Iron deficiency drives pathological cardiac remodeling and diastolic dysfunction associated with inhibition of AMPK-mTORC1 signaling.

BACKGROUND

Epidemiological evidence has established a strong association between iron deficiency (ID) and the exacerbation of heart failure (HF) and increased mortality. However, the molecular mechanisms by which iron deficiency drives cardiac diastolic dysfunction remain incompletely understood. This study aimed to elucidate the mechanism by which iron deficiency causes cardiac dysfunction through disruption of myocardial energy homeostasis and consequent impairment of heart function.

METHODS

An in vivo iron deficiency (ID) mouse model was established via phlebotomy combined with a low-iron diet, while an in vitro model was induced by treating H9C2 cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes (hiPSCCMs) with deferoxamine (DFO). Serum ferritin level was measured by enzyme-linked immunosorbent assay (ELISA). Cardiac function was assessed by echocardiography. Cardiomyocyte hypertrophy and myocardial fibrosis were evaluated using wheat germ agglutinin (WGA) and Masson's trichrome (MT) staining. Integrated transcriptomic sequencing (RNA-Seq) and targeted metabolomics analyses in DFO treated H9C2 cardiomyocytes were performed to identify key dysregulated pathways, which were further validated by Western blot and immunofluorescence. Mitochondrial function and energy production were quantified using the Seahorse XFe24 Extracellular Flux Analyzer.

RESULTS

After 250 to 300 μL blood withdrawal and low-iron diet treatment for 4 weeks, serum ferritin level was significantly lower in ID model group compared with the sham group. ID model displayed a cardiac diastolic dysfunction phenotype, as indicated by an increased ratio of early diastolic mitral inflow velocity to early diastolic mitral annular velocity (E/E' ratio), while left ventricular ejection fraction remained preserved. Histological analyses of mouse hearts revealed significant cardiomyocyte hypertrophy and interstitial fibrosis in ID model hearts. In vitro, multi-omics profiling in DFO treated H9C2 cells uncovered profound metabolic reprogramming induced by iron deficiency, characterized by suppressed mitochondrial oxidative phosphorylation and ATP production, accompanied by a compensatory shift toward glycolysis, ultimately leading to cellular energy depletion, evidenced by a marked reduction in oxygen consumption rate (OCR) and intracellular adenosine triphosphate (ATP) levels. The energetic stress activated AMPK, as evidenced by increased AMPKα phosphorylation, which in turn inhibited mTORC1 signaling. Consistently, phosphorylation of downstream mTORC1 effectors, including P70S6K, S6, and 4EBP1, was significantly reduced in left ventricular tissue, DFO-treated H9C2 cells and hiPSCCMs. Pharmacological inhibition of AMPK with Compound C rescued the impaired mTORC1 signaling.

CONCLUSIONS

Iron deficiency directly disrupts myocardial ATP production via the ATP-AMPK-mTORC1 axis, leading to pathological cardiac remodeling and diastolic dysfunction. These findings provide mechanistic insight into iron deficiency-related heart failure, highlighting metabolic signaling pathways as potential therapeutic targets.