Proximal weakness and creatine kinase elevation in systemic sclerosis: Clinical correlates, prognosis and functional implications

OBJECTIVES

To determine the frequency, clinical correlates and implications of clinical evidence of muscle disease in systemic sclerosis (SSc).

METHODS

Australian Scleroderma Cohort Study participants with ≥1 creatine kinase (CK) and proximal power assessment were subdivided according to presence of proximal weakness (PW: proximal muscle power<5/5) and CK elevation(≥140IU/L). Participants were assigned to one of four groups: concurrent PW&CK elevation, PW alone, CK elevation alone or neither. Between-group comparisons were made with chi-squared, ANOVA or Kruskal-Wallis tests. Survival analysis was performed using time-varying-covariate Cox regression modelling. Longitudinal data were modelled using multinomial logistic and linear regression.

RESULTS

Of 1786 participants, 4 % had concurrent PW&CK elevation, 15 % PW alone, 24 % CK elevation and 57 % neither. Participants with PW&CK elevation displayed a severe, inflammatory SSc phenotype, with more frequent dcSSc(p < 0.01), tendon friction rubs(p < 0.01), synovitis(p < 0.01) and digital ulceration(p = 0.03). Multimorbidity(p < 0.01) and cardiopulmonary disease, including ischaemic heart disease(p < 0.01) and pulmonary arterial hypertension(p < 0.01), were most common in those with PW, with and without CK elevation. Men with anti-Scl70 positivity most frequently had CK elevation alone, without other significant clinical differences. Multivariable modelling demonstrated 3.6-fold increased mortality in those with PW&CK elevation (95 %CI 1.9-6.6, p < 0.01) and 2.1-fold increased mortality in PW alone (95 %CI 1.4-3.0, p < 0.01) compared to those without PW or CK elevation. CK elevation alone conferred better survival (HR 0.7, 95 %CI 0.4-1.1, p = 0.09) compared to those with no PW or CK elevation. PW regardless of CK elevation was associated with impaired physical function, with reduced six-minute-walk-distance (p < 0.01), higher HAQ-DI scores (p < 0.01) and increased patient-reported dyspnoea (p = 0.04).

CONCLUSION

Clinical features of myopathy are highly prevalent in SSc, affecting almost half of our study cohort. Detection of PW and elevated CK alone, even without imaging or histopathological identification of SSc-myopathy, identified important clinical associations and are associated with poorer function and overall prognosis.

Neutral lipid storage disease with myopathy: clinicopathological and genetic features of nine Iranian patients

The rare disorder known as Neutral Lipid Storage Disease with Myopathy presents with a variety of clinical manifestations, including myopathy, cardiac dysfunction, and other organ complications. Early diagnosis is crucial due to the increased risk of cardiomyopathy. We describe the clinical, histopathological, muscle imaging, and genetic findings of nine neutral lipid storage myopathy patients. Proximal weakness and asymmetric involvement may suggest lipid storage myopathy. While skeletal muscle weakness was the main manifestation in our patients, one case presented only with hyperCKemia. Additionally, three patients had fertility issues, two suffered from diabetes mellitus, two had cardiomyopathy, and one had a history of hypothyroidism. Muscle histopathology revealed lipid depositions and rimmed vacuoles, prompting peripheral blood smears to detect Jordan Anomalies. All muscle biopsies and peripheral blood smear showed lipid droplets, rimmed vacuoles, and Jordan anomaly. Identifying PNPLA2 gene mutations is important for diagnosing neutral lipid storage myopathy; our cases showed some novel mutations. This study highlights the importance of early diagnosis and comprehensive evaluation in managing neutral lipid storage myopathy cases.

