Genetic risk score of cerebral infarction in atrial fibrillation genome-wide association study.

INTRODUCTION: Stroke is a leading cause of death and the primary cause of adult-acquired disability. Patients with cardiogenic embolic stroke also have higher mortality and recurrence rates than patients with other stroke subtypes. Atrial fibrillation (AF) is a major risk factor for cerebral infarction (CI). The large-scale study identified 32 loci in the MEGASTROKE study. However, few studies have attempted to identify novel stroke risk variants in patients with a history of AF. Our overall aim was to identify novel CI risk variants in AF cases and explore whether their associations with the CI risk were affected by the CHADS2 and CHA2DS2-VASc scores. METHODS: We performed association study with CI using 8181 AF cases in previous genome-wide association study (GWAS) and imputation data without controls. We classified AF cases into those with or without past history of CI, and the genetic associations with the CI risk were examined. RESULTS: GWAS identified eight associated loci. The generated genetic risk score (GRS) for the eight loci was significantly associated with CI in patients with AF (1.46 × 10-8 ). We estimated bivariate logistic regression model which contained GRS and CHADS2 score (GRS: p-Value = 7.41 × 10-9 , CHADS2 score: p-Value <2.0 × 10-16 ) or CHA2DS2-VASc scores (GRS: p-Value = 2.52 × 10-10 , CHA2DS2-VASc score: p-Value <2.0 × 10-16 ). CONCLUSION: We identified eight genetic variants that were potentially associated with the risk of CI of AF cases and the significant GRS, whose associations were independent of the CHADS2 or CHA2DS2-VASc score.

Ethnic similarities in genetic polymorphisms associated with atrial fibrillation: Far East Asian vs European populations.

BACKGROUND: In European ancestry, 111 genetic loci were identified as associated with atrial fibrillation (AF). We explored the reproducibility of those single nucleotide polymorphisms (SNPs) in a genome-wide association study (GWAS) meta-analysis of Far East Asian populations. METHODS: We performed a meta-analysis of the Korean AF network and Japanese AF data sets (9118 cases and 33 467 controls) by an inverse-variance fixed-effects model. We compared the results with 111 previously reported SNPs proven in Europeans after excluding 36 missing loci and a locus with a minor allelic frequency (MAF) < 0.01 in the European population. RESULTS: Among remaining 74 loci, 29 loci were replicated at a P < .05, and 17 of those loci were newly found in the Far East Asian population: 3 loci with a P < 5×10-8 (METTL11B at 1q24, KCNN2 at 5q22 and LRMDA at 10q22), 4 loci at the threshold of the Bonferroni correction of P = 4.5 × 10-4  ~ 5×10-8 (KIF3C at 2p23, REEP3, NRBF2 at 10q21, SIRT1, MYPN at 10q21 and CFL2 at 14q13) and 10 SNPs with a P = .05 ~ 4.5 × 10-4 . Among 18 AF loci with a MAF< 0.01 in the Far East Asian populations, 2 loci (GATA4 at 8q23 and SGCG at 13q12) were replicated after a fine mapping. Twenty-seven AF loci, including a locus, which had a sufficient sample size to get a power of over 80% (with a type 1 error α = 4.5 × 10-4 ), were not replicated in the Far East Asian populations. CONCLUSIONS: We newly replicated 19 AF-associated genetic loci in the European descent among the Far East Asian populations. It highlights the extensive sharing of AF genetic risks across Far East Asian populations.

Mutant KCNJ3 and KCNJ5 Potassium Channels as Novel Molecular Targets in Bradyarrhythmias and Atrial Fibrillation.

