NHLBI Family Heart Study Research Articles

Response to Letter Regarding Article, “Human C-Reactive Protein Does Not Promote Atherosclerosis in Transgenic Rabbits”

HomeCirculationVol. 122, No. 4Response to Letter Regarding Article, “Human C-Reactive Protein Does Not Promote Atherosclerosis in Transgenic Rabbits” Free AccessLetterPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessLetterPDF/EPUBResponse to Letter Regarding Article, “Human C-Reactive Protein Does Not Promote Atherosclerosis in Transgenic Rabbits” Tomonari Koike, Ying Yu, Jifeng Zhang and Jianglin Fan Yukio Ozaki Shuji Kitajima and Kazutoshi Nishijima Masatoshi Morimoto Teruo Watanabe Sucharit Bhakdi Yujiro Asada Y. Eugene Chen Tomonari KoikeTomonari Koike Department of Molecular Pathology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan Search for more papers by this author , Ying YuYing Yu Department of Molecular Pathology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan Search for more papers by this author , Jifeng ZhangJifeng Zhang Department of Molecular Pathology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan Search for more papers by this author and Jianglin FanJianglin Fan Department of Molecular Pathology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan Search for more papers by this author Yukio OzakiYukio Ozaki Department of Clinical and Laboratory Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan Search for more papers by this author Shuji KitajimaShuji Kitajima Analytical Research Center for Experimental Sciences, Saga University, Saga, Japan Search for more papers by this author and Kazutoshi NishijimaKazutoshi Nishijima Analytical Research Center for Experimental Sciences, Saga University, Saga, Japan Search for more papers by this author Masatoshi MorimotoMasatoshi Morimoto Department of Rehabilitation, Kumamoto Health Science University, Kumamoto, Japan Search for more papers by this author Teruo WatanabeTeruo Watanabe Fukuoka Wajiro Hospital, Fukuoka, Japan Search for more papers by this author Sucharit BhakdiSucharit Bhakdi Institute of Medical Microbiology and Hygiene, Mainz, Germany Search for more papers by this author Yujiro AsadaYujiro Asada The First Department of Pathology, Faculty of Medicine, Miyazaki University, Miyazaki, Japan Search for more papers by this author Y. Eugene ChenY. Eugene Chen Cardiovascular Center, Department of Internal Medicine, University of Michigan, Ann Arbor, Mich Search for more papers by this author Originally published27 Jul 2010https://doi.org/10.1161/CIRCULATIONAHA.110.951798Circulation. 2010;122:e407We appreciate the comments by Nakajima and Saito on our recent article published in Circulation.1 The major question they raised was why human C-reactive protein (CRP) transgenic rabbits failed to exhibit other metabolic disorders, because emerging data support that CRP levels are elevated in patients with metabolic syndrome.2 It is well documented that elevated plasma CRP levels are associated with many pathological states such as cardiovascular diseases and metabolic syndrome; however, these associations do not necessarily mean that high levels of CRP can cause these diseases. Indeed, population genetics studies have failed to link CRP single-nucleotide polymorphisms to the increased risk of cardiovascular diseases, although CRP single-nucleotide polymorphisms are associated with marked increases in CRP levels.3,4 Also, there is no evidence to date to show that elevation of plasma CRP alone can lead to metabolic syndrome both clinically and experimentally. It is apparent that further experiments with appropriate large-animal models are required to investigate CRP functions in metabolic syndrome. Because metabolic syndrome is composed of several metabolic disorders (eg, hypertension, dyslipidemia, and hyperglycemia), which are mediated by multiple genes and many environmental factors, it is unlikely that overexpression of a single CRP gene in animals can lead to all these abnormalities. In fact, we have recently transgenically expressed human CRP in hypertensive animals and found that in the setting of hypertension, CRP does exert certain detrimental effects on both lipid and glucose metabolism (unpublished data). Taken together, CRP functions in both physiology and pathophysiology remain to be further elucidated with genetically modified large animals, as we reported in the study.1DisclosuresNone. References 1 Koike T, Kitajima S, Yu Y, Nishijima K, Zhang J, Ozaki Y, Morimoto M, Watanabe T, Bhakdi S, Asada Y, Chen YE, Fan J. Human C-reactive protein does not promote atherosclerosis in transgenic rabbits. Circulation. 2009; 120: 2088–2094.LinkGoogle Scholar2 Ridker PM, Buring JE, Cook NR, Rifai N. C-reactive protein, the metabolic syndrome, and risk of incident cardiovascular events: an 8-year follow-up of 14 719 initially healthy American women. Circulation. 2003; 107: 391–397.LinkGoogle Scholar3 Wang Q, Hunt SC, Xu Q, Chen YE, Province MA, Eckfeldt JH, Pankow JS, Song Q. Association study of CRP gene polymorphisms with serum CRP level and cardiovascular risk in the NHLBI Family Heart Study. Am J Physiol Heart Circ Physiol. 2006; 291: H2752–H2757.CrossrefMedlineGoogle Scholar4 Zacho J, Tybjaerg-Hansen A, Jensen JS, Grande P, Sillesen H, Nordestgaard BG. Genetically elevated C-reactive protein and ischemic vascular disease. N Engl J Med. 2008; 359: 1897–1908.CrossrefMedlineGoogle Scholar Previous Back to top Next FiguresReferencesRelatedDetails July 27, 2010Vol 122, Issue 4 Advertisement Article InformationMetrics https://doi.org/10.1161/CIRCULATIONAHA.110.951798 Originally publishedJuly 27, 2010 PDF download Advertisement SubjectsAnimal Models of Human DiseaseEpidemiologyMechanismsPathophysiology

