Duchenne Muscular Dystrophy Cardiomyopathy Research Articles

The Role of Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases in Duchenne Muscular Dystrophy Cardiomyopathy

Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD). Standard cardiac biomarkers are poor indicators of DMD cardiovascular disease. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) regulate collagen turnover. Given the cardiac fibrosis seen in DMD, we hypothesized that MMPs and TIMPs correlate with severity of DMD cardiomyopathy. Prospectively enrolled DMD subjects (n = 42) underwent cardiac magnetic resonance imaging for function and late gadolinium enhancement (LGE), including LGE severity from 0 (no LGE) to 4 (severe). Serum from DMD and healthy male control subjects (n = 15) analyzed for MMPs 1, 2, 3, 7, 9, and 10 and TIMPs 1-4. MMP1, MMP7, and MMP10 were higher in DMD than in control (respectively, median 5080 pg/mL vs 2120 pg/mL [P = .007], 2170 pg/mL vs 1420 pg/mL [P < .001], and 216 pg/mL vs 140pg/mL [P = .040]); TIMP4 was lower in DMD (124 pg/mL vs 263 pg/mL; P = .046). Within DMD, MMP7 correlated inversely with left ventricular ejection fraction (r = -0.40; P = .012) and directly with strain (r = 0.54; P = .001) and LGE severity (r = 0.47; P = .003). MMP7 was higher in DMD patients with LGE compared with those without LGE and control subjects (P < .001). Multiple MMPs are elevated in DMD compared with control subjects. MMP7 is related to DMD cardiac dysfunction and myocardial fibrosis, possibly through remodeling of the extracellular matrix.

Increased Blood Pressure and Body Mass Index as Potential Modifiable Factors in The Progression of Myocardial Dysfunction in Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is characterized by progressive cardiomyopathy. Left ventricular (LV) function may worsen by factors increasing LV afterload such as hypertension and obesity. To identify potential modifiable risk factors for progression of cardiomyopathy in Duchenne muscular dystrophy (DMD). We retrospectively analysed systolic blood pressures (SBP) and body-mass indexes (BMI) from 273 visits of 65 DMD patients aged 4-18 years between 2003 and 2016, divided in 14 age groups. Values were normalized using Z-scores (Z-SBP and Z-BMI). A linear mixed model was used to analyse correlations between Z-SBP and BMI, steroid use, age, ambulatory status and cardiac medication (CM) use. To study the relationship between SBP and BMI and myocardial deformation prior to the onset of clinical cardiomyopathy, LV deformation, defined by global longitudinal strain (GLS), was quantified in a subset of 36 patients <11 years. Multiple linear regression was used to study the relation between GLS and clinical parameters. Median follow-up was 5 years. SBP was significantly elevated in all age groups under 14 years (p≤0.04) and 15-16 years (p = 0.033) and correlated positively with BMI (p = 0.001) and negatively with CM use over time (p = 0.018). Z-BMI followed a bell-shaped distribution and plotted approximately one standard deviation above the mean in patients between 7 and 15 years. In the subset of younger patients, reduced GLS was associated with higher BMI (β= 0.348, p = 0.004). SBP and BMI may be potentially modifiable factors to retard deterioration of LV function in DMD.

Abstract 16715: Troponin I Levels Correlate With Cardiac Magnetic Resonance Late Gadolinium Enhancement and Native T1 Values in Duchenne Muscular Dystrophy Cardiomyopathy and Identify Early Disease Progression