BACKGROUND: Bradyarrhythmia is a common clinical manifestation. Although the majority of cases are acquired, genetic analysis of families with bradyarrhythmia has identified a growing number of causative gene mutations. Because the only ultimate treatment for symptomatic bradyarrhythmia has been invasive surgical implantation of a pacemaker, the discovery of novel therapeutic molecular targets is necessary to improve prognosis and quality of life. METHODS: We investigated a family containing 7 individuals with autosomal dominant bradyarrhythmias of sinus node dysfunction, atrial fibrillation with slow ventricular response, and atrioventricular block. To identify the causative mutation, we conducted the family-based whole exome sequencing and genome-wide linkage analysis. We characterized the mutation-related mechanisms based on the pathophysiology in vitro. After generating a transgenic animal model to confirm the human phenotypes of bradyarrhythmia, we also evaluated the efficacy of a newly identified molecular-targeted compound to upregulate heart rate in bradyarrhythmias by using the animal model. RESULTS: We identified one heterozygous mutation, KCNJ3 c.247A>C, p.N83H, as a novel cause of hereditary bradyarrhythmias in this family. KCNJ3 encodes the inwardly rectifying potassium channel Kir3.1, which combines with Kir3.4 (encoded by KCNJ5) to form the acetylcholine-activated potassium channel ( IKACh channel) with specific expression in the atrium. An additional study using a genome cohort of 2185 patients with sporadic atrial fibrillation revealed another 5 rare mutations in KCNJ3 and KCNJ5, suggesting the relevance of both genes to these arrhythmias. Cellular electrophysiological studies revealed that the KCNJ3 p.N83H mutation caused a gain of IKACh channel function by increasing the basal current, even in the absence of m2 muscarinic receptor stimulation. We generated transgenic zebrafish expressing mutant human KCNJ3 in the atrium specifically. It is interesting to note that the selective IKACh channel blocker NIP-151 repressed the increased current and improved bradyarrhythmia phenotypes in the mutant zebrafish. CONCLUSIONS: The IKACh channel is associated with the pathophysiology of bradyarrhythmia and atrial fibrillation, and the mutant IKACh channel ( KCNJ3 p.N83H) can be effectively inhibited by NIP-151, a selective IKACh channel blocker. Thus, the IKACh channel might be considered to be a suitable pharmacological target for patients who have bradyarrhythmia with a gain-of-function mutation in the IKACh channel.

Functional Role of the L396R Mutation of Tks5 Identified by an Exome-Wide Association Study in Atrial Fibrillation.

BACKGROUND: Atrial fibrillation (AF) is the most common cardiac arrhythmia; however, the current treatment strategies for AF have limited efficacy. Thus, a better understanding of the mechanisms underlying AF is important for future therapeutic strategy. A previous study (Exome-Wide Association Study (ExWAS)) identified a rare variant, rs202011870 (MAF=0.00036, GenomAD), which is highly associated with AF (OR=3.617, P<0.0001). rs202011870 results in the replacement of Leu at 396 with Arg (L396R) in a molecule, Tks5; however, the mechanism of how rs202011870 links to AF is completely unknown.Methods and Results:The association of rs202011870 with AF was examined in 3,378 participants (641 control and 2,737 AF cases) from 4 independent cohorts by using an Invader assay. Consequences of rs202011870 in migration ability, podosome formation, and expression of inflammation-related molecules in macrophages were examined using RAW264.7 cells with a trans-well assay, immunocytochemistry, and qPCR assay. Validation of the association of rs202011870 with AF was successful. In vitro studies showed that RAW264.7 cells with L396R-Tks5 increased trans-well migration ability, and enhanced podosome formation. RAW264.7 cells with L396R-Tks5 also increased the expression of several inflammatory cytokines and inflammation-related molecules. CONCLUSIONS: L396R mutation in Tks5 associated with AF enhances migration of macrophages and their inflammatory features, resulting in enhanced susceptibility to AF.

Association of the Clinical and Genetic Factors With Superior Vena Cava Arrhythmogenicity in Atrial Fibrillation.

