Association between the TaqIB polymorphism in the cholesteryl ester transfer protein gene locus and postprandial plasma lipoprotein levels in heterozygotes for familial hypercholesterolemia

Quantile-dependent expressivity of postprandial lipemia

Purpose

“Quantile-dependent expressivity” describes an effect of the genotype that depends upon the level of the phenotype (e.g., whether a subject’s triglycerides are high or low relative to its population distribution). Prior analyses suggest that the effect of a genetic risk score (GRS) on fasting plasma triglyceride levels increases with the percentile of the triglyceride distribution. Postprandial lipemia is well suited for testing quantile-dependent expressivity because it exposes each individual’s genotype to substantial increases in their plasma triglyceride concentrations. Ninety-seven published papers were identified that plotted mean triglyceride response vs. time and genotype, which were converted into quantitative data. Separately, for each published graph, standard least-squares regression analysis was used to compare the genotype differences at time t (dependent variable) to average triglyceride concentrations at time t (independent variable) to assess whether the genetic effect size increased in association with higher triglyceride concentrations and whether the phenomenon could explain purported genetic interactions with sex, diet, disease, BMI, and drugs.

Results

Consistent with the phenomenon, genetic effect sizes increased (P≤0.05) with increasing triglyceride concentrations for polymorphisms associated with ABCA1, ANGPTL4, APOA1, APOA2, APOA4, APOA5, APOB, APOC3, APOE, CETP, FABP2, FATP6, GALNT2, GCKR, HL, IL1b, LEPR, LOX-1, LPL, MC4R, MTTP, NPY, SORT1, SULF2, TNFA, TCF7L2, and TM6SF2. The effect size for these polymorphisms showed a progressively increasing dose-response, with intermediate effect sizes at intermediate triglyceride concentrations. Quantile-dependent expressivity provided an alternative interpretation to their interactions with sex, drugs, disease, diet, and age, which have been traditionally ascribed to gene-environment interactions and genetic predictors of drug efficacy (i.e., personalized medicine).

Conclusion

Quantile-dependent expressivity applies to the majority of genetic variants affecting postprandial triglycerides, which may arise because the impaired functionalities of these variants increase at higher triglyceride concentrations. Purported gene-drug interactions may be the manifestations of quantile-dependent expressivity, rather than genetic predictors of drug efficacy.

The influence of gene polymorphisms on postprandial triglyceride response after oral fat tolerance test meal in patients with diabetes mellitus

AIMS

We evaluated the influence of CETP (rs5882 and rs708272), APOE (rs7412, rs429358) and LPL (rs328) gene polymorphisms on triglyceride (TG) response to oral fat tolerance test (OFTT) meal in patients with well-controlled type 2 diabetes mellitus (T2DM).

METHODS

Fifty-one men underwent OFTT and according to postprandial TG response patients were divided into two subgroups (positive [TG ≥ 220 mg/dL, 31 patients] and negative [TG < 220 mg/dL, 20 patients]). All patients were genotyped, and study variants were detected using polymerase chain reaction (PCR) and restricted fragment length polymorphism (RFLP) analysis.

RESULTS

Patients with genotype SS of LPL gene compared with genotype SX had more frequently positive response to OFTT (P = .04) and lower high-density lipoprotein cholesterol (HDL-C) concentration (P = .03). Patients with positive response to OFTT and genotype SS of LPL gene compared with genotype SX had lower AUC (area under the curve)-TG, 1744 (368) vs 1887 (807) mg/dL/h, respectively, P = .04. CETP and APOE gene polymorphisms had no influence on postprandial TG response to OFTT.

CONCLUSIONS

In patients with well-controlled T2DM, LPL but not CETP and APOE gene polymorphisms influenced TG postprandial response. Particularly, S447 allele carriers of LPL gene presented more frequently positive postprandial TG response to OFTT compared with 447X allele carriers. No differences were found between allele carriers of patients with negative response to OFTT in any other studied gene polymorphism.

Dyslipidemia and cardiovascular disease in women

Cardiovascular disease is the major cause of death in women in developed countries. Dyslipidemia is highly prevalent in women, particularly after the menopause. Elevated low-density lipoprotein cholesterol (LDL-C) has been identified as the key lipid parameter in both genders whereas HDL-cholesterol and triglycerides have been more closely associated, in some studies, with cardiovascular risk in women. Menopause has been shown to be associated with an increase in total and LDL-cholesterol and a decrease in HDL-cholesterol (predominantly in the HDL2 subfraction). Despite its beneficial effects on the lipid profile, hormone replacement therapy is not recommended for primary or secondary prevention of cardiovascular disease in women. The latest meta-analysis of statin trials with gender-specific outcomes showed a similar benefit in women and men. The addition of ezetimibe to simvastatin in patients with acute coronary syndromes showed a further reduction of the primary endpoint in both genders. While there are no gender-related differences in drug treatment of dyslipidemia, current guidelines, to avoid overtreatment, strongly suggest risk estimation before initiating lipid-lowering treatment in women without manifest cardiovascular disease.

