Tomoya Nakano

Nuclear accumulation of androgen receptor in gender difference of dilated cardiomyopathy due to lamin A/C mutations

AIMS Dilated cardiomyopathy (DCM) is characterized by ventricular dilation associated with systolic dysfunction, which could be caused by mutations in lamina/C gene (LMNA). LMNA-linked DCM is severe in males in both human patients and a knock-in mouse model carrying a homozygous p.H222P mutation (LmnaH222P/H222P). The aim of this study was to investigate the molecular mechanisms underlying the gender difference of LMNA-linked DCM. METHODS AND RESULTS A whole-exome analysis of a multiplex family with DCM exhibiting the gender difference revealed a DCM-linked LMNA mutation, p.R225X. Immunohistochemical analyses of neonatal rat cardiomyocytes expressing mutant LMNA constructs and heart samples from the LMNA-linked DCM patients and LmnaH222P/H222P mice demonstrated a nuclear accumulation of androgen receptor (AR) and its co-activators, serum response factor, and four-and-a-half LIM protein-2. Role of sex hormones in the gender difference was investigated in vivo using the LmnaH222P/H222P mice, where male and female mice were castrated and ovariectomized, respectively, or treated with testosterone or an antagonist of AR. Examination of the mice by echocardiography, followed by the analyses of histological changes and gene/protein expression profiles in the hearts, confirmed the involvement of testicular hormone in the disease progression and enhanced cardiac remodelling in the LmnaH222P/H222P mice. CONCLUSION These observations indicated that nuclear accumulation of AR was associated with the gender difference in LMNA-linked DCM.

Sex differences in clinical characteristics and long-term outcome in acute decompensated heart failure patients with preserved and reduced ejection fraction.

In patients with acute decompensated heart failure (ADHF), sex differences considering clinical and pathophysiologic features are not fully understood. We investigated sex differences in left ventricular (LV) ejection fraction (LVEF), plasma B-type natriuretic peptide (BNP) levels, and prognostic factors in patients with ADHF in Japan. We studied 748 consecutive ADHF patients of 821 patients registered in the ADHF registry between January 2007 and December 2014. Patients were divided into four groups based on sex and LVEF [reduced (ejection fraction, or EF, <50%, heart failure with reduced EF, or HFrEF) or preserved (EF ≥50%, heart failure with preserved LVEF, or HFpEF)]. The primary endpoint was the combination of cardiovascular death and heart failure (HF) admission. The present study consisted of 311 female patients (50% HFrEF, 50% HFpEF) and 437 male patients (63% HFrEF, 37% HFpEF). There was significant difference between sexes in the LVEF distribution profile. The ratio of HFpEF patients was significantly higher in female patients than in male patients (P= 0.0004). Although there were no significant sex differences in median plasma BNP levels, the prognostic value of BNP levels was different between sexes. Kaplan-Meier analysis revealed that the high BNP group had worse prognosis than the low BNP group in male but not in female patients. In multivariate analysis, log transformed BNP at discharge predicted cardiovascular events in male but not in female HF patients (female, hazard ratio: 1.169; 95% confidence interval: 0.981-1.399;P= 0.0806; male, hazard ratio: 1.289; 95% confidence interval: 1.120-1.481;P= 0.0004). In patients with ADHF, the distribution of LV function and the prognostic significance of plasma BNP levels for long-term outcome were different between the sexes.

Evaluation of left ventricular diastolic function by fractional area change using cine cardiovascular magnetic resonance: a feasibility study

BackgroundEvaluation of left ventricular (LV) diastolic function is essential for the management of heart failure. We verified whether LV diastolic function could be evaluated by measuring the fractional area change (FAC) using cine cardiovascular magnetic resonance (CMR).MethodsWe collected clinical data from 59 patients who underwent echocardiography and cine CMR. Normal, impaired relaxation, pseudonormal, and restrictive LV filling were observed in 15, 28, 11, and 5 patients, respectively. We calculated FAC during the first 30% of diastole (diastolic-index%) in the short-axis view, by tracing the contours on only three MR cine images.ResultsThe diastolic index was significantly lower (p < 0.0001) in patients with impaired relaxation (32.4 ± 7.5), pseudonormal filling (25.4 ± 5.6), and restrictive filling (9.5 ± 1.5) compared to those with normal diastolic function (67.7 ± 10.8), and the index decreased significantly with worsening of diastolic dysfunction. The diastolic index correlated positively with early diastolic mitral annular velocity measured by tissue Doppler imaging (r = 0.75, p < 0.0001), respectively.ConclusionsMeasurement of FAC can be useful for the evaluation of LV diastolic function using cine CMR.