BACKGROUND: Atrial fibrillation (AF) can be initiated from arrhythmogenic foci within the muscular sleeves that extend not only into the pulmonary veins but also into both vena cavae. The superior vena cava (SVC) is a key target site for catheter ablation. Patients with SVC-derived AF often lack the clinical risk factors of AF.Methods and Results:We conducted a meta-analysis of the clinical and genetic factors of 2,170 AF patients with and without SVC arrhythmogenicity. In agreement with previous reports, the left atrial diameter was smaller in AF patients with SVC arrhythmogenicity. Among 6 variants identified in a previous genome-wide association study in Japanese patients, rs2634073 and rs6584555 were associated with SVC arrhythmogenicity. This finding was confirmed in our meta-analysis using independent cohorts. We also found that SVC arrhythmogenicity was conditionally dependent on age, body mass index, and left ventricular ejection fraction. CONCLUSIONS: Both clinical and genetic factors are associated with SVC arrhythmogenicity.

Two susceptibility loci to Takayasu arteritis reveal a synergistic role of the IL12B and HLA-B regions in a Japanese population.

Takayasu arteritis (TAK) is an autoimmune systemic vasculitis of unknown etiology. Although previous studies have revealed that HLA-B*52:01 has an effect on TAK susceptibility, no other genetic determinants have been established so far. Here, we performed genome scanning of 167 TAK cases and 663 healthy controls via Illumina Infinium Human Exome BeadChip arrays, followed by a replication study consisting of 212 TAK cases and 1,322 controls. As a result, we found that the IL12B region on chromosome 5 (rs6871626, overall p = 1.7 × 10(-13), OR = 1.75, 95% CI 1.42-2.16) and the MLX region on chromosome 17 (rs665268, overall p = 5.2 × 10(-7), OR = 1.50, 95% CI 1.28-1.76) as well as the HLA-B region (rs9263739, a proxy of HLA-B*52:01, overall p = 2.8 × 10(-21), OR = 2.44, 95% CI 2.03-2.93) exhibited significant associations. A significant synergistic effect of rs6871626 and rs9263739 was found with a relative excess risk of 3.45, attributable proportion of 0.58, and synergy index of 3.24 (p ≤ 0.00028) in addition to a suggestive synergistic effect between rs665268 and rs926379 (p ≤ 0.027). We also found that rs6871626 showed a significant association with clinical manifestations of TAK, including increased risk and severity of aortic regurgitation, a representative severe complication of TAK. Detection of these susceptibility loci will provide new insights to the basic mechanisms of TAK pathogenesis. Our findings indicate that IL12B plays a fundamental role on the pathophysiology of TAK in combination with HLA-B(∗)52:01 and that common autoimmune mechanisms underlie the pathology of TAK and other autoimmune disorders such as psoriasis and inflammatory bowel diseases in which IL12B is involved as a genetic predisposing factor.

Integrating genetic, transcriptional, and functional analyses to identify 5 novel genes for atrial fibrillation.

BACKGROUND: Atrial fibrillation (AF) affects >30 million individuals worldwide and is associated with an increased risk of stroke, heart failure, and death. AF is highly heritable, yet the genetic basis for the arrhythmia remains incompletely understood. METHODS AND RESULTS: To identify new AF-related genes, we used a multifaceted approach, combining large-scale genotyping in 2 ethnically distinct populations, cis-eQTL (expression quantitative trait loci) mapping, and functional validation. Four novel loci were identified in individuals of European descent near the genes NEURL (rs12415501; relative risk [RR]=1.18; 95% confidence interval [CI], 1.13-1.23; P=6.5×10(-16)), GJA1 (rs13216675; RR=1.10; 95% CI, 1.06-1.14; P=2.2×10(-8)), TBX5 (rs10507248; RR=1.12; 95% CI, 1.08-1.16; P=5.7×10(-11)), and CAND2 (rs4642101; RR=1.10; 95% CI, 1.06-1.14; P=9.8×10(-9)). In Japanese, novel loci were identified near NEURL (rs6584555; RR=1.32; 95% CI, 1.26-1.39; P=2.0×10(-25)) and CUX2 (rs6490029; RR=1.12; 95% CI, 1.08-1.16; P=3.9×10(-9)). The top single-nucleotide polymorphisms or their proxies were identified as cis-eQTLs for the genes CAND2 (P=2.6×10(-19)), GJA1 (P=2.66×10(-6)), and TBX5 (P=1.36×10(-5)). Knockdown of the zebrafish orthologs of NEURL and CAND2 resulted in prolongation of the atrial action potential duration (17% and 45%, respectively). CONCLUSIONS: We have identified 5 novel loci for AF. Our results expand the diversity of genetic pathways implicated in AF and provide novel molecular targets for future biological and pharmacological investigation.

