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

No association between LDL receptor and CETP genetic variants and atorvastatin response in Jordanian hyperlipidemic patients

OBJECTIVES

Atorvastatin is commonly used medication to achieve low levels of low-density lipoproteins (LDL). Cholesteryl ester transfer protein (CETP) and LDL receptor (LDLR) genetic variants can affect the cholesterol transport and hence may affect on atorvastatin response. This study aimed to investigate the influence of LDLR AvaII, CETP TaqIb, and Rs1532624 on the efficacy of 20 mg atorvastatin among Jordanian hyperlipidemic patients.

METHODS

One hundred and 50 blood samples were collected from hyperlipidemic patients in the University of Jordan Hospital. Polymerase chain reaction-restriction fragment length polymorphism was used for genotyping of LDLR AvaII and CETP TaqIb genetic variants. The genotyping of CETP Rs1532624 variant was done by Sanger DNA-Sequencing.

RESULTS

LDLR AvaII and CETP TaqIb and Rs1532624 variants showed a significant (p value < 0.05) association with the baseline of the LDL at the time of diagnoses. On the other hand, none of the tested genetic variants showed a significant (p value>0.05) association with LDL reduction after atorvastatin therapy.

CONCLUSIONS

Results demonstrated a significant association between the LDLR AvaII and CETP TaqIb, and Rs1532624 genetic variants with the LDL baseline level. However, the atorvastatin therapy among hyperlipidemic patients of Jordanian origin was not affected by any of the tested variants.

Hyperalphalipoproteinemia and Beyond: The Role of HDL in Cardiovascular Diseases

Hyperalphalipoproteinemia (HALP) is a lipid disorder characterized by elevated plasma high-density lipoprotein cholesterol (HDL-C) levels above the 90th percentile of the distribution of HDL-C values in the general population. Secondary non-genetic factors such as drugs, pregnancy, alcohol intake, and liver diseases might induce HDL increases. Primary forms of HALP are caused by mutations in the genes coding for cholesteryl ester transfer protein (CETP), hepatic lipase (HL), apolipoprotein C-III (apo C-III), scavenger receptor class B type I (SR-BI) and endothelial lipase (EL). However, in the last decades, genome-wide association studies (GWAS) have also suggested a polygenic inheritance of hyperalphalipoproteinemia. Epidemiological studies have suggested that HDL-C is inversely correlated with cardiovascular (CV) risk, but recent Mendelian randomization data have shown a lack of atheroprotective causal effects of HDL-C. This review will focus on primary forms of HALP, the role of polygenic inheritance on HDL-C, associated risk for cardiovascular diseases and possible treatment options.

Common genetic variation in obesity, lipid transfer genes and risk of Metabolic Syndrome: Results from IDEFICS/I.Family study and meta-analysis

As the prevalence of metabolic syndrome (MetS) in children and young adults is increasing, a better understanding of genetics that underlie MetS will provide critical insights into the origin of the disease. We examined associations of common genetic variants and repeated MetS score from early childhood to adolescence in a pan-European, prospective IDEFICS/I.Family cohort study with baseline survey and follow-up examinations after two and six years. We tested associations in 3067 children using a linear mixed model and confirmed the results with meta-analysis of identified SNPs. With a stringent Bonferroni adjustment for multiple comparisons we obtained significant associations(p < 1.4 × 10⁻⁴) for 5 SNPs, which were in high LD (r² > 0.85) in the 16q12.2 non-coding intronic chromosomal region of FTO gene with strongest association observed for rs8050136 (effect size(β) = 0.31, p_Wald = 1.52 × 10⁻⁵). We also observed a strong association of rs708272 in CETP with increased HDL (p = 5.63 × 10⁻⁴⁰) and decreased TRG (p = 9.60 × 10⁻⁵) levels. These findings along with meta-analysis advance etiologic understanding of childhood MetS, highlighting that genetic predisposition to MetS is largely driven by genes of obesity and lipid metabolism. Inclusion of the associated genetic variants in polygenic scores for MetS may prove to be fundamental for identifying children and subsequently adults of the high-risk group to allow earlier targeted interventions.

Genome-Wide Association Study of Metabolic Syndrome Reveals Primary Genetic Variants at CETP Locus in Indians

Indians, a rapidly growing population, constitute vast genetic heterogeneity to that of Western population; however they have become a sedentary population in past decades due to rapid urbanization ensuing in the amplified prevalence of metabolic syndrome (MetS). We performed a genome-wide association study (GWAS) of MetS in 10,093 Indian individuals (6,617 MetS and 3,476 controls) of Indo-European origin, that belong to our previous biorepository of The Indian Diabetes Consortium (INDICO). The study was conducted in two stages-discovery phase (N = 2,158) and replication phase (N = 7,935). We discovered two variants within/near the CETP gene-rs1800775 and rs3816117-associated with MetS at genome-wide significance level during replication phase in Indians. Additional CETP loci rs7205804, rs1532624, rs3764261, rs247617, and rs173539 also cropped up as modest signals in Indians. Haplotype association analysis revealed GCCCAGC as the strongest haplotype within the CETP locus constituting all seven CETP signals. In combined analysis, we perceived a novel and functionally relevant sub-GWAS significant locus-rs16890462 in the vicinity of SFRP1 gene. Overlaying gene regulatory data from ENCODE database revealed that single nucleotide polymorphism (SNP) rs16890462 resides in repressive chromatin in human subcutaneous adipose tissue as characterized by the enrichment of H3K27me3 and CTCF marks (repressive gene marks) and diminished H3K36me3 marks (activation gene marks). The variant displayed active DNA methylation marks in adipose tissue, suggesting its likely regulatory activity. Further, the variant also disrupts a potential binding site of a key transcription factor, NRF2, which is known for involvement in obesity and metabolic syndrome.

