Heritability of carotid intima-media thickness: a twin study

2024 Heart Disease and Stroke Statistics: A Report of US and Global Data From the American Heart Association

BACKGROUND

The American Heart Association (AHA), in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, nutrition, sleep, and obesity) and health factors (cholesterol, blood pressure, glucose control, and metabolic syndrome) that contribute to cardiovascular health. The AHA Heart Disease and Stroke Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, brain health, complications of pregnancy, kidney disease, congenital heart disease, rhythm disorders, sudden cardiac arrest, subclinical atherosclerosis, coronary heart disease, cardiomyopathy, heart failure, valvular disease, venous thromboembolism, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The AHA, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States and globally to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2024 AHA Statistical Update is the product of a full year's worth of effort in 2023 by dedicated volunteer clinicians and scientists, committed government professionals, and AHA staff members. The AHA strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional global data, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Transcription Factor Regulation of Gene Expression Network by ZNF385D and HAND2 in Carotid Atherosclerosis

Carotid intima-media thickness (CIMT) is a surrogate indicator for atherosclerosis and has been shown to predict cardiovascular risk in multiple large studies. Identification of molecular markers for carotid atheroma plaque formation can be critical for early intervention and prevention of atherosclerosis. This study performed transcription factor (TF) network analysis of global gene expression data focusing on two TF genes, ZNF385D and HAND2, whose polymorphisms have been recently reported to show association with CIMT. Genome-wide gene expression data were measured from pieces of carotid endarterectomy collected from 34 hypertensive patients (atheroma plaque of stages IV and above according to the Stary classification) each paired with one sample of distant macroscopically intact tissue (stages I and II). Transcriptional regulation networks or the regulons were reconstructed for ZNF385D (5644 target genes) and HAND2 (781 target genes) using network inference. Their association with the progression of carotid atheroma was examined using gene-set enrichment analysis with extremely high statistical significance for regulons of both ZNF385D and HAND2 (p < 6.95 × 10-7) suggesting the involvement of expression quantitative loci (eQTL). Functional annotation of the regulon genes found heavy involvement in the immune system's response to inflammation and infection in the development of atherosclerosis. Detailed examination of the regulation and correlation patterns suggests that activities of the two TF genes could have high clinical and interventional impacts on impairing carotid atheroma plaque formation and preventing carotid atherosclerosis.

Heart Disease and Stroke Statistics-2023 Update: A Report From the American Heart Association

BACKGROUND

The American Heart Association, in conjunction with the National Institutes of Health, annually reports the most up-to-date statistics related to heart disease, stroke, and cardiovascular risk factors, including core health behaviors (smoking, physical activity, diet, and weight) and health factors (cholesterol, blood pressure, and glucose control) that contribute to cardiovascular health. The Statistical Update presents the latest data on a range of major clinical heart and circulatory disease conditions (including stroke, congenital heart disease, rhythm disorders, subclinical atherosclerosis, coronary heart disease, heart failure, valvular disease, venous disease, and peripheral artery disease) and the associated outcomes (including quality of care, procedures, and economic costs).

METHODS

The American Heart Association, through its Epidemiology and Prevention Statistics Committee, continuously monitors and evaluates sources of data on heart disease and stroke in the United States to provide the most current information available in the annual Statistical Update with review of published literature through the year before writing. The 2023 Statistical Update is the product of a full year's worth of effort in 2022 by dedicated volunteer clinicians and scientists, committed government professionals, and American Heart Association staff members. The American Heart Association strives to further understand and help heal health problems inflicted by structural racism, a public health crisis that can significantly damage physical and mental health and perpetuate disparities in access to health care, education, income, housing, and several other factors vital to healthy lives. This year's edition includes additional COVID-19 (coronavirus disease 2019) publications, as well as data on the monitoring and benefits of cardiovascular health in the population, with an enhanced focus on health equity across several key domains.

RESULTS

Each of the chapters in the Statistical Update focuses on a different topic related to heart disease and stroke statistics.

CONCLUSIONS

The Statistical Update represents a critical resource for the lay public, policymakers, media professionals, clinicians, health care administrators, researchers, health advocates, and others seeking the best available data on these factors and conditions.

Increased Carotid Intima-Media Thickness in Asymptomatic Individuals Is Associated with the PCSK9 (rs2149041) Gene Polymorphism in the Mexican Mestizo Population: Results of the GEA Cohort

The increase in carotid intima-media thickness (CIMT) and coronary artery calcification (CAC) are features of subclinical atherosclerosis that might be determined by the genetic background of patients. Among the multiple risk factors, the proprotein convertase subtilisin kexin type 9 (PCSK9) has a great impact on atheroma development. Then, we focused on the potential association of the PCSK9 gene polymorphism (rs2149041) with the risk of an increased CIMT. We included 881 unrelated, asymptomatic individuals (732 normal CIMT and 149 increased CIMT) who lacked coronary calcification (CAC score = 0). Under the recessive inheritance model and adjusted by several cardiovascular risk factors, the rs2149041 polymorphism, determined by TaqMan genotyping assay, was associated with a high risk of increased CIMT (OR = 2.10, 95% IC = 1.26–3.47, P recessive = 0.004). Our results suggest that the rs2149041 polymorphism could be a risk marker for increased CIMT in asymptomatic individuals without coronary artery disease determined by the absence of a CAC score.

Sex-specific association between inflammation and endothelial function relevant gene and vulnerable carotid plaque

Objectives: We aimed to explore sex-specific association between genes involved in inflammation and endothelial function and vulnerable carotid plaque, a subclinical precursor of ischemic stroke.

Methods: Carotid plaque and plaque phenotype were assessed by carotid ultrasound in high-risk participants for stroke drawn from a multicenter, cross-sectional survey in southwestern China. We examined 18 single nucleotide polymorphisms (SNPs) in 10 genes related to inflammation and endothelial function. Sex differences in the genotype of the candidate SNPs and risk of vulnerable carotid plaques were assessed. Interaction tests were performed to identify the SNPs that might modify the association between the sex and vulnerable plaques. For SNPs with suggestive evidence for interaction with sex (p for interaction&lt;0.05), stratification analysis by sex was performed to evaluate the sex-specific association between the SNP and vulnerable plaques.

Results: 2,644 high-risk individuals were enrolled, comprising 1,202 (45.5%) men and 1,442 (54.5%) women. Vulnerable carotid plaques were detected in 425 (16.1%) participants. Among candidate SNPs, the genotype frequencies of 5 SNPs (TNFSF4 rs11811788, TNFSF4 rs1234313, IL6R rs4845625, VCAM1 rs2392221, and ITGA2 rs1991013) were significantly different between sex (all p &lt; 0.05). Univariable and multivariable analyses suggested that male individuals had a significantly higher prevalence of vulnerable carotid plaques (20.0% vs. 12.8%, adjusted OR 1.72, 95% CI 1.12–2.66, p = 0.014), while none of the candidate SNPs was significantly associated with vulnerable plaques (all p &gt; 0.05). Interaction tests found the association between sex and vulnerable plaques is affected by the genotype of IL6R rs4845625 (p for interaction = 0.031). Stratification analysis revealed a strong association between IL6R rs4845625 and vulnerable carotid plaque in man (dominant model TT vs. CT + CC: adjusted OR 1.52, 95% CI 1.12–2.07, p = 0.007; codominant model TT vs. CC: adjusted OR 1.50, 95% CI 1.00–2.25, p = 0.048) but not in women (p &gt; 0.05 in all genetic models).

Conclusion: The rs4845625 polymorphism in IL6R has sex-specific effects on vulnerable carotid plaque in Chinese Han high-risk individuals for stroke. Our findings provide a plausible genetic basis underlying the sex difference in carotid plaque vulnerability.

