Association of apolipoprotein E and B polymorphisms with serum lipids

WWOX gene is associated with HDL cholesterol and triglyceride levels

Background

Altered lipid profile, and in particular low HDL and high triglyceride (TG) plasma levels, are within the major determinants of cardiovascular diseases. The identification of quantitative trait loci (QTL) affecting these lipid levels is a relevant issue for predictive purposes. The WWOX gene has been recently associated with HDL levels. This gene is located at chromosome 16q23, a region previously linked to familial combined hyperlipidemia (FCHL) and HDL. Our objective is to perform a genetic association analysis at the WWOX gene region with HDL, TG and TG/HDL ratio.

Methods

A quantitative association analysis performed in 801 individuals selected from the Spanish general population.

Results

For HDL levels, two regions of intron 8 display clustering of positive signals (p < 0.05) but none of them was associated in the haplotypic analysis (0.07 ≤ p ≤ 0.165). For TG levels not only intron 8 but also a 27 kb region spanning from the promoter region to intron 4 are associated in this study. For the TG/HDL genetic association analysis, positive signals are coincident with those of the isolated traits. Interestingly, haplotypic analysis at the 5' region showed that variation in this region modified both HDL and TG levels, especially the latter (p = 0.003).

Conclusions

Our results suggest that WWOX is a QTL for both TG and HDL.

5' ins/del and 3' VNTR polymorphisms in the apolipoprotein B gene in relation to lipids and coronary artery disease

BACKGROUND

Studies that considered apolipoprotein B (APOB) gene polymorphisms as risk factors for coronary artery disease (CAD) have reported conflicting results. We sought to analyze the association between 5' ins/del and 3' VNTR polymorphisms of APOB, lipid parameters and CAD risk.

METHODS

We recruited 251 patients with CAD, documented by coronary angiography, and 94 controls. Genotyping was performed by PCR. Lipids and apolipoproteins were measured.

RESULTS

5' ins/del (ins/ins, ins/del, del/del) and 3' VNTR (LL, SS, LS) polymorphism frequencies were significantly (p<0.05) different between controls and CAD patients. LL and del/del were significantly associated with higher levels of apolipoprotein B (apoB), total cholesterol/high-density lipoprotein cholesterol ratio and apoB/apoA-I ratio (p<0.05) and with increased risk of CAD. The odds ratio for significant coronary stenosis associated with del/del was 3.2 (95% CI 1.6-36.42) (p=0.032) and with LL was 2.2 (95% CI 1.1-5.1) (p=0.042).

CONCLUSIONS

The two polymorphisms exert an impact on lipid levels and contribute to the susceptibility to the development of CAD.

Apolipoprotein E polymorphism and changes in serum lipids during a family-based counselling intervention

OBJECTIVE

To compare serum lipids and their changes during a family-based health education in children aged 6-17 years with or without the epsilon4 allele of the gene encoding apolipoprotein E (apoE).

DESIGN

An intervention study.

SETTING

A family-based prevention of risk factors of coronary heart disease in Eastern Finland. The programme consisted of two counselling meetings at children's schools and three at children's homes.

SUBJECTS

Four hundred and thirty-nine children with a family history of cardiovascular diseases (CVD) participated in a family-based health education. The children were divided into two groups according to apoE genotype. The risk group consisted of 143 children having apoE epsilon4 allele (genotype epsilon3/4 or epsilon4/4) and the non-risk group of 296 children without apoE epsilon4 allele (epsilon2/3 or epsilon3/3). The final sample of the follow-up study included 354 (81%) children (114 and 240, respectively).

RESULTS

Baseline differences were found in low-density lipoprotein cholesterol (LDL-C) (P=0.007) and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio (P=0.030) among boys and in total cholesterol (TC)/HDL-C (P=0.008) and LDL-C/HDL-C ratios (P=0.006) among girls. Differences between groups in changes during the follow-up were observed only for TC/HDL-C ratio (P-value adjusted for age=0.049) among boys.

