Contribution of the cholesteryl ester transfer protein gene TaqIB polymorphism to the reduced plasma HDL-cholesterol levels found in abdominal obese men with the features of the insulin resistance syndrome

Cholesterol Ester Transfer Protein Taq1B Polymorphism and Its Association with Cardiovascular Risk Factors in Patients Undergoing Angiography in Yazd, Eastern Iran: A Cross-Sectional Study

Background

Several studies assessed the relationship between the cholesterol ester transfer protein (CETP) Taq1B gene polymorphism (rs708272) with risk factors of cardiovascular diseases (CVDs). However, their findings were inconsistent. The present study investigated the relationship between CVD risk factors and the Taq1B variant in patients undergoing coronary angiography.

Methods

This cross-sectional study was conducted on 476 patients aged 30-76 years old of both sexes from 2020-2021, in Yazd (Iran). The Taq1B polymorphism genotypes were evaluated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) on DNA extracted from whole blood. Standard protocols were used to measure cardio-metabolic markers. To determine the association between CVDs risk factors and the rs708272 variant, binary logistic regression was used in crude and adjusted models.

Results

Taq1B polymorphism genotype frequencies were 10.7% for B1B1, 72.3% for B1B2, and 17% for B2B2. There was no significant association between abnormal levels of CVDs risk factors and different genotypes of the Taq1B variant, Gensini score (P=0.64), Syntax score (P=0.79), systolic blood pressure (P=0.55), diastolic blood pressure (P=0.58), and waist circumference (P=0.79). There was no significant association between genotypes of the rs708272 variant and any abnormal serum lipid levels. After adjusting for confounders, the results remained non-significant.

Conclusion

There was no significant association between CVDs risk factors and CETP rs708272 polymorphism. The relationship between CETP gene variants and CVD occurrences varied across groups, implying that more research in different regions is required.A preprint version of this manuscript is available at https://www.researchsquare.com/article/rs-2575215/v1 with doi: 10.21203/rs.3.rs-2575215/v1.

Abdominal Obesity, Excessive Adiposity, and the Taq1B CETP Variant Are Positively Associated with Serum Lipid Levels in Mexican Women

INTRODUCTION

Obesity is a prevalent multifactorial disease whose main complication is dyslipidemia. Serum lipid levels also depend on genetic factors including the Taq1B variant of the CETP gene, which is suggested to be influenced by environmental factors and adiposity. Therefore, this study aimed to determine the effect of the Taq1B CETP variant on serum lipid levels associated with anthropometrical variables.

METHODS

165 women from western Mexico were enrolled in this cross-sectional study. Weight and body fat were measured by bioimpedance and waist circumference with a measuring tape. Serum lipid levels were determined by dry chemistry. The Taq1B CETP variant was analyzed by allelic discrimination.

RESULTS

Women with abdominal obesity and the B1B2/B2B2 genotype had significantly higher total cholesterol levels (195.17 [185.95-204.39] vs. 183 mg/dL [169.83-196.16], p = 0.007) and low density lipoprotein (118.84 [110.65-127.03] vs. 113.84 mg/dL [102.37-125.31], p = 0.037) than carriers of the B1B1 genotype. Likewise, subjects with excessive adiposity and the B1B2/B2B2 genotype showed significantly higher total cholesterol levels (195.05 [186.04-204.06] vs. 182.40 mg/dL [169.03-195.76], p = 0.003) than those with the B1B1 genotype.

CONCLUSION

Women with abdominal obesity or excessive adiposity, who are also carriers of the B1B2/B2B2 genotype, have higher serum lipid levels than women with the B1B1 genotype.

Quantile-Dependent Expressivity and Gene-Lifestyle Interactions Involving High-Density Lipoprotein Cholesterol

BACKGROUND

The phenotypic expression of a high-density lipoprotein (HDL) genetic risk score has been shown to depend upon whether the phenotype (HDL-cholesterol) is high or low relative to its distribution in the population (quantile-dependent expressivity). This may be due to the effects of genetic mutations on HDL-metabolism being concentration dependent.

METHOD

The purpose of this article is to assess whether some previously reported HDL gene-lifestyle interactions could potentially be attributable to quantile-dependent expressivity.

SUMMARY

Seventy-three published examples of HDL gene-lifestyle interactions were interpreted from the perspective of quantile-dependent expressivity. These included interactive effects of diet, alcohol, physical activity, adiposity, and smoking with genetic variants associated with the ABCA1, ADH3, ANGPTL4, APOA1, APOA4, APOA5, APOC3, APOE, CETP, CLASP1, CYP7A1, GALNT2, LDLR, LHX1, LIPC, LIPG, LPL, MVK-MMAB, PLTP, PON1, PPARα, SIRT1, SNTA1,and UCP1genes. The selected examples showed larger genetic effect sizes for lifestyle conditions associated with higher vis-à-vis lower average HDL-cholesterol concentrations. This suggests these reported interactions could be the result of selecting subjects for conditions that differentiate high from low HDL-cholesterol (e.g., lean vs. overweight, active vs. sedentary, high-fat vs. high-carbohydrate diets, alcohol drinkers vs. abstainers, nonsmokers vs. smokers) producing larger versus smaller genetic effect sizes. Key Message: Quantile-dependent expressivity provides a potential explanation for some reported gene-lifestyle interactions for HDL-cholesterol. Although overall genetic heritability appears to be quantile specific, this may vary by genetic variant and environmental exposure.