Genetic connection of carotid atherosclerosis with coat color and body weight in an intercross between hyperlipidemic mouse strains

Atherosclerosis in the carotid artery is a major cause of ischemic stroke and has a strong genetic component. The aim of this study was to identify genetic factors contributing to carotid atherosclerosis. 154 female F2mice were generated from an intercross between LP/J and BALB/cJ Apoe-null (Apoe^-/-) mice and fed 12 weeks of Western diet. Atherosclerotic lesions, body weight, and coat color were measured and genotyping was performed using miniMUGA arrays. A significant QTL on chromosome (Chr) 7, named Cath20, and 5 suggestive QTL on Chr 6, 12, 13, 15, and X were identified for carotid lesions. Three significant QTL, Bwfq2, Bw1n, Bwtq6, on Chr 2, 7, and 15 were identified for body weight. Two significant QTL, Chop2 and Albc2, on Chr 4 and 7 were identified for coat color, with Tyr, encoding tyrosinase, being the causal gene of Albc2. Cath20 coincided precisely with QTL Bw1n and Albc2 on Chr7. Carotid lesion sizes were significantly correlated with body weight and graded coat color in F2 mice. Cath20 on Chr7 disappeared after adjustment for coat color but remained after adjustment for body weight. These results demonstrate genetic connections of carotid atherosclerosis with body weight and coat color in hyperlipidemic mice and suggest a potential role for Tyr in carotid atherosclerosis.

Genetic Connection between Hyperglycemia and Carotid Atherosclerosis in Hyperlipidemic Mice

Type 2 diabetes (T2D) is a major risk for atherosclerosis and its complications. Apoe-null (Apoe^−/−) mouse strains exhibit a wide range of variations in susceptibility to T2D and carotid atherosclerosis, with the latter being a major cause of ischemic stroke. To identify genetic connections between T2D and carotid atherosclerosis, 145 male F2 mice were generated from LP/J and BALB/cJ Apoe^−/− mice and fed 12 weeks of a Western diet. Atherosclerotic lesions in the carotid arteries, fasting, and non-fasting plasma glucose levels were measured, and genotyping was performed using miniMUGA arrays. Two significant QTL (quantitative trait loci) on chromosomes (Chr) 6 and 15 were identified for carotid lesions. The Chr15 QTL coincided precisely with QTL Bglu20 for fasting and non-fasting glucose levels. Carotid lesion sizes showed a trend toward correlation with fasting and non-fasting glucose levels in F2 mice. The Chr15 QTL for carotid lesions was suppressed after excluding the influence from fasting or non-fasting glucose. Likely candidate genes for the causal association were Tnfrsf11b, Deptor, and Gsdmc2. These results demonstrate a causative role for hyperglycemia in the development of carotid atherosclerosis in hyperlipidemic mice.

Twenty-Five Novel Loci for Carotid Intima-Media Thickness: A Genome-Wide Association Study in >45 000 Individuals and Meta-Analysis of >100 000 Individuals

OBJECTIVE

Carotid artery intima-media thickness (cIMT) is a widely accepted marker of subclinical atherosclerosis. Twenty susceptibility loci for cIMT were previously identified and the identification of additional susceptibility loci furthers our knowledge on the genetic architecture underlying atherosclerosis. Approach and Results: We performed 3 genome-wide association studies in 45 185 participants from the UK Biobank study who underwent cIMT measurements and had data on minimum, mean, and maximum thickness. We replicated 15 known loci and identified 20 novel loci associated with cIMT at P<5×10^-8. Seven novel loci (ZNF385D, ADAMTS9, EDNRA, HAND2, MYOCD, ITCH/EDEM2/matrix metalloproteinase [MMP]24, and MRTFA) were identified in all 3 phenotypes. An additional new locus (LOXL1) was identified in the meta-analysis of the 3 phenotypes. Sex interaction analysis revealed sex differences in 7 loci including a novel locus (SYNE3) in males. Meta-analysis of UK Biobank data with a previous meta-analysis led to identification of three novel loci (APOB, FIP1L1, and LOXL4). Transcriptome-wide association analyses implicated additional genes ARHGAP42, NDRG4, and KANK2. Gene set analysis showed an enrichment in extracellular organization and the PDGF (platelet-derived growth factor) signaling pathway. We found positive genetic correlations of cIMT with coronary artery disease r_g=0.21 (P=1.4×10^-7), peripheral artery disease r_g=0.45 (P=5.3×10^-5), and systolic blood pressure r_g=0.30 (P=4.0×10^-18). A negative genetic correlation between average of maximum cIMT and high-density lipoprotein was found r_g=-0.12 (P=7.0×10^-4).

CONCLUSIONS

Genome-wide association meta-analyses in >100 000 individuals identified 25 novel loci associated with cIMT providing insights into genes and tissue-specific regulatory mechanisms of proatherosclerotic processes. We found evidence for shared biological mechanisms with cardiovascular diseases.

Multiethnic Genome-Wide Association Study of Subclinical Atherosclerosis in Individuals With Type 2 Diabetes

BACKGROUND

Coronary artery calcification (CAC) and carotid artery intima-media thickness (cIMT) are measures of subclinical atherosclerosis in asymptomatic individuals and strong risk factors for cardiovascular disease. Type 2 diabetes (T2D) is an independent cardiovascular disease risk factor that accelerates atherosclerosis.

METHODS

We performed meta-analyses of genome-wide association studies in up to 2500 T2D individuals of European ancestry (EA) and 1590 T2D individuals of African ancestry with or without exclusion of prevalent cardiovascular disease, for CAC measured by cardiac computed tomography, and 3608 individuals of EA and 838 individuals of African ancestry with T2D for cIMT measured by ultrasonography within the CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology) Consortium.

RESULTS

We replicated 2 loci (rs9369640 and rs9349379 near PHACTR1 and rs10757278 near CDKN2B) for CAC and one locus for cIMT (rs7412 and rs445925 near APOE-APOC1) that were previously reported in the general EA populations. We identified one novel CAC locus (rs8000449 near CSNK1A1L/LINC00547/POSTN at 13q13.3) at P=2.0×10-8 in EA. No additional loci were identified with the meta-analyses of EA and African ancestry. The expression quantitative trait loci analysis with nearby expressed genes derived from arterial wall and metabolic tissues from the Genotype-Tissue Expression project pinpoints POSTN, encoding a matricellular protein involved in bone formation and bone matrix organization, as the potential candidate gene at this locus. In addition, we found significant associations (P<3.1×10-4) for 3 previously reported coronary artery disease loci for these subclinical atherosclerotic phenotypes (rs2891168 near CDKN2B-AS1 and rs11170820 near FLJ12825 for CAC, and rs7412 near APOE for cIMT).

CONCLUSIONS

Our results provide potential biological mechanisms that could link CAC and cIMT to increased cardiovascular disease risk in individuals with T2D.