Postprandial lipemia as a cardiometabolic risk factor

High levels of fasting circulating triglycerides (TG) represent an independent risk factor for cardiovascular disease. In western countries, however, people spend most time in postprandial conditions, with continuous fluctuation of lipemia due to increased levels of TG-rich lipoproteins (TRLs), including chylomicrons (CM), very low density lipoproteins (VLDL), and their remnants. Several factors contribute to postprandial lipid metabolism, including dietary, physiological, pathological and genetic factors. The presence of coronary heart disease, type 2 diabetes, insulin resistance and obesity is associated with higher postprandial TG levels compared with healthy conditions; this association is present also in subjects with normal fasting TG levels. Increasing evidence indicates that impaired metabolism of postprandial lipoproteins contributes to the pathogenesis of coronary artery disease, suggesting that lifestyle modifications as well as pharmacological approaches aimed at reducing postprandial TG levels might help to decrease the cardiovascular risk.

Cholesteryl Ester Transfer Protein and ATP-Binding Cassette Transporter A1 Genotype Alter the Atorvastatin and Simvastatin Efficacy

We compared the efficacy of atorvastatin with simvastatin according to cholesteryl ester transfer protein (CETP) and adenosine triphosphate-binding cassette transporter A1 ( ABCA1) genes. Patients treated with atorvastatin (n = 254) or simvastatin (n = 332) were genotyped for CETP (TaqIB and I405V) and ABCA1 (R219K) genetic variants. For genotype B1B2, atorvastatin compared with simvastatin treatment resulted in a greater decrease in total cholesterol (35.4% vs 31.6%, P = .035) and a lower increase in high-density lipoprotein cholesterol (2% vs 8%, P = .05). For genotype B2B2, atorvastatin compared with simvastatin treatment resulted in a lower decrease in low-density lipoprotein cholesterol (31.85 vs 42%, P = .029). For genotypes RR and KK, atorvastatin compared with simvastatin treatment resulted in a greater decrease of triglycerides (27% vs 17% and 35% vs 15%, respectively; P = .02 for all comparisons). The TaqIB and R219K (opposite to I405V) gene polymorphisms seem to modify the response to lipid-lowering therapy with simvastatin or atorvastatin treatment.

Update on genetics of postprandial lipemia

The relationship between alimentary lipemia and coronary disease is of great interest in view of the epidemiological and experimental evidence that underlies it. The modulation of such phenomena is influenced by both genetic and environmental factors, thus explaining their extraordinary individual variance. Over the last two decades there has been an explosion of research in this area, with often conflicting findings reported in the literature. In this study we have presented the current evidence linking a number of candidate genes (APOA1/C3/A4/A5 cluster, ABCA1, CETP, GCKR, HL, IL-6, LPL, PLIN, and TCF7L2) to the modulation of the postprandial lipid metabolism. Increased knowledge of how these and other genes influence postprandial response should increase the understanding of personalised nutrition.

Cholesteryl ester transfer protein gene and effectiveness of lipid lowering of atorvastatin

Cholesteryl ester transfer protein (CETP) plays a key role in lipid metabolism. Thus, variations in the CETP gene may be clinically relevant. Newly started atorvastatin users (n=212) were genotyped for CETP genetic variants (TaqIB and I405V). Homozygotes for B1 allele of TaqIB polymorphism had lower plasma high density lipoprotein cholesterol (HDL-C) compared with B1B2 or B2B2 genotypes (p=0.03, for each). Homozygotes for I allele of I405V polymorphism had lower plasma HDL-C compared with IV or VV genotypes (p=0.001, for each). In the whole population, the B1 carriers increased HDL-C levels by 4% after atorvastatin treatment, compared with B2 carriers, where a 4% decrease occurred (p=0.03). Also homozygotes for B1 allele decreased triglyceride levels to a lesser, though not significant, degree compared to B1B2 or B2B2 genotypes. CETP TaqIB or I405V polymorphisms seem to modify the lipid lowering response to atorvastatin treatment. This knowledge may help design more effective hypolipidaemic treatment.

Postprandial metabolic heterogeneity in men with primary dyslipidaemia

INTRODUCTION

Familial combined hyperlipidaemia (FCH) and familial hypercholesterolaemia (FH) have been strongly linked to premature coronary artery disease. Postprandial hypertriglyceridaemia is also associated with atherosclerotic disease. We evaluated the postprandial lipaemia in men with FCH and FH and compared them to a group of healthy men.

