Haemochromatosis gene mutations in idiopathic dilated cardiomyopathy

BACKGROUND—Two common mutations of the haemochromatosis associated gene (HFE) (cys282tyr (C282Y) and his63asp (H63D)) have been implicated in haemochromatosis and as modulators in cardiovascular disease.
OBJECTIVE—To investigate the role of these mutations in the pathogenesis of idiopathic dilated cardiomyopathy.
DESIGN AND SETTING—Case-control and prospective cohort study of patients attending a cardiomyopathy unit in a tertiary referral cardiac centre.
METHODS—207 unrelated white patients with dilated cardiomyopathy, followed up for 259 patient years, and 200 controls were tested for HFE C282Y and H63D mutations by polymerase chain reaction and restriction digestion.
RESULTS—31/207 patients (15%) v 24/200 controls (12%) carried C282Y (adjusted odds ratio (OR) 1.2 (95% confidence interval 0.7 to 2.2)), 74/207 (36%) v 53/200 (27%) carried H63D (OR 1.6 (1.1 to 2.5)), and 10/207 (4.8%) v 4/200 (2%) were compound heterozygotes (OR 2.6 (0.8 to 8.5)). Four patients and six controls were H63D homozygous and one was C282Y homozygous. There was a progressive increase in mean serum iron ([Fe]) and transferrin saturations from patients with no mutation ([Fe] = 16.3 µmol/l, transferrin saturation = 23.7%) through H63D heterozygotes (17.5 µmol/l, 25.8%), C282Y heterozygotes (17.1 µmol/l, 26.6%), H63D homozygotes (20.0 µmol/l, 33.5%), compound heterozygotes (26.8 µmol/l, 41.7%), and C282Y homozygotes (34 µmol/l, 71%). At follow up (median 90 months) the rate of death or cardiac transplantation was 52/207 (25%). C282Y heterozygotes had less ventricular dilatation (mean (SD): 59.9 (1.7) mm v 64.9 (0.9) mm, p < 0.05), better fractional shortening (24 (1.7)% v 18.8 (1.4)%, p < 0.01), and a trend towards improved survival without transplantation. [Fe] and transferrin saturation did not correlate with disease severity and were not associated with reduced survival.
CONCLUSIONS—The frequency of the H63D mutation is significantly increased in patients with idiopathic dilated cardiomyopathy. As H63D has a relatively minor effect on iron status, the mechanism of this association may be unrelated to iron metabolism.


Keywords: dilated cardiomyopathy; genetics; haemochromatosis     

Severe disease expression of cardiac troponin C and T mutations in patients with idiopathic dilated cardiomyopathy

OBJECTIVES: We performed genetic investigations of cardiac troponin T (TNNT2) and troponin C (TNNC1) in 235 consecutive patients with idiopathic dilated cardiomyopathy (DCM) to evaluate prevalence of mutations and associated disease expression in affected families. BACKGROUND: Recently, mutations in sarcomeric genes have been reported in DCM. However, the prevalence, penetrance, and clinical significance of sarcomere gene mutations in large consecutive cohorts of DCM patients are poorly defined. METHODS: Mutation detection was performed by fluorescent SSCP/DHPLC analysis and direct sequencing. The functional effects of mutations on interactions within the troponin complex were assessed by a two-hybrid luciferase assay. RESULTS: A total of 43% (102 of 235) of the study cohort had familial DCM. One TNNC1 and four TNNT2 (three novel) mutations were identified in one and four families, respectively. The prevalence of TNNC1/TNNT2 mutations in familial DCM was 5% with a penetrance of 100%. A total of 21 mutation carriers were identified; 6 underwent cardiac transplantation, 5 died of heart failure, and 4 died suddenly at a mean age of 29 years, while 6 remained stable on medication.Functional studies showed significant impairment of mutated troponin interaction compared with wild-type control, indicating an altered regulation of myocardial contractility. CONCLUSIONS: Cardiac troponin C was identified as a novel DCM gene. The disease expression associated with TNNC1 and TNNT2 mutations was severe with complete penetrance. The data suggest that mutation analysis of the troponin complex in DCM patients may prove valuable in early identification of individuals with an adverse prognosis and a high risk of premature death. This may lead to improved management and survival.     

