Dilated Cardiomyopathy In Duchenne Muscular Dystrophy Research Articles

The IAAM LTBP4 Haplotype is Protective Against Dystrophin-Deficient Cardiomyopathy.

Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of progression display wide variability, whose molecular bases have been scarcely elucidated. Potential DCM-modifying factors include glucocorticoid (GC) and cardiological treatments, DMD mutation type and location, and variants in other genes. We retrospectively collected 3138 echocardiographic measurements of left ventricular ejection fraction (EF), shortening fraction (SF), and end-diastolic volume (EDV) from 819 DMD participants, 541 from an Italian multicentric cohort and 278 from the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS). Using generalized estimating equation (GEE) models, we estimated the yearly rate of decrease of EF (-0.80%) and SF (-0.41%), while EDV increase was not significantly associated with age. Utilizing a multivariate generalized estimating equation (GEE) model we observed that mutations preserving the expression of the C-terminal Dp71 isoform of dystrophin were correlated with decreased EDV (-11.01 mL/m2, p = 0.03) while for dp116 were correlated with decreased EF (-4.14%, p = <0.001). The rs10880 genotype in the LTBP4 gene, previously shown to prolong ambulation, was also associated with increased EF and decreased EDV (+3.29%, p = 0.002, and -10.62 mL/m2, p = 0.008) with a recessive model. We quantitatively describe the progression of systolic dysfunction progression in DMD, confirm the effect of distal dystrophin isoform expression on the dystrophin-deficient heart, and identify a strong effect of LTBP4 genotype of DCM in DMD.

Abstract 14072: Bioenergetic and Metabolic Impairments in Duchenne Muscular Dystrophy (DMD) Patients' Induced Pluripotent Stem Cell-derived Cardiomyocytes (iPSC-CMs)

Introduction: DMD, an X-linked muscle degenerative fatal disease, is caused by mutations in the dystrophin gene. Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality in DMD patients. Since the DMD DCM treatment is limited, novel therapeutic modalities are urgently needed. Hypothesis: We hypothesized that dystrophin mutations in DMD lead to cardiomyopathy-causing bioenergetic/metabolic impairments, which can be therapeutically targeted for improving cardiac function. Methods: The study included iPSC-CMs from a healthy volunteer and 3 DMD patients (young male, YM; adult male, AM; adult female, AF) and mdx mice. We investigated the bioenergetics, electrophysiology, mitochondrial and metabolic features of iPSC-CMs and heart tissues using the SeaHorse Flux Analyzer, patch clamp, confocal fluorescence microscopy and Liquid Chromatography Mass Spectrometry (LC-MS) technologies, respectively. Results: To test the hypothesis, we measured the iPSC-CM respiration rate using the SeaHorse. Compared to healthy, in both AM and AF DMD, but not in YM DMD cardiomyocytes, ATP production decreased by 75%, and basal respiration decreased by 80% and 45%, respectively. In agreement with impaired oxidative phosphorylation capacity, mitochondrial activity measured by 3D life confocal microscopy was attenuated by 35% in AM, but not in YM. Concurring with the healthy-like bioenergetic status, YM iPSC-CMs fired regularly with no arrhythmias, in contrast to the prominent arrhythmias in AM and AF cardiomyocytes. Further, the LC-MS analysis demonstrated that the levels of 13%, 6% and 7% of the 120 metabolite measured, were lower in AM, AF and YM, while 10%, 18% and 43% were higher, respectively, compared to healthy iPSC-CMs ( p&lt;0.05 ). For example, in AM and AF (but not in YM) the phosphocreatine (PCr) levels were diminished by &gt;80%, compared to healthy iPSC-CMs, indicating a dysfunctional PCr energy system. Finally, the LC-MS analysis of mdx ventricular tissue demonstrated a statistically-significant different metabolic profile in 8 mdx mice vs 8 healthy mice. Conclusion: DMD iPSC-CMs and mdx mice exhibit bioenergetic/metabolic impairments, which constitute novel targets for alleviating the cardiomyopathy in DMD patients.