New human leukocyte antigen risk allele in Japanese patients with Takayasu arteritis.

BACKGROUND: The association of human leukocyte antigen (HLA) alleles and Takayasu arteritis (TA) is not fully understood. The aim of the present study was to investigate HLA alleles in Japanese patients with TA and the association of these alleles with clinical manifestations. METHODS AND RESULTS: A total of 96 patients diagnosed with TA according to the Guideline for Management of Vasculitis Syndrome (Japanese Circulation Society 2008) and 371 healthy controls were enrolled in the present study. HLA genotyping showed a significant association of HLA-B67 (P=0.00024, odds ratio [OR]=4.94), a novel locus, and B52 (P<0.0001; OR=3.35), a conventional locus, with TA using both sequence-based typing and PCR-SSP assay. The frequency of HLA-B39, an allele reportedly associated with TA in Asian populations, was not higher than controls in the present study (P=0.86, OR=1.07). B52 had higher prevalence than B67 but the OR was higher for B67. We next studied the association of HLA-B67 and -B52 with clinical characteristics: age at disease onset, distribution of arteritis, pulmonary involvement, aortic regurgitation, systemic hypertension, steroid resistance and recurrence rate in TA. There was no significant difference in these clinical parameters between HLA-B67-positive or HLA-B52-positive patients and other patients. CONCLUSIONS: The HLA-B67 allele could be a new and important marker of TA because of its high OR compared to HLA-B52, although its prevalence in TA is lower.

Establishment of the Certified Research Ethics Professionals: An Ethical Review Expert -Translated in English from Japanese Version.

Medical research is indispensable to develop new treatments or diagnostic methods. An ethics review board reviews the validity of such medical research. However, with the recent advances in medicine, a meaningful review of medical research often requires advanced knowledge. There is thus a growing necessity for a professional who can support ethical review. Therefore, a new system called the Certified Research Ethics Committee Professional (CReP), an Ethical Review Expert, has been established.

Networking analysis on superior vena cava arrhythmogenicity in atrial fibrillation.

Atrial fibrillation (AF) can be initiated from arrhythmogenic foci within the muscular sleeves that extend not only into the pulmonary veins but also into both vena cavae. Patients with SVC-derived AF have the common clinical and genetic risk factors. Bayesian network analysis is a probabilistic model in which a qualitative dependency relationship among random variables is represented by a graph structure and a quantitative relationship between individual variables is expressed by a conditional probability. We used data of meta-analysis of 2170 AF patients with and without SVC arrhythmogenicity in the previous article. Bayesian Networking analysis was performed using the software "bnlearn". Using the clinical and genetic factors associated with SVC arrhythmogenicity in the previous article, we investigated a Bayesian networking structure to determine the probabilitic causation of variants to clinical parameters and found that the rate of recurrence depended on SVC arrhythmogenicity and LA diameter, and that SVC arrhythmogenicity was conditionally dependent on gender, body mass index, and genetic risk score. We found the possibility of prediction model generated from three factors. Receiver-operation characteristic analysis showed the area under the curve was 0.84. Using the clinical/genetic factors associated with SVC arrhythmogenicity through the previous meta-analysis of over 2000 patients, Bayesian networking analysis indicated the probabilistic causation of SVC arrhythmogenicity and associated clinical/genetic factors.

