A kinesin family member 6 variant is associated with coronary heart disease in the Women's Health Study

Kif6 regulates cilia motility and polarity in brain ependymal cells

Ependymal cells, lining brain ventricular walls, display tufts of cilia that beat in concert promoting laminar Cerebrospinal fluid (CSF) flow within brain ventricles. The ciliary axonemes of multiciliated ependymal cells display a 9+2 microtubule array common to motile cilia. Dyneins and kinesins are ATPase microtubule motor proteins that promote the rhythmic beating of cilia axonemes. Despite common consensus about the importance of axonemal dynein motor proteins, little is known about how Kinesin motors contribute to cilia motility. Here, we define the function of Kinesin family member 6 (Kif6) using a mutation that lacks a highly conserved C-terminal tail domain ( Kif6 p.G555fs ) and which displays progressive hydrocephalus in mice. An analogous mutation was isolated in a proband displaying macrocephaly, hypotonia, and seizures implicating an evolutionarily conserved function for Kif6 in neurodevelopment. We find that loss of Kif6 function caused decreased ependymal cilia motility and subsequently decreased fluid flow on the surface of brain ventricular walls. Kif6 protein was localized at ependymal cilia and displayed processive motor movement (676 nm/s) on microtubules in vitro . Loss of the Kif6 C-terminal tail domain did not affect the initial ciliogenesis in vivo , but did result in defects in cilia orientation, the formation of robust apical actin networks, and stabilization of basal bodies at the apical surface. This suggests a novel role for the Kif6 motor in maintenance of ciliary homeostasis of ependymal cells.

Summary statement

We found that Kif6 is localized to the axonemes of ependymal cells. In vitro analysis shows that Kif6 moves on microtubules and that its loss mice decrease cilia motility and cilia-driven flow, resulting in hydrocephalus.

Single-cell genomics illustrates heterogeneous phenotypes of myocardial fibroblasts under ischemic insults

Myocardial regenerative strategies are promising where the choice of ideal cell population is crucial for successful translational applications. Herein, we explored the regenerative/repair responses of infarct zone cardiac fibroblast(s) (CF) by unveiling their phenotype heterogeneity at single-cell resolution. CF were isolated from the infarct zone of Yucatan miniswine that suffered myocardial infarction, cultured under simulated ischemic and reperfusion, and grouped into control, ischemia, and ischemia/reperfusion. The single-cell RNA sequencing analysis revealed 19 unique cell clusters suggesting distinct subpopulations. The status of gene expression (log2 fold change (log2 FC) > 2 and log2 FC < -2) was used to define the characteristics of each cluster unveiling with diverse features, including the pro-survival/cardioprotective (Clusters 1, 3, 5, 9, and 18), vasculoprotective (Clusters 2 and 5), anti-inflammatory (Clusters 4 and 17), proliferative (Clusters 4 and 5), nonproliferative (Clusters 6, 8, 11, 16, 17, and 18), proinflammatory (Cluster 6), profibrotic/pathologic (Clusters 8 and 19), antihypertrophic (Clusters 8 and 10), extracellular matrix restorative (Clusters 9 and 12), angiogenic (Cluster 16), and normal (Clusters 7 and 15) phenotypes. Further understanding of these unique phenotypes of CF will provide significant translational opportunities for myocardial regeneration and cardiac management.

KIF6 Trp719Arg Genetic Variant Increases Risk for Thoracic Aortic Dissection

BACKGROUND

KIF6 (kinesin family member 6), a protein coded by the KIF6 gene, serves an important intracellular function to transport organelles along microtubules. In a pilot study, we found that a common KIF6 Trp719Arg variant increased the propensity of thoracic aortic aneurysms (TAA) to suffer dissection (AD). The present study aims for a definite investigation of the predictive ability of KIF6 719Arg vis à vis AD. Confirmatory findings would enhance natural history prediction in TAA.

METHODS

1108 subjects (899 aneurysm and 209 dissection patients) had KIF6 719Arg variant status determined.

RESULTS

The 719Arg variant in the KIF6 gene correlated strongly with occurrence of AD. Specifically, KIF6 719Arg positivity (homozygous or heterozygous) was substantially more common in dissectors (69.8%) than non-dissectors (58.5%) (p = 0.003). Odds ratios (OR) for suffering aortic dissection ranged from 1.77 to 1.94 for Arg carriers in various dissection categories. These high OR associations were noted for both ascending and descending aneurysms and for homozygous and heterozygous Arg variant patients. The rate of aortic dissection over time was significantly higher for carriers of the Arg allele (p = 0.004). Additionally, Arg allele carriers were more likely to reach the combined endpoint of dissection or death (p = 0.03).

CONCLUSIONS

We demonstrate the marked adverse impact of the 719Arg variant of the KIF6 gene on the likelihood that a TAA patient will suffer aortic dissection. Clinical assessment of the variant status of this molecularly important gene may provide a valuable "non-size" criterion to enhance surgical decision making above and beyond the currently used metric of aortic size (diameter).

Impact of 719Trp>Arg Polymorphism of KIF 6 Gene on Contrast Induced Nephropathy in Patients Undergoing Coronary Angiography or Percutaneous Coronary Intervention

Background:

The identification of preventive strategies, such as statin therapy, is crucial for the management of contrast-induced nephropathy (CIN). Several studies showed the association between KIF6 polymorphism (replacement of Trp719 with Arg) and an increased cardiovascular risk, while others showed a correlation between ‘pleiotropic’ effects of statins and a reduction in cardiovascular events in the population with the risk allele due to the documented modulation of response to statin by KIF6 polymorphism. Aim of this study is to assess the impact of KIF6 polymorphism on the development of CIN.

Methods:

We analysed 1253 consecutive patients undergoing coronary angiography/PCI. Serum creatinine was collected at baseline, 24 and 48 hours after contrast exposure. We identified the different allelic patterns and assessed the incidence of CIN (absolute increase of 0.5mg/dL or relative >25% in creatinine at 24 and 48h).

Results:

KIF6 Arg mutation was found in 669 patients (heterozygotes n = 525, homozygotes n = 144). The total prevalence of CIN was 12.5% and we did not find any association between KIF6 polymorphism and CIN development (11.3%, 13.7%, 13.2% p = 0.30). At subgroups analysis among statin ‘naïve’ patients we found a higher prevalence of CIN in homozygous patients as compared to wild-type (20.7% vs 11.3%, p = 0.05), while opposite results were observed among patients with statin therapy (8.6% vs 13.2%, p = 0.28).

Conclusion:

KIF6 homozygous Arg was associated with a significant increase in the risk of CIN only among statin naive patients. Future studies are needed to evaluate the beneficial effects of statin especially in this subset of patients.

Coronary Heart Disease in Type 2 Diabetes Mellitus: Genetic Factors and Their Mechanisms, Gene-Gene, and Gene-Environment Interactions in the Asian Populations

Asians are more susceptible to type 2 diabetes mellitus (T2D) and its coronary heart disease (CHD) complications than the Western populations, possibly due to genetic factors, higher degrees of obesity, insulin resistance, and endothelial dysfunction that could occur even in healthy individuals. The genetic factors and their mechanisms, along with gene-gene and gene-environment interactions associated with CHD in T2D Asians, are yet to be explored. Therefore, the objectives of this paper were to review the current evidence of genetic factors for CHD, summarize the proposed mechanisms of these genes and how they may associate with CHD risk, and review the gene-gene and gene-environment interactions in T2D Asians with CHD. The genetic factors can be grouped according to their involvement in the energy and lipoprotein metabolism, vascular and endothelial pathology, antioxidation, cell cycle regulation, DNA damage repair, hormonal regulation of glucose metabolism, as well as cytoskeletal function and intracellular transport. Meanwhile, interactions between single nucleotide polymorphisms (SNPs) from different genes, SNPs within a single gene, and genetic interaction with environmental factors including obesity, smoking habit, and hyperlipidemia could modify the gene's effect on the disease risk. Collectively, these factors illustrate the complexities of CHD in T2D, specifically among Asians.