Introduction: Cardiomyopathy is the leading cause of death in Duchenne muscular dystrophy (DMD). Elevated troponin levels are observed in DMD and may vary with disease progression. We studied troponin levels in DMD related to myocardial fibrosis and native T1 measures. Methods: This is a prospective, cross-sectional, observational study of 30 DMD subjects measuring native T1 levels and late gadolinium enhancement (LGE) on cardiac MR imaging (CMR) correlated with temporally associated serum troponin I levels. Non-parametric analyses including Spearman correlations and Kruskal-Wallis test were performed between groups. P-values resulting from the pair-wise comparisons were adjusted for multiple comparisons using the Sidak method where appropriate. Results: There were 15 DMD subjects with no LGE (age 12±3 yo; EF% 60±5) and troponin I level of 0.05±0.08; 7 DMD subjects with mild LGE (age 17±5 yo, EF% 52±8) and troponin I level of 0.28±0.36; and 8 DMD subjects with moderate to severe LGE (age 16±6 yo; EF% 54±8) and troponin I level of 0.11±0.14. There was a statistically significant positive correlation between troponin I levels and MOLLI septal native T1 values (r2=0.173, p=0.02). Troponin I levels in DMD subjects with mild LGE were significantly increased compared to subjects with no LGE (p=0.02). MOLLI lateral native T1 levels were increased with moderate-severe LGE compared to mild and none (p&lt;0.01), but did not correlate with troponin levels. Conclusions: Serum biomarker troponin I levels were increased in DMD subjects with mild LGE and correlated with MOLLI septal native T1 values. Troponin I levels may be a useful minimally invasive outcome marker to monitor myocardial disease progression in DMD cardiomyopathy.

Efficacy of Multi-exon Skipping Treatment in Duchenne Muscular Dystrophy Dog Model Neonates

Duchenne muscular dystrophy (DMD) is caused by mutations in DMD, which codes for dystrophin. Because the progressive and irreversible degeneration of muscle occurs from childhood, earlier therapy is required to prevent dystrophic progression. Exon skipping by antisense oligonucleotides called phosphorodiamidate morpholino oligomers (PMOs), which restores the DMD reading frame and dystrophin expression, is a promising candidate for use in neonatal patients, yet the potential remains unclear. Here, we investigate the systemic efficacy and safety of early exon skipping in dystrophic dog neonates. Intravenous treatment of canine X-linked muscular dystrophy in Japan dogs with a 4-PMO cocktail resulted in ∼3%-27% in-frame exon 6-9 skipping and dystrophin restoration across skeletal muscles up to 14% of healthy levels. Histopathology was ameliorated with the reduction of fibrosis and/or necrosis area and centrally nucleated fibers, significantly in the diaphragm. Treatment induced cardiac multi-exon skipping, though dystrophin rescue was not detected. Functionally, treatment led to significant improvement in the standing test. Toxicity was not observed from blood tests. This is the first study to demonstrate successful multi-exon skipping treatment and significant functional improvement in dystrophic dogs. Early treatment was most beneficial for respiratory muscles, with implications for addressing pulmonary malfunction in patients.

Exosome-Derived Dystrophin from Allograft Myogenic Progenitors Improves Cardiac Function in Duchenne Muscular Dystrophic Mice.

Progressive cardiomyocyte loss in Duchenne muscular dystrophy (DMD) leads to cardiac fibrosis, cardiomyopathy, and eventually heart failure. In the present study, we observed that myogenic progenitor cells (MPC) carry mRNA for the dystrophin gene. We tested whether cardiac function can be improved in DMD by allograft transplantation of MPC-derived exosomes (MPC-Exo) into the heart to restore dystrophin protein expression. Exo from C2C12 cells (an MPC cell line) or vehicle were delivered locally into the hearts of MDX mice. After 2days of treatment, we observed that MPC-Exo restored dystrophin expression in the hearts of MDX mice, which correlated with improved myocardial function in dystrophin-deficient MDX mouse hearts. In conclusion, this study demonstrated that allogeneic WT-MPC-Exo transplantation transiently restored dystrophin gene expression and improved cardiac function in MDX mice, suggesting that allogenic exosomal delivery may serve as an alternative treatment for cardiomyopathy of DMD.

Exacerbation of dystrophic cardiomyopathy by phospholamban deficiency mediated chronically increased cardiac Ca2+ cycling in vivo.

