Early-onset Heart Disease Research Articles

Measurement of Betaine‐Homocysteine Methyltransferase Activity via Fluorescent Detection of Free Thiols

High concentrations of homocysteine correlate with early onset heart disease and other disorders. The enzyme betaine‐homocysteine methyltransferase (BHMT) consumes homocysteine by transferring a methyl group from betaine to the free thiol group of homocysteine to form methionine. BHMT activity in turn can cause an imbalance of betaine, leading to other health issues like fatty liver and digestive disorders. Clearly, then, understanding the activity and regulation of BHMT can lead to insights into several key health problems. Unfortunately, currently available in vitro BHMT enzyme assays include the use of NMR or HPLC and thus are either slow or not readily scalable.Our goals are to create a new high throughput in vitro assay to measure BHMT activity and to implement this assay to better understand the enzyme’s regulation. This new assay utilizes the dye monobromobimane (mBBr), which becomes fluorescent upon conjugation to a free thiol group. The free thiol of BHMT substate homocysteine is consumed upon methylation; mBBr fluorescence, then, serves as a quantitative reporter of the progress of the BHMT reaction. We have confirmed that mBBr detects the model thiol, L‐cysteine, in a 96‐well plate format, and we can detect sub‐nanomolar amounts of homocysteine deprotected from commercially available DL‐homocysteine thiolactone. This assay has been used to follow the progress of BHMT activity and to investigate the effects of several potential inhibitors. The development of a simple fluorescent assay will enhance the speed of study of this and related enzymes and could spur high throughput searches for small molecule modulators.

Oligogenic inheritance of a human heart disease involving a genetic modifier.

Complex genetic mechanisms are thought to underlie many human diseases, yet experimental proof of this model has been elusive. Here, we show that a human cardiac anomaly can be caused by a combination of rare, inherited heterozygous mutations. Whole-exome sequencing of a nuclear family revealed that three offspring with childhood-onset cardiomyopathy had inherited three missense single-nucleotide variants in the MKL2, MYH7, and NKX2-5 genes. The MYH7 and MKL2 variants were inherited from the affected, asymptomatic father and the rare NKX2-5 variant (minor allele frequency, 0.0012) from the unaffected mother. We used CRISPR-Cas9 to generate mice encoding the orthologous variants and found that compound heterozygosity for all three variants recapitulated the human disease phenotype. Analysis of murine hearts and human induced pluripotent stem cell-derived cardiomyocytes provided histologic and molecular evidence for the NKX2-5 variant's contribution as a genetic modifier.

Three rights can make a wrong

Human Genetics Many diseases are thought to arise from co-inheritance of rare genetic variants that are benign on their own but harmful in combination. This hypothesis has been difficult to validate by functional experiments. Gifford et al. sequenced the genomes of two parents who were asymptomatic and their three children, all of whom had early-onset heart disease. They identified three likely culprit genetic variants, two in transcription factor genes linked to heart development and one in a gene encoding a muscle structural protein. When they introduced these three variants together into mice by gene editing, the mice developed heart disease resembling that seen in the children. Science , this issue p. [865][1] [1]: /lookup/doi/10.1126/science.aat5056

Interdisciplinary Models for Research and Clinical Endeavors in Genomic Medicine: A Scientific Statement From the American Heart Association.

The completion of the Human Genome Project has unleashed a wealth of human genomics information, but it remains unclear how best to implement this information for the benefit of patients. The standard approach of biomedical research, with researchers pursuing advances in knowledge in the laboratory and, separately, clinicians translating research findings into the clinic as much as decades later, will need to give way to new interdisciplinary models for research in genomic medicine. These models should include scientists and clinicians actively working as teams to study patients and populations recruited in clinical settings and communities to make genomics discoveries-through the combined efforts of data scientists, clinical researchers, epidemiologists, and basic scientists-and to rapidly apply these discoveries in the clinic for the prediction, prevention, diagnosis, prognosis, and treatment of cardiovascular diseases and stroke. The highly publicized US Precision Medicine Initiative, also known as All of Us, is a large-scale program funded by the US National Institutes of Health that will energize these efforts, but several ongoing studies such as the UK Biobank Initiative; the Million Veteran Program; the Electronic Medical Records and Genomics Network; the Kaiser Permanente Research Program on Genes, Environment and Health; and the DiscovEHR collaboration are already providing exemplary models of this kind of interdisciplinary work. In this statement, we outline the opportunities and challenges in broadly implementing new interdisciplinary models in academic medical centers and community settings and bringing the promise of genomics to fruition.