Bioenergetic and metabolic impairments in Duchenne Muscular Dystrophy (DMD) patients' iPSC-derived cardiomyocytes

Abstract Introduction DMD, an X-linked muscle degenerative fatal disease, is caused by mutations in the dystrophin gene. Dilated cardiomyopathy (DCM) is a major cause of morbidity and mortality in DMD patients. Treatments for DCM in DMD are limited to steroids and standard heart failure medications such as β-blockers and ACE-inhibitors, and therefore novel therapeutic modalities are urgently needed. Purpose We hypothesized that dystrophin mutations in DMD lead to cardiomyopathy-causing bioenergetic/metabolic impairments, which can be therapeutically targeted for improving cardiac function. Methods Induced Pluripotent Stem Cell-derived cardiomyocytes (iPSC-CMs) were generated from healthy volunteer and 3 DMD patients: young male (YM), adult male (AM) and adult female (AF). We investigated the bioenergetics, electrophysiology, mitochondrial and metabolic features of healthy and DMD iPSC-CMs using the Seahorse Flux analyzer, patch clamp, confocal fluorescence microscopy and Liquid chromatography mass spectrometry (LC-MS) technologies, respectively. Results To test the hypothesis, we measured respiration and glycolytic rates of healthy and DMD iPSC-CMs. Compared to healthy iPSC-CMs, in both AM and AF DMD, but not in YM DMD cardiomyocytes, there was a 75% decrease in ATP production, and 80% and 45% decrease in basal respiration, respectively. In agreement with the healthy-like bioenergetic status of YM, the iPSC-CMs showed no arrhythmias, in contrast to the prominent arrhythmias in AM and AF cardiomyocytes. To determine whether the impairment in the phosphorylation pathway (OXPHOS) affects glycolysis, we measured the cardiomyocytes' response to glycolytic stress test. These experiments showed that the glycolytic rates were similar in healthy and DMD iPSC-CMs. In agreement with impaired OXPHOS, mitochondrial activity measured by 3D life confocal microscopy was attenuated in the DMD male by 35%, compared to healthy cardiomyocytes. Furthermore, the metabolomic LC-MS analyses demonstrated significant differences in metabolite levels in YM, AM and AF DMD iPSC-CMs relative to healthy iPSC-CMs. For example, compared to healthy iPSC-CMs, there was a dramatic fall to undetected levels in phosphocreatine in both AM and AF, but not in YM DMD, indicating a dysfunctional phosphocreatine energy system. Conclusions DMD iPSC-CMs exhibit bioenergetic/metabolic impairments, which constitute novel targets for alleviating the cardiomyopathy in DMD patients. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): ISF - Israel Science Foundation

Altered Wave Reflection in Patients with Duchenne Muscular Dystrophy (DMD)

Cardiovascular complications are progressive in Duchenne Muscular Dystrophy (DMD) with cardiomyopathy/heart failure characterized as the leading cause of death in these young patients. Increased wave reflection augments pulsatile load on the heart and is known to be predictive of new onset heart failure in adults. Patients with DMD may have higher wave reflection as measured by augmentation index (AIx) but this has yet to be comprehensively studied in these patients. Given the incidence of dilated cardiomyopathy in DMD, a better understanding of the pulsatile load and ventricular‐arterial interactions could provide valuable insight into disease progression and management.PURPOSEThus, the purpose of this study was to characterize wave reflectance and pulsatile load with wave separation and wave intensity analyses in a group of patients with DMD compared to typically‐developing controls.METHODSAssessments were performed on 23 boys (10 DMD and 13 typically‐developing controls (CON)) between the ages of 8 and 18 years. A brachial artery oscillometric‐cuff device was used to record brachial artery pressure waveforms that were calibrated and synthesized to central pressure waves using a generalized transfer function. Pulse wave analysis (PWA) was performed to determine central blood pressures and AIx. Wave separation analysis was also used to determine the relative contributions of forward (Pf) and backward (Pb) pressure waves and reflection magnitude (RM=Pb/Pf).RESULTSPatients with DMD had a significantly higher augmentation index (AI) as measured by PWA (DMD: 21.2 ± 5 vs CON: 0.9 ± 2 %, p&lt;0.05) but no difference in central pulse pressure (DMD: 34 ± 3 vs CON: 30 ± 1 mmHg). There was also no difference in Pf between groups (DMD: 27 ± 2 vs CON: 26 ± 2 mmHg). However, both Pb (DMD: 14.0 ± 1 vs CON: 11.7 ± 1 mmHg, p&lt;0.05) and RM (DMD: 52.0 ± 1 vs CON: 43.5 ± 2 %, p&lt;0.05) were significantly elevated in the children with DMD.CONCLUSIONThese preliminary data suggest that patients with DMD have higher wave reflection, which may indicate increased arterial stiffness and increased pulsatile load on the heart.Support or Funding InformationGrant support: NIH P20GM113125This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Telomere shortening and metabolic compromise underlie dystrophic cardiomyopathy

