Mitsuhiro Yokota

Meta-analysis of genome-wide association studies identifies common variants associated with blood pressure variation in East Asians

We conducted a meta-analysis of genome-wide association studies of systolic (SBP) and diastolic (DBP) blood pressure in 19,608 subjects of east Asian ancestry from the AGEN-BP consortium followed up with de novo genotyping (n = 10,518) and further replication (n = 20,247) in east Asian samples. We identified genome-wide significant (P < 5 × 10−8) associations with SBP or DBP, which included variants at four new loci (ST7L-CAPZA1, FIGN-GRB14, ENPEP and NPR3) and a newly discovered variant near TBX3. Among the five newly discovered variants, we obtained significant replication in the independent samples for all of these loci except NPR3. We also confirmed seven loci previously identified in populations of European descent. Moreover, at 12q24.13 near ALDH2, we observed strong association signals (P = 7.9 × 10−31 and P = 1.3 × 10−35 for SBP and DBP, respectively) with ethnic specificity. These findings provide new insights into blood pressure regulation and potential targets for intervention.

Meta-analysis identifies common variants associated with body mass index in east Asians.

Multiple genetic loci associated with obesity or body mass index (BMI) have been identified through genome-wide association studies conducted predominantly in populations of European ancestry. We performed a meta-analysis of associations between BMI and approximately 2.4 million SNPs in 27,715 east Asians, which was followed by in silico and de novo replication studies in 37,691 and 17,642 additional east Asians, respectively. We identified ten BMI-associated loci at genome-wide significance (P < 5.0 × 10−8), including seven previously identified loci (FTO, SEC16B, MC4R, GIPR-QPCTL, ADCY3-DNAJC27, BDNF and MAP2K5) and three novel loci in or near the CDKAL1, PCSK1 and GP2 genes. Three additional loci nearly reached the genome-wide significance threshold, including two previously identified loci in the GNPDA2 and TFAP2B genes and a newly identified signal near PAX6, all of which were associated with BMI with P < 5.0 × 10−7. Findings from this study may shed light on new pathways involved in obesity and demonstrate the value of conducting genetic studies in non-European populations.

Blood Pressure and Hypertension Are Associated With 7 Loci in the Japanese Population

Background— Two consortium-based genome-wide association studies have recently identified robust and significant associations of common variants with systolic and diastolic blood pressures in populations of European descent, warranting further investigation in populations of non-European descent. Methods and Results— We examined the associations at 27 loci reported by the genome-wide association studies on Europeans in a screening panel of Japanese subjects (n=1526) and chose 11 loci showing association signals (1-tailed test in the screening, P<0.3) for an extensive replication study with a follow-up panel of 3 Japanese general-population cohorts (n ≤24 300). Significant associations were replicated for 7 loci—CASZ1, MTHFR, ITGA9, FGF5, CYP17A1-CNNM2, ATP2B1, and CSK-ULK3—with any or all of these 3 traits: systolic blood pressure (P=1.4×10−14 to 0.05), diastolic blood pressure (P=1.9×10−12 to 0.05), and hypertension (P=2.0×10−14 to 0.006; odds ratio, 1.10 to 1.29). The strongest association was observed for FGF5. In the whole study panel, the variance (R2) for blood pressure explained by the 7 single-nucleotide polymorphism loci was calculated to be R2=0.003 for male and 0.006 for female participants. Stratified analysis implied the potential presence of a gene-age-sex interaction, although it did not reach a conclusive level of statistical significance after adjustment for multiple testing. Conclusions— We have confirmed 7 loci associated with blood pressure and/or hypertension in the Japanese. These loci can guide fine-mapping efforts to pinpoint causal variants and causal genes with the integration of multiethnic results.

Genome-wide association study of coronary artery disease in the Japanese.

A new understanding of the genetic basis of coronary artery disease (CAD) has recently emerged from genome-wide association (GWA) studies of common single-nucleotide polymorphisms (SNPs), thus far performed mostly in European-descent populations. To identify novel susceptibility gene variants for CAD and confirm those previously identified mostly in populations of European descent, a multistage GWA study was performed in the Japanese. In the discovery phase, we first genotyped 806 cases and 1337 controls with 451 382 SNP markers and subsequently assessed 34 selected SNPs with direct genotyping (541 additional cases) and in silico comparison (964 healthy controls). In the replication phase, involving 3052 cases and 6335 controls, 12 SNPs were tested; CAD association was replicated and/or verified for 4 (of 12) SNPs from 3 loci: near BRAP and ALDH2 on 12q24 (P=1.6 × 10−34), HLA-DQB1 on 6p21 (P=4.7 × 10−7), and CDKN2A/B on 9p21 (P=6.1 × 10−16). On 12q24, we identified the strongest association signal with the strength of association substantially pronounced for a subgroup of myocardial infarction cases (P=1.4 × 10−40). On 6p21, an HLA allele, DQB1*0604, could show one of the most prominent association signals in an ∼8-Mb interval that encompasses the LTA gene, where an association with myocardial infarction had been reported in another Japanese study. CAD association was also identified at CDKN2A/B, as previously reported in different populations of European descent and Asians. Thus, three loci confirmed in the Japanese GWA study highlight the likely presence of risk alleles with two types of genetic effects – population specific and common – on susceptibility to CAD.

