Novel Biomarkers for Heart Failure: A Proteomic Approach

Heart failure (HF) is clinical syndrome growing in economic burden worldwide as it is difficult to diagnose due to its multiple aetiologies and comorbidities, it is expensive to treat and has poor patient outcomes. Even with improvements in therapy and diagnostic methods, heart failure still affects over 500, 000 individuals in the UK alone. The main aim of this project was to identify novel protein biomarkers that predict HF prognosis in heart failure patients that have received optimal therapy for one year. Extracellular vesicle (ECV) and Calcium Silicate Matrix (CSM) enrichment methods were employed to isolate low and mid abundance proteins in these patient samples. Parallel Reaction Monitoring (PRM) with heavy labelling and Selected Reaction Monitoring (SRM) with surrogate peptides were then used to detect and semi-quantitate these proteins using peptides unique to each protein. This is the first time, to our knowledge that PRM with heavy labelling or SRM with surrogate peptides have been used for the identification and relative quantification of peptides for the discovery of biomarkers in HF samples.

Limma analysis of proteins detected using SRM with surrogate peptides identified seven peptides (representing seven proteins) that were differentially expressed between the patient samples observed in this study (FDR < 0.05). Five of these proteins were differentially expressed in both discovery work using data independent acquisition and targeted work using SRM in this project. These five proteins are the final panel of potential biomarkers identified in this project and are candidate biomarkers for heart failure: Apolipoprotein M, Apolipoprotein C-III, Fermitin family homolog 3, Antithrombin-III and Vitronectin. To establish these five proteins as true predictors of prognosis in heart failure patients, future work is required such as absolute quantification of these five proteins using stable isotope labels.