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

Heritability of carotid intima-media thickness and inflammatory factors of atherosclerosis in a Chinese population

Carotid intima-media thickness (cIMT), a marker of subclinical atherosclerosis, has been found to be associated with incident stroke. High-sensitivity C-reactive protein (CRP) and fibrinogen have been demonstrated to be associated with atherosclerosis. Previous studies on heritability estimates of IMT, CRP, and fibrinogen among Chinese populations are limited. This study aims to estimate the heritability of these risk factors in residents who participated in the Taichung Community Health Study (TCHS) and their family members. A total of 2671 study subjects from 805 families were enrolled in the study, selected from a random sample of TCHS participants and their family members. CRP, and fibrinogen were obtained from each participant, and a questionnaire interview was conducted. cIMT was measured by high-resolution B-mode ultrasound and expressed as the mean of the maximum. Heritability estimates and the familial correlation of cIMT, CRP, and fibrinogen among family pairs were determined with SAGE software. With multivariate adjustments, significant heritability was found for cIMT (h2 = 0.26, P < 0.001), CRP (h2 = 0.34, P < 0.001), and fibrinogen (h2 = 0.48, P < 0.001). The intrafamilial correlation coefficients for the three indexes in the parent-offspring pairs were significant (P < 0.001) and ranged from 0.17 to 0.41. The full sibship correlations were also significant (P < 0.001) for the three indexes and ranged from 0.19 to 0.47. This study indicates that a moderate proportion of the variability in CRP, fibrinogen, and cIMT can be attributed to genetic factors in Chinese populations. The findings suggest that CRP is associated with cIMT, whereas no significant association exists between fibrinogen and cIMT.

Subclinical Atherosclerosis Progression in Low-Risk, Middle-Aged Adults: Carotid Leads Femoral in IMT Increase but Not in Plaque Formation

This study investigated subclinical atherosclerosis progression in low-risk, middle-aged adults (N = 141; a mean age of 49.6 ± 4.7 years) using a 5-year ultrasound follow-up. We compared the involvement of the carotid and femoral arteries.

METHODS

Clinical data, risk factors, carotid/femoral intima-media thickness (IMT), and plaque presence were analyzed.

RESULTS

Cardiovascular risk factors and scores increased significantly at follow-up. Both carotid and femoral mean IMT increased (p < 0.001). While plaque prevalence rose and was similar in both arteries (carotid: 4.8% to 17.9%, femoral: 3.6% to 17.7%, p < 0.001 for both), the progression of plaque burden was greater in femorals. Notably, the carotid mean IMT demonstrated a faster yearly progression rate compared to the mean femoral IMT. The prevalence of pathological nomogram-based mean IMT right or left was higher in the carotids (52.9% to 78.8%, p < 0.001) compared to femorals (23.2% to 44.7%, p < 0.001), with a significant increase at the end of follow-up in both territories.

CONCLUSIONS

This study demonstrates significant subclinical atherosclerosis progression in low-risk, middle-aged adults over 5 years. Carotid arteries showed a faster progression rate of mean IMT and a higher prevalence of pathological nomogram-based mean IMT compared to the femoral arteries. However, plaque burden was similar in both territories, with greater progression in femorals. Identifying carotid and femoral atherosclerosis burden may be a valuable tool for risk stratification in this population.

Skin Autofluorescence Mirrors Surrogate Parameters of Vascular Aging: An Enable Study

Advanced glycation end-products (AGEs) are implicated in vascular aging due to their pro-inflammatory properties. Skin autofluorescence (SAF) is a measure to estimate their deposition. It is an easily quantifiable marker that has been shown to correlate with cardiovascular risk and parameters of metabolic diseases. Herein, we compared skin autofluorescence with other techniques indicating increased cardiovascular diseases, namely, pulse wave velocity (PWVao) and intima–media thickness (IMT). We also studied the impacts of other parameters in deeply phenotyped cohorts of young, middle-aged, and older individuals. SAF, aortic PWVao, and IMT proved to be significantly correlated with each other and with age. However, based on a moderator analysis, we could not show that these associations were affected by age. Some specific parameters such as creatinine and CRP were found to be significantly associated with skin AGE values after adjusting for confounding variables. In conclusion, SAF is a simple screening tool for vascular health with comparable power to more elaborated technical tests.

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.