Frequency, predictors and outcome of stent fracture after sirolimus-eluting stent implantation

BACKGROUND Recently, stent fracture (SF) of sirolimus-eluting stents (SES) has been shown to be associated with an increased risk of in-stent restenosis. We sought to evaluate the incidence, predictors and clinical outcome of SF after SES implantation in comparable unselected lesions. METHODS A total of 430 lesions of 382 patients treated with SES were analyzed. SF was defined as single or multiple stent strut fracture as well as complete separation of stent segments. RESULTS At follow-up, SF was identified in 33 of 430 lesions (7.7%). In lesions with SF, the in-stent restenosis was observed more frequently than non-SF lesions (15.2% vs. 4.0%, P=0.004). At 450 days, however, the cumulative rate of major cardiac events was not significantly different between lesions with and without SF (9.1% vs. 7.1%, P=0.722). The risk of SF was independently associated with total stent length (OR 2.22; 95% CI, 1.25 to 3.95; P=0.007), the change in the angulation of the lesion after stenting (OR 1.55; 95% CI, 1.07 to 2.25; P=0.020), and the right coronary artery lesions (OR 3.26; 95% CI, 1.18 to 8.96; P=0.022). CONCLUSIONS The occurrence of SF after SES implantation, was found to be relatively common in the particular population, however, did not lead to an increased risk of adverse cardiac events at 450 days, despite a higher incidence of in-stent restenosis.

A genome-wide association study of a coronary artery disease risk variant

Although over 30 common genetic susceptibility loci have been identified to be independently associated with coronary artery disease (CAD) risk through genome-wide association studies (GWAS), genetic risk variants reported to date explain only a small fraction of heritability. To identify novel susceptibility variants for CAD and confirm those previously identified in European population, GWAS and a replication study were performed in the Koreans and Japanese. In the discovery stage, we genotyped 2123 cases and 3591 controls with 521 786 SNPs using the Affymetrix SNP Array 6.0 chips in Korean. In the replication, direct genotyping was performed using 3052 cases and 4976 controls from the KItaNagoya Genome study of Japan with 14 selected SNPs. To maximize the coverage of the genome, imputation was performed based on 1000 Genome JPT+CHB and 5.1 million SNPs were retained. CAD association was replicated for three GWAS-identified loci (1p13.3/SORT1 (rs599839), 9p21.3/CDKN2A/2B (rs4977574), and 11q22.3/ PDGFD (rs974819)) in Koreans. From GWAS and a replication, SNP rs3782889 showed a strong association (combined P=3.95 × 10−14), although the association of SNP rs3782889 doesn’t remain statistically significant after adjusting for SNP rs11066015 (proxy SNP with BRAP (r2=1)). But new possible CAD-associated variant was observed for rs9508025 (FLT1), even though its statistical significance did marginally reach at the genome-wide a significance level (combined P=6.07 × 10−7). This study shows that three CAD susceptibility loci, which were previously identified in European can be directly replicated in Koreans and also provides additional evidences implicating suggestive loci as risk variants for CAD in East Asian.

Exercise Training Alters Left Ventricular Geometry and Attenuates Heart Failure in Dahl Salt-Sensitive Hypertensive Rats

The clinical efficacy of exercise training in individuals with heart failure is well established, but the mechanism underlying such efficacy has remained unclear. An imbalance between cardiac hypertrophy and angiogenesis is implicated in the transition to heart failure. We investigated the effects of exercise training on cardiac pathophysiology in hypertensive rats. Dahl salt-sensitive rats fed a high-salt diet from 6 weeks of age were assigned to sedentary or exercise (swimming)-trained groups at 9 weeks. Exercise training attenuated the development of heart failure and increased survival, without affecting blood pressure, at 18 weeks. It also attenuated left ventricular concentricity without a reduction in left ventricular mass or impairment of cardiac function. Interstitial fibrosis was increased and myocardial capillary density was decreased in the heart of sedentary rats, and these effects were attenuated by exercise. Exercise potentiated increases in the phosphorylation of Akt and mammalian target of rapamycin observed in the heart of sedentary rats, whereas it inhibited the downregulation of proangiogenic gene expression apparent in these animals. The abundance of the p110&agr; isoform of phosphatidylinositol 3-kinase was decreased, whereas those of the p110&ggr; isoform of phosphatidylinositol 3-kinase and the phosphorylation of extracellular signal-regulated kinase and p38 mitogen-activated protein kinase were increased, in the heart of sedentary rats, and all of these effects were prevented by exercise. Thus, exercise training had a beneficial effect on cardiac remodeling and attenuated heart failure in hypertensive rats, with these effects likely being attributable to the attenuation of left ventricular concentricity and restoration of coronary angiogenesis through activation of phosphatidylinositol 3-kinase(p110&agr;)-Akt-mammalian target of rapamycin signaling.