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.

Relationship between Lipid Phenotypes, Overweight, Lipid Lowering Drug Response and KIF6 and HMG-CoA Genotypes in a Subset of the Brisighella Heart Study Population

The existence of genetic traits might explain the susceptibility to develop hypercholesterolemia and the inter-individual differences in statin response. This study was performed to evaluate whether individuals' polymorphisms in HMG-CoA and KIF6 genes are independently associated with hypercholesterolemia, other lipid-associated traits, and statin response in unselected individuals enrolled in the Brisighella heart study (Survey 2012). A total of 1622 individuals, of which 183 under statin medication, were genotyped for a total of five polymorphisms (KIF6 rs20455, rs9471077, rs9462535; HMG-CoA rs3761740, rs3846662). The relationships between the five loci and clinical characteristics were analyzed. The principal basic parameters calculated on 12 h fasting blood included total cholesterol (TC), High Density Lipoprotein Cholesterol (HDL-C), Low-Density Lipoprotein Cholesterol (LDL-C), and triglycerides (TG). Hypercholesterolemia was defined as a TC >200 mg/dL or use of lipid-lowering medication. 965 individuals were characterized by hypercholesterolemia; these subjects were significantly older (p < 0.001), with body mass index (BMI) and waist circumference significantly higher (p < 0.001) compared to the others. HMG-CoA rs3846662 GG genotype was significantly over-represented in the hypercholesterolemic group (p = 0.030). HMG-CoA rs3846662 genotype was associated with the level of TC and LDL-C. Furthermore, in the same subset of untreated subjects, we observed a significant correlation between the KIF6 rs20455 and HDL-C. KIF6 variants were associated with a significantly lower (rs20455) or higher (rs9471077 and rs9462535) risk of obesity, in males only. No association between responsiveness to statins and the polymorphisms under investigation were observed. Our results showed associations between HMG-CoA rs3846662 and KIF6 rs20455 and lipid phenotypes, which may have an influence on dyslipidemia-related events. Moreover, this represents the first study implicating KIF6 variants with obesity in men, and point to the possible involvement of this genetic locus in the known gender-related differences in coronary artery disease.

Personalized Management of Cardiovascular Disorders

Personalized management of cardiovascular disorders (CVD), also referred to as personalized or precision cardiology in accordance with general principles of personalized medicine, is selection of the best treatment for an individual patient. It involves the integration of various "omics" technologies such as genomics and proteomics as well as other new technologies such as nanobiotechnology. Molecular diagnostics and biomarkers are important for linking diagnosis with therapy and monitoring therapy. Because CVD involve perturbations of large complex biological networks, a systems biology approach to CVD risk stratification may be used for improving risk-estimating algorithms, and modeling of personalized benefit of treatment may be helpful for guiding the choice of intervention. Bioinformatics tools are helpful in analyzing and integrating large amounts of data from various sources. Personalized therapy is considered during drug development, including methods of targeted drug delivery and clinical trials. Individualized recommendations consider multiple factors - genetic as well as epigenetic - for patients' risk of heart disease. Examples of personalized treatment are those of chronic myocardial ischemia, heart failure, and hypertension. Similar approaches can be used for the management of atrial fibrillation and hypercholesterolemia, as well as the use of anticoagulants. Personalized management includes pharmacotherapy, surgery, lifestyle modifications, and combinations thereof. Further progress in understanding the pathomechanism of complex cardiovascular diseases and identification of causative factors at the individual patient level will provide opportunities for the development of personalized cardiology. Application of principles of personalized medicine will improve the care of the patients with CVD.

KIF6 719Arg Genetic Variant and Risk for Thoracic Aortic Dissection

BACKGROUND

Carriers of the 719Arg variant in KIF6, compared with noncarriers, have been reported to be at greater risk for coronary heart disease (CHD) in six prospective studies. Because CHD, thoracic aortic dissection, and nondissection thoracic aortic aneurysm share some risk factors and aspects of pathophysiology, we investigated whether carriers of the 719Arg variant also have greater odds of thoracic aortic dissection or nondissected thoracic aortic aneurysm than noncarriers.

METHODS

We genotyped 140 thoracic aortic dissection cases, 497 nondissection thoracic aortic aneurysm cases, and 275 disease-free controls collected in the United States, Hungary, and Greece and investigated the association between KIF6 719Arg carrier status and thoracic aortic dissection, and between KIF6 719Arg carrier status and nondissection thoracic aortic aneurysm, using logistic regression models adjusted for age, sex, hypertension, smoking, and country.

RESULTS

The odds of aortic dissection were two-fold greater in KIF6 719Arg carriers compared with noncarriers (odds ratio (OR) 2.14, 95% confidence interval (CI) 1.18-3.9). To account for the potential of concomitant CHD to confound the association between the KIF6 719Arg and thoracic aortic dissection, we repeated the analysis after removing subjects with concomitant CHD; the estimates for association of KIF6 719Arg carrier status remained essentially the same (OR 2.04, 95% CI 1.11-3.77). In contrast, KIF6 719Arg carrier status was not associated with risk for nondissection thoracic aortic aneurysm.

CONCLUSIONS

We observed an association of the KIF6 719Arg genetic variant with thoracic aortic dissection in this multicenter case-control study. This association may enhance our management of patients with thoracic aortic disease.

Investigation of KIF6 Trp719Arg gene polymorphism in a case-control study of coronary artery disease and non-fatal myocardial infarction in the Eastern Province of Saudi Arabia

BACKGROUND

Kinesin-like protein 6 (KIF6), a member of the kinesin superfamily, is involved in intracellular transport. A few prospective studies have shown the KIF6 variant Trp719Arg (rs20455) to be associated with coronary artery disease (CAD) in Caucasian populations. However, recent genome-wide association studies on CAD have not proven these associations.

OBJECTIVES

Since the role of KIF6 719Arg allele in other ethnic populations is largely unknown, we sought to determine whether the KIF6 719Arg allele is associated with CAD in an ethnic Middle Eastern population.

DESIGN

Case-control study.

SETTING

CAD patients and control subjects from King Fahd Hospital of the University, Al-Khobar, Saudi Arabia.

PATIENTS AND METHODS

The study population included angiographically defined CAD patients (n=1002) and controls (n=984) with a normal electrocardiogram.

MAIN OUTCOME MEASURE(S)

Association of KIF6 Trp719Arg mutation with CAD.

RESULTS

The KIF6 Trp719Arg polymorphism was not associated with CAD (OR 0.976, 95% CI 0.861-1.105; P=.704). In addition, KIF6 Trp719Arg polymorphism showed a lack of association even in stratified myocardial infarction patients (n=802) (OR 1.006, 95% CI 0.881-1.148; P=.929) in comparison to controls.

CONCLUSIONS

The absence of Trp719Arg polymorphism association with CAD and CAD in stratified myocardial infarction cases indicates that the polymorphism is not associated with an increased risk among CAD patients from the Eastern Province of Saudi Arabia.

LIMITATIONS

Unavailability of data on statin usage among the patient population.

Genetic Testing in Hyperlipidemia

Hereditary dyslipidemias are often underdiagnosed and undertreated, yet with significant health implications, most importantly causing preventable premature cardiovascular diseases. The commonly used clinical criteria to diagnose hereditary lipid disorders are specific but are not very sensitive. Genetic testing may be of value in making accurate diagnosis and improving cascade screening of family members, and potentially, in risk assessment and choice of therapy. This review focuses on using genetic testing in the clinical setting for lipid disorders, particularly familial hypercholesterolemia.

The Trp719Arg polymorphism of the KIF6 gene and coronary heart disease risk: systematic review and meta-analysis

BACKGROUND

Genetic factors play an important role in the pathogenesis of coronary heart disease (CHD). Kinesin-like protein 6 (KIF6) is a new candidate gene for CHD, since it has been identified as a potential risk factor. The aim of this study was to perform a systematic review and meta-analysis of previously published association studies between the Trp719Arg polymorphism of KIF6 and the development of CHD.