Comments on: Association Study between Coronary Artery Disease and rs1333049 and rs10757274 Polymorphisms at 9p21 Locus in South-West Iran.

Foroughmand et al. (1) have recently reported association between coronary artery disease (CAD) and two well-known single nucleotide polymorphisms (SNPs) on chromosome 9p21.3 in subjects from South-West Iran. We doubt the validity of their findings. Genotyping was done using ARMS-PCR for rs1333049 and rs10757274 in their study. When we first looked at the genotype frequencies, we observed a substantial excess of heterozygote subjects for both SNPs. Specifically, the relative excess of heterozygosity (REH) (2), a measure for the strength of deviation from Hardy-Weinberg equilibrium (HWE), was approximately 137% for rs1333049 in controls (REH=2.3688, Table 1). In contrast, we did not observe any deviation from HWE in our own studies (3, 4). We additionally conducted a short literature search to identify other studies from Asia, which reported genotype frequencies in controls for rs1333049. These studies are summarized in table 1. None of these studies shows a deviation from HWE in their control groups (all P>0.05). In summary, only the recent study by Foroughmand and colleagues (1) shows a marked deviation from HWE in controls with this deviation observed for both reported SNPs. Possible reasons for deviations from HWE have been summarized, e.g., in Ziegler et al. (2). The most likely cause for such a strong deviation from HWE is genotyping errors, especially because genotyping by ARMS-PCR plus gel electrophoresis is prone to such errors. However, REH could also be caused by population specifics, which has been discussed by Namipashaki et al. (5). In any case, we (2) and others (5) recommend the investigation of HWE in population-based genetic association studies to improve quality and reliability of the research results.

Association Study between Coronary Artery Disease and rs1333049 and rs10757274 Polymorphisms at 9p21 Locus in South-West Iran.

Coronary artery disease (CAD) is a multi-factorial and heterogenic disease with atherosclerosis plaques formation in internal wall of coronary artery. Plaque formation results to limitation of the blood reaching to myocardium leading to appearance of some problems, such as ischemia, sudden thrombosis veins and myocardial infarction (MI). Several environmental and genetic factors are involved in prevalence and incident of CAD as follows: hypertension, high low density lipoprotein-cholesterol (LDL-C), age, diabetes mellitus, family history of early-onset heart disease and smoking. According to genome wide association studies (GWAS), five polymorphisms in the 9p21 locus seem to be associated with the CAD. We aimed to evaluate the remarkable association of two polymorphisms at 9p21 locus, rs1333049 and rs10757274, with CAD. This experimental study was conducted in Golestan, Aria Hospitals and Genetics Lab of Shahid Chamran University in the city of Ahvaz, Iran, in 2010- 2011. The collected blood samples belonging to 170 CAD patients (case group) and 100 healthy individuals (control group) were analyzed by tetra-primer amplification refractory mutation system (ARMS)-polymerase chain reaction (PCR) technique. The results were analyzed using software package used for statistical analysis (SPSS; SPSS Inc., USA) version 16. A value of p<0.05 and an odd ratio (OR) with 95% confidence intervals (CI) were considered significant. The frequencies of CC, CG and GG genotypes for rs1333049 polymorphism in patients were 18.2, 65.3 and 16.5%, while in controls, the related values were 25, 67 and 8%, respectively. GG genotypes of rs1333049 polymorphism in CAD patients were more than control cases (OR: 0.354, 95%CI: 0.138-0.912, p=0.032). The frequencies of AA, AG and GG genotypes for rs10757274 in CAD patients were 8.2, 58.3 and 33.5%, while in controls, the related values were 35, 63 and 2%, respectively. GG Genotype in rs10757274 polymorphism in CAD patients was found more than control cases (OR: 0.014, 95% CI: 0.003 -0.065, p=0.0001). The rs1333049 polymorphism at 9p21 locus shows a weak association with CAD, whereas rs10757274 polymorphism reveals a significant association with CAD. These variants may help the identification of patients with increased risk for coronary artery disease.