Melatonin: A potential adjuvant therapy for septic myopathy

Septic myopathy, also known as ICU acquired weakness (ICU-AW), is a characteristic clinical symptom of patients with sepsis, mainly manifested as skeletal muscle weakness and muscular atrophy, which affects the respiratory and motor systems of patients, reduces the quality of life, and even threatens the survival of patients. Melatonin is one of the hormones secreted by the pineal gland. Previous studies have found that melatonin has anti-inflammatory, free radical scavenging, antioxidant stress, autophagic lysosome regulation, mitochondrial protection, and other multiple biological functions and plays a protective role in sepsis-related multiple organ dysfunction. Given the results of previous studies, we believe that melatonin may play an excellent regulatory role in the repair and regeneration of skeletal muscle atrophy in septic myopathy. Melatonin, as an over-the-counter drug, has the potential to be an early, complementary treatment for clinical trials. Based on previous research results, this article aims to critically discuss and review the effects of melatonin on sepsis and skeletal muscle depletion.

Skeletal muscle abnormalities in heart failure with preserved ejection fraction

Almost half of all heart failure (HF) disease burden is due to HF with preserved ejection fraction (HFpEF). The primary symptom in patients with HFpEF, even when well compensated, is severe exercise intolerance and is associated with their reduced quality of life. Recently, studies showed that HFpEF patients have multiple skeletal muscle (SM) abnormalities, and these are associated with decreased exercise intolerance. The SM abnormalities are likely intrinsic to the HFpEF syndrome, not a secondary consequence of an epiphenomenon. These abnormalities are decreased muscle mass, reduced type I (oxidative) muscle fibers, and reduced type I-to-type II fiber ratio as well as a reduced capillary-to-fiber ratio, abnormal fat infiltration into the thigh SM, increased levels of atrophy genes and proteins, reduction in mitochondrial content, and rapid depletion of high-energy phosphate during exercise with markedly delayed repletion of high-energy phosphate during recovery in mitochondria. In addition, patients with HFpEF have impaired nitric oxide bioavailability, particularly in the microvasculature. These SM abnormalities may be responsible for impaired diffusive oxygen transport and/or impaired SM oxygen extraction. To date, exercise training (ET) and caloric restriction are some of the interventions shown to improve outcomes in HFpEF patients. Improvements in exercise tolerance following aerobic ET are largely mediated through peripheral SM adaptations with minimal change in central hemodynamics and highlight the importance of targeting SM to improve exercise intolerance in HFpEF. Focusing on the abnormalities mentioned above may improve the clinical condition of patients with HFpEF.

Revisiting skeletal myopathy and exercise training in heart failure: Emerging role of myokines

Exercise intolerance remains a major unmet medical need in patients with heart failure (HF). Skeletal myopathy is currently considered as the major limiting factor for exercise capacity in HF patients. On the other hand, emerging evidence suggest that physical exercise can decrease morbidity and mortality in HF patients. Therefore, mechanistic insights into skeletal myopathy may uncover critical aspects for therapeutic interventions to improve exercise performance in HF. Emerging data reviewed in this article suggest that the assessment of circulating myokines (molecules synthesized and secreted by skeletal muscle in response to contraction that display autocrine, paracrine and endocrine actions) may provide new insights into the pathophysiology, phenotyping and prognostic stratification of HF-related skeletal myopathy. Further studies are required to determine whether myokines may also serve as biomarkers to personalize the modality and dose of physical training prescribed for patients with HF and exercise intolerance. In addition, the production and secretion of myokines in patients with HF may interact with systemic alterations (e.g., inflammation and metabolic disturbances), frequently present in patients with HF. Furthermore, myokines may exert beneficial or detrimental effects on cardiac structure and function, which may influence adverse cardiac remodelling and clinical outcomes in HF patients. Collectively, these data suggest that a deeper knowledge on myokines regulation and actions may lead to the identification of novel physical exercise-based therapeutic approaches for HF patients.