Chocolate consumption is inversely associated with calcified atherosclerotic plaque in the coronary arteries: The NHLBI Family Heart Study

While a diet rich in anti-oxidant has been favorably associated with coronary disease and hypertension, limited data have evaluated the influence of such diet on subclinical disease. Thus, we sought to examine whether chocolate consumption is associated with calcified atherosclerotic plaque in the coronary arteries (CAC). In a cross-sectional design, we studied 2217 participants of the NHLBI Family Heart Study. Chocolate consumption was assessed by a semi-quantitative food frequency questionnaire and CAC was measured by cardiac CT. We defined prevalent CAC using an Agatston score of at least 100 and fitted generalized estimating equations to calculate prevalence odds ratios of CAC. There was an inverse association between frequency of chocolate consumption and prevalent CAC. Odds ratios (95% CI) for CAC were 1.0 (reference), 0.94 (0.66-1.35), 0.78 (0.53-1.13), and 0.68 (0.48-0.97) for chocolate consumption of 0, 1-3 times per month, once per week, and 2+ times per week, respectively (p for trend 0.022), adjusting for age, sex, energy intake, waist-hip ratio, education, smoking, alcohol consumption, ratio of total-to-HDL-cholesterol, non-chocolate candy, and diabetes mellitus. Controlling for additional confounders did not alter the findings. Exclusion of subjects with coronary heart disease or diabetes mellitus did not materially change the odds ratio estimates but did modestly decrease the overall significance (p=0.07). These data suggest that chocolate consumption might be inversely associated with prevalent CAC.

Polymorphisms near EXOC4 and LRGUK on chromosome 7q32 are associated with Type 2 Diabetes and fasting glucose; The NHLBI Family Heart Study

BackgroundThe chromosome 7q32 region is linked to metabolic syndrome and obesity related traits in the Family Heart Study. As part of a fine mapping study of the region, we evaluated the relationship of polymorphisms to fasting glucose levels and Type 2 diabetes.MethodsThirty-nine HapMap defined tag SNPs in a 1.08 Mb region and a novel deletion polymorphism were genotyped in 2,603 participants of the NHLBI Family Heart Study (FHS). Regression modeling, adjusting for BMI, age, sex, smoking and the TCF7L2 polymorphism, was used to evaluate the association of these polymorphisms with T2D and fasting glucoses levels.ResultsThe deletion polymorphism confers a protective effect for T2D, with homozygous deletion carriers having a 53% reduced risk compared to non-deleted carriers. Among non-diabetics, the deletion was significantly associated with lower fasting glucose levels in men (p = 0.038) but not women (p = 0.118). In addition, seven SNPs near the deletion were significantly associated (p < 0.01) to diabetes.ConclusionChromosome 7q32 contains both SNPs and a deletion that were associated to T2D. Although the deletion region contains several islands of strongly conserved sequence, it is not known to contain a transcribed gene. The closest nearby gene, EXOC4, is involved in insulin-stimulated glucose transport and may be a candidate for this association. Further work is needed to determine if the deletion represents a functional variant or may be in linkage disequilibrium with a functional mutation influencing EXOC4 or another nearby gene.