Association of a cholesteryl ester transfer protein variant (rs1800777) with fat mass, HDL cholesterol levels, and metabolic syndrome

BACKGROUND

There is little evidence of the association between CETP SNPs and obesity and/or related metabolic parameters.

OBJECTIVE

To analyze the association of the polymorphism rs1800777 of the CETP gene with anthropometric parameters, lipid profile, metabolic syndrome and its components, and adipokine levels in obese subjects without type 2 diabetes mellitus or hypertension.

DESIGN

A population of 1005 obese subjects was analyzed. Electrical bioimpedance was performed, and blood pressure, presence of metabolic syndrome, dietary intake, physical activity, and biochemical tests were recorded.

RESULTS

Nine hundred and sixty eight patients (96.3%) had the GG genotype, 37 patients the GA genotype (3.7%) (no AA genotype was detected). Fat mass (delta: 4.4±1.1kg; p=0.04), waist circumference (delta: 5.6±2.1cm; p=0.02), and waist to hip ratio (delta: 0.04±0.01cm; p=0.01) were higher in A allele carriers than in non-A allele carriers. HDL cholesterol levels were lower in A allele carriers than in non-A allele carriers (delta: 4.2±1.0mg/dL; p=0.04). In the logistic regression analysis, the GA genotype was associated to an increased risk of central obesity (OR 7.55, 95% CI 1.10-55.70, p=0.02) and low HDL cholesterol levels (OR 2.46, 95% CI 1.23-4.91, p=0.014).

CONCLUSION

The CETP variant at position +82 is associated to lower HDL cholesterol levels, increased fat mass, and central obesity in obese subjects. These results may suggest a potential role of this variant gene in pathophysiology of adipose tissue.

Association between Six CETP Polymorphisms and Metabolic Syndrome in Uyghur Adults from Xinjiang, China

OBJECTIVE

To explore the association between CETP gene polymorphisms and metabolic syndrome (MS), as well as the relationship between the CETP gene polymorphisms and each component of MS.

METHODS

A total of 571 individuals which were randomly selected from 5692 Uyghur adults were subdivided into two groups, including 280 patients with MS and 291 control subjects, using the group-matching method after matching for gender. We detected CETP polymorphisms (rs5882, rs1800775, rs3764261, rs12149545, rs711752, and rs708272) by using the Snapshot method.

RESULTS

(1) Significant differences were found involving the frequency distribution of genotypes and alleles of rs1800775, rs3764261, rs12149545, rs711752, and rs708272 between the control and MS groups (all p < 0.05). (2) rs1800775, rs3764261, rs12149545, rs711752, and rs708272 polymorphisms were significantly related to the risk of MS (all p < 0.05). (3) The rs1800775 polymorphism was associated with high fasting blood glucose levels and low high density lipoprotein cholesterol (HDL-C); rs3764261 and rs12149545 polymorphisms were associated with all components of MS except high blood pressure; rs711752 and rs708272 polymorphisms were associated with low HDL-C (all p < 0.05). (4) Complete linkage disequilibrium (LD) was identified for two pairs of single nucleotide polymorphisms (SNPs) (rs3764261 and rs12149545 (D' = 1.000, r² = 0.931), rs711752 and rs708272 (D' = 1.000, r² = 0.996)). (5) The A-G-G-G-C (p = 0.013, odds ratio [OR] = 0.622, 95% confidence interval [95% CI] = 0.427-0.906) and A-T-A-A-T (p < 0.001, OR = 0.519, 95% CI = 0.386-0.697) haplotypes were more frequent in the control group than in the case group. Conclusions: The rs1800775, rs3764261, rs12149545, rs711752, and rs708272 polymorphisms of CETP were associated with MS and its components among the Uyghur ethnic group. Complete LD was found between two pairs of SNPs (rs3764261 and rs12149545, rs711752, and rs708272). The A-G-G-G-C and A-T-A-A-T haplotypes might be protective factors for MS.

Cholesterol ester transfer protein (CETP) gene polymorphism and selected parameters of lipid metabolism in children from families with history of cardiovascular system diseases

BACKGROUND

Children from families with a history of cardiovascular system diseases are especially predisposed to early development of atherosclerosis. Therefore, the aim of this study was to examine the selected lipid parameters and polymorphisms of G279A located in the cholesterol ester transfer protein (CETP) gene.

MATERIAL/METHODS

This longitudinal study was performed in 3 stages. During stage I the tests were carried out on 137 newborns after birth. Of these, we selected 30 children with a family history of cardiovascular system diseases. During stage II of the study the same children were evaluated at the age of 18-30 months, and during stage III at the age 5-6 years. Gestational age and the birth weight were evaluated in newborns. The older children were examined physically, and nutritional status was assessed. In all of the children examined, we determined the blood concentrations of triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, apolipoproteins (AI and B), lipoprotein(a) and polymorphisms, and the G279A locus of the CETP gene.

RESULTS

In children with genotype B1B1 (after birth and aged 5-6 years), a significantly lower cholesterol concentration in the HDL fraction was found compared to those with genotype B1B2 and B2B2. Other biochemical parameters of lipid metabolism were not significantly different between these genetic polymorphisms.

