Heritability of left ventricular mass in a large cohort of twins

Association of the rs3039851 Insertion/Deletion in the Gene PPP3R1, Which Encodes the Regulatory Calcineurin Subunit B Type 1, with Left Ventricular Mass in Polish Full-Term Newborns

BACKGROUND

The five base-pair (bp) insertion/deletion (rs3039851) polymorphism in the PPP3R1 gene, which encodes calcineurin subunit B type 1, has been found to be associated with left ventricular hypertrophy (LVH) in hypertensive patients and in athletes. The aim of this study is to analyze the possible association between PPP3R1:rs3039851 polymorphism and left ventricular mass (LVM) in full-term healthy newborns.

METHODS

The study group consisted of 162 consecutive, full-term, healthy newborns. Two-dimensional M-mode echocardiography was used to assess LVM. The PPP3R1:rs3039851 polymorphism was identified by PCR-RFLP in genomic DNA extracted from cord blood leukocytes.

RESULTS

No significant differences were found between newborns homozygous for the reference allele (5I/5I, n = 135) and newborns carrying at least one 5D allele (n = 27) for LVM standardized for body mass, body length or body surface area (LVM/BM, LVM/BL or LVM/BSA, respectively). However, the frequency of PPP3R1:rs3039851 genotypes with a 5D allele (5I/5D + 5D/5D) among newborns with the largest LVM/BM or LVM/BSA (upper tertile) was statistically significantly higher compared with the prevalence in individuals with the lowest values of both indices (lower tertile).

CONCLUSIONS

Our results suggest that the PPP3R1:rs3039851 polymorphism may contribute to subtle variation in left ventricular mass at birth.

Left Ventricular Adaptation to Exercise Training via Magnetic Resonance Imaging: Studies of Twin Responses to Understand Exercise THerapy

PURPOSE

Changes in left ventricular mass (LVM) and end-diastolic volume (EDV) in response to exercise training are important determinants of functional capacity in health and disease, but the impact of different exercise modalities remains unclear.

METHODS

Using a randomized crossover design we studied the impact of resistance (RES) and endurance (END) training using cardiac magnetic resonance imaging in previously untrained monozygotic (MZ) and dizygotic (DZ) twin pairs (n = 72; 22 MZ pairs, 14 DZ same-sex pairs; 26.1 ± 5.4 yr). Twins, as pairs, undertook 3 months of RES and 3 months of END training (order randomized), separated by a 3-month washout.

RESULTS

Group results revealed that END increased LVM (P < 0.001) and EDV (P = 0.007), whereas RES did not (P > 0.05). A higher proportion of individuals responded to END than RES for LVM (72% vs 38%, P < 0.001) and EDV (67% vs 40%, P = 0.003). Baseline cross-sectional intraclass correlations were higher for MZ than DZ twin pairs for all variables (e.g., LVM heritability = 0.42), but no significant correlations were apparent between pairs for change in any variable in response to either RES or END (P > 0.05).

CONCLUSIONS

Our findings indicate that cardiac adaptation in response to exercise is modality-specific and that low responders to one mode of exercise can be high responders to an alternative. Heritability estimates based on cross-sectional data, which suggested a genetic contribution to LVM, do not accord with estimates based on training effects, which indicated limited genetic impact on adaptation in this 3-month study of exercise training. This study has implications for understanding the physiological and health impacts of typically used exercise modalities on cardiac adaptation in previously untrained individuals.

Whole-Exome Sequencing and hiPSC Cardiomyocyte Models Identify MYRIP, TRAPPC11, and SLC27A6 of Potential Importance to Left Ventricular Hypertrophy in an African Ancestry Population

Background: Indices of left ventricular (LV) structure and geometry represent useful intermediate phenotypes related to LV hypertrophy (LVH), a predictor of cardiovascular (CV) disease (CVD) outcomes.

Methods and Results: We conducted an exome-wide association study of LV mass (LVM) adjusted to height^2.7, LV internal diastolic dimension (LVIDD), and relative wall thickness (RWT) among 1,364 participants of African ancestry (AAs) in the Hypertension Genetic Epidemiology Network (HyperGEN). Both single-variant and gene-based sequence kernel association tests were performed to examine whether common and rare coding variants contribute to variation in echocardiographic traits in AAs. We then used a data-driven procedure to prioritize and select genes for functional validation using a human induced pluripotent stem cell cardiomyocyte (hiPSC-CM) model. Three genes [myosin VIIA and Rab interacting protein (MYRIP), trafficking protein particle complex 11 (TRAPPC11), and solute carrier family 27 member 6 (SLC27A6)] were prioritized based on statistical significance, variant functional annotations, gene expression in the hiPSC-CM model, and prior biological evidence and were subsequently knocked down in the hiPSC-CM model. Expression profiling of hypertrophic gene markers in the knockdowns suggested a decrease in hypertrophic expression profiles. MYRIP knockdowns showed a significant decrease in atrial natriuretic factor (NPPA) and brain natriuretic peptide (NPPB) expression. Knockdowns of the heart long chain fatty acid (FA) transporter SLC27A6 resulted in downregulated caveolin 3 (CAV3) expression, which has been linked to hypertrophic phenotypes in animal models. Finally, TRAPPC11 knockdown was linked to deficient calcium handling.

Conclusions: The three genes are biologically plausible candidates that provide new insight to hypertrophic pathways.

Association between insulin resistance and left ventricular hypertrophy in asymptomatic, Black, sub-Saharan African, hypertensive patients: a case-control study

Background

Conflicting information exists regarding the association between insulin resistance (IR) and left ventricular hypertrophy (LVH). We described the associations between obesity, fasting insulinemia, homeostasis model assessment of insulin resistance (HOMA-IR), and LVH in Black patients with essential hypertension.

Methods

A case–control study was conducted at the Centre Médical de Kinshasa (CMK), the Democratic Republic of the Congo, between January and December 2019. Cases and controls were hypertensive patients with and without LVH, respectively. The relationships between obesity indices, physical inactivity, glucose metabolism and lipid disorder parameters, and LVH were assessed using linear and logistic regression analyses in simple and univariate exploratory analyses, respectively. When differences were observed between LVH and independent variables, the effects of potential confounders were studied through the use of multiple linear regression and in conditional logistic regression in multivariate analyses. The coefficients of determination (R²), adjusted odds ratios (aORs), and their 95% confidence intervals (95% CIs) were calculated to determine associations between LVH and the independent variables.

Results

Eighty-eight LVH cases (52 men) were compared against 132 controls (81 men). Variation in left ventricular mass (LVM) could be predicted by the following variables: age (19%), duration of hypertension (31.3%), body mass index (BMI, 44.4%), waist circumference (WC, 42.5%), glycemia (20%), insulinemia (44.8%), and HOMA-IR (43.7%). Hypertension duration, BMI, insulinemia, and HOMA-IR explained 68.3% of LVM variability in the multiple linear regression analysis. In the logistic regression model, obesity increased the risk of LVH by threefold [aOR 2.8; 95% CI (1.06–7.4); p = 0.038], and IR increased the risk of LVH by eightfold [aOR 8.4; 95 (3.7–15.7); p < 0.001].