MATERIAL AND METHODS

The study population consisted of 83 men: 34 FCH, 29 FH and 20 healthy. The FCH and FH groups were further divided into five subgroups, according to their lipid phenotype: FCH-IIA (n = 13), FCH-IIB (n = 10), FCH-IV (n = 11), FH-IIA (n = 21) and FH-IIB (n = 8). Postprandial lipaemia was evaluated by the areas under the curve for triglyceride (TG) concentrations (TG-AUC).

RESULTS

The TG levels after oral fat tolerance test were significantly higher in FCH, compared to FH and healthy groups (TG-AUC in mg/dl/h; 2678 ±1415 vs. 1503 ±1147 and 1011 ±652 respectively, p < 0.001). The postprandial response was higher in FCH-IV and FCH-IIB, compared to FCH-IIA (TG-AUC in mg/dl/h; 3220 ±824 or 3409 ±770 vs. 1863 ±577 respectively, p < 0.001, for both comparisons). The FCH-IIA group showed higher postprandial TG levels when compared to FH-IIA (TG-AUC in mg/dl/h; 1863 ±577 vs. 1374 ±428 respectively, p = 0.008). There were no significant differences between FH-IIB and FCH-IIB subgroups. There was a significant correlation (r = 0.907, p < 0.001) between the postprandial TG-AUC and fasting TG levels in all FCH subjects.

CONCLUSIONS

All phenotypes of FCH and the FH IIB phenotype demonstrate an exaggerated postprandial response that could partially contribute to the high cardiovascular risk. These patients should be identified and treated early with the appropriate hypolipidaemic agents.

Cholesteryl ester transfer protein gene polymorphisms and longevity syndrome

Purpose:

High levels of high density lipoprotein (HDL) cholesterol are associated with a decreased risk of coronary heart disease (CHD). Subjects with high levels of HDL cholesterol (>70 mg/dl; 1.79 mmol/l) as well as high levels of low density lipoprotein (LDL) cholesterol, could represent a group with longevity syndrome (LS). Since HDL particles are influenced by cholesteryl ester transfer protein (CETP) activity, it is worth studying the CETP polymorphism. The aim of the study was to detect whether 2 genetic variants of the CETP are associated with the LS.

Subjects and Methods:

The study population consisted of 136 unrelated men and women with no personal and family history of CHD; 69 met the criteria for LS and 67 did not meet these criteria and had “normal” HDL cholesterol (>40 and <70 mg/dl; >1.03 and <1.79 mmol/l). All patients were genotyped for the TaqIB and I405V polymorphisms.

Results:

The B2 allele frequency of TaqIB polymorphism was higher in the LS in comparison with the non-LS group (p=0.03) whereas B1 allele frequency was higher in the non-LS group (p=0.03).

Conclusions:

Gene polymorphisms could help decide whether individuals who have increased levels of both LDL cholesterol and HDL cholesterol require treatment. Some of the prerequisites could include that subjects with LS should not only have very high levels of HDL cholesterol but also favorable gene polymorphisms. However, further investigations with a larger sample and including other gene polymorphisms, are needed.

Sex-associated effect of CETP and LPL polymorphisms on postprandial lipids in familial hypercholesterolaemia

Background

This study assessed the gender-specific influence of the cholesteryl ester transfer protein (TaqIB, I405V) and lipoprotein lipase (S447X) polymorphisms on the response to an oral fat tolerance test in heterozygotes for familial hypercholesterolaemia.

Methods

We selected and genotyped 80 men and postmenopausal women heterozygous for familial hypercholesterolaemia (main group) as well as 11 healthy control subjects. Patients were subgrouped based on their response to oral fat tolerance test. The oral fat tolerance test was defined as pathological when postprandial triglyceride concentration was higher than the highest triglyceride concentration observed in healthy subjects (220 mg/dl) at any time (2, 4, 6 or 8 h).

Results

In the pathological subgroup, men had significantly higher incremental area under the curve after oral fat tolerance test than postmenopausal women. Furthermore, multivariate analysis revealed a gender association of TaqIB and I405V influence on postprandial lipaemia in this subgroup.

Conclusion

In conclusion, it seems that gender and TaqIB polymorphism of the cholesteryl ester transfer protein gene were both associated with the distribution of triglyceride values after oral fat tolerance test, only in subjects with a pathological response to oral fat tolerance test. Specifically, men carrying the B2 allele of the TaqIB polymorphism showed a higher postprandial triglyceride peak and a delayed return to basal values compared with women carrying B2. However, further investigations in larger populations are required to replicate and confirm these findings.