Cardiomyopathy is a significant contributor to morbidity and mortality in Duchenne muscular dystrophy (DMD). Membrane instability, leading to intracellular Ca2+ mishandling and overload, causes myocyte death and subsequent fibrosis in DMD cardiomyopathy. On a cellular level, cardiac myocytes from mdx mice have dysregulated Ca2+ handling, including increased resting Ca2+ and slow Ca2+ decay, especially evident under stress conditions. Sarco(endo)plasmic reticulum Ca2+ ATPase and its regulatory protein phospholamban (PLN) are potential therapeutic targets for DMD cardiomyopathy owing to their key role in regulating intracellular Ca2+ cycling. We tested the hypothesis that enhanced cardiac Ca2+ cycling would remediate cardiomyopathy caused by dystrophin deficiency. We used a genetic complementation model approach by crossing dystrophin-deficient mdx mice with PLN knockout (PLNKO) mice [termed double-knockout (DKO) mice]. As expected, adult cardiac myocytes isolated from DKO mice exhibited increased contractility and faster relaxation associated with increased Ca2+ transient peak height and faster Ca2+ decay rate compared with control mice. However, compared with wild-type, mdx, and PLNKO mice, DKO mice unexpectedly had reduced in vivo systolic and diastolic function as measured by echocardiography. Furthermore, Evans blue dye uptake was increased in DKO hearts compared with control, mdx, and PLNKO hearts, demonstrating increased membrane damage, which subsequently led to increased fibrosis in the DKO myocardium in vivo. In conclusion, despite enhanced intracellular Ca2+ handling at the myocyte level, DMD cardiomyopathy was exacerbated owing to unregulated chronic increases in Ca2+ cycling in DKO mice in vivo. These findings have potentially important implications for ongoing therapeutic strategies for the dystrophic heart. NEW & NOTEWORTHY This study examined the effects of phospholamban ablation on the pathophysiology of cardiomyopathy in dystrophin-deficient mice. In this setting, contractility and Ca2+ cycling were enhanced in isolated myocytes; however, in vivo heart function was diminished. Additionally, sarcolemmal integrity was compromised and fibrosis was increased. This is the first study, to our knowledge, examining unregulated Ca2+ cycling in the dystrophin-deficient heart. Results from this study have implications for potential therapies targeting Ca2+ handling in dystrophic cardiomyopathy. Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/unregulated-ca2-cycling-exacerbates-dmd-cardiomyopathy/ .

Abstract 310: Mechanistic Insights into Duchenne Muscular Dystrophy-Associated Cardiomyopathy

Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disorder resulting from a mutation in the dystrophin gene. Loss of dystrophin function leads to progressive muscle wasting and cardiomyopathy. In 2018, advanced cardiomyopathy is the primary mode of death, despite the application of standard of care CHF therapies. Our group has recently undertaken a cardiac MRI study demonstrating that adult DMD patients have small hearts with very low LV mass as compared to patients with non-ischemic cardiomyopathy or healthy patients. The central hypothesis is DMD-associated cardiomyopathy develops secondary to dysregulation of various cardiac signaling pathways that modulate cardiac growth, namely cardiomyocyte proliferation. Utilizing the mdx mouse, a model of DMD, decreased heart/body weight ratios were noted from birth (P1: Hrt/BW 5.6 ± 0.16 vs. 4.8 ± 0.18 NTg vs mdx p&lt;0.005 n=32). NTg and m dx hearts have similar cardiomyocyte cell size (WGA staining: 0.08 ± 0.001 vs 0.08 ± 0.002 NTg vs mdx p&lt;0.05 n=3), suggesting there are fewer cells in mdx hearts. FACS analysis indicated mdx hearts have fewer cardiomyocytes than NTg hearts (35% reduction; 51.7e 4 ± 4.9e 4 vs. 33.8e 4 ± 3.5e 4 NTg vs mdx p&lt;0.05 n=6). Transcriptome profiling demonstrated that molecular pathways governing cardiac proliferation were significantly reduced in mdx hearts (Ki67: 4.8 ± 0.3 vs 2.0 ± 0.1 NTg vs mdx p&lt;0.005 n=3), with a corresponding increase in cardiac atrophy gene expression at later time points (Foxo3 1.4 ± 0.2 vs 2.8 ± 0.3 NTg vs mdx p&lt;0.005 n=3). Furthermore, immunohistochemical analyses showed significantly reduced proliferation in mdx hearts (Ki67: 13.7 ± 1.2 vs. 6.0 ± 1.0 NTg vs mdx p&lt;0.005, n=3; pH3: 118 ± 5.3 vs 59 ± 4.5 p&lt;0.005 n=3). Finally, RNA-Seq data revealed a disruption of the YAP signaling pathway, an important mediator of cardiomyocyte proliferation, in mdx P4 hearts. Cell cycle targets of YAP were reduced in P4 mdx hearts (20/27 genes, n=3) suggesting a disruption of the Hippo-Yap pathways in mdx hearts. Collectively, the current study provides a unique insight into the mechanism leading to the development DMD cardiomyopathy and directs investigation into potential therapeutic targets for the amelioration of DMD-associated cardiomyopathy.