NYD-SP18 is associated with obesity in the NHLBI Family Heart Study

The NHLBI Family Heart Study (FHS) genome-wide linkage scan identified a region of chromosome 7q with a logarithm of odds score of 4.9 for body mass index (BMI). We report the results of fine mapping the linkage peak using 1020 single nucleotide polymorphisms (SNPs) to test for association to obesity in families exhibiting linkage to chromosome 7. Association observed in linked families (284 obese cases/381 controls) was examined in an independent set of unrelated FHS participants (172 obese cases/308 controls) to validate the observed association. Two dichotomous obesity phenotypes were studied based on clinical BMI cutoffs and the sex-specific distribution of both BMI and leptin levels. Using a P-value of 0.01 as criteria for association in the linked families, a P-value of 0.05 as criteria for association in the unrelated sample, and requiring consistency in the direction of the effect of the minor allele between the two samples, we identified two coding SNPs in the NYD-SP18 gene with minor alleles increasing the risk of obesity. Adjustment for exercise, smoking and FTO genotype did not influence the result in linked families, but improved the result in the unrelated sample. Carrying a minor allele of the nonsynonymous SNP rs6971091 conferred an odds ratio of at least 2 for obesity defined by both BMI and leptin levels. The effect of the NYD-SP18 SNP on obesity was larger than the effect of FTO in FHS families. Publicly available results from genome-wide association studies support the association between NYD-SP18 and BMI. The NYD-SP18 gene is described as testes development related, but little is known about the gene's function or the mechanism by which it may influence risk for obesity.

Offspring's leukocyte telomere length, paternal age, and telomere elongation in sperm.

Leukocyte telomere length (LTL) is a complex genetic trait. It shortens with age and is associated with a host of aging-related disorders. Recent studies have observed that offspring of older fathers have longer LTLs. We explored the relation between paternal age and offspring's LTLs in 4 different cohorts. Moreover, we examined the potential cause of the paternal age on offspring's LTL by delineating telomere parameters in sperm donors. We measured LTL by Southern blots in Caucasian men and women (n=3365), aged 18–94 years, from the Offspring of the Framingham Heart Study (Framingham Offspring), the NHLBI Family Heart Study (NHLBI-Heart), the Longitudinal Study of Aging Danish Twins (Danish Twins), and the UK Adult Twin Registry (UK Twins). Using Southern blots, Q-FISH, and flow-FISH, we also measured telomere parameters in sperm from 46 young (<30 years) and older (>50 years) donors. Paternal age had an independent effect, expressed by a longer LTL in males of the Framingham Offspring and Danish Twins, males and females of the NHLBI-Heart, and females of UK Twins. For every additional year of paternal age, LTL in offspring increased at a magnitude ranging from half to more than twice of the annual attrition in LTL with age. Moreover, sperm telomere length analyses were compatible with the emergence in older men of a subset of sperm with elongated telomeres. Paternal age exerts a considerable effect on the offspring's LTL, a phenomenon which might relate to telomere elongation in sperm from older men. The implications of this effect deserve detailed study.

Genome‐wide admixture mapping for coronary artery calcification in African Americans: the NHLBI Family Heart Study

