Yubao Zou

Mutations in NEXN, a Z-Disc Gene, Are Associated with Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM), the most common inherited cardiac disorder, is characterized by increased ventricular wall thickness that cannot be explained by underlying conditions, cadiomyocyte hypertrophy and disarray, and increased myocardial fibrosis. In as many as 50% of HCM cases, the genetic cause remains unknown, suggesting that more genes may be involved. Nexilin, encoded by NEXN, is a cardiac Z-disc protein recently identified as a crucial protein that functions to protect cardiac Z-discs from forces generated within the sarcomere. We screened NEXN in 121 unrelated HCM patients who did not carry any mutation in eight genes commonly mutated in myofilament disease. Two missense mutations, c.391C>G (p.Q131E) and c.835C>T (p.R279C), were identified in exons 5 and 8 of NEXN, respectively, in two probands. Each of the two mutations segregated with the HCM phenotype in the family and was absent in 384 control chromosomes. In silico analysis revealed that both of the mutations affect highly conserved amino acid residues, which are predicted to be functionally deleterious. Cellular transfection studies showed that the two mutations resulted in local accumulations of nexilin and that the expressed fragment of actin-binding domain containing p.Q131E completely lost the ability to bind F-actin in C2C12 cells. Coimmunoprecipitation assay indicated that the p.Q131E mutation decreased the binding of full-length NEXN to α-actin and abolished the interaction between the fragment of actin-binding domain and α-actin. Therefore, the mutations in NEXN that we describe here may further expand the knowledge of Z-disc genes in the pathogenesis of HCM.

MiR-221 promotes cardiac hypertrophy in vitro through the modulation of p27 expression.

Cardiac hypertrophy has been known as an independent predictor for cardiovascular morbidity and mortality. Molecular mechanisms underlying the development of heart failure remain elusive. Recently, microRNAs (miRs) have been established as important regulators in cardiac hypertrophy. Here, we reported miR‐221 was up‐regulated in both transverse aortic constricted mice and patients with hypertrophic cardiomyopathy (HCM). Forced expression of miR‐221 by transfection of miR‐221 mimics increased myocyte cell size and induced the re‐expression of fetal genes, which were inhibited by the knockdown of endogenous miR‐221 in cardiomyocytes. The TargetScan algorithm‐based prediction identified that p27, a cardiac hypertrophic suppressor, is the putative target of miR‐221, which was confirmed by luciferase assay and Western blotting.

Plasma concentrations of interleukin-6, C-reactive protein, tumor necrosis factor-α and matrix metalloproteinase-9 in aortic dissection

BACKGROUND The role of inflammation in aortic dissection (AD) has not fully been investigated. We evaluated the potential relationships between interleukin-6 (IL-6), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and matrix metalloproteinase-9 (MMP-9) and AD. METHODS Plasma concentrations of IL-6, TNF-α, MMP-9 and CRP were determined in 64 acute AD patients, 42 patients with chronic AD, 98 patients with hypertension alone, and 96 healthy subjects. RESULTS IL-6 concentrations were higher in acute AD than that in hypertension and healthy controls (10.98±2.38 vs. 3.79±1.56 and 3.32±1.60 pg/ml, P<0.05, respectively). Increased CRP concentrations were found in acute AD compared with chronic AD and hypertension as well as healthy subjects (13.48±3.74 vs. 4.12±2.99, 1.62±0.65 and 1.12±0.35 mg/l, P<0.001, respectively). Higher MMP-9 concentrations were detected in acute AD, chronic AD and hypertension compared with healthy controls (37.75±9.38, 55.78±6.41 and 31.03±7.94 vs. 21.24±7.28 ng/ml, P<0.05, P<0.001 and P<0.05, respectively), and in the dead compared to the survived (107.29±9.38 vs. 86.80±7.93 ng/ml, P<0.001) among acute AD patients. In acute AD, the time after onset had positive correlation with TNF-α (r=0.497, P=0.000), and negative correlation with CRP (r=-0.424, P=0.000). Plasma CRP levels decreased significantly when the onset time increased (P=0.013). Moreover, in the patients with acute AD who underwent surgery and stenting, plasma MMP-9 concentrations increased immediately after surgical treatment and stenting, and reached the peak values at 24h, then decreased at 1 week (P<0.001). CONCLUSIONS Our findings confirmed and extended previous studies that increased plasma inflammatory markers were significantly associated with AD.