CONCLUSIONS

A lower cholesterol concentration in the HDL fraction in children with a family history of cardiovascular system diseases was determined by polymorphism of the CETP gene. Homozygotes (genotype B1B1) show a tendency towards the phenotype favoring the development of atherosclerosis.

Cholesteryl Ester Transfer Protein (CETP) polymorphisms affect mRNA splicing, HDL levels, and sex-dependent cardiovascular risk

Polymorphisms in and around the Cholesteryl Ester Transfer Protein (CETP) gene have been associated with HDL levels, risk for coronary artery disease (CAD), and response to therapy. The mechanism of action of these polymorphisms has yet to be defined. We used mRNA allelic expression and splice isoform measurements in human liver tissues to identify the genetic variants affecting CETP levels. Allelic CETP mRNA expression ratios in 56 human livers were strongly associated with several variants 2.5-7 kb upstream of the transcription start site (e.g., rs247616 p = 6.4 × 10(-5), allele frequency 33%). In addition, a common alternatively spliced CETP isoform lacking exon 9 (Δ9), has been shown to prevent CETP secretion in a dominant-negative manner. The Δ 9 expression ranged from 10 to 48% of total CETP mRNA in 94 livers. Increased formation of this isoform was exclusively associated with an exon 9 polymorphism rs5883-C>T (p = 6.8 × 10(-10)) and intron 8 polymorphism rs9930761-T>C (5.6 × 10(-8)) (in high linkage disequilibrium with allele frequencies 6-7%). rs9930761 changes a key splicing branch point nucleotide in intron 8, while rs5883 alters an exonic splicing enhancer sequence in exon 9.The effect of these polymorphisms was evaluated in two clinical studies. In the Whitehall II study of 4745 subjects, both rs247616 and rs5883T/rs9930761C were independently associated with increased HDL-C levels in males with similar effect size (rs247616 p = 9.6 × 10(-28) and rs5883 p = 8.6 × 10(-10), adjusted for rs247616). In an independent multiethnic US cohort of hypertensive subjects with CAD (INVEST-GENE), rs5883T/rs9930761C alone were significantly associated with increased incidence of MI, stroke, and all-cause mortality in males (rs5883: OR 2.36 (CI 1.29-4.30), p = 0.005, n = 866). These variants did not reach significance in females in either study. Similar to earlier results linking low CETP activity with poor outcomes in males, our results suggest genetic, sex-dependent CETP splicing effects on cardiovascular risk by a mechanism independent of circulating HDL-C levels.

Association between diet and polymorphisms in individuals with statin-controlled dyslipidaemia grouped according to oxidative stress biomarkers

The objective of this study was to investigate whether differences in diet and in single-nucleotide polymorphisms (SNPs) found in paraoxonase-1 (PON-1), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), cholesterol ester transfer protein (CETP) and apolipoprotein E (APOE) genes, are associated with oxidative stress biomarkers and consequently with susceptibility of low-density cholesterol (LDL) to oxidation. A multivariate approach was applied to a group of 55 patients according to three biomarkers: plasma antioxidant activity, malondialdehyde and oxidized LDL (oxLDL) concentrations. Individuals classified in Cluster III showed the worst prognoses in terms of antioxidant activity and oxidative status. Individuals classified in Cluster I presented the lowest oxidative status, while individuals grouped in Cluster II presented the highest levels of antioxidant activity. No difference in nutrient intake was observed among the clusters. Significantly higher γ- and δ-tocopherol concentrations were observed in those individuals with the highest levels of antioxidant activity. No single linear regression was statistically significant, suggesting that mutant alleles of the SNPs selected did not contribute to the differences observed in oxidative stress response. Although not statistically significant, the p value of the APO E coefficient for oxLDL response was 0.096, indicating that patients who carry the TT allele of the APO E gene tend to present lower plasma oxLDL concentrations. Therefore, the differences in oxidative stress levels observed in this study could not be attributed to diet or to the variant alleles of PON-1, CETP, HMGCR or APO E. This data supports the influence of γ-tocopherol and δ-tocopherol on antioxidant activity, and highlights the need for further studies investigating APO E alleles and LDL oxidation.

TAQIB and I405V polymorphisms of CETP are moderately associated with obesity risk in the Chinese adult population

Associations between the TAQIB and I405V polymorphisms and obesity risk were studied for a single locus as well as in combination. A total of 934 obese subjects and 924 normal controls were included in the study. TAQIB was associated with high-density lipoprotein (HDL) levels (P < 0.001), while I405V was associated with levels of low-density lipoprotein (P = 0.03) and total cholesterol (P = 0.007). Less common alleles of TAQIB and I405V were associated with decreased obesity risk and further drops in odds ratio (OR) were observed in carriers with rare homozygous alleles on both loci (OR = 0.659, P = 0.02). The TAQIB B2 allele was associated with reductions in both hip circumference (P = 0.034) and triceps skinfold thickness (TST) (P = 0.045), although this effect was completely abolished after controlling for HDL levels. The 405V variant was associated with reductions in hip circumference (P = 0.031), body fat composition (P = 0.039) and TST (P = 0.036); these effects were weakened (P < 0.1) after controlling for HDL levels. In conclusion, less common alleles of TAQIB and I405V appear to be modestly associated with obesity risk in an adult Chinese population. Adjustments for HDL levels completely (TAQIB) or partially (I405V) abolished the observed association.