Early onset of cardiomyopathy and intellectual disability in a girl with Danon disease associated with a de novo novel mutation of the LAMP2 gene

Danon disease, primary lysosome‐associated membrane protein‐2 (LAMP‐2) deficiency, is characterized clinically by cardiomyopathy, myopathy and intellectual disability in boys. Because Danon disease is inherited in an X‐linked dominant fashion, males are more severely affected than females, who usually have only cardiomyopathy without myopathy or intellectual disability; moreover, the onset of symptoms in females is usually in adulthood. We describe a girl with Danon disease who presented with hypertrophic cardiomyopathy and Wolff‐Parkinson‐White (WPW) syndrome at 12 years of age. Subsequently, she showed signs of mild learning disability and intellectual disability on psychological examinations. She had a de novo novel mutation in the LAMP‐2 gene and harbored an identical c.749C > A (p.Ser250X) variant, resulting in a stop codon in exon 6. She showed decreased, but not completely absent LAMP‐2 expression on immunohistochemical and Western blot analyses of a skeletal muscle biopsy specimen, which has been suggested to be caused by a 50% reduction in LAMP‐2 expression (LAMP‐2 haploinsufficiency) in female patients with Danon disease caused by a heterozygous null mutation. To our knowledge, our patient is one of the youngest female patients to have been given a diagnosis of Danon disease. In addition, this is the first documented case in a girl that was clearly associated with intellectual disability, which is very rare in females with Danon disease. Our findings suggest that studies of female patients with Danon disease can extend our understanding of the clinical features of this rare disease.

Suppressed Production of Soluble Fms-Like Tyrosine Kinase-1 Contributes to Myocardial Remodeling and Heart Failure.

Soluble fms-like tyrosine kinase-1 (sFlt-1), an endogenous inhibitor of vascular endothelial growth factor and placental growth factor, is involved in the pathogenesis of cardiovascular disease. However, the significance of sFlt-1 in heart failure has not been fully elucidated. We found that sFlt-1 is decreased in renal failure and serves as a key molecule in atherosclerosis. In this study, we aimed to investigate the role of the decreased sFlt-1 production in heart failure, using sFlt-1 knockout mice. sFlt-1 knockout mice and wild-type mice were subjected to transverse aortic constriction and evaluated after 7 days. The sFlt-1 knockout mice had significantly higher mortality (52% versus 15%; P=0.0002) attributable to heart failure and showed greater cardiac hypertrophy (heart weight to body weight ratio, 8.95±0.45 mg/g in sFlt-1 knockout mice versus 6.60±0.32 mg/g in wild-type mice; P<0.0001) and cardiac dysfunction, which was accompanied by a significant increase in macrophage infiltration and cardiac fibrosis, than wild-type mice after transverse aortic constriction. An anti–placental growth factor–neutralizing antibody prevented pressure overload–induced cardiac hypertrophy, fibrosis, and cardiac dysfunction. Moreover, monocyte chemoattractant protein-1 expression was significantly increased in the hypertrophied hearts of sFlt-1 knockout mice compared with wild-type mice. Monocyte chemoattractant protein-1 inhibition with neutralizing antibody ameliorated maladaptive cardiac remodeling in sFlt-1 knockout mice after transverse aortic constriction. In conclusion, decreased sFlt-1 production plays a key role in the aggravation of cardiac hypertrophy and heart failure through upregulation of monocyte chemoattractant protein-1 expression in pressure-overloaded heart.

Electron Microscopic Findings Are an Important Aid for Diagnosing Mitochondrial Cardiomyopathy With Mitochondrial DNA Mutation 3243A>G.

Mitochondrial disease can be caused by defects in either mitochondrial or nuclear DNA, but mtDNA mutations are the most common cause in adult.1 Among these mutations, m.3243A>G mutation (MTTL) was first identified in patients with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome.2 The mutation is located in the gene encoding tRNALeu and results in impaired protein synthesis and electron transport chain dysfunction.2 Cardiomyopathy is seen in 40% of the symptomatic individuals, usually left ventricular hypertrophy with hypokinesis,3 which however is often overlooked when the patients show few phenotypes typical for mitochondrial disease. The patient (case 1) was a 60-year-old man admitted to Nara Medical University Hospital because of dyspnea due to congestive heart failure. He had hypertension and diabetes mellitus for nearly 10 years and had been hard of hearing for 2 years. His mother also …

Prognostic Value of Urinary Neutrophil Gelatinase‐Associated Lipocalin on the First Day of Admission for Adverse Events in Patients With Acute Decompensated Heart Failure

Background Urinary neutrophil gelatinase‐associated lipocalin (U‐NGAL) is an early predictor of acute kidney injury and adverse events in various diseases; however, in acute decompensated heart failure patients, its significance remains poorly understood. This study aimed to investigate the prognostic value of U‐NGAL on the first day of admission for the occurrence of acute kidney injury and long‐term outcomes in acute decompensated heart failure patients. Methods and Results We studied 260 acute decompensated heart failure patients admitted to our department between 2011 and 2014 by measuring U‐NGAL in 24‐hour urine samples collected on the first day of admission. Primary end points were all‐cause death, cardiovascular death, and heart failure admission. Patients were divided into 2 groups according to their median U‐NGAL levels (32.5 μg/gCr). The high‐U‐NGAL group had a significantly higher occurrence of acute kidney injury during hospitalization than the low‐U‐NGAL group (P=0.0012). Kaplan‐Meier analysis revealed that the high‐U‐NGAL group exhibited a worse prognosis than the low‐U‐NGAL group in all‐cause death (hazard ratio 2.07; 95%CI 1.38‐3.12, P=0.0004), cardiovascular death (hazard ratio 2.29; 95%CI 1.28‐4.24, P=0.0052), and heart failure admission (hazard ratio 1.77; 95%CI 1.13‐2.77, P=0.0119). The addition of U‐NGAL to the estimated glomerular filtration rate significantly improved the predictive accuracy of all‐cause mortality (P=0.0083). Conclusions In acute decompensated heart failure patients, an elevated U‐NGAL level on the first day of admission was related to the development of clinical acute kidney injury and independently associated with poor prognosis.