Plasma resistin concentration determined by common variants in the resistin gene and associated with metabolic traits in an aged Japanese population

AbstractAims/hypothesisResistin is a cytokine derived from adipose tissue and is implicated in obesity-related insulin resistance and type 2 diabetes mellitus. Polymorphisms of the resistin gene (RETN) have been shown to affect the plasma resistin concentration. The aims of this study were to identify polymorphisms of RETN that influence plasma resistin concentration and to clarify the relation between plasma resistin level and metabolic disorders in an aged Japanese cohort.MethodsThe study participants comprised 3133 individuals recruited to a population-based prospective cohort study (KING study). Plasma resistin concentration, BMI, abdominal circumference, blood pressure, fasting plasma glucose and serum insulin concentrations, HbA1c content and serum lipid profile were measured in all participants. The HOMA index of insulin resistance (HOMA-IR) was also calculated. Eleven polymorphisms of RETN were genotyped.ResultsA combination of ANOVA and multiple linear regression analysis in screening and large-scale subsets of the study population revealed that plasma resistin concentration was significantly associated with rs34861192 and rs3745368 polymorphisms of RETN. Multiple linear regression analysis with adjustment for age and sex also showed that the plasma resistin level was significantly associated with serum concentrations of HDL-cholesterol, triacylglycerol and insulin, as well as with BMI.Conclusions/interpretationOur results implicate the rs34861192 and rs3745368 polymorphisms of RETN as robust and independent determinants of plasma resistin concentration in the study population. In addition, plasma resistin level was associated with dyslipidaemia, serum insulin concentration and obesity. Trial registration: ClinicalTrials.gov NCT00262691 Funding: This study was supported by Grants-in-Aids for Scientific Research from the Japan Society for the Promotion of Science and the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

Superoxide-Dependent Cathepsin Activation Is Associated with Hypertensive Myocardial Remodeling and Represents a Target for Angiotensin II Type 1 Receptor Blocker Treatment

The elastolytic activity of cathepsins in the myocardium is implicated in hypertensive heart failure (HF). Given that reactive oxygen species are also implicated in protease activation associated with cardiac remodeling, we examined the role of the reactive oxygen species-induced cathepsin activation system in cardiac remodeling during the development of hypertensive HF. Dahl salt-sensitive hypertensive rats maintained on a high-salt diet were treated with vehicle, the cathepsin inhibitor E64d, or the angiotensin receptor blocker olmesartan from 12 to 19 weeks of age. Cathepsin expression and activity were increased in the left ventricle of HF rats; olmesartan inhibited these effects, restored the balance between elastin and collagen in the left ventricle, and suppressed degradation of the elastic lamina of coronary arteries of HF rats. Furthermore, olmesartan inhibited up-regulation of NADPH oxidase subunits and activity as well as superoxide generation. These effects of olmesartan were mimicked by E64d and were accompanied by amelioration of cardiac fibrosis. Finally, olmesartan and apocynin reduced angiotensin II-induced increases in cathepsin mRNA and protein levels in cultured rat neonatal cardiac myocytes. These data suggest that cathepsins likely trigger and promote cardiac remodeling and that blocking the angiotensin II type 1 receptor attenuates cathepsin expression and activity by inhibiting the production of superoxide by NADPH oxidase, thereby attenuating cardiac remodeling and dysfunction.

Pioglitazone attenuates cardiac hypertrophy in rats with salt-sensitive hypertension: role of activation of AMP-activated protein kinase and inhibition of Akt.

Objective Cardiac hypertrophy is common in diabetes and an independent risk factor for cardiac morbidity and mortality. We investigated the effects of pioglitazone on cardiac hypertrophy and hypertrophic signaling in Dahl salt-sensitive hypertensive rats. Methods Dahl salt-sensitive rats were fed a high-salt diet from 7 weeks of age and treated with pioglitazone (2.5 mg/kg per day) or vehicle from 7 to 11 weeks. Results The vehicle-treated rats developed left ventricular hypertrophy and fibrosis as well as left ventricular diastolic dysfunction. The serum level of adiponectin and the phosphorylation of AMP-activated protein kinase in the myocardium did not differ between the vehicle-treated rats and control rats maintained on a normal diet. The phosphorylation of Akt, mammalian target of rapamycin, and p70S6 kinase as well as the total protein content were increased in the heart of vehicle-treated rats compared with control rats, and these changes were blocked by treatment with pioglitazone. Pioglitazone treatment also ameliorated left ventricular hypertrophy and fibrosis, improved diastolic function, and increased both the serum adiponectin concentration and the level of AMP-activated protein kinase phosphorylation in the heart. Conclusions Long-term administration of pioglitazone attenuated left ventricular hypertrophy and fibrosis as well as inhibited phosphorylation of mammalian target of rapamycin and p70S6 kinase in the heart of hypertensive rats. The beneficial cardiac effects of pioglitazone are likely attributable, at least partly, both to the activation of AMP-activated protein kinase signaling through stimulation of adiponectin secretion and to the inhibition of Akt signaling.