Cardiac Muscle Pathology Research Articles

Integrin α7 Mutations Are Associated With Adult-Onset Cardiac Dysfunction in Humans and Mice.

Background Integrin α7β1 is a major laminin receptor in skeletal and cardiac muscle. In skeletal muscle, integrin α7β1 plays an important role during muscle development and has been described as an important modifier of skeletal muscle diseases. The integrin α7β1 is also highly expressed in the heart, but its precise role in cardiac function is unknown. Mutations in the integrin α7 gene (ITGA7) have been reported in children with congenital myopathy. Methods and Results In this study, we described skeletal and cardiac muscle pathology in Itga7-/- mice and 5 patients from 2 unrelated families with ITGA7 mutations. Proband in family 1 presented a homozygous c.806_818del [p.S269fs] variant, and proband in family 2 was identified with 2 intron variants in the ITGA7 gene. The complete absence of the integrin α7 protein in muscle supports the ITGA7 mutations are pathogenic. We performed electrocardiography, echocardiography, or cardiac magnetic resonance imaging, and histological biopsy analyses in patients with ITGA7 deficiency and Itga7-/- mice. The patients exhibited cardiac dysrhythmia and dysfunction from the third decade of life and late-onset respiratory insufficiency, but with relatively mild limb muscle involvement. Mice demonstrated corresponding abnormalities in cardiac conduction and contraction as well as diaphragm muscle fibrosis. Conclusions Our data suggest that loss of integrin α7 causes a novel form of adult-onset cardiac dysfunction indicating a critical role for the integrin α7β1 in normal cardiac function and highlights the need for long-term cardiac monitoring in patients with ITGA7-related congenital myopathy.

Cardiac and respiratory muscle responses to dietary N-acetylcysteine in rats consuming a high-saturated fat, high-sucrose diet.

What is the central question of this study? This study addresses whether a high-fat, high-sucrose diet causes cardiac and diaphragm muscle abnormalities in male rats and whether supplementation with the antioxidant N-acetylcysteine reverses diet-induced dysfunction. What is the main finding and its importance? N-Acetylcysteine attenuated the effects of high-fat, high-sucrose diet on markers of cardiac hypertrophy and diastolic dysfunction, but neither high-fat, high-sucrose diet nor N-acetylcysteine affected the diaphragm. These results support the use of N-acetylcysteine to attenuate cardiovascular dysfunction induced by a 'Western' diet. Individuals with overweight or obesity display respiratory and cardiovascular dysfunction, and oxidative stress is a causative factor in the general aetiology of obesity and of skeletal and cardiac muscle pathology. Thus, this preclinical study aimed to define diaphragmatic and cardiac morphological and functional alterations in response to an obesogenic diet in rats and the therapeutic potential of an antioxidant supplement, N-acetylcysteine (NAC). Young male Wistar rats consumed ad libitum a 'lean' or high-saturated fat, high-sucrose (HFHS) diet for ∼22weeks and were randomized to control or NAC (2mg/ml in the drinking water) for the last 8 weeks of the dietary intervention. We then evaluated diaphragmatic and cardiac morphology and function. Neither HFHS diet nor NAC supplementation affected diaphragm-specific force, peak power or morphology. Right ventricular weight normalized to estimated body surface area, left ventricular fractional shortening and posterior wall maximal shortening velocity were higher in HFHS compared with lean control animals and not restored by NAC. In HFHS rats, the elevated deceleration rate of early transmitral diastolic velocity was prevented by NAC. Our data showed that the HFHS diet did not compromise diaphragmatic muscle morphology or in vitro function, suggesting other possible contributors to breathing abnormalities in obesity (e.g., abnormalities of neuromuscular transmission). However, the HFHS diet resulted in cardiac functional and morphological changes suggestive of hypercontractility and diastolic dysfunction. Supplementation with NAC did not affect diaphragm morphology or function but attenuated some of the cardiac abnormalities in the rats receiving the HFHS diet.

Effects of moderate aerobic exercise, low-level laser therapy, or their combination on muscles pathology, oxidative stress and irisin levels in the mdx mouse model of Duchenne muscular dystrophy.