Pathway analysis with genome-wide association study (GWAS) data detected the association of atrial fibrillation with the mTOR signaling pathway.

BACKGROUND: Genome-wide association studies (GWAS) have identified numerous loci associated with diseases and traits. However, the elucidation of disease mechanisms followed by drug development has remained a challenge owing to complex gene interactions. We performed pathway analysis with MAGENTA (Meta-Analysis Geneset Enrichment of variaNT Associations) to clarify the pathways in genetic background of AF. METHODS: The existing GWAS data were analyzed using MAGENTA. A microarray analysis was then performed for the identified pathways with human atrial tissues, followed by Gene-Set Enrichment Analysis (GSEA). RESULTS: MAGENTA identified two novel candidate pathways for AF pathogenesis, the CTCF (CCCTC-binding factor, p = 1.00 × 10-4, FDR q = 1.64 × 10-2) and mTOR pathways (mammalian target of rapamycin, p = 3.00 × 10-4, FDR q = 3.13 × 10-2). The microarray analysis with human atrial tissue using the GSEA indicated that the mTOR pathway was suppressed in AF cases compared with non-AF cases, validating the MAGENTA results, but not CTCF pathway. CONCLUSIONS: MAGENTA identified a novel pathway, mTOR, followed by GSEA with human atrial tissue samples. mTOR pathway is a key interface that adapts the change of environments by pressure overload and metabolic perturbation. Our results indicate that the MTOR pathway is involved in the pathogenesis of AF, although the details of the basic mechanism remain unknown and further analysis for causal-relationship of mTOR pathway to AF is required. CTCF pathway is essential for construction of chromatin structure and transcriptional process. The gene-set components of CTCF overlap with those of mTOR in Biocarta.

Effects of immunosuppressive and biological agents on refractory Takayasu arteritis patients unresponsive to glucocorticoid treatment.

BACKGROUND: We aimed to investigate the effects of immunosuppressive and biological agents on refractory Takayasu arteritis (TA) patients resistant to or dependent on glucocorticoids. METHODS: Forty-four consecutive TA patients were enrolled, and the clinical characteristics and effectiveness of the immunosuppressive and biological agents in achieving and maintaining remission among glucocorticoid-resistant or glucocorticoid-dependent patients were investigated. RESULTS: Fifteen patients showed favorable response to the initial glucocorticoid treatment, and 29 patients exhibited resistance to initial glucocorticoid treatment or relapsed with tapering glucocorticoid. Of the 29 patients, 5 responded to additional glucocorticoid treatment, and 22 of the remaining 24 glucocorticoid-resistant or glucocorticoid-dependent patients were prescribed immunosuppressive agents. Methotrexate was the most commonly used in these patients as the first-line treatment. In total, 10 patients maintained remission using immunosuppressive agents, with the effectiveness of each agent about 20%. The only significant difference between patients who were and were not able to achieve and maintain remission with immunosuppressive agents was the presence of the HLA-B52 allele (p<0.0001). Biological agents were administered to 6 patients refractory to immunosuppressive agents. All patients were administered tumor necrosis factor (TNF) inhibitors as the first-line treatment, and 3 patients maintained remission. Anti-interleukin-6 receptor antibody was administered to 2 patients who were resistant to the TNF inhibitors, and 1 patient achieved and maintained remission. CONCLUSION: In our cohort, 64% of the glucocorticoid-resistant or glucocorticoid-dependent patients maintained remission through a combined treatment with glucocorticoid, immunosuppressive agents, and/or biological agents. The combined use of immunosuppressive and biological agents appears to be a promising treatment option for achieving and maintaining remission in refractory TA patients.

Clinical utility and functional analysis of variants in atrial fibrillation-associated locus 4q25.