CONCLUSIONS

At baseline, children with apoE epsilon4 allele had on average a more unfavourable lipid profile than those without apoE epsilon4 allele. However, the effect of about 33 months' family-based health education on plasma lipids did not depend on apoE genotype in children with a family history of CVD.

Apolipoprotein E polymorphism and atherosclerosis

The relationship between apolipoprotein (apo) E and vascular disease has been the subject of a considerable amount of research. However, this relationship is far from clearly defined. This deficiency appears to be due to a multitude of factors. Among these are differences in ethnicity, age (and possibly gender), diagnostic criteria, and environmental factors (eg, diet and smoking) that have contributed to the contradictory findings. Several diseases and their treatment may also influence this relationship. There are also documented interactions between apo E genotypes and other genes or vascular risk factors. One possible clinically relevant application of identifying the apo E genotype could be to assess the response to a particular drug treatment. It may also be that apo E polymorphism will become a good predictor of vascular death (eg, from myocardial infarction or stroke) rather than an indicator of the risk of developing vascular disease but without an acute ischemic event. More research is required to define the place of apo E genotyping in the management of vascular disease in its various forms. Whatever the future brings, the evaluation of apo E genotypes will need to be rapid, cheap, and technically undemanding before this investigation becomes widely available and clinically relevant.

Physical activity may modulate effects of ApoE genotype on lipid profile

Increased levels of physical activity may improve the lipid profile, but is this effect identical across apolipoprotein E (apoE) genotypes? A population-based cross-sectional survey conducted from 1999 to 2000 included 1708 randomly selected men and women aged 35 to 74 years. A validated physical activity questionnaire measured, for each participant, the total energy expenditure and its percentage used in high-intensity activities (%high-intensity activity), eg, brisk walking and sports. The effects of the apoEx%high-intensity activity interaction on the lipid profile were investigated by using multiple linear regression models. Among men, increased %high-intensity activity had greater protective effects in the apoE4 group regarding (1) high density lipoprotein (HDL) cholesterol (P<0.001), compared with either the apoE2 (interaction P=0.05) or apoE3 (interaction P<0.03) groups, and (2) triglycerides (P<0.03), compared with the apoE3 group (interaction P=0.07). A 10% increase of %high-intensity activity by an apoE4 man would correspond with a 0.07-mmol/L increase in HDL cholesterol and a -0.15-mmol/L decrease in triglycerides. Among women, only the protective effects of physical activity on HDL cholesterol in the apoE4 group versus the apoE2 group was statistically significant. Spending a larger fraction of the total energy expenditure in high-intensity activities may counteract the atherogenic effects of the epsilon4 allele on the lipid profile.

Polymorphism of the apolipoprotein E gene and early carotid atherosclerosis defined by ultrasonography in asymptomatic adults

Clinical and autoptical studies have suggested a predisposing role of the allele E4 of apolipoprotein E (apoE) in the development of atherosclerosis and cardiovascular disease. To investigate the possible contribution of apoE allele polymorphism to the carotid intima-media thickness (IMT) as assessed by ultrasound, we studied 260 asymptomatic nondiabetic subjects (121 men, 139 women; mean +/- SD age, 53 +/- 7 years), randomly selected from the population register of the inhabitants of Trieste, Italy. B-mode ultrasound was used to quantify the maximum IMT at 12 sites on the near and far wall of the common, bifurcation, and internal carotid arteries. ApoE genotypes were determined from amplified apoE sequences by restriction isotyping. The frequencies of E2, E3, and E4 alleles were 0.073, 0.827, and 0.100, respectively. As expected, subjects with E4 allele had the highest levels of total serum cholesterol and LDL cholesterol, subjects with E2 allele had the lowest levels, and those with E3 genotype had intermediate levels. The echographic measurements of carotid IMT showed increasing values from E2 to E4 carriers. After adjustment for total and LDL cholesterol serum levels, triglycerides, ratio of LDL to HDL cholesterol, age, sex, and body mass index, ANCOVA showed that the common carotid IMT was significantly greater (P = .029) in subjects with E4 allele compared with E3 carriers. Our data confirm the influence of apoE4 on cholesterol levels and clearly show that apoE genotype affects carotid atherosclerosis in its early stages in middle-aged asymptomatic subjects.

