BackgroundPatients with inherited dilated cardiomyopathy (DCM) frequently die with severe heart failure (HF) or die suddenly with arrhythmias, although these symptoms are not always observed at birth. It remains unclear how and when HF and arrhythmogenic changes develop in these DCM mutation carriers. In order to address this issue, properties of the myocardium and underlying gene expressions were studied using a knock-in mouse model of human inherited DCM caused by a deletion mutation ΔK210 in cardiac troponinT.Methodology/Principal FindingsBy 1 month, DCM mice had already enlarged hearts, but showed no symptoms of HF and a much lower mortality than at 2 months or later. At around 2 months, some would die suddenly with no clear symptoms of HF, whereas at 3 months, many of the survivors showed evident symptoms of HF. In isolated left ventricular myocardium (LV) from 2 month-mice, spontaneous activity frequently occurred and action potential duration (APD) was prolonged. Transient outward (Ito) and ultrarapid delayed rectifier K+ (IKur) currents were significantly reduced in DCM myocytes. Correspondingly, down-regulation of Kv4.2, Kv1.5 and KChIP2 was evident in mRNA and protein levels. In LVs at 3-months, more frequent spontaneous activity, greater prolongation of APD and further down-regulation in above K+ channels were observed. At 1 month, in contrast, infrequent spontaneous activity and down-regulation of Kv4.2, but not Kv1.5 or KChIP2, were observed.Conclusions/SignificanceOur results suggest that at least three steps of electrical remodeling occur in the hearts of DCM model mice, and that the combined down-regulation of Kv4.2, Kv1.5 and KChIP2 prior to the onset of HF may play an important role in the premature sudden death in this DCM model. DCM mice at 1 month or before, on the contrary, are associated with low risk of death in spite of inborn disorder and enlarged heart.

Background: The bromocresol green (BCG) assay is commonly used for measuring albumin (ALB), but is affected by 1 -and 2 -globulins, which are elevated in systemic inflammation. The modified bromocresol purple (mBCP) assay is another dye-binding method developed to overcome non-specific reactions. Concentrations of 2 -macroglobulin, a major 2 -globulin component, are increased in nephrotic syndrome (NS), but not in inflammation. There is little direct evidence that 2 -macroglobulin affects BCG or mBCP assays. Methods: We measured serum albumin concentrations in 33 patients with NS and 13 reference healthy controls using BCG (ALB BCG ) and mBCP (ALB mBCP ) assays, and nephelometry (nALB) as a reference method. We also determined five specific proteins belonging to the 1 -and 2 -globulins by nephelometry. After adding purified 2 -macroglobulin to albumin solutions, protein reactivity in these three assays was compared. Results: Nephrotic syndrome patients were categorized to tertiles according to nALB concentration. In all tertiles, ALB BCG was significantly higher than nALB, especially in the severe hypoalbuminemia group, in which 2 -macroglobulin was 43-49% higher. By contrast, ALB mBCP and nALB were almost identical in all three groups. The difference between ALB BCG and nALB was positively correlated with the 2 -macroglobulin concentration. In vitro, when 2 -macroglobulin was added to solutions containing identical albumin concentrations, 2 -macroglobulin dose-dependently increased ALB BCG , but not ALB mBCP . Conclusions: In NS, 2 -macroglobulin is a major factor for positive bias of ALB BCG , especially in patients with severe hypoalbuminemia. The mBCP assay is useful for measuring albumin concentrations in NS.