Physical inactivity and excessive sucrose consumption are associated with higher serum lipids in subjects with Taq1B CETP polymorphism

BACKGROUND

Dyslipidaemias result from the interaction between genetic and environmental factors, including diet disequilibrium and physical inactivity. Among the genetic factors associated with serum lipids, the Taq1B CETP polymorphism has been investigated. The B1 allele has been considered as a risk factor for dyslipidaemia because of its association with greater CETP levels and higher serum triglycerides. The present study aimed to determine the role of the Taq1B polymorphism with lipid and anthropometric variables and its interaction with diet and physical activity.

METHODS

In total, 215 subjects were enrolled in this cross-sectional study. Diet intake was evaluated using a 3-day food consumption record and physical activity was determined in accordance with World Health Organization recommendations. The Taq1B CETP polymorphism was determined by allelic discrimination.

RESULTS

Subjects with the B1B2/B2B2 genotype, who had a sucrose consumption ≥5% of the total kcal day^-1 , had higher levels of total cholesterol (TC) [165.55 (142.21-188.89) mg dL^-1 versus 200.19 (184.79-215.60) mg dL^-1 ; P for interaction = 0.034] and low-density lipoprotein [99.29 (75.52-123.05) mg dL^-1 versus 128.64 (113.59-143.69) mg dL^-1 ; P for interaction = 0.037] than subjects with the B1B1 genotype. Subjects who did not perform physical activity and had the B1B2/B2B2 genotype showed significantly higher levels of TC [177.48 (161.36-193.60) mg dL^-1 versus 194.49 (185.43-203.56) mg mL^-1 ; P for interaction = 0.033] than subjects with the B1B1 genotype.

CONCLUSIONS

We provide evidence that subjects with inadequate environmental factors carriers of the polymorphic genotype had higher serum lipid levels than subjects with the B1B1 genotype.

CETP genotype and concentrations of HDL and lipoprotein subclasses in African-American men

Aim: To assess the association between the CETP Taq1B and I405V polymorphisms with levels of lipoprotein subclasses in African-American (AA) men with and without Type 2 diabetes (T2DM). Patients & methods: AA men, over 30 years of age, with (n = 54) or without T2DM (n = 50), and not receiving lipid-lowering agents, underwent advanced lipid analysis and genotyping. Results & conclusion: In the total patient population Taq1B B2-allele carriers had significantly higher levels of large HDL subclasses (HDL-2b [p = 0.017] and HDL-L [p = 0.019]), lower levels of small-HDL subclasses (HDL-3a [p = 0.004] and HDL-3b [p = 0.031]), and lower levels of LDL subclasses (LDL-IVa [p = 0.012] and LDL-IIIb [p = 0.009]). The only significant genotype-diabetes interaction occurred with the HDL-2a subclass (p = 0.015). No statistically significant associations were seen with I405V genotype. Our observations of lower levels of small-HDL and higher levels of large-HDL suggest that a potentially important HDL subclass-CETP relationship exists.

Impact of variants in CETP and apo AI genes on serum HDL cholesterol levels in men and women from the Polish population

INTRODUCTION

Polymorphisms in the cholesterol ester transfer protein (CETP) gene and apolipoprotein AI (apo AI) gene are identified as the most common genetic factors influencing high-density lipoprotein cholesterol (HDL cholesterol) levels. Low HDL cholesterol is an important risk factor for cardiovascular disease. We investigated the effect of the TaqIB polymorphism of the CETP gene and the 75G/A polymorphism of the apo AI gene on the HDL cholesterol concentration in a sample of Polish adults.

MATERIAL AND METHODS

A total of 621 subjects, 414 women and 207 men, were included in this study. Lipid levels were measured using standard protocols, and apolipoprotein AI was determined by immunoturbidimetric assay. CETP and apo AI genotyping was performed using a restriction fragment length polymorphism based method.

RESULTS

Significantly lower HDL cholesterol concentrations were found in B1B1 homozygotes than in carriers of the B2 allele of the TaqIB polymorphism in the CETP gene among both men and women. In GG homozygotes of the 75G/A polymorphism in the apo AI gene lower HDL cholesterol levels were observed, but the difference did not reach statistical significance. A statistically significant association of low HDL cholesterol (< 25^th percentile) with CETP genotypes was found in women (p < 0.0001) and in men (p = 0.0368).

CONCLUSIONS

These data demonstrate a significant impact of the TaqIB polymorphism in the CETP gene on HDL cholesterol levels in the studied Polish population, while the effect of the 75G/A polymorphism in the apo AI gene appears not to be significant.

Association of the CETP Taq1B and LIPG Thr111Ile Polymorphisms with Glycated Hemoglobin and Blood Lipids in Newly Diagnosed Hyperlipidemic Patients

OBJECTIVE

To examine the association of 2 common polymorphisms in high-density lipoprotein (HDL)-related genes, namely, cholesterol ester transfer protein CETP Taq1B (rs708272) and endothelial lipase LIPG Thr111Ile (rs2000813), with glycated hemoglobin (A1C), blood lipid levels and the risk for type 2 diabetes in a group of hyperlipidemic patients from northern Greece.

METHODS

We categorized 175 patients with hyperlipidemia into 2 subgroups according to the presence or absence of type 2 diabetes, defined as a recent diagnosis, A1C >6.5% and/or fasting glucose >126 mg/dL. Genotypes for the 2 polymorphisms studied were determined by polymerase chain reaction-restriction fragment length polymorphism. Both polymorphisms were analyzed by multivariate and univariate analyses of baseline A1C levels and plasma lipids. The genotype and allele frequencies of the 2 subgroups were compared.