Coronary artery calcification (CAC) is an important measure of subclinical coronary atherosclerosis and an independent predictor of coronary heart disease. To identify the genetic loci contributing to CAC, we conducted a genome-wide scan with 374 microsatellite markers by applying admixture mapping to 618 African American participants in the US National Heart, Lung, and Blood Institute Family Heart Study, in which 868 European American participants from family heart study and 157 Africans genotyped by the Marshfield Medical Genetics Center were used as the two reference founding populations for the African Americans, and a computer program based on a Markov Chain Monte Carlo algorithm, STRUCTURE 2.1, was used to estimate European and African ancestries among African Americans. A permutation test for random repeated sampling regression of CAC score on marker specific African ancestry found 22 markers statistically significant at the 0.05 level and four markers, D10S189 at 10p14, D20S159 at 20q13, D12S1294 at 12q14, and D6S1053 at 6q12, significant at the 0.01 level. D10S189 and D6S1053 were further confirmed at the 0.05 significance level by regression of CAC on allelic copy number, in which individual ancestry was used as a genetic background covariate to control possible stratification in African Americans. On the basis of the results from this and other independent studies, the location of D6S1053 at 80cM on chromosome 6 (6q12) seems to harbor a highly promising quantitative trait loci for atherosclerosis.

Circulating soluble ICAM-1 levels shows linkage to ICAM gene cluster region on chromosome 19: The NHLBI Family Heart Study follow-up examination

Atherogenesis is a chronic inflammatory process in which intercellular adhesion molecule 1 (ICAM-1) plays a critical role. Circulating soluble ICAM-1 (sICAM-1) is thought to be the result of cleavage of membrane-bound ICAM-1 and its concentration in serum/plasma has been shown to be heritable. Genome-wide linkage scans were conducted for quantitative trait loci influencing sICAM-1. Phenotype and genetic marker data were available for 2617 white and 531 black individuals in the NHLBI Family Heart Study follow-up examination. Heritability for sICAM-1 was 0.39 in whites and 0.59 in blacks. Significant linkage was observed on chromosome 19 (LOD = 4.0 at 14 cM) in whites near the ICAM gene cluster that includes the structural gene for ICAM-1. The T-allele of ICAM-1 SNP rs5491 has been strongly associated with the specific sICAM-1 assay we used in our study. Through additional genotyping we were able to rule out rs5491 as the cause of the linkage finding. This study provides preliminary evidence linking genetic variation in the ICAM1 structural gene to circulating sICAM-1 levels.

Association of sICAM-1 and MCP-1 with coronary artery calcification in families enriched for coronary heart disease or hypertension: the NHLBI Family Heart Study

Association of sICAM-1 and MCP-1 with coronary artery calcification in families enriched for coronary heart disease or hypertension: the NHLBI Family Heart Study

Association of sICAM-1 and MCP-1 with coronary artery calcification in families enriched for coronary heart disease or hypertension: the NHLBI Family Heart Study

BackgroundData accumulated from mouse studies and in vitro studies of human arteries support the notion that soluble intercellular adhesion molecule-1 (sICAM-1) and monocyte chemoattractant protein-1 (MCP-1) play important roles in the inflammation process involved in atherosclerosis. However, at the population level, the utility of sICAM-1 and MCP-1 as biomarkers for subclinical atherosclerosis is less clear. In the follow-up exam of the NHLBI Family Heart Study, we evaluated whether plasma levels of sICAM-1 and MCP-1 were associated with coronary artery calcification (CAC), a measure of the burden of coronary atherosclerosis.MethodsCAC was measured using the Agatston score with multidetector computed tomography. Information on CAC and MCP-1 was obtained in 2246 whites and 470 African Americans (mean age 55 years) without a history of coronary heart disease (CHD). Information on sICAM-1 was obtained for white participants only.ResultsIn whites, after adjustment for age and gender, the odds ratios (ORs) of CAC (CAC > 0) associated with the second, third, fourth, and fifth quintiles of sICAM-1 compared to the first quintile were 1.22 (95% confidence interval [CI]: 0.91–1.63), 1.15 (0.84–1.58), 1.49 (1.09–2.05), and 1.72 (1.26–2.36) (p = 0.0005 for trend test), respectively. The corresponding ORs for the second to fifth quintiles of MCP-1 were 1.26 (0.92–1.73), 0.99 (0.73–1.34), 1.42 (1.03–1.96), and 2.00 (1.43–2.79) (p < 0.0001 for trend test), respectively. In multivariable analysis that additionally adjusted for other CHD risk factors, the association of CAC with sICAM-1 and MCP-1 was attenuated and no longer statistically significant. In African Americans, the age and gender-adjusted ORs of CAC associated with the second and third tertiles of MCP-1 compared to the first tertile were 1.16 (0.64–2.08) and 1.25 (0.70–2.23) (p = 0.44 for trend test), respectively. This result did not change materially after additional adjustment for other CHD risk factors. Test of race interaction showed that the magnitude of association between MCP-1 and CAC did not differ significantly between African Americans and whites. Similar results were obtained when CAC ≥ 10 was analyzed as an outcome for both MCP-1 and sICAM-1.ConclusionThis study suggests that sICAM-1 and MCP-1 are biomarkers of coronary atherosclerotic burden and their association with CAC was mainly driven by established CHD risk factors.