Genetic associations with carotid intima-media thickness link to atherosclerosis with sex-specific effects in sub-Saharan Africans

Atherosclerosis precedes the onset of clinical manifestations of cardiovascular diseases (CVDs). We used carotid intima-media thickness (cIMT) to investigate genetic susceptibility to atherosclerosis in 7894 unrelated adults (3963 women, 3931 men; 40 to 60 years) resident in four sub-Saharan African countries. cIMT was measured by ultrasound and genotyping was performed on the H3Africa SNP Array. Two new African-specific genome-wide significant loci for mean-max cIMT, SIRPA (p = 4.7E-08), and FBXL17 (p = 2.5E-08), were identified. Sex-stratified analysis revealed associations with one male-specific locus, SNX29 (p = 6.3E-09), and two female-specific loci, LARP6 (p = 2.4E-09) and PROK1 (p = 1.0E-08). We replicate previous cIMT associations with different lead SNPs in linkage disequilibrium with SNPs primarily identified in European populations. Our study find significant enrichment for genes involved in oestrogen response from female-specific signals. The genes identified show biological relevance to atherosclerosis and/or CVDs, sex-differences and transferability of signals from non-African studies.

Heritability of Cardiothoracic Ratio and Aortic Arch Calcification in Twins

Background and Objectives: Aortic arch calcification (AoAC) is associated with a variety of cardiovascular complications. The measurement and grading of AoAC using posteroanterior (PA) chest X-rays are well established. The cardiothoracic ratio (CTR) can be simultaneously measured with PA chest X-rays and used as an index of cardiomegaly. The genetic and environmental contributions to the degree of the AoAC and CTR are not well understood. The purpose of this study was to investigate the effect of genetics and environmental factors on the AoAC and CTR. Materials and Methods: A total of 684 twins from the South Korean twin registry (261 monozygotic, MZ and 81 dizygotic, DZ pairs; mean age 38.6 ± 7.9 years, male/female = 264/420) underwent PA chest X-rays. Cardiovascular risk factors and anthropometric data were also collected. The AoAC and CTR were measured and graded using a standardized method. A structural equation method was used to calculate the proportion of variance explained by genetic and environmental factors behind AoAC and CTR. Results: The within-pair differences were low regarding the grade of AoAC, with only a few twin pairs showing large intra-pair differences. We found that the thoracic width showed high heritability (0.67, 95% CI: 0.59–0.73, p = 1). Moderate heritability was detected regarding cardiac width (0.54, 95% CI: 0.45–0.62, p = 0.572) and CTR (0.54, 95% CI: 0.44–0.62, p = 0.701). Conclusions: The heritable component was significant regarding thoracic width, cardiac width, and the CTR.

Decreased heritability and emergence of novel genetic effects on pulse wave velocity from youth to young adulthood

Increased arterial stiffness measured by pulse wave velocity (PWV) is an important parameter in the assessment of cardiovascular risk. Our previous longitudinal study has demonstrated that carotid-distal PWV showed reasonable stability throughout youth and young adulthood. This stability might be driven by genetic factors that are expressed consistently over time. We aimed to illustrate the relative contributions of genetic and environmental factors to the stability of carotid-distal PWV from youth to young adulthood. We also examined potential ethnic differences. For this purpose, carotid-distal PWV was measured twice in 497 European American (EA) and African American (AA) twins, with an average interval time of 3 years. Twin modelling on PWV showed that heritability decreased over time (62–35%), with the nonshared environmental influences becoming larger. There was no correlation between the nonshared environmental factors on PWV measured at visit 1 and visit 2, with the phenotypic tracking correlation (r = 0.32) completely explained by shared genetic factors over time. Novel genetic influences were identified accounting for a significant part of the variance (19%) at the second measurement occasion. There was no evidence for ethnic differences. In summary, novel genetic effects appear during development into young adulthood and account for a considerable part of the variation in PWV. Environmental influences become larger with age for PWV.

Twin gestation and the burden of adult cardio-renal disease

The rate of twin births has increased by nearly 80% in recent decades largely due to advanced reproductive technologies. Twins are often born preterm and/or growth restricted which are independently associated with impaired renal and vascular development. Many preterm and twin infants are surviving into adulthood, albeit with an increased burden of chronic health conditions. Twinning as a research tool offers the unique opportunity to investigate the impact of genetics versus the environment on clinical outcomes. This educational review will focus on delineating our current understanding of the renal and cardiovascular development and long-term outcomes among twin born individuals. Specifically, existing literature regarding how twins differ in kidney size and function as well as vascular stiffness and hypertension profiles from singletons will be discussed. The unique situation of twin-twin transfusion syndrome which is associated with distinct short- and long-term cardio-renal disease will be highlighted. Ultimately, the ability to stratify risk of future cardio-renal disease at birth for infants born preterm and/or growth restricted, including twins, is important to guide clinical follow up. In addition, this early risk stratification could direct research efforts to better understand the mechanisms driving impaired organogenesis and allow for discovery of therapeutic interventions aimed at modifying disease progression and improving longevity in the most vulnerable infant subgroups.