Conclusion

Obesity and IR appear to be the primary predictors of LVH in Black sub-Saharan African hypertensive patients. The comprehensive management of cardiovascular risk factors should be emphasized, with particular attention paid to obesity and IR. A prospective population-based study of Black sub-Saharan individuals that includes the use of serial imaging remains essential to better understand subclinical LV deterioration over time and to confirm the role played by IR in Black sub-Saharan individuals with hypertension.

Ethnic differences in childhood right and left cardiac structure and function assessed by cardiac magnetic resonance imaging

Ethnic differences in cardiovascular risk factors and disease are well-known and may originate in early-life. We examined the ethnic differences in cardiac structure and function in children using cardiac magnetic resonance imaging in a European migrant population, and whether any difference was explained by early life factors. We used a prospective population-based cohort study among 2317 children in Rotterdam, the Netherlands. We compared children from Dutch (73%), Cape Verdean (3.5%), Dutch Antillean (3.3%), Moroccan (6.1%), Surinamese-Creoles (3.9%), Surinamese-Hindustani (3.4%), and Turkish (6.4%) background. Main outcomes were cMRI-measured cardiac structures and function. Cardiac outcomes were standardized on body surface area. Cape Verdean, Surinamese-Hindustani, and Turkish children had smaller right ventricular end-diastolic volume and left ventricular end-diastolic volume relative to their body size than Dutch children (p < 0.05). These results were not fully explained by fetal and childhood factors. Right ventricular ejection fraction and left ventricular ejection fraction did not differ between ethnicities after adjustment for fetal and childhood factors.Conclusion: Right ventricular end-diastolic volume and left ventricular end-diastolic volume differ between ethnic subgroups in childhood, without affecting ejection fraction. Follow-up studies are needed to investigate whether these differences lead to ethnic differences in cardiac disease in adulthood. What is Known: • Ethnic differences in cardiovascular risk factors and disease are well-known and may originate in early-life. • The prevalence of cardiovascular disease differs between ethnic groups. What is New: • We examined ethnic differences in left and right cardiac structure and function in children using cMRI. • Right and left cardiac dimensions differ between ethnic groups in childhood and are only partly explained by fetal and childhood factors.

Exploring human trainability: Design and rationale of Studies of Twin Responses to Understand Exercise as a Therapy (STRUETH) study

Background

Exercise confers myriad health benefits and physical inactivity is a modifiable risk factor for many non-communicable chronic diseases. However, individual responsiveness to guideline-based exercise programs is idiosyncratic for health and fitness outcomes. It is not known whether the response of individuals to distinct exercise modalities tend to be concordant or whether there is a genetic contribution to variation in exercise responsiveness.

Methods/design

Healthy, young adult (16-40yrs) monozygotic (MZ) and dizygotic (DZ) twin pairs were recruited and randomly assigned to 3 months of endurance or resistance exercise training. Twin pairs trained together. After 3 months of training in their randomly assigned mode, a washout period of 3 months was observed before twin pairs crossed over to complete 3 months of the alternate exercise intervention. Measures of cardiac morphology and function, cerebrovascular function, cognitive performance, peripheral artery function, biochemistry, blood pressure, body composition, skeletal muscle strength and cardiopulmonary fitness were collected before and after each exercise intervention (i.e. at weeks 0, 12, 24 and 36).

Discussion

We adopted exercise modalities that produce distinct haemodynamic and physiological stimuli for physiological adaptation and recruited MZ and DZ twin pairs to address questions such as; do individuals exhibit concordant responses to distinct exercise modalities? and what is the genetic contribution to adaptation resulting from distinct training modalities? The results of this study will provide insight into the genetic and environmental contribution to exercise response to distinct modes of training, with implications for determining the optimal approaches to exercise prescription.

Left ventricular cardiac geometry and ambulatory blood pressure in children

Limited information is available regarding the relationship between ambulatory blood pressure monitoring (ABPM) and cardiac geometry in hypertensive children. ABPM and 2D-echocardiography were retrospectively reviewed in children and adolescents <21 years old with primary hypertension. A total of 119 participants (median age 15.0 [IQR 12, 16] years) with hypertension were included. Left ventricular hypertrophy was diagnosed in 39.5% of participants. Normal geometry was found in 47.1%, concentric remodeling (CR) in 13.4%, concentric hypertrophy (CH) in 15.1%, and eccentric hypertrophy (EH) in 24.4% of children. After adjustment for age, sex, and body mass index z-score, awake systolic blood pressure (BP) index (BPi) (OR 1.07, 95% CI: 1.001-1.14, P = 0.045), awake diastolic BPi (OR 1.04, 95% CI: 1.00-1.09, P = 0.048), awake systolic BP load (OR 1.02, 95% CI: 1.000-1.04, P = 0.047), and sleep systolic BP load (OR 1.02, 95% CI: 1.001-1.04, P = 0.03) were directly associated with CH. No ABPM parameters were significant predictors of EH. In conclusion, ABPM parameters were found to be independent predictors of cardiac geometry, specifically CH.

Genetically determined pattern of left ventricular function in normal and hypertensive hearts

We sought to assess the inheritance of left ventricular (LV) function using speckle-tracking echocardiography and the impact of hypertension on modifying the genetically determined pattern of contraction in a population of twins. We recruited 92 Caucasian twin pairs, including 74 hypertensive (HTN) siblings. Beyond standard echocardiographic protocol, a speckle-tracking analysis was performed, including global longitudinal strain (GLS). Systolic function, as assessed by ejection fraction, showed moderate heritability (61%); however, GLS showed higher and dominant heritability (75%). Heterogeneity models revealed that there were no differences between the HTN and non-HTN subjects regarding the heritability of GLS. However, the heritability estimates of diastolic function parameters, including early diastolic strain rate, were low. LV systolic biomechanics is highly heritable. GLS shows dominant heritability, despite the presence of early-stage hypertensive heart disease. Early diastolic parameters are rather determined by environmental factors. These findings suggest the presence of a genetic framework that conserves systolic function despite the expression of diastolic dysfunction and may underlie the phenotypic progression towards heart failure with preserved ejection fraction.

