Genetic contributions to left ventricular hypertrophy

Association of ACE gene D polymorphism with left ventricular hypertrophy in patients with diastolic heart failure: a case-control study

OBJECTIVES

To explore the association between ACE gene insertion/deletion (I/D) polymorphism with left ventricular hypertrophy (LVH) in patients with hypertension who have developed heart failure with preserved ejection fraction (HFpEF). Being a major contributor to the development of diastolic heart dysfunction, the renin angiotensin aldosterone system and its genetic variations are thought to induce LVH in hypertensive hearts apart from haemodynamic factors.

DESIGN

Case control study.

SETTING

An Iranian referral university hospital.

PARTICIPANTS

176 patients with hypertension and a diagnosis of HFpEF on presence of symptoms of heart failure plus Doppler echocardiographic documentation of left ventricular (LV) diastolic dysfunction and/or elevated NT-proBNP levels. Those with significant coronary, valvular, pericardial and structural heart diseases were excluded as well as patients with atrial fibrillation, renal failure and pulmonary causes of dyspnoea. They were divided into two cohorts of 88 cases with and 88 controls without LVH, after determination of LV mass index, using two-dimensional and M-mode echocardiography. The I/D polymorphism of the ACE gene was determined using the PCR method.

RESULTS

The D allele was significantly more prevalent among cases with compared with controls without LVH (p=0.0007). Genotype distributions also differed significantly under additive (p=0.005, OR=0.53, 95% CI 0.34 to 0.84) and recessive (p=0.001, OR=0.29, 95% CI 0.13 to 0.66) models.

CONCLUSIONS

In patients with hypertension who develop HFpEF, the D allele of the ACE gene is probably associated with the development of LVH. With the detrimental effects of LVH on the heart's diastolic properties, this can signify the role of genetic contributors to the development of HFpEF in patients with hypertension and may serve as a future risk predictor for the disease.

The association between BMP4 gene polymorphism and its serum level with the incidence of LVH in hypertensive patients

Background

Bone morphogenic proteins 4 (BMP4) is associated with cardiac remodeling under different conditions. However, the role of BMP4 and its gene polymorphism in the incidence of left ventricular hypertrophy (LVH) in hypertensive patients remains unknown.

Methods

A total of 1265 patients diagnosed with essential hypertension (EH) were recruited. Patients were assigned to LVH+ (n = 420) and LVH- (n = 845) groups. serum BMP4 level was measured and two single nucleotide polymorphism (SNPs) polymorphisms, 6007C > T and -5826G > A of BMP4 gene were genotyped. We also inhibited the BMP4 by small interfering RNA (siRNA). The effect of BMP4 on the hypertrophic response in Human Cardiomyocytes AC16 cells was studied.

Results

We found that the 6007C > T polymorphism of the BMP4 gene and the serum BMP4 level were significantly associated with the risk to develop LVH. With TT as reference, multivariate logistic regression analysis showed the 6007CC genotype carriers had a higher susceptibility to LVH incidence (adjusted OR = 2.65, 95% CI: 1.63-4.31, adjusted P < 0.001). Our in vitro study shows that the BMP4 inhibition in cardiomyocyte by si-RNA technique significantly decreased the Ang II induced cardiomyocyte size and protein content per cell, indicating the importance of BMP4 in the cardiomyocyte hypertrophy.

Conclusion

Collectively, our data suggest that both the 6007C > T of the BMP4 gene and the serum BMP4 level may be used as potential marker for LVH incidence among the EH patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-014-0368-x) contains supplementary material, which is available to authorized users.

Role of osteoprotegerin and its gene polymorphisms in the occurrence of left ventricular hypertrophy in essential hypertensive patients

The aim of the study was to investigate the role of osteoprotegerin (OPG) in left ventricular hypertrophy (LVH) development in patients with essential hypertension (EH). A total of 1092 patients diagnosed with EH were recruited. The LVHs were determined and OPG gene polymorphisms were genotyped. Patients with LVH had a significantly higher mean serum OPG level than those without LVH. The 1181CC genotype carriers had significantly lower risk for LVH compared with GC and GG genotype carriers. The serum OPG level and OPG 1181 G>C polymorphism were found to be independent risk factors for the occurrence of LVH in hypertensive patients. In vitro study shows that OPG overexpression upregulates cell surface size, protein synthesis per cell, and hypertrophy- and fibrosis-related proteins in both cardiomyocytes and cardiac fibroblasts, whereas OPG inhibition can abolish the above-mentioned changes. Consistent with the in vitro data, our in vivo study revealed that the OPG administration induced the LVH in hypertensive rats. This study is the first to report the close association between OPG and LVH development in EH patients and the regulatory effect of OPG on cardiomyocytes and cardiac fibroblasts.