Associations between SNP83 of phosphodiesterase 4D gene and carotid atherosclerosis in a southern Chinese Han population: a case-control study

Atherosclerosis was an important pathophysiological basis of atherothrombotic stroke, and phosphodiesterase 4D (PDE4D) polymorphism (SNP83/rs966221) was reported to be associated with the susceptibility to atherothrombotic stroke. Aim of the present study was to explore the potential association between SNP83 and carotid atherosclerosis (CAS). 204 southern Chinese Han participants were divided into two groups according to the carotid intima-media thickness (IMT) of the carotid artery: CAS group (carotid IMT ≥ 1.0 mm) and non-CAS group (carotid IMT < 1.0 mm). Carotid IMT was measured by color Doppler ultrasound. The PDE4D SNP83 polymorphism was determined by SNaPshot technique. Our study found that SNP83 was associated significantly with CAS susceptibility under the dominant, overdominant and codominant models. After adjusting for age, gender, low-density lipoprotein cholesterol, Hemoglobin A1c, cigarette smoking, hypertension history, and diabetes mellitus history, the association still remained significant (dominant model: crude OR = 2.373, 95% CI: 1.268-4.442, P = 0.007; adjusted OR = 3.129, 95% CI: 1.104-8.866, P = 0.032; overdominant model: crude OR = 1.968, 95% CI: 1.043-3.714, P = 0.037; adjusted OR = 2.854, 95% CI: 1.005-8.108, P = 0.049; codominant: crude OR = 2.102, 95% CI: 1.110-3.979, P = 0.023; adjusted OR = 2.984, 95% CI: 1.047-8.502, P = 0.041). Carotid IMT of carriers with CT + CC genotypes was higher than carriers with TT genotype (P = 0.016). Our results indicated that the SNP83/rs966221 located on PDE4D gene was significantly associated between CAS susceptibility and carotid IMT independently of conventional risk factors in a southern Chinese Han population.

Association between Gut Microbial Diversity and Carotid Intima-Media Thickness

Background and Objectives: There is an increasing focus on the effect of the gut microbiome on developing atherosclerosis, but there is still no unified standpoint. We aimed to find associations between intestinal microbiome diversity and a marker of subclinical atherosclerosis, the carotid intima-media thickness (IMT). Materials and Methods: Recruited from the Hungarian Twin Registry, 108 monozygotic (MZ) twins (mean age 52.4 ± 14.1 years, 58% female) underwent a comprehensive carotid ultrasound examination (Samsung RS85). Of the 108 MZ twins, 14 pairs (mean age 65 ± 6.4 years, 71% female) discordant for carotid IMT were selected to undergo a stool sample collection. A special stool sampling container was mailed and received from each participant. After DNA extraction, library construction was performed specifically for the V3–V4 hypervariable region of microbial 16S rRNA. Next, the microbiome composition of the samples was determined using Kraken software. Two hypotheses were tested with the exact permutation test: (1) in the group with normal IMT, the Shannon index of the phyla is higher; and (2) the Firmicutes/Bacteroidetes ratio is greater in the group with high IMT values. Furthermore, the abundance of different bacterial strains present at higher and normal IMT was also explored. Statistical analysis was carried out using R software. Results: Increased Firmicutes/Bacteroidetes ratio was associated with increased IMT (mean Firmicutes/Bacteroidetes ratio of IMT > 0.9 and IMT < 0.9 groups: 2.299 and 1.436, respectively; p = 0.031). In the group with normal IMT values, a substantially higher fraction of Prevotellaceae was observed in contrast with subjects having subclinical atherosclerosis. However, there was no significant difference in the alpha diversity between the two groups. Conclusions: The determining role of individual genera and their proportions in the development and progression of atherosclerosis can be assumed. Further studies are needed to clarify if these findings can be used as potential therapeutic targets.

Inflammation and Endothelial Function Relevant Genetic Polymorphisms and Carotid Plaque in Chinese Population

Aim: To examine the association between carotid plaque and variants in genes involved in inflammation and endothelial function.

Methods: This was a multicenter, cross-sectional survey in southwestern China. The residents aged ≥ 40 years volunteered to participate in the face-to-face survey in eight communities. A total of 2,377 subjects with high stroke risk were enrolled. Carotid plaque and plaque phenotype were assessed by carotid ultrasound. Genotypes of 19 variants in 10 genes related to inflammation and endothelial function were examined. Gene-gene interaction was analyzed by generalized multifactor dimensionality reduction (GMDR).

Results: Carotid plaques were found in 852 (35.8%) subjects, and 454 (53.3%) had stable plaques, whereas 398 (46.7%) had vulnerable plaques. PPARA rs4253655, HABP2 rs7923349, and IL1A rs1609682 were associated with the presence of carotid plaque, and NOS2A rs2297518 and PPARA rs4253655 were associated with vulnerable plaque in univariate analysis. The GMDR analysis revealed that there was a significant gene–gene interaction among HABP2 rs7923349, ITGA2 rs1991013, IL1A rs1609682, and NOS2A rs8081248, and the high-risk interactive genotype among the four variants was independently associated with a higher risk of carotid vulnerable plaque after adjusting the covariates (OR, 2.86, 95% CI: 1.32–7.13, P = 0.003).

Conclusion: The prevalence of carotid plaque was very high in the high-risk stroke population in southwestern China. Variants in genes involved in the endothelial function and inflammation were associated with the carotid plaque. The high-risk interactive genotype among rs7923349, rs1991013, rs1609682, and rs8081248 was independently associated with a higher risk of vulnerable plaque.

Genetic and environmental factors on heart rate, mean arterial pressure and carotid intima-media thickness: A longitudinal twin study

BACKGROUND

Heart rate (HR), mean arterial pressure (MAP) and carotid intima-media thickness (cIMT) are moderately heritable cardiovascular traits, but the environmental effects on the longitudinal change of their heritability have never been investigated.

METHODS

368 Italian and Hungarian twins (107 monozygotic, 77 dizygotic) underwent oscillometric measurement and B-mode sonography of bilateral carotid arteries in 2009/2010 and 2014. Within- -individual/cross-study wave, cross-twin/within-study wave and cross-twin/cross-study wave correlations were estimated, and bivariate Cholesky models were fitted to decompose the total variance at each wave and covariance between study waves into additive genetic, shared and unique environmental components.

RESULTS

For each trait, a moderate longitudinal stability was observed, with within-individual/crosswave correlations of 0.42 (95% CI: 0.33-0.51) for HR, 0.34 (95% CI: 0.24-0.43) for MAP, and 0.23 (95% CI: 0.12-0.33) for cIMT. Cross-twin/cross-wave correlations in monozygotic pairs were all significant and substantially higher than the corresponding dizygotic correlations. Genetic continuity was the main source of longitudinal stability, with across-time genetic correlations of 0.52 (95% CI: 0.29-0.71) for HR, 0.56 (95% CI: 0.31-0.81) for MAP, and 0.36 (95% CI: 0.07-0.64) for cIMT. Overlapping genetic factors explained respectively 57%, 77%, and 68% of the longitudinal covariance of the HR, MAP and cIMT traits.

CONCLUSIONS

Genetic factors have a substantial role in the longitudinal change of HR, MAP and cIMT; however, the influence of unique environmental factors remains relevant. Further studies should better elucidate whether epigenetic mechanisms have a role in influencing the stability of the investigated traits over time.

Carotid artery intima-media thickness, distensibility and elasticity: population epidemiology and concordance in Australian children aged 11-12 years old and their parents

OBJECTIVES

To describe a well-established marker of cardiovascular risk, carotid intima-media thickness (IMT) and related measures (artery distensibility and elasticity) in children aged 11-12 years old and mid-life adults, and examine associations within parent-child dyads.

DESIGN

Cross-sectional study (Child Health CheckPoint), nested within a prospective cohort study, the Longitudinal Study of Australian Children (LSAC).

SETTING

Assessment centres in seven Australian major cities and eight selected regional towns, February 2015 to March 2016.

PARTICIPANTS

Of all participating CheckPoint families (n=1874), 1489 children (50.0% girls) and 1476 parents (86.8% mothers) with carotid IMT data were included. Survey weights and methods were applied to account for LSAC's complex sample design and clustering within postcodes and strata.

OUTCOME MEASURES

Ultrasound of the right carotid artery was performed using standardised protocols. Primary outcomes were mean and maximum far-wall carotid IMT, quantified using semiautomated edge detection software. Secondary outcomes were carotid artery distensibility and elasticity. Pearson's correlation coefficients and multivariable linear regression models were used to assess parent-child concordance. Random effects modelling on a subset of ultrasounds (with repeated measurements) was used to assess reliability of the child carotid IMT measure.