The effect of physical activity on serum total and low-density lipoprotein cholesterol concentrations varies with apolipoprotein E phenotype in male children and young adults: The Cardiovascular Risk in Young Finns Study

Apolipoprotein E (apo E) determines serum total (TC) and low-density lipoprotein (LDL-C) cholesterol concentrations and is thus associated with coronary heart disease (CHD) risk. We studied if the effect of physical activity (PA) on serum TC and LDL-C concentrations varies with apo E phenotype in a population-based sample of children and young adults with regular PA. The study cohort consisted of subjects aged 9, 12, 15, 18, 21, and 24 years in 1986 (N = 1,498) participating in a large multicenter study of cardiovascular risk factors in children and young adults. Serum lipid concentrations were determined enzymatically, and apo E phenotypes by isoelectric focusing and immunoblotting. The composition of the diet was determined by a 48-hour recall method, and a PA index was calculated on the basis of frequency, intensity, and duration of activity assessed by a questionnaire. LDL-C (P = .0082), TC (P = .014), and the high-density lipoprotein cholesterol (HDL-C)/TC ratio (P = .0004) responses to exercise varied with apo E phenotype. The effect of PA on LDL-C, TC, or HDL/TC was not found in apo E phenotype E4/4. A moderate inverse effect of PA on TC and LDL-C and a positive effect on HDL/TC was found in subjects with E4/3 and E3/3 phenotypes. Similar but stronger associations were found between these variables within the group of E3/2 males. The effect of PA on serum lipid levels was strongest within the phenotype E3/2. These associations were not explained by dietary habits. Apo E phenotype partly determines the effect of PA on serum TC and LDL-C in Finnish male children and young adults with regular PA.

Polymorphisms of the apolipoprotein E gene and severity of coronary artery disease defined by angiography

In a recent study, we could account for only about 50% of the variance in angiographically determined severity of coronary artery disease (CAD) with use of lipid and clinical variables as predictors. To explore the possible contribution of the apolipoprotein (apo) E polymorphisms to the severity of CAD (rather than to its occurrence), we studied 424 white patients aged 65 years or less consecutively referred for coronary angiography. Among the 304 male and 120 female patients, there were 110 with no significant CAD and 118 with one, 96 with two, and 100 with three significantly diseased major coronary arteries (> 50% luminal obstruction). The allele frequencies were 0.068 for E2, 0.759 for E3, and 0.172 for E4. The E2 frequency was slightly lower and E4 higher than the frequencies reported for healthy white populations (E2: 0.072 to 0.130; E4: 0.136 to 0.160). There was a clear association between the apo E genotype and the number of significantly diseased vessels (regression coefficient = .12, P = .008). The frequency of the E4 allele increased linearly with the increase in CAD severity in both sexes (for none, one, two, and three significantly diseased vessels; female patients: 0.136, 0.161, 0.200, and 0.324; male patients: 0.136, 0.167, 0.132, and 0.229, respectively, P < .01). The frequencies of the E2 allele, on the other hand, decreased with increasing severity (for none, one, two, and three significantly diseased vessels; female patients: 0.091, 0.018, 0.050, and 0.029; male patients: 0.073, 0.089, 0.072, and 0.054, respectively, P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging and genetic variation of plasma apolipoproteins. Relative loss of the apolipoprotein E4 phenotype in centenarians