Abstract 241: In Vitro Disease Modeling and Discovery of Small Molecules for the Treatment of Duchenne Muscular Dystrophy Utilizing Patient iPSC-derived Cardiomyocytes

Duchenne Muscular Dystrophy (DMD) is a fatal disease of skeletal and cardiac muscle characterized by progressive muscle weakness and atrophy. Current average life expectancy is in the mid-20s and mortality is often linked to end stage cardiomyopathy. DMD is a monogenic disease caused by loss-of-function mutations in the dystrophin gene. While dystrophin is critical for muscle function by connecting the cytoskeleton to the sarcolemma and extracellular matrix, its absence can be largely compensated for by up-regulation of utrophin (UTRN), the fetal orthologue of dystrophin. Because of the importance of UTRN expression in the heart in both DMD patients and preclinical models, we utilized DMD patient iPSC-derived cardiomyocytes as a relevant cellular model to perform in vitro pharmacology as well as functional assessment. Human iPSC-derived cardiomyocytes recapitulate key properties of bona fide cardiomyocytes, such as expression of cardiac genes, spontaneous contractility, and response to chronotropic drugs (eg. isoproterenol and hERG channel blockers). We have created an isogenic pair of healthy control and DMD iPSC lines with exon 51 deletion using CRISPR/Cas9 technology. Functional measurements of cardiomyocyte electrophysiology were performed by multielectrode array (MEA) and fluorometric imaging plate reader (FLIPR) platforms. High-throughput assays were developed to measure UTRN expression in cardiomyocyte culture in 384-well plates. Importantly, we have identified small molecules that increased UTRN expression in both patient and isogenic DMD iPSC-derived cardiomyocytes. Our study represents a valuable strategy for small molecule drug discovery for the treatment of DMD cardiomyopathy based on iPSC technology.

Cardiovascular health supervision for Duchenne Muscular Dystrophy; data from the MD STARnet

BackgroundIn 2005, the American Academy of Pediatrics (AAP) published a policy statement on cardiovascular health supervision for Duchenne Muscular Dystrophy (DMD). Data is lacking on its effect on cardiovascular care. MethodsUsing the infrastructure of the Muscular Dystrophy Surveillance, Tracking and Research Network, we examined a population-based sample of individuals with DMD, focusing on cardiac testing and prescription of cardiac medication. Comparisons were made pre- (2000–2005) and post- (2006–2011) publication Results731 cases were studied; mean age of diagnosis 3.8 years and mean duration of follow-up 9.3 years. There was a significant decrease in time from diagnosis to first electrocardiogram (ECG) and echocardiogram (ECHO) from pre- to post-publication; 1047 (95% CI: 905–1188) days to 411 (95% CI: 324–498) days for ECG (p < 0.01) and 1153 (95% CI: 1022–1284) days to 352 (95% CI: 280–424) days for ECHO (p < 0.01). Only 4.5% and 8.2% of those ≥10 years of age met the recommendation for yearly ECG and ECHO respectively. Prescription of a cardiac medication with an abnormal ECHO increased post-publication 91/125, 72.8% versus pre- 47/77, 61.0% (p = 0.08). After 2005, cases with a normal ECHO were 2.3 (95% CI 1.23–4.31) times more likely to be prescribed a cardiac medication (p < 0.01). ConclusionsSince publication of the AAP statement, DMD patients are having cardiac testing sooner and cardiac medication is prescribed more often. However, the majority are not having testing with recommended frequency. Overcoming barriers to recommended cardiac care may lead to a better understanding of the natural history of cardiomyopathy in DMD and better treatment strategies.

