Genetics of coronary artery disease - a clinician's perspective

Bangladeshi Atherosclerosis Biobank and Hub: The BANGABANDHU Study

Background

Genetic factors contribute significantly to the risk of ischaemic heart disease (IHD), which is the leading cause of mortality in Bangladesh. The BANGABANDHU (Bangladeshi Atherosclerosis Biobank AND Hub) study will allow a hypothesis-free genome-wide association study (GWAS) to identify genetic risk factors associated with ischaemic heart disease patients undergoing coronary artery bypass graft (CABG) surgery in Bangladesh.

Methods

 This is a multi-centre population-based case-control study aimed to evaluate 1500 (Fifteen Hundred) adult (≥18 years of age) people divided into 2 study groups: Case/Proband (750 IHD patients undergoing CABG surgery) and Control (750 healthy people). Spouses or family members are preferred as healthy control subjects due to their shared geographic location and similar environmental exposure.

Results

This will be the first largest DNA repository of CABG patients in Bangladesh, and identifying novel gene loci among CABG patients might help to discover novel therapeutic targets for Bangladeshi IHD patients. Further, identifying and comparing novel gene loci among CABG patients with other ancestry might help devise national guidelines for treating coronary artery disease.

Conclusion

Promising current study results will encourage Bangladeshi researchers and pharmaceutical companies to conduct further studies into the genetic basis of Bangladeshi complex coronary artery disease, which might identify novel genes for therapeutic targets for Bangladeshi patients and strengthen the healthcare standards in Bangladesh.

Mendelian randomization studies on coronary artery disease: a systematic review and meta-analysis

BACKGROUND

Coronary artery disease (CAD) remains one of the leading causes of mortality worldwide. We aimed to summarize what is currently known with regard to causal modifiable risk factors associated with CAD in populations of diverse ancestries through conducting a systematic review and meta-analysis of Mendelian randomization (MR) studies on CAD.

METHODS

The databases Embase, Medline, Cochrane Library and Web of Science were searched on the 19th and 20th of December 2022 for MR studies with CAD as a primary outcome; keywords of the search strategy included "coronary artery disease" and "mendelian randomization". Studies were included if they were published in the English language, included only human participants, employed Mendelian randomization as the primary methodology and studied CAD as the outcome of interest. The exclusion criteria resulted in the removal of studies that did not align with the predefined inclusion criteria, as well as studies which were systematic reviews themselves, and used the same exposure and outcome source as another study. An ancestry-specific meta-analysis was subsequently conducted on studies which investigated either body mass index, lipid traits, blood pressure or type 2 diabetes as an exposure variable. Assessment of publication bias and sensitivity analyses was conducted for risk of bias assessment in the included studies.

RESULTS

A total of 1781 studies were identified through the database searches after de-duplication was performed, with 47 studies included in the quantitative synthesis after eligibility screening. Approximately 80% of all included study participants for MR studies on CAD were of European descent irrespective of the exposure of interest, while no study included individuals of African ancestry. We found no evidence of differences in terms of direction of causation between ancestry groups; however, the strength of the respective relationships between each exposure and CAD were different, with this finding most evident when blood pressure was the exposure of interest.

CONCLUSIONS

Findings from this review suggest that patterns regarding the causational relationship between modifiable risk factors and CAD do not differ in terms of direction when compared across diverse ancestry populations. Differences in the observed strengths of the respective relationships however are indicative of the value of increasing representation in non-European populations, as novel genetic pathways or functional SNPs relating to CAD may be uncovered through a more global analysis.

SYSTEMATIC REVIEW REGISTRATION

The protocol for this systematic review was registered to the International Prospective Register of Systematic Reviews (PROSPERO) and is publicly available online (CRD42021272726).

Genome-wide association studies on coronary artery disease: A systematic review and implications for populations of different ancestries

BACKGROUND

Cardiovascular diseases are some of the leading causes of death worldwide, with coronary artery disease leading as one of the primary causes of mortality in both the developing and developed worlds. Despite its prevalence, there is a disproportionately small number of studies conducted in populations of non-European ancestry, with the limited sample sizes of such studies further restricting the power and generalizability of respective findings. This research aimed at understanding the differences in the genetic architecture of coronary artery disease (CAD) in populations of diverse ancestries in order to contribute towards the understanding of the pathophysiology of coronary artery disease.

METHODS

We performed a systematic review on the 6th of October, 2022 summarizing genome-wide association studies on coronary artery disease, while employing the GWAS Catalog as an independent database to support the search. We developed a framework to assess the methodological quality of each study. We extracted and grouped associated single nucleotide polymorphisms and genes according to ancestry groups of participants.

