Effect of Ivabradine in dilated cardiomyopathy from Duchenne muscular dystrophy: A chance for slowing progression of heart failure?

Dilated cardiomyopathy contributes to morbidity and mortality in Duchenne Muscular Dystrophy (DMD), an inheritable muscle wasting disease caused by a mutation in the dystrophin gene. Preclinical studies in mouse models of muscular dystrophy have demonstrated reduced cardiomyopathy and improved cardiac function following oral treatment with the potent and selective thromboxane A2/prostanoid receptor (TPr) antagonist, ifetroban. Further, a phase 2 clinical trial (NCT03340675, Cumberland Pharmaceutical) is currently recruiting subjects to determine if ifetroban can improve cardiac function in patients with DMD. Although TPr is a promising therapeutic target for the treatment of dilated cardiomyopathy in DMD, little is known about TPr function in coronary arteries that perfuse blood through the cardiac tissue. In the current study, isolated coronary arteries from young (~3-5 months) and aged (~9-12 months) mdx mice, a widely used mouse model of DMD, and age-matched controls were examined using wire myography. Vasoconstriction to increasing concentrations of TPr agonist U-46619(U4) was enhanced in young mdx mice versus controls. Additionally, young mdx mice displayed a significant attenuation in endothelial cell-mediated vasodilation to increasing concentrations of the muscarinic agonist acetylcholine (ACh). Since TPr activation was enhanced in young mdx mice, U4-mediated vasoconstriction was measured in the absence and presence of ifetroban. Ifetroban reduced U4-mediated vasoconstriction in young mdx and both aged mdx and control mice. Overall, our data demonstrate enhanced coronary arterial vasoconstriction to TPr activation in young mdx mice, a phenotype that could be reversed with ifetroban. These data could have important therapeutic implications for improving cardiovascular function in DMD.

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Abstract 468: Previously Unrecognized Intronic Variants in the Dystrophin Gene Identified as Possible Contributors to Dilated Cardiomyopathy

Circulation Research ◽

10.1161/res.127.suppl_1.468 ◽

2020 ◽

Vol 127 (Suppl_1) ◽

Author(s):

Alex Gyftopoulos ◽

Tamara Ashvetiya ◽

Yi-Ju Chen ◽

Libin Wang ◽

Charles H Williams ◽

...

Keyword(s):

Heart Failure ◽

Muscular Dystrophy ◽

Dilated Cardiomyopathy ◽

Allele Frequency ◽

Minor Allele Frequency ◽

Mixed Model ◽

Dystrophin Gene ◽

Becker Muscular Dystrophy ◽

Minor Allele ◽

Intronic Variants

Nonischemic dilated cardiomyopathy (DCM) often has a genetic etiology, however, its prevalence and etiologies are not completely understood. The UK Biobank comprises clinical and genetic data for greater than 500,000 individuals with enrollees 40-69 years of age. Our group created a custom phenotype of heart failure using ICD-10 codes for several subtypes of heart failure diagnoses including DCM. We then compared the individuals included in the custom heart failure phenotype to control individuals in a 20-to-1 fashion to identify genetic differences. Data were compared using Mixed Model Analysis for Pedigrees/Populations (MMAP) mixed-model regression. We identified 8 unlinked intronic variants in the dystrophin gene ( DMD ) that, when separated by self-identified race, occurred with a combined minor allele frequency of 0.15 in individuals with heart failure who identified as being of African descent. The combined minor allele frequency of these variants was 0.05 in individuals who self-identified as being of European descent. One variant of DMD in particular (rs139029250), was identified with a minor allele frequency of 0.05 in African British with DCM. The unadjusted odds ratio of a diagnosis of heart failure in individuals with rs129029250 was 4.65. When separated by gender, the unadjusted odds ratios are 2.02 for females and 6.44 for males. DMD is most notably known for its role in Duchenne and Becker muscular dystrophy, both of which are known to cause dilated cardiomyopathy in affected individuals. However, none of the individuals (36 female and 43 male) identified in our analysis with rs129029250 have been diagnosed with Duchenne muscular dystrophy, Becker muscular dystrophy, or a primary disorder of muscle (ICD code G70). Additionally, these individuals have an intronic variant of DMD , while Duchene and Becker muscular dystrophy are both due to exonic mutations. These findings suggest a possible common variant in the DMD gene that may contribute to DCM in individuals of African descent.

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