Genetics of diastolic heart failure

Heart failure explains a large portion of heart diseases. Molecular mechanisms determining cardiac function, by inference dysfunction in heart failure, are incompletely understood, especially in the common (or congestive) systolic (SHF) and diastolic heart failure (DHF). Limited genome-wide association studies (GWASs) in humans are reported on SHF and no GWAS has been performed on DHF. Genetic analyses in a rodent model of true DHF, Dahl salt-sensitive (DSS) rats, have begun to unravel the genetic components determining diastolic function. Diastolic dysfunction of DSS rats can be ameliorated or even normalized by distinct quantitative trait loci (QTLs), designated as diastolic function/blood pressure QTLs (DF/BP QTLs), which also affect blood pressure (BP). However, an improvement in diastolic dysfunction is merely transitory from a single DF/BP QTL, despite a permanent lowering of BP. A long-term protection against diastolic dysfunction can be realized only through combining specific DF/BP QTLs. Moreover, the worsening diastolic dysfunction with age can also be reversed in a different combination of DF/BP QTLs. Thus, distinct genes in combinations must be involved in the physiological mechanisms ameliorating or reversing diastolic dysfunction. As not all the QTLs that influence BP can affect diastolic function, it is not BP reduction itself that restores diastolic function, but rather specific genes that are uniquely integrated into the pathways of blood pressure homeostasis as well as diastolic function. Thus, the elucidation of pathophysiological mechanisms causal to hypertensive diastolic dysfunction will not only provide new diagnostic tools, but also novel therapeutic targets and strategies in reducing, curing, and even reversing DHF.

Serum osteopontin, but not OPN gene polymorphism, is associated with LVH in essential hypertensive patients

This study aims to investigate the role of osteopontin (OPN) genetic polymorphisms in the occurrence of left ventricular hypertrophy (LVH) in Chinese patients with essential hypertension (EH). A total of 1,092 patients diagnosed with EH were recruited. Three single nucleotide polymorphisms (SNP) on the promoter region of the OPN gene, including -66T/G, -156G/GG, and -443C/T were genotyped. The serum thrombin-cleaved OPN levels were studied. Patients were divided into LVH+ (n = 443) and the LVH- (n = 649) groups. We found that none of the studied SNPs in the OPN gene was associated with the risk and severity of LVH. The SNPs in the OPN gene did not correlate with the serum OPN levels. However, the serum thrombin-cleaved OPN levels were found to be an independent risk factor for LVH in the EH patients. Multivariate logistic regression analysis showed that serum thrombin-cleaved OPN levels were independently associated with the development of LVH (adjusted OR = 2.47, 95 % CI 1.56-4.01, adjusted P < 0.001). In vitro studies showed that the thrombin-cleaved OPN treatment increased the protein content per cell, the cardiomyocyte surface size, and the expression level of atrial natriuretic peptide protein in a dose-dependent manner. The thrombin-cleaved OPN serum level, but not OPN gene polymorphism, is associated with the development of LVH in EH patients.

KEY MESSAGES

Serum OPN is related to LVH incidence in essential hypertension subjects. OPN stimulates cardiomyocyte hypertrophy in vitro. OPN SNPs are not related to LVH incidence.

Genome-wide association study of cardiac structure and systolic function in African Americans: the Candidate Gene Association Resource (CARe) study

BACKGROUND

Using data from 4 community-based cohorts of African Americans, we tested the association between genome-wide markers (single-nucleotide polymorphisms) and cardiac phenotypes in the Candidate-gene Association Resource study.

METHODS AND RESULTS

Among 6765 African Americans, we related age, sex, height, and weight-adjusted residuals for 9 cardiac phenotypes (assessed by echocardiogram or magnetic resonance imaging) to 2.5 million single-nucleotide polymorphisms genotyped using Genome-wide Affymetrix Human SNP Array 6.0 (Affy6.0) and the remainder imputed. Within the cohort, genome-wide association analysis was conducted, followed by meta-analysis across cohorts using inverse variance weights (genome-wide significance threshold=4.0 ×10(-7)). Supplementary pathway analysis was performed. We attempted replication in 3 smaller cohorts of African ancestry and tested lookups in 1 consortium of European ancestry (EchoGEN). Across the 9 phenotypes, variants in 4 genetic loci reached genome-wide significance: rs4552931 in UBE2V2 (P=1.43×10(-7)) for left ventricular mass, rs7213314 in WIPI1 (P=1.68×10(-7)) for left ventricular internal diastolic diameter, rs1571099 in PPAPDC1A (P=2.57×10(-8)) for interventricular septal wall thickness, and rs9530176 in KLF5 (P=4.02×10(-7)) for ejection fraction. Associated variants were enriched in 3 signaling pathways involved in cardiac remodeling. None of the 4 loci replicated in cohorts of African ancestry was confirmed in lookups in EchoGEN.