Lamin A/C haploinsufficiency causes dilated cardiomyopathy and apoptosis-triggered cardiac conduction system disease

Mutations in the lamin A/C (LMNA) gene, which encodes nuclear membrane proteins, cause a variety of human conditions including dilated cardiomyopathy (DCM) with associated cardiac conduction system disease. To investigate mechanisms responsible for electrophysiologic and myocardial phenotypes caused by dominant human LMNA mutations, we performed longitudinal evaluations in heterozygous Lmna^+/− mice. Despite one normal allele, Lmna^+/− mice had 50% of normal cardiac lamin A/C levels and developed cardiac abnormalities. Conduction system function was normal in neonatal Lmna^+/− mice but, by 4 weeks of age, atrioventricular (AV) nodal myocytes had abnormally shaped nuclei and active apoptosis. Telemetric and in vivo electrophysiologic studies in 10-week-old Lmna^+/− mice showed AV conduction defects and both atrial and ventricular arrhythmias, analogous to those observed in humans with heterozygous LMNA mutations. Isolated myocytes from 12-month-old Lmna^+/− mice exhibited impaired contractility. In vivo cardiac studies of aged Lmna^+/− mice revealed DCM; in some mice this occurred without overt conduction system disease. However, neither histopathology nor serum CK levels indicated skeletal muscle pathology. These data demonstrate cardiac pathology due to heterozygous Lmna mutations reflecting a 50% reduction in lamin protein levels. Lamin haploinsufficiency caused early-onset programmed cell death of AV nodal myocytes and progressive electrophysiologic disease. While lamin haploinsufficiency was better tolerated by non-conducting myocytes, ultimately, these too succumbed to diminished lamin levels leading to dilated cardiomyopathy, which presumably arose independently from conduction system disease.     

Familial dilated cardiomyopathy in patients transplanted for idiopathic dilated cardiomyopathy

OBJECTIVE: To evaluate the prevalence, clinical features, and pattern of inheritance of familial dilated cardiomyopathy (DCM) in heart transplant patients. PATIENTS AND METHOD: Patients with idiopathic DCM who had undergone heart transplantation were invited to participate. Patients with alcohol abuse were excluded. A clinical evaluation, 12-lead ECG, echocardiogram, blood tests, and DNA extraction were performed in patients and relatives. Familial DCM was defined as the presence of at least one relative with idiopathic DCM. Possible familial DCM was considered when at least one relative had left ventricular enlargement (LVE) (> 112% predicted LVEDD). RESULTS: One hundred and ninety-nine relatives of 43 families were studied. DCM was familial in 11 probands (25.6%) and possibly familial in 11 (25.6%). Fifteen relatives had DCM (7.5%), 26 (13.1%) LVE, and 5 (2.5%) hypertrophic cardiomyopathy. The pattern of inheritance was autosomal dominant in most families. Five probands (3 with familial DCM) had antecedents of consanguinity and possible recessive inheritance. Six probands (14%, 1 with familial DCM) had relatives with conduction system defects. Creatine kinase was moderately increased in 9 relatives (4.5%), 3 of them with LVE. Fifteen patients had at least moderate alcohol intake. Three of them had familial DCM (relatives without alcohol abuse) and 6 had possible familial DCM. CONCLUSIONS: The prevalence of familial DCM is high in patients who undergo heart transplant. Left ventricular enlargement, conduction system abnormalities, and elevated creatine kinase may be early markers of familial disease. Hypertrophic cardiomyopathy is present in some relatives of patients with idiopathic DCM. Familial DCM is present in patients with a previous diagnosis of alcoholic DCM.     

T-lymphocyte subsets in patients with idiopathic dilated cardiomyopathy

T-cell subsets were measured in the peripheral blood of 33 patients with heart failure from idiopathic dilated cardiomyopathy, 22 patients with heart failure from other causes, and 33 normal controls. Mean T-suppressor cell percentage was 30% in normals, 21% in patients with idiopathic dilated cardiomyopathy whose duration of symptoms was less than 1 year (P = 0.0005), and 26% in those with symptoms for greater than 1 year (P = 0.05). Similarly, percentage of T-suppressor cells in the group with heart failure from causes other than idiopathic dilated cardiomyopathy was significantly lower (23%; P = 0.005) in those with short duration of symptoms. When both heart failure groups were combined those with symptoms for less than 1 year had significantly lower T-suppressor frequencies (22%) than those with symptoms for more than 1 year (P = 0.015). Multivariate analysis identified duration of symptoms and age as the only independent predictors of T-suppressor cell frequencies. Decreased percentage of T-suppressor cells in patients with idiopathic dilated cardiomyopathy may be an epiphenomenon related to duration of heart failure. This should be taken into account in assigning an etiologic mechanism for T-suppressor cells in idiopathic dilated cardiomyopathy.     