We determined the common polymorphism of apolipoprotein E (E2, E3, and E4), apolipoprotein B Xba I polymorphism, and apolipoprotein C-III Sst I polymorphism in almost all Finnish centenarians alive in 1991 (n = 179/185). Plasma lipid and lipoprotein levels in different apolipoprotein genotypes were also measured. In comparison with younger Finnish populations studied previously, the frequency of the apolipoprotein E epsilon 2 allele was almost twice as high (7.0% versus 4.1%; P < .05) and that of the epsilon 4 allele only approximately one third as high (8.4% versus 22.7%; P < .001) in the centenarians. Plasma cholesterol and high-density lipoprotein cholesterol levels tended to be lowest in the group with the epsilon 2 allele (4.33 mmol/L and 1.41 mmol/L, respectively), intermediate in those with the epsilon 3 allele (4.57 mmol/L and 1.48 mmol/L, respectively), and highest in those with the epsilon 4 allele (4.82 mmol/L and 1.60 mmol/L, respectively). The frequencies of the apolipoprotein B X1 and X2 alleles (Xba I restriction site absent or present, respectively) among the centenarians and among the young Finns were not significantly different, whereas the apolipoprotein C-III S2 allele (Sst I restriction site present) occurred more often in the centenarians (frequency, 12.9%) than in the youngest reference population (frequency, 8.8%; P < .05). Centenarians with the apolipoprotein B X2X2 genotype and apolipoprotein E4 phenotype had a higher mean plasma cholesterol level than those with the X1X1 genotype and E2 phenotype (5.24 versus 3.43 mmol/L; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Screening for mutations in the exon 26 of the apolipoprotein B gene in hypercholesterolemic Finnish families by the single-strand conformation polymorphism method

To date, the only known apolipoprotein B (apo B) mutation causing hypercholesterolemia is the apo B 3500 Arg-->Gln or the familial defective apo B (FDB) mutation. This mutation has not been detected in the Finnish population. We have set up a systematic single-strand conformation polymorphism (SSCP) analysis-based screening method to search for other mutations in the exon 26 of the apo B gene in 21 Finnish hypercholesterolemic probands. The 7572-bp exon 26 covers half of the coding region of the gene including the DNA sequence coding for the putative low-density lipoprotein (LDL) receptor binding site on the apo B protein. Exon 26 was amplified as six 1190- to 1435-bp fragments, each of which was further split into three smaller 213- to 579-bp segments by restriction enzymes. These digestion products were run on nondenaturing polyacrylamide gels using at least three different electrophoretic conditions and autoradiographed. All previously known genetic variants in the exon 26 were detected by the SSCP method. A C-->T change at nucleotide 7064, in complete association with the XbaI site, was characterized by direct sequencing. This variant did not affect the amino acid sequence of the apo B protein. The SSCP-based procedure appears suitable for systematic screening for DNA sequence changes in large coding regions.

DNA polymorphisms of the apolipoprotein B gene are associated with obesity and serum lipids in healthy Indians in Singapore

Three DNA polymorphisms (Ins/Del, XbaI and EcoRI) of the apolipoprotein B gene and their influence on body-mass index, serum lipids and apolipoprotein levels were studied in 181 healthy Indians of both sexes (121 males and 60 females), aged between 17 and 71 years. The frequencies of X+ (XbaI) and Del (Ins/Del) of the signal peptide region in Indians were found to be significantly lower (0.17 and 0.11, respectively) compared to the frequencies in Caucasians (0.50 and 0.32, respectively) (P < 0.025). The frequency of E- (EcoRI) was similar to that in Caucasians (0.10 vs 0.15). A highly significant linkage disequilibrium was observed between the XbaI site and Ins/Del polymorphism of the apo B gene in this sample (X2 = 31.9, P < 0.001). The simultaneous presence of Del and X+ allele was significantly associated with higher body mass index (X2 = 11.43, P < 0.005), serum total cholesterol (X2 = 5.11; P < 0.025) and triglyceride (X2 = 6.42; P < 0.025) levels. Mean values of adjusted BMI and serum triglyceride levels were found to be 29.0 +/- 1.92 vs 23.7 +/- 0.67 (P < 0.025) and 278.0 +/- 60.78 vs 140.4 +/- 15.43 mg/dl (P < 0.05), respectively, in subjects with Del and X+ compared to others. The multiple regression tests showed that 3.3 and 5.8% of the total variability of BMI is explained by Ins/Del and XbaI polymorphism, respectively, in this sample (P = 0.06 and 0.02), while 3.8% of serum triglyceride levels was explained by Ins/Del polymorphism of the apo B gene (P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)