Circulating MCP-1 levels shows linkage to chemokine receptor gene cluster on chromosome 3: the NHLBI family heart study follow-up examination.

Atherogenesis is a chronic inflammatory process. Critical in the inflammation process is monocyte chemoattractant protein-1 (MCP-1). To locate genomic regions that affect circulating MCP-1 levels, a genome-wide linkage scan was conducted in a sample of whites and blacks. Phenotype and genetic marker data were available for 2501 white and 513 black participants in the National Heart Lung Blood Institute Family Heart Study follow-up examination. Heritability for MCP-1 was 0.37 in whites and 0.47 in blacks after adjusting for the effects of sex, age, age-sex interaction, smoking status, lifetime smoking exposure (pack-years) and field center. Significant linkage was observed for MCP-1 in a combined black and white sample on chromosome 3 (logarithm of the odds ratio (LOD)=3.5 at 78 cM, P=0.0001) and suggestive linkage was observed in whites on chromosome 5 (LOD=1.8 at 128 cM, P=0.002). Located under the linkage peak on chromosome 3 is the chemokine receptor gene cluster, including CCR2, the receptor for MCP-1. This study provides preliminary evidence linking genetic variation in a receptor to circulating levels of its ligand, as previously demonstrated for the low-density lipoprotein receptor. Further characterization of these chromosomal regions is needed to identify the functional mutations associated with circulating levels of MCP-1.

Summary of the American Heart Association’s Scientific Statement on the Relevance of Genetics and Genomics for Prevention and Treatment of Cardiovascular Disease

Atherosclerotic cardiovascular disease (CVD) is a major health problem in the United States and around the world.1,2 The development of CVD is a complex process, and evidence demonstrates that family history is associated with CVD.3 There are several mendelian disorders that contribute to CVD, and although the mutations are rare, they have a large relative risk. The most common forms of CVD, however, are believed to be multifactorial and to result from many genes, each with a small effect working alone or in combination with modifier genes or environmental factors. See Circulation. 2007;115:2878–2901 Two main approaches have been used to discover genetic influences on CVD (Figure): genome-wide linkage and gene association studies. For discovery of new genes, the most frequently used method has been genome-wide linkage conducted using genetic and phenotypic data from families. Linkage analysis is a hypothesis-generating method intended to localize genomic regions that might contain genes influencing a trait. Once likely regions have been discovered, efforts shift to identifying the causative genes. Gene maps are scrutinized, and “candidate” genes within regions of interest are identified based on prior knowledge of gene function. Candidate gene association studies are designed to compare genotype frequencies between case and control groups; a statistical difference in frequencies between cases and controls offers evidence that a genotype is associated with the trait. Figure. Fundamentals of the techniques used for the discovery of the genetic basis of CVD. Adapted with permission from: Arnett DK, Baird AE, Barkley RA, Basson CT, Boerwinkle E, Ganesh SK, Herrington DM, Hong Y, Jaquish C, McDermott DA, O’Donnell CJ. Relevance of genetics and genomics for prevention and treatment of cardiovascular disease: a scientific statement from the American Heart Association Council on Epidemiology and Prevention, the Stroke Council, and the Functional Genomics and Translational Biology Interdisciplinary Working Group. …

QTL-specific genotype-by-smoking interaction and burden of calcified coronary atherosclerosis: The NHLBI Family Heart Study