Circulating tenascin-C levels in patients with idiopathic dilated cardiomyopathy

Circulating serum tenascin-C (an extracellular matrix glycoprotein) levels in patients with idiopathic dilated cardiomyopathy (IDC) were measured. Serum tenascin-C levels were increased in proportion to the severity of left ventricular dysfunction in patients with IDC. The associations of serum tenascin-C levels with serum troponin T and procollagen type III aminoterminal peptide levels suggest that increased levels of serum tenascin-C indicate ongoing replacement fibrosis after myocardial damage in IDC.     

肌联蛋白基因突变与中国人扩张型心肌病

目的 肌联蛋白是由单基因编码的最大蛋白,普遍存在于心肌和骨骼肌,被称为第三肌丝,具有复杂的牛物力学性质和牛物化学功能.2002年日本研究人员报道r肌联蛋白基因(TTN)第3、14、49号外显子的4个基凶突变町能与扩张型心肌病(DCM)发病相关,我国未见相关报道.本研究通过寻找我同DCM患者是否存在TTN的突变,探讨在中国人基因背景下可能存在的TTN的突变及其与我国DCM发病的关系.方法 采用聚合酶链反应-单链构象多态件(PCR-SSCP)方法、聚丙烯酰胺凝胶电泳及DNA序列测定等方法对117例DCM患者和120例健康对照者TTN的第3、14、49号外显子的多个位点进行检测、分析.结果 在我国DCM患者和健康对照者中未发现与日本DCM患者相同位点的基因突变,而在2例有明显DCM家族史的儿章患者(1.7%)中新发现了位于TTN第49号外显子的13053位点基凶突变--G→A突变(G13053A),其导敛第4351位点氨基酸由甘氨酸变为大冬氨酸(Gly4351Asp),在健康对照组巾未发现此改变.结论 本研究首次在中国DCM患者中发现存在于TTN第49号外显子的基因错义突变,该突变可能是DCM重要的病因学机制,尤其可能与早发DCM相关.     

Natural history of dilated cardiomyopathy due to lamin A/C gene mutations

OBJECTIVES: We examined the prevalence, genotype-phenotype correlation, and natural history of lamin A/C gene (LMNA) mutations in subjects with dilated cardiomyopathy (DCM). BACKGROUND: Mutations in LMNA have been found in patients with DCM with familial conduction defects and muscular dystrophy, but the clinical spectrum, prognosis, and clinical relevance of laminopathies in DCM are unknown. BACKGROUND: A cohort of 49 nuclear families, 40 with familial DCM and 9 with sporadic DCM (269 subjects, 105 affected), was screened for mutations in LMNA using denaturing high-performance liquid chromatography and sequence analysis. Bivariate analysis of clinical predictors of LMNA mutation carrier status and Kaplan-Meier survival analysis were performed. RESULTS: Mutations in LMNA were detected in four families (8%), three with familial (R89L, 959delT, R377H) and one with sporadic DCM (S573L). There was significant phenotypic variability, but the presence of skeletal muscle involvement (p < 0.001), supraventricular arrhythmia (p = 0.003), conduction defects (p = 0.01), and "mildly" DCM (p = 0.006) were predictors of LMNA mutations. The LMNA mutation carriers had a significantly poorer cumulative survival compared with non-carrier DCM patients: event-free survival at the age of 45 years was 31% versus 75% in non-carriers. CONCLUSIONS: Mutations in LMNA cause a severe and progressive DCM in a relevant proportion of patients. Mutation screening should be considered in patients with DCM, in particular when clinical predictors of LMNA mutation are present, regardless of family history.     