RESULTS

The CETP Taq1B polymorphism was associated with HDL-cholesterol (HDL-C) and A1C levels, but this association was affected by type 2 diabetes; the association with A1C levels was significant only in type 2 diabetes (p=0.005), whereas the association with HDL-C occurred only in the subgroup without type 2 diabetes (p<0.001). LIPG Thr111Ile did not affect plasma HDL-C or A1C levels independently but appeared to modulate their association with CETP Taq1B, and LIPG 111IleIle homozygotes tended to be present at a higher frequency in the hyperlipidemic patients with type 2 diabetes compared to the hyperlipidemic patients without type 2 diabetes (p=0.056).

CONCLUSIONS

In hyperlipidemic patients, apart from its known association with HDL-C, CETP Taq1B is also associated with A1C levels, and both associations are modified by type 2 diabetes and LIPG Thr111Ile.

The roles of genetic polymorphisms and human immunodeficiency virus infection in lipid metabolism. Biomed Res Int. 2013;2013:836790. [PMID: 24319689 PMCID: PMC3844249 DOI: 10.1155/2013/836790]

Dyslipidemia has been frequently observed among individuals infected with human immunodeficiency virus type 1 (HIV-1), and factors related to HIV-1, the host, and antiretroviral therapy (ART) are involved in this phenomenon. This study reviews the roles of genetic polymorphisms, HIV-1 infection, and highly active antiretroviral therapy (HAART) in lipid metabolism. Lipid abnormalities can vary according to the HAART regimen, such as those with protease inhibitors (PIs). However, genetic factors may also be involved in dyslipidemia because not all patients receiving the same HAART regimen and with comparable demographic, virological, and immunological characteristics develop variations in the lipid profile. Polymorphisms in a large number of genes are involved in the synthesis of structural proteins, and enzymes related to lipid metabolism account for variations in the lipid profile of each individual. As some genetic polymorphisms may cause dyslipidemia, these allele variants should be investigated in HIV-1-infected patients to identify individuals with an increased risk of developing dyslipidemia during treatment with HAART, particularly during therapy with PIs. This knowledge may guide individualized treatment decisions and lead to the development of new therapeutic targets for the treatment of dyslipidemia in these patients.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

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.

Effects of V279F in the Lp-PLA(2) gene on markers of oxidative stress and inflammation in Koreans

BACKGROUND

A single nucleotide polymorphism (SNP), V279F, in the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) gene is known to influence enzyme activity. It is unclear whether Lp-PLA(2) exerts pro- or antiatherogenic effects in humans. We investigated the interplay between V279F, Lp-PLA(2) activity, oxidative stress and inflammation.

METHODS

We genotyped 2914 healthy Koreans (43-79years) for the Lp-PLA(2) V279F and measured anthropometric parameters, lipid profile, fatty acid composition, lipid peroxides, inflammatory markers and Lp-PLA(2) levels.

RESULTS

Lp-PLA(2) activity was 24% lower in V/F subjects (n=641) than in those with the V/V genotype (n=2227). Enzyme activity was undetectable in F/F subjects. Lp-PLA(2) activity was positively correlated with LDL-cholesterol (r=0.134, P<0.001), ox-LDL (r=0.064, P<0.01), 8-epi-PGF(2alpha) (r=0.198, P<0.001), free fatty acid (r=0.082, P<0.001), and fibrinogen (r=0.112, P<0.01) levels. Additionally, ox-LDL, 8-epi-PGF(2alpha), free fatty acid, and fibrinogen levels were positively correlated with hs-CRP. V279F was associated with LDL-cholesterol and arachidonic acid (AA) in serum phospholipid. F/F subjects had lower LDL-cholesterol than V/V subjects (V/V: 120.9+/-0.69, V/F: 119.4+/-1.26, F/F: 109.2+/-4.84mg/dl, P=0.025). A significant association between the F/F genotype and increasing AA in serum phospholipids was found in subjects with high LDL-cholesterol (> or =130mg/dl) (P=0.003) but not in those with low LDL-cholesterol (<130mg/dl). F/F subjects in the high LDL-cholesterol group had CRP concentrations about three times higher than those with V/V or V/F genotypes (V/V: 1.25+/-0.09, V/F: 0.97+/-0.12, F/F: 3.20+/-0.88mg/dl, P<0.001).

CONCLUSIONS

The recessive effects of Lp-PLA(2) V279F on LDL-cholesterol and significant correlations between Lp-PLA(2) activity and LDL-cholesterol, 8-epi-PGF(2alpha) and fibrinogen support a pro-oxidative or pro-atherogenic role for this enzyme. Paradoxically, the combination of the complete deficiency of Lp-PLA(2) activity and high LDL-cholesterol enhanced lipid peroxidation and inflammation.

Lack of association between the cholesteryl ester transfer protein gene--TaqIB polymorphism and coronary restenosis following percutaneous transluminal coronary angioplasty and stenting: a pilot study

BACKGROUND

The most widely studied variation at the cholesteryl ester transfer protein (CETP) gene locus is a silent base change called the Thermobius aquaticus IB (TaqIB) polymorphism. TaqIB has been shown to affect levels/activity of CETP, plasma levels of high-density lipoprotein cholesterol (HDL-C), and to contribute to the risk of developing atherosclerosis and coronary heart disease (CHD). Ongoing studies are investigating possible associations between CETP gene polymorphisms and the development of coronary restenosis following percutaneous transluminal coronary angioplasty (PTCA) and stenting.