RESULTS

We identified 3100 studies, of which, 36 relevant studies were included in this research. Three of the studies that were included were not listed in the GWAS Catalog, highlighting the value of conducting an independent search alongside established databases in order to ensure the full research landscape has been captured. 743,919 CAD case participants from 25 different countries were analysed, with 61% of the studies identified in this research conducted in populations of European ancestry. No studies investigated populations of Africans living in continental Africa or admixed American ancestry groups besides African-Americans, while limited sample sizes were included of population groups besides Europeans and East Asians. This observed disproportionate population representation highlights the gaps in the literature, which limits our ability to understand coronary artery disease as a global disease. 71 genetic loci were identified to be associated with coronary artery disease in more than one article, with ancestry-specific genetic loci identified in each respective population group which were not detected in studies of other ancestries.

CONCLUSIONS

Although the replication and validation of these variants are still warranted, these finding are indicative of the value of including diverse ancestry populations in GWAS reference panels, as a more comprehensive understanding of the genetic architecture and pathophysiology of CAD can be achieved.

Prognostic Modelling Studies of Coronary Heart Disease—A Systematic Review of Conventional and Genetic Risk Factor Studies

This study aims to provide an overview of multivariable prognostic modelling studies developed for coronary heart disease (CHD) in the general population and to explore the optimal prognostic model by comparing the models’ performance. A systematic review was performed using Embase, PubMed, Cochrane, Web of Science, and Scopus databases until 30 November 2019. In this work, only prognostic studies describing conventional risk factors alone or a combination of conventional and genomic risk factors, being developmental and/or validation prognostic studies of a multivariable model, were included. A total of 4021 records were screened by titles and abstracts, and 72 articles were eligible. All the relevant studies were checked by comparing the discrimination, reclassification, and calibration measures. Most of the models were developed in the United States and Canada and targeted the general population. The models included a set of similar predictors, such as age, sex, smoking, cholesterol level, blood pressure, BMI, and diabetes mellitus. In this study, many articles were identified and screened for consistency and reliability using CHARM and GRIPS statements. However, the usefulness of most prognostic models was not demonstrated; only a limited number of these models supported clinical evidence. Unfortunately, substantial heterogeneity was recognized in the definition and outcome of CHD events. The inclusion of genetic risk scores in addition to conventional risk factors might help in predicting the incidence of CHDs; however, the generalizability of the existing prognostic models remains open. Validation studies for the existing developmental models are needed to ensure generalizability, improve the research quality, and increase the transparency of the study.

Relationship between Long Noncoding RNA H19 Polymorphisms and Risk of Coronary Artery Disease in a Chinese Population: A Case-Control Study

METHODS

We collected 732 samples from Liaoning Province, China, and three polymorphisms in long noncoding RNA H19 were genotyped using the KASP platform.

RESULTS

Our data showed that H19 rs2735971 and rs3024270 variant genotypes were associated with a decreased risk of CAD (rs2735971, P = 0.003, odds ratio (OR) = 0.6195, 95% confidence interval = 0.44 - 0.84; rs3024270, P = 0.030, OR = 0.65, 95% confidence interval = 0.44 - 0.96). No significant association with the risk of CAD was found for H19 rs2839698 polymorphism (P > 0.05). In haplotype analysis, H19 polymorphisms of rs2735971-rs2839698-rs3024270 A-C-C haplotype reduced the risk of CAD by 0.61-fold (P = 0.004, OR = 0.61, 95% confidence interval = 0.43-0.86). In addition, we found that rs2839698 interacted with smoking (P interaction = 0.027), and according to multifactor dimensionality reduction analysis, the three-factor model including H19 rs2839698-smoking-drinking was the best model for the risk of CAD (testing balanced accuracy = 0.6979).

CONCLUSION

Our study demonstrated that some genotypes of H19 rs2735971 and rs3024270 polymorphisms, as well as rs2735971-rs2839698-rs3024270 A-C-C haplotype, were associated with the risk of CAD in a Chinese population, and these genotypes have the potential to be biomarkers for predicting CAD risk. We also found that rs2735971-rs2839698-rs3024270 A-C-C may have a significantly lower risk of CAD. The recessive genetic model of rs3024270 could predict the severity of CAD.

