Low density lipoprotein ligand-receptor interactions in normal healthy individuals characterized by their XbaI apolipoprotein B DNA polymorphism

Associations of the APOB rs693 and rs17240441 polymorphisms with plasma APOB and lipid levels: a meta-analysis

BACKGROUND

The associations of the apolipoprotein B gene (APOB) rs693 and rs17240441 polymorphisms with plasma levels of APOB and lipids have been widely explored, but the results were inconclusive. This meta-analysis aimed to clarify the associations of the rs693 and rs17240441 polymorphisms with fasting APOB and lipid levels.

METHODS

Sixty-one studies (50,018 subjects) and 23 studies (8425 subjects) were respectively identified for the rs693 and rs17240441 polymorphisms by searching in PubMed, Google Scholar, Web of Science, Cochrane Library, Wanfang, VIP and CNKI databases. The following information was collected for each study: first author, age, gender, ethnicity, health condition, sample size, genotyping, lipid assay method, mean and standard deviation or standard error of APOB and lipid variables by genotypes. A dominant model was used for this meta-analysis.

RESULTS

The carriers of the rs693 variant allele (T) had higher levels of APOB [standardized mean difference (SMD) = 0.26, 95% confidence interval (CI) = 0.16-0.36, P < 0.01], triglycerides (TG) (SMD = 0.12, 95% CI = 0.05-0.20, P < 0.01), total cholesterol (TC) (SMD = 0.24, 95% CI = 0.17-0.30, P < 0.01) and low-density lipoprotein cholesterol (LDL-C) (SMD = 0.22, 95% CI = 0.14-0.30, P < 0.01), and lower levels of high-density lipoprotein cholesterol (HDL-C) (SMD = -0.06, 95% CI = -0.11-0.01, P = 0.01) than the non-carriers. The carriers of the rs17240441 deletion allele had higher levels of APOB (SMD = 0.13, 95% CI = 0.06-0.20, P < 0.01), TC (SMD = 0.17, 95% CI = 0.07-0.26, P < 0.01) and LDL-C (SMD = 0.15, 95% CI = 0.07-0.23, P < 0.01) than the non-carriers.

CONCLUSIONS

The rs693 polymorphism is significantly associated with higher levels of APOB, TG, TC and LDL-C, and lower levels of HDL-C. The rs17240441 polymorphism is significantly associated with higher levels of APOB, TC and LDL-C. Further studies are needed to elucidate the underlying mechanisms.

Molecular variation at the apolipoprotein B gene locus in relation to lipids and cardiovascular disease: a systematic meta-analysis

Apolipoprotein B (apoB) is the sole protein component of low-density lipoprotein (LDL) and is thought to play an important role in atherogenesis. We performed a meta-analysis of the associations between the three most frequently investigated polymorphisms (XbaI, signal peptide insertion/deletion, EcoRI) in the apolipoprotein B (APOB) gene, lipid parameters, and the risk of ischemic heart disease (IHD). We restricted our analysis to Caucasians. Homozygotes for the XbaI X+ allele had significantly elevated levels of LDL cholesterol (LDL-C) and apoB, but a decreased risk (OR=0.80; 95%CI: 0.66-0.96) of IHD. Homozygosity for the signal peptide deletion allele was associated with similarly increased levels of LDL-C and apoB, and with an increased risk of IHD (OR=1.30; 95%CI: 1.08-1.58). Subjects homozygous for the rare EcoRI allele had significantly decreased levels of total and LDL cholesterol, but unaltered risk of IHD. We conclude that all three polymorphic apoB sites are associated with altered lipid levels, but not necessarily with a consistently altered risk of IHD. These data suggest that the relationship between apoB levels, hypercholesterolemia and IHD risk cannot have a simple molecular basis in the apoB gene.

