Journal Article

125 Post-genomic atrial and ventricular myocardial proteome of end-stage lamin heart disease: a prospective clinical trial

Chan, Fiona, O’Brien, Benjamin, Shiwani, Hunain, Steeds, Richard, Captur, Gabriella, Mohiddin, Saidi A, Syrris, Petros, Coats, Caroline, Alfarih, Mashael, Topriceanu, Cristian, Moon, James, Hughes, Alun D, Pettit, Stephen, Arbustini, Eloisa, Moody, William, Vowinckel, Jakob

2023

Overview

BackgroundLamins A/C (encoded by the LMNA gene) can lead to dilated cardiomyopathy (DCM). LMNA DCM to be ranked clinically as one of the most dreaded forms of DCM because of its high propensity for sudden cardiac death and advanced heart failure. However, lamin heart disease (LHD) remains to be poorly understood. Thus, this study sought to undertake proteomic analysis of myocardial tissue to explore the postgenomic phenotype of end-stage lamin heart disease.MethodsThis prospective clinical trial (NCT03860454) enrolled consecutive patients with end-stage LHD (LMNA-group, n=7) and ischaemic DCM (ICM-group, n=7) who were undergoing heart transplantation. For comparison, samples from healthy unused control donor hearts (CTRL, n=6) collected from the University of Sydney Heart Bank were also included. Samples were obtained from left atrium (LA), left ventricle (LV), right atrium (RA), right ventricle (RV) and interventricular septum (IVS). Liquid chromatography combined with mass-spectrometry (MS) was used to quantify protein concentrations. We compared protein concentrations in cardiac samples between LMNA and ICM groups. Proteins were considered differentially abundant if two simultaneous criteria were met: (1) there was a 1.5-fold increase/decrease, and (2) the p-value passed the correction for multiple testing at a false discovery rate of 0.01 (i.e., q-value<0.05). Given the slight differences in MS methodologies, only qualitative comparisons were made with the CTRL group. Gene ontology (GO) enrichment analysis explored the related biological processes. Biological processes, cellular components and molecular function GO categories with >2 members were considered.ResultsParticipant characteristics are presented in Table 1. 4,247 proteins were identified in LMNA and ICM samples, of which 633 were differentially abundant in LA, 39 in LV, 181 in RA, 52 in RV, and 85 in IVS (Table 2). The top 25 differentially abundant proteins ranked by q-value are presented using volcano plots in Figure 1. Abundance of lamin A/C was reduced but lamin B (LMNB) increased in LMNA LA/RA tissue compared to ICM, but not in LV/RV, with lamin B being absent in CTRL septal samples. Across all tissue samples, ECM proteins levels were differently abundant with pro-fibrotic fibrillar proteins being found at higher levels. Transthyretin was more abundant in the LV/RV of LMNA compared to ICM while sarcomeric proteins such as titin and cardiac myosin heavy chain were generally reduced in RA/LA of LMNA. In RV/LV, glycolysis enzymes and sarcoendoplasmic reticulum calcium-binding proteins appeared to be decreased. Protein expression profiling and GO enrichment analysis revealed sarcopenia, extracellular matrix (ECM) remodeling, deficient myocardial energetics, redox imbalances, and abnormal calcium handling in LMNA samples. For LV, box plots comparing the intensities of the top 25 differentially abundant proteins between LMNA and ICM based on q-value, and the top 20 enriched biological processes are presented in Figure 2.ConclusionLHD is a biventricular and biatrial disease, characterized by sarcopenia, aberrant metabolism, and ECM remodeling. LMNB and transthyretin were unexpectedly abundant in the atria and ventricles respectively of patients with end-stage lamin heart disease potentially hinting to the possibility of compensatory responses.Abstract 125 Table 1Participant characteristics LMNA (n=7) ICM (n=7) p-value* Demographics Age, years42 (39.0, 43.4)52 (48.0, 60.5)0.306Sex, Males4 (57.1%)6 (85.7%)0.554Body Mass Index (kg/m2)28.5 (26.0, 29.3)26.1 (24.5, 28.7)0.699Ethnicity, White5 (71.4%)4 (57.1%)0.503 Co-morbidities High cholesterol, yes1 (14.3%)3 (42.9%)0.306Diabetes, yes1 (14.3%)2 (28.6%)1.00Atrial Fibrillation, yes5 (71.4%)1 (14.3%)0.105 Echocardiography LVIDd, mm60 (57.0, 62.0)58.0 (51.0, 62.0)0.807IVSd thickness, mm8.4 (7.9, 8.5)8.1 (8.0, 8.3)0.807Ejection Fraction (%)24.3 (14.5, 32.3)24.0 (20.3, 25.6)0.876LV mass (grams)173.2 (161.1, 205.2)209.0 (143.9, 209.9)1.00Medial E/e’15.8 (11.6, 24.5)15.0 (12.0, 18.1)0.659TAPSE, cm1.7 (1.2, 1.8)1.5 (1.4, 1.7)0.679*Reported p values were derived using Mann Whitney U-test, χ2 or Fisher’s exact test as appropriate.d, diastolic; IVS, interventricular septum; LV, left ventricle; LVID, LV internal diameter; TAPSE, tricuspid annular plane systolic excursion. Abstract 125 Table 2Contingency table showing number of differentially abundant proteins between heart regions (RA, RV, LA, LV, IVS) and between groups (LMNA, ICM) LA_ICM LA_LMNA LV_ICM LV_LMNA RA_ICM RA_LMNA RV_ICM RV_LMNA IVS_ICM IVS_LMNA LA_ICM N/A 633 156185307443194224318242 LA_LMNA N/A721723177838489481053952 LV_ICM N/A 39 530779396413277 LV_LMNA N/A484769592816633 RA_ICM N/A 181 639715838685 RA_LMNA N/A9099481077944 RV_ICM N/A 52 6747 RV_LMNA N/A11610 IVS_ICM N/A 85 IVS_LMNA N/AAbstract 125 Figure 1Volcano plots of differentially expressed proteins.Proteins in the (A) right atrium, (B) left atrium, (C) right ventricle, (D) left ventricle and (E) interventricular septum differentially abundant between LMNA and ICM samples. Only the top 25 differentially expressed proteins ranked by q-value are annotated in red in these volcano plots.ICM, ischaemic dilated cardiomyopathy; IVS, interventricular septum; LA, left atrium; LMNA, lamin; log, logarithm; LV, left ventricle; RA, right atrium; RV, right ventricle.Abstract 125 Figure 2Left ventricular myocardial proteins and their gene ontology.A. Box plots comparing intensities of the top 25 LV proteins between LMNA and ICM based on q-value. Genes coding for the proteins rather than the proteins themselves are named.B. The top 20 enriched biological processes across the 39 proteins differentially abundant in the LV myocardium of LMNA and ICM, are presented in the rightmost panel. The raw (red), Benjamini-Hochberg corrected (green) and Bonferroni corrected enrichment p-values are displayed in the leftmost panel. Fold enrichment is shown in the middle panel.Abbreviations as in Figure 2.Conflict of InterestNone

• Publisher: BMJ Publishing Group Ltd and British Cardiovascular Society,BMJ Publishing Group LTD
• Subject: Cardiomyopathy / Cardiovascular disease / Clinical trials / compensatory expression / Heart / Heart Failure / Ischemia / lamin heart disease / Ontology / Proteins / remodeling / Sarcopenia