ANALYSIS OF PLASMA PROTEIN AGGREGATION FROM PATIENTS WITH HEART FAILURE WITH PRESERVED EJECTION FRACTION

Objective: To compare the structural conformation of circulating protein aggregates and the levels of SDS-resistant protein aggregates between patients with heart failure with preserved ejection fraction (HFpEF) and age-matched individuals. Design and method: Ten adults were recruited, five patients with HFpEF (age: 70.0 ± 3.2 years, FEVE: 58.0 ± 7.5%, NT-proBNP: 1039.4 ± 530.7 pg/mL, BMI: 33.2 ± 5.6 kg/m2, SBP: 142.0 ± 23.5 mmHg, DBP: 74.6 ± 9.3 mmHg) and five age-matched individuals with cardiovascular risk factors (70.6 ± 2.7 years, BMI: 32.8 ± 2.8 kg/m2, SBP: 38.5 ± 13.8 mmHg, DBP: 81.6 ± 6.6 mmHg). SDS detergent-insoluble protein aggregates were analysed in plasma pre-cleared from albumin and immunoglobulin, by diagonal two-dimensional electrophoresis. Fourier-transform infrared spectroscopy (FTIR) was used to assess plasma proteins’ secondary structures, particularly the ones related with high aggregation propensity. Results: Our results indicate that HFpEF patients have similar plasma levels of SDS-resistant protein aggregates to those of age-matched participants (29.6 ± 6.4 vs. 35.0 ± 3.9%, p = 0.153). However, HFpEF patients with lower VO2peak and higher NT-proBNP generally presented higher level of protein aggregates. FTIR multivariate analysis of the amide region I (1700–1600 cm-1), which is directly related to proteins secondary structures, allowed to discriminate HFpEF from age-matched group. Partial Least Square Regression (PLS-R) to this spectra region showed that HFpEF patients exhibited strong vibrational peaks characteristic of protein aggregates (intermolecular beta-sheet (1625 cm-1), anti-parallel beta-sheet (1693 cm-1) and aggregate strands (1611 cm-1)); the age-matched individuals were characterized by a band containing alpha-helix structures (1653 cm-1), characteristic of a more stable conformation with less susceptibility to aggregation. Conclusions: The analysis of the protein aggregation profile by FTIR revealed that the plasma from HFpEF patients was characterized by the presence of secondary structures typical of protein aggregates. Although the fraction of detergent-insoluble aggregates was not different from the one of age-matched participants, our ongoing identification of proteins present in the aggregates, by mass spectrometry, will allow us to infer main molecular pathways involved in the progression of HFpEF.