The Italian Twin Registry: An Update at 18 Years From Its Inception

The Italian Twin Registry (ITR), established in 2001, is a population-based registry of voluntary twins. To date, it consists of approximately 29,000 twins who gave their consent to participate in the studies proposed by the ITR research group. The database comprises 11,500 monozygotic and 16,700 dizygotic twins resident throughout the country and belonging to a wide age range (from 0 to 95 years, mean 36.8 years). This article provides an overview of the recruitment strategies along with the major phenotypes investigated during an 18 years' research period. Over the years, several self-reported questionnaire data were collected, together with saliva/blood samples and measurements taken during in-person interviews or outpatient clinical examinations. Mental and behavioral phenotypes as well as atherosclerotic traits were studied in depth across different age groups. A birth cohort of twins was established and followed up. Novel research hypotheses are also being tested in ongoing projects. The ITR is involved in international studies in collaboration with other twin registries and represents a valuable resource for national and international research initiatives regarding a broad spectrum of health-related characteristics.

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.

Vascular function and stiffness: population epidemiology and concordance in Australian children aged 11-12 years and their parents

OBJECTIVES

To describe the epidemiology and parent-child concordance of vascular function in a population-based sample of Australian parent-child dyads at child age 11-12 years.

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 major Australian cities and eight regional towns or home visits, February 2015-March 2016.

PARTICIPANTS

Of all participating CheckPoint families (n=1874), 1840 children (49% girls) and 1802 parents (88% mothers) provided vascular function data. Survey weights and methods were applied to account for LSAC's complex sample design and clustering within postcodes and strata.

OUTCOME MEASURES

The SphygmoCor XCEL assessed vascular function, generating estimates of brachial and central systolic blood pressure and diastolic blood pressure, central pulse pressure, augmentation index and carotid-femoral pulse wave velocity. Pearson's correlation coefficients and multivariable linear regression models estimated parent-child concordance.

RESULTS

Hypertension was present in 3.9% of children and 9.0% of parents. Mean child and parent values for augmentation index were 4.5% (SD 11.6) and 21.3% (SD 12.3), respectively, and those for carotid-femoral pulse wave velocity were 4.48 m/s (SD 0.59) and 6.85 m/s (SD 1.14), respectively. Parent-child correlation for brachial systolic blood pressure was 0.20 (95% CI 0.15 to 0.24), brachial diastolic blood pressure 0.21 (95% CI 0.16 to 0.26), central systolic blood pressure 0.21 (95% CI 0.16 to 0.25), central diastolic blood pressure 0.21 (95% CI0.17 to 0.26), central pulse pressure 0.19 (95% CI 0.14 to 0.24), augmentation index 0.28 (95% CI 0.23 to 0.32) and pulse wave velocity 0.22 (95% CI 0.18 to 0.27).

CONCLUSIONS

We report Australian values for traditional and more novel vascular function markers, providing a reference for future population studies. Cross-generational concordance in multiple vascular function markers is already established by age 11-12 years, with mechanisms of heritability remaining to be explored.

Association of Endothelial Function with Parental Hypertension in Normotensive-Obese African-American Women: A Pilot Study