Sequencing of Linkage Region on Chromosome 12p11 Identifies PKP2 as a Candidate Gene for Left Ventricular Mass in Dominican Families

Increased left ventricular mass (LVM) is an intermediate phenotype for cardiovascular disease (CVD) and a predictor of stroke. Using families from the Dominican Republic, we have previously shown LVM to be heritable and found evidence for linkage to chromosome 12p11. Our current study aimed to further characterize the QTL by sequencing the 1 LOD unit down region in 10 families from the Dominican Republic with evidence for linkage to LVM. Within this region, we tested 5477 common variants [CVs; minor allele frequency (MAF) ≥5%] using the Quantitative Transmission-Disequilibrium Test (QTDT). Gene-based analyses were performed to test rare variants (RVs; MAF < 5%) in 181 genes using the family-based sequence kernel association test. A sample of 618 unrelated Dominicans from the Northern Manhattan Study (NOMAS) and 12 Dominican families with Exome Array data were used for replication analyses. The most strongly associated CV with evidence for replication was rs1046116 (Discovery families P = 9.0 × 10-4; NOMAS P = 0.03; replication families P = 0.46), a missense variant in PKP2 In nonsynonymous RV analyses, PKP2 was one of the most strongly associated genes (P = 0.05) with suggestive evidence for replication in NOMAS (P = 0.05). PKP2 encodes the plakophilin 2 protein and is a desmosomal gene implicated in arrythmogenic right ventricular cardiomyopathy and recently in arrhythmogenic left ventricular cardiomyopathy, which makes PKP2 an excellent candidate gene for LVM. In conclusion, sequencing of our previously reported QTL identified common and rare variants within PKP2 to be associated with LVM. Future studies are necessary to elucidate the role these variants play in influencing LVM.

Cardiac telomere length in heart development, function, and disease

Telomeres are repetitive nucleoprotein structures at chromosome ends, and a decrease in the number of these repeats, known as a reduction in telomere length (TL), triggers cellular senescence and apoptosis. Heart disease, the worldwide leading cause of death, often results from the loss of cardiac cells, which could be explained by decreases in TL. Due to the cell-specific regulation of TL, this review focuses on studies that have measured telomeres in heart cells and critically assesses the relationship between cardiac TL and heart function. There are several lines of evidence that have identified rapid changes in cardiac TL during the onset and progression of heart disease as well as at critical stages of development. There are also many factors, such as the loss of telomeric proteins, oxidative stress, and hypoxia, that decrease cardiac TL and heart function. In contrast, antioxidants, calorie restriction, and exercise can prevent both cardiac telomere attrition and the progression of heart disease. TL in the heart is also indicative of proliferative potential and could facilitate the identification of cells suitable for cardiac rejuvenation. Although these findings highlight the involvement of TL in heart function, there are important questions regarding the validity of animal models, as well as several confounding factors, that need to be considered when interpreting results and planning future research. With these in mind, elucidating the telomeric mechanisms involved in heart development and the transition to disease holds promise to prevent cardiac dysfunction and potentiate regeneration after injury.

Genetic Dissection of Cardiac Remodeling in an Isoproterenol-Induced Heart Failure Mouse Model

We aimed to understand the genetic control of cardiac remodeling using an isoproterenol-induced heart failure model in mice, which allowed control of confounding factors in an experimental setting. We characterized the changes in cardiac structure and function in response to chronic isoproterenol infusion using echocardiography in a panel of 104 inbred mouse strains. We showed that cardiac structure and function, whether under normal or stress conditions, has a strong genetic component, with heritability estimates of left ventricular mass between 61% and 81%. Association analyses of cardiac remodeling traits, corrected for population structure, body size and heart rate, revealed 17 genome-wide significant loci, including several loci containing previously implicated genes. Cardiac tissue gene expression profiling, expression quantitative trait loci, expression-phenotype correlation, and coding sequence variation analyses were performed to prioritize candidate genes and to generate hypotheses for downstream mechanistic studies. Using this approach, we have validated a novel gene, Myh14, as a negative regulator of ISO-induced left ventricular mass hypertrophy in an in vivo mouse model and demonstrated the up-regulation of immediate early gene Myc, fetal gene Nppb, and fibrosis gene Lgals3 in ISO-treated Myh14 deficient hearts compared to controls.

Heart failure is the most common cause of morbidity and mortality in the aging population. Previous large-scale human genome-wide association studies have yielded only a handful of genetic loci contributing to heart failure-related traits. Using a panel of diverse inbred mouse strains, treated with a β-adrenergic agonist isoproterenol to mimic the heart failure state, we sought to uncover the contribution of common genetic variation in heart failure. We found that heart failure has a strong genetic component. We successfully identified 17 genome-wide significant loci associated with indices of heart failure. We showed that genetic variation in a novel gene Myh14 affects heart failure by altering the mechanical responses of heart muscles to isoproterenol-induced stress. Follow-up studies of this gene and additional candidate genes and loci should reveal potential mechanisms by which genetic variations contribute to heart failure in the general human population. Such insights may lead to improved diagnosis and tailor treatment based on the genetic makeup of individuals in the population.

Cardiac morphology and function reference values derived from a large subset of healthy young Caucasian adults by magnetic resonance imaging

AIMS

Assessment of cardiac anatomy and function by cardiovascular magnetic resonance (CMR) is accurate and reproducible and is commonly performed to clarify borderline results obtained by other techniques. Normal reference values are lacking in a large sample of young healthy adults. As CMR is increasingly solicited to discriminate normality from equivocal disease in this population, we sought to determine reliable reference values.

METHODS AND RESULTS

A sample of 434 Caucasian adults aged 26 ± 4 years (45% male) without cardiovascular disease or risk factors (including obesity and smoking) underwent CMR. Blood pressure, electrocardiogram, and plasma markers (lipid profile, fasting glucose, troponin, and Nt-pro-BNP) were within normal limits and typical of a low-cardiometabolic-risk profile. End-diastolic (ED), end-systolic (ES), and stroke volumes were greater in men for left and right atria and ventricles. Left ventricular (LV) mass was higher in men. ED wall thickness of all segments was greater in men, whereas ES wall thickening (segmental function) was similar in both genders. After normalization to body surface area, all gender differences remained. Left and right ventricular volumes were lower, and left atrial volumes were higher in older individuals. In contrast, LV mass was not associated with age.

CONCLUSION

This is the first large database of reference ranges for ventricular and atrial functions, volumes, and mass in young Caucasian men and women devoid of cardiovascular disease and risk factors. These data will contribute to improving the accuracy of CMR interpretation for clinical and research applications.