This study aimed to investigate how the combined use of low-level laser therapy (LLLT) and exercise, to reduce the possible side effects and/or increase the benefits of exercise, would affect oxidative stress, utrophin, irisin peptide, and skeletal, diaphragmatic, and cardiac muscle pathologies. In our study, 20 mdx mice were divided into four groups. Groups; sedentary and placebo LLLT (SC), sedentary and LLLT (SL), 30-min swimming exercise (Ex), and 30-min swimming exercise and LLLT (ExL). After 8weeks of swimming exercise, muscle tests, biochemically; oxidative stress index (OSI), utrophin and irisin levels were measured. Skeletal, diaphragmatic and cardiac muscle histopathological scores, skeletal and cardiac muscle myocyte diameters were determined under the light and electron microscope. While only irisin levels were increased in group SL compared to SC, it was determined that OSI, heart muscle histopathological scores decreased and irisin levels increased in both exercise groups (p < 0.05). In addition, in the ExL group, an increase in rotarod and utrophin levels, and a decrease in muscle and diaphragm muscle histopathological scores were observed (p < 0.05). It was determined that the application of swimming exercise in the mdx mouse model increased the irisin level in the skeletal muscle, while reducing the OSI, degeneration in the heart muscle, inflammation and cardiopathy. When LLLT was applied in addition to exercise, muscle strength, skeletal muscle utrophin levels increased, and skeletal and diaphragmatic muscle degeneration and inflammation decreased. In addition, it was determined that only LLLT application increased the level of skeletal muscle irisin.

Pathological alterations in the gastrointestinal tract of a porcine model of DMD

BackgroundPatients with Duchenne muscular dystrophy (DMD) develop severe skeletal and cardiac muscle pathologies, which result in premature death. Therefore, the current therapeutic efforts are mainly targeted to correct dystrophin expression in skeletal muscle and heart. However, it was reported that DMD patients may also exhibit gastrointestinal and nutritional problems. How the pathological alterations in gastrointestinal tissues contribute to the disease are not fully explored.ResultsHere we employed the CRISPR/Cas9 system combined with somatic nuclear transfer technology (SCNT) to establish a porcine model of DMD and explored their pathological alterations. We found that genetic disruption of dystrophin expression led to morphological gastrointestinal tract alterations, weakened the gastrointestinal tract digestion and absorption capacity, and eventually led to malnutrition and gastric dysfunction in the DMD pigs.ConclusionsThis work provides important insights into the pathogenesis of DMD and highlights the need to consider the gastrointestinal dysfunction as an additional therapeutic target for DMD patients.

Evaluating Associations Between Nonclinical Cardiovascular Functional Endpoints and Repeat-dose Cardiovascular Toxicity in the Beagle Dog: A Cross-company Initiative.

Integrating nonclinical in vitro, in silico, and in vivo datasets holistically can improve hazard characterization and risk assessment. In pharmaceutical development, cardiovascular liabilities are a leading cause of compound attrition. Prior to clinical studies, functional cardiovascular data are generated in single-dose safety pharmacology telemetry studies, with structural pathology data obtained from repeat-dose toxicology studies with limited concurrent functional endpoints, eg, electrocardiogram via jacketed telemetry. Relationships between datasets remain largely undetermined. To address this gap, a cross-pharma collaboration collated functional and structural data from 135 compounds. Retrospective functional data were collected from good laboratory practice conscious dog safety pharmacology studies: effects defined as hemodynamic blood pressure or heart rate changes. Morphologic pathology findings (mainly degeneration, vacuolation, inflammation) from related toxicology studies in the dog (3-91 days repeat-dosing) were reviewed, harmonized, and location categorized: cardiac muscle (myocardium, epicardium, endocardium, unspecified), atrioventricular/aortic valves, blood vessels. The prevalence of cardiovascular histopathology changes was 11.1% of compounds, with 53% recording a functional blood pressure or heart rate change. Correlations were assessed using the Mantel-Haenszel Chi-square trend test, identifying statistically significant associations between cardiac muscle pathology and (1) decreased blood pressure, (2) increased heart rate, and between cardiovascular vessel pathology and increased heart rate. Negative predictive values were high, suggesting few compounds cause repeat-dose cardiovascular structural change in the absence of functional effects in single-dose safety pharmacology studies. Therefore, observed functional changes could prompt moving (sub)chronic toxicology studies forward, to identify cardiovascular liabilities earlier in development, and reduce late-stage attrition.