DNA polymorphisms of the apoprotein B gene are associated with altered plasma lipoprotein concentrations but not with perceived risk of cardiovascular disease: European Atherosclerosis Research Study

Three polymorphisms of the apoprotein B gene (XbaI, signal peptide insertion/deletion and the 3'-variable number of tandem repeats) selected on the basis of previously published reports as likely to be the most informative, were investigated in a cross-cultural study in Europe. Students from 14 universities, grouped for analyses into five regions, were recruited as cases (n = 682) if they had a paternal history of premature myocardial infarction. For comparison, twice the number of age- and sex-matched controls (n = 1312) were recruited from the same student populations. There were significant regional differences in allele frequencies of the XbaI and VNTR polymorphisms but not of the signal peptide. There were no significant differences in allele frequencies between cases and controls. Adjusted for age, gender and region, the lipoprotein concentrations differed significantly with genotype. The XbaI polymorphism was associated with differences in plasma cholesterol (P = 0.007), triglyceride (P = 0.050), apo B (P = 0.001) and LDL cholesterol (P = 0.01). An interaction between XbaI genotype and body mass index was observed on plasma triglyceride (P = 0.015) and apo B (P = 0.005) concentrations. The signal peptide deletion allele was associated with increased plasma cholesterol (P = 0.03), apo B (P = 0.04) and LDL cholesterol (P = 0.02). The VNTR was not significantly associated with any of these variables although there was a significant genotype/status interaction in relation to HDL cholesterol (P = 0.001) and apo AI (P = 0.001) concentrations. We conclude that, although they are associated with significant differences in lipoprotein concentrations within- and between-populations, the apo B DNA polymorphisms studied are of less value as indicators of cardiovascular risk-factor status in the offspring of individuals affected by the disease.

The effect of variation in the apolipoprotein B gene on plasmid lipid and apolipoprotein B levels. I. A likelihood-based approach to cladistic analysis

A new method is described for employing family data to test for significant haplotype effects on continuously distributed variables, using likelihood-ratio tests of linear models in which haplotype effects are parameterized and familial correlations taken into account. The method is applied to the apolipoprotein B (Apo B) gene, using 5 polymorphisms (Insertion/deletion, Bsp1286I, XbaI, MspI, EcoRI) to define haplotypes in 121 French nuclear families. Eleven haplotypes were found, five of which, combined, account for over 95% of the sample. A haplotype phylogeny is proposed, and is used to define a nested set of models for testing the effects of Apo B variation on total-, low-density-lipoprotein (LDL)-, and high-density-lipoprotein (HDL)-cholesterol, triglyceride, and Apo B levels. Apo B haplotype effects account for about 10% of the genetic variance and 5% of the total variance in HDL-cholesterol and triglyceride levels. Clusters of evolutionarily-related haplotypes with similar phenotypic effects are identified for HDL-cholesterol and triglycerides. Single haplotypes with statistically significant effects are identified for cholesterol, LDL-cholesterol, and Apo B levels.

The ins/del polymorphism in the signal sequence of apolipoprotein B has no effect on lipid parameters

The 'ins/del' polymorphism in the signal sequence of apolipoprotein B alters the hydrophobicity of the signal sequence and therefore would be expected to affect the rate of production of apolipoprotein B (apo B) and the plasma concentrations of lipoproteins containing this apolipoprotein. We sought evidence for an association with plasma lipid levels and this polymorphism in two studies, one using a normal randomly selected population (N = 188) and another using a mildly hypercholesterolaemic group of men aged 45-64 (N = 360). The frequency of the rarer, 'del' allele, was the same in both groups. Likewise no differences in serum cholesterol, serum triglycerides, very low density lipoprotein, low density lipoprotein or high density lipoprotein were seen comparing homozygotes for the signal sequence allele within either group.

Genetic variants of apolipoprotein B: relation to serum lipid levels and coronary artery disease among the Finns

The genetic variation of apolipoprotein B has been studied extensively in Finns with the aid of protein and DNA polymorphisms. Population association studies confirmed significant associations between the XbaI polymorphism of the apolipoprotein B gene and elevated serum cholesterol levels, and dietary studies suggested that the XbaI and ins/del polymorphisms might modify the serum lipid response to dietary fat intake. Studies comparing patients and controls, however, did not confirm previous studies suggesting that the multi-allelic variation at the 3'VNTR region of the apolipoprotein B gene was associated with coronary artery disease. The results suggest that the apolipoprotein B gene is involved in the regulation of serum lipid levels. A yet unknown mutation in linkage disequilibrium with the XbaI site may contribute to this regulation.