Genetic influence on left ventricular structure and function: a Korean twin and family study

Genetic factors have been suggested to be one of the determinants of the variation of left ventricular (LV) structure and function. However, the heritability range of LV structure varies across studies and the influence of genetics on LV function is not well established, especially in Asian populations. Study subjects were 1,642 healthy Korean adults from 426 families, consisting of 298 pairs of monozygotic twins, 62 pairs of dizygotic twins, one set of triplets, 567 siblings, and 354 parents. LV structure and function were measured by M-mode and 2D echocardiography, and conventional and tissue Doppler imaging (TDI). Pairwise intra-class correlations for various familial relationships and heritability were estimated for LV structure and function. The heritability of LV mass, LV ejection fraction (LVEF), left atrial volume index, the ratio between early and late diastolic velocity of mitral inflow (E/A ratio), and the ratio between early diastolic velocity of mitral inflow and early diastolic mitral annular velocities (E/Ea ratio) was 0.44, 0.27, 0.44, 0.25, and 0.33, respectively. Bivariate genetic analysis showed that LV structural and functional traits had significant genetic correlations with cardiovascular risk factors. Additive genetic correlation (ρG) of LV mass with body mass index, systolic blood pressure, and high density lipoprotein cholesterol were 0.49, 0.42, and -0.15 respectively. LVEF (ρG = 0.33) and left atrial volume index (ρG = 0.24) also had a significant genetic correlation with systolic blood pressure. These findings support the theory that genetic factors have significant influence on these traits and necessitate further work to identify the specific genes involved.

Validation study of candidate single nucleotide polymorphisms associated with left ventricular hypertrophy in the Korean population

Background

Left ventricular hypertrophy (LVH) is a valid predictor for cardiovascular mortality and morbidity regardless of age, gender, and race. The HyperGEN study conducted a genome-wide association study and identified twelve single nucleotide polymorphisms (SNPs) associated with LVH. The aim of this study was to validate these candidate SNPs in the Korean population.

Methods

Among 1637 individuals from the Korean Multi-Rural Communities Cohort Study (MRCohort) of the Korean Genome Epidemiology Study (KoGES), we carried out a linear regression analysis with left ventricular mass index (LVMI) and a logistic regression analysis for LVH status.

Results

The rs4129218 on chromosome 12 tended to be associated with LVM/body surface area (adjusted β = −0.023; p = 0.036) and LVM/height^2.7 (adjusted β = −0.027; p = 0.016), and was marginally protective against LVH after adjustment for age, sex, body mass index, serum creatinine, systolic blood pressure, heart rate and antihypertensive medication (adjusted odds ratio = 0.766 and 0.731; p = 0.027 and 0.007 according to indexation by BSA and height^2.7, respectively).

Conclusions

In the Korean population, the minor allele of rs4129218 had borderline association with lower LVM. This study suggests that rs4129218 on chromosome 12 showed consistent tendency of possibly related loci for LVH independent of ethnic background.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-015-0158-1) contains supplementary material, which is available to authorized users.

Association of genetic variation in calmodulin and left ventricular mass in full-term newborns

Calmodulin II (CALM2) gene polymorphism might be responsible for the variation in the left ventricular mass amongst healthy individuals. The aim was to evaluate the correlation between left ventricular mass (LVM) and g.474955027G>A (rs7565161) polymorphism adjacent to the CALM2 gene. Healthy Polish newborns (n = 206) were recruited. Two-dimensional M-mode echocardiography was used to assess LVM. Polymorphisms were determined by polymerase chain reaction-restriction fragment length polymorphism and sequencing analyses. The carriers of the G allele of the CALM2 polymorphism had significantly higher left ventricular mass/weight (LVM/BW) values, when compared with newborns homozygous for the A allele (3.1 g/m(2) versus 2.5 g/m(2), P adjusted = 0.036). The AG genotype of CALM2 was associated with the highest values of LVM/BW, exhibiting a pattern of overdominance (2.9 g/kg versus 3.1 g/kg versus 2.5 g/kg, P adjusted = 0.037). The results of this study suggest that G>A CALM2 polymorphism may account for subtle variation in LVM at birth.

Transcriptional network analysis for the regulation of left ventricular hypertrophy and microvascular remodeling

Hypertension and cardiomyopathies share maladaptive changes of cardiac morphology, eventually leading to heart failure. These include left ventricular hypertrophy (LVH), myocardial fibrosis, and structural remodeling of coronary microcirculation, which is the morphologic hallmark of coronary microvascular dysfunction. To pinpoint the complex molecular mechanisms and pathways underlying LVH-associated cardiac remodeling independent of blood pressure effects, we employed gene network approaches to the rat heart. We used the Spontaneously Hypertensive Rat model showing many features of human hypertensive cardiomyopathy, for which we collected histological and histomorphometric data of the heart and coronary vasculature, and genome-wide cardiac gene expression. Here, we provide a large catalogue of gene co-expression networks in the heart that are significantly associated with quantitative variation in LVH, microvascular remodeling, and fibrosis-related traits. Many of these networks were significantly conserved to human idiopathic and/or ischemic cardiomyopathy patients, suggesting a potential role for these co-expressed genes in human heart disease.

Variant on chromosome 9p is associated with left ventricular mass: results from two cohorts of essential hypertensive individuals

OBJECTIVES

It is well known that among hypertensive patients, an increased left ventricular mass (LVM) is a powerful predictor of cardiovascular morbidity and mortality. However, the mechanisms underlying LVM in hypertension are not completely understood, as the absolute value of blood pressure and other risk factors associated do not predict alone a definite LVM progression. Recently, the 9p21 chromosomal region has been consistently associated with coronary heart disease.

METHODS AND RESULTS

We examined the association of 384 single nucleotide polymorphisms (SNPs) in the short arm of chromosome 9 with LVM in 821 hypertensive individuals from northern Italy. We identified a SNP (rs894379) in the intronic region of the centlein, centrosomal protein (CNTLN) gene on chromosome 9p22, whose minor allele G is associated with an increased LVM. We performed a follow-up validation analysis for the top SNP in 1038 hypertensive individuals from southern Italy. We then combined the results and found a nominal association for rs894379 (β  =  2.46, P  =  0.0026).

CONCLUSION

We describe a new variant associated with echocardiography LVM. This result, though it needs to be further investigated, may improve our understanding of the genetic determination of this prognostically relevant trait.

Age-related changes in heart function by serial echocardiography in women aged 40-80 years

AIM

To determine if a defined set of echocardiographic parameters at entry and exit of a longitudinal study over 5 years showed changes with aging.

METHODS

The cohort consisted of 484 randomly recruited women aged 40-80. They were examined by two echocardiography cardiologists, independent of the medical information for these women.

RESULTS

Across the age decades (40-49, 50-59, 60-69, 70-79 years), body weight and body surface area (BSA) did not vary, and diastolic blood pressure (DBP) was stable; systolic blood pressure (SBP) progressively increased. There was gradual decline in left ventricular (LV) diastolic function, increase in LV muscle mass, and decrease in LV end-diastolic volume (LVEDV). The serial decrease in rate of change over 5 years in ejection fraction (ET) was small but significant across the four age decades.

CONCLUSIONS

As expected, there were age-related changes in cardiac structure and function over time in women who showed no apparent cardiovascular disease (CVD) at entry to the study. The direction of these serial changes was toward the development of LV stiffness and likelihood of subsequent heart failure. The clinical significance of the decrease in rate of change in EF remains unclear.