METHODS

Studies and abstracts investigating the relationship between the Trp719Arg polymorphism of KIF6 and subsequent risk for development of CHD were reviewed. Electronic search from Pubmed and EBSCO databases was performed between 1993 and 2014 to identify studies that fulfilled the inclusion criteria. To analyze the association we used the models: allelic, additive, dominant and recessive. Moreover, we conducted a sub-analysis by populations using the same four models.

RESULTS

Twenty-three studies were included in the meta-analysis. The Trp719Arg polymorphism showed a significant association with CHD when the analysis comprised the population with myocardial infarction (MI) and the additive genetic model was used. Moreover, this polymorphism showed a protective association with CHD when the analysis comprised the whole population using the recessive genetic model.

CONCLUSIONS

Our findings indicate that the Trp719Arg polymorphism of the KIF6 gene is an important risk factor for developing MI and that allele 719Arg may have a protective association to present CHD in all populations.

PROSPERO REGISTRATION

CRD42015024602.

Genotyping and meta-analysis of KIF6 Trp719Arg polymorphism in South Indian Coronary Artery Disease patients: A case-control study

The KIF6 719Arg allele is an interesting genomic variant widely screened in various populations and is reported to be associated with the risk of Coronary Artery Disease (CAD) and statin treatment outcome. Recent population based clinical studies and large-scale meta-analyses pondered over the role of 719Arg variant in CAD risk and treatment response. We screened the KIF6 Trp719Arg polymorphism (rs20455) in south Indian CAD patients in a case–control approach. A total of 1042 samples (510 CAD patients and 532 controls) were screened for the KIF6 Trp719Arg SNP by TaqMan SNP genotyping assay, followed by meta-analysis of the genotype data of non-Europeans reports. The 719Arg risk genotype (GG) was observed in 29.6% of CAD cases and in 30.1% of controls with an odds ratio (OR) of 1.07 (95% CI: 0.76–1.50), p value = 0.709. No significant difference in the genotype frequency was observed between CAD and controls in both dominant model (AG + GG vs AA) and allelic model (719Arg vs 719Trp) with an OR of 1.11 (p = 0.491) and 1.03 (p = 0.767), respectively. The covariate analysis indicated that smoking & alcohol consumption increased the risk for MI among CAD patients. Meta-analysis showed that the KIF6 719Arg allele is not associated with CAD risk in both fixed effect (p = 0.515, OR = 1.023, 95% CI = 0.956–1.094) and random effect (p = 0.547, OR = 1.022, 95% CI = 0.953–1.096). The symmetrical shape of the Egger's funnel plots revealed that there is no publication bias. These results suggest that there is no association of KIF6 719Arg allele with CAD risk in South Indian population and the meta-analysis confirms the same among non-European population.

•

First study to screen for KIF6Trp719Arg SNP in south Indian population

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KIF6Arg variant is not a risk factor for south Indian CAD patients.

•

Meta-analysis showed no association of KIF6Arg allele in non-European CAD populations.

•

Smoking and alcoholic status were strong risk factors for MI; whereas KIF6 status is not.

Kinesin family member 6 (kif6) is necessary for spine development in zebrafish

BACKGROUND

Idiopathic scoliosis is a form of spinal deformity that affects 2-3% of children and results in curvature of the spine without structural defects of the vertebral units. The pathogenesis of idiopathic scoliosis remains poorly understood, in part due to the lack of a relevant animal model.

RESULTS

We performed a forward mutagenesis screen in zebrafish to identify new models for idiopathic scoliosis. We isolated a recessive zebrafish mutant, called skolios, which develops isolated spinal curvature that arises independent of vertebral malformations. Using meiotic mapping and whole genome sequencing, we identified a nonsense mutation in kinesin family member 6 (kif6(gw326) ) unique to skolios mutants. Three additional kif6 frameshift alleles (gw327, gw328, gw329) were generated with transcription activator-like effector nucleases (TALENs). Zebrafish homozygous or compound heterozygous for kif6 frameshift mutations developed a scoliosis phenotype indistinguishable from skolios mutants, confirming that skolios is caused by the loss of kif6. Although kif6 may play a role in cilia, no evidence for cilia dysfunction was seen in kif6(gw326) mutants.

CONCLUSIONS

Overall, these findings demonstrate a novel role for kif6 in spinal development and identify a new candidate gene for human idiopathic scoliosis.

Organ system heterogeneity DB: a database for the visualization of phenotypes at the organ system level

Perturbations of mammalian organisms including diseases, drug treatments and gene perturbations in mice affect organ systems differently. Some perturbations impair relatively few organ systems while others lead to highly heterogeneous or systemic effects. Organ System Heterogeneity DB (http://mips.helmholtz-muenchen.de/Organ_System_Heterogeneity/) provides information on the phenotypic effects of 4865 human diseases, 1667 drugs and 5361 genetically modified mouse models on 26 different organ systems. Disease symptoms, drug side effects and mouse phenotypes are mapped to the System Organ Class (SOC) level of the Medical Dictionary of Regulatory Activities (MedDRA). Then, the organ system heterogeneity value, a measurement of the systemic impact of a perturbation, is calculated from the relative frequency of phenotypic features across all SOCs. For perturbations of interest, the database displays the distribution of phenotypic effects across organ systems along with the heterogeneity value and the distance between organ system distributions. In this way, it allows, in an easy and comprehensible fashion, the comparison of the phenotypic organ system distributions of diseases, drugs and their corresponding genetically modified mouse models of associated disease genes and drug targets. The Organ System Heterogeneity DB is thus a platform for the visualization and comparison of organ system level phenotypic effects of drugs, diseases and genes.

KIF6 719Arg Carrier Status Association with Homocysteine and C-Reactive Protein in Amnestic Mild Cognitive Impairment and Alzheimer's Disease Patients

Recent research has demonstrated associations between statin use, KIF6 719Arg carrier status, and cholesterol levels and amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) patients. The association between 719Arg carrier status with homocysteine (tHcy) and c-reactive protein (CRP) levels in aMCI and AD has not been previously investigated. Data from 175 aMCI and AD patients were used for the analysis. 719Arg carriers had significantly lower levels of tHcy than noncarriers (P = 0.02). No significant difference in CRP levels between 719Arg carriers and noncarriers was present (P = 0.37). Logistic regression yielded no significant effect for 719Arg status on CRP [OR = 1.79 (0.85, 3.83), P = 0.13] but did demonstrate a significant effect for tHcy [OR = 0.44 (0.23, 0.83), P = 0.01] after adjusting for ApoE ε4 carrier status, age, gender, and statin use. This study is the first to explore the relationship between KIF6 719Arg carrier status with tHcy and CRP levels. 719Arg carriers were more likely to have normal tHcy levels after adjusting for ApoE ε4 status, age, gender, and statin use. These results suggest that the KIF6 gene might influence cardiovascular pathways associated with AD.

The Association between KIF6 Single Nucleotide Polymorphism rs20455 and Serum Lipids in Filipino-American Women

The Trp719Arg allele of KIF6 rs20455, a putative risk factor for CHD especially in those with elevated low-density lipoprotein cholesterol (LDL-C), was investigated in Filipino-American women (FAW, n = 235) participating in health screenings in four cities. The rs20455 genotype of each subject was determined by a multiplex assay using a Luminex-OLA procedure. The risk allele Trp719Arg was present in 77% of the subjects. The genotype distribution was 23% Trp/Trp, 51% Arg/Trp, and 26% Arg/Arg. Genotype did not predict the presence of CHD risk factors. Moreover, LDL-C, HDL-C, and triglycerides mean values did not vary as a function of genotype. However, those with the Arg/Arg genotype on statin medication exhibited a significantly higher mean triglycerides level (P < 0.01). Approximately 60% of participants regardless of genotype exhibited LDL-C levels ≥100 mg/dL but were not taking medication. Approximately 43% of those with the Trp719Arg risk allele on statins exhibited elevated LDL-C levels. Our study suggests that the Trp719Arg allele of KIF 6 rs20455 is common among Filipino-American women; thus, even with borderline LDL-C levels would benefit from statin treatment. Secondly, many participants did not exhibit guideline recommended LDL-C levels including many who were on statin drugs.