Inhibition of prostaglandin D2 signaling prevents the progression of dilated cardiomyopathy in Duchenne muscular dystrophy

Inhibition of prostaglandin D2 signaling prevents the progression of dilated cardiomyopathy in Duchenne muscular dystrophy

Evaluation of cardiac functions in children with Duchenne Muscular Dystrophy: A prospective case-control study.

BackgroundDuchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. The incidence of cardiomyopathy in DMD increases with age, so its early detection is important because institution of cardioprotective medical therapies may slow adverse remodeling and attenuate heart failure symptoms in these patients.ObjectiveTo assess the cardiac functions in children clinically suspected to have DMD.MethodsOver a one-year period, 28 male children aged from 3 to 18 years old, who met the criteria for diagnosis of DMD compared to 47 healthy controls children, were approached to participate in the study. The included children were subjected to full clinical examination, and blood samples were collected to determine creatinine phosphokinase (CPK), troponin I enzyme, myoglobin and lactate dehydrogenase (LDH) enzyme level. Echocardiography and 12-leads electrocardiogram (ECG) were also done for children in both groups. Data were analyzed using Independent-samples t-test, Mann-Whitney U, Chi square, and Fisher’s exact test.ResultsThe mean age of the cases group was 7.29±3.24 years versus 8.06±2.86 years for controls. In DMD group, 25% had positive family history of DMD while 35.7% of them had positive consanguinity. All cases had elevated CPK level while CPK level in controls was normal (p<0.0001). LDH level was elevated in 19 cases (67.86%) of DMD while all controls children had normal LDH level (p<0.0001). Furthermore, the mean serum myoglobin level of DMD patients was higher relative to that of healthy controls (39.39±7.25 versus 33.68 ±12.38 ng/ml respectively) (p=0.01). Echocardiography of our patients revealed that seven cases (25%) had low ejection fraction (EF) and fraction shortening (FS). In addition, all controls children had normal EF (p<0.0001) and normal FS (p<0.0001). Interestingly, ECG showed that 28.57% of cases had sinus tachycardia vs. 6.88% for controls (p=0.0001). Prolonged QTc interval was present in 39.29% of cases (mean 431.39±43.60) while all controls had normal QTc duration for age (mean of 415.17±25.2) (p<0.0001).ConclusionECG manifestations in children with DMD in the form of sinus tachycardia and prolonged QTc interval are an early alarm for developing cardiomyopathy before overt echocardiographic findings appear.

NG.I.6 - The heart is a muscle too: the cardiomyopathy of Duchenne muscular dystrophy

NG.I.6 - The heart is a muscle too: the cardiomyopathy of Duchenne muscular dystrophy

P.54 - Increased blood pressure and BMI in relation to cardiomyopathy in Duchenne muscular dystrophy

P.54 - Increased blood pressure and BMI in relation to cardiomyopathy in Duchenne muscular dystrophy

P.321 - Ultrasonography evaluation of long-term taurine effects on cardiac and skeletal muscles of mdx mice

Taurine (Tau) is the most abundant free amino acid in heart and skeletal muscle. In these tissues Tau is involved in normal contractile function by regulating the calcium homeostasis and the calcium sensitivity of the contractile proteins. Preclinical studies in mdx mice disclosed promising effects of Tau as a countermeasure for the early alterations of skeletal muscle in Duchenne muscular dystrophy (DMD). DMD is a rare disease caused by the absence of sub-sarcolemmal protein dystrophin, progressively leading to skeletal muscle wasting and heart failure via altered calcium homeostasis abnormal inflammation and profibrotic signaling. We presently focused on the potential effectiveness of Tau supplementation on later cardiac muscle dysfunction in DMD, since this has never been investigated up to now. Tau was orally administered (1g/kg/daily) in male wild type (WT) and mdx mice at an initial age of 6 months. The treatment duration was 6 months. Tau effects were tested on WT and mdx mice by measuring body mass, in vivo force and resistance to treadmill exercise. In parallel, by using an UBM system (Vevo 2100; VisualSonics, Canada), ultrasound evaluation of the left ventricular function and hindlimb volume (V) and percentage of vascularization (%V) were also performed. Our results showed a significant reduction of stroke volume (SV; -30%), ejection fraction (EF; -18.4%) and fractional shortening (FS; -23%) in 12 months old untreated mdx mice with respect to the age-matched untreated WT. Interestingly, Tau treatment significantly and selectively counteracted the alterations of SV, EF and SF in mdx mice as the values were similar to those of untreated WT mice. No significant effects were observed on the V and %V of hindlimb skeletal muscle as well as on the other functional parameters in response to Tau. This study provide the new evidence that long term Tau supplementation could be an effective specific countermeasure for DMD cardiomyopathy (DPP-NL and PRIN-MIUR).

