Complex genetics of monogenic familial hypercholesterolemia

Heterozygous familial hypercholesterolemia (FH) is an inherited disorder of lipid metabolism, leading to severely elevated low-density lipoprotein-cholesterol levels and an increased risk of cardiovascular disease (CVD). Despite the monogenic cause of FH, CVD susceptibility varies considerably. Traditional risk factors, a specific low-density lipoprotein receptor mutation and modifier genes have been suggested to influence susceptibility to CVD. With the completion of the Human Genome Project and the availability of high throughput molecular methods, we expect that the creation of a genetic fingerprint of CVD risk in FH is feasible in the coming years. The challenge remains to link genetic data and clinical information to refine individualized approaches to CVD care in FH patient

Usefulness of Genetic Polymorphisms and Conventional Risk Factors to Predict Coronary Heart Disease in Patients With Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is an autosomal dominant disorder with an associated high risk of coronary heart disease (CHD). The considerable variation in age of onset of CHD in patients with FH is believed to arise from conventional risk factors, as well as genetic variation other than in the low-density lipoprotein receptor gene. The degree to which currently known genetic variants can improve the prediction of CHD risk beyond conventional risk factors in this disorder was investigated. Fourteen genetic variants recently identified for association with CHD in a Dutch FH population were considered. Prediction models were constructed using Cox proportional hazards models, and predictive value was assessed using a Concordance statistic (c statistic). A total of 1,337 patients with FH were completely genotyped for all genetic variants. Hazard ratios of the genetic variants ranged from 0.61 to 0.74 and 1.24 to 2.33. The c statistic of the CHD prediction model based on genetic variants was 0.59, denoting little discrimination. The model based on conventional risk factors had a c statistic of 0.75, denoting moderate discrimination. Adding genetic test results to this model increased the c statistic to 0.76. In conclusion, the contribution of 14 genetic variants to the prediction of CHD risk in patients with FH was limited. To improve genome-based prediction of CHD, larger numbers of genetic variants need to be identified that either on their own or in gene-gene interaction have substantial effects on CHD risk. (C) 2009 Elsevier Inc. (Am J Cardiol 2009;103:375-380

Genome-Based Prediction of Breast Cancer Risk in the General Population: A Modeling Study Based on Meta-Analyses of Genetic Associations

Background: Genome-wide association studies identified novel breast cancer susceptibility variants that could be used to predict breast cancer in asymptomatic women. This review and modeling study aimed to investigate the current and potential predictive performance of genetic risk models. Methods: Genotypes and disease status were simulated for a population of 10,000 women. Genetic risk models were constructed from polymorphisms from meta-analysis including, in separate scenarios, all polymorphisms or statistically significant polymorphisms only. We additionally investigated the magnitude of the odds ratios (OR) for 1 to 100 hypothetical polymorphisms that would be needed to achieve similar discriminative accuracy as available prediction models [modeled range of area under the receiver operating characteristic curve (AUC) 0.70-0.80]. Results: Of the 96 polymorphisms that had been investigated in meta-analyses, 41 showed significant associations. AUC was 0.68 for the genetic risk model based on all 96 polymorphisms and 0.67 for the 41 significant polymorphisms. Addition of 50 additional variants, each with risk allele frequencies of 0.30, requires per-allele ORs of 1.2 to increase this AUC to 0.70, 1.3 to increase AUC to 0.75, and 1.5 to increase AUC to 0.80. To achieve AUC of 0.80, even 100 additional variants would need per-allele ORs of 1.3 to 1.7, depending on risk allele frequencies. Conclusion: The predictive ability of genetic risk models in breast cancer has the potential to become comparable to that of current breast cancer risk models. Impact: Risk prediction based on low susceptibility variants becomes a realistic tool in prevention of nonfamilial breast cancer. Cancer Epidemiol Biomarkers Prev; 20(1); 9-22. (C) 2011 AACR

Two Common Haplotypes of the Glucocorticoid Receptor Gene Are Associated with Increased Susceptibility to Cardiovascular Disease in Men with Familial Hypercholesterolemia