Alteration of β-Adrenoceptor Signaling in Left Ventricle of Acute Phase Takotsubo Syndrome: a Human Study

Accumulating evidence indicates alteration of the β-adrenoceptor (AR), such as desensitization and subtype switching of its coupling G protein, plays a role in the protection against catecholamine toxicity in heart failure. However, in human takotsubo syndrome (TTS), which is associated with a surge of circulating catecholamine in the acute phase, there is no histologic evidence of β-AR alteration. The purpose of this study was to investigate the involvement of alteration of β-AR signaling in the mechanism of TTS development. Left ventricular (LV) biopsied samples from 26 patients with TTS, 19 with normal LV function, and 26 with dilated cardiomyopathy (DCM) were studied. G protein-coupled receptor kinase 2 (GRK2) and β-arrestin2, which initiate the alteration of β-AR signaling, were more abundantly expressed in the myocardium in acute-phase TTS than in those of DCM and normal control as indicated by immunohistochemistry. The percentage of cardiomyocytes that showed positive membrane staining for GRK2 and β-arrestin2 was also significantly higher in acute-phase TTS. Sequential biopsies in the recovery-phase for two patients with TTS revealed that membrane expression of GRK2 and β-arrestin2 faded over time. This study provided the first histologic evidence of the involvement of alteration of β-ARs in the development of TTS.

Mitochondrial deformity confined to a single cardiomyocyte in human endomyocardial biopsy specimens: Report of 4 cases

During electron microscopic examination of 156 consecutive human endomyocardial biopsy specimens, we found marked mitochondrial deformity within a single cardiomyocyte in each of 4 specimens. The deformed mitochondria were unevenly distributed, but the deformities were confined to the one cardiomyocyte. Those affected cardiomyocytes were accompanied by nonspecific degenerative changes such as nuclear hypertrophy and/or rarefaction of the myofibrils. Mitochondria in all other cells within the specimens appeared normal. Such an abnormality has never been reported to date. Each of the four cases was diagnosed with a different ailment: post-myocarditis, dilated cardiomyopathy, amyloidosis, and tachycardia-induced heart failure. However, all four cases were accompanied by left ventricular systolic dysfunction at biopsy. The very limited mitochondrial deformation may thus reflect a type of degenerative change that accompanies heart failure. <Learning objective: A marked mitochondrial deformity must have been overlooked to date, which is confined to a single cardiomyocyte in an endomyocardial biopsy specimen. Its etiology is still unknown but may reflect a type of degenerative change that accompanies heart failure.>.

Salt accelerates aldosterone-induced cardiac remodeling in the absence of guanylyl cyclase-A signaling.

AIMS Excess sodium causes the development of cardiovascular diseases in conjunction with enhancing renin-angiotensin-aldosterone system (RAAS). Natriuretic peptides are sodium regulators and prevent pathological cardiac alterations by counteracting RAAS. However, it is unknown whether natriuretic peptides inhibit the sodium effect in adverse cardiac alterations. Here, we investigated whether excess salt intake could exacerbate cardiac remodeling in mice with impaired natriuretic peptide signaling. MATERIALS AND METHODS Mice lacking the gene encoding the natriuretic peptide receptor, guanylyl cyclase-A (GC-A), and wild-type mice were administered with either a vehicle substance or a subpressor dose of aldosterone (100ng/kg/min), alongside low salt (0.001% NaCl), normal salt (0.6% NaCl), or high salt diets (6.0% NaCl) for four weeks. Mice were then sacrificed and the hearts were evaluated by histology and RT-PCR. KEY FINDINGS Salt load did not induce cardiac changes in vehicle and aldosterone groups in wild-type mice. On the other hand, cardiac hypertrophy and interstitial fibrosis were significantly exacerbated in a salt dependent manner in GC-A knockout (KO) mice administered aldosterone, and were associated with enhanced gene expression relevant to hypertrophy, fibrosis, and oxidative stress conditions. Of note, excess salt intake increased the expression of Sgk1, serum and glucocorticoid responsive kinase-1, in aldosterone-administered GC-A KO mice. These molecular changes were not observed in wild-type mice. SIGNIFICANCE The results of the present study demonstrate that excess salt intake induced cardiac remodeling in conjunction with aldosterone administration in GC-A KO mice, indicating that GC-A signaling attenuated the deleterious salt effect in aldosterone-induced cardiac remodeling.