Novel KIF6 polymorphism increases susceptibility to type 2 diabetes mellitus and coronary heart disease in Han Chinese men

OBJECTIVES

The effect of the KIF6 polymorphism Trp719Arg on the risk of T2DM and T2DM with CHD remains unclear.

METHODS

946 unrelated subjects of Han Chinese origin were recruited, comprising 346 controls, 312 T2DM, and 288 T2DM + CHD patients. Genotyping was performed by high-resolution melting curve analysis using real-time qPCR. The impact of the variant on T2DM/T2DM + CHD and gene-sex interaction were evaluated by stepwise multiple regression analysis.

RESULTS

The frequencies of the Trp719 allele in T2DM and T2DM + CHD patients were similar to the control group, whereas significantly increased 719Arg allele frequencies were observed in male T2DM and T2DM + CHD patients compared with the corresponding control group. Further sex partition analysis revealed that only male 719Arg allele carriers had approximately 3-fold and 5-fold higher risk of T2DM and T2DM + CHD, respectively, than noncarriers. There was also a significant association between carriers and higher TG and lower HDL-C levels.

CONCLUSION

The KIF6 719Arg allele may increase the risk of T2DM and T2DM + CHD only in Han Chinese men by modulating lipid metabolism, especially with regard to TG and HDL.

Pharmacogenomics of lipid-lowering therapies

Statins are the most widely used group of lipid-lowering drugs and they have been shown to be effective in the prevention of cardiovascular disease, primarily by reducing plasma low-density lipoprotein cholesterol concentrations and possibly through other pleiotropic effects. However, there are large variations in lipid responses to statins and some patients have intolerable muscle adverse drug reactions, which may in part be related to genetic factors. In the last decade, pharmacogenetic studies on statins ranging from the candidate gene approach to the more recent genome-wide association studies have provided evidence that genetic variations play an important role in determining statin responses. This review summarizes the current understanding on the pharmacogenomics of statins and other lipid-lowering drugs in current use.

How do we improve patient compliance and adherence to long-term statin therapy?

Statins are highly effective drugs prescribed to millions of people to lower LDL-cholesterol and decrease cardiovascular risk. The benefits of statin therapy seen in randomized clinical trials will only be replicated in real-life if patients adhere to the prescribed treatment regimen. But, about half of patients discontinue statin therapy within the first year, and adherence decreases with time. Patient, physician and healthcare system-related factors play a role in this problem. Recent studies have focused more on the patients' perspectives on non-adherence. Adverse events are cited as the most common cause of statin discontinuation; thus, the healthcare provider must be willing to ally and dialogue with patients to address concerns and assess the risks and benefits of continued statin therapy.

No evidence for cardiac dysfunction in Kif6 mutant mice

A KIF6 variant in man has been reported to be associated with adverse cardiovascular outcomes after myocardial infarction. No clear biological or physiological data exist for Kif6. We sought to investigate the impact of a deleterious KIF6 mutation on cardiac function in mice. Kif6 mutant mice were generated and verified. Cardiac function was assessed by serial echocardiography at baseline, after ageing and after exercise. Lipid levels were also measured. No discernable adverse lipid or cardiac phenotype was detected in Kif6 mutant mice. These data suggest that dysfunction of Kif6 is linked to other more complex biological/biochemical parameters or is unlikely to be of material consequence in cardiac function.

KIF6 719Arg allele is associated with statin effects on cholesterol levels in amnestic mild cognitive impairment and Alzheimer's disease patients

KIF6 719Arg allele carriers are thought to have a greater lipid lowering response from statin therapy than non-carriers. Given the continued interest in the relationship between cholesterol, statin use, amnestic mild cognitive impairment (aMCI), and Alzheimer's disease (AD), investigating the role of KIF6 719Arg carrier status in these relationships may be of importance. Data from 86 patients (36 aMCI, 50 AD) with an average age of 76.87 ± 8.22 years were used for this study. Total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL), and triglycerides were the outcome variables. 719Arg carriers taking statins had significantly lower TC (p < 0.001) and LDL (p < 0.001) levels than 719Arg carriers not taking statins. In addition, 719Arg carriers not taking statins had significantly higher TC (p = 0.004) and LDL (p < 0.001) than 719Arg non-carriers taking statins. Additional analyses indicated that ApoE ε4 carrier status and statin use interaction is also associated with lower TC (p = 0.04), but not LDL (p = 0.06). The interaction between 719Arg and ApoE ε4 carrier status on TC and LDL was not significant. This study is the first to demonstrate an association between lower cholesterol levels and statin use among KIF6 719Arg allele carriers with aMCI and AD. Accounting for 719Arg carrier status may be important in future studies investigating the link between cholesterol and AD and also for AD and aMCI clinical trials using statins as a treatment.

Pharmacogenetics of statins: achievements, whole-genome analyses and future perspectives

Statins are the most commonly prescribed class of drug worldwide and therapy is highly effective in reducing low-density lipoprotein cholesterol levels and cardiovascular events. However, there is large variability in clinical response to statin treatment. Recent research provides evidence that genetic variation contributes to this variable response to statin treatment. Until recently, pharmacogenetic studies have used mainly candidate gene approaches to investigate these effects. Since candidate gene studies explain only a small part of the observed variation and results have often been inconsistent, genome-wide association (GWA) studies may be a better approach. In this paper the most important candidate gene studies and the first published GWA studies assessing statin response are discussed. Moreover, we describe the PHASE study, an EU-funded GWA study that will investigate the genetic variation responsible for the variation in response to pravastatin in a large randomized clinical trial.

Meta-analyses of KIF6 Trp719Arg in coronary heart disease and statin therapeutic effect

Aims

The goal of our study is to assess the contribution of KIF6 Trp719Arg to both the risk of CHD and the efficacy of statin therapy in CHD patients.

Methods and Results

Meta-analysis of 8 prospective studies among 77,400 Caucasians provides evidence that 719Arg increases the risk of CHD (P<0.001, HR = 1.27, 95% CI = 1.15–1.41). However, another meta-analysis of 7 case-control studies among 65,200 individuals fails to find a significant relationship between Trp719Arg and the risk of CHD (P = 0.642, OR = 1.02, 95% CI = 0.95–1.08). This suggests that the contribution of Trp719Arg to CHD varies in different ethnic groups. Additional meta-analysis also shows that statin therapy only benefit the vascular patients carry 719Arg allele (P<0.001, relative ratio (RR) = 0.60, 95% CI = 0.54–0.67). To examine the role of this genetic variant in CHD risk in Han Chinese, we have conducted a case-control study with 289 CHD cases, 193 non-CHD controls, and 329 unrelated healthy volunteers as healthy controls. On post hoc analysis, significant allele frequency difference of 719Arg is observed between female CHD cases and female total controls under the dominant model (P = 0.04, χ² = 4.228, df = 1, odd ratio (OR) = 1.979, 95% confidence interval (CI) = 1.023–3.828). Similar trends are observed for post hoc analysis between female CHD cases and female healthy controls (dominant model: P = 0.04, χ² = 4.231, df = 1, OR = 2.015, 95% CI = 1.024–3.964). Non-genetic CHD risk factors are not controlled in these analyses.

Conclusions

Our meta-analysis demonstrates the role of Trp719Arg of KIF6 gene in the risk of CHD in Caucasians. The meta-analysis also suggests the role of this variant in statin therapeutic response in vascular diseases. Our case-control study suggests that Trp719Arg of KIF6 gene is associated with CHD in female Han Chinese through a post hoc analysis.