BACKGROUND: Chromosome 4q25 has been repeatedly identified as atrial fibrillation (AF)-sensitive locus in multiple genome-wide association studies (GWAS) and is considered to hold some clues to AF pathogenesis. We aimed to investigate the clinical utilities in Japanese and to unveil the function of the 4q25 locus in affecting transcription of adjacent genes. METHODS: We conducted AF GWAS in Japanese population (1382 AF cases and 1478 controls) and the replication panel (1666 AF cases and 1229 controls) with detailed clinical information which showed the acceleration of AF onset. Stepwise investigations with linkage disequilibrium analysis, histone code patterns, and reporter assay in the 4q25 locus were performed. RESULTS: The AF GWAS confirmed a significant association of rs4611994 and rs1906617 in chromosome 4q25 with AF. In the clinical analysis, AF onset of the individuals with risk allele accelerated 2.5 years compared with those with protective allele (p=0.00012). Next, in the functional analysis, three single nucleotide polymorphisms (SNPs) in the variant group selected by linkage disequilibrium analysis were identified as candidates for the cis-regulatory element toward adjacent genes in chromatin immunoprecipitation assay. Among them, rs4611994 and rs72900144 regions showed higher effects on the transcriptional activity of luciferase gene in the risk alleles than those in the protective alleles (p<0.0001, p<0.005, respectively). CONCLUSIONS: AF GWAS in Japanese confirmed the association with 4q25 locus and indicated that its SNP affected the acceleration of AF onset. The candidate regions of the causative SNPs, rs4611994 and rs72900144, could alter the adjacent gene expression level.

Chromosome 4q25 variants and recurrence after second-generation cryoballoon ablation in patients with paroxysmal atrial fibrillation.

BACKGROUND: Chromosome 4q25 single-nucleotide polymorphisms (SNPs) are associated with atrial fibrillation (AF) recurrence after radiofrequency catheter ablation, however the underlying mechanism is unknown. Pulmonary vein (PV) reconnections are common post-radiofrequency ablation. We explored the pre-procedural parameters, including AF susceptibility SNPs, predicting the response to PV isolation (PVI) using second-generation cryoballoons. METHODS: One hundred fifty-seven paroxysmal AF patients undergoing PVI using second-generation cryoballoons and genetic testing were enrolled. The top 6 AF-associated Japanese ancestry SNPs were evaluated. Fourteen-day consecutive monitoring was performed to detect AF recurrences. RESULTS: Early recurrence of AF (ERAF) was detected in 74(47.1%) patients, and the AF-free survival at 12-months after single procedures was 72.1%. Cox's proportional models determined that higher pro-BNP values (hazard ratio [HR]=1.001; 95% confidence interval [CI]=1.000-1.001; p=0.003) and the rs1906617 risk allele (HR=2.440; 95% CI=1.062-5.605; p=0.035) were independently associated with ERAFs, and the rs1906617 risk allele (HR=4.339; 95% CI=1.044-18.028; p=0.043) was the sole factor significantly associated with AF recurrence. Second procedures were performed in 41 patients a median of 6.0[5.0-9.5] months later, and 42/162(25.9%) PVs were reconnected. Reconnections were similarly observed in rs1906617 risk allele carriers and wild-type patients. Risk allele carriers at rs1906617 were more likely to have non-PV foci, but did not reach statistical significance (10/35 vs. 0/6, p=0.132). CONCLUSIONS: AF risk alleles on chromosome 4q25 modulated the risk of AF recurrence after PVI using second-generation cryoballoons in patients with paroxysmal AF. Our study results suggested that non-PV foci might be the more likely mechanism of a high AF recurrence in chromosome 4q25 variant carriers.

Genetic Variants Associated With Susceptibility to Atrial Fibrillation in a Japanese Population.