RESULTS

The average mean and maximum child carotid IMT were 0.50 mm (SD 0.06) and 0.58 mm (SD 0.05), respectively. In adults, average mean and maximum carotid IMT were 0.57 mm (SD 0.07) and 0.66 mm (SD 0.10), respectively. Mother-child correlations for mean and maximum carotid IMT were 0.12 (95% CI 0.05 to 0.23) and 0.10 (95% CI 0.03 to 0.21), respectively. For carotid artery distensibility and elasticity, mother-child correlations were 0.19 (95% CI 0.10 to 0.25) and 0.11 (95% CI 0.02 to 0.18), respectively. There was no strong evidence of father-child correlation in any measure.

CONCLUSIONS

We provide Australian values for carotid vascular measures and report a modest mother-child concordance. Both genetic and environmental exposures are likely to contribute to carotid IMT.

Common Genetic Variants on Bone Morphogenetic Protein Receptor Type IB (BMPR1B) Gene Are Predictive for Carotid Intima-Media Thickness

BACKGROUND

Bone morphogenetic proteins (BMP) 2 and 4 are implicated in the development of atherosclerosis. However, the relationships between the proteins, their main receptors and carotid intima-media thickness (cIMT), a predictive preclinical phenotype of atherosclerosis, have not been established. Methods and Results: We screened and validated the relationships of single-nucleotide polymorphisms (SNPs) on BMP2, BMP4, BMPR1A, BMPR1B, and BMPR2 with thicker cIMT by 2 independent case-control studies that used different subject selection methods. Among 200 screened SNPs, 12 on BMPR1B were regarded as candidate genetic markers (P-value <5.0×10^-4). After combining the discovery and validation studies and adjusting for traditional cardiovascular risk factors, rs4456963*G, rs4235438*T, rs2522530*T, and rs3796433*C showed significant higher odds ratios (ORs) of having thicker cIMT (adjusted ORs: 1.50-1.56; all P-values <2.5×10^-4). Multivariate analyses showed that rs4456963 and rs3796433 were significantly independent determinants of cIMT thickening. The corresponding multivariate-adjusted ORs for rs4456963*G and rs3796433*C alleles were 1.50 (95% confidence interval (CI): 1.22-1.84) and 1.50 (95% CI: 1.23-1.82), respectively. Interaction between rs4456963 and rs3796433 was evident by the significantly higher OR (8.16, 95% CI: 3.12-21.3) for subjects with the GG-CC genotype. The rs4456963*G and rs3796433*C showed positively linear trends with severity of carotid atherosclerosis.

CONCLUSIONS

We identified 2 SNPs on BMPR1B showing significantly independent correlations with thicker cIMT. The study provides invaluable evidence supporting that BMPR1B is closely related to carotid atherosclerosis and a potential target for the development of therapeutic agents for atherosclerotic disease.

Associations of Common Genetic Variants on IL-17 Genes and Carotid Intima-Media Thickness

AIM

Atherosclerosis is a chronic inflammatory process of the arterial wall and carotid intima-media thickness (cIMT) is regarded as its early marker. Several members of the IL-17 family are involved in pro-inflammatory functions. The specific aim of the study was to explore the relationships of common genetic variants on IL-17 genes with cIMT thickening.

METHODS

In the discovery stage, 146 SNPs on 11 IL-17 genes were screened for their relationships with cIMT by a case-control study that enrolled 284 and 464 subjects who had thicker and normal cIMT, respectively. Findings were replicated by an independent case-control study that enrolled 282 subjects who had thicker cIMT and 282 age-sex-matched subjects who had normal cIMT.

RESULTS

Among 134 eligible SNPs in the discovery study, only IL-17RC rs279545 was significantly correlated with cIMT (p=6.9×10^-5). The rs279545 and 2 nearby linked SNPs rs55847610 and rs3846167 were included in the validation study. We found that the rs279545^＊G, rs55847610^＊G, and rs3846167^＊C were correlated with significantly higher likelihoods of having thicker cIMT. The corresponding multivariate-adjusted ORs were 1.462 (95% CI: 1.055-2.027), 1.481 (95% CI:1.090-2.013), and 1.589 (95% CI: 1.147-2.200), respectively. Analyses of rs279545-rs55847610 haplotypes showed that the multivariate-adjusted OR for A-A haplotype was significantly decreased (OR=0.665, 95% CI: 0.487-0.908) and for G-G haplotype was significantly increased (OR=1.539, 95% CI: 1.097-2.161).

CONCLUSIONS

We first correlated cIMT, a preclinical clinical cardiovascular marker, with IL-17RC, the key molecule in the IL-17 signaling pathway. Our results indicated that IL-17RC may play critical role in the development of atherosclerotic diseases.

Carotid Artery Atherosclerosis: A Review on Heritability and Genetics

Carotid atherosclerosis (CAS) is associated with increased cardiovascular risk, and therefore, assessing the genetic versus environmental background of CAS traits is of key importance. Carotid intima-media-thickness and plaque characteristics seem to be moderately heritable, with remarkable differences in both heritability and presence or severity of these traits among ethnicities. Although the considerable role of additive genetic effects is obvious, based on the results so far, there is an important emphasis on non-shared environmental factors as well. We aimed to collect and summarize the papers that investigate twin and family studies assessing the phenotypic variance attributable to genetic associations with CAS. Genes in relation to CAS markers were overviewed with a focus on genetic association studies and genome-wide association studies. Although the role of certain genes is confirmed by studies conducted on large populations and meta-analyses, many of them show conflicting results. A great focus should be on future studies elucidating the exact pathomechanism of these genes in CAS in order to imply them as novel therapeutic targets.

Twins Lead to the Prevention of Atherosclerosis: Preliminary Findings of International Twin Study 2009

Introduction

Atherosclerosis is an inflammatory process in which the artery wall thickens as a result of plaque deposition, but this process may be preceded by increased arterial stiffness. We sought to evaluate the influence of genetics and shared and unshared environmental components on the onset of atherosclerosis.

Methods

A total of 135 monozygotic (MZ) and 70 dizygotic (DZ) twin pairs (mean age 49 ± 16 years) underwent carotid intima media thickness (IMT; carotid analyzer) and arterial stiffness (augmentation index on brachial artery [ Aixbra], pulse wave velocity on aorta [ PWVao]; TensioMed Arteriograph) measurements.

Results

Age-adjusted intraclass correlations were greater in MZ than in DZ pairs for proximal right common carotid artery (CCA; MZ = 0.19, DZ = 0.06), proximal and distal left CCA (MZ = 0.27, DZ = 0.06; MZ = 0.27, DZ = 0.13, respectively), and proximal left internal carotid artery (ICA; MZ = 0.39, DZ = −0.54), suggesting a moderate genetic effect. Heritability was estimated to be 18% (95% confidence interval [CI] = 3–33) for proximal right CCA, 26% and 27% for proximal and distal left CCA, respectively, and 38% (95% CI = 26–49) for proximal left ICA. Regarding distal right CCA and proximal right ICA, no genetic effects were detected. Age-adjusted intraclass correlation of Aixbra and PWVao were 0.65 (95% CI = 0.55–0.72) and 0.46 (95% CI = 0.33–0.57) in MZ, 0.42 (95% CI = 0.24–0.57) and 0.28 (95% CI = 0.08–0.47) in DZ pairs; heritability 45% (95% CI = 12–71%) and 42% (95% CI = 2–57%) adjusted by age, respectively.

Conclusions

The investigated parameters appeared to be only moderately influenced by genetic factors. Environmental factors of relevance for these measures appeared not to be shared within family but related to individual experience (e.g., smoking habits, diet, and physical activity). Atherosclerosis detection at an early stage is necessary for treatment to prevent serious complications such as stroke and heart attack.