Duchenne muscular dystrophy (DMD) is an incurable X-linked genetic disease that is caused by a mutation in the dystrophin gene and affects one in every 3,600 boys. We previously showed that long telomeres protect mice from the lethal cardiac disease seen in humans with the same genetic defect, dystrophin deficiency. By generating the mdx4cv/mTRG2 mouse model with "humanized" telomere lengths, the devastating dilated cardiomyopathy phenotype seen in patients with DMD was recapitulated. Here, we analyze the degenerative sequelae that culminate in heart failure and death in this mouse model. We report progressive telomere shortening in developing mouse cardiomyocytes after postnatal week 1, a time when the cells are no longer dividing. This proliferation-independent telomere shortening is accompanied by an induction of a DNA damage response, evident by p53 activation and increased expression of its target gene p21 in isolated cardiomyocytes. The consequent repression of Pgc1α/β leads to impaired mitochondrial biogenesis, which, in conjunction with the high demands of contraction, leads to increased oxidative stress and decreased mitochondrial membrane potential. As a result, cardiomyocyte respiration and ATP output are severely compromised. Importantly, treatment with a mitochondrial-specific antioxidant before the onset of cardiac dysfunction rescues the metabolic defects. These findings provide evidence for a link between short telomere length and metabolic compromise in the etiology of dilated cardiomyopathy in DMD and identify a window of opportunity for preventive interventions.

Left Ventricular Tonic Contraction as a Novel Biomarker of Cardiomyopathy in Duchenne Muscular Dystrophy.

Dilated cardiomyopathy (DCM) inevitably afflicts patients with Duchenne muscular dystrophy (DMD) as a consequence of cell death induced by unguarded calcium influx into cardiomyocytes. This mechanism may also inhibit muscle relaxation in early stages of cardiomyopathy. ACE inhibition (ACEi) is known to delay the onset and slow the progression of DCM in DMD. The objective of this study is to use echocardiography to assess for preclinical cardiac changes consistent with intracellular calcium dysregulation before the onset of overt ventricular dysfunction, and to evaluate how prophylactic ACEi may alter these pre-cardiomyopathic changes in the pediatric DMD population. We examined 263 echocardiograms from 70 pediatric patients with DMD. We defined abnormal tonic contraction (TC) as left ventricular internal dimension in diastole (LVIDd) Z-score < -1.5. In our cohort, we found that TC is detectable as early as 8 years of age, and most commonly affects patients between 11 and 15 years. This effect was independent of LV mass and systolic function. Prophylactic ACEi decreased the incidence of TC (p = 0.007) and preserved cardiac function (p < 0.0001). Left ventricular TC often precedes DCM in DMD, most commonly affecting the 11- to 15-year-old age range. TC is not related to ventricular hypertrophy, but rather may be a clinical correlate of the "calcium hypothesis" of DMD pathophysiology. LV TC is thus a promising biomarker for early detection of cardiomyopathy in DMD. ACEi prophylaxis suppresses LV TC and delays the development of DCM in DMD.

LEFT VENTRICULAR TONIC CONTRACTION FREQUENTLY PRECEDES DILATION IN CARDIOMYOPATHY OF DUCHENNE MUSCULAR DYSTROPHY

Dilated cardiomyopathy (DCM) inevitably afflicts patients with Duchenne muscular dystrophy (DMD). Understanding of the molecular pathophysiology of DCM in DMD has advanced, but correlation of these advances with clinical disease is lacking. We sought to identify echocardiographic changes that occur