BACKGROUND: Atrial fibrillation (AF) affects millions of individuals worldwide. The genome-wide association studies have identified robust genetic associations with AF. METHODS: We genotyped 5461 participants of Japanese ancestry for 11 AF-related loci and determined the effects of carrying different numbers of risk alleles on disease development and age at disease onset. The weighted genetic risk score (GRS) was calculated, and its ability to predict AF was determined. RESULTS: Six single-nucleotide polymorphisms-rs593479 (1q24 in PRRX1), rs1906617 (4q25 near PITX2), rs11773845 (7q31 in CAV1), rs6584555 (10q25 in NEURL), rs6490029 (12q24 in CUX2), and rs12932445 (16q22 in ZFHX3) (P < 1.9 × 10-5)-were confirmed as being associated with AF. Patients with a high total number of risk alleles (9-12) had a younger median age at onset of AF (58 years; 95% confidence interval [CI], 55-60 years) than those with a low total number (1-4) (63 years; 95% CI, 61-64 years) (P = 0.0015). We observed a 4.38-fold (95% CI, 3.69-5.19) difference in risk of AF between individuals with scores in the top and bottom quartiles of the GRS. Receiver operating characteristic analysis indicated an area under the curve of 0.641 (95% CI, 0.628-0.653; P < 0.0001). CONCLUSIONS: Six loci were validated as associated with AF in a Japanese population. This study suggests that a combination of common genetic markers modestly facilitates discrimination of AF. This is the first report, to our knowledge, to demonstrate that the age of onset of AF is affected by common risk alleles.

Identification of six new genetic loci associated with atrial fibrillation in the Japanese population.

Atrial fibrillation is the most common cardiac arrhythmia and leads to stroke. To investigate genetic loci associated with atrial fibrillation in the Japanese population, we performed a genome-wide association study (GWAS) that included 8,180 atrial fibrillation cases and 28,612 controls with follow-up in an additional 3,120 cases and 125,064 controls. We replicated previously reported loci and identified six new loci, near the KCND3, PPFIA4, SLC1A4-CEP68, HAND2, NEBL and SH3PXD2A genes. Five of the six new loci were specifically associated with atrial fibrillation in the Japanese population after comparing our data to those from individuals of European ancestry, suggesting that there might be different genetic factors affecting susceptibility across ancestry groups. Our study discovered variants in the HAND2, KCND3 and NEBL genes, which are relevant to atrial fibrillation susceptibility. The involvement of PPFIA4 and SH3PXD2A in axon guidance also suggested a role in disease pathogenesis. Our findings may contribute to a better understanding of atrial fibrillation susceptibility and pathogenesis.

Dielectric permittivity change detects the process of blood coagulation: Comparative study of dielectric coagulometry with rotational thromboelastometry.

BACKGROUND: Intravascular thrombus formation causes various cardiovascular diseases. To monitor coagulation is important for screening native status, prevention from bleeding and maintaining it within its therapeutic range. The prothrombin time and the activated partial thromboplastin time are widely used for assessment and recognized as the conventional methods. Prothrombin time methods employ enhancement of coagulation with thromboplastin. Since the laboratory data depend on the production lot and/or the manufacturer, the accurate methods are required for evaluation. Rotational thromboelastometry (ROTEM) is a method based on detection of the change in resistance to rotational movement during blood clotting, while dielectric blood coagulometry (DBCM) is a novel method for assessment of clotting by measuring the change of electrical permittivity. These methods are thus based on the technology for observation of different physical phenomena. The aim of this study was to compare parameters such as the clotting time obtained by ROTEM and DBCM to evaluate their clinical usefulness. METHODS AND RESULTS: ROTEM and DBCM parameters were measured in 128 patients. The ROTEM clotting time showed a significant positive correlation with the DBCM coagulation time (R=0.707, p<0.001). Comparison of the DBCM coagulation time between patients with and without anticoagulant therapy (including novel oral anticoagulants) revealed a significant difference (43.8±11.9min in the anticoagulant group vs 29.4±8.3min in the control group, p<0.001). Evaluation of coagulation was equivalent with DBCM and ROTEM. CONCLUSIONS: The present study suggested that DBCM, a novel method for measuring blood clotting, could provide the detail assessment for the status of anticoagulant therapy.

Novel Dielectric Coagulometer Identifies Hypercoagulability in Patients with a High CHADS2 Score without Atrial Fibrillation.