METHODS AND RESULTS

The primary objective of the present study was to investigate the frequency of TaqIB-polymorphism, and a possible association with post-PTCA coronary restenosis, in 204 Greek patients who had undergone PTCA and stenting. As a secondary objective, the analysis was extended to explore possible interacting or additive effects by various CHD risk factors, and a deletion in the alpha(2B)-adrenergic receptor gene. The frequency of TaqIB was 54%, similar to the frequency of the polymorphism in a group of 35 healthy controls.

CONCLUSIONS

The results from this study do not indicate that the TaqIB variation at the CETP gene locus is a significant predictor for assessing the risk of developing coronary restenosis following PTCA and stenting. This result was not affected when considering any one of the additionally studied factors.

The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

Interactions between alcohol intake and the polymorphism of rs708272 on serum high-density lipoprotein cholesterol levels in the Guangxi Hei Yi Zhuang population

Both alcohol consumption and the polymorphism of the cholesteryl ester transfer protein (CETP) TaqIB gene (rs708272) influence plasma high-density lipoprotein cholesterol (HDL-C) levels. However, their interactions on serum HDL-C levels is not well known. The present study was undertaken to detect the interactions between alcohol consumption and the rs708272 polymorphism on serum lipid levels in the Guangxi Hei Yi Zhuang population. Genotyping of the rs708272 in 342 nondrinkers and 416 drinkers aged 15-70 years was performed by polymerase chain reaction and restriction fragment length polymorphism. Interactions between rs708272 genotype and alcohol consumption was assessed using a cross-product term between genotypes and the aforementioned factor. Statistical significance was evaluated with analysis of co-variance. The frequency of B1 allele was 65.8% in nondrinkers and 64.7% in drinkers (P>.05), respectively. The frequencies of B1B1, B1B2, and B2B2 genotypes were 45.0%, 41.5%, and 13.5% in nondrinkers, and 41.3%, 46.6%, and 12.0% in drinkers (P>.05), respectively. The levels of HDL-C and apolipoprotein (Apo) AI in nondrinkers were higher in B2B2 genotype than in B1B1 genotype (P<.05 for each), whereas triglyceride (TG) levels in drinkers were higher in B1B1 genotype than in B1B2 genotype (P<.05). The levels of TG, HDL-C, Apo AI in B1B1 genotype, and HDL-C and Apo AI in B1B2 genotype were higher in drinkers than in nondrinkers (P<.05-.01), whereas the levels of low-density lipoprotein cholesterol (LDL-C) and Apo B in B2B2 genotype, and the levels of LDL-C in B1B1 genotype were lower in drinkers than in nondrinkers (P<.05-.01). The levels of HDL-C were positively correlated with female sex and genotype in nondrinkers (P<.001 for each), and were positively associated with age and alcohol consumption in drinkers (P<.005 and<.01, respectively). This study suggests that the B1 carriers benefited more from alcohol consumption than the B2 carriers in increasing serum HDL-C and Apo AI levels, and lowering LDL-C levels.

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.

Cholesteryl ester transfer protein B1B1 genotype as a predictor of coronary artery disease in Taiwanese with type 2 diabetes mellitus

Diabetes is known to be a high-risk factor for coronary artery disease (CAD), and lipid abnormalities have been found to possibly contribute to CAD in diabetic patients. Cholesteryl ester transfer protein (CETP) gene TaqIB polymorphism is associated with lipid profile variability, and this polymorphism may be a risk factor for CAD in diabetic patients. To clarify the relationship between CETP TaqIB gene polymorphism and CAD, we enrolled in our study 365 Taiwanese with type 2 diabetes mellitus (101 with CAD and 264 without CAD). The genotype of the subjects for TaqIB polymorphism of CETP in intron 1 was analyzed by using polymerase chain reaction-restriction fragment length polymorphism. The CETP B1B1 genotype (18.8% vs 8.5%, P = .002) and B1 allele (42.1% vs 29.7%, P = .002) were significantly more frequent in diabetic patients with CAD than those without CAD. Logistic regression analysis revealed that the CETP B1B1 genotype was associated with CAD in patients with type 2 diabetes mellitus (odds ratio, 3.18; 95% confidence interval, 1.54-6.54; P = .002). Interestingly, in diabetic patients, serum creatinine levels higher than 1.4 mg/dL were also associated with increased risk for CAD (odds ratio, 2.09; 95% confidence interval, 1.12-3.91; P = .02). Our results suggest that the CETP B1B1 genotype is a strong genetic predictor of CAD in Taiwanese with type 2 diabetes mellitus.

Genetic epistasis in the VLDL catabolic pathway is associated with deleterious variations on triglyceridemia in obese subjects

BACKGROUND

Abdominal obesity and hypertriglyceridemia (the hypertriglyceridemic-waist phenotype) increase cardiovascular risk. The very low-density lipoprotein (VLDL) is a triglyceride (TG)-rich particle. Frequent variations in the genes coding for enzymes and proteins involved in the VLDL catabolism have already been documented. The epistatic effect of such variants on the risk profile associated with abdominal obesity remains to be elucidated.

OBJECTIVE

This study aims to assess the effect of combinations of frequent single-nucleotide polymorphisms (SNPs) in the VLDL catabolic pathway on the relation between abdominal obesity and fasting TG.