Gene-environment interactions of CETP gene variation in a high cardiovascular risk Mediterranean population

Genome-wide association studies show that cholesteryl ester transfer protein (CETP) single nucleotide polymorphisms (SNPs) are more strongly associated with HDL cholesterol (HDL-C) concentrations than any other loci across the genome. However, gene-environment interactions for clinical applications are still largely unknown. We studied gene-environment interactions between CETP SNPs and dietary fat intake, adherence to the Mediterranean diet, alcohol consumption, smoking, obesity, and diabetes on HDL-C in 4,210 high cardiovascular risk subjects from a Mediterranean population. We focused on the -4,502C>T and the TaqIB SNPs in partial linkage disequilibrium (D'= 0.88; P < 0.001). They were independently associated with higher HDL-C (P < 0.001); this clinically relevant association was greater when their diplotype was considered (14% higher in TT/B2B2 vs. CC/B1B1). No gene-gene interaction was observed. We also analyzed the association of these SNPs with blood pressure, and no clinically relevant associations were detected. No statistically significant interactions of these SNPs with obesity, diabetes, and smoking in determining HDL-C concentrations were found. Likewise, alcohol, dietary fat, and adherence to the Mediterranean diet did not statistically interact with the CETP variants (independently or as diplotype) in determining HDL-C. In conclusion, the strong association of the CETP SNPs and HDL-C was not statistically modified by diet or by the other environmental factors.

Association of two CETP polymorphisms with HDL levels in the Chinese obese population

The association of two cholesterol ester transfer protein (CETP) polymorphisms, D442G and TAQIB (B1-->B2), with high-density lipoprotein (HDL) levels in 932 Chinese obese individuals (BMI >or= 27) was investigated in comparison with normal controls (BMI <or= 24). Independent association was demonstrated for TAQIB minor allele B2 and CETP442 minor allele G with elevated HDL levels. The CETP D442G polymorphism was associated with a much greater increase in HDL levels in subjects with BMI exceeding 27 kg/m(2) (+5.42 mg/dl, P = 0.0007) compared to normal controls (+1.97 mg/dl, P = 0.275), and the increase in HDL reached the highest level among subjects with BMI exceeding 30 kg/m(2) (+6.80 mg/dl, P = 0.016). TAQIB showed significant association with HDL levels only in normal BMI subgroup (P = 0.0017). TAQIB significantly interacted with serum triglyceride (TG) on modulating HDL levels (P = 0.027). The TAQIB-TG interaction effect remained marginally significant after controlling for BMI (P = 0.057). We conclude that D442G polymorphism is associated with more HDL elevation in obesity. TAQIB interacts with serum TG on modulating HDL levels, and the interaction is partly independent of BMI.

Cholesteryl ester transfer protein TaqIB, -629C>A and I405V polymorphisms and risk of coronary heart disease in an Indian population

BACKGROUND

Polymorphisms in cholesteryl ester protein gene have been linked to risk of coronary heart disease (CHD) in many world populations through their effect on reverse cholesterol transport.

METHODS

Five hundred four (504) unrelated electrocardiograph confirmed cases of CHD and 338 population based controls, matched by age and gender, belonging to the Tamilian population of south India were genotyped for polymorphisms in CETP gene using PCR RFLP methods.

RESULTS

The multivariate logistic regression analyses demonstrated that CETP B1B1 and CA genotypes of TaqIB and -629C>A were significantly associated with increased risk for CHD (odds ratio (OR) 2.7; 95% confidence intervals (CI) (1.5-3.3); OR 1.5 (1.1-2.4)) respectively. Combined wild genotypes of CETP gene showed an association with CHD (OR-1.7 (1.0-2.9) as well as the combined heterozygous mutants (OR 1.5 (1.0-2.3); p-0.03). Subgroup analysis based on gender revealed that men harboring CETP B1B1 and CA genotypes have a significant risk for CHD B1B1- 2.7 (1.7-4.3), CA-1.8 (1.3-2.6). There was no link between CETP I450V polymorphism and CHD. Analysis based on hypertensive status showed a significant association between these polymorphisms and non hypertensive CHD patients.

CONCLUSIONS

The risk in non hypertensive and male CHD patients is higher in the presence of CETP B1B1 and CA genotypes.

Associations of genetic variants in ATP-binding cassette A1 and cholesteryl ester transfer protein and differences in lipoprotein subclasses in the multi-ethnic study of atherosclerosis

BACKGROUND

ATP-binding cassette A1 (ABCA1) and cholesteryl ester transfer protein (CETP) play important roles in the reverse cholesterol transport pathway. The associations of ABCA1 and CETP polymorphisms with lipoprotein subclasses have not been extensively studied.

METHODS

We genotyped 2 ABCA1 and 5 CETP polymorphisms in 999 participants of the Multi-Ethnic Study of Atherosclerosis (MESA) and studied their associations with HDL and LDL subclass particle concentrations, measured by nuclear magnetic resonance spectroscopy.

RESULTS

ABCA1 and CETP polymorphisms were associated with different and distinct changes in lipoprotein subclass concentrations. The ABCA1 1051G/A AA genotype, previously found to be associated with cardioprotective effects in this cohort, was associated with a 5.5% higher concentration of small HDL particles (P = 0.024). The CETP TaqIB B2B2, -2505C/A AA, and -629C/A AA genotypes, previously demonstrated to lack cardioprotective effects, were associated with 15.2%, 15.4%, and 11.7% higher HDL cholesterol concentrations, respectively, and 36.5%, 40.7%, and 25.4% higher large HDL particle concentrations (P < 0.0001). The minor alleles of the A373P and R451Q polymorphisms were associated with lower large HDL particle concentrations.