BACKGROUND: Recent reports showed that the CHADS2 score predicted the risk of strokes in patients without atrial fibrillation (AF). Although the hypercoagulability may contribute to the thrombogenesis, it has not been fully investigated due to a lack of a sensitive evaluation modality. Recently a novel dielectric blood coagulometry (DBCM) was invented for evaluating the coagulability by measuring the temporal change in whole blood dielectric permittivity. OBJECTIVE: We evaluated the utility of the DBCM for identifying the coagulability. PATIENTS/METHODS: For fundamental experiments, 133 citrated blood samples were drawn from subjects with or without heparin administration. A DBCM analysis was performed to find the adequate coagulation index, and to delineate its measurement range by adding recombinant human tissue factor (TF) or heparin. Then the coagulability was assessed by DBCM and conventional coagulation assays in 84 subjects without AF, who were divided into 3 groups by their CHADS2 score. Another 17 patients who received warfarin were also assessed by DBCM to evaluate the effect of anticoagulants. RESULTS AND CONCLUSIONS: We calculated the derivative of the dielectric permittivity change after recalcification, and extracted the end of acceleration time (EAT) as a novel index. The EAT showed a dose-dependent shortening with the addition of serial dilutions of TF (×10-2 to ×10-4), and a dose-dependent prolongation with the addition of heparin (0.05 to 0.15 U/ml). The EAT was significantly shorter in the higher CHADS2 score group (19.8 ± 4.8, 18.6 ± 3.1, and 16.3 ± 2.7 min in the CHADS2 = 0, 1, and ≥2 groups, respectively, p = 0.0065 by ANOVA). Patients receiving warfarin had a significantly more prolonged EAT than those without warfarin (18.6±4.2 vs. 25.8±7.3 min, p <0.001). DBCM detected the whole blood coagulability with a high sensitivity. Subjects with higher CHADS2 scores exhibited hypercoagulability without AF.

Aromatase knockout mice reveal an impact of estrogen on drug-induced alternation of murine electrocardiography parameters.

Our in vitro characterization showed that physiological concentrations of estrogen partially suppressed the I(Kr) channel current in guinea pig ventricular myocytes and the human ether-a-go-go-related gene (hERG) channel currents in CHO-K1 cells regardless of estrogen receptor signaling and revealed that the partially suppressed hERG currents enhanced the sensitivity to the hERG blocker E-4031. To obtain in vivo proof-of-concept data to support the effects of estrogen on cardiac electrophysiology, we here employed an aromatase knockout mouse as an in vivo estrogen-null model and compared the acute effects of E-4031 on cardiac electrophysiological parameters with those in wild-type mice (C57/BL6J) by recording surface electrocardiogram (ECG). The ablation of circulating estrogens blunted the effects of E-4031 on heart rate and QT interval in mice under a denervation condition. Our result provides in vivo proof of principle and demonstrates that endogenous estrogens increase the sensitivity of E-4031 to cardiac electrophysiology.

A functional SNP in ITIH3 is associated with susceptibility to myocardial infarction.

Myocardial infarction (MI) results from complex interactions of multiple genetic and environmental factors. To disclose genetic backgrounds of MI, we performed a large-scale, case-control association study using 52,608 gene-based single-nucleotide polymorphism (SNP) markers, and identified a candidate SNP located on chromosome 3p21.2-p21.1. Subsequent linkage-disequilibrium mapping indicated very significant association between MI and a SNP in exon 2 of the inter-alpha (globulin) inhibitor 3 gene (ITIH3; chi(2) = 24.88, P = 6.1 x 10(-7), 3,353 affected individuals versus 3,807 controls). In vitro functional analyses showed that this SNP enhanced the transcriptional level of the ITIH3 gene. Furthermore, we found expression of the ITIH3 protein in the vascular smooth muscle cells and macrophages in the human atherosclerotic lesions, suggesting ITIH3 SNP to be a novel genetic risk factor of MI.