Abstract 279: A Deletion In The N2A Region Of Titin Carried By Muscular Dystrophy With Myositis (mdm) Mice Severely Affects Skeletal Muscle, But Not The Heart

20% of dilated cardiomyopathy patients carry mutations in the giant protein titin. Mutations are predominant in A band but also occur in I band, a domain that regulates passive tension and myocyte signaling. A recessive mouse mutation in titin I band N2A region (mdm) causes early onset muscular dystrophy with myositis and death. We assessed cardiac morphology, function, and transcriptional profiles (RNAseq) in mdm mice. Young homozygous mdm mice (n>6) have reduced body weight (7gms) vs. heterozygous (20gm) or WT (17gm) littermates, with severe skeletal muscle dystrophy. Four-week old homozygous mdm mice have higher left ventricular (LV): body weight ratios. Echocardiography revealed thinner LV posterior wall and septum (LVPWd and IVSd) and normal LV diameter (LVDd); when normalized for body weight, cardiac dimensions were increased compared to WT or heterozygous mdm mice. Fractional shortening was reduced in homozygous Mdm mice (35%) vs. WT (40-41%, p<0.01); histology showed neither overt pathology nor fibrosis. Titin gels showed lack of difference in cardiac titin isoform pattern, consistent with RNAseq, which showed the mdm titin transcript excluded exons 107 and 108, deleting in frame 48 amino acids. 240 transcripts (0.8%) were differentially expressed (fold change >1.5 and <0.75, p<0.001) in homozygous vs. heterozygous mdm hearts; ANP and BNP were mildly upregulated (2- and 1.2-fold). Altered transcripts participated in extracellular and immune signaling pathways. Among titin binding partners, only calpain-3 that interacts with N2A was changed (0.6-fold), consistent with previous reports in skeletal muscle. As humans have heterozygous mutations, we stressed adult heterozygous mdm and WT mice (2 weeks of angiotensin II infusion): both had comparable hypertrophic responses (increased LVPWd and IVSd). Aged (89 week old) unstressed heterozygous mdm mice had normal cardiac dimensions and function. The N2A region, I-band titin mdm mutation causes minimal cardiac dysfunction in mice, unlike the severe skeletal muscle phenotype. Human I-band mutations are unlikely to cause dilated cardiomyopathy.

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Chloroquine Decreases Cardiomyocyte Autophagy and Improves Cardiac Function in a Mouse Model of Duchenne Muscular Dystrophy

10.21203/rs.3.rs-149383/v1 ◽

2021 ◽

Author(s):

Takaya Hirata ◽

Shiro Baba ◽

Kentaro Akagi ◽

Daisuke Yoshinaga ◽

Katsutsugu Umeda ◽

...

Keyword(s):

Heart Failure ◽

Skeletal Muscle ◽

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Left Ventricular ◽

Muscle Disease ◽

Therapeutic Modality ◽

Cardiomyocyte Autophagy ◽

And Function ◽

Ventricle Size

Abstract Background: Duchenne muscular dystrophy (DMD), a severe degenerative skeletal and cardiac muscle disease, has a poor prognosis, and no curative treatments are available. Because autophagy has been reported to contribute to skeletal muscle degeneration, therapies targeting autophagy are expected to improve skeletal muscle hypofunction. However, the role of this regulatory mechanism has not been evaluated clearly in DMD cardiomyocytes. Methods: In the present study, we demonstrated that autophagy was enhanced in the cardiomyocytes of mdx mice, a model of DMD, and that increased autophagy contributed to the development of cardiomyopathy in this context. Results: As assessed by GFP-mRFP-LC3 transfection, autophagosomes were more abundant in cardiomyocytes of mdx mice compared with control wild-type (WT) mice. The number of autophagosomes was significantly enhanced by isoproterenol-induced cardiac stress (4 weeks) in cardiomyocytes of mdx but not WT mice. Simultaneously, isoproterenol increased cardiomyocyte fibrosis in mdx but not WT mice. Administration of chloroquine, an autophagy inhibitor, significantly decreased cardiomyocyte autophagy and fibrosis in mdx mice, even after isoproterenol treatment. Left ventricle size and function were evaluated by echocardiography. Left ventricular contraction was decreased in mdx mice after isoproterenol treatment compared with control mice, which was alleviated by chloroquine administration.Conclusions: These findings suggested that heart failure of DMD could be associated with autophagy. Therefore, autophagy inhibitors, such as chloroquine, are a potential therapeutic modality for heart failure in DMD patients.