Genetics and pharmacogenetics in the diagnosis and therapy of cardiovascular diseases

Cardiovascular diseases are the main cause of death worldwide. The ability to accurately define individual susceptibility to these disorders is therefore of strategic importance. Linkage analysis and genome-wide association studies have been useful for the identification of genes related to cardiovascular diseases. The identification of variants predisposing to cardiovascular diseases contributes to the risk profile and the possibility of tailored preventive or therapeutic strategies. Molecular genetics and pharmacogenetics are playing an increasingly important role in the correct clinical management of patients. For instance, genetic testing can identify variants that influence how patients metabolize medications, making it possible to prescribe personalized, safer and more efficient treatments, reducing medical costs and improving clinical outcomes. In the near future we can expect a great increment in information and genetic testing, which should be acknowledged as a true branch of diagnostics in cardiology, like hemodynamics and electrophysiology. In this review we summarize the genetics and pharmacogenetics of the main cardiovascular diseases, showing the role played by genetic information in the identification of cardiovascular risk factors and in the diagnosis and therapy of these conditions. (www.actabiomedica.it)

Association of Toll-like receptor 4 polymorphisms with the risk of coronary artery disease in the ethnic Zhuang population of the Guangxi Province of China

OBJECTIVES

Toll-like receptor 4 (TLR4) is known to be involved in the innate immunity and inflammatory responses that plays a crucial role in the pathogenesis of coronary artery disease (CAD). This study aimed to examine the potential relationship of TLR4 polymorphisms and serum TLR4 protein levels and the risk of CAD in the ethnic Zhuang population of China.

METHODS

1171 serum samples were collected from Zhuang patients, including 556 CAD cases (≥50% luminal stenosis of any coronary vessel) and 615 normal healthy controls (subjects with no luminal stenosis in coronary arteries). Detection of TLR4 polymorphisms was by single base extension polymerase chain reaction (Snapshot PCR) and DNA sequencing (rs11536879A/G and rs11536889G/C) gene sequence in all subjects. Serum TLR4 protein concentrations was measured by ELISA.

RESULTS

There are significant differences in the allele and genotype frequencies of TLR4 gene rs11536889 between Chinese Zhuang CAD patients and controls, especially in the males. Male carriers of rs11536879 andrs11536889 variant alleles show an increased risk of CAD compared to non-carriers. Serum TLR4 protein levels of CAD patients are higher than controls and the levels tended to increase with the number of coronary artery lesions. Serum TLR4 protein levels of CAD patients showed no correlation with rs11536879 and rs11536889 polymorphisms.

CONCLUSIONS

The rs11536879 and rs11536889 polymorphisms of TLR4 gene and serum TLR4 protein levels may contribute to the occurrence and development of CAD. However, the rs11536879 and rs11536889 polymorphisms have no significant effects on the expression of serum TLR4 protein in Zhuang patients with CAD.

Genetic architecture: the shape of the genetic contribution to human traits and disease

Genetic architecture describes the characteristics of genetic variation that are responsible for heritable phenotypic variability. It depends on the number of genetic variants affecting a trait, their frequencies in the population, the magnitude of their effects and their interactions with each other and the environment. Defining the genetic architecture of a complex trait or disease is central to the scientific and clinical goals of human genetics, which are to understand disease aetiology and aid in disease screening, diagnosis, prognosis and therapy. Recent technological advances have enabled genome-wide association studies and emerging next-generation sequencing studies to begin to decipher the nature of the heritable contribution to traits and disease. Here, we describe the types of genetic architecture that have been observed, how architecture can be measured and why an improved understanding of genetic architecture is central to future advances in the field.

Role of Cytokine Gene Score in Risk Prediction of Premature Coronary Artery Disease

AIMS

Pro- and anti-inflammatory cytokines play a significant role in early atherosclerosis. Linkage disequilibrium patterns differ between ethnic groups pointing toward the need to develop population-specific gene risk scores. Our objective was to investigate the role of a cytokine gene score in the risk prediction of premature coronary artery disease (PCAD).

METHODS

A case-control study was performed at the National University of Sciences and Technology (NUST) in collaboration with the Cardiovascular Genetics Institute, University College London, United Kingdom. Three hundred forty subjects with >70% stenosis in at least one coronary vessel on angiography were labeled as PCAD cases and compared with 310 angio-negative controls. Genotyping of the rs187238 (interleukin [IL]-18), rs1800795 (IL-6), rs1800629 (tumor necrosis factor [TNF]-alpha), rs1800871 (IL-10), and rs1946519 (IL-18) SNPs was performed using KASPar and TaqMan assays.

RESULTS

The odds ratio for cytokine gene score was significantly higher for PCAD (p = 0.025) when adjusted for age, sex, and ethnicity. There was a highly significant difference in gene risk allele frequency between Pakistanis and Caucasians (Northwick Park Heart Study II [NPHSII]) for rs187238 (IL-18), rs1800795 (IL-6), rs1800629 (TNF-alpha), and rs1800871 (IL-10) (p < 0.01).

CONCLUSIONS

A cytokine gene score has significant discriminatory ability and potential in the risk prediction of PCAD. Cytokine gene risk allele frequencies differ significantly between Pakistanis and Caucasians supporting the need to develop population-specific gene scores.