CONCLUSIONS

Our study of the influence of ABCA1 and CETP genetic variants on lipoprotein subclasses demonstrates the importance of interpreting lipoprotein subclasses within the context of the biochemical processes involved in the alterations. In the case of HDL, the study of subclass particle numbers and sizes may not be sufficiently informative. Assays for HDL function may be needed to supplement quantification of HDL cholesterol and HDL particle numbers and sizes.

One common polymorphism of cholesteryl ester transfer protein gene in Iranian subjects with and without primary hypertriglyceridemia

Primary hypertriglyceridemia is considered to be a major risk factor for pancreatitis, atherosclerosis and coronary heart disease. Cholesteryl ester transfer protein gene polymorphisms known to be associated with changes in lipid levels. This study was performed by using polymerase chain reaction and restriction fragment length polymorphisms. Genotype distribution and allelic frequencies of polymorphism were determined and compared in primary hypertriglyceridemic and normotriglyceridemic subjects. The results showed that plasma cholesteryl ester transfer protein activity was significantly higher in primary hypertriglyceridemia than in controls (p = 0.001). In this study all individuals with B2B2 genotype had lower plasma cholesteryl ester transfer protein activity, higher high-density lipoprotein than B1B1 and B1B2 genotypes, whereas triglyceride was significantly decreased in this genotype. The genotype and allelic frequencies for this polymorphism differed significantly between primary hypertriglyceridemic patients and controls (p = 0.014 and p = 0.027, respectively). In both groups, CETP Taq 1B polymorphism (presence of B2 allele) correlated significantly with HDL-C (r = 0.207 and 0.300 in control and patient groups, respectively) and CETP activity (r = -0.193 for controls and r = -0.132 for patients). Taq 1B polymorphism of cholesteryl ester transfer protein gene was associated with changes in lipids profile and plasma cholesteryl ester transfer protein activity in the selected population.

Cholesteryl ester transfer protein (CETP) genetic variation and early onset of non-fatal myocardial infarction

Although Cholesteryl Ester Transfer Protein (CETP) mediates the transfer of cholesteryl esters and triglycerides between lipoprotein particles and thus plays a crucial role in reverse cholesterol transport, the association of variations in the CETP gene with acute myocardial infarction (MI) remains unclear. In this study we examined whether common genetic variation in the CETP gene is related to early-onset non-fatal MI risk in a population-based case-control study from western Washington State. Genotyping for the CETP -2708 G/A, -971 A/G, -629 A/C, Intron-I TaqI G/A and exon-14 A/G (I405V) SNPs was performed in 578 cases with first acute non-fatal MI and in 666 demographically similar controls, free of clinical cardiovascular disease, identified randomly from the community. In-person interviews and non-fasting blood specimens provided data on coronary heart disease risk factors. In men, there was little evidence for an association between single SNPs and MI risk, but in women the age- and race-adjusted OR was found to be significant in 4 out of the 5 CETP single variants. Haplotype analysis revealed two haplotypes associated with MI risk among men. As compared to men homozygous for the most common haplotype D (-2708 G, -971 G, -629 C, TaqI G and exon-14 A), the fully-adjusted multiplicative model identified haplotype G (-2708 G, -971 A, -629 A, TaqI G and exon-14 G) was associated with a 4.0-6.0-fold increased risk of MI for each additional copy; [95%CI 2.4-14.8] and haplotype B (-2708 G, -971 G, -629 A, TaqI A and exon-14 A) showed a significant decreased risk for early onset MI [OR = 0.18; 95%CI 0.04 - 0.75]. An evolutionary-based haplotype analysis indicated that the two haplotypes associated with the MI risk are most evolutionarily divergent from the other haplotypes. Variation at the CETP gene locus is associated with the risk of early-onset non-fatal MI. This association was found to be independent of HDL-C levels. These data and the sex-specific findings require confirmation in other populations.

Cholesteryl ester transfer protein genetic polymorphisms, HDL cholesterol, and subclinical cardiovascular disease in the Multi-Ethnic Study of Atherosclerosis

The cholesteryl ester transfer protein (CETP) plays a key role in high-density lipoprotein (HDL) metabolism. Genetic variants that alter CETP activity and concentration may cause significant alterations in HDL-cholesterol (HDL-C) concentration; however, controversies remain about whether these genetic variants are associated with atherosclerosis. We genotyped the CETP R451Q, A373P, -629C/A, Taq1B, and -2505C/A polymorphisms in a cohort of Caucasian, Chinese, African-American, and Hispanic individuals within the Multi-Ethnic Study of Atherosclerosis. Genotypes were examined in relationship to HDL-C, CETP activity, CETP concentration, and three measures of subclinical cardiovascular disease (CVD): coronary artery calcium (CAC) measured by fast CT scanning, carotid intimal-medial thickness (IMT), and carotid artery plaque measured by ultrasonography. Carriers of the 451Q and 373P alleles have a significantly higher CETP concentration (22.4% and 19.5%, respectively; p<0.001) and activity (13.1% and 9.4%, respectively; p<0.01) and lower HDL-C (5.6% and 6.0%, respectively; p<0.05). The minor alleles of the R451Q and A373P polymorphisms are associated with the presence of CAC, even after adjusting for CVD risk factors and HDL-C (p=0.006 and p=0.01, respectively). The R451Q polymorphism is also associated with presence of carotid artery plaque (p=0.036). Polymorphism is associated with neither common nor internal carotid IMT. We confirmed that the -629A, Taq1B B2, and -2505A alleles are significantly associated with lower CETP concentration (20.8%, 25.0%, and 23.7%, respectively; p<0.001) and activity (14.8%, 19.8%, and 18.4%, respectively; p<0.001) and higher HDL-C concentration (9.7%, 11.5%, and 10.4%, respectively; p<0.01). However, we did not find any associations between these non-coding polymorphisms and subclinical CVD.