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Vitamin D Status in Children with Idiopathic Dilated Cardiomyopathy

Journal of Child Science ◽

10.1055/s-0041-1731076 ◽

2021 ◽

Vol 11 (01) ◽

pp. e120-e124

Author(s):

Duaa M. Raafat ◽

Osama M. EL-Asheer ◽

Amal A. Mahmoud ◽

Manal M. Darwish ◽

Naglaa S. Osman

Keyword(s):

Vitamin D ◽

Serum Level ◽

Dilated Cardiomyopathy ◽

Smooth Muscles ◽

Left Ventricular ◽

Idiopathic Dilated Cardiomyopathy ◽

Vitamin D Receptors ◽

Left Ventricular Dimensions ◽

And Function ◽

Ventricular Dimensions

AbstractDilated cardiomyopathy (DCM) is the third leading cause of heart failure in pediatrics. The exact etiology of DCM is unknown in more than half of the cases. Vitamin D receptors are represented in cardiac muscles, endothelium, and smooth muscles of blood vessels suggesting that vitamin D could have a vital cardioprotective function. This study aimed to assess serum level of vitamin D in children with idiopathic DCM and to correlate the serum level of vitamin D with the left ventricular dimensions and function. This study is a descriptive cross-sectional single-center study, includes 44 children of both sexes, diagnosed as idiopathic DCM. Serum level of vitamin D was assessed and correlated with the left ventricular dimensions and function. Mean age of studied children was 6.08 ± 4.4 years. Vitamin D deficiency was found in 90.9% of children with idiopathic DCM with a mean level 13.48 ng/mL. There was a negative correlation between vitamin D level and fraction shortening and left ventricular end-diastolic diameter in children with DCM. Vitamin D level is not only significantly low in children with idiopathic DCM but it is also significantly correlated with the degree of left ventricular dysfunction.

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A carrier of Duchenne muscular dystrophy with dilated cardiomyopathy but no skeletal muscle symptom

Brain and Development ◽

10.1016/0387-7604(95)00018-7 ◽

1995 ◽

Vol 17 (3) ◽

pp. 202-205 ◽

Cited By ~ 18

Author(s):

Hirotoshi Kinoshita ◽

Yu-ichi Goto ◽

Mitsuru Ishikawa ◽

Tetsuya Uemura ◽

Kouichi Matsumoto ◽

...

Keyword(s):

Skeletal Muscle ◽

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Dilated Cardiomyopathy ◽

Muscle Symptom

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Abstract MP216: Identification Of Novel Phosphoprotein Signaling Pathways In Human Dilated Cardiomyopathy By Integrative Proteomic And Phosphoproteomic Analysis

Circulation Research ◽

10.1161/res.129.suppl_1.mp216 ◽

2021 ◽

Vol 129 (Suppl_1) ◽

Author(s):

Cristine J Reitz ◽

Marjan Tavassoli ◽

Da Hye Kim ◽

Sina Hadipour-Lakmehsari ◽

Saumya Shah ◽

...

Keyword(s):

Dilated Cardiomyopathy ◽

Cardiac Tissue ◽

Regulatory Element ◽

Critical Role ◽

Left Ventricular ◽

Confocal Imaging ◽

Intercalated Disc ◽

Bioinformatics Analyses ◽

Tissue Samples ◽

And Function

Dilated cardiomyopathy (DCM) is one of the most common causes of heart failure, yet the majority of the underlying signaling mechanisms remain poorly characterized. Protein phosphorylation is a key regulatory element with profound effects on the activity and function of signaling networks; however, there is a lack of comprehensive phosphoproteomic studies in human DCM patients. We assessed the hypothesis that an integrative phosphoproteomics analysis of human DCM would reveal novel phosphoprotein candidates involved in disease pathophysiology. Combined proteomic and phosphoproteomic analysis of explanted left ventricular tissue samples from DCM patients ( n =4) and non-failing controls ( n =4) identified 5,570 unique proteins with 13,624 corresponding phosphorylation sites. From these analyses, we identified αT-catenin as a unique candidate protein with a cluster of 4 significantly hyperphosphorylated sites in DCM hearts ( P <0.0001), with no change in total αT-catenin expression at the protein level. Bioinformatics analyses of human datasets and confocal imaging of human and mouse cardiac tissue show highly cardiac-enriched expression of αT-catenin, localized to the cardiomyocyte intercalated disc. High resolution 3-dimensional reconstruction shows elongated intercalated disc morphology in DCM hearts (10.07±0.76 μm in controls vs. 17.20±1.87 μm in DCM, P <0.05, n =3/group), with significantly increased colocalization of αT-catenin with the intercalated disc membrane protein N-cadherin (Pearson’s coefficient 0.55±0.04 in controls vs. 0.71±0.02 in DCM, P <0.05, n =3/group). To investigate the functional role of cardiac αT-catenin phosphorylation, we overexpressed WT protein vs. non-phosphorylatable forms based on the loci identified in DCM hearts, in adult mouse cardiomyocytes using lentiviral transduction. Confocal imaging revealed significant internalization of the phospho-null form, as compared to the prominent intercalated disc staining of the WT protein (17.78±0.79% of WT vs. 9.25±0.49% of 4A mutant, P <0.0001, n =50 cells/group). Together, these findings suggest a critical role for αT-catenin phosphorylation in maintaining cardiac intercalated disc organization in human DCM.