Statin pharmacogenomics: opportunities to improve patient outcomes and healthcare costs with genetic testing

HMG-CoA reductase inhibitors, commonly known as statins, are some of the most widely prescribed medications worldwide and have been shown to be effective at lowering cholesterol in numerous long-term prospective trials, yet there are significant limitations to their use. First, patients receiving statin therapy have relatively low levels of medication adherence compared with other drug classes. Next, numerous statin formulations are available, each with its own unique safety and efficacy profile, and it may be unclear to prescribers which treatment is optimal for their patients. Finally, statins have class-wide side effects of myopathy and rhabdomyolysis that have resulted in a product recall and dosage limitations. Recent evidence suggests that two genomic markers, KIF6 and SLCO1B1, may inform the therapy choice of patients initiating statins. Given the prevalence of statin usage, their potential health advantages and their overall cost to the healthcare system, there could be significant clinical benefit from creating personalized treatment regimens. Ultimately, if this approach is effective it may encourage higher adoption of generic statins when appropriate, promote adherence, lower rates of myopathy, and overall achieve higher value cardiovascular care. This paper will review the evidence for personalized prescribing of statins via KIF6 and SLCO1B1 and consider some of the implications for testing these markers as part of routine clinical care.

Association of KIF6 variant with lipid level and angiographic coronary artery disease events risk in the Han Chinese population

KIF6 is a class of molecular motor from the kinesin superfamily. Recently, multiple large studies consisting mainly of Europeans have shown that KIF6 Trp719Arg SNP may be a new predictive factor for coronary artery disease (CAD) event risk. The allelic frequency distribution of rs20455 is different in various populations, yet studies among the Han population, one of the largest ethnic groups in the World, have not been conducted. This study is aimed to evaluate the association of KIF6 Trp719Arg variant with angiographic CAD and serum lipid levels in the Han population from northern China. In this case-controlled study, peripheral blood samples were collected from 356 patients and 568 controls of Han Chinese origin. Genotyping was performed by a high-resolution melting curve. The impact of rs20455 on CAD and non-fatal MI was evaluated in a dominant genetic model with stepwise multiple regression analysis. There were no significant differences of genotypes and allele frequency between angiographic CAD and control groups (p > 0.05); however, that of MI and non-MI subgroups were significant differences (p < 0.05). After adjusting for significant risk factors, angiographic CAD risk was not significantly increased in 719Arg allele carriers compared with non-carriers. Further analysis revealed that the non-fatal MI risk and triglyceride levels were significantly higher in 719Arg allele carriers than non-carriers. In conclusion, KIF6 719Arg allele was not an independent risk factor for angiographic CAD susceptibility in Han populations from northern China. However, it was associated with a significantly higher TG level, which may indicate an increased myocardial infarction risk in angiographic CAD patients.

The evolution and refinement of traditional risk factors for cardiovascular disease

Traditional risk factors for cardiovascular disease such as systemic hypertension and hypercholesterolemia, all described more than half a century ago, are relatively few in number. Efforts to expand the epidemiologic canon have met with limited success because of the high hurdle of causality. Fortunately, another solution to current deficiencies in risk assessment-in particular, the underestimation of risk both before and after initiation of pharmacotherapy-may exist. Parallel to the investigation of novel biomarkers, such as high-sensitivity C-reactive protein, ongoing research has yielded improved metrics of known causative conditions. This evolution of traditional risk factors, heralded by measures such as ambulatory blood pressure, central hemodynamics, low density lipoprotein particle concentration, genetic testing, and "vascular age," may better address the detection gap in cardiovascular disease.

A common KIF6 polymorphism increases vulnerability to low-density lipoprotein cholesterol: two meta-analyses and a meta-regression analysis

Background

We sought to determine if a common polymorphism can influence vulnerability to LDL cholesterol, and thereby influence the clinical benefit derived from therapies that reduce LDL cholesterol.

Methods

We conducted a meta-analysis of the association between a common Trp719Arg polymorphism in the kinesin-like protein 6 (KIF6) gene and the risk of cardiovascular disease (CVD), and a meta-regression analysis to measure the effect modification of this polymorphism on the association between LDL cholesterol and the risk of CVD. We used this measure of genetic effect modification to predict the expected difference in clinical benefit among KIF6 719Arg allele carriers and non-carriers in response to therapies that reduce LDL cholesterol. We then conducted a meta-analysis of statin trials to compare the expected difference in clinical benefit with the observed difference during treatment with a statin.

Results

In a meta-analysis involving 144,931 participants, the KIF6 719Arg allele was not associated with the relative risk (RR) of CVD (RR: 1.02, 95%CI: 0.98–1.07, p = 0.288). Meta-regression analysis involving 88,535 participants, however, showed that the 719Arg allele appears to influence the effect of LDL cholesterol on the risk of CVD. KIF6 carriers experienced a 13% greater reduction in the risk of CVD per mmol/L decrease in LDL cholesterol than non-carriers. We interpreted this difference as the expected difference in clinical benefit among KIF6 carriers and non-carriers in response to therapies that lower LDL cholesterol. The difference in clinical benefit predicted by the increased vulnerability to LDL cholesterol among KIF6 carriers (ratio of RR: 0.87, 95%CI: 0.80–0.94, p = 0.001) agreed very closely with the observed difference among 50,060 KIF6 carriers and non-carriers enrolled in 8 randomized trials of statin therapy (ratio of RR: 0.87, 95%CI: 0.77–0.99, p = 0.038).

Conclusion

The KIF6 719Arg allele increases vulnerability to LDL cholesterol and thereby influences the expected clinical benefit of therapies that reduce LDL cholesterol.

KIF6, LPA, TAS2R50, and VAMP8 genetic variation, low density lipoprotein cholesterol lowering response to pravastatin, and heart disease risk reduction in the elderly

Single nucleotide polymorphisms (SNPs) at the KIF6 (kinesin like protein 6, rs20455 or 719Arg), LPA (lipoprotein(a), rs3798220), TAS2R50 (taste receptor type 2, member 50, rs1376251) and VAMP8 (vesicle-associated membrane protein 8, rs1010) have previously been associated with low density lipoprotein cholesterol (LDL-C) lowering response to statins, coronary heart disease (CHD) at baseline, or CHD events on trial. We examined SNPs at the KIF6 (rs20455 or 719Arg), LPA (rs3798220), TAS2R50 (rs1376251) and VAMP8 (rs1010) in 5,411 participants in PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) (mean age 75.3 years), who had been randomized to pravastatin 40 mg/day or placebo and were followed for a mean of 3.2 years. No SNP was related to vascular disease at baseline. Only the KIF6 SNP was related to LDL-C lowering with homozygous Arg 719 subjects being significantly less responsive than other groups (p=0.025, -34.2 vs. -36.1%). With regard to the primary CHD endpoint on trial (fatal or non-fatal myocardial infarction or stroke), we observed a significant relationship for KIF6 719Arg homozygotes (p=0.03, hazards ratio 0.47, 12.8% of the population) in women on pravastatin only, and for TAS2R50 for the AA genotype (p=0.03, hazards ratio 1.76, 8.9% of the population), also only in women on pravastatin. Our data indicate that the assessment of KIF6 rs20455 and TAS2R50 rs1376251 genotypes are not useful for predicting statin induced cardiovascular risk reduction in men, but do predict CHD risk reduction in women in this elderly population. However, these differences are no longer significant after correction for multiple comparisons, and we do not recommend the assessment of any of these SNPs in clinical practice.

The 719Arg variant of KIF6 and cardiovascular outcomes in statin-treated, stable coronary patients of the treating to new targets and incremental decrease in end points through aggressive lipid-lowering prospective studies

BACKGROUND

Carriers of the KIF6 719Arg variant may be at increased risk for CVD and may benefit more from statin therapy, in terms of CVD risk reduction, than noncarriers. Our objective was to investigate whether carriers of the KIF6 719Arg genetic variant (rs20455) are at increased cardiovascular risk and obtain more benefit from high-dose statin therapy than do noncarriers.