P.2.17 Hypertrophic cardiomyopathy in a patient with Duchenne muscular dystrophy

Dilated cardiomyopathy is observed in Duchenne muscular dystrophy (DMD). We report the case of a 28 year old DMD patient who exhibited a hypertrophic phenotype and preservation of cardiac function. On cardiac magnetic resonance imaging (CMR), the patient demonstrated severe asymmetric septal hypertrophy, raising the possibility of an underlying genetic cause distinct from DMD. Left ventricular systolic function was preserved with a normal ejection fraction. Additional CMR late gadolinium enhancement (LGE) imaging for myocardial fibrosis demonstrated an unusual LGE pattern. The sub-epicardial LGE in the left ventricular free wall was typical of those found in DMD patients. However, LGE was also present at the right and left ventricular insertion points typical of patients with hypertrophic cardiomyopathy. The patient has a commonly found DMD mutation, duplication in exons 3–4 of the dystrophin gene, predictive of the characteristic DMD dilated cardiomyopathy. Further genetic testing for genes known to cause hypertrophic cardiomyopathy identified two mutations: a heterozygous Glu542Gln mutation in the MYBPC3 gene and a heterozygous Glu195Lys mutation in the TNNT2 gene. Both mutations have been reported as disease causing in individuals with autosomal dominant hypertrophic cardiomyopathy. This case illustrates the co-occurrence of two relatively common genetic conditions: DMD and HCM. We postulate that these confounding gene mutations led to cardiac muscle hypertrophy, preventing the expected development of the typical dilated cardiomyopathy. The downstream pathways by which the cardiac hypertrophy and myocyte disarray resulting from MYBPC3 and TNNT2 mutations might abrogate cardiac dysfunction caused by dystrophinopathy are unknown but have important clinical implications. They may reveal a potential gene-based therapeutic strategy whereby insertion of a pro-hypertrophic gene variant may ameliorate or prevent dilated cardiomyopathy in DMD patient.

Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD), the most common inherited muscular dystrophy of childhood, leads to death due to cardiorespiratory failure. Paradoxically, mdx mice with the same genetic deficiency of dystrophin, exhibit minimal cardiac dysfunction, impeding the development of therapies. We postulated that the difference between mdx and DMD might result from differences in telomere lengths in mice and humans. We show here that, like DMD patients, mice that lack dystrophin and have shortened telomeres (mdx/mTRKO) develop severe functional cardiac deficits including ventricular dilation, contractile and conductance dysfunction, and accelerated mortality. These cardiac defects are accompanied by telomere erosion, mitochondrial fragmentation, and increased oxidative stress. Treatment with anti-oxidants significantly retards the onset of cardiac dysfunction and death of mdx/mTRKO mice. In corroboration, of four DMD patients analyzed, all had 45% shorter telomeres in their cardiomyocytes relative to age- and sex-matched controls. We propose that the demands of contraction in the absence of dystrophin coupled with increased oxidative stress conspire to accelerate telomere erosion culminating in cardiac failure and death. These findings provide strong support for a link between telomere length and dystrophin deficiency in the etiology of dilated cardiomyopathy in DMD and suggest preventive interventions.

Re-examination of the Electrocardiogram in Boys With Duchenne Muscular Dystrophy and Correlation With Its Dilated Cardiomyopathy

Duchenne muscular dystrophy (DMD) results in dilated cardiomyopathy (DC). Characteristic electrocardiographic (ECG) changes include short PR interval, right ventricular hypertrophy (RVH), prolonged QTc interval, and prominent Q waves in leads I, aVL, V5, and V6 or in leads II, III, aVF, V5, and V6. We re-examined the prevalence and correlation of ECG changes with DC in DMD. Electrograms of 115 patients with DMD were evaluated. DC was defined as an echocardiographic ejection fraction<55%. PR interval and RVH were based on age-based normal values. Abnormal Q waves were >or=4 mm. Abnormal QTc interval was >or=450 ms. ST-segment depression was defined as >0.5 mm. Fisher's exact test evaluated significant differences between groups and logistic regression determined whether number of ECG changes predicted DC. Forty had DC. No significant differences existed between the number of ECG changes in DC and non-DC groups (p=0.279). Distribution of findings included short PR interval (43%), RVH (37%), prominent Q waves in leads V5 (34%) and V6 (33%), prominent Q waves in leads I, aVL, V5, and V6 (3, 1 with DC), prominent Q waves in leads II, III, aVF, V5, and V6 (9, 4 with DC), long QTc interval (0), ST depression (2, 1 with DC), and flat/biphasic ST segments (38, 15 with DC). In conclusion, ECG changes are similar in patients with DMD regardless of presence of DC. Previously reported characteristic ECG changes are seen in a minority of DMD cases. The most common findings are short PR interval and RVH. Prominent Q waves in leads II, III, aVF, V5, and V6 are more likely.