Genetics of premature myocardial infarction

Prevalent Variants in the LDLR Gene Impair Responsiveness to Rosuvastatin among Family Members of Patients with Premature Myocardial Infarction

BACKGROUND

Familial hypercholesterolemia (FH) is an inherited metabolic disorder characterized by high levels of low-density lipoprotein cholesterol (LDL-c) from birth. About 85% of all FH cases are caused by pathogenic variants in the LDLR gene. Individuals with FH have increased cardiovascular risk, including a high risk of premature myocardial infarction (PMI).

METHODS

We conducted an opportunistic exome screening to identify variants in the LDLR gene among Vietnamese patients with PMI treated at a general hospital in southern Vietnam. A cascade testing for LDLR variants was conducted in their relatives within three generations, and the effects of the LDLR variant on the response to rosuvastatin treatment were also studied using a comparative before-and-after study design on those who were eligible.

RESULTS

A total of 99 participants from the three generations of four PMI patients were recruited, mean age 37.3 ± 18.5 years, 56.6% males. Sanger sequencing revealed two variants in the LDLR gene: variant rs577934998 (c.664T>C), detected in 17 individuals within one family, and variant rs12710260 (c.1060+10G>C), found in 32 individuals (49.5%) in the other three families tested. Individuals harboring the variant c.664T>C had significantly higher baseline LDL-c and total cholesterol levels compared to those with variant c.1060+10G>C (classified as benign) or those without LDLR variants, and among the 47 patients subjected to a 3-month course of rosuvastatin therapy, those with variant c.664T>C had a significantly higher risk of not achieving the LDL-c target after the course of treatment compared to the c.1060+10G>C carriers.

CONCLUSIONS

These findings provide evidence supporting the existence of pathogenic LDLR variants in Vietnamese patients with PMI and their relatives and may indicate the need for personalizing lipid-lowering therapies. Further studies are needed to delineate the extent and severity of the problem.

Effects of familial hypercholesterolemia-associated genes on the phenotype of premature myocardial infarction

Background

The incidence of premature myocardial infarction (PMI) has gradually increased in recent years. Genetics plays a central role in the development of PMI. Familial hypercholesterolemia (FH) is one of the most common genetic disorders of cholesterol metabolism leading to PMI.

Objective

This study investigated the relationship between FH-associated genes and the phenotype of PMI to clarify the genetic spectrum of PMI diseases.

Method

This study enrolled PMI patients (n = 225) and detected the mutations in their FH-associated genes (LDLR, APOB, PCSK9, LDLRAP1) by Sanger sequencing. At the same time, patients free of PMI (non-FH patients, n = 56) were enrolled as control, and a logistic regression analysis was used to identify risk factors associated with PMI. The diagnosis of FH was confirmed using “2018 Chinese expert consensus of FH screening and diagnosis” before the prevalence and clinical features of FH were analyzed.

Results

Pathogenic mutations in LDLR, APOB, PCSK9 and LDLRAP1 genes were found in 17 of 225 subjects (7.6%), and all mutations were loss of function (LOF) and heterozygous. The genotype-phenotype relationship of patients carrying FH-associated mutations showed high heterogeneity. The logistic regression analysis showed that the smoking history, obesity and the family history of premature CHD were independent risk factors of PMI. In this study, a total of 19 patients (8.4%) were diagnosed as FH, and the proportion of smoking subjects in FH patients was higher than that in non-FH patients.

Conclusions

FH-associated gene mutations were present in about 7.6% of Chinese patients with PMI. In addition to genetic factors, smoking history, lifestyle and other environmental factors may play a synergistic role in determining the phenotype of PMI.

Trial registration

Essential gene mutation of cholesterol metabolism in patients with premature myocardial infarction. ChiCTR-OCH-12002349.Registered 26 December 2014, http://www.chictr.org.cn/showproj.aspx?proj=7201.

Genetics-Current and Future Role in the Prevention and Management of Coronary Artery Disease

PURPOSE OF REVIEW

The purpose of this study is to review genetic risk variants for coronary artery disease (CAD) and how they will change the management and prevention of CAD currently and in the future.