Obese African-American (AA) women are at high risk of hypertension (HT) and cardiovascular disease (CVD). Flow-mediated dilation (FMD) and arterial augmentation index (AI) are measures of endothelial function and arterial stiffness. Whether endothelial function and arterial stiffness predict risk of HT or CVD in obese African-American women with, versus without, parental histories of HT and whether aerobic exercise is an effective countermeasure remain unclear. The capacity for FMD is partly heritable. Therefore, we tested the hypotheses that less FMD and greater AI may be found in normotensive-obese, young-adult (18-26 year-old) AA women with hypertensive parents (n=10) than in a matched control group with normotensive parents (n=10) and that a single bout of aerobic exercise improves both endothelial function and arterial stiffness, with less improvement in the women with hypertensive parents. We studied each subject while at rest, 20 min before and 20 min after, 30 min of aerobic exercise. The exercise-induced changes and parental hypertension-related differences in AI were not significant. The exercise increased FMD in both of the groups with no significant difference in magnitude between the women with hypertensive and normotensive parents. FMD was significantly less in the women with hypertensive parents than in the women with normotensive parents after, but not before, the exercise (mean ±95% confidence interval of 11.3 ± 4.9% vs. 15.6 ± 4.9%, P=0.05). These findings suggest that a 30-min bout of aerobic exercise may improve FMD and unmask endothelial dysfunction in normotensive-obese, young-adult AA women with parental histories of HT. Future studies should determine whether regular aerobic exercise protects obese AA women from the endothelial dysfunction associated with diabetes and prevents CVD in this high-risk population.

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.

Genetic and environmental determinants of longitudinal stability of arterial stiffness and wave reflection: a twin study

BACKGROUND

We aimed at evaluating the impact of genetic and environmental factors on longitudinal changes in aortic pulse wave velocity (aPWV) and aortic augmentation index (aAIx).

METHOD

Three hundred and sixty-eight Italian and Hungarian adult twins (214 monozygotic, 154 dizygotic) underwent repeated evaluations of aPWV and aAIx (TensioMed Arteriograph). Within-individual/cross-wave, cross-twin/within-wave and cross-twin/cross-wave correlations were calculated; bivariate Cholesky models were fitted to calculate additive genetic (A), shared environmental (C) and unique environmental (E) components.

RESULTS

For both aPWV and aAIx, cross-twin correlations in monozygotic pairs (r between 0.35 and 0.56) were all significant and always higher than in dizygotic pairs, both at wave 1 and at wave 2. Heritability and unshared environmental proportion of variance at each wave were substantially time-invariant for aPWV (heritability 0.51, 95% CI 0.36-0.63 at wave 1; 0.49, 95% CI 0.34-0.62 at wave 2), whereas for aAIx, we observed a diminished genetic effect (heritability 0.57, 95% CI 0.45-0.67 at wave 1; 0.37, 95% CI 0.21-0.51 at wave 2). Overlapping genetic factors explained a high proportion (0.88, 95% CI 0.61-1.00) of longitudinal covariance for aPWV, and had a relatively lower impact on aAIx (0.55, 95% CI 0.35-0.70). Genetic correlations of aPWV (r = 0.64, 95% CI 0.42-0.85) and aAIx (r = 0.70, 95% CI 0.52-0.87) between waves were lower than 1, suggesting a potential contribution of novel genetic variance on arterial stiffening.

CONCLUSION

Changes in aPWV and aAIx over time are largely genetically determined. Our results might stimulate further studies on genetic and epigenetic factors influencing the process of vascular ageing.

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.

Genetic influence on femoral plaque and its relationship with carotid plaque: an international twin study

To disentangle genetic and environmental influences on the development of femoral plaques using a population of adult twins. To evaluate the potential role of shared genetic and environmental factors in the co-occurrence of femoral and carotid plaques. The sample included 566 twins belonging to 164 monozygotic (MZ) and 119 dizygotic (DZ) twin pairs, who underwent peripheral arterial assessment by B-mode ultrasound in different centers. The variance in femoral plaques onset was due to genetic factors and the remaining 50% was explained by common (15%) and unique (35%) environmental factors. Findings on sidedness and number of femoral plaques indicated that also these traits were mainly under genetic control. No effect of common environment was found on plaques composition, and variability of this trait was explained by genetics (64%) and unique environment (36%). Covariation between the liabilities to carotid and femoral plaques was mainly attributed to shared genes (77%), with the remaining 23% explained by individual-specific environmental factors shared by the two districts. Inter-individual differences in plaque onset as well as in their number, sidedness and composition are mainly genetic in origin. The results on the cooccurrence of carotid and femoral plaque underline the genetic role in atherogenesis.

Age-related Impairment of Vascular Structure and Functions

Among age-related diseases, cardiovascular and cerebrovascular diseases are major causes of death. Vascular dysfunction is a key characteristic of these diseases wherein age is an independent and essential risk factor. The present work will review morphological alterations of aging vessels in-depth, which includes the discussion of age-related microvessel loss and changes to vasculature involving the capillary basement membrane, intima, media, and adventitia as well as the accompanying vascular dysfunctions arising from these alterations.

