Candidate gene polymorphism in cardiovascular disease: the BIP cohort.

BACKGROUND: Cardiovascular disease is now well established as a multifactorial disease. In a given individual, the level of cardiovascular risk is due to the interaction between genetic and environmental components. The BIP cohort comprises 3000 patients with cardiovascular disease who were tested for the benefits of bezafibrate treatment. This cohort has the data for the lipid profile of each individual, fibrinogen, insulin, as well as clinical, demographic and lifestyle parameters. OBJECTIVES: To genotype up to 64 variable sites in 36 genes in the BIP cohort. The genes tested in this assay are involved in pathways implicated in the development and progression of atherosclerotic plaques, lipid and homocystein metabolism, blood pressure regulation, thrombosis, rennin-angiotensin system, platelet aggregation, and leukocyte adhesion. METHODS: DNA was extracted from 1000 Israeli patients from the BIP cohort. A multilocus assay, developed by the Roche Molecular System, was used for genotyping. Allele frequencies for some of the markers were compared to the published frequencies in a healthy population (the French Stanislas cohort, n = 1480). RESULTS: Among the 26 comparable alleles checked in the two cohorts, 16 allele frequencies were significantly different from the healthy French population: ApoE(E3, E2, E4), ApoB (71ile), ApoC (3482T, 455C, 1100T, 3175G, 3206G), CETP(405val), ACE (Del), AGT (235thr), ELAM (128arg); P < 0001 and LPL (93G, 291Ser, 447ter); P < 005. CONCLUSIONS: Although a comparable healthy Israeli population study is needed for more precise interpretation of these results, frequency differences in these polymorphic alleles--associated with lipid metabolism, renin-angiotensin system and leukocyte adhesion mechanism--between CVD patients and healthy individuals nevertheless implicate these candidate genes as predisposing for CVD.

Are common disease susceptibility alleles the same in outbred and founder populations?

Founder populations have been the subjects of complex disease studies because of their decreased genetic heterogeneity, increased linkage disequilibrium and more homogeneous environmental exposures. However, it is possible that disease alleles identified in founder populations may not contribute significantly to susceptibility in outbred populations. In this study we examine the Hutterites, a founder population of European descent, for 103 polymorphisms in 66 genes that are candidates for cardiovascular or inflammatory diseases. We compare the frequencies of alleles at these loci in the Hutterites to their frequencies in outbred European-American populations and test for associations with cardiovascular disease-associated phenotypes in the Hutterites. We show that alleles at these loci are found at similar frequencies in the Hutterites and in outbred populations. In addition, we report associations between 39 alleles or haplotypes and cardiovascular disease phenotypes (P<0.05), with five loci remaining significant after adjusting for multiple comparisons. These data indicate that this founder population is informative and offers considerable advantages for genetic studies of common complex diseases.

ApoC-III gene polymorphisms and risk of coronary artery disease.

Several polymorphisms in the apolipoprotein C-III (apoC-III) gene have been associated with hypertriglyceridemia, but the link with coronary artery disease risk is still controversial. In particular, apoC-III promoter sequence variants in the insulin responsive element (IRE), constitutively resistant to downregulation by insulin, have never been investigated in this connection. We studied a total of 800 patients, 549 of whom had angiographically documented coronary atherosclerosis, whereas 251 had normal coronary arteriograms. We measured plasma lipids, insulin, apoA-I, apoB, and apoC-III and assessed three polymorphisms in the apoC-III gene, namely, T-455C in the IRE promoter region, C1100T in exon 3, and Sst1 polymorphic site (S1/S2) in the 3' untranslated region. Each variant influenced triglyceride levels, but only the T-455C (in homozygosity) and S2 alleles influenced apoC-III levels. In coronary artery disease (CAD) patients, 18.6% were homozygous for the -455C variant compared with only 9.2% in CAD-free group (P < 0.001). In logistic regression models, homozygosity for -455C variant was associated with a significantly increased risk of CAD (OR = 2.5 and 2.18 for unadjusted and adjusted models, respectively) suggesting that it represents an independent genetic susceptibility factor for CAD.

A common promoter polymorphism in the hepatic lipase gene (LIPC-480C>T) is associated with an increase in coronary calcification in type 1 diabetes.

Type 1 diabetes is associated with coronary heart disease (CHD) and coronary artery calcification (CAC), a measure of subclinical CHD. The hepatic lipase gene promoter polymorphism (LIPC-480C>T) is a common variant affecting lipid metabolism. This study examined the relation between the LIPC-480C>T and CAC in type 1 diabetes. In the type 1 diabetic patients studied, 56% had CAC >0 Agatston units (AU). These subjects had a longer duration of diabetes (26.2 +/- 1.3 vs. 17.8 +/- 1.4 years; P < 0.001), lower HDL cholesterol levels (55.7 +/- 2.4 vs. 61.0 +/- 2.5 mg/dl; P = 0.05), higher triglyceride levels (101 +/- 17.3 vs. 66 +/- 7.6 mg/dl; P < 0.05), and higher diastolic blood pressure (79.7 +/- 1.0 vs. 76.0 +/- 1.4 mmHg; P < 0.05). The LIPC-480 T allele was more common in subjects with CAC (frequency = 0.31 +/- 0.05 vs. 0.14 +/- 0.04; P = 0.006). The proportion with CAC was 44% in LIPC-480CC subjects, 71% in heterozygotes, and 83% in LIPC-480TT subjects (P < 0.01). LIPC-480 T allele frequency increased as the amount of CAC increased (P = 0.007). LIPC-480 genotype was independently associated with the CAC (odds ratio = 2.90, 95% CI 1.22-6.92, P < 0.05) after adjusting for duration of diabetes, age, sex, diastolic blood pressure, HDL cholesterol, and triglyceride levels. In conclusion, the LIPC-480C>T polymorphism was associated with subclinical CHD in type 1 diabetes. This genetic variant may identify subjects in which early intervention to prevent CHD may be appropriate.