MiR-451 is decreased in hypertrophic cardiomyopathy and regulates autophagy by targeting TSC1.

The molecular mechanisms that drive the development of cardiac hypertrophy in hypertrophic cardiomyopathy (HCM) remain elusive. Accumulated evidence suggests that microRNAs are essential regulators of cardiac remodelling. We have been suggested that microRNAs could play a role in the process of HCM. To uncover which microRNAs were changed in their expression, microRNA microarrays were performed on heart tissue from HCM patients (n = 7) and from healthy donors (n = 5). Among the 13 microRNAs that were differentially expressed in HCM, miR‐451 was the most down‐regulated. Ectopic overexpression of miR‐451 in neonatal rat cardiomyocytes (NRCM) decreased the cell size, whereas knockdown of endogenous miR‐451 increased the cell surface area. Luciferase reporter assay analyses demonstrated that tuberous sclerosis complex 1 (TSC1) was a direct target of miR‐451. Overexpression of miR‐451 in both HeLa cells and NRCM suppressed the expression of TSC1. Furthermore, TSC1 was significantly up‐regulated in HCM myocardia, which correlated with the decreased levels of miR‐451. As TSC1 is a known positive regulator of autophagy, we examined the role of miR‐451 in the regulation of autophagy. Overexpression of miR‐451 in vitro inhibited the formation of the autophagosome. Conversely, miR‐451 knockdown accelerated autophagosome formation. Consistently, an increased number of autophagosomes was observed in HCM myocardia, accompanied by up‐regulated autophagy markers, and the lipidated form of LC3 and Beclin‐1. Taken together, our findings indicate that miR‐451 regulates cardiac hypertrophy and cardiac autophagy by targeting TSC1. The down‐regulation of miR‐451 may contribute to the development of HCM and may be a potential therapeutic target for this disease.

Rare Variants in Genes Encoding MuRF1 and MuRF2 Are Modifiers of Hypertrophic Cardiomyopathy

Modifier genes contribute to the diverse clinical manifestations of hypertrophic cardiomyopathy (HCM), but are still largely unknown. Muscle ring finger (MuRF) proteins are a class of muscle-specific ubiquitin E3-ligases that appear to modulate cardiac mass and function by regulating the ubiquitin-proteasome system. In this study we screened all the three members of the MuRF family, MuRF1, MuRF2 and MuRF3, in 594 unrelated HCM patients and 307 healthy controls by targeted resequencing. Identified rare variants were confirmed by capillary Sanger sequencing. The prevalence of rare variants in both MuRF1 and MuRF2 in HCM patients was higher than that in control subjects (MuRF1 13/594 (2.2%) vs. 1/307 (0.3%), p = 0.04; MuRF2 22/594 (3.7%) vs. 2/307 (0.7%); p = 0.007). Patients with rare variants in MuRF1 or MuRF2 were younger (p = 0.04) and had greater maximum left ventricular wall thickness (p = 0.006) than those without such variants. Mutations in genes encoding sarcomere proteins were present in 19 (55.9%) of the 34 HCM patients with rare variants in MuRF1 and MuRF2. These data strongly supported that rare variants in MuRF1 and MuRF2 are associated with higher penetrance and more severe clinical manifestations of HCM. The findings suggest that dysregulation of the ubiquitin-proteasome system contributes to the pathogenesis of HCM.