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Emery-Dreifuss muscular dystrophy with dilated cardiomyopathy preceding skeletal muscle symptoms

Cardiology in the Young ◽

10.1017/s1047951121004674 ◽

2021 ◽

pp. 1-3

Author(s):

Koichi Takamizawa ◽

Ki-Sung Kim ◽

Hideaki Ueda

Keyword(s):

Skeletal Muscle ◽

Genetic Testing ◽

Muscular Dystrophy ◽

Dilated Cardiomyopathy ◽

Cardiac Complications ◽

Normal Muscle ◽

Initial Manifestation ◽

Skeletal Muscle Weakness ◽

Joint Disorder ◽

Myocardial Biopsies

Abstract Emery-Dreifuss muscular dystrophy is a slowly progressive skeletal muscle and joint disorder associated with cardiac complications. Dilated cardiomyopathy was the initial manifestation of Emery-Dreifuss muscular dystrophy in an 8-year-old girl. Despite normal muscle and myocardial biopsies, genetic testing revealed LMNA mutations. As Emery-Dreifuss muscular dystrophy is associated with minimal skeletal muscle weakness, cardiac complications can facilitate its diagnosis.

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Postnatal development of mice with combined genetic depletions of lamin A/C, emerin and lamina-associated polypeptide 1

Human Molecular Genetics ◽

10.1093/hmg/ddz082 ◽

2019 ◽

Vol 28 (15) ◽

pp. 2486-2500 ◽

Cited By ~ 1

Author(s):

Yuexia Wang ◽

Ji-Yeon Shin ◽

Koki Nakanishi ◽

Shunichi Homma ◽

Grace J Kim ◽

...

Keyword(s):

Skeletal Muscle ◽

Muscular Dystrophy ◽

Left Ventricular Function ◽

Left Ventricular ◽

Lamin A ◽

Heterozygous Deletion ◽

Gene Encoding ◽

Heart Ultrastructure ◽

Electrocardiographic Parameters ◽

Normal Embryonic Development

Abstract Mutations in LMNA encoding lamin A/C and EMD encoding emerin cause cardiomyopathy and muscular dystrophy. Lmna null mice develop these disorders and have a lifespan of 7–8 weeks. Emd null mice show no overt pathology and have normal skeletal muscle but with regeneration defects. We generated mice with germline deletions of both Lmna and Emd to determine the effects of combined loss of the encoded proteins. Mice without lamin A/C and emerin are born at the expected Mendelian ratio, are grossly normal at birth but have shorter lifespans than those lacking only lamin A/C. However, there are no major differences between these mice with regards to left ventricular function, heart ultrastructure or electrocardiographic parameters except for slower heart rates in the mice lacking both lamin A/C and emerin. Skeletal muscle is similarly affected in both of these mice. Lmna+/− mice also lacking emerin live to at least 1 year and have no significant differences in growth, heart or skeletal muscle compared to Lmna+/− mice. Deletion of the mouse gene encoding lamina-associated protein 1 leads to prenatal death; however, mice with heterozygous deletion of this gene lacking both lamin A/C and emerin are born at the expected Mendelian ratio but had a shorter lifespan than those only lacking lamin A/C and emerin. These results show that mice with combined deficiencies of three interacting nuclear envelope proteins have normal embryonic development and that early postnatal defects are primarily driven by loss of lamin A/C or lamina-associated polypeptide 1 rather than emerin.

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Empagliflozin improves chronic hypercortisolism-induced abnormal myocardial structure and cardiac function in mice

Therapeutic Advances in Chronic Disease ◽

10.1177/2040622320974833 ◽

2020 ◽

Vol 11 ◽

pp. 204062232097483

Author(s):

Qing-Qing Zhang ◽

Guo-Qing Li ◽

Yi Zhong ◽

Jie Wang ◽

An-Ning Wang ◽

...