RECENT FINDINGS

Through the efforts of international consortia, 58 genetic risk variants for CAD of genome-wide significance have been replicated in appropriate independent populations. Only one third of these variants mediate their risk through known conventional risk factors for CAD. Thus, unknown mechanisms contribute to CAD. Secondly, the genetic risk is proportional to the total number of risk variants rather than the intensity of any risk factor. Thirdly, the availability of the genetic risk variants enables one to perform Mendelian randomization (MR) studies since they are randomized at conception, not confounded, fixed for life, and can be used to determine if a risk factor is causative or just a marker. MR can also be used to determine the safety and efficacy of a gene product targeted for drug therapy. Genetic risk variants have been shown to successfully risk stratify for CAD in both primary and secondary preventions. Contrary to dogma, MR documents that plasma HDL-C is not protective of CAD. The use of genetic risk score (GRS) for CAD is shown to be more effective in risk stratifying for CAD than the Framingham risk score and independent of the conventional risk factors including family history. Furthermore, the GRS predicts the response to statin therapy in primary and secondary preventions. The use of GRS could represent a paradigm shift in the prevention of CAD.

The Relationship Between Gene Polymorphisms and Dipping Profile in Patients With Coronary Heart Disease

BACKGROUND

The aim of this study is to report the relationship between certain single-nucleotide polymorphisms (SNPs) and blunted nighttime blood pressure (BP) fall in patients with coronary artery disease confirmed by coronary angiography.

METHODS

According to the percentage decrease in mean systolic BP (SBP) and diastolic BP (DBP) during the nighttime period, subjects were classified as dippers or nondippers (nighttime relative SBP or DBP decline ≥10% and <10%, respectively). Genetic risk score (GRS18) was constructed to evaluate additive effect of 18 SNPs for nondipping status.

RESULTS

In the present study, 1,345 subjects with coronary heart disease (CHD) were included. During follow-up period (median 8.3 years, interquartile range 5.3-9.0 years), there were 245 all-cause deaths (18.2%) including 114 cardiovascular deaths (8.5%). There were significant differences in the number of revascularizations between nondippers SBP and DBP and dippers SBP and DBP (48.0% vs. 36.4%, P < 0.01). SNPs of the genes, MIA3, MRAS, PCSK9, SMG6, and ZC3HC1, were related to a higher risk of nondipping SBP and DBP status.

CONCLUSIONS

In the present study, polymorphisms of genes related to CHD (MIA3, MRAS, PCSK9, SMG6, and ZC3HC1) were associated with nondipping SBP and DBP profile, and GRS18 was associated with nondipping status. In addition, this profile was related to a higher risk of revascularization.

A genetic basis for coronary artery disease

CAD and cancer account for over one-half of all deaths in the world. It is claimed that the 21st century is the last century for CAD. This is, in part, because CAD is preventable based on randomized, placebo-controlled clinical trials, which show modifying known risk factors such as cholesterol is associated consistently with 40-60% reduction in morbidity and mortality from CAD. Comprehensive prevention will require modifying genetic risk factors that are claimed to account for 40-60% of predisposition to CAD. The 21st century is meeting this challenge with over 50 genetic risk variants discovered and replicated in large genome-wide association studies involving over 200,000 cases and controls. Similarly, 157 genetic variants have been discovered that regulate plasma lipids including, LDL-C, HDL-C, triglycerides, and total cholesterol. A major finding from these studies is that only 15 of the 50 genetic variants for CAD act through known risk factors. Hence, the pathogenesis of CAD in addition to cholesterol and other known risk factors is due to various other factors, many of which remain unknown. Secondly, genes regulating the plasma triglyceride levels are strongly associated with the pathogenesis of CAD. Thirdly, Mendelian randomization studies show no protection from genes that increase plasma HDL cholesterol. This is contrary to current opinion. These genetic risk variants have provided new targets for the development of novel therapies to prevent CAD. Already a new and potent drug has been developed targeting PCSK9, which is in phase 3 clinical trials and shows great efficacy and safety for prevention of CAD. The 21st century is looking very bright for the prevention of CAD.

Precocious virulent coronary atherosclerosis in the very young

BACKGROUND

The incidence of Myocardial Infarction (MI) in patients under the age of 30 has been rarely addressed. Moreover, it is not understood why these patients develop symptomatic Coronary Artery Disease (CAD) at such an early age. Traditional risk factor assessment has not been successful in identifying these patients before they present with MI.