Inconsistencies in the genetic prediction of HDL cholesterol versus atherosclerosis

PURPOSE OF REVIEW

High-density lipoprotein (HDL) is generally perceived as having a protective role with respect to cardiovascular disease. The metabolism of HDL is mediated through a complex network of apoproteins, enzymes and transfer proteins. Genetic variants within this network can increase plasma HDL, but not with uniformly beneficial clinical outcomes. The purpose of this review is to explore and propose mechanisms for these discrepant observations.

RECENT FINDINGS

Recent developments in this area include new observations of genetic variants that paradoxically increase both HDL and cardiovascular risk. Also discussed are newly observed, function-altering modifications of the HDL particle. Proposed explanations include the segregation of the genetic variants associated with the respective endpoints of plasma HDL and cardiovascular risk. Functionally impaired but quantitatively robust plasma HDL and the emerging understanding of proinflammatory HDL also may contribute to our understanding of discordant observations.

SUMMARY

Enhanced understanding of these relationships may allow a more accurate assessment of clinical risk based on plasma HDL and help explain why HDL may, in some circumstances, be an inappropriate therapeutic target.

Cholesteryl ester transfer protein gene polymorphisms are associated with coronary artery disease in Corsican population (France)

The aim of the present study was to investigate the association between coronary artery disease (CAD) and Cholesterol Ester Transfer Protein (CETP) (gaaa)n polymorphisms of the CETP gene in Central Corsica island (France). The study group was composed by 300 unrelated Corsican patients with angiographically documented CAD and 300 unrelated healthy blood donors. Significant differences were observed in the distribution of CETP (gaaa)n alleles between the groups under study (p=0.03; chi(2): 16.8, df: 8). The occurrence of a long allele (408 bp) was higher in cases (12%) than in control group (2%), showing a 6.75-fold increased risk for CAD in Corsica patients (p=0.0055; OR=6.750; 95% CIs=1.47-31.00). The correlation of this polymorphism with the lipid profile (cholesterol, low density lipoprotein-cholesterol, high density lipoprotein-cholesterol and triglycerides) in the patients group was determined. There was a significant association of the long alleles of CETP (gaaa)n with HDL-C levels. In the patient and in the control groups the LL genotypes had lower HDL-C compared with the SS and SL genotypes (p<0.0001). In summary our results suggest that the genetic variation at the CETP gene may play an important role in determining CAD in Corsican population.

Genetic determinants of HDL: monogenic disorders and contributions to variation

PURPOSE OF REVIEW

This review focuses on recent progress towards the characterization of genetic variations that contribute to interindividual variation in plasma high-density lipoprotein cholesterol levels in the general population.

RECENT FINDINGS

Many of the genes that harbor rare mutations leading to extreme high-density lipoprotein cholesterol levels contain common variation that influences plasma high-density lipoprotein cholesterol in several study populations. Candidate gene association studies provide evidence that some of these variations have an effect on high-density lipoprotein cholesterol, dependent on epistatic interactions or environmental context. Both rare and common variations contribute to interindividual high-density lipoprotein cholesterol variation. Recent comparisons of candidate gene sequences between individuals in the tails of the high-density lipoprotein cholesterol distributions (the upper or lower 1-5%) of several study populations indicate that as many as 20% of individuals with low high-density lipoprotein cholesterol harbor a rare mutation in an investigated gene. For example, the ABCA1 gene region harbors rare mutations and common variants that contribute to interindividual high-density lipoprotein cholesterol variation in the general population.

SUMMARY

The genetic control of high-density lipoprotein cholesterol level is complex. Maximizing the utility of genetic knowledge for predicting an individual's high-density lipoprotein cholesterol level or response to intervention will require a better understanding of the action of combinations of genetic variants and environmental exposures.

Cholesteryl ester-transfer protein (CETP) polymorphism and the association of acute coronary syndromes by obesity status in Greek subjects: the CARDIO2000-GENE study

OBJECTIVE

Cholesterol ester transfer protein (CETP) regulates plasma lipid distribution. The present study aimed to investigate whether the CETP gene (Taq1B) polymorphism predisposes to Acute Coronary Syndromes (ACS) depending on obesity status.

METHODS

We studied demographic, lifestyle and clinical information in 237 hospitalized patients (185 males) with a first event of an ACS and 237 controls matched by age and sex. CETP Taq1B genotyping was performed by PCR-RFLP analysis.

RESULTS

Overall, the CETP genotype frequencies were, in patients: 14% (n = 33), 35% (n = 83) and 51% (n = 121) and in controls: 17% (n = 39), 33% (n = 78) and 50% (n = 120) for B2B2, B1B1 and B1B2 respectively (p = 0.72). A significant interaction (p for interaction <0.001) was observed between obesity status and CETP concerning the likelihood of having ACS. Therefore, we stratified our analysis by obesity status and observed that B2B2 was associated with a 0.27 times lower likelihood of having ACS among normal-weight people (OR = 0.27, p = 0.02). No significant relationships were observed among overweight or obese participants.

CONCLUSIONS

These findings provide evidence of a protective effect of the B2B2 genotype of the CETP Taq1B polymorphism on the likelihood of having a first event of ACS in normal-weight persons.