Polygenic Control of Carotid Atherosclerosis in a BALB/cJ × SM/J Intercross and a Combined Cross Involving Multiple Mouse Strains

Atherosclerosis in the carotid arteries is a major cause of ischemic stroke, which accounts for 85% of all stroke cases. Genetic factors contributing to carotid atherosclerosis remain poorly understood. The aim of this study was to identify chromosomal regions harboring genes contributing to carotid atherosclerosis in mice. From an intercross between BALB/cJ (BALB) and SM/J (SM) apolipoprotein E-deficient (Apoe^-/-) mice, 228 female F2 mice were generated and fed a "Western" diet for 12 wk. Atherosclerotic lesion sizes in the left carotid artery were quantified. Across the entire genome, 149 genetic markers were genotyped. Quantitative trait locus (QTL) analysis revealed eight loci for carotid lesion sizes, located on chromosomes 1, 5, 12, 13, 15, 16, and 18. Combined cross-linkage analysis using data from this cross, and two previous F2 crosses derived from BALB, C57BL/6J and C3H/HeJ strains, identified five significant QTL on chromosomes 5, 9, 12, and 13, and nine suggestive QTL for carotid atherosclerosis. Of them, the QTL on chromosome 12 had a high LOD score of 9.95. Bioinformatic analysis prioritized Arhgap5, Akap6, Mipol1, Clec14a, Fancm, Nin, Dact1, Rtn1, and Slc38a6 as probable candidate genes for this QTL. Atherosclerotic lesion sizes were significantly correlated with non-HDL cholesterol levels (r = 0.254; p = 0.00016) but inversely correlated with HDL cholesterol levels (r = -0.134; p = 0.049) in the current cross. Thus, we demonstrated the polygenic control of carotid atherosclerosis in mice. The correlations of carotid lesion sizes with non-HDL and HDL suggest that genetic factors exert effects on carotid atherosclerosis partially through modulation of lipoprotein homeostasis.

Multiethnic Exome-Wide Association Study of Subclinical Atherosclerosis

BACKGROUND

The burden of subclinical atherosclerosis in asymptomatic individuals is heritable and associated with elevated risk of developing clinical coronary heart disease. We sought to identify genetic variants in protein-coding regions associated with subclinical atherosclerosis and the risk of subsequent coronary heart disease.

METHODS AND RESULTS

We studied a total of 25 109 European ancestry and African ancestry participants with coronary artery calcification (CAC) measured by cardiac computed tomography and 52 869 participants with common carotid intima-media thickness measured by ultrasonography within the CHARGE Consortium (Cohorts for Heart and Aging Research in Genomic Epidemiology). Participants were genotyped for 247 870 DNA sequence variants (231 539 in exons) across the genome. A meta-analysis of exome-wide association studies was performed across cohorts for CAC and carotid intima-media thickness. APOB p.Arg3527Gln was associated with 4-fold excess CAC (P=3×10^-10). The APOE ε2 allele (p.Arg176Cys) was associated with both 22.3% reduced CAC (P=1×10^-12) and 1.4% reduced carotid intima-media thickness (P=4×10^-14) in carriers compared with noncarriers. In secondary analyses conditioning on low-density lipoprotein cholesterol concentration, the ε2 protective association with CAC, although attenuated, remained strongly significant. Additionally, the presence of ε2 was associated with reduced risk for coronary heart disease (odds ratio 0.77; P=1×10^-11).

CONCLUSIONS

Exome-wide association meta-analysis demonstrates that protein-coding variants in APOB and APOE associate with subclinical atherosclerosis. APOE ε2 represents the first significant association for multiple subclinical atherosclerosis traits across multiple ethnicities, as well as clinical coronary heart disease.

Genetic Research and Women's Heart Disease: a Primer

PURPOSE OF REVIEW

This review provides a brief synopsis of sexual dimorphism in atherosclerosis with an emphasis on genetic studies aimed to better understand the atherosclerotic process and clinical outcomes in women. Such studies are warranted because development of atherosclerosis, impact of several traditional risk factors, and burden of coronary heart disease (CHD) differ between women and men.

RECENT FINDINGS

While most candidate gene studies pool women and men and adjust for sex, some sex-specific studies provide evidence of association between candidate genes and prevalent and incident CHD in women. So far, most genome-wide association studies (GWAS) also failed to consider sex-specific associations. The few GWAS focused on women tended to have small sample sizes and insufficient power to reject the null hypothesis of no association even if associations exist. Few studies consider that sex can modify the effect of gene variants on CHD. Sufficiently large-scale genetic studies in women of different race/ethnic groups, taking into account possible gene-gene and gene-environment interactions as well as hormone-mediated epigenetic mechanisms, are needed. Using the same disease definition for women and men might not be appropriate. Accurate phenotyping and inclusion of relevant outcomes in women, together with targeting the entire spectrum of atherosclerosis, could help address the contribution of genes to sexual dimorphism in atherosclerosis. Discovered genetic loci should be taken forward for replication and functional studies to elucidate the plausible underlying biological mechanisms. A better understanding of the etiology of atherosclerosis in women would facilitate future prevention efforts and interventions.

Associations of EDNRA and EDN1 polymorphisms with carotid intima media thickness through interactions with gender, regular exercise, and obesity in subjects in Taiwan: Taichung Community Health Study (TCHS)

The aim of this study was to evaluate the interacted association between EDNRA and EDN1 polymorphisms and gender, regular exercise, and obesity status on carotid intima media thickness (IMT) in community- dwelling subjects of the Taichung Community Health Study. Five single-nucleotide polymorphisms (SNPs rs1395821, rs1878406, rs5333, rs1800541, and rs5370) of the EDNRA and EDN1 gene were examined in 480 participants from 160 families. The IMT protocol involves scanning the common carotid arteries (CCAs), the carotid bifurcations (bulb), and the origins (first 1 cm) of the internal carotid arteries (ICAs). Generalized linear models with a generalized estimating equation were employed to consider the dependence among family members. After multivariate adjustment, the effects of interactions between EDNRA and EDN1 gene with gender, obesity, and exercise were observed. For gene-gender interaction on CCA IMT, the adjusted mean for men carrying the GA/GG genotype of EDNRASNP rs1878406 was 1.18 times higher than that for men carrying the AA genotype (95% CI: 1.01, 1.37). As for bulb and ICA IMT, the adjusted mean values for women carrying the AC/AA genotype of EDN1 rs5370 was lower than those carrying the CC genotype: 0.89, [0.82, 0.98]; and 0.90 [0.83, 0.99], respectively. We did observe significant effects of EDNRA SNPs rs1395821 and rs5333 in individuals who regularly exercised. A significantly lower adjusted mean in CCA IMT for non-obese individuals carrying EDNRA SNP rs5333 was observed (0.92 [0.86, 0.99]) compared with non-obese individuals carrying the AA genotype. This study first reported significant interactions of EDNRA and EDN1 polymorphisms with gender, regular exercise, and obesity on carotid IMT in Han Chinese participants.

Angle between the common and internal carotid arteries detected by ultrasound is related to intima-media thickness among those with atherosclerotic disease

OBJECTIVES

Although carotid artery structural variations have been detected by ultrasound, their clinical significance is not fully understood. The objective of this study was to determine whether the angle between the common carotid artery (CCA) and the internal carotid artery (ICA), designated angle α, an ultrasound-detectable carotid artery structural variation, is related to carotid artery intima-media thickness (IMT), a surrogate marker for carotid atherosclerosis.