METHODS

Retrospective, single cohort, observational study of 14,704 cardiac catheterizations performed in a community hospital between January 2006-January 2010 identified 12 cases age <30 with MI secondary to a fixed atherosclerotic lesion requiring angioplasty and stenting. The angiograms and charts were reviewed to assess the incidence and frequency of traditional risk factors such as smoking, dyslipidemia and diabetes and family history.

RESULTS

All the patients had single vessel disease. Many of the patients were noted to have traditional CAD risk factors. 2 patients had an intervention and then months later sustained another acute MI secondary to a new culprit lesion despite aggressive risk factor modification.

CONCLUSION

Evaluating patients for premature CAD by screening for traditional risk factors has not effectively identified at risk patients prior to presentation with MI. There is a role for studies evaluating new and novel risk factors and imaging modalities so that these patients can be identified prior to experiencing MI.

Haplotype-based association of four lymphotoxin-alpha gene polymorphisms with the risk of coronary artery disease in Han Chinese

Lymphotoxin-alpha (LTA), a pro-inflammatory cytokine, has been implicated in the pathogenesis of coronary atherosclerosis. Meanwhile, association of some single nucleotide polymorphisms (SNPs) of LTA gene with coronary artery disease (CAD) has been evaluated; however, the results are irreproducible. We therefore investigated the relationship between four SNPs of LTA gene and CAD in Han Chinese: G+10A (rs1800683, 5'-untranslated region), A+80C (rs2239704, 5'-untranslated region), T+496C (Cys13Arg, rs2229094, exon 2), and C+804A (Thr26Asn, rs1041981, exon 3). Genotyping was performed in 438 CAD patients and 330 healthy controls. Single-locus analysis showed that the genotype and allele frequencies of G+10A polymorphism exhibited marginal differences between CAD patients and controls, although no statistical significance was observed after the Bonferroni correction. Logistic regression analysis revealed that GG genotype of G+10A polymorphism was significantly associated with the risk of CAD under the dominant mode, whereas no significant association was detected between A+80C polymorphism and CAD. In contrast, individuals carrying TT or TC genotype of T+496C polymorphism showed a decreased CAD risk relative to those with CC genotype under the recessive mode. Likewise, CC genotype of C+804A polymorphism was associated with a protective effect on CAD under the dominant mode. Further, in haplotype analysis, the haplotype G-C-T-C (in order of rs1800683, rs2239704, rs2229094 and rs1041981) was significantly associated with a decreased risk of CAD after assigning the most common haplotype A-C-T-A as a reference. In conclusion, we show a protective effect of the haplotype G-C-T-C on the occurrence of CAD, suggesting the involvement of LTA in CAD pathogenesis.

The relationship between polymorphisms on chromosome 9p21 and age of onset of coronary heart disease in black and white women

AIM

Genome-wide association studies have identified variants on chromosome 9p21 that are associated with coronary heart disease (CHD). The relationship between these variants and the age of onset of CHD is less clear. The aim of this study was to examine the allelic frequencies and haplotype structure of eight single-nucleotide polymorphisms (SNPs) on chromosome 9p21 in ethnically diverse women. We also explored the relationship between 9p21 SNPs and the age of CHD onset.

RESULTS

There was considerable interethnic allelic and haplotype diversity across the 9p21 locus with only two SNPs (rs10757274 and rs4977574) in perfect linkage disequilibrium in both races, and only a small proportion of the haplotypes shared between the racial groups. With the exception of rs1333040, whites with at least one copy of the 9p21 SNP risk alleles were found to have CHD from 1.45 (rs10116277) to 4.77 (rs2383206) years earlier than those with the wild-type alleles. Blacks carrying at least one copy of the risk allele (92%) for rs1333040 had a CHD age of onset that was 6.5 years earlier than those with the wild-type alleles.

CONCLUSIONS

Different variants on chromosome 9p21 may influence CHD age of onset in whites and blacks.

Heterogeneity of the phenotypic definition of coronary artery disease and its impact on genetic association studies

BACKGROUND

Variability in phenotypic characterization of coronary artery disease (CAD) may contribute to the heterogeneity of genetic association studies, and more consistency in phenotype definitions might improve replication of genetic associations. We assessed the extent of phenotypic heterogeneity and quantified its impact in a large literature sample of association studies.