Background Calcified coronary plaque (CCP) is a complex trait influenced by both genes and environment, and plausibly an interaction between the two. Because the familial aggregation of CCP has been demonstrated and smoking is a significant, independent predictor of CCP, we assessed the evidence for genotype-by-smoking interaction and conducted linkage analysis of quantitative Agatston CCP scores in participants of the NHLBI Family Heart Study (FHS). Methods During standardized clinical exams smoking habits were ascertained and CCP was quantified with cardiac computed tomography (CT). Among 4387 relationship pairs from 2128 Caucasian examinees variance component analysis was implemented in SOLAR to examine: (1) additive genotype-by-smoking status interaction using a variance component approach; (2) linkage analysis in the full sample and among smoking subsets defined by individual smoking exposure; (3) QTL-specific genotype-by-smoking interaction in the regions that appeared to differentiate between smoking strata. Results The prevalence of CCP (and median Agatston score) was 75% (184.6) in men and 48% (51.0) in women. We detected four genome-wide significant logarithm of odds (LOD) scores in samples stratified by individual smoking exposure: chromosome 4 at 122 cM (nearest marker D4S2297; robust adjusted LOD = 3.1; q = 0.053), chromosome 6 at 99 cM (nearest marker D6S1056; robust adjusted LOD = 3.3; q = 0.053), chromosome 11 at 19 cM (nearest marker D11S199; robust adjusted LOD = 4.0; q = 0.02) and chromosome 13 at 77 cM (nearest marker D13S892; robust adjusted LOD = 3.1; q = 0.053). Additive and QTL-specific genotype-by-smoking interaction was detected on chromosomes 4, 6, 11 and 13; all P < 0.05. Three of the four QTLs identified in this report have been previously linked to atherosclerosis and harbor interesting candidate genes. Conclusions These findings demonstrate the importance of considering complex interactions in the search for genes that influence the pathogenesis of CCP.

The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

BackgroundA low ankle-brachial index (ABI) is associated with increased risk of coronary heart disease, stroke, and death. Regression model parameter estimates may be biased due to measurement error when the ABI is included as a predictor in regression models, but may be corrected if the reliability coefficient, R, is known. The R for the ABI computed from DINAMAP™ readings of the ankle and brachial SBP is not known.MethodsA total of 119 participants in both the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) had repeat ABIs taken within 1 year, using a common protocol, automated oscillometric blood pressure measurement devices, and technician pool.ResultsThe estimated reliability coefficient for the ankle systolic blood pressure (SBP) was 0.68 (95% CI: 0.57, 0.77) and for the brachial SBP was 0.74 (95% CI: 0.62, 0.83). The reliability for the ABI based on single ankle and arm SBPs was 0.61 (95% CI: 0.50, 0.70) and the reliability of the ABI computed as the ratio of the average of two ankle SBPs to two arm SBPs was estimated from simulated data as 0.70.ConclusionThese reliability estimates may be used to obtain unbiased parameter estimates if the ABI is included in regression models. Our results suggest the need for repeated measures of the ABI in clinical practice, preferably within visits and also over time, before diagnosing peripheral artery disease and before making therapeutic decisions.

The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS)

The “Good Cholesterol”

Atherosclerosis is an insidious and dangerous disease: a progressive chemical and structural injury to the blood vessels in such critical organs as the heart, brain, and kidney. The hallmark feature of atherosclerosis is the buildup of cholesterol into lesions called plaques that can reduce the flow of blood. When the delivery of blood to heart muscle drops enough, this can result in the development of chest pain or angina. Angina indicates that the heart muscle is not receiving enough oxygen to carry out its pumping functions. Atherosclerotic plaques can also suddenly rupture, develop a blood clot on their surface, and completely choke off a portion of heart muscle. This chain of events frequently results in heart attack or sudden death without warning. Atherosclerotic disease also predisposes people to stroke, peripheral vascular disease, lower-extremity amputation, and loss of kidney function, among other devastating outcomes. Despite all that we have learned in the past 50 years, atherosclerosis remains the No. 1 killer of men and women and the chief reason for loss of quality of life in Western countries. We are, however, gaining ground. Considerable research has revealed the importance of factors that increase an individual’s risk for developing this disease. Among the most important of these risk factors are elevated blood pressure, diabetes mellitus, obesity, inactivity, smoking, and cholesterol levels. When your physician measures your cholesterol level, he or she is looking at your lipid profile, which comprises low-density lipoprotein cholesterol (LDL-C, or the “bad” cholesterol), triglycerides (blood fats), and high-density lipoprotein cholesterol (HDL-C, or the “good” cholesterol). In a general way, when it comes to measurement of your LDL-C and triglyceride values, a lower value is better because these lipids drive the development and progression of atherosclerosis. In sharp contrast, when it …