METHODS AND RESULTS

We used an adjusted Cox proportional hazard model to assess the hazard ratio (HR) for the reduction of major cardiovascular events by 80 mg/d atorvastatin over 10 mg/d atorvastatin in 4599 patients of the Treating to New Targets (TNT) study and by 80 mg/d atorvastatin over 20-40 mg/d simvastatin in 6541 patients of the Incremental Decrease in End Points Through Aggressive Lipid-Lowering (IDEAL) study. A total of 381 and 648 patients had a cardiovascular event during follow-up in TNT and IDEAL, respectively. Heterozygotes and homozygotes for the minor allele were not at increased risk compared with noncarriers. In TNT, for noncarriers of the 719Arg allele, the HR for high- versus low-dose atorvastatin was 0.81 (95% confidence interval, 0.59-1.11). In carriers of 1 or 2 minor alleles, the HR was 0.85 (0.66-1.11) and carriers of 2 copies of the minor allele obtained a significant risk reduction (HR: 0.44, 95% confidence interval, 0.23-0.84). In IDEAL, the respective HRs were 0.85 (0.67-1.10), 0.88 (0.62-1.07) and 0.91 (0.58-1.43). The interaction term for carrier status by treatment was also nonsignificant (P=0.810 in TNT and P=0.909 in IDEAL).

CONCLUSIONS

In these 2 large, randomized clinical trials, carriers of the KIF6 719Arg allele were not at increased cardiovascular risk and did not obtain consistent cardiovascular benefit from high-dose statin therapy compared with noncarriers.

Emerging genomic applications in coronary artery disease

Over the last 4 years, an unprecedented number of studies illuminating the genomic underpinnings of common "polygenic" diseases including coronary artery disease have been published. Notably, these studies have established numerous deoxyribonucleic acid (DNA) variants within or near chromosome 9p21.3, the LPA, CXADR, and APOE genes, to name a few, as key coronary artery disease and sudden cardiac death susceptibility markers. Most importantly, many of these DNA variants confer over a 2-fold increase in risk for coronary artery disease, myocardial infarction, and ventricular fibrillation. Additionally, loss-of-function variants in the hepatic cytochrome 2C19 system have now been found to be the predominant genetic mediators of clopidogrel antiplatelet response, with variant carriers having a >3-fold increase in risk for stent thrombosis. In the near future, many additional rare polymorphisms, structural variants, and tissue-specific epigenetic features of the human genome including DNA methylation, histone modifications, and chromatin state will emerge as significant contributors to disease pathogenesis and drug response. In aggregate, these findings will have the potential to radically change the practice of cardiovascular medicine. However, only the individual clinician can ultimately enable the translation of these important discoveries to systematic implementation in clinical practice.

Lack of association between the Trp719Arg polymorphism in kinesin-like protein-6 and cardiovascular risk and efficacy of atorvastatin among subjects with diabetes on dialysis: the 4D study

AIMS

We investigated whether KIF6 Trp719Arg genotypes affect cardiovascular outcomes and efficacy of statin therapy in patients with type 2 diabetes mellitus undergoing hemodialysis.

METHODS AND RESULTS

We conducted a post hoc analysis of the 4D-study, a randomized trial including 1255 patients. Patients were randomly assigned to double-blind treatment with either 20mg of atorvastatin (n = 619) or placebo (n = 636) once daily and followed for 4 years (median). DNA was available for 1232 patients and we assessed KIF6 Trp719Arg genotypes by PCR and subsequent restriction digest. Carriers of the Arg719 allele showed no increased prevalence of cardiovascular disease. The incidence of cardiac death, MI, and stroke did not differ across KIF6 genotypes, irrespective of whether the patients were treated with atorvastatin or not.

CONCLUSION

In patients with type 2 diabetes mellitus on hemodialysis, KIF6 Trp719Arg genotypes were not associated with adverse cardiovascular outcomes during follow-up or with the efficacy of atorvastatin therapy.

Investigation of KIF6 Trp719Arg in a case-control study of coronary artery disease in Western Indians

BACKGROUND

A single-nucleotide polymorphism Trp719Arg (rs20455T>C) in the kinesin-like protein 6 (KIF6), which is a protein involved in intracellular transport, has been shown to predict increased coronary artery disease (CAD) risk and event reduction during statin therapy.

AIM

In the current study, we have evaluated the association of the variant Trp719Arg with CAD/non fatal myocardial infarction (MI) in Western Indians.

METHODS

Genotyping for Trp719Arg was done by an allele-specific real-time assay in 227 cases with confirmed CAD and 150 controls.

RESULTS

We have found that the KIF6 719 Arg carriers were not at a significantly higher risk for CAD/non-fatal MI in this case-control study of an Indo-European population from Western India (Unadjusted odds ratio [OR] 0.767 95% confidence interval [CI] 0.573-1.027 for 719Arg carriers). When the genotypes were further tested to determine association with prevalent myocardial infarction as the event versus CAD, no association was seen in a univariate analysis (MI vs. CAD OR 0.804 95% CI 0.543-1.189; MI vs. Controls OR 0.702 95% CI 0.482-1.021).

CONCLUSION

In summary, carriers of the KIF6 719Arg allele were not at increased risk of CAD/non-fatal MI in a case-control study of Indians (Indo-Europeans) living in Western India.

No impact of KIF6 genotype on vascular risk and statin response among 18,348 randomized patients in the heart protection study

OBJECTIVES

The aim of this study was to test the effects of the KIF6 Trp719Arg polymorphism (rs20455) on vascular risk and response to statin therapy in 18,348 participants from the Heart Protection Study.

BACKGROUND

There have been claims that noncarriers of the KIF6 719Arg variant receive little benefit from statin therapy. Screening for this genetic variant is now being used to influence statin use.

METHODS

Participants received 40 mg simvastatin daily for 4 to 6 weeks before being randomly allocated 40 mg simvastatin daily or placebo for 5 years. Major coronary event was pre-defined as coronary death or nonfatal myocardial infarction, and major vascular event was pre-defined as major coronary event plus revascularization or stroke.

RESULTS

The KIF6 genotype was not significantly associated, among placebo-allocated participants, with the risks of incident major vascular events, major coronary events, revascularizations, or strokes. Overall, 40 mg simvastatin daily produced a 42% reduction in low-density lipoprotein cholesterol, which did not differ significantly by KIF6 719Arg carrier status (p = 0.51). Proportional reductions in the risk of major vascular events with statin therapy were similar (interaction p = 0.70) and highly significant across KIF6 genotypes: 23% (95% confidence interval: 16% to 29%; p = 5.3 × 10⁻¹⁰) in carriers (Arg/Arg or Trp/Arg), and 24% (95% confidence interval: 17% to 31%; p = 4.6 × 10⁻⁹) in noncarriers (Trp/Trp). A similar lack of interaction was observed for major coronary events, revascularizations, and strokes considered separately.

CONCLUSIONS

Statin therapy significantly reduces the incidence of coronary and other major vascular events to a similar extent, irrespective of KIF6 genotype. Consequently, the use of KIF6 genotyping to guide statin therapy is not warranted. (Heart Protection Study; ISRCTN48489393).

Survival bias and drug interaction can attenuate cross-sectional case-control comparisons of genes with health outcomes. An example of the kinesin-like protein 6 (KIF6) Trp719Arg polymorphism and coronary heart disease

BACKGROUND

Case-control studies typically exclude fatal endpoints from the case set, which we hypothesize will substantially underestimate risk if survival is genotype-dependent. The loss of fatal cases is particularly nontrivial for studies of coronary heart disease (CHD) because of significantly reduced survival (34% one-year fatality following a coronary attack). A case in point is the KIF6 Trp719Arg polymorphism (rs20455). Whereas six prospective studies have shown that carriers of the KIF6 Trp719Arg risk allele have 20% to 50% greater CHD risk than non-carriers, several cross-sectional case-control studies failed to show that carrier status is related to CHD. Computer simulations were therefore employed to assess the impact of the loss of fatal events on gene associations in cross-sectional case-control studies, using KIF6 Trp719Arg as an example.