BackgroundInherited dilated cardiomyopathy (DCM) is a progressive disease that often results in death from congestive heart failure (CHF) or sudden cardiac death (SCD). Mouse models with human DCM mutation are useful to investigate the developmental mechanisms of CHF and SCD, but knowledge of the severity of CHF in live mice is necessary. We aimed to diagnose CHF in live DCM model mice by measuring voluntary exercise using a running wheel and to determine causes of death in these mice.Methodology/Principal FindingsA knock-in mouse with a mutation in cardiac troponin T (ΔK210) (DCM mouse), which results in frequent death with a t1/2 of 70 to 90 days, was used as a DCM model. Until 2 months of age, average wheel-running activity was similar between wild-type and DCM mice (approximately 7 km/day). At approximately 3 months, some DCM mice demonstrated low running activity (LO: <1 km/day) while others maintained high running activity (HI: >5 km/day). In the LO group, the lung weight/body weight ratio was much higher than that in the other groups, and the lungs were infiltrated with hemosiderin-loaded alveolar macrophages. Furthermore, echocardiography showed more severe ventricular dilation and a lower ejection fraction, whereas Electrocardiography (ECG) revealed QRS widening. There were two patterns in the time courses of running activity before death in DCM mice: deaths with maintained activity and deaths with decreased activity.Conclusions/SignificanceOur results indicate that DCM mice with low running activity developed severe CHF and that running wheels are useful for detection of CHF in mouse models. We found that approximately half of ΔK210 DCM mice die suddenly before onset of CHF, whereas others develop CHF, deteriorate within 10 to 20 days, and die.

Inherited dilated cardiomyopathy (DCM) is characterized by dilatation and dysfunction of the ventricles, and often results in sudden death or heart failure (HF). Although angiotensin receptor blockers (ARBs) have been used for the treatment of HF, little is known about the effects on postulated electrical remodeling that occurs in inherited DCM. The aim of this study was to examine the effects of candesartan, one of the ARBs, on cardiac function and electrical remodeling in the hearts of inherited DCM model mice (TNNT2 ΔK210). DCM mice were treated with candesartan in drinking water for 2 months from 1 month of age. Control, non-treated DCM mice showed an enlargement of the heart with prolongation of QRS and QT intervals, and died at t1/2 of 70 days. Candesartan dramatically extended the lifespan of DCM mice, suppressed cardiac dilatation, and improved the functional parameters of the myocardium. It also greatly suppressed prolongation of QRS and QT intervals and action potential duration (APD) in the left ventricular myocardium and occurrence of ventricular arrhythmia. Expression analysis revealed that down-regulation of Kv4.2 (Ito channel protein), KChIP2 (auxiliary subunit of Kv4.2), and Kv1.5 (IKur channel protein) in DCM was partially reversed by candesartan administration. Interestingly, non-treated DCM heart had both normal-sized myocytes with moderately decreased Ito and IKur and enlarged cells with greatly reduced K+ currents (Ito, IKur IK1 and Iss). Treatment with candesartan completely abrogated the emergence of the enlarged cells but did not reverse the Ito, and IKur in normal-sized cells in DCM hearts. Our results indicate that candesartan treatment suppresses structural remodeling to prevent severe electrical remodeling in inherited DCM.

Background: During the development of heart failure, a fetal cardiac gene program is reactivated and accelerates pathological cardiac remodeling. We previously reported that a transcriptional repressor, neuron restrictive silencer factor (NRSF), suppresses the fetal cardiac gene program, thereby maintaining cardiac integrity. The underlying molecular mechanisms remains to be determined, however. Methods: We aim to elucidate molecular mechanisms by which NRSF maintains normal cardiac function. We generated cardiac-specific NRSF knockout mice and analyzed cardiac gene expression profiles in those mice and mice cardiac-specifically expressing a dominant-negative NRSF mutant. Results: We found that cardiac expression of Gαo, an inhibitory G protein encoded in humans by GNAO1, is transcriptionally regulated by NRSF and is increased in the ventricles of several mouse models of heart failure. Genetic knockdown of Gnao1 ameliorated the cardiac dysfunction and prolonged survival rates in these mouse heart failure models. Conversely, cardiac-specific overexpression of GNAO1 in mice was sufficient to induce cardiac dysfunction. Mechanistically, we observed that increasing Gαo expression increased surface sarcolemmal L-type Ca 2+ channel activity, activated Calcium/calmodulin-dependent kinase-II (CaMKII) signaling and impaired Ca 2+ handling in ventricular myocytes, which led to cardiac dysfunction. Conclusions: These findings shed light on a novel function of Gαo in the regulation of cardiac Ca 2+ homeostasis and systolic function and suggest Gαo may be an effective therapeutic target for the treatment of heart failure.