Vascular Smooth Muscle Cells and Arterial Stiffening: Relevance in Development, Aging, and Disease

The cushioning function of large arteries encompasses distension during systole and recoil during diastole which transforms pulsatile flow into a steady flow in the microcirculation. Arterial stiffness, the inverse of distensibility, has been implicated in various etiologies of chronic common and monogenic cardiovascular diseases and is a major cause of morbidity and mortality globally. The first components that contribute to arterial stiffening are extracellular matrix (ECM) proteins that support the mechanical load, while the second important components are vascular smooth muscle cells (VSMCs), which not only regulate actomyosin interactions for contraction but mediate also mechanotransduction in cell-ECM homeostasis. Eventually, VSMC plasticity and signaling in both conductance and resistance arteries are highly relevant to the physiology of normal and early vascular aging. This review summarizes current concepts of central pressure and tensile pulsatile circumferential stress as key mechanical determinants of arterial wall remodeling, cell-ECM interactions depending mainly on the architecture of cytoskeletal proteins and focal adhesion, the large/small arteries cross-talk that gives rise to target organ damage, and inflammatory pathways leading to calcification or atherosclerosis. We further speculate on the contribution of cellular stiffness along the arterial tree to vascular wall stiffness. In addition, this review provides the latest advances in the identification of gene variants affecting arterial stiffening. Now that important hemodynamic and molecular mechanisms of arterial stiffness have been elucidated, and the complex interplay between ECM, cells, and sensors identified, further research should study their potential to halt or to reverse the development of arterial stiffness.

Heritability of the femoral intima media thickness

BACKGROUND

The measurement of femoral intima-media thickness (IMT) is underutilized in the clinical practice, although it is a surrogate marker of cardiovascular disease.

MATERIALS AND METHODS

388 Hungarian and Italian twins (121 monozygotic, 73 dizygotic pairs) underwent bilateral B-mode sonography of femoral arteries. IMT was measured by semiautomated software, where available, or by calipers.

RESULTS

Within-pair correlation in monozygotic twins was higher than in dizygotics for each parameter. Age-, sex- and country-adjusted genetic effect accounted for 43.9% (95% confidence interval, CI 21.3%-65.2%) and 47.2% (95% CI, 31.4%-62.6%) of the variance of common and superficial femoral artery IMT, respectively, and unshared environmental effect for 56.1% (95% CI 34.6%-78.5%) and 52.8% (95% CI, 37.2%-68.5%). These results did not change significantly after correcting for body mass index or central systolic blood pressure.

CONCLUSIONS

Genetic factors have a moderate role in the determination of common and superficial femoral IMT; however, the influence of environmental (lifestyle) factors remains still relevant. Environmental factors may have a role in influencing the genetic predisposition for femoral vascular hypertrophy.

Femoral Artery Ultrasound Examination

We compared intima–media thickness (IMT) and the prevalence of plaques in the common carotid artery (CCA) and common femoral artery (CFA) in apparently healthy participants. This multicenter study included 322 participants (59.9% female; age 20-78 years, mean 52.1 ± 15.3 years) who underwent Echo-color Doppler examination of the CCA and CFA bilaterally. Prevalence and composition of plaque were recorded. A significant ( P < .01) difference between mean CCA-IMT and mean CFA-IMT was detected (0.70 vs 0.73 mm). Plaque prevalence was significantly higher in the CFA compared to the CCA (40.7% vs 30.4%). Atherosclerotic plaques were found in both CFA and CCA in 46% of the cases, solely in CFA in 38%, and in CCA alone in 17%. The observed difference in plaque prevalence was even greater when only fibrolipid isolated plaques were considered (CFA 39.4% vs CCA 22.1%). In a healthy general population, atherosclerotic plaques were present in the CFA but not in the CCA in over one-third of the cases. Further studies must confirm whether ultrasonography of the CFA might be introduced in the screening protocols for cardiovascular risk assessment.