METHOD

Only gene variants in the lipoprotein lipase, apolipoprotein (apo) CIII, hepatic lipase and apo E genes known to be frequent in the general population (allele frequency>5%) were included in this study. The presence of selected SNPs was detected by polymerase chain reaction-restriction fragment length polymorphism in a sample of 640 non-diabetic French Canadians at high cardiovascular risk (405 obese, 235 non-obese).

RESULTS

Carrying more than two frequent gene variants involved in the VLDL catabolic pathway significantly increased the risk of hyperTG (odds ratio of TG>1.7 mmol/l=4.15; P=0.001). This effect was proportional to the number of SNPs and genes involved and was significantly amplified by the presence of abdominal obesity defined on the basis of waist circumference.

CONCLUSION

When combined with abdominal obesity, epistasis in the VLDL pathway has a deleterious effect on fasting TG and coronary artery disease risk profile according to the TG threshold (1.7 mmol/l) used in medical guidelines for the assessment of the metabolic syndrome and associated risk.

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.

Associations between HDL-cholesterol and polymorphisms in hepatic lipase and lipoprotein lipase genes are modified by dietary fat intake in African American and White adults

Polymorphisms in genes involved in HDL-cholesterol (HDL-C) metabolism influence plasma HDL-C concentrations. We examined whether dietary fat intake modified relations between HDL-C and polymorphisms in hepatic lipase (LIPC-514C-->T), cholesteryl ester transfer protein (CETP TaqIB), and lipoprotein lipase (LPL S447X) genes. Diet (food frequency questionnaire), plasma lipids, and LIPC, CETP, and LPL genotypes were assessed in approximately 12,000 White and African American adults. In both races and all genotypes studied, minor allele homozygotes had highest HDL-C concentrations compared to the other genotypes (P<0.001). However, main effects were modified by usual dietary fat intake. In African Americans - women somewhat more strongly than men -LIPC TT homozygotes with fat intake >or=33.2% of energy had approximately 3-4 mg/dL higher HDL-C concentrations than CC and CT genotypes. In contrast, when fat intake was <33.2% of energy, TT homozygotes had HDL-C concentrations approximately 3.5mg/dL greater than those with the CC genotype but not different from those with the CT genotype (P(interaction)=0.013). In Whites, LPLGG homozygotes had greatest HDL-C at lower total, saturated, and monounsaturated fat intakes but lowest HDL-C at higher intakes of these fats (P(interaction)<or=0.002). Dietary fat did not modify associations between CETP and HDL-C. In conclusion, these data show that plasma HDL-C differs according to LIPC, LPL, and CETP genotypes. In the case of LIPC and LPL, data suggest dietary fat modifies these relations.

Does weight loss prognosis depend on genetic make-up?

The prevalence of obesity is rising throughout the world. Indeed, obesity has reached epidemic proportions in many developed and transition countries. Obesity is a complex disease with multifactorial origin, which in many cases appears as a polygenic condition affected by environmental factors. Treatment or prevention of obesity is necessary to reverse or avoid the onset of type 2 diabetes and other obesity-related diseases. Weight loss is a complex trait that depends on many environmental, behavioural and genetic influences. An effective programme for the management of overweight and obesity must take into account all of these factors. Individual responses to weight loss interventions vary widely and reliable predictors of successful slimming are poorly understood. The individual genetic make-up participating in energy expenditure regulation, appetite control, lipid metabolism and adipogenesis, have been reported to affect the risk of treatment failure in some subjects. In addition, the genotype could also help to predict the changes in lipid profile, cardiovascular risk factors and insulin sensitivity in response to weight loss. Herein, the current evidence from human studies that support the existence of a genetic component and the participation of different polymorphisms in the prognosis of weight loss induced by interventions leading to a negative energy balance are reviewed.

Cholesteryl ester transfer protein TaqIB polymorphism and its relation to parameters of the insulin resistance syndrome in an Austrian cohort

The cholesteryl ester transfer protein (CETP) is responsible for the exchange of triglycerides and cholesteryl esters between lipoprotein particles leading to an increased hepatic clearance of HDL-cholesteryl esters. A high CETP activity reduces serum HDL levels, whereas persons without CETP activity have high HDL levels. We investigated the association of the TaqIB CETP polymorphism and various parameters of the insulin resistance syndrome in a cross sectional population based study. We included 1029 persons without known cardiovascular disease or diabetes mellitus consecutively enrolled in our SAPHIR program (Salzburg Atherosclerosis Prevention program in persons with a High Infarction Risk). Numerous clinical and laboratory data were accomplished. Insulin sensitivity was measured by a short insulin tolerance test. The TaqIB CETP polymorphism was determined by PCR, TaqI restriction and electrophoresis. 35.2% were homozygous for the prevalence (B1B1), 46.7% were heterozygous (B1B2), and 18.1% homozygous for the absence (B2B2) of the restriction site. HDL cholesterol and apolipoprotein A1 were lower and small dense low-density lipoproteins (sdLDL) higher in B1B1 compared to B2B1 and B2B2 persons. In women, we found a significant interaction effect between CETP genotype and adiposity for HDL cholesterol. B1B1 women with a BMI and a waist circumference above the median had 9.7 mg/dl lower HDL than B1B2 and 9.1 mg/dl lower HDL than B2B2 women (P < 0.001). In men, no interaction effect but a marked genotype to HDL correlation was found. There was a high CETP effect on sdLDL detected in men (P = 0.001). B1B1 men had sdLDL in 36%, B1B2 in 24.6%, and B2B2 in only 14.5%. Men with adiposity and insulin resistance had twice as many sdLDL as insulin sensitive men. We found a significant sex specific effect of the TaqIB CETP polymorphism on the insulin resistance parameters HDL-cholesterol and sdLDL in an Austrian population based study.