METHODS

As a cross-sectional study, we measured angle α in routine carotid artery ultrasounds from 176 subjects (130 men) with atherosclerotic disease/risk factors that attended Kouseiren Hospital in Kagoshima City, Japan between August 2007 and April 2009. We evaluated the correlation between the angle α and CCA- or ICA-IMT.

RESULTS

Angle α was weakly correlated with age but significantly correlated with ICA-IMT. The correlation was stronger in subjects with an ICA-IMT ≥ 0.5 mm than in those with an ICA-IMT < 0.5 mm (Right side r = 0.475 vs. 0.246, Left side r = 0.498 vs. 0.301, respectively). Upon multivariate logistic regression analysis, angle α and serum low-density lipoprotein cholesterol were independent explanatory variables for ICA-IMT.

CONCLUSION

Angle α is related to ICA-IMT in subjects with atherosclerotic disease or risk factors in this study.

Genetic association and gene-smoking interaction study of carotid intima-media thickness at five GWAS-indicated genes: the Bogalusa Heart Study

OBJECTIVES

To examine the associations of five GWAS-identified genes with carotid intima-media thickness (IMT) in a biracial sample from the Bogalusa Heart Study, and evaluate their participation in gene-smoking interactions.

METHODS

Far wall IMTs of common carotid arteries were measured using high-resolution B-mode ultrasound. Both the gene-smoking interactions and single-marker associations were evaluated by linear models of carotid IMT levels, while the gene-based analyses were assessed through the truncated product method. A Bonferroni multiple testing correction was applied.

RESULTS

Marker rs7840785 (PINX1) was significantly associated with right carotid IMT (p=0.0003) using all participants; mean levels for the CC, TC, and TT genotypes were 0.74 (0.73 to 0.75), 0.76 (0.75 to 0.78), and 0.78 (0.75, 0.81), respectively. Similar trends were observed in blacks (p=0.0031) and whites (p=0.0118). Marker rs7844465 (ZHX2) was significantly associated with left carotid IMT in whites (p=0.0005); mean IMT levels for the GG, TG, and TT genotypes were 0.73 (0.71 to 0.74), 0.75 (0.74 to 0.77) and 0.78 (0.75 to 0.81), respectively. Marker rs6841473 (EDNRA) modified the association between smoking and left carotid IMT in blacks (p=2.79×10(-5)). In addition, gene-based analysis demonstrated that EDNRA and ZHX2 were associated with left carotid IMT in the white and overall participants, respectively, while PINX1 was associated with right carotid IMT in both blacks and whites.

CONCLUSION

We identified two novel markers that were associated with IMT in both blacks and whites. One gene-smoking interaction was identified in blacks only. Three genes showed gene-based associations with IMT levels. However, genetic markers with small effects may have been missed due to the limited number of black participants.

Posttraumatic stress disorder, combat exposure, and carotid intima-media thickness in male twins

Posttraumatic stress disorder (PTSD) is associated with an increased risk of ischemic heart disease, though the pathophysiologic mechanisms remain unclear. Carotid artery intima-media thickness (CIMT) is a measure of subclinical atherosclerosis. We examined whether PTSD and combat exposure were associated with CIMT in Vietnam War-era twins after controlling for shared genetic and childhood factors. Between 2002 and 2010, we studied 465 middle-aged twins from the Vietnam Era Twin Registry who were free from cardiovascular disease. PTSD was diagnosed using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and CIMT was measured by ultrasound. Mixed-effects regression models were used to examine individual, between-pair, and within-pair associations. Approximately 13% of participants met the criteria for PTSD, and 45% served in the Vietnam Theater. PTSD was associated with 32.7 μm higher CIMT (95% confidence interval (CI): 0.9, 64.5) after adjustment for confounders. The average CIMT for the pair increased by 59.7 μm for each additional twin with PTSD (95% CI: 15.9, 104.2). We found no significant within-pair differences in CIMT when comparing PTSD-discordant co-twins. Results for combat exposure were similar, but its association with CIMT weakened after adjustment for PTSD (95% CI: 7.0, 45.3). Among Vietnam War-era veterans, combat exposure and PTSD are associated with CIMT, though the associations are largely mediated by shared childhood factors.

Heritability of arterial stiffness and carotid intima-media thickness: an Italian twin study

BACKGROUND AND AIMS

Carotid intima-media thickness (IMT) and arterial stiffness parameters, including aortic augmentation index (AIx) and pulse wave velocity (PWV), are independent predictors of stroke and cardiovascular disease. Genetic effects on these traits were never explored in a Mediterranean country. The present study aims to quantify the contribution of genes, environment and age to carotid IMT and aortic Aix and PWV.

METHODS AND RESULTS

The twin design was used. A total of 348 adult twins from the Italian Twin Register underwent measurements of carotid IMT and aortic PWV and AIx in three university hospitals located in Rome, Padua and Perugia. Carotid IMT was measured by B-mode ultrasound, aortic PWV and AIx by Arteriograph. Genetic modelling was performed to decompose total variance of traits into genetic, shared and unshared environmental and age components. For each phenotype, the best-fitting model included additive genetic, unshared environmental and age effects. For IMT, heritability was 0.32 (95% confidence interval (CI): 0.25-0.38), unshared environmental component was 0.25 (0.18-0.32) and age contribution was 0.44 (0.39-0.49). For AIx and PWV, heritabilities were 0.42 (0.29-0.55) and 0.49 (0.35-0.62), unshared environmental components were 0.31 (0.22-0.44) and 0.37 (0.26-0.51) and age contributions were 0.27 (0.16-0.39) and 0.14 (0.06-0.24), respectively.

CONCLUSION

This study shows substantial genetic and unshared environmental influences on carotid intima-media thickness and arterial stiffness and confirms the relevant role of age in the aetiology of these traits. Further support is provided for prevention and health promotion strategies based on modifiable factors.

Association between ideal cardiovascular health and carotid intima-media thickness: a twin study

Background

The American Heart Association (AHA) recently developed the Cardiovascular Health Index (CVHI), a health metric consisting of 7 modifiable risk factors. The relationship of the CVHI with preclinical markers, such as carotid intima‐media thickness (CIMT) has not been assessed.

Methods

We examined 490 male monozygotic and dizygotic twins without overt cardiovascular disease. CIMT was measured using B‐mode ultrasonography. Each of the 7 CVHI components (blood pressure, fasting glucose, total cholesterol, body mass index, physical activity, healthy diet, and smoking) was given a point score of 0, 1, or 2 to represent poor, intermediate, or ideal health, respectively. A CVHI summation score was computed (range 0 to 14) and categorized as inadequate (0 to 4), average (5 to 9), or optimum (10 to 14) cardiovascular health. Mixed‐model regression was used to examine the association of the CVHI with CIMT.

Results

The mean age of the twins was 55.4 years, and 61% were monozygotic. The mean CIMT was 0.75 (±0.11) mm and the mean CVHI score was 7.7 (±2.1). There was an inverse correlation between CVHI and CIMT (Spearman r=−0.22, P<0.01). For every 5‐unit increase in overall CVHI score (indicating better cardiovascular health category), CIMT decreased by 0.045 mm (P<0.001) after adjusting for demographic variables and other confounders. Within monozygotic twin pairs, a 5‐unit increment in CVHI score was associated with a 0.05 mm lower CIMT (P<0.001).

Conclusions

The CVHI is independently associated with CIMT and the association is not confounded by shared genetic and other familial factors.