Clinical Manifestations and Longterm Outcome for Patients with Takayasu Arteritis in China

Objective. To describe a large cohort of patients with Takayasu arteritis in China. Methods. We retrospectively analyzed 566 patients hospitalized in Fuwai Hospital between 2002 and 2013. Data collected were clinical characteristics, laboratory findings, angiographic features, treatment, and longterm outcome. Results. The female to male ratio was 3.8 to 1, and the mean age of onset was 28.9 ± 12.0 years. The most common inflammatory symptom, initial symptom, and coexisting disease were fever (52, 9.2%), dizziness (214, 37.8%), and hypertension (HTN; 392, 69.3%), respectively. Pulmonary artery, coronary artery involvement, and aortic regurgitation were found in 83 (14.7%), 66 (11.7%), and 181 (36.7%) patients, respectively. Elevation of the erythrocyte sedimentation rate was observed in 131 patients (23.1%). Treatment included drugs, interventional therapy, autologous blood vessel transplant, artificial blood vessel transplant, and aortic valve replacement. During a mean followup of 5.0 ± 0.2 years, 32 patients died, including 1 patient who died suddenly during coronary angiography. HTN, major complications, and a progressive disease course were significant prognostic markers. Conclusion. HTN, rather than fever, is the leading reason for patients with Takayasu arteritis to see a doctor in China. HTN, major complications, and a progressive disease course are statistically significant predictors of survival. Because of cardiovascular events associated with the disease, early diagnosis and treatment are urgent to improve prognosis.

Isolated left ventricular noncompaction: clinical profile and prognosis in 106 adult patients

This study was undertaken to evaluate the clinical course of isolated left ventricular noncompaction (ILVNC) and to identify the predictors for adverse outcomes in an adult cohort with ILVNC. Between March 2003 and April 2012, 106 adult patients diagnosed with ILVNC at Fuwai Hospital were included in this study. The medical history, electrocardiograms, and echocardiograms of these patients were retrospectively analyzed by chart review. Of these patients, 64 (60 %) were in New York Heart Association (NYHA) functional class III/IV and 84 (79 %) had systolic dysfunction (left ventricular ejection fraction (LVEF) <50 %). During a follow-up of 2.9 ± 2.1 years, 28 (26 %) patients died or underwent heart transplantation. The annual incidence of death or transplantation was 9.1 %. The determinants of death or heart transplantation included NYHA functional class III/IV (hazard ratio (HR) 4.52; 95 % confidence interval (CI) 1.57–13.04; P = 0.005), decreased left ventricular ejection fraction (HR 0.94; 95 % CI 0.90–0.97; P = 0.001), dilated left ventricular end-diastolic diameter (HR, 1.06; 95 % CI, 1.02–1.09; P = 0.001), increased left atrial diameter (HR 1.08; 95 % CI 1.03–1.14; P = 0.001), reduced systolic blood pressure (HR 0.96; 95 % CI 0.94–0.99; P = 0.003), the presence of pulmonary hypertension (HR 3.50; 95 % CI 1.63–7.51; P = 0.001), and right bundle branch block (HR 7.79; 95 % CI 2.56–23.76; P < 0.001). In conclusion, this study demonstrates that ILVNC is related to a high incidence of death or heart transplantation. Advanced heart failure, a dilated left heart with systolic dysfunction, reduced systolic blood pressure, pulmonary hypertension, and right bundle branch block predict adverse outcomes of ILVNC.

Cardiac-Specific Overexpression of miR-222 Induces Heart Failure and Inhibits Autophagy in Mice

Background: MicroRNAs play a crucial role in the regulation of pathological cardiac remodeling and heart failure. Previously, we found that overexpression of miR-221 induces heart failure in mice. The miR-222 and miR-221 share the same gene cluster, however, the role of miR-222 in the regulation of cardiac function remained ill-defined. Methods and Results: Transgenic mice with cardiac-specific expression of miR-222 (Tg-miR-222) mice were generated. The Tg-miR-222 mice developed significantly enlarged hearts at 4 weeks of age. Transthoracic echocardiograph data indicated that the hearts of Tg-miR-222 mice exhibited an increased left ventricular end-diastolic internal diameter and decreased fractional shortening. We observed that the LC3-II in Tg-miR-222 mice was decreased accompanied with the upregulation of p62, indicating the autophagy inhibition in the hearts of Tg-miR-222 mice. The mTOR pathway, a negative regulator of autophagy, was activated in the hearts of Tg-miR-222 mice. The expression of p27 was downregulated by miR-222 overexpression. Conclusion: Our data indicate that miR-222 overexpression induces heart failure in mice. The downregulation of p27 and the activation of mTOR pathway may be involved in miR-222-induced heart failure and autophagy inhibition. Thus, targeting miR-222 expression may be a therapeutic strategy against pathological cardiac remodeling.