Mutation in RyR2-FKBP Binding site alters Ca2+ signaling modestly but increases "arrhythmogenesis" in human stem cells derived cardiomyocytes

AIMS

To gain insights into FKBP regulation of cardiac ryanodine receptor (RyR2) and Ca²⁺ signaling, we introduced the point mutation (N771D-RyR2) corresponding to skeletal muscle mutation (N760D-RyR1) associated with central core disease (CCD) via CRISPR/Cas9 gene-editing in the RyR2 FKBP binding site expressed in human induced pluripotent stem cell-derived cardiomyocytes (hiPSCCMs). Patients inflicted with CCD and other hereditary skeletal muscle diseases often show higher incidence of atrial or ventricular arrhythmias.

METHODS AND RESULTS

Ca²⁺ imaging of voltage-clamped N771D-RyR2 mutant compared to WT hiPSCCMs showed: (1) ∼30% suppressed I_Ca with no significant changes in the gating kinetics of I_Ca; (2) 29% lower SR Ca²⁺ content and 33% lower RyR2 Ca²⁺ leak; (3) higher CICR gain and 30-35% increased efficiency of I_Ca-triggered Ca^2±release; (4) higher incidence of aberrant SR Ca²⁺ releases, DADs, and Ca²⁺ sparks; (5) no change in fractional Ca²⁺-release, action potential morphology, sensitivity to isoproterenol, and sarcomeric FKBP-binding pattern.

CONCLUSIONS

The more frequent spontaneous Ca²⁺ releases and longer Ca²⁺ sparks underlie the increased incidence of DADs and cellular arrhythmogenesis of N771D-RyR2 mutant. The smaller RyR2 Ca^2±leak and SR content result from suppressed I_Cathat is compensated by higher CICR gain.

Poor Myocardial Compaction in a Patient with Recessive MYL2 Myopathy

Recessive mutations in the Myosin regulatory light chain 2 (MYL2) gene are the cause of an infantile-onset myopathy, associated with fatal myocardial disease of variable macromorphology. We here present the first Japanese family affected with recessive MYL2 myopathy. Affected siblings manifested typical features and the proband's autopsy findings were compatible with the diagnosis of noncompaction cardiomyopathy. The rapidly progressive clinical course of this recessive MYL2 cardiomyopathy highlights the crucial role of c-terminal tails in MYL2 protein in maintaining cardiac morphology and function.

Desmin mutations result in mitochondrial dysfunction regardless of their aggregation properties

Desmin, being a major intermediate filament of muscle cells, contributes to stabilization and positioning of mitochondria. Desmin mutations have been reported in conjunction with skeletal myopathies accompanied by mitochondrial dysfunction. Depending on the ability to promote intracellular aggregates formation, mutations can be considered aggregate-prone or non-aggregate-prone. The aim of the present study was to describe how expression of different desmin mutant isoforms effects mitochondria and contributes to the development of myocyte dysfunction. To achieve this goal, two non-aggregate-prone (Des S12F and Des A213V) and four aggregate-prone (Des L345P, Des A357P, Des L370P, Des D399Y) desmin mutations were expressed in skeletal muscle cells. We showed that all evaluated mutations affected the morphology of mitochondrial network, suppressed parameters of mitochondrial respiration, diminished mitochondrial membrane potential, increased ADP/ATP ratio, and enhanced mitochondrial DNA (mtDNA) release. mtDNA was partially secreted through exosomes as demonstrated by GW4869 treatment. Dysfunction of mitochondria was observed regardless the type of mutation: aggregate-prone or non-aggregate-prone. However, expression of aggregate-prone mutations resulted in more prominent phenotype. Thus, in this comparative study of six pathogenic desmin mutations that cause skeletal myopathy development, we confirmed a role of mitochondrial dysfunction and mtDNA release in the pathogenesis of desmin myopathies, regardless of the aggregation capacity of the mutated desmin.

