Abstract Body (Do not enter title and authors here): Background:
Duchenne muscular dystrophy (DMD) is an X-linked, progressive neuromuscular disorder characterized by cardiac and skeletal myopathy. The cardiac and skeletal muscle manifestations have different ages of onset and rates of progression, suggesting variability in the pathophysiology of dystrophin loss within the respective muscle groups.

Hypothesis
We hypothesized that proteomics with comprehensive clinical phenotyping would identify novel biomarkers that correlate with cardiac but not skeletal disease progression in boys with DMD.

Methods:
This single-center cohort study of 56 DMD subjects performed cardiac magnetic resonance (CMR), including left ventricular ejection fraction (LVEF), late gadolinium enhancement (LGE), and myocardial circumferential strain (ECC). Fifty-one subjects underwent quantitative muscle testing, and 33 underwent actigraphy (MSK indices). Aptamer-based technology (SomaScan, SomaLogic, Boulder, CO) evaluated 1128 proteins in plasma sampled at the time of CMR. Correlations between serum protein levels and cardiac or MSK indices were tested using Benjamini-Hochberg corrected p-values (q-values).

Results:
The mean age of DMD subjects was 15.5 years old +/- 4.30. Twenty-six subjects had left ventricular dysfunction (LVEF <55%), 45 subjects had LGE, and 45 were non-ambulatory. Of 1128 proteins analyzed, 208 demonstrated a significant correlation for cardiac but not MSK indices (Figure 1). Figure 2 lists the 20 proteins with the strongest correlations, which included biomarkers of inflammation, calcium regulation in myocytes, and cell adhesion.

Conclusion:
We detected 208 novel proteins that correlate with cardiac-specific DMD disease progression. These proteins provide a better understanding of the underlying differences of cardiac disease, compared to MSK disease in DMD and provide clues to potential cardiac therapeutic options.