The genetic basis for survivorship in coronary artery disease

Survivorship is a trait characterized by endurance and virility in the face of hardship. It is largely considered a psychosocial attribute developed during fatal conditions, rather than a biological trait for robustness in the context of complex, age-dependent diseases like coronary artery disease (CAD). The purpose of this paper is to present the novel phenotype, survivorship in CAD as an observed survival advantage concurrent with clinically significant CAD. We present a model for characterizing survivorship in CAD and its relationships with overlapping time- and clinically-related phenotypes. We offer an optimal measurement interval for investigating survivorship in CAD. We hypothesize genetic contributions to this construct and review the literature for evidence of genetic contribution to overlapping phenotypes in support of our hypothesis. We also present preliminary evidence of genetic effects on survival in people with clinically significant CAD from a primary case-control study of symptomatic coronary disease. Identifying gene variants that confer improved survival in the context of clinically appreciable CAD may improve our understanding of cardioprotective mechanisms acting at the gene level and potentially impact patients clinically in the future. Further, characterizing other survival-variant genetic effects may improve signal-to-noise ratio in detecting gene associations for CAD.

New quantitative trait loci for carotid atherosclerosis identified in an intercross derived from apolipoprotein E-deficient mouse strains

Carotid atherosclerosis is the primary cause of ischemic stroke. To identify genetic factors contributing to carotid atherosclerosis, we performed quantitative trait locus (QTL) analysis using female mice derived from an intercross between C57BL/6J (B6) and BALB/cJ (BALB) apolipoprotein E (Apoe^−/−) mice. We started 266 F₂ mice on a Western diet at 6 wk of age and fed them the diet for 12 wk. Atherosclerotic lesions in the left carotid bifurcation and plasma lipid levels were measured. We genotyped 130 microsatellite markers across the entire genome. Three significant QTLs, Cath1 on chromosome (Chr) 12, Cath2 on Chr5, and Cath3 on Chr13, and four suggestive QTLs on Chr6, Chr9, Chr17, and Chr18 were identified for carotid lesions. The Chr6 locus replicated a suggestive QTL and was named Cath4. Six QTLs for HDL, three QTLs for non-HDL cholesterol, and three QTLs for triglyceride were found. Of these, a significant QTL for non-HDL on Chr1 at 60.3 cM, named Nhdl13, and a suggestive QTL for HDL on ChrX were new. A significant locus for HDL (Hdlq5) was overlapping with a suggestive locus for carotid lesions on Chr9. A significant correlation between carotid lesion sizes and HDL cholesterol levels was observed in the F₂ population (R = −0.153, P = 0.0133). Thus, we have identified several new QTLs for carotid atherosclerosis and the locus on Chr9 may exert effect through interactions with HDL.

Leukotriene A4 hydrolase haplotype, diet and atherosclerosis: a twin study

OBJECTIVE

Atherosclerosis is an inflammatory process resulting from the interaction between genetic and environmental factors. Leukotrienes are inflammatory mediators generated from arachidonic acid, and genetic polymorphisms involved in leukotriene metabolism are implicated in atherosclerosis. The objectives of this study are to examine whether genetic variants in key leukotriene enzymes are associated with atherosclerosis, and whether dietary intake of competing leukotriene substrates modifies the effect of leukotriene variants on atherosclerosis.

METHODS

Atherosclerosis was assessed by common carotid intima-media thickness (IMT) using ultrasound. Sequence variants within arachidonate 5-lipoxygenase activating protein (ALOX5AP) and leukotriene A4 hydrolase (LTA4H) genes were analyzed with 32 single nucleotide polymorphisms (SNPs) in 169 Caucasian twin pairs from the Vietnam Era Twin Registry. The associations between genetic polymorphisms and carotid atherosclerosis, and gene × diet interactions were examined by generalized estimating equation controlling for potential confounders.

RESULTS

A six-SNP haplotype in LTA4H, designated HapE, was significantly associated with carotid IMT after adjusting for known coronary risk factors. Twins carrying HapE had a much lower IMT compared to twins not carrying (695 μm vs. 750 μm, p = 0.0007). Moreover, dietary intake of polyunsaturated fatty acids strongly augmented the cardioprotective effect of HapE among those with this haplotype but not those without, suggesting a haplotype × diet interaction (interaction P(HapE×n-3) = 0.03, P(HapE×n-6) = 0.015).

CONCLUSION

We identified a novel leukotriene haplotype that appears to be protective toward subclinical atherosclerosis. This association is modified by dietary intake of polyunsaturated fatty acids.

MAOA promoter methylation and susceptibility to carotid atherosclerosis: role of familial factors in a monozygotic twin sample

BACKGROUND

Atherosclerosis is a complex process involving both genetic and epigenetic factors. The monoamine oxidase A (MAOA) gene regulates the metabolism of key neurotransmitters and has been associated with cardiovascular risk factors. This study investigates whether MAOA promoter methylation is associated with atherosclerosis, and whether this association is confounded by familial factors in a monozygotic (MZ) twin sample.

METHODS

We studied 84 monozygotic (MZ) twin pairs drawn from the Vietnam Era Twin Registry. Carotid intima-media thickness (IMT) was measured by ultrasound. DNA methylation in the MAOA promoter region was quantified by bisulfite pyrosequencing using genomic DNA isolated from peripheral blood leukocytes. The association between DNA methylation and IMT was first examined by generalized estimating equation, followed by matched pair analyses to determine whether the association was confounded by familial factors.

RESULTS

When twins were analyzed as individuals, increased methylation level was associated with decreased IMT at four of the seven studied CpG sites. However, this association substantially reduced in the matched pair analyses. Further adjustment for MAOA genotype also considerably attenuated this association.

CONCLUSIONS

The association between MAOA promoter methylation and carotid IMT is largely explained by familial factors shared by the twins. Because twins reared together share early life experience, which may leave a long-lasting epigenetic mark, aberrant MAOA methylation may represent an early biomarker for unhealthy familial environment. Clarification of familial factors associated with DNA methylation and early atherosclerosis will provide important information to uncover clinical correlates of disease.

Non-invasive vessel examinations in carriers of LDL-receptor defective gene versus non-carriers with newly detected asymptomatic severe hypercholesterolemia

The results of the research of early vascular alterations in LDL-R carriers in comparison with those in non-carriers with severe hypercholesterolemia are controversial.

AIM

To investigate the difference between severe hypercholesterolemia patients that carry LDL-R defective gene and those that do not have it, in their functional (flow-mediated vasodilation) and structural (intima-media thickness of carotid artery and ankle-brachial index) characteristics of arterial wall.

PATIENTS AND METHODS

The study included 120 hypercholesterolemic patients. Biochemistry parameters were studied by routine methods. The flow-mediated vasodilation (%FMD), ankle-brachial index (ABI) and intima-media thickness (IMT) of common carotid artery were determined using Hewlett Packard Sonos 5 500; MedicaSoft. IMT.lab was the software programme used in the study.

RESULTS

There was no significant difference between the groups with respect to total cholesterol, LDL, HDL, Apo-B, Apo-A1, cellular adhesion molecules (sICAM-1, sVCAM-1, sP- and sE-selectine). The Apo-B/Apo A1 index differed significantly (t = 11.23, p < 0.001) between the two groups; there was difference even after adjustment for age. There was no significant difference in the endothelial dependent and independent vasodilatation between the examined groups (p > 0.05). We found a significantly greater carotid IMT and lower ABI in the carriers than the respective parameters in the non-carriers. This significant difference was confirmed after adjustment for age.

CONCLUSION

Our data show that LDL-R carriers have a higher carotid IMT and lower ABI than non-carriers, whereas no difference between the groups was found with respect to the level of lipid parameters and %FMD.

A candidate gene study revealed sex-specific association between the OLR1 gene and carotid plaque

BACKGROUND AND PURPOSE

Sex differences have been recognized in stroke risk; however, the sex-dependent genetic contribution to stroke is unclear. We sought to examine the sex-dependent associations between genes involved in lipid metabolism and carotid atherosclerotic plaque, a subclinical precursor of stroke.