Effects of aerobic and inspiratory training on skeletal muscle microRNA-1 and downstream-associated pathways in patients with heart failure

BACKGROUND

The exercise intolerance in chronic heart failure with reduced ejection fraction (HFrEF) is mostly attributed to alterations in skeletal muscle. However, the mechanisms underlying the skeletal myopathy in patients with HFrEF are not completely understood. We hypothesized that (i) aerobic exercise training (AET) and inspiratory muscle training (IMT) would change skeletal muscle microRNA-1 expression and downstream-associated pathways in patients with HFrEF and (ii) AET and IMT would increase leg blood flow (LBF), functional capacity, and quality of life in these patients.

METHODS

Patients age 35 to 70 years, left ventricular ejection fraction (LVEF) ≤40%, New York Heart Association functional classes II-III, were randomized into control, IMT, and AET groups. Skeletal muscle changes were examined by vastus lateralis biopsy. LBF was measured by venous occlusion plethysmography, functional capacity by cardiopulmonary exercise test, and quality of life by Minnesota Living with Heart Failure Questionnaire. All patients were evaluated at baseline and after 4 months.

RESULTS

Thirty-three patients finished the study protocol: control (n = 10; LVEF = 25 ± 1%; six males), IMT (n = 11; LVEF = 31 ± 2%; three males), and AET (n = 12; LVEF = 26 ± 2%; seven males). AET, but not IMT, increased the expression of microRNA-1 (P = 0.02; percent changes = 53 ± 17%), decreased the expression of PTEN (P = 0.003; percent changes = -15 ± 0.03%), and tended to increase the p-AKT^ser473 /AKT ratio (P = 0.06). In addition, AET decreased HDAC4 expression (P = 0.03; percent changes = -40 ± 19%) and upregulated follistatin (P = 0.01; percent changes = 174 ± 58%), MEF2C (P = 0.05; percent changes = 34 ± 15%), and MyoD expression (P = 0.05; percent changes = 47 ± 18%). AET also increased muscle cross-sectional area (P = 0.01). AET and IMT increased LBF, functional capacity, and quality of life. Further analyses showed a significant correlation between percent changes in microRNA-1 and percent changes in follistatin mRNA (P = 0.001, rho = 0.58) and between percent changes in follistatin mRNA and percent changes in peak VO₂ (P = 0.004, rho = 0.51).

CONCLUSIONS

AET upregulates microRNA-1 levels and decreases the protein expression of PTEN, which reduces the inhibitory action on the PI3K-AKT pathway that regulates the skeletal muscle tropism. The increased levels of microRNA-1 also decreased HDAC4 and increased MEF2c, MyoD, and follistatin expression, improving skeletal muscle regeneration. These changes associated with the increase in muscle cross-sectional area and LBF contribute to the attenuation in skeletal myopathy, and the improvement in functional capacity and quality of life in patients with HFrEF. IMT caused no changes in microRNA-1 and in the downstream-associated pathway. The increased functional capacity provoked by IMT seems to be associated with amelioration in the respiratory function instead of changes in skeletal muscle. ClinicalTrials.gov (Identifier: NCT01747395).

Neutral lipid storage disease with myopathy in China: a large multicentric cohort study

Background

Neutral lipid storage disease with myopathy (NLSDM) is a rare clinical heterogeneous disorder caused by mutations in the patatin-like phospholipase domain-containing 2 (PNPLA2) gene. NLSDM usually presents skeletal myopathy, cardiomyopathy and the multiple organs dysfunction. Around 50 cases of NLSDM have been described worldwide, whereas the comprehensive understanding of this disease are still limited. We therefore recruit NLSDM patients from 10 centers across China, summarize the clinical, muscle imaging, pathological and genetic features, and analyze the genotype-phenotype relationship.