特发性扩张型心肌病与HLA-A*基因的关联研究

目的探讨特发性扩张型心肌病（idiopathic dilated cardiomyopathy，IDC）易感的分子机制和确立一种人类主要组织相容性复合体（HLA—A＊）基因的检测方法。方法采用聚合酶链式反应和顺序特异性引物（PCR—SSP）基因分析方法，对31例特发性扩张型心肌病患者及29例无血缘关系的健康人的HIA—A＊各等位基因及亚基因进行检测分析，并将该方法与其他检测HIA等位基因的方法进行对比。结果HIA—A＊ 03基因与IDC呈正相关（RR=4．697，P〈0．05），其他HIA—A＊各等位基因未见异常。结论HIA—A＊03基因可能是北方汉族人IDC的致病易感基因之一。采用的方法（PCR—SSP）具有快速、简便、敏感、准确和可靠等优点，值得推广。     

Novel lamin A/C mutations in two families with dilated cardiomyopathy and conduction system disease

BACKGROUND: The LMNA gene, one of 6 autosomal disease genes implicated in familial dilated cardiomyopathy, encodes lamins A and C, alternatively spliced nuclear envelope proteins. Mutations in lamin A/C cause 4 diseases: Emery-Dreifuss muscular dystrophy, limb girdle muscular dystrophy type 1B, Dunnigan-type familial partial lipodystrophy, and dilated cardiomyopathy. METHODS AND RESULTS: Two 4-generation white families with autosomal dominant familial dilated cardiomyopathy and conduction system disease were found to have novel mutations in the rod segment of lamin A/C. In family A a missense mutation (nucleotide G607A, amino acid E203K) was identified in 14 adult subjects; disease was manifest as progressive conduction disease in the fourth and fifth decades. Death was caused by heart failure. In family B a nonsense mutation (nucleotide C673T, amino acid R225X) was identified in 10 adult subjects; disease was also manifest as progressive conduction disease but with earlier onset (third and fourth decades), ventricular dysrhythmias, left ventricular enlargement, and systolic dysfunction. Death was caused by heart failure and sudden cardiac death. Skeletal muscle disease was not observed in either family. CONCLUSIONS: Novel rod segment mutations in lamin A/C cause variable conduction system disease and dilated cardiomyopathy without skeletal myopathy.     

Coronary endothelial dysfunction in patients with acute-onset idiopathic dilated cardiomyopathy

Objectives. This study sought to determine whether coronary endothelial dysfunction exists in patients with acute-onset idiopathic dilated cardiomyopathy (DCM) and to explore its relation to recovery of left ventricular systolic function in this patient population.Background. Coronary endothelial dysfunction exists in chronic DCM, but its importance in the development and progression of ventricular dysfunction is not known. To address this issue we studied coronary endothelial function in patients with idiopathic DCM <6 months in duration and explored the relation between coronary endothelial function and subsequent changes in left ventricular ejection fraction (LVEF).Methods. Ten patients with acute-onset idiopathic DCM (duration of heart failure symptoms 2.0 ± 0.4 months [mean ± SEM]) and 11 control patients with normal left ventricular function underwent assessment of coronary endothelial function during intracoronary administration of the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator adenosine. Coronary cross-sectional area (CSA) was determined by quantitative coronary angiography and coronary blood flow (CBF) by the product of coronary CSA and CBF velocity measured by an intracoronary Doppler catheter. Patients with DCM underwent assessment of left ventricular function before and several months after the study.Results. Acetylcholine infusion produced no change in coronary CSA in control patients but significant epicardial constriction in patients with DCM (−36 ± 11%, p < 0.01). These changes were associated with increases in CBF in control patients (+118 ± 49%, p < 0.01) but no change in patients with DCM. Infusion of adenosine produced increases in coronary caliber and blood flow in both groups. Follow-up assessment of left ventricular function was obtained in nine patients with DCM 7.0 ± 1.7 months after initial study, at which time LVEF had improved by ≥0.10 in four patients. Multiple linear regression revealed a positive correlation between both the coronary CSA (r² = 0.57, p < 0.05) and CBF (r² = 0.68, p < 0.01) response to acetylcholine and the subsequent improvement in LVEF.Conclusions. Coronary endothelial dysfunction exists at both the microvascular and the epicardial level in patients with acute-onset idiopathic DCM. The preservation of coronary endothelial function in this population is associated with subsequent improvement in left ventricular function.