Interleukin 1 Receptor-Like 1 Protein (ST2) is a Potential Biomarker for Cardiomyopathy in Duchenne Muscular Dystrophy.

Duchenne muscular dystrophy (DMD) is a rare, fatal X-linked disorder characterized by the lack of dystrophin, a key sarcolemma muscle protein.Cardiac failure is a significant cause of death in DMD subjects. The purpose of our research was to identify potential cardiac serum biomarkers associated with DMD cardiomyopathy. This is an observational, case-controlled study using subjects from the CINRG DMD natural history study with cardiomyopathy (ejection fraction (EF) <55%; shortening fraction (SF) <28%), subjects without cardiomyopathy (EF≥55%; SF≥28%) compared to normal healthy volunteer subjects. The DMD with cardiomyopathy group had significantly lower average EF and SF (EF=45±10/SF=25±2%) than the DMD without cardiomyopathy group (EF=58±5% and SF=32±3%; p<0.01). Among a selected set of potential biomarkers for cardiomyopathy (MMP9, BNP, GAL3, CRP, LEP, TNC, TLR4 and ST2) we validated ST2 as significantly elevated in the serum of DMD cardiomyopathy group (35,798±4884pg/mL) compared to normal controls (9940±2680pg/mL; p<0.01; n=6). Matrix metallopeptidase 9 (MMP9) levels were found significantly increased in both DMD groups compared to controls (p<0.01). No significant differences were seen in BNP, GAL3, CRP, LEP, TNC or TLR4 levels. Increased ST2 levels were found in serum of DMD subjects compared to healthy volunteers and further elevated in DMD subjects with cardiomyopathy. Future studies correlating cardiomyopathy with ST2 levels may allow for improved non-invasive monitoring of cardiac disease in DMD subjects.

Increased constitutive nitric oxide production by whole body periodic acceleration ameliorates alterations in cardiomyocytes associated with utrophin/dystrophin deficiency

Duchenne Muscular Dystrophy (DMD) cardiomyopathy is a progressive lethal disease caused by the lack of the dystrophin protein in the heart. The most widely used animal model of DMD is the dystrophin-deficient mdx mouse; however, these mice exhibit a mild dystrophic phenotype with heart failure only late in life. In contrast, mice deficient for both dystrophin and utrophin (mdx/utrn−/−, or dKO) can be used to model severe DMD cardiomyopathy where pathophysiological indicators of heart failure are detectable by 8–10weeks of age. Nitric oxide (NO) is an important signaling molecule involved in vital functions of regulating rhythm, contractility, and microcirculation of the heart, and constitutive NO production affects the function of proteins involved in excitation-contraction coupling. In this study, we explored the efficacy of enhancing NO production as a therapeutic strategy for treating DMD cardiomyopathy using the dKO mouse model of DMD. Specifically, NO production was induced via whole body periodic acceleration (pGz), a novel non-pharmacologic intervention which enhances NO synthase (NOS) activity through sinusoidal motion of the body in a headward-footward direction, introducing pulsatile shear stress to the vascular endothelium and cardiomyocyte plasma membrane. Male dKO mice were randomized at 8weeks of age to receive daily pGz (480cpm, Gz±3.0m/s2, 1h/d) for 4weeks or no treatment, and a separate age-matched group of WT animals (pGz-treated and untreated) served as non-diseased controls. At the conclusion of the protocol, cardiomyocytes from untreated dKO animals had, respectively, 4.3-fold and 3.5-fold higher diastolic resting concentration of Ca2+ ([Ca2+]d) and Na+ ([Na+]d) compared to WT, while pGz treatment significantly reduced these levels. For dKO cardiomyocytes, pGz treatment also improved the depressed contractile function, decreased oxidative stress, blunted the elevation in calpain activity, and mitigated the abnormal increase in [Ca2+]d upon mechanical stress. These improvements culminated in a significant reduction in circulating cardiac troponin T (cTnT) and an extension of the median lifespan of dKO mice from 16 to 31weeks. Treatment with L-NAME (NOS inhibitor) significantly decreased overall lifespan and abolished the cardioprotective properties elicited by pGz. Our results provide evidence that enhancement of NO synthesis by pGz can ameliorate cellular dysfunction in dKO cardiomyocytes and may represent a novel therapeutic intervention in DMD cardiomyopathy patients.

