter. The -971G/A promoter polymorphism therefore constitutes a non-functional marker. Furthermore, the observed effects of the -971G/A polymorphism on both plasma CETP concentration and HDL-C levels are due to functional variants in linkage disequilibrium with it. Our findings strongly suggest the existence of as yet unidentified functional polymorphisms in the CETP gene promoter that could explain the association between specific polymorphisms of the CETP gene and both plasma HDL-C and CETP concentrations.

Polyunsaturated fatty acids modulate the effects of the APOA1 G-A polymorphism on HDL-cholesterol concentrations in a sex-specific manner: the Framingham Study

BACKGROUND

A common G-to-A substitution in the promoter area (-75 base pairs) of the apolipoprotein A-I gene (APOA1) has been described. The A allele was shown to be associated with higher HDL-cholesterol concentrations in some studies but not in others.

OBJECTIVE

We examined whether dietary fat modulates the association between this polymorphism and HDL-cholesterol concentrations.

DESIGN

We studied a population-based sample of 755 men and 822 women from the Framingham Offspring Study.

RESULTS

The frequency of the A allele was 0.165. No significant differences were observed between G/G subjects and carriers of the A allele for any lipid variables. In multivariate linear regression models, HDL-cholesterol concentrations in women were associated with a significant interaction between polyunsaturated fatty acid (PUFA) intake as a continuous variable and APOA1 genotype (P = 0.005). By using 3 categories of PUFA intake, we found a significantly different effect of APOA1 genotype across PUFA categories in women. When PUFA intake was <4% of energy, G/G subjects had approximately 14% higher HDL-cholesterol concentrations than did carriers of the A allele (P < 0.05). Conversely, when PUFA intake was >8%, HDL-cholesterol concentrations in carriers of the A allele were 13% higher than those of G/G subjects (P < 0.05). No significant allelic difference was observed for subjects in the range of PUFA intake of 4-8% of energy. These interactions were not significant in men.

CONCLUSIONS

We found a significant gene-diet interaction associated with the APOA1 G-A polymorphism. In women carriers of the A allele, higher PUFA intakes were associated with higher HDL-cholesterol concentrations, whereas the opposite effect was observed in G/G women.

O componente genético da determinação dos lipídeos séricos

Os níveis de lipídeos séricos são características multifatoriais determinadas por um grande número de fatores genéticos e ambientais. A identificação do componente genético dessas características tem sido intensamente investigada nos últimos anos. Esses estudos têm enfocado principalmente polimorfismos nos genes que codificam proteínas estruturais e enzimas relacionadas com o metabolismo de lipídeos. Estudos mais recentes mostraram que o efeito desses polimorfismos depende em parte das interações dos diferentes genótipos com os fatores de risco clássicos tais como tabagismo, sobrepeso ou sedentarismo. A variabilidade encontrada nesses genes parece também influir na resposta a fármacos comumente utilizados no tratamento das hiperlipidemias.

Cholesteryl ester transfer protein, high density lipoprotein and arterial disease

The reported relationships between cholesteryl ester transfer protein, high density lipoproteins and arterial disease are confusing and conflicting. Several papers published during the review period add substantially to the evidence base regarding the atherogenicity (or anti-atherogenicity) of cholesteryl ester transfer protein, although none clearly resolves the continuing conflict. These new papers are presented against the backdrop of the previous state of knowledge.

Variation at the cholesteryl ester transfer protein gene in relation to plasma high density lipoproteins cholesterol levels and carotid intima-media thickness

BACKGROUND

Cholesteryl ester transfer protein (CETP) plays a major role in lipoprotein metabolism. We have screened the CETP gene for mutations and polymorphisms regulating high density lipoproteins cholesterol (HDL-C) levels and the development of atherosclerosis, and found some polymorphisms (I405V and R451Q) to have minor effects.

DESIGN

The purpose of this study was to investigate the combined effect of the several polymorphisms of the CETP gene so far found on HDL-C levels and carotid intima-media thickness (IMT), and, in addition, to study whether the recently found functional polymorphism in the promoter region of the CETP gene (C to A, - 629 relative to the first transcribed nucleotide) explains the previous associations due to linkage disequilibrium. The genotypes were determined in a population sample of 481 men and women.

RESULTS

There were no significant differences in plasma CETP activity or carotid IMT between the genotypes of the promoter polymorphism. The women with the CC genotype of the promoter polymorphism had the lowest HDL-C levels (P < 0.001), but no such difference was seen in men. Detected polymorphisms of the CETP gene explained about 8% of the variation in HDL-C in women and about 7 and 10% of the variation in carotid IMT in women and men, respectively. The associations of the promoter, I405V and R451Q-A373P polymorphisms with HDL-C and carotid IMT seemed to be independent of each other. The associations with IMT were independent of total HDL-C levels, suggesting that HDL subfractions may have more effect on IMT.

CONCLUSION

The CETP gene locus was found to be polymorphic and its polymorphisms explained a reasonable proportion of the variation in the degree of carotid atherosclerosis.