RESULTS

Ten replicates of 1,000,000 observations each were generated reflecting Canadian demographics. Cardiovascular disease (CVD) risks were assigned by the Framingham equation and events distributed among KIF6 Trp719Arg genotypes according to published prospective studies. Logistic regression analysis was used to estimate odds ratios between KIF6 genotypes. Results were examined for 33%, 41.5%, and 50% fatality rates for incident CVD.In the absence of any difference in percent fatalities between genotypes, the odds ratios (carriers vs. noncarriers) were unaffected by survival bias, otherwise the odds ratios were increasingly attenuated as the disparity between fatality rates increased between genotypes. Additional simulations demonstrated that statin usage, shown in four clinical trials to substantially reduce the excess CHD risk in the KIF6 719Arg variant, should also attenuate the KIF6 719Arg odds ratio in case-control studies.

CONCLUSIONS

These computer simulations show that exclusions of prior CHD fatalities attenuate odds ratios of case-control studies in proportion to the difference in the percent fatalities between genotypes. Disproportionate CHD survival for KIF6 Trip719Arg carriers is suggested by their 50% greater risk for recurrent myocardial infarction. This, and the attenuation of KIF6 719Arg carrier risk with statin use, may explain the genotype's weak association with CHD in cross-sectional case-control studies. The results may be relevant to the underestimation of risk in cross-sectional case-control studies of other genetic CHD-risk factors affecting survival.

The contribution of a 9p21.3 variant, a KIF6 variant, and C-reactive protein to predicting risk of myocardial infarction in a prospective study

Background

Genetic risk factors might improve prediction of coronary events. Several variants at chromosome 9p21.3 have been widely reported to be associated with coronary heart disease (CHD) in prospective and case-control studies. A variant of KIF6 (719Arg) has also been reported to be associated with increased risk of CHD in large prospective studies, but not in case-control studies. We asked whether the addition of genetic information (the 9p21.3 or KIF6 variants) or a well-established non-genetic risk factor (C-reactive protein [CRP]) can improve risk prediction by the Framingham Risk Score (FRS) in the Cardiovascular Health Study (CHS)--a prospective observational study of risk factors for cardiovascular disease among > 5,000 participants aged 65 or older.

Methods

Improvement of risk prediction was assessed by change in the area under the receiver-operator characteristic curve (AUC) and by net reclassification improvement (NRI).

Results

Among white participants the FRS was improved by addition of KIF6 719Arg carrier status among men as assessed by the AUC (from 0.581 to 0.596, P = 0.03) but not by NRI (NRI = 0.027, P = 0.32). Adding both CRP and 719Arg carrier status to the FRS improved risk prediction by the AUC (0.608, P = 0.02) and NRI (0.093, P = 0.008) in men, but not women (P ≥ 0.24).

Conclusions

While none of these risk markers individually or in combination improved risk prediction among women, a combination of KIF6 719Arg carrier status and CRP levels modestly improved risk prediction among white men; although this improvement is not significant after multiple-testing correction. These observations should be investigated in other prospective studies.

Exon 11 deletion in the myocyte enhancer factor (MEF)2A and early onset coronary artery disease gene in a Sicilian family

AIMS

We investigated the prevalence of the myocyte enhancer factor (MEF)2A exon 11 deletion, a putative coronary artery disease (CAD) susceptibility gene, in patients referred for coronary angiography.

METHODS AND RESULTS

In total, 1079 consecutive patients referred for coronary angiography in the GENICA Study were genotyped and 301 low-risk subjects were used as controls. One patient with early onset three vessels CAD, carrying the MEF2A deletion was found in the GENICA Study cohort and none in the control group.

CONCLUSION

In a cohort of patients undergoing coronary angiography for suspected CAD the MEF2A exon 11 deletion occurred in 0.09%.

Genetic variants of connexin37 are associated with carotid intima-medial thickness and future onset of ischemic stroke

BACKGROUND

Carotid intima-medial thickness (IMT) is a surrogate marker of subclinical atherosclerosis. This study aimed to investigate the impacts of genetic variants on IMT and future development of ischemic stroke in a cohort, followed by an independent replication study.

METHODS

B-mode carotid ultrasound was performed among 3330 healthy adults in the CVDFACT cohort study, and the genetic effects of atherosclerosis-related genes including connexin37 (GJA4), C-reactive protein (CRP), paraoxonase (PON1), adiponectin (ACDC), angiotensin-converting enzyme (ACE), beta-adrenergic receptor (ADRB1, ADRB2), antithrombin III (SERPINC1), and kinesin family member 6 (KIF6) were evaluated by a multivariate regression model, adjusting for traditional vascular risk factors. Study subjects were prospectively followed for the development of ischemic stroke to assess the prognostic impacts of these genetic variants. An independent case-control study was performed to replicate the genetic association from the cohort study.

RESULTS

The T allele of connexin37 C1019T polymorphism significantly affected IMT (β=0.014, p=0.013) after adjusting for traditional risk factors. During an average follow-up period of 10.7 years, 80 patients with ischemic stroke (2.4%) were identified. The connexin37 1019T allele was significantly associated with an increased rate of ischemic stroke under an additive model, with hazard ratios (HR) of 2.83 (95% confidence interval, 1.2-6.66) and 1.69 (95% confidence interval, 1.06-2.71), comparing TT and CT genotype with CC, respectively. After Cox analysis, age (HR, 1.78 every 10 years), diabetes mellitus (HR, 2.63), hypertension (HR, 2.08), and the T allele of C1019T polymorphism of GJA4 (HR, 1.69) were identified as independent predictors of ischemic stroke. The relationship between T allele of C1019T polymorphism of GJA4 gene and ischemic stroke was also confirmed by an independent association study.

CONCLUSION

Connexin 37 genetic variants significantly affect carotid IMT and contribute to future development of ischemic stroke.

Family coronary heart disease: a call to action

A family history of coronary heart disease (CHD) is an accepted risk factor for cardiovascular events and is independent of common CHD risk factors. Advances in the understanding of genetic influences on CHD risk provide the opportunity to apply this knowledge and improve patient care. Utility of inherited cardiovascular risk testing exists by utilizing both phenotypes and genotypes and includes improved CHD risk prediction, selection of the most appropriate treatment, prediction of outcome, and family counseling. The major impediment to widespread clinical adoption of this concept involves un-reimbursed staff time, educational needs, access to a standardized and efficient assessment mechanism, and privacy issues. The link between CHD and inheritance is indisputable and the evidence strong and consistent. For clinicians, the question is how to utilize this information, in an efficient manner, in order to improve patient care and detection of high-risk family members.

KIF6 Trp719Arg polymorphism and the effect of statin therapy in elderly patients: results from the PROSPER study

BACKGROUND

Statin therapy has been found to substantially and significantly reduce coronary events in carriers of the KIF6 719Arg variant (rs20455) but not in noncarriers. We investigated whether, among the elderly, statin therapy also significantly reduced coronary events in carriers but not in noncarriers.

DESIGN AND METHODS

Among 5,752 patients of the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) study, we assessed the effect of pravastatin, compared with placebo, on coronary events according to 719Arg carrier status using proportional hazards models.

RESULTS

Since benefit from statin therapy in elderly patients has been primarily shown among those with prior vascular disease, we performed analyses in PROSPER patients with prior disease and found that pravastatin therapy significantly reduced events in 719Arg carriers [hazards ratio (HR): 0.66, 95% confidence interval (CI): 0.52-0.86] but not in noncarriers (HR: 0.94, 95% CI: 0.69-1.28), P=0.09 for interaction between treatment and carrier status. Among those without prior disease, no significant benefit was observed in either carriers or noncarriers. Among those with prior vascular disease in the placebo arm, Trp719Arg heterozygotes were at significantly greater risk, compared with noncarriers (HR: 1.36, 95% CI: 1.03-1.81, P=0.03); the HR of 719Arg carriers, compared with noncarriers, was 1.28 (95% CI: 0.98-1.69, P=0.07).