The expression of the rare caveolin-3 variant T78M alters cardiac ion channels function and membrane excitability.

AimsCaveolinopathies are a family of genetic disorders arising from alterations of the caveolin-3 (cav-3) gene. The T78M cav-3 variant has been associated with both skeletal and cardiac muscle pathologies but its functional contribution, especially to cardiac diseases, is still controversial. Here, we evaluated the effect of the T78M cav-3 variant on cardiac ion channel function and membrane excitability.Methods and resultsWe transfected either the wild type (WT) or T78M cav-3 in caveolin-1 knock-out mouse embryonic fibroblasts and found by immunofluorescence and electron microscopy that both are expressed at the plasma membrane and form caveolae. Two ion channels known to interact and co-immunoprecipitate with the cav-3, hKv1.5 and hHCN4, interact also with T78M cav-3 and reside in lipid rafts. Electrophysiological analysis showed that the T78M cav-3 causes hKv1.5 channels to activate and inactivate at more hyperpolarized potentials and the hHCN4 channels to activate at more depolarized potentials, in a dominant way. In spontaneously beating neonatal cardiomyocytes, the expression of the T78M cav-3 significantly increased action potential peak-to-peak variability without altering neither the mean rate nor the maximum diastolic potential. We also found that in a small cohort of patients with supraventricular arrhythmias, the T78M cav-3 variant is more frequent than in the general population. Finally, in silico analysis of both sinoatrial and atrial cell models confirmed that the T78M-dependent changes are compatible with a pro-arrhythmic effect.ConclusionThis study demonstrates that the T78M cav-3 induces complex modifications in ion channel function that ultimately alter membrane excitability. The presence of the T78M cav-3 can thus generate a susceptible substrate that, in concert with other structural alterations and/or genetic mutations, may become arrhythmogenic.

Local Aldosterone Synthesis in Skeletal Muscle

OBJECTIVETo characterize mineralocorticoid receptor (MR) regulation in normal vs. dystrophic skeletal muscle and elucidate the mechanism behind the efficacy of MR antagonists in dystrophic muscle.BACKGROUNDOur lab has recently shown MR is present in skeletal muscle fibers and represents a novel therapeutic target for treating both the skeletal and cardiac muscle pathologies of Duchenne muscular dystrophy (DMD). However, the underlying mechanisms and functional role of MR activation in skeletal muscle is still unclear. Excessive MR activation is known to contribute to the pathogenesis of heart failure, presumably due to increased levels of its natural ligand aldosterone. However, clinical trials have shown that addition of an MR antagonist to standard‐of‐care regimens (ACE inhibitors like lisinopril) improves morbidity and mortality in patients, even when circulating aldosterone levels are within the physiological range. There is now a growing body of evidence that shows aldosterone, which was previously thought to only be synthesized in the adrenal cortex can also be synthesized and metabolized locally in extra‐adrenal tissues, including the heart, particularly in pathological states.DESIGN/METHODSAldosterone synthase (CYP11B2) and other key enzymes in the aldosterone synthesis pathway were tested at the protein level in mouse skeletal muscles and myogenic cultures from normal and dystrophic models, and in normal human myogenic cultures using western blot analysis and immunofluorescence. Sequencing analysis of reverse transcribed PCR (RT‐PCR) of RNA from mouse skeletal muscle and human myotubes was used to confirm expression.RESULTSCYP11B2 is present in mouse skeletal muscle homogenates and up‐regulated in muscles from dystrophic mice (Figure 1). CYP11B2 does not appear to be coming from the skeletal muscle itself; immunofluorescence of dystrophic mouse muscles suggests this enzyme may be present in a subset of immune cells, which are present at much higher levels in dystrophic muscles (Figure 1). We have also found type 2 11‐beta hydroxysteroid dehydrogenase (11β‐HSD2), a key regulator of MR specificity, is present in normal human myotubes and is up‐regulated in dystrophic muscle (Figure 2).CONCLUSIONSCYP11B2 and 11β‐HSD2 levels are significantly increased in dystrophic muscle, suggesting MR activation is in excess of the physiological need. 11β‐HSD2 is expressed within the muscle fibers but CYP11B2 appears to be coming from a population of immune cells up‐regulated in dystrophic tissue due to increased inflammation and muscle degeneration.Support or Funding InformationNational Institutes of Health [R01 NS082868]

Genetic disruption of Ano5 in mice does not recapitulate human ANO5-deficient muscular dystrophy.