Genetic inheritance effects on endurance and muscle strength: an update

Top-level sport seems to play a natural Darwinian stage. The most outstanding athletes appear to emerge as a result of exogenous influences of nature and/or coincidence, namely, the contingency of practicing certain sport for which their talents best fit. This coincidence arises because certain individuals possess anatomical, metabolic, functional and behavioural characteristics that are precisely those required to excel in a given sport. Apart from the effects of training, there is strong evidence of genetic influence upon athletic performance. This article reviews the current state of knowledge regarding heritable genetic effects upon endurance and muscle strength, as reported by several twin and family studies. Due, probably, to the inaccuracy of the measurement procedures and sampling error, heritability estimates differ widely between studies. Even so, the genetic inheritence effects seem incontrovertible in most physical traits: ~40-70% for peak oxygen uptake and cardiac mass and structure, and ~30-90% for anaerobic power and capacity, ranging according to the metabolic category. Studies in development by several researchers at this present time seem to guarantee that future reviews will include twins and family studies concerning genes associated with the adaptive processes against hormetic agents, such as exercise, heat and oxidative stress.

Elements of 'missing heritability'

PURPOSE OF REVIEW

To discuss the basis of 'missing heritability', which has emerged as an enigma in the post-genome-wide association studies (GWAS) era.

RECENT FINDINGS

Alleles identified through GWAS account for a relatively small fraction of heritability of the complex phenotypes. Accordingly, a significant part of heritability of the complex traits remains unaccounted for ('missing heritability'). Recent findings offer several explanations, including overestimation of heritability of the complex traits and underestimation of the effects of alleles identified through GWAS. In addition, yet-to-be identified common as well as rare alleles might in part explain the 'missing heritability'. Moreover, gene-gene (epistasis) and gene-environmental interactions might explain another fraction of heritability of complex traits. Moreover, transgenerational epigenetic changes, regulated in part by microRNAs, might also contribute to the 'missing heritability'.

SUMMARY

The new findings suggest a multifarious nature of the 'missing heritability'. The findings de-emphasize the focus on delineating the basis of 'missing heritability' and shift the focus to elucidation of the molecular mechanisms by which genomic and genetic factors govern the pathogenesis of the complex phenotypes.

Common variants in RYR1 are associated with left ventricular hypertrophy assessed by electrocardiogram

AIMS

To identify the genetic risk factors that influence the development of electrocardiographic (ECG) left ventricular hypertrophy (LVH), a major risk factor for cardiovascular (CV) morbidity and mortality.

METHODS AND RESULTS

We performed a genomewide association study (GWAS) of ECG-LVH, in which the community-based Korea Association REsource (KARE) study (8432 controls and 398 cases) was analysed by Affymetrix SNP array 5.0. The GWAS results were validated in hospital-based samples (597 controls and 207 cases). Fourteen single-nucleotide polymorphisms (SNPs) in eight genetic loci (5q35.1, 6p22.3-22.1, 8q24.2, 11p15, 11q21-22.1, 14q12, 17q11.2, and 19q13.1) were associated with ECG-LVH in the original GWAS study (P < 1 × 10(-5)). Of these SNPs, 12 were genotyped in the hospital sample. There was consistent association with the 19q13.1 region which contains RYR1 gene. The most significant SNP in the region was rs10500279, which had genomewide significance in the combined GWAS/replication sample [odds ratio = 1.58 (confidence interval: 1.35-1.85), P = 1.0 × 10(-8)]. Mutations in RYR1, which encodes a major Ca(2+) channel in the skeletal muscle, have been reported to correlate with CV diseases.

CONCLUSION

We performed the first GWAS for ECG-LVH, implicating the skeletal muscle Ca(2+) channel protein RYR1 as a genetic risk factor. These results might increase our understanding of the development of ECG-LVH.

A follow-up study for left ventricular mass on chromosome 12p11 identifies potential candidate genes

Background

Left ventricular mass (LVM) is an important risk factor for cardiovascular disease. Previously we found evidence for linkage to chromosome 12p11 in Dominican families, with a significant increase in a subset of families with high average waist circumference (WC). In the present study, we use association analysis to further study the genetic effect on LVM.

Methods

Association analysis with LVM was done in the one LOD critical region of the linkage peak in an independent sample of 897 Caribbean Hispanics. Genotype data were available on 7085 SNPs from 23 to 53 MB on chromosome 12p11. Adjustment was made for vascular risk factors and population substructure using an additive genetic model. Subset analysis by WC was performed to test for a difference in genetic effects between the high and low WC subsets.

Results

In the overall analysis, the most significant association was found to rs10743465, downstream of the SOX5 gene (p = 1.27E-05). Also, 19 additional SNPs had nominal p < 0.001. In the subset analysis, the most significant difference in genetic effect between those with high and low WC occurred with rs1157480 (p = 1.37E-04 for the difference in β coefficients), located upstream of TMTC1. Twelve additional SNPs in or near 6 genes had p < 0.001.

Conclusions

The current study supports previously identified evidence by linkage for a genetic effect on LVM on chromosome 12p11 using association analysis in population-based Caribbean Hispanic cohort. SOX5 may play an important role in the regulation of LVM. An interaction of TMTC1 with abdominal obesity may contribute to phenotypic variation of LVM.

Protective effect of the 1742(C/G) polymorphism of human cardiotrophin-1 against left ventricular hypertrophy in essential hypertension

OBJECTIVE

Experimental and clinical evidence supports a role of cardiotrophin-1 (CT-1) in the development of hypertensive left ventricular hypertrophy (LVH). The goal of this study was to investigate the relationship between human CT-1 genetic background and LVH in essential hypertension.

METHODS

A total of 900 individuals were genotyped for the 1742(C/G) polymorphism of the human CT-1 gene. Serum CT-1 levels were assessed by ELISA in 681 individuals. Left ventricular parameters were determined by two-dimensional echocardiography in 297 individuals.

RESULTS

The prevalence of the GG genotype of the 1742(C/G) polymorphism was reduced in essential hypertension (8.4% in normotensive individuals, 4.9% in hypertensive patients, P = 0.046 versus CC/CG individuals) and in LVH (11.5% in nonhypertrophic normotensive individuals, 12.2% in nonhypertrophic hypertensive patients, 2.6% in hypertensive patients with LVH, P = 0.008 versus CC/CG individuals). Apart from this, GG individuals presented lower serum concentration of CT-1 (GG, 147.1 ± 10.5 fmol/ml; CC/CG, 187.1 ± 4.8 fmol/ml; P = 0.036) and left ventricular mass index (GG, 91 ± 6 g/m; CC/CG, 119 ± 3 g/m; P = 0.002). Multivariate analyses showed that the 1742(C/G) polymorphism was a significant determinant of both left ventricular mass index and serum CT-1, after adjusting for confounding factors. Finally, in-vitro studies supported the functionality of the 1742(C/G) polymorphism.