Increased blood pressure and BMI in relation to cardiomyopathy in Duchenne muscular dystrophy

Objective: Cardiomyopathy in Duchenne muscular dystrophy (DMD) is characterized by progressive left ventricle dysfunction (LVD). LVD is worsened by increased left ventricular afterload. We studied factors influencing this afterload: systolic blood pressure (SPB), obesity, steroid use and cardiac medication (CM) in DMD patients. Subsequently, we studied the relation between these factors and LV deformation in a subset of young patients without clinical cardiomyopathy. Methods: SBP measurements were evaluated retrospectively from 285 visits of 65 patients aged 4–18 years between February 2003 and December 2016. Values were normalized for age and length using Z-scores (Z-SBP). Age was divided in 14 groups, from 4–5 to 17– 18 years. A linear mixed model was used to analyse longitudinal correlations between Z-SBP and body mass index (BMI), steroid use, age, ambulatory status and CM use. In a subset of 36 patients <11 years, LV deformation, defined by global longitudinal strain (GLS), was quantified with speckle tracking imaging in the apical 4-chamber view of transthoracic echocardiograms. Multiple linear regression was used to assess relations between GLS, BMI, SBP, age and years on steroids. Results: Median follow-up time was 5 years (range 1–12). Z-SBP was significantly elevated in all age groups under 14 years (p < 0.016) and 15–16 years (p = 0.014). Prevalence of hypertension (Z-SBP ≥ 1.65) ranged from 22–39%. Z-SBP correlated positively with BMI (p = 0.001), and negatively with CM use over time (p = 0.017). Mean age of the younger cohort was 8.5 (±1.5) years. Here, reduced GLS was associated with increased BMI (p = 0.004, R2 = 30.8%), but not with other variables. Conclusion: SBP was significantly elevated in the majority of DMD age groups below 18 years. Z-SBP correlated positively with BMI over time. BMI was also associated with decreased LV deformation in younger patients. Prospective studies are needed for confirmation, and to assess the relevance of earlier management of these factors in DMD.

Eplerenone for early cardiomyopathy in Duchenne muscular dystrophy: results of a two-year open-label extension trial

BackgroundCardiomyopathy is a leading cause of morbidity and mortality in boys with Duchenne muscular dystrophy (DMD). We recently showed in a 12-month double-blind randomized controlled trial that adding eplerenone to background medical therapy was cardioprotective in this population. The objective of this study was to evaluate the safety and efficacy of longer-term eplerenone therapy in boys with DMD.ResultsEleven subjects (phase 1 baseline median [range] age: 13 [7 – 25] years) from the original 12-month trial at a single participating center were enrolled. Importantly, those who entered the extension study who had been on eplerenone previously were significantly older than those who had originally been on placebo (median age 10.5 vs. 18.0 years, p = 0.045). During an additional 24-month open-label extension study, all boys received eplerenone 25 mg orally once daily to treat preclinical DMD cardiomyopathy, defined as evident myocardial damage by late gadolinium enhancement cardiac magnetic resonance (LGE) with preserved ejection fraction (EF). The threshold for potassium level, the primary safety measure, was not exceeded in any non-hemolyzed blood sample. Over 24 months, left ventricular (LV) systolic strain, a more sensitive marker whose more negative values indicate greater contractility significantly improved (median change -4.4%, IQR -5.8 to -0.9%) in younger subjects whereas older subjects’ strain remained stable without significant worsening or improvement (median change 0.2%, IQR -1.1 to 4.3%). EF and extent of myocardial damage by LGE remained stable in both groups over 2 years.ConclusionsEplerenone offers effective and safe cardioprotection for boys with DMD, particularly when started at a younger age. Eplerenone is a useful clinical therapeutic option, particularly if treatment is initiated earlier in life when cardiac damage is minimal.Trial registrationhttp://ClinicalTrials.gov identifier NCT01521546. Registered 26 January 2012.