The Impact of Pedigree Structure on Heritability Estimates for Pulse Pressure in Three Studies

Objectives: Pulse pressure (PP) is a measure of large artery stiffness and has been shown to be an important predictor of cardiovascular morbidity and mortality. The aims of the present study were to investigate the heritability of PP in three studies, the Diabetes Heart Study (DHS), the Insulin Resistance Atherosclerosis Family Study (IRAS FS), and the NHLBI Family Heart Study (FHS), to estimate the residual heritability after inclusion of a common set of covariates, and to investigate the impact of pedigree structure on estimating heritability. Methods and Results: DHS is primarily a sibling pair nuclear family study design, while both IRAS FS and FHS have large pedigrees. Heritability estimates of log-transformed PP were obtained using variance component models. After adjusting for age, gender, ethnicity/center, height, diabetes status, and mean arterial pressure (MAP), heritability estimates of PP were 0.40 ± 0.08 , 0.22 ± 0.05, and 0.19 ± 0.03 in DHS, IRAS FS, and FHS, respectively. The heritability estimate from DHS was significantly different from both IRAS FS and FHS (both p values <0.05). A random re-sampling technique (modified bootstrap) was used to explore the heritability in the IRAS FS and FHS data when these pedigrees were trimmed to mimic the DHS pedigree structure. The re-sampling method (mimicking a sibling pair nuclear family design in all studies) yielded PP heritability estimates of 0.37, 0.34, and 0.27 in DHS, IRAS FS, and FHS, respectively. There was no significant difference among the heritability estimates from the three studies based on the re-sampling method. Conclusion: We have shown that PP has a moderately heritable component in three different studies. These data illustrate the influence of pedigree structure can have on estimating heritability. Thoughtful comparisons of heritability estimates must consider study design factors such as pedigree structure.

Genome-wide linkage analysis replicates susceptibility locus for fasting plasma triglycerides: NHLBI Family Heart Study.

Recent reports implicate chromosomal regions linked to inter-individual variation in plasma triglycerides. We conducted genome-wide scans to replicate these linkages and/or identify other loci influencing plasma triglycerides in the NHLBI Family Heart Study (FHS). Data were obtained for 501 three-generational families. Genotyping was done by the Utah Molecular Genetics Laboratory and NHLBI Mammalian Genotyping Service; markers from both were placed on one genetic map. Analysis was done using multipoint variance components linkage. Fasting plasma triglycerides were log-transformed and age-, sex-, and field center-adjusted; suggestive linkage evidence was found on chromosome 8 (LOD=2.80 at 89 cM, marker D8S1141). Further adjustment for waist girth, BMI, diabetes, hypertension, and lipid-lowering drugs suggested linkage regions on chromosomes 6 (LOD=2.29 at 79 cM, marker D6S295) and 15 (LOD=1.85 at 43 cM, marker D15S659). Since HDL is correlated with triglycerides and because it was linked to this region on chromosome 15 in FHS, we created a composite triglyceride-HDL phenotype. The combined phenotype LOD score was 3.0 at the same marker on chromosome 15. Chromosome 15 likely harbors a susceptibility locus with an influence on triglycerides and HDL. Regions on chromosomes 6 and 8 may also contain loci contributing to inter-individual variation in plasma triglycerides.

