Mechanisms Underlying Iron Deficiency-Induced Cardiac Disorders: Implications for Treatment.

Abstract

Two billion people worldwide suffer from anemia, which can lead to the onset of cardiac disorders; nevertheless, the precise mechanisms remain unclear. There are at least three distinct mechanisms by which iron deficiency (ID) contributes to the development of cardiac disorders. First, ID increases concentrations of intact fibroblast growth factor-23 (iFGF-23), which promotes left ventricular hypertrophy. Additionally, individuals with ID typically have low circulating levels of vitamin D and an increased body burden of cadmium (Cd). Both factors-high Cd levels and a lack of vitamin D-elevate the risk of various cardiac disorders. Cd is transported in the body via transferrin and as non-transferrin-bound cadmium (NTBCd), with around 50% carried by transferrin. Transferrin-bound Cd is internalized into cells through the transferrin receptor 1 (TfR1), whereas NTBCd uptake occurs via receptors involved in iron transport, such as divalent metal transporter 1 (DMT1), ZIP8, and ZIP14. These receptors, expressed in tissues like the myocardium, contribute to Cd accumulation in the heart. In cases of coronary artery disease, regions of the heart affected by hypoxia, due to reduced blood flow, overexpress TfR1, DMT1, ZIP8, and ZIP14. This increases the uptake of Cd into cardiomyocytes. Cd, once inside the cells, damages mitochondria through oxidative stress, lipid peroxidation, and DNA alterations, leading to cell death. Once destroyed, cardiomyocytes release intracellular potassium which can potentially cause fatal arrhythmia. Cardiac iron bioaccumulation is primarily influenced by two factors: blood iron concentrations and the density of TfR1. Numerous studies have explored the potential benefits of iron supplementation, with varying results. We hypothesize that the extent of beneficial effects from iron supplementation may depend on the presence of specific comorbidities, such as chronic kidney disease or hyperaldosteronism. This hypothesis is based on the observation that certain hormones, including aldosterone and noradrenaline, downregulate the expression of TfR1. Therefore, we propose that co-treatment with iron and aldosterone antagonists could enhance cardiac iron uptake and improve the overall effectiveness of the therapy. Additionally, vitamin D supplementation prior to the onset of disease and chelation therapy after diagnosis could provide some benefits.