Patient accounts of diagnostic testing for familial hypercholesterolaemia: comparing responses to genetic and non-genetic testing methods

BackgroundContinuing developments in genetic testing technology together with research revealing gene-disease associations have brought closer the potential for genetic screening of populations. A major concern, as with any screening programme, is the response of the patient to the findings of screening, whether the outcome is positive or negative. Such concern is heightened for genetic testing, which it is feared may elicit stronger reactions than non-genetic testing.MethodsThis paper draws on thematic analysis of 113 semi-structured interviews with 39 patients being tested for familial hypercholesterolaemia (FH), an inherited predisposition to early-onset heart disease. It examines the impact of disease risk assessments based on both genetic and non-genetic information, or solely non-genetic information.ResultsThe impact of diagnostic testing did not seem to vary according to whether or not genetic information was used. More generally, being given a positive or negative diagnosis of FH had minimal discernible impact on people's lives as they maintained the continuity of their beliefs and behaviour.ConclusionsThe results suggest that concerns about the use of genetic testing in this context are unfounded, a conclusion that echoes findings from studies in this and other health contexts.

Childhood Cancer Survivors at Risk for Early-Onset Heart Disease

Childhood Cancer Survivors at Risk for Early-Onset Heart Disease

Impact of Apolipoprotein(a) Isoform Size Heterogeneity on the Lysine Binding Function of Lipoprotein(a) in Early Onset Coronary Artery Disease

Elevated plasma Lp(a) is an independent risk factor for cardiovascular disease. Unique to Lp(a) is the apoprotein, apo(a) which can vary from 250 to 800 kDa in molecular weight. Small isoforms are also associated with the risk of cardiovascular disease. The purpose of this study was to examine the association of Lp(a) concentration, apo(a) size, and Lp(a) lysine-binding site(s) (LBS) function in patients with early onset heart disease, and age-matched controls. Mean values of Lp(a) were significantly higher in the patients than for the age-matched group. The smallest molecular weight isoform for each subject had significantly fewer kringles for the patients than the age-matched controls. There was a significant correlation between LBS activity and kringle number in the single-banded phenotypes of the patients, but not the controls. LBS activity was significantly higher in patients with small isoforms (< or =18 kringles) compared to controls. The odds ratio for coronary artery disease for high LBS activity and high Lp(a) concentration was 4.4 (p = 0.002) and for high LBS activity and small isoforms was 10.1 (p = 0.002). In the patients, Lp(a) concentration was higher, apo(a) size was smaller, and LBS activity higher in the small isoforms compared to the controls. This study suggests an association of high LBS activity in small isoforms of Lp(a) with disease in humans.

The use of single nucleotide polymorphisms in the isolation of common disease genes.

The numerous successes using positional cloning to identify genes mutated in monogenic disorders has galvanised geneticists to start using similar techniques to tackle common complex diseases such as asthma, osteoarthritis, depression and early onset heart disease. The technology is currently at an intermediate stage in which linkage in family studies is being supplemented with locus-specific association studies in populations, enabling accurate localisation of the disease causing or susceptibility gene. These studies are often labour and time intensive unless focus is placed on biological candidate genes. In general, most candidate gene studies for common diseases have been unrewarding. However, single nucleotide polymorphisin (SNP) mapping has accelerated complex disease gene localisation, providing a tool to narrow the linkage region by the detection of multiple SNPs associated with the disease in a relatively small linkage disequilibriuln (LD) region. Identification of susceptibility genes will enable a better understanding of the mechanisms of the disease processes and will facilitate the discovery of new and more efficacious medicines. Whole genome SNP maps will also allow abbreviated SNP profiles to be developed for pharmacogenetic applications, enabling physicians to tailor therapeutic regimens (i.e., identify patients likely to receive therapeutic benefit and not suffer adverse reactions).