Context: Glucocorticoids contribute to the development of atherosclerosis. Four polymorphisms in the glucocorticoid receptor (GR) gene have been reported to alter glucocorticoid sensitivity and have been associated with cardiovascular risk factors. Studies on the relationship between these GR variants and cardiovascular disease (CVD) risk, however, have yielded conflicting results. Objective: We sought to determine whether haplotypes based on functional polymorphisms in the GR gene influenced susceptibility to CVD in a high-risk population. Design, Setting, and Participants: In a multicenter cohort study, 1830 patients with heterozygous familial hypercholesterolemia were genotyped for the functional ER22/23EK, N363S, BclI, and 9 beta variants. We analyzed the combined effect of all GR variants by constructing haplotypes and using a Cox proportional hazards regression model with adjustment for year of birth and smoking. The analyses were stratified for sex. Main Outcome Measures: The primary outcome measure was CVD defined as coronary, cerebral, and peripheral artery disease. Results: A total of 359 men (40.8%) and 224 women (23.6%) had a cardiovascular event. In men, the BclI haplotype was associated with a 34% higher CVD risk (confidence interval 1.02-1.76; P = 0.03) and the 9 beta haplotype with a 41% higher CVD risk (confidence interval 1.02-1.94; P = 0.04). In women, none of the GR haplotypes was significantly related with CVD. We did not find differences in cardiovascular risk factors between GR haplotypes. Conclusions: In this large cohort of high-risk individuals, two common haplotypes in the GR gene modified CVD susceptibility among men. (J Clin Endocrinol Metab 93: 4902-4908, 2008

Haplotype of the angiotensinogen gene is associated with coronary heart disease in familial hypercholesterolemia

OBJECTIVE: Familial hypercholesterolemia is characterized by high plasma low-density lipoprotein cholesterol levels and premature coronary heart disease. Despite the monogenetic origin of familial hypercholesterolemia, the incidence of coronary heart disease varies considerably among patients, which is only partly explained by classical risk factors. Hypertension is an important risk factor for coronary heart disease that is associated with angiotensinogen levels. Therefore, we analyzed the angiotensinogen gene as a modifier gene for coronary heart disease risk in patients with familial hypercholesterolemia. METHODS: In a cohort of 1785 familial hypercholesterolemia patients, we reconstructed five frequent haplotypes of the angiotensinogen gene, based on four polymorphisms. The five haplotypes cover approximately 98% of the genetic diversity accounted for by these four polymorphisms. The associations between the haplotypes and coronary heart disease were analyzed with the haplo.stats program, adjusted for age, sex and smoking. RESULTS: Patients homozygous for the C allele of the 4072 T>C polymorphism had a 34% increased coronary heart disease risk (P = 0.017) compared to patients homozygous for the T allele. Haplotype H3, consisting of the minor allele of the 4072T>C polymorphism and the major alleles of the other polymorphisms, had a frequency of 15% and was associated with a 45% increased coronary heart disease risk (P = 0.006) compared to the wild-type haplotype H1. CONCLUSIONS: We conclude that genetic variation in the angiotensinogen gene contributes to coronary heart disease risk in patients with familial hypercholesterolemi

Arachidonate 5-lipoxygenase-activating protein (ALOX5AP) gene and coronary heart disease risk in familial hypercholesterolemia

Objectives: To investigate the arachionate 5-lipoxygenase-activating protein (ALOX5AP) gene as a potential modifier gene for coronary heart disease (CHD) in patients with familial hypercholesterolemia (FH). Background: The ALOX5AP gene is required for the synthesis of leukotrienes, a protein family involved in inflammatory responses. Recently, genetic variation in this gene was shown to be associated with myocardial infarction in an Icelandic and British population. Since FH is characterized by severely increased levels of plasma low-density lipoprotein (LDL) cholesterol levels, chronic inflammation of the arterial wall, and subsequent premature CHID, the ALOX5AP gene could be an important modifier gene for CHD in FH. Methods: In a cohort of 1817 FH patients, we reconstructed two four-marker haplotypes, previously defined in Icelandic (HapA) and British (HapB) individuals. The haplotypes were inferred with PHASE and the associations between the haplotypes and CHD were analyzed with a Cox proportional hazards model, adjusted for year of birth, sex, and smoking. Results: HapB had a frequency of 6.9% and 8.2% in the group without and with CHD, respectively, conferring a hazard ratio of 1.48 (95% CI 1.17-1.89, p = 0.001). This association was predominantly found in patients with LDL cholesterol levels above the median (HR 1.82, 95% CI 1.20-2.76, p = 0.005). HapA was not associated with CHID. Conclusion: We conclude that genetic variation in the ALOX5AP gene contributes to CHD risk in patients with FH. Our findings emphasize the important role of inflammation in the pathogenesis of early CHD in this disorder, particularly in patients with more severely raised LDL cholesterol levels. (C) 2008 Elsevier Ireland Ltd. All rights reserved