Association of Parental Hypertension With Arterial Stiffness in Nonhypertensive Offspring: The Framingham Heart Study

High arterial stiffness seems to be causally involved in the pathogenesis of hypertension. We tested the hypothesis that offspring of parents with hypertension may display higher arterial stiffness before clinically manifest hypertension, given that hypertension is a heritable condition. We compared arterial tonometry measures in a sample of 1564 nonhypertensive Framingham Heart Study third-generation cohort participants (mean age: 38 years; 55% women) whose parents were enrolled in the Framingham Offspring Study. A total of 468, 715, and 381 participants had 0 (referent), 1, and 2 parents with hypertension. Parental hypertension was associated with greater offspring mean arterial pressure (multivariable-adjusted estimate=2.9 mm Hg; 95% confidence interval, 1.9-3.9, and 4.2 mm Hg; 95% confidence interval, 2.9-5.5, for 1 and 2 parents with hypertension, respectively; P<0.001 for both) and with greater forward pressure wave amplitude (1.6 mm Hg; 95% confidence interval, 0.6-2.7, and 1.9 mm Hg; 95% confidence interval, 0.6-3.2, for 1 and 2 parents with hypertension, respectively; P=0.003 for both). Carotid-femoral pulse wave velocity and augmentation index displayed similar dose-dependent relations with parental hypertension in sex-, age-, and height-adjusted models, but associations were attenuated on further adjustment. Offspring with at least 1 parent in the upper quartile of augmentation index and carotid-femoral pulse wave velocity had significantly higher values themselves (P≤0.02). In conclusion, in this community-based sample of young, nonhypertensive adults, we observed greater arterial stiffness in offspring of parents with hypertension. These observations are consistent with higher vascular stiffness at an early stage in the pathogenesis of hypertension.

Predictive value of the augmentation index derived vascular age in patients with newly diagnosed atherosclerosis

Early detection of atherosclerosis, i.e., in occupational health screening programs could reduce the rate of cardiovascular events in the working population. Changes of the augmentation index (AIX) correlate with changes of the arterial stiffness induced by aging, atherosclerosis, or arterial hypertension and have a prognostic value for cardiovascular events. Their diagnostic yield should be increased by normalizing the AIX to age, in terms of a calculating the vascular age (VA). In this pilot study, 30 patients (mean age 65.3 ± 8.8 years, 21 male) with suspected coronary heart disease underwent a duplex ultrasound of the carotid arteries and a measurement of the ankle brachial index in addition to the coronary angiography. The AIX was recorded with a portable device (Vascular Explorer), and the VA was calculated. Atherosclerosis was found in 24 patients. They were older than the patients without atherosclerosis, but there was no age dependency found for the distribution pattern or severity of atherosclerosis. In patients with findings of atherosclerosis, the calculated VA was higher than the chronological age, and these differences were significant in patients below 65 years of age. Comparing patients in higher blood pressure classes with patients in lower classes, significantly higher AIX, VA, and differences to the chronological age were found. The VA, deduced from the noninvasively obtained AIX, is a promising candidate for screening programs for atherosclerosis, i.e., in occupational health screening programs.

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.

Examination of the Relationship between Oral Health and Arterial Sclerosis without Genetic Confounding through the Study of Older Japanese Twins

OBJECTIVE

Although researchers have recently demonstrated a relationship between oral health and arterial sclerosis, the genetic contribution to this relationship has been ignored even though genetic factors are expected to have some effect on various diseases. The aim of this study was to evaluate oral health as a significant risk factor related to arterial sclerosis after eliminating genetic confounding through study of older Japanese twins.

SUBJECTS AND METHODS

Medical and dental surveys were conducted individually for 106 Japanese twin pairs over the age of 50 years. Maximal carotid intima-media thickness (IMT-Cmax) was measured as a surrogate marker of arterial sclerosis. IMT-Cmax > 1.0 mm was diagnosed as arterial sclerosis. All of the twins were examined for the number of remaining teeth, masticatory performance, and periodontal status. We evaluated each measurement related with IMT-Cmax and arterial sclerosis using generalized estimating equations analysis adjusted for potential risk factors. For non-smoking monozygotic twins, a regression analysis using a "between within" model was conducted to evaluate the relationship between IMT-Cmax and the number of teeth as the environmental factor controlling genetic and familial confounding.

RESULTS

We examined 91 monozygotic and 15 dizygotic twin pairs (males: 42, females: 64) with a mean (± standard deviation) age of 67.4 ± 10.0 years. Out of all of the oral health-related measurements collected, only the number of teeth was significantly related to arterial sclerosis (odds ratio: 0.72, 95% confidence interval: 0.52-0.99 per five teeth). Regression analysis showed a significant association between the IMT-Cmax and the number of teeth as an environmental factor (p = 0.037).

CONCLUSIONS

Analysis of monozygotic twins older than 50 years of age showed that having fewer teeth could be a significant environmental factor related to arterial sclerosis, even after controlling for genetic and familial confounding.

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.