CONCLUSION

Our results indicate that the 1742(C/G) polymorphism of the human CT-1 gene is associated with LVH in hypertension and that the GG genotype may have a protective role. It is suggested that CT-1 is one of the mediators of this association.

Association of echocardiographic left ventricular structure with the ACE D/I polymorphism: a meta-analysis

Introduction: In a previous meta-analysis, we derived pooled estimates for the association of left ventricular mass (LVM) and hypertrophy (LVH), as diagnosed by electrocardiography or echocardiography, with the ACE D/I polymorphism. We updated this meta-analysis until May 2009 only considering echocardiographic phenotypes.

Methods: We computed pooled estimates from a random-effects model.

Results: Across 38 studies, both DD homozygotes ( n = 2440) and DI heterozygotes ( n = 4310) had higher ( p ≤ 0.002) LVM or LVM index than II homozygotes ( n = 2229). Across 21 studies with available data, this was due to increased mean wall thickness (MWT) with no difference in left ventricular internal diameter (LVID). Standardised differences (DD versus II) were 0.39 ( p < 0.001) for LVM, 0.34 ( p = 0.009) for MWT, and 0.066 ( p = 0.26) for LVID. Across 16 studies (4894 participants), the pooled odds ratios of LVH (versus II homozygotes) were 1.11 ( p = 0.29) and 1.02 ( p = 0.88) for the DD and DI genotypes, respectively. Sensitivity analyses were confirmatory.

Conclusions: Our meta-analysis supports the hypothesis that the enhanced ACE activity associated with the D allele is associated with higher LV mass. Smaller sample size might explain the lack of significant association with LVH.

Genetic variation in NCAM1 contributes to left ventricular wall thickness in hypertensive families

RATIONALE

Left ventricular (LV) mass and related phenotypes are heritable, important predictors of cardiovascular disease, particularly in hypertensive individuals.

OBJECTIVE

Identify genetic predictors of echocardiographic phenotypes in hypertensive families.

METHODS AND RESULTS

A multistage genome-wide association study (GWAS) was conducted in hypertensive-ascertained black families (HyperGEN, stage I; GENOA, stage II); findings were replicated in HyperGEN white families (stage III). Echocardiograms were collected using a common protocol, and participants were genotyped with the Affymetrix Genome-Wide Human SNP 6.0 Array. The following were analyzed using mixed models adjusted for ancestry: in stages I and II, 1258 and 989 blacks, respectively; and in stage III, 1316 whites. Phenotypes included LV mass, LV internal dimension (LVID), wall thicknesses (posterior [PWT] and intraventricular septum [IVST]), and relative wall thickness (RWT). In stage I, 5 single nucleotide polymorphisms (SNPs) had P≤10(-6). In stage II, 1 SNP (rs1436109; NCAM1 intron 1) replicated with the same phenotype (PWT, P=0.025) in addition to RWT (P=0.032). In stage III, rs1436109 was associated with RWT (P=5.47×10(-4)) and LVID (P=1.86×10(-4)). Fisher combined probability value for all stages was RWT=3.80×10(-9), PWT=3.12×10(-7), IVST=8.69×10(-7), LV mass=2.52×10(-3), and LVID=4.80×10(-4).

CONCLUSIONS

This GWAS conducted in hypertensive families identified a variant in NCAM1 associated with LV wall thickness and RWT. NCAM is upregulated during the remodeling period of hypertrophy to heart failure in Dahl salt-sensitive rats. Our initial screening in hypertensive blacks may have provided the context for this novel locus.

SNP-SNP interactions dominate the genetic architecture of candidate genes associated with left ventricular mass in African-Americans of the GENOA study

BACKGROUND

Left ventricular mass (LVM) is a strong, independent predictor of heart disease incidence and mortality. LVM is a complex, quantitative trait with genetic and environmental risk factors. This research characterizes the genetic architecture of LVM in an African-American population by examining the main and interactive effects of individual candidate gene single nucleotide polymorphisms (SNPs) and conventional risk factors for increased LVM.

METHODS

We used least-squares linear regression to investigate 1,878 SNPs from 234 candidate genes for SNP main effects, SNP-risk factor interactions, or SNP-SNP interactions associated with LVM in 1,328 African-Americans from the Genetic Epidemiology Network of Arteriopathy (GENOA) study. We reduced the probability of false positive results by implementing three analytic criteria: 1) the false discovery rate, 2) cross-validation, and 3) testing for internal replication of results.

RESULTS

We identified 409 SNP-SNP interactions passing all three criteria, while no SNP main effects or SNP-risk factor interactions passed all three. A multivariable model including four SNP-SNP interactions explained 11.3% of the variation in LVM in the full GENOA sample and 5.6% of LVM variation in independent test sets.

CONCLUSIONS

The results of this research underscore that context dependent effects, specifically SNP-SNP interactions, may dominate genetic contributions to variation in complex traits such as LVM.

Natriuretic peptides and the genomics of left-ventricular hypertrophy

Left-ventricular hypertrophy (LVH) is one of the strongest independent predictors of cardiovascular morbidity and mortality in the general population. Although hypertension and obesity are well-established, independent risk factors for the development of LVH, they explain less than 25% to 50% of the variance of left ventricular mass (LVM) in humans. A substantial body of evidence suggests that there is a genetic basis to the observed inter-individual variability in the susceptibility to the development of LVH. Given the continuous relationship between LVM and cardiovascular morbidity and mortality, elucidating the genetic determinants of inter-individual differences in the susceptibility to LVH is of considerable public health importance. It promises the opportunity to identify high-risk individuals for targeted intervention and may identify novel therapeutic targets for improved prevention and treatment strategies.

Electrocardiographic indices of left ventricular hypertrophy and repolarization phase share the same genetic influences: a twin study

BACKGROUND

Both left ventricular hypertrophy (LVH) and repolarization phase (RP) are known to be attributable to genetic influences, but less is known whether they share same genetic influences. The aim of this study was to investigate to what extent individual differences in electrocardiographic (ECG) LVH and RP are explained by genetic and environmental influences and whether these influences are shared between these two traits.

METHODS

Resting ECG recordings were obtained from 186 monozygotic and 203 dizygotic female twin individuals, aged 63 to 76 years. Latent factors, called LVH and RP, were formed to condense the information obtained from LVH indices (Cornell voltage and Cornell product) and T-wave amplitudes (leads V(5) and II), respectively. Multivariate quantitative genetic modeling was used both to decompose the phenotypic variances into additive genetic, common environmental, and unique environmental influences, and for the calculation of genetic and environmental correlations between LVH and RP.

RESULTS

Additive genetic influences explained 16% of individual differences in LVH and 74% in RP. The remaining individual differences were explained by both common and unique environmental influences. The genetic correlation and unique environmental correlation between LVH and RP were -0.93 and -0.05, respectively.