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.

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.

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.

The metabolic syndrome: A crossroad for genotype-phenotype associations in atherosclerosis

The metabolic syndrome comprises a set of metabolic and physiologic risk factors associated with elevated cardiovascular disease risk. The expression of each one of its major factors (hypertriglyceridemia, low high-density lipoprotein cholesterol levels, hypertension, abdominal obesity, and insulin resistance) has been found to be the result of complex interactions between genetic and environmental factors. Moreover, obesity may play a major role in triggering the metabolic syndrome by interacting with genetic variants at candidate genes for dyslipidemia, hypertension, and insulin resistance. In support of this hypothesis, several studies at multiple candidate genes have already demonstrated the significance of these interactions; however, the data and their reliability are still very limited, and in many cases replication studies are still lacking in the literature. Therefore, more studies with better epidemiologic design and standardized adiposity measures are needed to estimate the contribution of body weight and fat distribution to the genetic predisposition to the metabolic syndrome, which is the most common cardiovascular disease risk factor in industrialized societies.

Genes, diet and serum lipid concentrations: lessons from ethnically diverse populations and their relevance to coronary heart disease in Asia

PURPOSE OF REVIEW

The burden of coronary heart disease (CHD) in Asia has risen in tandem with socio-economic development and urbanization. Although all ethnic groups have been affected, some appear to be at particularly high risk. The basis of these ethnic differences remains poorly understood.

RECENT FINDINGS

Differing levels of risk factors for CHD have been observed between ethnic groups. Previous studies, however, may be confounded by a large ethnic variation in socio-economic status and place of residence. Few studies have taken dietary factors into account. Recent studies involving Chinese, Malays and Asian Indians living in Singapore suggest that neither dietary nor genetic factors, taken in isolation, sufficiently explain ethnic differences in serum lipid profiles. Several genetic variants in key candidate genes (apolipoprotein E, APOE, cholesteryl ester transfer protein, CETP and hepatic lipase, LIPC) have recently been found to modulate the association between dietary factors and serum lipid concentrations in these ethnic groups and in other populations.

SUMMARY

To fully evaluate the differences in CHD risk between ethnic groups, environmental exposures, including dietary factors need to be carefully evaluated, and gene-environment interactions that may give rise to these differences need to be taken into account. These are critical steps in the development of targeted strategies to contain the epidemic of coronary heart disease in Asia. An understanding of the basis of these differences may also provide insights into the pathogenesis of disease that one cannot get through the examination of more homogenous populations.

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 frequency of the cholesteryl ester transfer protein-TaqI B2 allele is lower in African Americans than in Caucasians

Cholesteryl ester transfer protein (CETP) mediates the exchange of cholesteryl ester for triglyceride between high density lipoprotein (HDL) and very low density lipoprotein. The B2 allele of the TaqIB polymorphism located in the first intron of the CETP gene occurs with an allele frequency of about 0.40 in Caucasians and is associated with decreased CETP levels and activity and with higher HDL-cholesterol (HDL-C) levels in this racial group. We hypothesized that the higher levels of HDL-C seen in African Americans compared with Caucasians could be in part explained by a higher frequency of the TaqI B2 allele. We determined the distribution of this polymorphism in a total of 395 African Americans and 362 Caucasian ascertained as two independent cohorts: one of healthy volunteers (NORM) and the other of patients undergoing cardiac catheterization (CATH). Of the 244 NORM-African Americans studied, 56% were B1B1, 37% B1B2 and 7% B2B2, compared with the 224 NORM-Caucasians of which 33% were B1B1, 45% B1B2 and 22% B2B2. In the CATH-African American group (n=151) 51% were B1B1, 41% B1B2 and 8% B2B2 compared with 35% CATH-Caucasians B1B1, 54% B1B2 and 11% B2B2. The frequency of the B2 allele in the Caucasian subjects in both cohorts was similar to that reported in the literature. The frequency of the B2 allele was significantly lower in African Americans than in Caucasians in the NORM group (0.26 vs 0.44; chi(2)=36.5, P<0.001) and in the CATH group (0.28 vs 0.38, chi(2)=4.7, P=0.01). Carriers of the B2 allele had higher HDL-C levels compared with B1B1 subjects in Caucasians (NORM: 57 vs 53 mg/dl, P=0.035; CATH: 47 vs 42 mg/dl, P=0.049) and in CATH-African Americans (48 vs 43 mg/dl, P=0.028), but not in NORM-African Americans (55 vs 54 mg/dl, P=0.494). There were no other significant associations between this polymorphism and other lipids and lipoproteins in the subjects studied. These results suggest that, in contrast to our hypothesis, the B2 allele of the TaqIB polymorphism is less frequent in African Americans compared with Caucasians and that this polymorphism is unlikely to contribute to the higher levels of HDL-C reported in the African American population.