BackgroundAnoctamin 5 (ANO5) is a member of a conserved gene family (TMEM16), which codes for proteins predicted to have eight transmembrane domains and putative Ca2+-activated chloride channel (CaCC) activity. It was recently reported that mutations in this gene result in the development of limb girdle muscular dystrophy type 2L (LGMD2L), Miyoshi myopathy type 3 (MMD3), or gnathodiaphyseal dysplasia 1 (GDD1). Currently, there is a lack of animal models for the study of the physiological function of Ano5 and the disease pathology in its absence.ResultsHere, we report the generation and characterization of the first Ano5-knockout (KO) mice. Our data demonstrate that the KO mice did not present overt skeletal or cardiac muscle pathology at rest conditions from birth up to 18 months of age. There were no significant differences in force production or force deficit following repeated eccentric contractions between wild type (WT) and KO mice. Although cardiac hypertrophy developed similarly in both KO and WT mice after daily isoproterenol (ISO, 100 mg/kg) treatment via intraperitoneal injection for 2 weeks, they were functionally indiscernible. However, microarray analysis identified the genes involved in lipid metabolism, and complement pathways were altered in the KO skeletal muscle.ConclusionsTaken together, these data provide the evidence to show that genetic ablation of Ano5 in C57BL/6J mice does not cause overt pathology in skeletal and cardiac muscles, but Ano5 deficiency may lead to altered lipid metabolism and inflammation signaling.Electronic supplementary materialThe online version of this article (doi:10.1186/s13395-015-0069-z) contains supplementary material, which is available to authorized users.

Estimation of passive and active properties in the human heart using 3D tagged MRI.

Advances in medical imaging and image processing are paving the way for personalised cardiac biomechanical modelling. Models provide the capacity to relate kinematics to dynamics and—through patient-specific modelling—derived material parameters to underlying cardiac muscle pathologies. However, for clinical utility to be achieved, model-based analyses mandate robust model selection and parameterisation. In this paper, we introduce a patient-specific biomechanical model for the left ventricle aiming to balance model fidelity with parameter identifiability. Using non-invasive data and common clinical surrogates, we illustrate unique identifiability of passive and active parameters over the full cardiac cycle. Identifiability and accuracy of the estimates in the presence of controlled noise are verified with a number of in silico datasets. Unique parametrisation is then obtained for three datasets acquired in vivo. The model predictions show good agreement with the data extracted from the images providing a pipeline for personalised biomechanical analysis.

Mammalian target of rapamycin is essential for cardiomyocyte survival and heart development in mice

Mammalian target of rapamycin (mTOR) is a critical regulator of protein synthesis, cell proliferation and energy metabolism. As constitutive knockout of Mtor leads to embryonic lethality, the in vivo function of mTOR in perinatal development and postnatal growth of heart is not well defined. In this study, we established a muscle-specific mTOR conditional knockout mouse model (mTOR-mKO) by crossing MCK-Cre and Mtorflox/flox mice. Although the mTOR-mKO mice survived embryonic and perinatal development, they exhibited severe postnatal growth retardation, cardiac muscle pathology and premature death. At the cellular level, the cardiac muscle of mTOR-mKO mice had fewer cardiomyocytes due to apoptosis and necrosis, leading to dilated cardiomyopathy. At the molecular level, the cardiac muscle of mTOR-mKO mice expressed lower levels of fatty acid oxidation and glycolysis related genes compared to the WT littermates. In addition, the mTOR-mKO cardiac muscle had reduced Myh6 but elevated Myh7 expression, indicating cardiac muscle degeneration. Furthermore, deletion of Mtor dramatically decreased the phosphorylation of S6 and AKT, two key targets downstream of mTORC1 and mTORC2 mediating the normal function of mTOR. These results demonstrate that mTOR is essential for cardiomyocyte survival and cardiac muscle function.