CONCLUSION

Elderly carriers of the KIF6 719Arg variant with prior vascular disease received significant benefit from pravastatin therapy; no benefit was observed in noncarriers with prior disease or in those without prior disease (carriers or noncarriers).

Lack of association between the Trp719Arg polymorphism in kinesin-like protein-6 and coronary artery disease in 19 case-control studies

OBJECTIVES

We sought to replicate the association between the kinesin-like protein 6 (KIF6) Trp719Arg polymorphism (rs20455), and clinical coronary artery disease (CAD).

BACKGROUND

Recent prospective studies suggest that carriers of the 719Arg allele in KIF6 are at increased risk of clinical CAD compared with noncarriers.

METHODS

The KIF6 Trp719Arg polymorphism (rs20455) was genotyped in 19 case-control studies of nonfatal CAD either as part of a genome-wide association study or in a formal attempt to replicate the initial positive reports.

RESULTS

A total of 17,000 cases and 39,369 controls of European descent as well as a modest number of South Asians, African Americans, Hispanics, East Asians, and admixed cases and controls were successfully genotyped. None of the 19 studies demonstrated an increased risk of CAD in carriers of the 719Arg allele compared with noncarriers. Regression analyses and fixed-effects meta-analyses ruled out with high degree of confidence an increase of ≥2% in the risk of CAD among European 719Arg carriers. We also observed no increase in the risk of CAD among 719Arg carriers in the subset of Europeans with early-onset disease (younger than 50 years of age for men and younger than 60 years of age for women) compared with similarly aged controls as well as all non-European subgroups.

CONCLUSIONS

The KIF6 Trp719Arg polymorphism was not associated with the risk of clinical CAD in this large replication study.

KIF6 p.Trp719Arg Testing to Assess Risk of Coronary Artery Disease and/or Statin Response

Coronary artery disease (CAD) is a leading cause of death worldwide and in the United States it is responsible for more than 500,000 deaths each year. Genome-wide association studies (GWAS) have revealed connections between a number of common single nucleotide polymorphisms (SNPs) and CAD and other cardiovascular diseases. The p.Trp719Arg SNP in the kinesin-like family 6 (KIF6) gene has recently been reported as a potential risk factor for CAD as well as a predictor of response to statin therapy.

KIF6 polymorphism as a predictor of risk of coronary events and of clinical event reduction by statin therapy

Evidence from multiple large prospective studies suggests that a common polymorphism that encodes an arginine (Arg)-to-tryptophan substitution at position 719 in the KIF6 gene is associated with coronary heart disease (CHD) and reduction in coronary events from statin therapy. Carriers of the 719Arg allele were at greater risk for primary and secondary CHD events, and statin therapy significantly reduced coronary events in 719Arg carriers but not in noncarriers. The number needed to treat to prevent a single CHD event ranged from 10 to 20 for 719Arg carriers, compared to >80 for noncarriers in the Cholesterol and Recurrent Events (CARE) study, the West of Scotland Coronary Prevention Study (WOSCOPS), the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER), and the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis In Myocardial Infarction 22 (PROVE IT-TIMI22) study. In conclusion, assessment of 719Arg carrier status holds promise for stratification of coronary event risk and for selection of optimal therapy in primary and secondary CHD prevention.

Genetic variants in the KIF6 region and coronary event reduction from statin therapy

A single nucleotide polymorphism (SNP) in KIF6, a member of the KIF9 family of kinesins, is associated with differential coronary event reduction from statin therapy in four randomized controlled trials; this SNP (rs20455) is also associated with the risk for coronary heart disease (CHD) in multiple prospective studies. We investigated whether other common SNPs in the KIF6 region were associated with event reduction from statin therapy. Of the 170 SNPs in the KIF6 region investigated in the Cholesterol and Recurrent Events trial (CARE), 28 were associated with differential event reduction from statin therapy (P_interaction < 0.1 in Caucasians, adjusted for age and sex) and were further investigated in the Pravastatin or Atorvastatin Evaluation and Infection Therapy-Thrombolysis In Myocardial Infarction 22 (PROVE IT-TIMI22) and West of Scotland Coronary Prevention Study (WOSCOPS). These analyses revealed that two SNPs (rs9462535 and rs9471077), in addition to rs20455, were associated with event reduction from statin therapy (P_interaction < 0.1 in each of the three studies). The relative risk reduction ranged from 37 to 50% (P < 0.01) in carriers of the minor alleles of these SNPs and from −4 to 13% (P > 0.4) in non-carriers. These three SNPs are in high linkage disequilibrium with one another (r² > 0.84). Functional studies of these variants may help to understand the role of KIF6 in the pathogenesis of CHD and differential response to statin therapy.

Investigation of KIF6 Trp719Arg in a case-control study of myocardial infarction: a Costa Rican population

Background and Methodology

The 719Arg allele of KIF6 (rs20455) was associated with coronary events in Caucasian participants of five prospective studies. We investigated whether this KIF6 variant was associated with non-fatal myocardial infarction (MI) in a case-control study of an admixed population from the Central Valley of Costa Rica. Genotypes of the KIF6 variant were determined for 4,134 men and women. Cases (1,987) had survived a first MI; controls (2,147) had no history of MI and were matched to cases by age, sex, and area of residence. We tested the association between the KIF6 719Arg allele and non-fatal MI by conditional logistic regression and adjusted for admixture of founder populations.

Principal Findings

Compared with the reference Trp/Trp homozygotes, KIF6 719Arg carriers were not at significantly higher risk for non-fatal MI in this study after adjustment for traditional risk factors or admixture (OR = 1.12; 95%CI, 0.98–1.28). Heterozygotes of the KIF6 Trp719Arg variant were at increased risk of non-fatal MI: the adjusted odds ratio was 1.16 (95% confidence interval, 1.01–1.34), but this association would not be significant after a multiple testing correction.

Conclusions/Significance

We found that carriers of the KIF6 719Arg allele were not at increased risk of non-fatal MI in a case-control study of Costa Ricans living in the Central Valley of Costa Rica.

Metabolomics and atherosclerosis

Metabolites reflect the dynamic processes underlying cellular homeostasis. Recent advances in analytical chemistry and molecular biology have set the stage for metabolite profiling to help us understand complex molecular processes and physiology. Metabolomics is the comparative analysis of metabolite flux and how it relates to biological phenotypes. As an intermediate phenotype, metabolite signatures capture a unique aspect of cellular dynamics that is not typically interrogated, providing a distinct perspective on cellular homeostasis. To date, there have been only a few metabolomics studies investigating cardiovascular diseases. In this review, we explore the principles of metabolomics and how it can provide further insight into the mechanisms of cardiovascular physiology and ultimately lead to improved diagnostic and therapeutic options for patients with cardiovascular disease.

Emerging clinical applications in cardiovascular pharmacogenomics

Over one-fourth of the 36 million annual outpatient prescriptions filled in the United States are known to have human genomic biomarker information available that predicts drug safety and efficacy, or both. However, to date, we have not systematically implemented strategies to effectively use this data in clinical practice to improve patient outcomes. Part of the difficulty has stemmed from the only modest predictive capacity of previously identified gene variants, lack of replication of data in multiple studies, and the hesitancy of the clinical community to translate data gleaned from basic and translational research to routine clinical practice. Now, additional key variants that strongly impact drug absorption, metabolism, and excretion are rapidly surfacing through the use of genome-wide association technology. Most importantly, these variants are being validated in independent cohorts of thousands of cases and controls. In the near future, the dramatic reduction in the cost of DNA sequencing will lead to further insight into the common and rare genetic variants that strongly predict our individual response to commonly used medications. The clinical community will need to be prepared to utilize this vital data in aiding their selection of the right drug for the right patient if we expect to significantly reduce the ever increasing burden of societies' most common diseases. Herein, we detail the most clinically compelling and robust examples of pharmacogenomics emerging in the field of cardiovascular disease and hopefully foretell how cardiovascular disease might be treated in the era of genomic medicine.