Cholesteryl ester transfer protein gene haplotypes, plasma high-density lipoprotein levels and the risk of coronary heart disease

High-density lipoprotein cholesterol (HDL-C) is a known inverse predictor of coronary heart disease (CHD) and is thus a potential therapeutic target. Cholesteryl ester transfer protein (CETP) is a key protein in HDL-C metabolism such that elevated CETP activity is associated with lower HDL-C. Currently available HDL-C raising drugs are relatively ineffective and evidence suggesting the role of CETP in HDL-C levels has promoted the development of CETP inhibitors as potential therapeutic agents for CHD. We investigated three SNPs in the CETP gene in two cross-sectional community-based populations (n = 1,574 and 1,109) and a population of 556 CHD patients to determine if reduced CETP activity due to genetic variations in the CETP gene would increase HDL-C levels and reduce the risk of CHD. CETP genotypes and haplotypes were tested for association with lipid levels, CETP activity and risk of CHD. Multivariate analysis showed the common AAB2 haplotype defined by the G-2708A, C-629A and TaqIB polymorphisms, was consistently associated with reduced CETP activity and increased HDL-C levels. A mean increase in HDL-C levels of 0.16-0.24 mmol/l was observed in individuals with two copies of the AAB2 haplotype relative to non AAB2 carriers across all three populations (P < 0.001). A case-control study of males indicated no association between single SNPs or haplotypes and the risk of CHD. These results suggest that raising HDL-C via CETP inhibition may not alter risk of CHD. Randomized control trials are needed to determine whether CETP inhibition will in reality reduce risk of CHD by raising HDL-C.

CETP (cholesteryl ester transfer protein) promoter −1337 C>T polymorphism protects against coronary atherosclerosis in Japanese patients with heterozygous familial hypercholesterolaemia

CETP (cholesteryl ester transfer protein) and HL (hepatic lipase) play a role in the metabolism of plasma lipoproteins, but the effects of CETP and LIPC (gene encoding HL) genotypes on coronary atherosclerosis may be dependent on LDL (low-density lipoprotein)-receptor activity. Recently, the −1337 C>T polymorphism in the CETP gene has been reported in REGRESS (Regression Growth Evaluation Statin Study) to be a major determinant of promoter activity and plasma CETP concentration. In the present study, we have investigated the effects of the CETP promoter −1337 C>T and LIPC promoter −514 C>T polymorphisms on serum lipid profiles and risk of coronary atherosclerosis in 206 patients (154 males) with heterozygous FH (familial hypercholesterolaemia). To evaluate coronary atherosclerosis, we used CSI (coronary stenosis index) calculated from coronary angiograms. The CETP −1337 T allele was less frequent in subjects with a CSI ≥14 (mean value) in the group with coronary artery disease (P=0.04, as determined by χ2 test). ANOVA revealed that HDL-C (high-density lipoprotein-cholesterol) and triacylglycerol (triglyceride) levels were not significantly higher in the presence of the CETP promoter −1337 T allele. Combined with LIPC promoter polymorphisms, HDL-C levels were highest and CSI were lowest with CETP −1337 CT+TT and LIPC −514 CC genotypes, but a significant interaction was not shown. A multiple logistic regression analysis revealed that, in patients with coronary atherosclerosis, the CETP− 1337 CC genotype was a significant genetic risk factor in FH (odds ratio=2.022; P=0.0256). These results indicate that the CETP promoter −1337C>T polymorphism is associated with the progression of coronary atherosclerosis in Japanese patients with FH, independent of HDL-C and triacylglycerol levels.

Novel variants in human and monkey CETP

Variation in CETP has been shown to play an important role in HDL-C levels and cardiovascular disease. To better characterize this variation, the promoter and exonic DNA for CETP was resequenced in 189 individuals with extreme HDL-C or age. Two novel amino acid variants were found in humans (V-12D and Y361C) and an additional variant (R137W) not previously studied in vitro were expressed. D-12 was not secreted and had no detectable activity in cells. C361 and W137 retained near normal amounts of cholesteryl ester transfer activity when purified but were less well secreted than wild type. Torcetrapib, a CETP inhibitor in clinical development with atorvastatin, was found to have a uniform effect on inhibition of wild type CETP versus W137 or C361. In addition, the level of variation in other species was assessed by resequencing DNA from nine cynomolgus monkeys. Numerous intronic and silent SNPs were found as well as two variable amino acids. The amino acid altering SNPs were genotyped in 29 monkeys and not found to be significantly associated with HDL-C levels. Three SNPs found in monkeys were identical to three found in humans with these SNPs all occurring at CpG sites.

An interaction between the TaqIB polymorphism of cholesterol ester transfer protein and smoking is associated with changes in plasma high-density lipoprotein cholesterol levels in Turks

Low levels of high-density lipoprotein cholesterol (HDL-C) are an independent risk factor for atherosclerosis. We investigated the effects of the TaqIB polymorphism of cholesterol ester transfer protein (CETP) on CETP activity and plasma HDL-C levels in random nondiabetic and self-reported diabetic subjects in a population with very low HDL-C levels. The rare B2B2 genotype was associated with significantly higher HDL-C levels and lower CETP activity in random subjects and with higher HDL-C in diabetic subjects. After stratification of random subjects by smoking status, the common B1B1 genotype was associated with lower HDL-C levels than the B2B2 genotype. Although smoking was associated with lower HDL-C, especially in men, HDL-C levels between smokers and nonsmokers were not different in subjects with the B1B2 or B2B2 genotypes. However, smoking (20+ cigarettes/day) was associated with a marked reduction in HDL-C in the B1B1 subjects. The B1B1/smoking interaction was not reflected in a difference in CETP activity. High triglycerides and elevated body mass index (BMI) lower HDL-C. The B2B2 genotype was associated with the highest HDL-C levels, and these levels were significantly lower in the hypertriglyceridemic subjects (>or=50th percentile). The lowest HDL-C levels were seen in hypertriglyceridemic subjects with the B1B1 genotype. Although BMI (>or=50th vs<50th percentile) did not affect HDL-C in B2B2 subjects, a high BMI was associated with markedly lower HDL-C in B1B1 subjects. Thus, HDL-C levels in Turks may be modulated by an interaction between the CETP TaqIB polymorphism and smoking, as well as an interaction with hypertriglyceridemia and BMI.

