Apolipoprotein B gene 3'VNTR polymorphism: association with plasma lipids and coronary heart disease in Han Chinese

BACKGROUND

Studies that considered polymorphisms within the apolipoprotein B (APOB) gene as risk factors for coronary heart disease (CHD) have reported conflicting results.

METHODS

The phenotypic effects of the 3'VNTR polymorphism of the APOB gene on the susceptibility to CHD were investigated in 120 unrelated healthy individuals and 137 CHD patients. The internal structure of APOB gene 3'VNTR alleles was also analyzed by the methods of SspI restriction mapping and DNA sequencing of the allele fragments.

RESULTS

In total, 14 segregating alleles and 32 genotypes of APOB gene 3'VNTR were characterized in the pooled total of 257 subjects. The frequency of 3'VNTR-B alleles [hypervariable element (HVE) > or =38)] in the CHD cases was higher than that of the controls (10.95% vs. 5.00%, p<0.05). 3'VNTR-B allele was dependently related to total cholesterol levels (p<0.05). Compared with SS homozygotes, 3'VNTR-B allele carriers were associated with an increased risk of CHD (OR=2.137, 95% CI=1.055-4.328, p=0.0349). No significant differences in the internal structure and sequences of APOB gene 3'VNTR alleles were found between cases and controls.

CONCLUSIONS

APOB gene 3'VNTR polymorphism exerts an impact on lipid metabolism and may contribute to the susceptibility to the development of CHD in Han Chinese.

Analysis of the apolipoprotein B gene 3' hypervariable region among nationals of the Abu Dhabi Emirate and comparisons with other populations

BACKGROUND

Among all the polymorphic markers available to date, a hypervariable region located in the 3' of the human apolipoprotein B gene has been extensively studied in global populations throughout the world.

PATIENTS AND METHODS

Using a polymerase chain reaction-based assay, we investigated the allele and genotype frequency distributions of the alleles (corresponding to repeats of a 30 base-pair core DNA sequence) of this hypervariable region in a group of 367 unrelated nationals (201 males, 166 females) from the United Arab Emirates.

RESULTS

We found 18 different alleles, ranging from 21 to 55 repeats, making up 51 genotypes that occurred in Hardy-Weinberg proportions and were associated with a heterozygosity index of 80.9%. The allele frequency distribution was different from that of other populations in that it was trimodal, with peaks at 31, 37 and 47 repeats, with corresponding relative frequencies of 16.1%, 25.1% and 6.0%. A four-allele model, which allowed comparisons with other reports, revealed distribution differences with all other ethnic groups except South Asians and Serbs.

CONCLUSION

This marker is very informative for the Emirati population, and will be very useful for UAE-specific DNA fingerprinting. It will also be a valuable tool for assessing the role of apolipoprotein B in cardiovascular diseases.

Association of an apolipoprotein B gene marker with essential hypertension

We designed an association (retrospective, case control) study aimed at evaluating associations between genetic variations of the human apolipoprotein B (apoB) gene and clinical diagnosis of essential hypertension. Our approach was to compare the distribution of the alleles of a highly polymorphic variable number of tandem repeats localized 3' to the human apoB gene, the apoB 3' hypervariable region (HVR), in a group of normotensive and a group of hypertensive individuals. We collected DNA samples from 437 unrelated nationals (215 normotensives and 222 hypertensives) from the United Arab Emirates (UAEs), and we determined their apoB 3' HVR allele and genotype status with a polymerase chain reaction-based assay. In the UAE population, we found 18 alleles underlying a total of 51 genotypes. The distribution of these alleles was significantly different between normotensive and hypertensive UAE nationals. The main peak of the distributions occurred at 35 repeats among hypertensives (with a relative frequency of 25.7% versus 19.6% in normotensives) and at 37 repeats among normotensives (28.8% versus 20.3% in hypertensives). Alleles with 21, 23, 25, 49, and 55 repeats were found in hypertensives only (with a combined relative frequency of 7.6%). We conclude that variations of the apoB gene, or of a nearby gene, that may be in linkage disequilibrium with these alleles play a role in the development of essential hypertension in the UAEs.