Comprehensive proteomics profiling reveals molecular pathways that are differentially regulated in hypertrophic cardiomyopathy and correlate with clinical markers of disease severity
Authors: Shimada Y J , Raita Y , Liang L W , Maurer M S , Hasegawa K , Fifer M A , Reilly M P 
Published: October 2021

Abstract

Background
Hypertrophic cardiomyopathy (HCM) is caused by mutations in the genes coding for proteins essential in normal myocardial contraction. However, it remains unclear through which molecular pathways gene mutations mediate the development and progression of HCM.

Purpose
To determine protein biomarkers and molecular pathways that are differentially regulated in HCM and correlated with disease severity.

Methods
We conducted a multicenter case-control study of cases with HCM and controls with hypertensive left ventricular hypertrophy. We carried out plasma proteomics profiling of 1681 proteins using the SOMAscan assay. We performed a sparse partial least squares discriminant analysis to develop a proteomics-based discrimination model with data from 1 institution (i.e., the training set). We tested the discriminative ability in independent samples from the other institutions (i.e., the test set). We executed pathway analysis using significantly dysregulated proteins with Bonferroni-corrected p&lt;0.05. Pathways with false discovery rate (FDR) &lt;0.05 and dysregulation of ≥5 member proteins were declared positive. In HCM, we also identified proteins with significant correlation with clinical markers of disease severity (e.g., New York Heart Association [NYHA] class, left atrial diameter) and performed pathway analysis.

Results
The study included 266 cases and 167 controls (n=308 in the training set; n=125 in the test set). Using the proteomics-based model derived from the training set, the area under the receiver-operating-characteristic curve was 0.89 (95% confidence interval [CI] 0.83–0.94, p&lt;0.001) in the test set (Figure). The sensitivity was 0.84 (95% CI 0.76–0.92) and the specificity was 0.78 (95% CI 0.66–0.90). A total of 508 proteins were significantly associated with the disease status. As shown in the Table, pathway analysis revealed that the Ras-MAPK pathway, along with its upstream and downstream (e.g., Rap1, PI3K-Akt) pathways, was upregulated in HCM (FDR &lt;0.001). Pathways involved in inflammation and fibrosis – e.g., the TGF-β pathway – were also found to be upregulated in HCM. In patients with HCM, 207 out of the 1681 proteins were significantly correlated with NYHA functional class. This number is more than twice as large as what would be expected by chance (i.e., 84 proteins at α=0.05 level). Pathway analysis of these 207 proteins showed upregulation of the Ras-MAPK and related pathways – e.g., PI3K-Akt, Rap1, and TNF. Similarly, 264 of the 1681 proteins were correlated with left atrial diameter in HCM. Pathway analysis of the 264 proteins revealed upregulation of the MAPK and the PI3K-Akt pathways.

Conclusions
This multicenter case-control study with independent validation serves as the largest-scale investigation with the most comprehensive proteomics profiling in HCM, exhibiting both novel (e.g., Ras-MAPK) and known (e.g., TGF-β) pathways that are differentially regulated in HCM and correlated with disease severity.

Funding Acknowledgement
Type of funding sources: Public grant(s) – National budget only. Main funding source(s): National Institute of Health and American Heart Association Figure 1. ROC curveTable 1. Differentially regulated pathways