THE STUDY OF APOPTOSIS MECHANISM IN THE PROCESS OF RECOMBINANT INTERLEUKIN-12 TREAT THE MICE WITH VIRAL MYOCARDITIS

ObjectivesThrough studying the NK cell activity, the pathological changes of myocardial cells and the changes of apoptosis in the process of recombinant interleukin -12 treat the mice with viral myocarditis,...

Abstract 16766: A Human Induced Pluripotent Stem Cell-Derived Engineered Cardiac Tissue Model of Pompe Disease

Background: Infantile-onset Pompe disease is a lethal autosomal recessive lysosomal storage disorder caused by the complete loss of acid α-glucosidase activity resulting in glycogen accumulation within lysosomes. Skeletal and cardiac muscle pathology develop due to aberrant glycogen metabolism and lysosomal dysfunction. This work presents the first in vitro human cardiac tissue model of Pompe disease documenting the classic Pompe cellular phenotype within a multicellular engineered cardiac tissue preparation. Methods: Pompe disease-specific human induced pluripotent stem (iPS) cell derived cardiomyocyte (iPS-CMs) were seeded into a polymerizing fibrin mixture to form mechanically integrated multicellular engineered cardiac tissue (ECT) constructs that were evaluated over a one-month period in parallel with healthy human iPS cell derived ECTs. Weekly measurements of isometric force and intracellular calcium transients were recorded under varying work load imposed by electrical pacing and β1 adrenergic stimulation. Structural assessment was performed using electron microscopy and immunohistochemistry. Results: Healthy and Pompe iPS-CMs can form cylindrically shaped ECTs of 1-2 mm diameter and 1.5-2 cm in length composed of coupled CMs that generate force in the milli-newton range along the cylindrical axis. We report structural changes in the ECT model consistent with the hallmarks of Pompe disease including progressive intracellular glycogen accumulation, lysosomal disruption, and myofibrillar disarray. Both healthy and Pompe ECTs generate higher twitch forces in response to mechanical stretch, have a negative force-frequency relationship characteristic of immature myocardium, and have an inotropic response to dobutamine stimulation. Conclusion: Human iPS-CM ECTs obey the Frank-Starling law and produce calcium cycling and force kinetics that respond to β1 adrenergic stimulation. The Pompe ECT provides a novel cardiac tool in which to further study the pathophysiology of this disease and test novel therapeutic approaches.

Calibrated quantitative ultrasound imaging of skeletal muscle using backscatter analysis

We evaluated the ability of an ultrasound method, which can characterize cardiac muscle pathology and has reliability across different imaging systems, to obtain calibrated quantitative estimates of backscatter of skeletal muscle. Our procedure utilized a tissue-mimicking phantom to establish a linear relationship between ultrasound grayscale and backscatter levels. We studied skeletal muscles of 82 adults: 45 controls and 37 patients with hereditary myopathies. We found that skeletal muscle ultrasound backscatter levels varied with probe orientation, age, and muscle contraction and pathology. Reliability was greater with the probe in longitudinal compared with transverse planes. Backscatter levels were higher in those >40 years of age, in muscle extension than flexion, and in myopathic patients than controls. Calibrated measurements of muscle backscatter have sensitivity and specificity in identifying and reliably measuring levels of skeletal muscle pathology.

Structural Heart Disease, SCN5A Gene Mutations, and Brugada Syndrome

The report of the Second Consensus Conference, published in Circulation in 2005, defined the Brugada syndrome as ST-segment elevation in the right precordial ECG leads (so-called type 1 ECG) and a high incidence of sudden death in patients with structurally normal hearts.1 An autosomal dominant disease with incomplete penetrance, Brugada syndrome has been linked to mutations in SCN5A , the gene encoding the alpha subunit of the cardiac sodium channel.2 More than 80 mutations in SCN5A have been linked to this syndrome (references cited in Reference 1). Analysis of several of these mutations has consistently demonstrated a loss of function related to multiple mechanisms, including failure of sodium channel protein expression and changes in the voltage and time dependence of sodium channel current activation, inactivation, or reactivation.1 Still, SCN5A mutations have been reported in only &20% of patients with Brugada syndrome diagnosed on the basis of clinical criteria, suggesting that other genetic defects and/or other disease mechanisms may give rise to this clinical picture. To complicate matters further, SCN5A mutations have also been identified in patients with the long-QT syndrome. These mutations generally lead to a “gain of function” in the sodium channel, which prolongs the QT interval by increasing inward current. In fact, at least 3 human diseases have been linked to defects in this gene: Brugada syndrome, long-QT syndrome, and progressive conduction disturbances.2–4 Furthermore, there is considerable overlap of clinical profiles, so some patients with Brugada syndrome also have atrial fibrillation, conduction defects with sinus node abnormalities, or prolonged QT interval (reviewed in Reference 1). Thus, genotype-phenotype relationships in Brugada syndrome are highly complex and serve to underscore our incomplete knowledge of the pathogenesis of this type of inherited arrhythmogenic disease. Article p 3680 A similar area of increasing complexity and uncertainty has to …

