The association of HDL cholesterol concentration with the −629C>A CETP promoter polymorphism is not fully explained by its relationship with plasma cholesteryl ester transfer

Exome chip-driven association study of lipidemia in >14,000 Koreans and evaluation of genetic effect on identified variants between different ethnic groups

Lipid levels in blood are widely used to diagnose and monitor chronic diseases. It is essential to identify the genetic traits involved in lipid metabolism for understanding chronic diseases. However, the influence of genetic traits varies depending on race, sex, age, and ethnicity. Therefore, research focusing on populations of individual countries is required, and the results can be used as a basis for comparison of results of other studies at the cross-racial and cross-country levels. In the present study, we selected lipid-related variants and evaluated their effects on lipid-related diseases in more than 14,000 subjects of three cohorts using the Illumina Human Exome Beadchip. A genome-wide association study was conducted using EPACTs after adjusting for age, sex, and recruitment area. A genome-wide significance cutoff was defined as p < 5E-08 in all the three cohorts. Sixteen variants represented the lipid traits and were classified as vulnerable to borderline hypertriglyceridemia, hyper-LDL-cholesterolemia, or hypo-HDL-cholesterolemia. Moreover, we compared the genetic effects of the 16 variants between ethnic groups and identified the missense variants in apolipoprotein A-V, cholesterol ester transfer protein, and apolipoprotein E as Asian-specific. Our study provides candidate genes as markers for chronic diseases through the evaluation of genetic effects.

Common variation in cholesteryl ester transfer protein: relationship of first major adverse cardiovascular events with the apolipoprotein B/apolipoprotein A-I ratio and the total cholesterol/high-density lipoprotein cholesterol ratio

BACKGROUND

The preference of the apolipoprotein (apo) B/apoA-I ratio over the total cholesterol/HDL cholesterol (TC/HDL-C) ratio in cardiovascular risk prediction is disputed. Cholesteryl ester transfer protein (CETP) is instrumental in lipoprotein remodelling and affects the cholesterol content in pro- and antiatherogenic lipoproteins relative to their major apolipoproteins. We tested the influence of common CETP variations on the strength of associations of a first major adverse cardiovascular event (MACE) with the apoB/apoA-I ratio compared with the TC/HDL-C ratio.

METHODS

A prospective case-cohort study was performed (PREVEND cohort; no previous cardiovascular disease and no use of lipid-lowering drugs initially). Fasting serum TC/HDL-C, apoB/apoA-I, triglycerides, and common CETP variations (TaqIB [rs708272] and -629C>A [rs1800775] polymorphisms) were measured at baseline. The composite end point was incident MACE.

RESULTS

A total of 532 of 6780 subjects experienced a first MACE during 10.8 years follow-up. The age- and sex-adjusted hazard ratio was 1.31 (95 % confidence interval 1.23-1.41) for the apoB/apoA-I ratio and 1.22 (95% confidence interval 1.26-1.39) for the TC/HDL-C ratio (both P < .001). These relationships were essentially similar within each TaqIB and -629C>A CETP genotype group. No interactions of the apoB/apoA-I ratio and the TC/HDL-C ratio with the TaqIB and the -629C>A CETP variations on incident MACE were observed (P > .20 for all).

CONCLUSION

The relationship of first MACE with the TC/HDL-C and the apoB/apoA-I ratio is not to an important extent dependent on common CETP variations. CETP variations are unlikely to affect the strength of the relationship of first MACE with the apoB/apoA-I ratio compared with the TC/HDL-C ratio.

The relationship of ACE and CETP gene polymorphisms with cardiovascular disease in a cohort of Asian Indian patients with and those without type 2 diabetes

INTRODUCTION

Hypertension and dyslipidemia have been associated with cardiovascular disease (CVD). We investigated the association of candidate gene polymorphisms in angiotensin-converting enzyme (ACE) and cholesterol ester transfer protein (CETP) genes in a cohort of Asian Indian patients with and those without type 2 diabetes.

METHODS

PCR-based genotyping of insertion/deletion (I/D) polymorphism of ACE (rs4646994) and -629C>A of CETP (rs1800775) was carried out in 520 individuals, of whom 160 had CVD+type 2 diabetes mellitus (T2DM), 90 were CVD patients without T2DM, 150 had T2DM with no cardiovascular complications, and 120 were age- and sex-matched healthy controls.

RESULTS

With respect to the ACE gene I/D polymorphism, there was a higher percentage of D/D genotype in CVD+T2DM patients, but it was not statistically significant, while the CETP -629A allele was significantly associated with CVD+T2DM patients (P=.000007; odds ratio=0.46; 95% confidence interval=0.32-0.65) as compared with the normal controls and not with CVD alone. Additive interactions between the AA+I/I genotypes, AC+I/D genotypes, and AC+D/D were identified between the patients and the controls with P values of .0052, .0009, and .0078, respectively.

CONCLUSIONS

Our study suggests that candidate gene polymorphism -629C>A of CETP may serve as a susceptibility biomarker for CVD in T2DM patients. Analyzing the combined effect of both ACE and CETP genotypes would enhance the sensitivity and specificity of CVD risk estimation in the T2DM patients in our population.