Results

A total of 45 NLSDM patients (18 men and 27 women) were recruited from 40 unrelated families. Thirteen patients were born from consanguineous parents. The phenotypes were classified as asymptomatic hyperCKemia (2/45), pure skeletal myopathy (18/45), pure cardiomyopathy (4/45), and the combination of skeletal myopathy and cardiomyopathy (21/45). Right upper limb weakness was the early and prominent feature in 61.5% of patients. On muscle MRI, the long head of the biceps femoris, semimembranosus and adductor magnus on thighs, the soleus and medial head of the gastrocnemius on lower legs showed the most severe fatty infiltration. Thirty-three families were carrying homozygous mutations, while seven families were carrying compound heterozygous mutations. A total of 23 mutations were identified including 11 (47.8%) point mutations, eight (34.8%) deletions and four (17.4%) insertions. c.757 + 1G > T, c.245G > A and c.187 + 1G > A were the three most frequent mutations. Among four groups of phenotypes, significant differences were shown in disease onset (< 20 years versus ≥20 years old, p = 0.003) and muscle pathology (with rimmed vacuoles versus without rimmed vacuoles, p = 0.001). PNPLA2 mutational type or functional defects did not show great impact on phenotypes.

Conclusion

We outline the clinical and genetic spectrum in a large cohort of NLSDM patients. Selective muscle fatty infiltration on posterior compartment of legs are characteristic of NLSDM. Chinese patients present with distinctive and relative hotspot PNPLA2 mutations. The disease onset age and pathological appearance of rimmed vacuoles are proved to be related with the clinical manifestations. The phenotypes are not strongly influenced by genetic defects, suggesting the multiple environmental risk factors in the development of NLSDM.

Dilated cardiomyopathy-mediated heart failure induces a unique skeletal muscle myopathy with inflammation

Background

Skeletal muscle myopathy and exercise intolerance are diagnostic hallmarks of heart failure (HF). However, the molecular adaptations of skeletal muscles during dilated cardiomyopathy (DCM)-mediated HF are not completely understood.

Methods

Skeletal muscle structure and function were compared in wild-type (WT) and cardiac myosin binding protein-C null mice (t/t), which develop DCM-induced HF. Cardiac function was examined by echocardiography. Exercise tolerance was measured using a graded maximum treadmill running test. Hindlimb muscle function was assessed in vivo from measurements of plantar flexor strength. Inflammatory status was evaluated from the expression of inflammatory markers and the presence of specific immune cell types in gastrocnemius muscles. Muscle regenerative capacityat days 3, 7, and 14 after eccentric contraction-induced injury was determined from the number of phenotypically new and adult fibers in the gastrocnemius, and functional recovery of plantar flexion torque.

Results

t/t mice developed DCM-induced HF in association with profound exercise intolerance, consistent with previous reports. Compared to WT, t/t mouse hearts show significant hypertrophy of the atria and ventricles and reduced fractional shortening, both systolic and diastolic. In parallel, the skeletal muscles of t/t mice exhibit weakness and myopathy. Compared to WT, plantar flexor muscles of t/t null mice produce less peak isometric plantar torque (Po), develop torque more slowly (+ dF/dt), and relax more slowly (− dF/dt, longer half-relaxation times,1/2RT). Gastrocnemius muscles of t/t mice have a greater number of fibers with smaller diameters and central nuclei. Oxidative fibers, both type I and type IIa, show significantly smaller cross-sectional areas and more central nuclei. These fiber phenotypes suggest ongoing repair and regeneration under homeostatic conditions. In addition, the ability of muscles to recover and regenerate after acute injury is impaired in t/t mice.

Conclusions

Our studies concluded that DCM-induced HF induces a unique skeletal myopathy characterized by decreased muscle strength, atrophy of oxidative fiber types, ongoing inflammation and damage under homeostasis, and impaired regeneration after acute muscle injury. Furthermore, this unique myopathy in DCM-induced HF likely contributes to and exacerbates exercise intolerance. Therefore, efforts to develop therapeutic interventions to treat skeletal myopathy during DCM-induced HF should be considered.

Electronic supplementary material

The online version of this article (10.1186/s13395-019-0189-y) contains supplementary material, which is available to authorized users.