5' flanking variants of resistin are associated with obesity

Diabetes and obesity have long been known to be related. The recently characterized adipocyte hormone resistin (also called FIZZ3/ADSF) has been implicated as a molecular link between impaired glucose tolerance (IGT) and obesity in mice. A search for sequence variants at the human resistin locus identified nine single-nucleotide polymorphisms (SNPs) but no coding variants. An investigation into the association of these SNPs with diabetes and obesity revealed two 5' flanking variants (g.-537 and g.-420), in strong linkage disequilibrium, that are associated with BMI. In nondiabetic individuals from the Quebec City area and the Saguenay-Lac-St-Jean region of Quebec, the g.-537 mutation (allelic frequency = 0.04) was significantly associated with an increase in BMI (P = 0.03 and P = 0.01, respectively). When the data from these two populations were combined and adjusted for age and sex, both the g.-537 (odds ratio [OR] 2.72, 95% CI 1.28-5.81) and the g.-420 variants (1.58, 1.06-2.35) were associated with an increased risk for a BMI > or =30 kg/m(2). In contrast, in case/control and family-based study populations from Scandinavia, we saw no effect on BMI with either of these promoter variants. No association was seen with diabetes in any of the population samples.

Visceral obesity and hyperinsulinemia modulate the impact of the microsomal triglyceride transfer protein -493G/T polymorphism on plasma lipoprotein levels in men

The dyslipidemic state of visceral obesity is characterized by increased plasma triglyceride levels, low high-density lipoprotein-cholesterol concentration and alterations in low-density lipoprotein (LDL) composition and concentration. A functional, non-coding microsomal triglyceride transfer protein (MTP) -493G/T polymorphism of the microsomal triglyceride transfer protein gene has been related to variations in LDL-cholesterol levels. To study the effect of the MTP -493G/T polymorphism on lipoprotein levels in visceral obesity and hyperinsulinemia, a total of 227 men were assigned into two groups on the basis of their MTP -493G/T polymorphism, including 121 GG homozygotes and 105 carriers of the T allele (92 GT and 13 TT). The two genotypic groups did not differ for their physiological characteristics nor for lipoprotein--lipid profiles, before and after adjustment for age. However, GG homozygotes were characterized by higher fasting insulin levels than carriers of the T allele (P<0.05). When the two genotypic groups were further divided on the basis of their visceral adipose tissue (AT) accumulation, assessed by computed tomography, we observed that T allele carriers with low levels of visceral AT (<130 cm(2)) had decreased plasma total cholesterol and LDL-apolipoprotein B (LDL-apoB) levels compared to viscerally obese men (P=0.035 and P=0.0001, respectively). Among GG homozygotes, no significant difference were observed. Although not significant, T allele carriers characterized by visceral obesity tended to have smaller, denser LDL particles than T allele carriers characterized by a low accumulation of visceral AT. When subjects were divided on the basis of their fasting insulin levels, it appears that hyperinsulinemic men were characterized by a deteriorated lipoprotein--lipid profile when they were carriers of the T allele compared to normoinsulinemic men. In summary, visceral obesity and hyperinsulinemia modulate the impact of the MTP -493G/T polymorphism on plasma total cholesterol and LDL-apoB levels, as well as on LDL peak particle diameter.

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.

Influence of CETP gene variation on plasma lipid levels and coronary heart disease: a survey in Taiwan

Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester from high-density lipoprotein (HDL) to very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and chylomicron in exchange for triglycerides. Two CETP genetic variation and four polymorphisms are investigated by polymerase chain reaction (PCR) and restriction enzyme digestion in a population of Taiwan. The results show that a very rare variation frequency is found for CETP intron 14 splice site G-->A change. The population shows a predominant 405Ile allele (61%), 442Asp (97.7%), intron 1Taq1B(+) G allele (52%), intron 8 Msp1(-) A allele (89%) and intron 9 EcoN1(-) T allele (59.2%) in the control group. Patients with coronary heart disease (CHD) have more CETP EcoN1(+/+) GG genotype (25.3%) than the controls (13.6%) (P=0.049). The intron 1 Taq1B(-) A allele is associated with a high HDL cholesterol and apoA1 level, the EcoN1(+) G allele with a low apoA1 level and the 442Gly with both high total cholesterol and LDL cholesterol levels. Paradoxically, the 442Gly is also present with a higher frequency (5.2%) in HDL cholesterol > or =65 mg/dl group than that in the general population (2.3%) (P=0.04).

The -629C>A polymorphism in the CETP gene does not explain the association of TaqIB polymorphism with risk and age of myocardial infarction in Icelandic men

The aim of this study was to examine whether the well-established effect of the common TaqIB polymorphism in intron 1 of the gene for cholesterol ester transfer protein (CETP) on high density lipoprotein cholesterol (HDL-C) concentration and increased risk of myocardial infarction (MI), could be explained by the recently identified -629C>A functional polymorphism in the promoter. Non-fatal MI cases (388 male) and a control group of 794 healthy men were recruited from the 30 year long prospective Reykjavik Study. In the healthy men the frequency of the TaqIB B2 allele was 0.47 (95% CI: 0.44-0.50) and there was a strong allelic association with the -629A allele (D=-0.21, P<0.0001), which had a frequency of 0.52 (95% CI: 0.49-0.56). B2B2 homozygotes displayed 15% higher HDL-C levels than subjects homozygous for the B1 allele (P<0.0001). Homozygotes for the -629A allele displayed 14% higher HDL-C concentrations than subjects homozygous for the -629C allele (P<0.0001). The frequencies of the alleles associated with lower HDL-C were significantly higher in cases compared with controls, 0.59 versus 0.53 (TaqIB B1) and 0.52 versus 0.48 (-629 C) respectively (P<0.05 for both). There was a significantly higher risk for MI in B1B1 homozygotes (OR=1.44, 95% CI: 1.10-1.87, P<0.01), compared to the other genotypes combined. This was not observed for the CC homozygotes (OR=1.16, 95% CI: 0.87-1.54). In addition, homozygotes for the TaqI B2 allele experienced a first MI 2 years later than men with other genotypes, 59 versus 61 years (P<0.05). This effect was not seen for the promoter polymorphism. These results strongly confirm the role of the CETP gene and the TaqIB variant as a risk factor for MI and suggest that another functional polymorphism is yet to be discovered in the CETP gene, that will explain the effect on MI associated with TaqIB observed in this study.