Association of CETP polymorphisms with the risk of vascular dementia and white matter lesions

Cholesteryl ester transfer protein (CETP), a component of the high density lipoprotein (HDL), plays a central role in reverse cholesterol transport. We investigated the association of two putative functional CETP polymorphisms (C-629A and I405V) with the risk of vascular dementia (VD) and tested if this association is influenced by the presence of APOE4 allele. Our study included 163 VD patients (mean age: 74.25 +/- 7.9 years) and 452 cognitively healthy probands (mean age: 70.81 +/- 7.9 years). As a biological correlate, the association of CETP gene variants with white matter lesion (WML) load was investigated. Neither the C-629A (P = 0.169) nor the I405V (P = 0.840) polymorphism was associated with VD risk in the whole sample. However, in non-carriers of the APOE4 allele, homozygote carriers of the CETP C-629A A allele presented with an increased risk of VD (P = 0.01). Whereas in APOE4 carriers, no association of CETP polymorphisms with VD risk was detected. In addition, carriers of the CETP C-629A AA genotype presented with decreased WML load in the frontal brain (P = 0.009). Our results suggest that CETP gene polymorphisms might influence WML load and the risk of VD, the latter in non-carriers of the APOE4 allele.

Glucocorticoid replacement is associated with hypertriglyceridaemia, elevated glucose and higher non-HDL cholesterol and may diminish the association of HDL cholesterol with the -629C>A CETP promoter polymorphism in GH-receiving hypopituitary patients

OBJECTIVES

The effect of glucocorticoid substitution on the prevalence of metabolic syndrome components (NCEP ATP III criteria) and serum lipid levels was determined in GH-replaced hypopituitary patients. As glucocorticoid replacement is associated with a pronounced decrease in plasma cholesteryl ester transfer protein (CETP) activity, we also tested associations of HDL cholesterol with the -629C>A CETP promoter polymorphism in subjects with and without ACTH deficiency.

DESIGN AND PATIENTS

In a university setting, we retrieved protocolized clinical and laboratory data from 165 adult hypopituitary patients, who had received GH for 1 year.

RESULTS

After adjustment for age, sex and smoking, non-HDL cholesterol (P = 0.05) and triglycerides (P = 0.004) were higher, but HDL cholesterol was not decreased in 117 glucocorticoid (mainly cortisone acetate in two divided doses) receiving subjects compared to 48 ACTH-sufficient subjects. The prevalence of elevated plasma glucose and/or diabetes (P = 0.04) and hypertriglyceridaemia (P = 0.005), but not of other metabolic syndrome components, was higher in glucocorticoid-replaced subjects. HDL cholesterol was higher in -629 A allele carriers compared to -629CC homozygotes in ACTH-sufficient subjects (P = 0.04), but not in glucocorticoid-treated subjects (P = 0.13). Multiple linear regression analysis demonstrated that only in ACTH-sufficient subjects, HDL cholesterol was independently related to this CETP gene variation (P = 0.03).

CONCLUSIONS

In GH- and glucocorticoid-replaced hypopituitary patients, serum non-HDL cholesterol and triglycerides are higher and the prevalence of hyperglycaemia is increased, but HDL cholesterol is not decreased. Conventional glucocorticoid replacement appears to diminish the association of HDL cholesterol with a common CETP gene variation.

Common variation in the CETP gene and the implications for cardiovascular disease and its treatment: an updated analysis

Human plasma contains cholesteryl ester transfer protein (CETP) which, besides other functions, enables the transfer of cholesteryl esters in plasma from high-density lipoproteins (HDL) towards triglyceride-rich lipoproteins, thereby contributing to lower HDL cholesterol. Variations in the CETP gene, including the intronic TaqIB polymorphism (rs708272), are common in the population. Although HDL cholesterol is approximately 10% higher in TaqIB B2B2 than in B1B1 carriers, the association of this polymorphism with cardiovascular disease has not been unequivocally established. We present an updated pooled analysis concerning the association of cardiovascular disease with the TaqIB polymorphism, including only studies that predominantly comprise Caucasian subjects. The distribution of this CETP genotype was observed to be different in population-based studies (n = 10,526) compared with studies in populations selected by high cardiovascular risk (n = 10,947), with B2B2 carriers being less frequent among cases from high-risk populations compared with cases from population-based studies (p = 0.0009 for the difference in genotype distribution). In population-based studies, the odds ratio (OR) for cardiovascular disease was found to be 1.45 (95% CI: 1.07–1.95) in B2B2 compared with B1B1 carriers, contrasting the lower OR of 0.84 (95% CI: 0.74–0.96) in B2B2 versus B1B1 carriers from high-risk populations. Thus, it is possible that in the general population, the B2 allele is associated with higher cardiovascular risk, despite higher HDL cholesterol. Our analysis agrees with the contention that selection towards a lower frequency of B2B2 homozygotes may have occurred in selected populations, which would result in a apparently protective effect of the B2 allele when determined in high-risk populations. We also evaluated whether the TaqIB polymorphism would predict efficacy of lipid-lowering treatment with respect to plasma lipids and cardiovascular outcome, but the results of published studies were contradictory. Likewise, no definite conclusion can be made at present concerning the effect of this CETP polymorphism on the lipid response to diet intervention.