CONCLUSIONS

In the largest genome-wide association study of cardiac structure and function to date in African Americans, we identified 4 genetic loci related to left ventricular mass, interventricular septal wall thickness, left ventricular internal diastolic diameter, and ejection fraction, which reached genome-wide significance. Replication results suggest that these loci may be unique to individuals of African ancestry. Additional large-scale studies are warranted for these complex phenotypes.

Assessment of the interaction of heritability of volume load and left ventricular mass: the HyperGEN offspring study

BACKGROUND

Left ventricular mass (LVM) is more closely associated with volume load than pressure load. We assessed whether part of the genetic heritability of LVM can be explained by stroke volume (SV) inheritance.

METHODS

Echocardiographic LVM, SV and peripheral resistance were measured in 527 families with at least two relatives from the HyperGEN study (51% African-American, 43% men, 44% obese, 53% hypertensive). Included were 1792 subjects without prevalent cardiovascular disease, diabetes and renal failure. Ethnic-specific genetic correlations were estimated using a variance components procedure (SOLAR).

RESULTS

Significant genetic correlations existed between LVM and SV after adjusting for age, sex, race, field center, systolic blood pressure, number of antihypertensive medications, and body mass index (rhog = 0.93 in African-Americans and 0.70 in Caucasians; both P < 0.0001). Urinary Na excretion or serum creatinine did not influence these correlations. After adjusting for covariates, heritability of LVM was greater (h = 0.46 in African-Americans and 0.47 in Caucasians; both P < 0.0001) than that for SV (h = 0.18 in African-Americans and 0.29 in Caucasians; both P < 0.02). Heritability of LVM slightly decreased in African-Americans (h = 0.34), but not in Caucasians (h = 0.45; both P < 0.0001) when SV was added to covariates. Heritability of SV almost disappeared by addition of LVM into the model in African-Americans (h = 0.04, P = not significant), whereas it was slightly reduced in Caucasians (h = 0.20, P < 0.005).

CONCLUSION

LVM and SV share a common genetic profile, but with only a modest reciprocal influence. Variability of LVM has some effect on calculated heritability of SV, especially in African-Americans, whereas the role of heritable volume load in determining the variability of LVM was modest only in African-Americans.

Genetic Variations Associated With Echocardiographic Left Ventricular Traits in Hypertensive Blacks

Echocardiographic measures of cardiac target organ damage, including left ventricular mass and relative wall thickness, are powerful predictors of heart disease morbidity and mortality. The aim of this study is to investigate whether single nucleotide polymorphisms in candidate genes for hypertension and heart disease have effects on quantitative measures of hypertensive cardiac target organ damage, independent of their actions on blood pressure levels, in a cohort of hypertensive black sibships. To detect replication of genetic effects across samples, this study took advantage of the affected sibling pair design and created 2 samples, each with 448 unrelated individuals. As part of the Genetic Epidemiology Network of Arteriopathy Study, subjects were screened using 2D echocardiography, and 395 single nucleotide polymorphisms in 80 candidate genes were genotyped. Linear regression was used to test for single nucleotide polymorphisms significantly associated with left ventricular mass index (g/m 2.7 ) or relative wall thickness after adjusting for associated covariates. Significant single nucleotide polymorphisms were subsequently tested for consistent directionality in genotype–phenotype relationships across samples. Three single nucleotide polymorphisms, 1 each in the APOE , SCN7A , and SLC20A1 genes, were significantly associated in both samples with left ventricular mass index and had replicate genotype–phenotype relationships. One in the ADRB1 gene was significantly associated with relative wall thickness with replicate effects in both samples. We identified genetic variation that significantly influences left ventricular traits with replicable effects in a cohort of hypertensive, black siblings.

