The relation among myocardial iron load and the severity of heart failure
Authors: Leszek P , Lewicki S , Kozlowska B , Sochanowicz B , Kolsut P , Szymanski L , Smigielski W , Kraj L , Kruszewski M , Zaleska-Kociecka M 
Published: October 2022

Abstract

Heart failure (HF) symptoms are related to reduced circulatory perfusion, peripheral congestion, also impaired peripheral muscle strength & oxygen utilization due to iron deficiency. Despite many premises, the correlation between myocardial iron load and failing heart function was not proved.
The purpose of this study was to assess iron itself and iron-related proteins in human failing (FH) vs non-failing (NFH) myocardium.
The study group consisted of 58 explanted FHs vs the control consisted of 31 NFHs unsuitable for transplantation. HF study group presented with LV dilatation (LVDD 67±8 mm; LVSD 59±13 mm), reduced contraction (LVEF 20±7.5%), RV enlargement (RVD 42±6.5 mm), pulmonary hypertension (2.21±0.93 Wu) and elevated NTproBNP (3955.5±2250.5pg/ml).
We assessed iron serum markers: ferritin (FR), transferrin/saturation (TSAT), transferrin receptor (soluble sTfR), sTFR/log FR; myocardial iron homeostasis assessment: M-Iron (Instrumental Neutron Activation Analysis, μg/g) and iron gathering proteins (by ELISA): divalent metal transporter (DMT-1); L-type calcium channel (L-CH), TfR-1/TfR-2; ferritins: heavy (FT-H), light (FT-L) chain, mitochondrial (FT-MT); ferroportin (FPN) and oxidative stress marker: 4-hydroxynonenal (4-HNE).
In FH vs NFH, M-Iron was reduced (164.6±25.2 vs 182.3±23.9; p=0.0358) however, did not apply to the entire group. Therefore we divvied the FH group into two subgroups (based on M-Iron concentration in NFH controls). Average iron concertation in non-iron-deficient (NIDM) subgroup was 172.5±19.1 (n=35) and in iron-deficient (IDM) subgroup wad 127.0±16.5; (n=23, p=0.0001).
Regardless M-Iron load in FH vs NFH myocardial proteins expressions were reduced: L-CH (NIDM vs IDM vs NFH: 49.2±9.2; 42.5±4.2; 67.3±23.0, p=0.0022); FT-L (16.4±7.3; 11.6±4.8; 26.3±7.5, p= &lt;0.0001, respectively); FT-MT (41.2±7.6; 38.7±4.1; 59.3±10.4 p≤0,0001, respectively). With regard to M-Iron load, only in DMT-1 expression was changed (NIDM vs IDM vs NFH 4.8±0.7; 4.0±0.5; 5.8±0.8; p≤0.0001). 4-HNE levels in FH vs NFH were increased, regardless M-Iron load (NIDM-Iron vs IDM-Iron vs NFH; 55.7±29.2; 57.2±47.8; 9.9±8.1 p≤0.0001).
Interestingly, the iron load (NIDM-Iron vs IDM-Iron) did not modify the assessed clinical parameters.
With regard to commonly used systemic iron markers only sTFR/log FR proved M-Iron load difference (NIDM-Iron vs IDM-Iron 0.6±0.2; 0.7±0.3; p=0.047910)
In FH, we observed, the subgroup with the reduced M-Iron load. The observed reduction of iron gathering proteins were independent on M-Iron load, except DMT-1 the main iron transportation protein into the cell. The results showed that the HF degree and concertation of iron proteins are unlikely to be affected by the M-Iron load, except DMT-1 protein. The oxidative stress was also regardless from M-Iron load, and increased in the whole FH group. Commonly used systemic iron markers except sTFR/log FR did not define M-Iron load.

Funding Acknowledgement
Type of funding sources: Public Institution(s). Main funding source(s): The Cardinal Stefan Wyszyński National Institute of Cardiology