Grant: Travel Awards - Institute Community Support

Inadequate supply of iron can elicit health defects yet there is also strong evidence that too much iron causes detrimental cellular effects. Accordingly, disturbed iron homeostasis is associated with various pathological conditions, including diabetes and heart failure. We contend that disturbed iron homeostasis is an important and underappreciated contributor to development of heart failure. To do so we hypothesized that iron induces cardiomyocyte insulin resistance via oxidative stress. In primary adult and neonatal cardiomyocytes as well as H9c2 cells, derived from rat heart ventricle, iron induced insulin resistance as determined by Western blotting and immunofluorescent detection of Akt phosphorylation. Using the CellROX Deep Red assay we also observed that iron increased generation of reactive oxygen species (ROS), and that anti-oxidant pre-treatment attenuated iron-induced insulin resistance. We used multiple assays to monitor autophagic flux and observed that iron suppressed autophagy. First, we determined LC3II and P62 levels by Western blotting. The increased autophagosome content was validated by an increase in puncta detected using the CytoID assay. To study the functional significance of changes in autophagy we created an autophagy-deficient cell model by overexpressing a dominant-negative Atg5 mutant in H9c2 cells and autophagy deficiency both induced insulin resistance. In conclusion, our study showed that iron overload reduced autophagy and stimulated ROS production, causing insulin resistance in cardiomyocytes. We anticipate that our findings will provide new knowledge relevant to current diagnostics and therapeutics related to altered iron status in clinical settings.