Maternal nutrient restriction alters gene expression in the ovine fetal heart

Adequate maternal nutrient supply is critical for normal fetal organogenesis. We previously demonstrated that a global 50% nutrient restriction during the first half of gestation causes compensatory growth of both the left and right ventricles of the fetal heart by day 78 of gestation. Thus, it was hypothesized that maternal nutrient restriction significantly altered gene expression in the fetal cardiac left ventricle (LV). Pregnant ewes were randomly grouped into control (100% national research council (NRC) requirements) or nutrient-restricted groups (50% NRC requirements) from day 28 to day 78 of gestation, at which time fetal LV were collected. Fetal LV mRNA was used to construct a suppression subtraction cDNA library from which 11 cDNA clones were found by differential dot blot hybridization and virtual Northern analysis to be up-regulated by maternal nutrient restriction: caveolin, stathmin, G-1 cyclin, alpha-actin, titin, cardiac ankyrin repeat protein (CARP), cardiac-specific RNA-helicase activated by MEF2C (CHAMP), endothelial and smooth muscle derived neuropilin (ESDN), prostatic binding protein, NADH dehydrogenase subunit 2, and an unknown protein. Six of these clones (cardiac alpha-actin, cyclin G1, stathmin, NADH dehydrogenase subunit 2, titin and prostatic binding protein) have been linked to cardiac hypertrophy in other species including humans. Of the remaining clones, caveolin, CARP and CHAMP have been shown to inhibit remodelling of hypertrophic tissue. Compensatory growth of fetal LV in response to maternal undernutrition is concluded to be associated with increased transcription of genes related to cardiac hypertrophy, compensatory growth or remodelling. Counter-regulatory gene transcription may be increased, in part, as a response to moderating the degree of cardiac remodelling. The short- and long-term consequences of these changes in fetal heart gene expression and induction of specific homeostatic mechanisms in response to maternal undernutrition remain to be determined.

Cardiac hypertrophy: a matter of translation

1. Left ventricular hypertrophy (LVH) of the heart is an adaptive response to sustained increases in blood pressure and hormone imbalances. Left ventricular hypertrophy is associated with programmed responses at the molecular and biochemical level in different subsets of cardiac cells, including the cardiac muscle cells (cardiomyocytes), fibroblasts, conductive tissue and coronary vasculature. 2. Regardless of the initiating cause, the actual increase in chamber enlargement is, in each case, due to an increase in size of a pre-existing cardiomyocyte population, with little or no change in their number; a process referred to as cellular hypertrophy. 3. An accelerated rate of global protein synthesis is the primary mechanism by which protein accumulation increases during cardiomyocyte hypertrophy. In turn, increased rates of synthesis are a result of increased translational rates of existing ribosomes (translational efficiency) and/or synthesis and recruitment of additional ribosomes (translational capacity). 4. The present review examines the relative importance of translational capacity and translational efficiency in the response of myocytes to acute and chronic demands for increased protein synthesis and the role of these mechanisms in the development of LVH.

Cardiac hypertrophy in vivo is associated with increased expression of the ribosomal gene transcription factor UBF

The ribosomal DNA transcription-specific factor, UBF, is a key target for the regulation of ribosomal RNA synthesis and hypertrophic growth of isolated neonatal cardiomyocytes. In this study, we have examined whether UBF expression is also an important determinant of cardiac growth rates in vivo. We show that rDNA transcription, rRNA synthesis and UBF expression in left ventricular myocytes isolated from mice 1-6 weeks following transverse aortic constriction were significantly increased (2.5-3.5-fold) compared to the levels in myocytes from the left ventricle of sham-operated mice.

Relationship between plasma insulin and left ventricular mass in normotensive participants of the Gubbio Study

BACKGROUND

There is substantial but not conclusive evidence that insulin resistance is related to left ventricular mass (LVM) in hypertensive individuals. To what extent this association is mediated by the relationship between plasma insulin and body size and build is still debated, and is poorly explored in nonhypertensive people.

OBJECTIVE

To explore the relationship between insulin or insulin resistance and LVM in a population-based sample of nonhypertensive participants of the Gubbio Study.

METHOD

Echocardiographic LVM was determined in 91 nondiabetic, nonhypertensive individuals aged 45-54 years, participating in a population-based screening. LVM normalized for height2.7 was used in the analyses; LV hypertrophy was defined as a value of > or = 50 g/m2.7 in men or > or = 47 g/m2.7 in women. Fasting plasma insulin and glucose were measured and the Homeostasis Model Assessment (HOMA) index was used as a measure of insulin resistance.

RESULTS

LVM was positively and significantly correlated with body mass index (BMI) (P < 0.01), waist circumference (P < 0.01) and HOMA index (P < 0.05), whereas correlations with plasma glucose and triglycerides did not reach statistical significance (P = 0.07 for both); all correlations were offset after adjusting for BMI. Fasting plasma insulin and HOMA index were not significantly different in subjects with or without LV hypertrophy (70.8 +/- 27.8 vs. 77.7 +/- 29.6 pmol/l and 2.2 +/- 1.0 vs. 2.6 +/- 1.4, respectively). Bivariate analysis performed stratifying participants above or below the 75th percentile of the sex-specific distribution for BMI (29.1 and 29.4 kg/m2 for males and females, respectively) and plasma insulin (84 pmol/l for either gender), did not result in appreciable differences in LVM due to insulin levels. Similar results were obtained replacing the HOMA index for insulin in the analysis.

CONCLUSION

In nonhypertensive individuals left ventricular mass is not associated with plasma insulin independently of body mass index.