Fat Deposition in Dilated Cardiomyopathy Assessed by CMR

OBJECTIVES The aim of this study was to prospectively investigate the prevalence of fat deposition in idiopathic dilated cardiomyopathy (DCM) by fat-water separation imaging. An auxiliary aim was to determine the relationship between left ventricular (LV) fat deposition and characteristic myocardial fibrosis, as well as cardiac functional parameters. BACKGROUND Idiopathic DCM remains the most common cause of heart failure in young people referred for cardiac transplantation; little is known about the clinical value of fat deposition in DCM. METHODS A total of 124 patients with DCM were studied after written informed consent was obtained. The magnetic resonance imaging scan protocols included a series of short-axis LV cine imaging for functional analysis, fat-water separation imaging, and late gadolinium enhancement (LGE) imaging. Fat deposition and fibrosis location were compared to the scar regions on LGE images using a 17-segment model. Statistical comparisons of LV global functional parameters, fibrosis volumes, and fat deposition were carried out using the Pearson correlation, Student t test, and multiple regressions. RESULTS The patients had a 41.9% (52 of 124) prevalence of positive LGE, and 12.9% (16 of 124) fat deposition prevalence was found in this DCM cohort. The patients with fat deposition had larger LV end-diastolic volume (LVEDV) index (140.8 ± 20.2 ml/m(2) vs. 123.4 ± 15.8 ml/m(2); p < 0.01), larger LV end-systolic volume (LVESV) index (111.3 ± 19.2 ml/m(2) vs. 87.0 ± 20.3 ml/m(2); p < 0.01), and decreased LV ejection fraction (LVEF) (21.1 ± 7.1% vs. 30.0 ± 10.7%; p < 0.01). Higher volumes of LGE were found in the group with myocardial fat deposition (18.39 ± 9.0 ml vs. 13.40 ± 6.54 ml; p = 0.001), as well as a higher percentage of LGE/LV mass (19.11 ± 7.78% vs. 13.60 ± 4.58%; p = 0.000). The volume of fat deposition was correlated with scar volume, LVEF, LVEDV index, and LVESV index. CONCLUSIONS Fat deposition is a common phenomenon in DCM, and it is associated with DCM characteristics such as fibrosis volume and LV function.

Prevalence of Liddle Syndrome Among Young Hypertension Patients of Undetermined Cause in a Chinese Population

Liddle syndrome, an autosomal dominant form of monogenic hypertension, has been regarded as a rare disorder, which leads to many Liddle syndrome patients being misdiagnosed and experiencing severe complications at an early age. Little is known about the prevalence of Liddle syndrome. In this study, the authors investigated the prevalence of Liddle syndrome confirmed by genetic testing among young hypertension patients of undetermined causes in China. A total of 330 hypertensive patients aged 14 to 40 years after exclusion of common secondary causes of hypertension were enrolled and serum potassium concentrations were measured. Patients with hypokalemia underwent genetic testing of the 13th exon of genes encoding β and γ subunits of the epithelial sodium channel (ENaC). Diagnosis was established by identification of mutations that destroy the PY motif of ENaC. Five patients were diagnosed with Liddle syndrome (prevalence, 1.52%), as well as 12 of their relatives. These patients with Liddle syndrome presented with an earlier onset of hypertension, a stronger family history of hypertension, and higher blood pressure than those with essential hypertension. All patients had hypokalemia and suppressed plasma renin activity. The results demonstrated that Liddle syndrome is an important etiology of hypertension in this young population. Screening of Liddle syndrome should focus on young hypertension patients, particularly those with early penetrance, hypokalemia, and low renin levels after exclusion of common secondary causes.