Cardiac involvement in muscular dystrophies: Molecular mechanisms

In this review, we draw attention to the multiple mechanisms responsible for the pathogenesis of cardiomyopathies in patients with muscular dystrophies. More than one single mechanism is likely to be involved in the development of skeletal and cardiac muscle pathology even when there is a single protein defect. The best example is dystrophin deficiency, in which increased sarcolemmal permeability following eccentric exercise, reduced force generation, and abnormal signaling are all likely to contribute to the progressive muscle damage observed. In other conditions, such as the sarcoglycanopathies, a protein deficiency both in the striated cardiomyocte and the vascular smooth muscle appears to play a significant role. An entirely different mechanism of disease is likely in defects of nuclear envelope proteins, although the precise pathogenesis of this group of conditions is still not clear. Differences between the organization of skeletal and cardiac muscle protein complex are also only starting to emerge and will very likely be the focus of future research.

Toward a Molecular Understanding of the Structure–Function of Ryanodine Receptor Ca&lt;SUP&gt;2+&lt;/SUP&gt; Release Channels: Perspectives From Recombinant Expression Systems

Identification of the genetic basis of human diseases linked to dysfunctional free calcium (Ca2+) signaling has triggered an explosion of interest in the functional characterization of the molecular components regulating intracellular Ca2+ homeostasis. There is a growing appreciation of the central role of intracellular ryanodine-sensitive Ca2+ release channel (RyR) regulation in skeletal and cardiac muscle pathologies, including malignant hyperthermia, heart failure, and sudden cardiac death. The use of cloned RyR isoforms and recombinant expression techniques has greatly facilitated the elucidation of the molecular basis of RyR Ca2+ release functionality. This review will focus on the recombinant techniques used in the functional characterization of recombinant RyR isoforms and the insights that these approaches have yielded in unraveling the mechanistic basis of RyR channel functionality.

Prevention of cardiomyopathy in mouse models lacking the smooth muscle sarcoglycan-sarcospan complex.

Cardiomyopathy is a multifactorial disease, and the dystrophin-glycoprotein complex has been implicated in the pathogenesis of both hereditary and acquired forms of the disease. Using mouse models of cardiomyopathy made by ablating genes for components of the sarcoglycan complex, we show that long-term treatment with verapamil, a calcium channel blocker with vasodilator properties, can alleviate the severe cardiomyopathic phenotype, restoring normal serum levels for cardiac troponin I and normal cardiac muscle morphology. Interruption of verapamil treatment leads again to vascular dysfunction and acute myocardial necrosis, indicating that predilection for cardiomyopathy is a continuing process. In contrast, verapamil did not prevent cardiac muscle pathology in dystrophin-deficient mdx mice, which neither show a disruption of the sarcoglycan complex in vascular smooth muscle nor vascular dysfunction. Hence, our data strongly suggest that pharmacological intervention with verapamil merits investigation as a potential therapeutic option not only for patients with sarcoglycan mutations, but also for patients with idiopathic cardiomyopathy associated with myocardial ischemia not related to atherosclerotic coronary artery disease.