METHODS

For the Genetic Determinant of Subclinical Carotid Disease study, 287 Dominicans ascertained through the Northern Manhattan Study were examined for carotid plaque using high-resolution ultrasound. Sixty-four single nucleotide polymorphisms (SNPs) in 11 lipid-related genes were genotyped. Plaque presence and plaque subphenotypes, including multiple, thick, irregular, and calcified plaque, were analyzed. First, the interaction between each SNP and sex was evaluated for association with each plaque phenotype using multiple logistic regression and controlling for age, smoking, and the main effects of sex and SNP. For SNPs with suggestive evidence for interaction with sex (P<0.1 for the interaction term), stratification analysis by sex was performed to evaluate the sex-specific association between the SNP and plaque phenotypes.

RESULTS

The most compelling finding is with the missense SNP rs11053646 (K167N) in the OLR1 gene, which encodes lectin-like oxidized low-density lipoprotein receptor. Stratification analysis revealed a strong association between rs11053646 and all plaque phenotypes in women (OR, 2.44 to 5.86; P=0.0003 to 0.0081) but not in men (OR, 0.85 to 1.22; P=0.77 to 0.92).

CONCLUSIONS

Genetic variation in genes involved in lipid metabolism may have sex-dependent effects on carotid plaque burden. Our findings provide a plausible biological basis underlying the sex difference in cardiovascular risk.

Genomewide linkage and peakwide association analyses of carotid plaque in Caribbean Hispanics

BACKGROUND AND PURPOSE

Atherosclerosis is a complex subclinical cardiovascular disorder with a substantial genetic component. This study sought to identify genetic loci influencing carotid plaque in 2 independent samples.

METHODS

B-mode ultrasound was performed to determine the presence and area of carotid plaque. Variance components analysis was used to test for linkage using 383 autosomal microsatellite markers in 1308 subjects from 100 Dominican families. Multiple linear and logistic regression models were used to investigate the association between plaque traits and 18,904 single nucleotide polymorphisms under the 1-logarithm of odds unit down regions of linkage peaks in an independent community-based data set (N = 941, 41% Dominicans) from the Northern Manhattan Study.

RESULTS

After adjustment for age, hypertension, diabetes mellitus, cigarette pack-years, body mass index, and waist-to-hip ratio, significant heritability was detected for plaque presence (h² = 0.50 ± 0.14, P < 0.0001) and plaque area (h²=0.17 ± 0.04, P < 0.0001). Quantitative and dichotomous trait linkage analyses obtained similar results and identified 4 regions with multipoint logarithm of odds scores ≥ 2.00 on 7q36, 11p15, 14q32, and 15q23. In the association analysis of the 4 linkage peaks, several single nucleotide polymorphisms in or near SOX6, FSD2, AP3S2, EFTUD1, and MYOD1 were associated with carotid plaque traits with a nominal P ≤ 0.0005 in the Northern Manhattan Study data set and with a P ≤ 0.01 in Northern Manhattan Study Dominican subset.

CONCLUSIONS

Carotid plaque has considerable heritability and may be influenced by loci on chromosomes 11p15, 14q32, and 15q23. The SOX6 gene within the bone morphogenic protein pathway could be a candidate for carotid plaque. Larger independent studies are needed to validate these findings.

Cross-sectional analysis of baseline data to identify the major determinants of carotid intima-media thickness in a European population: the IMPROVE study

AIMS

The 'IMPROVE study' was designed to investigate whether cross-sectional carotid artery intima-media thickness (IMT) and overall IMT progression are predictors of new vascular events in European individuals at high risk of cardiovascular diseases. This paper reports the results of the baseline analyses aimed at identifying the major determinants of increased carotid IMT (C-IMT).

METHODS AND RESULTS

IMPROVE is a prospective, multicentre, longitudinal, observational study. A total of 3711 subjects (age range 54-79 years) with at least three vascular risk factors (VRFs) were recruited in seven centres in Finland, France, Italy, the Netherlands, and Sweden. Collected variables included clinical, biochemical, genetic, socioeconomic, psychological, nutritional, and educational data, personal and family history of diseases, drug intake, and physical activity. By multiple linear regression analysis, C-IMT was positively associated with latitude, age, gender, pulse pressure, pack-years, and hypertension, and inversely with educational level (all P < 0.0001 for IMT(mean-max)). Latitude was the strongest independent determinant of C-IMT (partial r(2) for IMT(mean-max) = 0.109, P < 0.0001) and alone accounted for nearly half of the variation explained by the regression model (partial r(2) for IMT(mean-max) = 0.243, P < 0.0001). The geographical gradient for C-IMT paralleled the well-known north-to-south cardiovascular mortality gradient (r(2) for IMT(mean) = 0.96).

CONCLUSION

Latitude is an important determinant of C-IMT, which is not explained by between-country differences in established VRFs. Other unknown contributory mechanisms such as heritable, nutritional, or environmental factors may be important in the genesis of this geographical gradient.

The association of coronary artery calcification and carotid artery intima-media thickness with distinct, traditional coronary artery disease risk factors in asymptomatic adults

Coronary artery calcification (CAC) and common carotid artery intima-media thickness (CIMT) are measures of subclinical vascular disease. This 2000-2006 study aimed to characterize the associations among coronary artery disease risk factors, CAC quantity, and CIMT and to estimate shared genetic and environmental contributions to both CAC and CIMT among 478 asymptomatic Amish adults in Lancaster County, Pennsylvania. Heritability for CAC quantity and CIMT, adjusted for age and sex, was 0.42 (P = 0.0001) and 0.29 (P = 0.003), respectively. CAC quantity and CIMT were modestly correlated (adjusted r = 0.14, P = 0.003) but showed little evidence of shared genetic or environmental factors. However, significant genetic correlations were found for CAC quantity and total cholesterol (0.44 (standard error, 0.19); P = 0.03), for CAC quantity and low density lipoprotein cholesterol (0.55 (standard error, 0.17); P = 0.005), and for CIMT and waist circumference (0.58 (standard error, 0.25); P = 0.046), suggesting shared genes for these risk factors and measures of subclinical disease. Results suggest that some of the same genes influence variation in CAC and low density lipoprotein cholesterol, whereas a different set of genes influences variation in CIMT and waist circumference.

Depressive symptoms and heart rate variability: evidence for a shared genetic substrate in a study of twins

OBJECTIVE

To clarify the relationship between depression and heart rate variability (HRV) in a sample of twins. Reduced HRV, a measure of autonomic dysfunction, has been linked to depression but many studies have inadequately controlled for familial and environmental factors. Furthermore, little is known about whether depression and HRV share common genetic pathways.

METHODS

We performed power spectral analysis on 24-hour ambulatory electrocardiograms in 288 middle-aged male twins. Log-normalized ultra low, very low, low, high frequency, and total power were calculated. A lifetime history of major depressive disorder (MDD) was determined, using the Structured Clinical Interview for Psychiatry Disorders, and current depressive symptoms were measured with the Beck Depression Inventory. Mixed-effect regression models were used to account for intrapair variability and estimate within-pair effects at the same time controlling for potential confounders.

RESULTS

Both current depressive symptoms and a history of MDD were significantly associated with lower HRV. There was a graded effect, and power in each frequency band was 29% to 36% lower in the lowest band compared with the highest BDI category. All HRV measures except high frequency remained significantly associated with current depressive symptoms in multivariable analysis, but not with lifetime history of MDD. When analyses were stratified by zygosity, a significant within-pair association between BDI score and HRV was found in the dizygotic but not in the monozygotic twins, suggesting a genetic influence on the association.

CONCLUSIONS

A shared, genetically influenced biological pathway underlies the association between depression and lower HRV. These two phenotypes may be the expression of a generalized neurobiological perturbation.