Clinical Manifestations and Overall Management Strategies for Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder that causes progressive weakness and wasting of skeletal muscular and myocardium in boys due to mutation of dystrophin. The structural integrity of each individual skeletal and cardiac myocyte is significantly compromised upon physical stress due to the absence of dystrophin. The progressive destruction of systemic musculature and myocardium causes affected patients to develop multiple organ disabilities, including loss of ambulation, physical immobility, neuromuscular scoliosis, joint contracture, restrictive lung disease, obstructive sleep apnea, and cardiomyopathy. There are some central nervous system-related medical problems, as dystrophin is also expressed in the neuronal tissues. Although principal management is to mainly delay the pathological process, an enhanced understanding of underlying pathological processes has significantly improved quality of life and longevity for DMD patients. Future research in novel molecular approach is warranted to answer unanswered questions.

Smad4 SUMOylation is essential for memory formation through upregulation of the skeletal myopathy gene TPM2

Background

Smad4 is a critical effector of TGF-β signaling that regulates a variety of cellular functions. However, its role in the brain has rarely been studied. Here, we examined the molecular mechanisms underlying the post-translational regulation of Smad4 function by SUMOylation, and its role in spatial memory formation.

Results

In the hippocampus, Smad4 is SUMOylated by the E3 ligase PIAS1 at Lys-113 and Lys-159. Both spatial training and NMDA injection enhanced Smad4 SUMOylation. Inhibition of Smad4 SUMOylation impaired spatial learning and memory in rats by downregulating TPM2, a gene associated with skeletal myopathies. Similarly, knockdown of TPM2 expression impaired spatial learning and memory, while TPM2 mRNA and protein expression increased after spatial training. Among the TPM2 mutations associated with skeletal myopathies, the TPM2E122K mutation was found to reduce TPM2 expression and impair spatial learning and memory in rats.

Conclusions

We have identified a novel role of Smad4 SUMOylation and TPM2 in learning and memory formation. These results suggest that patients with skeletal myopathies who carry the TPM2E122K mutation may also have deficits in learning and memory functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12915-017-0452-9) contains supplementary material, which is available to authorized users.

Skeletal myopathy in a family with lamin A/C cardiac disease

BACKGROUND

The objective of this study was to evaluate patients with known hereditary cardiac conduction and myocardial disease (HCCMD) caused by a lamin A/C gene mutation for skeletal muscle involvement using magnetic resonance imaging (MRI) computed tomography (CT).

METHODS

Twenty-one patients with the diagnosis of HCCMD were available for study. Of these 21, 11 had MRI scans of the lower legs. The 11 that had an MRI were compared to a control group of 17 healthy controls. In ten patients in whom MRI was contraindicated, CT was used for lower leg imaging and the gastrocnemius muscle was compared to an unaffected muscle.

RESULTS

In patients with severe cardiac involvement defined as conduction system disease requiring pacemaker implant and CT instead of MRI, there was a significant difference in the composition of the unaffected muscle versus the gastrocnemius muscle, P<0.05. In the patients who underwent MRI, there was no statistical significance between the normal population and the study population. However, many study patients' images showed dramatic changes in the gastrocnemius muscle where there was definite replacement of muscle tissue by fibrofatty tissue.

CONCLUSIONS

Our results showed that patients with HCCMD can also present with skeletal muscle problems. The degree of skeletal muscle involvement is greater in HCCMD patients requiring implantable cardiac devices.

Familial restrictive cardiomyopathy with atrioventricular block without skeletal myopathy

Familial restrictive cardiomyopathy is an autosomal dominant cardiomyopathy histologically characterized by myocyte hypertrophy and interstitial fibrosis. The case of a 54-year-old man diagnosed with restrictive cardiomyopathy is reported. The patient had been implanted with a two-chambered pacemaker for a complete atrioventricular block 12 years before. The family history was positive with several affected members, none of whom had findings of skeletal myopathy. Genetic analysis of the index patient revealed no troponin I mutations.