Cardiac function of children with Duchenne muscular dystrophy

Background:Duchenne muscular dystrophy (DMD) is the most common childhood form of muscular dystrophy. Clinical guidelines recommend that evaluations for cardiomyopathy, arrhythmia, and heart failure be performed upon diagnosisThe incidence of cardiomyopathy in DMD increases with age Early detection of muscular dystrophy associated cardiomyopathy is important, because institution of cardioprotective medical therapies may slow adverse remodeling and attenuate heart failure symptoms in these patients. Aim: evaluation of cardiac function in children clinically suspected to have Duchenne muscular dystrophy. Methods:28 male children who met criteria for diagnosis of Duchenne muscular dystrophy aged from 3 to 18 years compared to 47 healthy control children were approached to participate in the study and, after consent, were submitted to full clinical examination, blood samples were collected to determinate CPK (creatinine phosphokinase), Troponin I enzyme, Myoglobin and LDH (lactate dehydrogenase) enzyme level,echocardiography and 12-lead electrocardiogram were done. Results: 28 Duchenne muscular dystrophy children and 47 age matched healthy male control children were included in the study. The mean age of study group was 7.29±3.24 years, and the mean age of the control group was 8.06±2. 86 years (p value 0 .28). 25% of cases had Positive family history of DMD. 35.7% of cases had positive consanguinity.all our cases had elevated CPK level (creatine phosphokinase) .The mean CPK level of cases was 2495.79 ± 3457.02 While CPK level in controls was normal, (p value<0.0001). LDH level was elevated in 19 cases 67.86% of cases. The mean serum LDH level in DMD cases was 1232.07 ± 617.72. All control children have normal LDH level with mean 163.02 ± 109.62, (P value : <0.0001).The mean serum myoglobin level of (DMD) patients was higher relative to that of healthy controls (but still within normal limits) 39.39 ± 7.25 versus 33.68 ±12.38 (ng/ml) respectively with statistically significant difference (P value: 0.01).There was no statistically significant difference between mean serum troponin I level of DMD patients and that of controls 0 .03 ± 0.05 versus 0.01 ±0 .02 (U/L) respectively (p value: 0.37). Echocardiography of our patients revealed that one patient (3.57%) had mild dilation of the left ventricular cavity which was statistically not significant, (P value: 0.37).7 cases (25%) of patients had low Ejection fraction (EF) and fraction shortening (FS) with mean (EF) 59.86 ± 10.20. All control children have normal EF with mean 73.30 ± 5.08 (P value : <0.0001). The mean FS was 20.29±5.59. All control children had normal (FS) with mean ±SD 36.17± 2.58 (P value : <0.0001). Electrocardiogram showed 28.57% of cases had sinus tachycardia with average heart rate (HR) 107 ±12.32 136. While 6.88% of controls had sinus tachycardia; (P value: 0.0001). Prolonged QTc interval was present in39.29% of cases with a mean of 431.39 ± 43.60 and that of controls was 415.17±25.2 (p value : <0.0001). QTc duration of controls were normal for age. Other parameters of ECG were normal for age; no type of arrhythmia could be detected apart from sinus tachycardia. Conclusion:ECG manifestations in children with DMD in the form of sinus tachycardia and prolonged QTC interval are an early alarm for developing cardiomyopathy before overt echocardiographic findings appear

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.