Cholesteryl ester transfer protein TaqI B and lipoprotein lipase Ser447Ter gene polymorphisms are not associated with ischaemic stroke in Greek patients

Cholesteryl ester transfer protein (CETP) and lipoprotein lipase (LPL) are both key players in plasma lipoprotein homeostasis and, as such, genetically induced alterations in their respective activities may affect susceptibility to cerebrovascular diseases. In this study, we examined the distribution of two common polymorphisms, namely CETP TaqI B and LPL Ser447Ter in a cohort of Greek clinically diagnosed late-onset ischaemic stroke patients (n = 98) and an ethnicity-, age- and sex-matched control group with no manifestations of vascular disease (n = 100). Our study revealed no statistically significant differences with respect to the distribution of either polymorphism, examined separately or in combination, between the two groups.

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.

HMG-CoA reductase inhibitor pharmacogenomics: overview and implications for practice

HMG-CoA reductase inhibitors (statins) are widely prescribed and recommended as first-line therapy for most patients with hypercholesterolemia or established coronary heart disease. However, there is interpatient variability in lipid-lowering response to statins that is not explained by initial cholesterol levels and inadequate dosing alone. Genetic polymorphisms may contribute. This review discusses the potential contribution of polymorphisms in genes encoding proteins involved in drug metabolism and transport, cholesterol biosynthesis, lipid metabolism and others to lipid responses to statins.

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.

Highly polymorphic repeat region in the CETP promoter induces unusual DNA structure

Genetic variation in the human cholesteryl ester transfer protein (CETP) promoter is associated with HDL cholesterol levels and cardiovascular disease with much of the genetic variation in CETP attributed to the promoter region. In this region, there are several single nucleotide polymorphisms as well as a variable length tandem repeat located 1946 base pairs upstream of the CETP transcription start that is highly polymorphic with respect to both length and sequence. There are more than 10 different long alleles and these vary in their repeat structure. We find that the short allele of this repeat is associated with high HDL cholesterol levels in vivo (P<0.0001). In males, this association is independent of the nearby -629 polymorphism. In addition, the variable length GAAA repeat can stimulate an adjacent GGGGA repeat to form a structure that hinders DNA amplification and sequencing. This structure also has an effect in vivo as shown by orientation effects and cloning efficiency in Escherichia coli.

An association study of the cholesteryl ester transfer protein TaqI B polymorphism with late onset Alzheimer's disease

Cholesteryl ester transfer protein (CETP) is reportedly able to affect the amount of cholesterol available for deposition and/or removal from peripheral tissues, in its capacity to mediate the transfer of cholesterol from high density lipoprotein (HDL) to very low density lipoprotein, in exchange for triacylglycerols from the latter. The TaqI B polymorphism of the human CETP gene has been associated with decreased CETP mass and an increase in HDL-cholesterol. While many studies have addressed the atherogenic or anti-atherogenic potential of this polymorphism, little is known about its effect on neurodegeneration, despite the fact that CETP is expressed in the brain and the disturbance of cholesterol homeostasis appears to be an important factor in the pathogenesis of Alzheimer's disease (AD). In this report, we have compared the distribution of the TaqI B polymorphism in an independent population of 102 clinically diagnosed late onset AD patients and a spousal control group of 97 individuals. We have also examined the possible interaction between this polymorphism and two other polymorphisms suspected of affecting cholesterol flux, namely apolipoprotein E APOE epsilon4, and lipoprotein lipase LPLS447X. No statistically significant differences have emerged with respect to either genotype or allele frequencies between the AD and control populations. CETP TaqI B did not interact significantly with either APOE epsilon4 or LPLS447X, in this study.

Haplotypes of the cholesteryl ester transfer protein gene predict lipid-modifying response to statin therapy

Cholesteryl ester transfer protein (CETP) plays a central role in high-density lipoprotein (HDL) metabolism. Single nucleotide polymorphisms (SNPs) and haplotypes in the CETP gene were determined in 98 patients with untreated dyslipidemias and analyzed for associations with plasma CETP and plasma lipids before and during statin treatment. Individual CETP SNPs and haplotypes were both significantly associated with CETP enzyme mass and activity. However, only certain CETP haplotypes, but not individual SNPs, significantly predicted the magnitude of change in HDL cholesterol (HDL-C) and triglycerides. After adjusting for covariates and multiple testing, the TTCAAA haplotype showed a gene-dose effect in predicting the HDL-C increase (P=0.03), while the TTCAAAGGG and AAAGGG haplotypes predicted a decrease in triglycerides (P=0.04 both). This is the first study to demonstrate that SNP haplotypes derived from allelic SNP combinations in the CETP gene were more informative than single SNPs in predicting the response to lipid-modifying therapy with statins.