Keyword(s):

Myocardial Dysfunction ◽

Sglt2 Inhibitor ◽

Heart Tissue ◽

Left Ventricular ◽

Tissue Samples ◽

Beneficial Effects ◽

Reduced Body ◽

Sodium Glucose Cotransporter ◽

And Function ◽

Visceral Adipose

Background: Chronic exposure to excess glucocorticoids is frequently associated with a specific cardiomyopathy. Empagliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, has beneficial effects as it aids in the reduction of heart failure and cardiovascular mortality in hospitalized patients. The aim of this study was to investigate the effects of empagliflozin on chronic hypercortisolism-induced myocardial fibrosis and myocardial dysfunction in mice. Methods: Male C57BL/6J mice (6 weeks old) were randomized to control, corticosterone (CORT), and empagliflozin + CORT groups. After 4 weeks of administration, heart structure and function were evaluated by echocardiography, and peripheral blood and tissue samples were collected. Expressions of Ccl2, Itgax, Mrc1, and Adgre1 mRNA in heart tissue were evaluated by RT-PCR, and signal transducer and activator of transcription 3 (STAT3) and Toll-like receptor 4 (TLR4) protein expression were analyzed by Western blotting. Results: Empagliflozin effectively reduced body weight, liver triglyceride, visceral adipose volume, and uric acid in CORT-treated mice. Left ventricular hypertrophy and cardiac dysfunction were improved significantly, phosphorylated STAT3 and TLR4 were alleviated, and macrophage infiltration in the myocardium was inhibited after administration of empagliflozin in CORT-treated mice. Conclusion: Empagliflozin has beneficial effects on specific cardiomyopathy associated with CORT, and the results provide new evidence that empagliflozin might be a potential drug for the prevention of this disease.

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Association between pulmonary function and left ventricular volume and function in duchenne muscular dystrophy

Muscle & Nerve ◽

10.1002/mus.26623 ◽

2019 ◽

Vol 60 (3) ◽

pp. 286-291 ◽

Cited By ~ 2

Author(s):

Arshjot Khokhar ◽

Athira Nair ◽

Vishal Midya ◽

Ashutosh Kumar ◽

Ankita Sinharoy ◽

...

Keyword(s):

Duchenne Muscular Dystrophy ◽

Muscular Dystrophy ◽

Pulmonary Function ◽

Left Ventricular Volume ◽

Ventricular Volume ◽

Left Ventricular ◽

And Function

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Growth differentiation factor 15 (GDF-15) inhibition to increase muscle mass and function in cancer cachexia.

Journal of Clinical Oncology ◽

10.1200/jco.2020.38.15_suppl.e15633 ◽

2020 ◽

Vol 38 (15_suppl) ◽

pp. e15633-e15633

Author(s):

Matthew Peloquin ◽

Brianna LaCarubba ◽

Stephanie Joaqium ◽

Gregory Weber ◽

John Stansfield ◽

...

Keyword(s):

Skeletal Muscle ◽

Body Weight ◽

Muscle Mass ◽

Muscle Function ◽

Skeletal Muscle Mass ◽

Cancer Cachexia ◽

Tumor Model ◽

Growth Differentiation Factor 15 ◽

Myostatin Inhibition ◽

And Function

e15633 Background: Almost half of cancer deaths are attributed to cancers most frequently associated with cachexia. Cachexia is a complex metabolic disease characterized by anorexia and unintentional weight loss. Skeletal muscle depletion has been recognized as a key feature of the disease, however muscle anabolic therapies have not been successful, suggesting that treatments that target multiple aspects of the disease will be most effective. Growth differentiation factor 15 (GDF-15) is a cytokine that induces anorexia and weight loss and is associated with cachexia in cancer patients. In preclinical cancer cachexia models, GDF-15 inhibition is sufficient to normalize food intake and body weight, including skeletal muscle mass. However, it remains to be determined whether the increased skeletal muscle mass also results in restoration of muscle function. Therefore, we examined the effect of GDF-15 inhibition on muscle mass and function in mouse models of cancer cachexia in comparison with myostatin inhibition, an established muscle anabolic pathway. Methods: Cachectic mouse tumor models were established with subcutaneous implantation of tumor cell lines reported to be GDF-15-dependent; mouse renal cell carcinoma (RENCA) and human ovarian cancer (TOV-21G) cell lines. Mice were treated with anti-GDF-15 (mAB2) or anti-myostatin (RK35) monoclonal antibodies and skeletal muscle function was assessed in vivo via maximum force, maximum rate of contraction and half relax time. In the RENCA tumor model, GDF-15 inhibition fully restored body weight and skeletal muscle mass whereas myostatin inhibition showed only a modest effect. Results: Consistent with the muscle mass improvement, GDF-15 inhibition dramatically increased functional muscle endpoints compared to the partial effect of myostatin inhibition. Interestingly, in the TOV-21G tumor model GDF-15 inhibition only partially restored body weight, however skeletal muscle mass and muscle function were completely normalized. Consistent with the functional assessment, GDF-15 inhibition in the RENCA tumor model decreased the expression of several catabolic genes (i.e. Trim63, Fbxo32, Myh7 and Myh2). The GDF-15 effect is likely to be secondary to the reversal of anorexia since wildtype mice pair-fed to Fc-GDF-15-treated mice demonstrated equivalent muscle mass loss. Conclusions: Taken together these data suggest that GDF-15 inhibition holds potential as an effective therapeutic approach to alleviate multiple aspects of cachexia.

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