Metabolic shifts and myocyte hypertrophy in deflazacort treatment ofmdx mouse cardiomyopathy

We tested the hypothesis that treatment of mdx mouse muscular dystrophy with the glucocorticoid deflazacort prevents cardiomyopathic lesions and is accompanied by changes in metabolism and gene expression that reflect the improved tissue integrity. Cardiac muscle pathology, expression of alpha-cardiac myosin heavy chain, DNA synthesis, laminin, and basic fibroblast growth factor (bFGF) were examined to characterize dystrophy and changes with treatment. The potential of proton magnetic resonance spectroscopy (H-NMRS) to track cardiac dystrophy and deflazacort effects was also studied. Deflazacort (but not equipotent prednisone) reproducibly decreased lesion prevalence and severity. Treatment also produced cardiomyocyte hypertrophy and a 5.4-fold increase in alpha-cardiac myosin content. Expression of bFGF messenger RNA (mRNA), notable around lesions, rose 3.3-fold, and laminin expression rose 2.1-fold after deflazacort. Studies using H-NMRS showed a cardiac "signature" with less glycine and taurine than limb muscle or diaphragm and shifts with progression of dystrophy (distinct from normal aging) in many metabolites. Increased taurine, acetate, and succinate were present after 2 weeks of deflazacort treatment but were not present after 4 weeks. Although paired kinetic and functional studies of myocardium will be needed to determine the origin of such changes, these results demonstrate the potential application of H-NMRS to monitor clinical heart disease and treatment. In addition, the metabolic effects of deflazacort were substantial in preventing the progression of cardiomyopathy in mdx mice and included increased expression of protectant and stabilizing factors and hypertrophy of cardiac myocytes.

The CHORUS (Cerivastatin in Heart Outcomes in Renal Disease: Understanding Survival) protocol: A double-blind, placebo-controlled trial in patients with ESRD

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin)–mediated lowering of serum cholesterol has been associated with a significant reduction in cardiovascular morbidity and mortality. Recent studies suggest that additional non–lipid lowering effects (eg, endothelial stabilization, anti-inflammatory, antithrombogenic) may be important in modulating their effectiveness. Dyslipidemia is common in end-stage renal disease (ESRD), and hemodialysis patients have increased cardiovascular morbidity and mortality. Cerivastatin, a new statin with powerful low-density lipoprotein–cholesterol (LDL-C) lowering capabilities, possesses some unique non-LDL-C–mediated properties that may contribute to a reduction of coronary events in the patient with ESRD. The primary objective of this multicenter multinational study of 1,054 hemodialysis patients is to compare 2 years of treatment with cerivastatin (0.4 mg/d) versus placebo on the composite clinical event rate of myocardial infarction, sudden cardiac death, ischemic stroke, and the need for coronary arterial bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) procedures in these patients. Changes in lipids, inflammatory proteins including heat stable C-reactive protein (hsCRP), interleukin-6 (IL-6), oncostatin-M, intracellular adhesion molecule-1 (ICAM-1) and monocyte-chemoattractant protein-1 (MCP-1), as well as markers of cardiac muscle pathology, such as troponin I and troponin T, will be assessed in a subset of patients. This study is the first of its kind to assess the effect of a statin on the reduction of cardiovascular morbidity and mortality in an incident hemodialysis population. It will determine whether treatment with cerivastatin can effectively reduce the significant cardiovascular morbidity and mortality.

Molecular basis of muscular dystrophies

Muscular dystrophies represent a heterogeneous group of disorders, which have been largely classified by clinical phenotype. In the last 10 years, identification of novel skeletal muscle genes including extracellular matrix, sarcolemmal, cytoskeletal, cytosolic, and nuclear membrane proteins has changed the phenotype-based classification and shed new light on the molecular pathogenesis of these disorders. A large number of genes involved in muscular dystrophy encode components of the dystrophin-glycoprotein complex (DGC) which normally links the intracellular cytoskeleton to the extracellular matrix. Mutations in components of this complex are thought to lead to loss of sarcolemmal integrity and render muscle fibers more susceptible to damage. Recent evidence suggests the involvement of vascular smooth muscle DGC in skeletal and cardiac muscle pathology in some forms of sarcoglycan-deficient limb-girdle muscular dystrophy. Intriguingly, two other forms of limb-girdle muscular dystrophy are possibly caused by perturbation of sarcolemma repair mechanisms. The complete clarification of these various pathways will lead to further insights into the pathogenesis of this heterogeneous group of muscle disorders. © 2000 John Wiley & Sons, Inc. Muscle Nerve 23: 1456–1471, 2000