TXNIP gene not associated with familial combined hyperlipidemia in the NHLBI Family Heart Study

Familial combined hyperlipidemia (FCHL) is the most common familial dyslipidemia, and is implicated in up to 20% of cases of premature coronary heart disease. Positive linkage to chromosome 1q was found in FCHL families participating in the NHLBI Family Heart Study (FHS), replicating linkage found in other studies. The HcB-19 mouse, which shares phenotypes with FCHL, was shown in other studies to have a nonsense mutation in the thioredoxin interacting protein gene ( txnip). txnip is a gene on mouse chromosome 3 in a region syntenic with the 1q human FCHL linkage region. We re-sequenced the human homolog of mouse txnip in the FHS sample and identified nine single nucleotide polymorphisms (SNPs). We did not observe the nonsense mutation found in the HcB-19 mouse, and only three of the SNPs discovered were sufficiently polymorphic for analysis. No association between FCHL and the TXNIP gene was found. Within FCHL cases, presence of variants also did not significantly affect body mass index or levels of lipids, insulin, or glucose. Our results suggest that in this sample, TXNIP does not play a major role in FCHL or related traits, and is unlikely to account for the positive evidence of linkage in this region.

Effects of polymorphisms of methionine synthase and methionine synthase reductase on total plasma homocysteine in the NHLBI Family Heart Study

The metabolism of homocysteine requires contributions of several enzymes and vitamin cofactors. Earlier studies identified a common polymorphism of methylenetetrahydrofolate reductase that was associated with mild hyperhomocysteinemia. Common variants of two other enzymes involved in homocysteine metabolism, methionine synthase and methionine synthase reductase, have also been identified. Methionine synthase catalyzes the remethylation of homocysteine to form methionine and methionine synthase reductase is required for the reductive activation of the cobalamin-dependent methionine synthase. The methionine synthase gene (MTR) mutation is an A to G substitution, 2756A→G, which converts an aspartate to a glycine codon. The methionine synthase reductase gene (MTRR) mutation is an A to G substitution, 66A→G, that converts an isoleucine to a methionine residue. To determine if these polymorphisms were associated with mild hyperhomocysteinemia, we investigated subjects from two of the NHLBI Family Heart Study field centers, Framingham and Utah. Total plasma homocysteine concentrations were determined after an overnight fast and after a 4-h methionine load test. MTR and MTRR genotype data were available for 677 and 562 subjects, respectively. The geometric mean fasting homocysteine was unrelated to the MTR or MTRR genotype categories (AA, AG, GG). After a methionine load, a weak positive association was observed between change in homocysteine after a methionine load and the number of mutant MTR alleles ( P-trend=0.04), but this association was not statistically significant according to the overall F-statistic ( P=0.12). There was no significant interaction between MTR and MTRR genotype or between these genotypes and any of the vitamins with respect to homocysteine concentrations. This study provides no evidence that these common MTR and MTRR mutations are associated with alterations in plasma homocysteine.

A genome-wide screen reveals evidence for a locus on chromosome 11 influencing variation in LDL cholesterol in the NHLBI Family Heart Study.

A genome scan was performed for low-density lipoprotein cholesterol concentration (LDL-C) in white subjects who were ascertained through the NHLBI Family Heart Study (FHS). The NIH Mammalian Genotyping Service (Marshfield, Wis.) genotyped 401 autosomal markers spaced at approximate 10-cM intervals. Additional FHS families were genotyped by the FHS Molecular Laboratory at the University of Utah for 243 markers; 645 subjects were typed in both laboratories so that a combined map of the 644 markers from the two screening sets (average distance of 5.46 cM) could be produced. Analyses were done on 2,799 genotyped subjects in 500 families where at least two genotyped persons in the family had measured LDL-C levels (average number of genotyped family members=5.95). The variance components method was used as implemented in GeneHunter (Kruglyak et al. 1996). Prior to analysis, each phenotype was adjusted, within sex, for age, age squared, body mass index, waist-hip ratio, alcohol, smoking, medication status for diabetes and hypertension, estrogen use, and field center location. Linkage analyses were performed, first excluding 305 subjects on lipid-lowering medications, then again including the data from these subjects. The highest peak was on chromosome 11 at 56.3-56.4 cM, with a maximum lod score of 3.72. Two genome scans of lipid traits in other populations have found peaks in this region. Other scores at or above 1.9 occurred on chromosomes 5 (lod=1.89 at 1.6 cM), 10 (lod=2.47 at 127.1 cM), 17 (lod=2.33 at 116.3 cM), and 21 (lod=2.74 at 45.2 cM).