CONCLUSIONS

In older women without overt cardiac diseases, RP is under stronger genetic control than LVH. The majority of genetic influences are shared between LVH and RP whereas environmental influences are mainly specific to each.

Novel quantitative trait locus is mapped to chromosome 12p11 for left ventricular mass in Dominican families: the Family Study of Stroke Risk and Carotid Atherosclerosis

Background

Left ventricular mass (LVM) is an important risk factor for stroke and vascular disease. The genetic basis of LVM is unclear although a high heritability has been suggested. We sought to map quantitative trait loci (QTL) for LVM using large Dominican families.

Methods

Probands were selected from Dominican subjects of the population-based Northern Manhattan Study (NOMAS). LVM was measured by transthoracic echocardiography. A set of 405 microsatellite markers was used to screen the whole genome among 1360 subjects from 100 Dominican families who had complete phenotype data and DNA available. A polygenic covariate screening was run to identify the significant covariates. Variance components analysis was used to estimate heritability and to detect evidence for linkage, after adjusting for significant risk factors. Ordered-subset Analysis (OSA) was conducted to identify a more homogeneous subset for stratification analysis.

Results

LVM had a heritability of 0.58 in the studied population (p < 0.0001). The most significant evidence for linkage was found at chromosome 12p11 (MLOD = 3.11, empirical p = 0.0003) with peak marker at D12S1042. This linkage was significantly increased in a subset of families with the high average waist circumference (MLOD = 4.45, p = 0.0045 for increase in evidence for linkage).

Conclusion

We mapped a novel QTL near D12S1042 for LVM in Dominicans. Enhanced linkage evidence in families with larger waist circumference suggests that gene(s) residing within the QTL interact(s) with abdominal obesity to contribute to phenotypic variation of LVM. Suggestive evidence for linkage (LOD = 1.99) has been reported at the same peak marker for left ventricular geometry in a White population from the HyperGEN study, underscoring the importance of this QTL for left ventricular phenotype. Further fine mapping and validation studies are warranted to identify the underpinning genes.

Genome-wide association study identifies single-nucleotide polymorphism in KCNB1 associated with left ventricular mass in humans: the HyperGEN Study

Background

We conducted a genome-wide association study (GWAS) and validation study for left ventricular (LV) mass in the Family Blood Pressure Program – HyperGEN population. LV mass is a sensitive predictor of cardiovascular mortality and morbidity in all genders, races, and ages. Polymorphisms of candidate genes in diverse pathways have been associated with LV mass. However, subsequent studies have often failed to replicate these associations. Genome-wide association studies have unprecedented power to identify potential genes with modest effects on left LV mass. We describe here a GWAS for LV mass in Caucasians using the Affymetrix GeneChip Human Mapping 100 k Set. Cases (N = 101) and controls (N = 101) were selected from extreme tails of the LV mass index distribution from 906 individuals in the HyperGEN study. Eleven of 12 promising (Q < 0.8) single-nucleotide polymorphisms (SNPs) from the genome-wide study were successfully genotyped using quantitative real time PCR in a validation study.

Results

Despite the relatively small sample, we identified 12 promising SNPs in the GWAS. Eleven SNPs were successfully genotyped in the validation study of 704 Caucasians and 1467 African Americans; 5 SNPs on chromosomes 5, 12, and 20 were significantly (P ≤ 0.05) associated with LV mass after correction for multiple testing. One SNP (rs756529) is intragenic within KCNB1, which is dephosphorylated by calcineurin, a previously reported candidate gene for LV hypertrophy within this population.

Conclusion

These findings suggest KCNB1 may be involved in the development of LV hypertrophy in humans.

Genetic influences on resting electrocardiographic variables in older women: a twin study

BACKGROUND

Previous studies in young and middle-aged men and women have shown that resting electrocardiographic (ECG) variables are influenced by genetic factors. However, the extent to which resting ECG variables are influenced by genetic factors in older women is unknown. Thus, the aim of this study was to estimate the relative contribution of genetic and environmental influences to individual differences in resting ECG variables among older female twins without overt cardiac diseases.

METHODS

Resting ECG recordings were obtained from 186 monozygotic and 203 dizygotic twin individuals, aged 63-76 years. Quantitative genetic modeling was used to decompose the phenotypic variance in each resting ECG variable into additive genetic, dominance genetic, shared environmental, and unique environmental influences.

RESULTS

The results showed that individual differences in the majority of the resting ECG variables were moderately to highly explained by additive genetic influences, ranging from 32% for T axis to 72% for TV(5). The results also suggested dominance genetic influences on QRS duration, TV(1), and Sokolow-Lyon voltage (36%, 53%, and 57%, respectively). Unique environmental influences were important for each resting ECG variable, whereas shared environmental influences were detected only for QT interval and QTc.

CONCLUSION

In older women without overt cardiac diseases, genetic influences explain a moderate to high proportion of individual differences in the majority of the resting ECG variables. Genetic influences are especially strong for T-wave amplitudes, left ventricular mass, and hypertrophy indices, whereas other variables, including heart rate, intervals, and axes, are more affected by environmental influences.

Change of genetic determinants of left ventricular structure in adolescence: longitudinal evidence from the Georgia cardiovascular twin study

BACKGROUND

Genetic contribution to left ventricular (LV) structure is generally recognized, but whether and how this influence varies by ethnicity or with age is unknown.

METHODS

Participants were 517 European-American (EA) and African-American (AA) twin pairs (mean age: 14.6 +/- 3.0) at visit 1 and 422 EA and AA twin pairs at follow-up 4.1 years later. Echocardiograms were obtained on both visits. Data were analyzed using the structural equation modeling software Mx.

RESULTS

Body mass index (BMI) was a strong predictor for all LV measures at both visits 1 and 2, accounting for 3.5-24.2% of the total variance. Hemodynamics explained up to 4.5% additional LV measures variance. After adjusting for BMI, LV measures showed substantial heritability (range: 21-71%). Best-fitting longitudinal models revealed considerable novel genetic effects on the interventricular septum, posterior wall-, and relative wall thickness (RWT) (but not LV internal diameter), accounting for 32-41% of the phenotypic variance at visit 2, with no significant gender and ethnic effects. There was a gender difference for LV mass index in AAs (P < 0.01), with a significant influence of novel genetic effects in males (47%), but not in females. No gender difference was seen in EAs, with 34% of the phenotypic variance at visit 2 attributable to novel genetic effects.

CONCLUSIONS

The heritability of cardiac structure and geometry was equally substantial in both AAs and EAs. Significant novel genetic influences were detected for all measures but LV inner diameter and LV mass index in AA females. Further developmental genetic studies are warranted to elucidate the nature of the emerging gene effects during the transition from adolescence to adulthood.