Lack of association of the common TaqIB polymorphism in the cholesteryl ester transfer protein gene with angiographically assessed coronary atherosclerosis

The anti-atherogenic effect of cholesteryl ester transfer protein (CETP) genetic variants associated with lowered enzyme activity is controversial. Moreover, in a few studies, this effect has been evaluated in the presence of a certain risk factor constellation. We addressed this issue in a case-control study, where 415 subjects with angiographically documented coronary artery disease (CAD +), 397 subjects without CAD (in 215, CAD was excluded by coronarography (CAD-)), and 188 healthy population controls, were screened for the CETP TaqIB polymorphism. The prevalence of the low-activity TaqIB2 allele was 0.396 in CAD+, and 0.428 and 0.416 in CAD- and population controls, respectively (p = 0.40). Its presence was significantly associated with increased high-density lipoprotein cholesterol (HDL-C) in population controls (1.40 +/- 0.40 mmol/l in B1B1, 1.52 +/- 0.39 mmol/l in B1B2 and 1.58 + 0.46 mmol/l in B2B2; p < 0.03 for trend), but not in the other groups. The CETP TaqIB polymorphism accounted for < 1% of the HDL-C variance in the whole cohort (p = 0.048). After adjustment for other risk factors, the CETP TaqIB2 allele was found not to be associated with significant changes in CAD risk independently of an assumed either dominant (odds ratio (OR) 0.97; 95% confidence interval (CI) 0.66-1.44; p = 0.89) or recessive effect (OR 0.68; 95% CI 0.42-1.12; p = 0.13). The CETP TaqIB polymorphism did not show a significant interaction with other risk factors in influencing CAD risk. Our findings do not support the hypothesis that a genetic variant resulting in lowered CETP activity is associated with reduced risk of coronary atherosclerosis.

Clustering of metabolic abnormalities in obese individuals: the role of genetic factors

The objective of this paper is to review the current evidence in support of genetic factors underlying the clustering of components of the metabolic syndrome in obese individuals. It has become clear that individual features of the metabolic syndrome are partially determined by familial factors some of which are unique to a given component and others that are shared among several features. A few candidate genes, encoding proteins of glucose, insulin and lipid metabolism, lipolytic cascade, fatty acid intestinal absorption, glucocorticoid metabolism, haemostasis and blood pressure, have been associated with a clustering of metabolic abnormalities, although the functional significance of these associations remains to be established. Furthermore, genetic polymorphisms, such as those detected at several lipoprotein metabolism loci, can modulate the relationships between different components of the metabolic syndrome. An overfeeding study conducted on identical twins has demonstrated that genetic factors play an important role in the responsiveness to changing energy balance conditions. Leptin receptor, beta2 adrenergic receptor and glucocorticoid receptor gene polymorphisms have been associated with an augmented clustering of metabolic abnormalities in response to overfeeding. Gene-gene interaction effects between markers of the alpha2A, beta2 and beta3 adrenergic receptor genes on components of the metabolic syndrome have been described. Genetic factors also seem to modify the responsiveness of metabolic syndrome features to endurance training. A growing understanding of the genetic architecture of the metabolic syndrome may help in the prevention of this condition. The reduction of excess body fat, the most common clinical feature among the cluster of metabolic abnormalities, should be the focus of the prevention and treatment of the metabolic syndrome.

Effects of comicronised fenofibrate on lipid and insulin sensitivity in patients with polymetabolic syndrome X

BACKGROUND

This study investigated the effects of comicronised fenofibrate in patients with dyslipidemia and polymetabolic syndrome X.

DESIGN

After a 6-week dietary run-in phase, 37 male patients eligible on lipid criteria entered a 12-week treatment phase consisting of diet plus one capsule daily containing 200 mg of comicronised fenofibrate (Lipanthyl(R)).

RESULTS

A significant reduction in plasma concentrations of total cholesterol, LDL cholesterol and triglyceride was observed after 4, 8 and 12 weeks of treatment with fenofibrate. The improvement in the atherogenic index LDL/HDL cholesterol from a pretreatment 3.8 to 3.0 after treatment was highly statistically significant and may be judged as satisfactory. Significant changes were also observed in haemostatic factors (fibrinogen reduced by 19%, factor VII activity reduced by 18%). Fasting serum insulin levels and insulin response (area under the curve) after oral glucose load were significantly reduced by 26.8% and 18.7%, respectively, indicating an improvement of insulin sensitivity. Systolic and diastolic blood pressure were significantly reduced. Uric acid was significantly reduced by 21.6%.

CONCLUSION

These favourable effects of comicronised fenofibrate both on lipid and non lipid parameters, including insulin sensitivity, may confer to this product a particular interest in the treatment of patients with polymetabolic syndrome X.