METHODS AND RESULTS

We searched for large (≥15 studies) meta-analyses of genetic associations and reviewed all studies included therein. From each primary study, we extracted phenotypic definitions, demographics, study design characteristics, and genotypic data. For each association, we assessed the magnitude and heterogeneity of genetic effects within and across CAD phenotypes, using meta-analytic methodologies. A total of 965 individual studies investigating 32 distinct variants in 22 genes were included, from which we grouped CAD phenotypes into 3 categories: acute coronary syndromes (ACS) (426 [44%] studies); angiographically documented disease (323 [34%] studies); and broad, not otherwise specified CAD (216 [22%] studies). These clinical phenotypes were overlapping. Subgroup meta-analyses by phenotype showed discordant results, but phenotypic classification generally explained small proportions of between-study heterogeneity. Differences between phenotypic groups were minimized for associations with robust statistical support. No CAD phenotype was consistently associated with larger or more homogeneous genetic effects in meta-analyses.

CONCLUSIONS

Substantial phenotypic heterogeneity exists in CAD genetic associations, but differences in phenotype definition make a small contribution to between-study heterogeneity. We did not find a consistent effect in terms of the magnitude or homogeneity of summary effects for a specific phenotype to support its preferential use in genetic studies or meta-analyses for CAD.

Varied association of prothrombin G20210A polymorphism with coronary artery disease susceptibility in different ethnic groups: evidence from 15,041 cases and 21,507 controls

Published data on the association between prothrombin G20210A polymorphism and coronary artery disease (CAD) risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total of 42 case-control studies including 15,041 cases and 21,507 controls were included in this meta-analysis. Overall, significantly elevated CAD risk was associated with prothrombin G20210A polymorphism (OR, 1.22; 95% CI 1.07-1.40; P=0.003) when 39 eligible studies were pooled into the meta-analysis. In the subgroup analysis, borderline statistically increased risk was found for myocardial infarction in 22 case-control studies (OR, 1.27; 95% CI 1.00-1.61; P=0.05). When stratified by ethnicity, significantly elevated risk was found in Europeans (OR, 1.19; 95% CI, 1.02-1.38; P=0.02). However, no statistical differences were found among Americans and Asians. In summary, this meta-analysis indicated that prothrombin G20210A allele is a low-penetrant risk factor for developing CAD in Europeans.

[Patient-related cardiovascular risk factors in the HIV-infected population]

The pathogenesis of arteriosclerosis in HIV-infected patients is complex. Both patient-related cardiovascular risk factors (CVRF) established for the general population and those related to highly-active antiretroviral therapy (HAART) and HIV infection per se are involved. Some traditional CVRF are more frequent in HIV infected patients than in the general population. In developed countries, HIV infection is more frequent among men and, due to HAART, their life expectancy has significantly increased. The prevalence of smoking (37-72%) is higher than in the general population, as is that of diabetes mellitus (17%), insulin resistance (17-51%), dyslipidemia (22-49%) and hypertriglyceridemia (34%). The higher prevalence in these patients is probably due to lifestyle and length of exposure to HAART, especially to certain antiretroviral drugs. Although overall cardiovascular risk in patients with HIV remains low, CVRF established for the general population become more important with increasing age. Longitudinal cohort studies indicate the magnitude of the association of these risk factors with cardiovascular disease in patients with HIV infection. In view of all the factors that intervene in HIV infection, specific mathematical models should be designed for this population that would allow individual cardiovascular risk to be calculated in each patient and measures for cardiovascular prevention to be established.

Creating a genetic risk score for coronary artery disease

Coronary artery disease (CAD) and its sequelae represent a significant health burden. Over the past two decades, numerous studies have attempted to link DNA sequence variation with the risk of CAD and related phenotypes. There has been significant evolution in technology from the early linkage studies within kindreds, and now we are able to use high-density genotyping to facilitate large-scale genome-wide association studies. The first novel genetic risk factor for CAD, 9p21.3, has been confirmed, and other loci are awaiting replication studies. The relative importance of each locus from a global standpoint and the incremental information conferred by testing for genetic variants remain to be determined.