Genetic determinants of cardiac hypertrophy

PURPOSE OF REVIEW

Cardiac hypertrophy is a common phenotypic response of the heart to stimulants. It is associated with increased morbidity and mortality in various cardiovascular disorders. Genetic factors are important determinants of phenotypic expression of cardiac hypertrophy, whether in single-gene disorders or in complex traits. We focus on the molecular genetics of cardiac hypertrophy in various conditions with an emphasis on hypertrophic cardiomyopathy, a genetic paradigm of cardiac hypertrophic response.

RECENT FINDINGS

The molecular genetic basis of cardiac hypertrophy in single-gene disorders has been partially elucidated. Likewise, the impact of genetics on the expression of cardiac hypertrophy in the general population has been demonstrated. Identification of mutations in the Z disk proteins has expanded the spectrum of causal mutations beyond the thin and thick filaments of the sarcomeres. In addition, modifier loci have been mapped and shown to impart considerable effects on the expression of cardiac hypertrophy in hypertrophic cardiomyopathy. Elucidation of the molecular genetics of sarcomeric hypertrophic cardiomyopathy and many of the phenocopies has highlighted the limitations of clinical diagnosis as a determinant of management and prognostic advice. The findings have raised the importance of diagnosis and treatment algorithms, which are based on both genotype and phenotype information.

SUMMARY

Cardiac hypertrophy, regardless of the cause, is the phenotypic consequence of complex interactions between genetic and nongenetic factors.

Ability of blood pressure to predict left ventricular hypertrophy in children with primary hypertension

OBJECTIVE

To determine whether casual blood pressure (BP) or ambulatory BP monitoring (ABPM) measurements obtained at the initial visit of a child with confirmed hypertension (HTN) might predict left ventricular hypertrophy (LVH), possibly obviating the need for echocardiography.

STUDY DESIGN

We conducted a cross-sectional study of 184 children aged 3 to 20 years who were referred for initial evaluation of elevated BP at 3 tertiary care centers. Casual BP and various ambulatory BP variables were analyzed to determine their association with LVH, defined after echocardiography by cardiologist diagnosis or a left ventricular mass index equal to or greater than the sex-specific 95th percentile.

RESULTS

A total of 41% of children who had echocardiograms had LVH. Children with LVH were significantly more likely to be non-white and have a higher body mass index z-score. There was no difference in casual systolic or diastolic BP index in children with hypertension who had LVH and children with hypertension without LVH. Children with systolic or diastolic BP loads > or = 50% were no more likely to have LVH than children with loads < 50%.

CONCLUSION

LVH is common in children with newly diagnosed HTN. The initial examination of these children should include echocardiography, because neither the severity of casual BP elevation nor the presence of abnormal ambulatory BP results at initial diagnosis are predictive of LVH.

The contribution of familial and heritable risks in heart failure

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent literature regarding the familial heritability of heart failure and to discuss the possible mechanisms through which this risk is mediated.

RECENT FINDINGS

Data from the Framingham Heart Study recently showed that the parental occurrence of heart failure increases the risk of heart failure in offspring. Although the mechanisms mediating this increased risk are not elucidated, heritable risks of heart failure may result from genes affecting the cardiac or vascular systems. Alternatively, familial risk may be mediated partly through the inheritance of recognized or as yet unidentified risk factors for heart failure. Heritable components or genetic loci for quantitative traits contribute to the development of hypertension, coronary artery disease, cardiomyopathies, valvular heart disease, and metabolic conditions, which collectively increase the risk of heart failure.

SUMMARY

A careful assessment of the family history of heart failure and associated risk factors may identify treatable targets that can potentially reduce the likelihood of developing heart failure, and can assist in the implementation of preventive strategies for risk populations with stages A and B heart failure.

Heritability of left ventricular mass in Japanese families living in Hawaii: the SAPPHIRe Study

OBJECTIVE

Established determinants of left ventricular (LV) mass explain only a modest fraction of its variability. Family studies to date suggest that a proportion of the unexplained variability can be accounted for by additive polygenic effects. An estimate of this proportion has not been reported previously in an East Asian population. The objective of this study was to estimate the heritability of LV mass in Japanese families living in Hawaii.

DESIGN AND METHODS

We analyzed data by components of variance in a sample of 169 hypertensive families (n = 476 subjects) and, separately, in a population-based sample of 256 families (n = 501 subjects) participating in the Honolulu Heart Program.

RESULTS

In multivariate models, established predictors of LV mass explained about half the total variance of LV mass. Using SOLAR, our estimates of the narrow sense heritability of LV mass ranged from 42.5% (SE 9.8, P < 0.0001) in our sample of hypertensive families to 60.6% (SE 11.7, P < 0.0001) in our population-based sample of families. Parametric bootstrap analyses confirmed that the inference for each sample was appropriate.

CONCLUSIONS

Assuming the absence of shared familial environmental effects, close to half of the unexplained variance of LV mass in Japanese subjects living in Hawaii is genetic in nature. This estimate was observed in two independent samples. Therefore, the pursuit of novel genetic determinants of LV mass through either whole genome or candidate gene association studies of this population may be worthwhile. Such studies are certainly feasible.

Age-related changes in echocardiographic measurements: association with variation in the estrogen receptor-alpha gene

Left ventricular (LV) mass and other LV measures have been shown to be heritable. In this study we hypothesized that functional variation in the gene coding for estrogen receptor-alpha (ESR1), known for mediating the effect of estrogens on myocardium, is associated with age-related changes in LV structure. Four genetic markers (ESR1 TA repeat; rs2077647, or +30T>C; rs2234693, or PvuII; and rs9340799, or XbaI) were genotyped in 847 unrelated individuals (488 women) from the Framingham Offspring Study, who attended 2 examination cycles 16 years apart (mean ages at first examination: 43+/-9 years; at follow-up: 59+/-9 years). ANCOVA was used to assess the association of polymorphisms and their haplotypes with cross-sectional measurements and longitudinal changes in LV mass, wall thickness, end-diastolic and end-systolic internal diameter, and fractional shortening after adjustment for factors known to influence these variables. Changes over time were detected for all of the LV measurements (P ranging from <0.0001 to 0.02), except for fractional shortening in men. The SS genotype of the ESR1 TA repeat polymorphism in the promoter region was associated with longitudinal changes in LV mass and LV wall thickness (P ranging from 0.0006 to 0.01). Moreover, the TA[S]-+30[T]-PvuII[T]-XbaI[A] haplotype (frequency: 47.5%) was associated with greater LV changes as compared with the TA[L]-+30[C]-PvuII[C]-XbaI[G] haplotype (frequency: 31.8%). Our results are consistent with the hypothesis that common ESR1 polymorphisms are significantly associated with age-related changes in LV structure. Understanding the mechanisms predisposing to unfavorable LV remodeling of the heart with advancing age may aid in the discovery of new therapeutic targets for the prevention of heart failure.