MiR‐133a Mitigates Ferroptosis by Attenuating Fatty Acid Metabolism in the Diabetic Heart

Abstract

Background/hypothesis of the studyMyocardial lipid accumulation occurs prior to the development of cardiac dysfunction in patients with diabetes mellitus (DM). miR‐133a prevents DM‐induced myocardial lipid deposition and is decreased in the DM heart, however its cardioprotective mechanisms remain unknown. Ferroptotic cell death which results from an increase in lipid peroxidation combined with a failure of lipid‐antioxidant mechanisms in the presence of iron, is upregulated in the DM heart. Thus, we hypothesize that overexpression of miR‐133a protects against ferroptotic cell death via inhibition of lipid accumulation, leading to decreased lipid peroxidation in the DM heart. We developed a novel Akita/miR‐133aTg (Ak/Tg) mouse model by crossbreeding DM Akita (Ak) with cardiac specific miR‐133a Tg (Tg) to elucidate how miR‐133a regulates ferroptotic cell death in the DM heart.Methods and ResultsDeep sequencing analysis revealed that miR‐133a activated fatty acid oxidation in the DM heart (p‐value=4.59E‐11). Protein levels of transcription factor Peroxisome proliferator‐activated receptor gamma (PPARG) (WT: 0.195±0.012, Ak: 0.23±0.012, Ak/Tg: 0.173±0.009, Tg: 0.16±0.012) and its coactivator Peroxisome proliferator‐activated receptor‐gamma coactivator (PGC‐1α) (WT: 0.162±0.006, Ak: 0.224±0.012, Ak/Tg: 0.149±0.011, Tg: 0.145±0.010). Furthermore, citrate synthase activity was increased in the presence of miR‐133a (WT: 0.793±0.043, Ak: 0.735±0.026, Ak/Tg: 0.994±0.055, Tg: 0.929±0.018), implying an increase of lipid clearance. Protein levels of glutathione peroxidase (GPX4), an antioxidant that inhibits the production of peroxidized lipids, were increased by the presence of miR‐133a (WT: 0.038±0.003, Ak: 0.024±0.002, Ak/Tg: 0.040±0.004, Tg: 0.030±0.006). miR‐133a also decreased levels of DM‐induced peroxidized lipids (WT: 203.9±12.69, Ak: 231.9±7.252, Ak/Tg: 209.8±8.885, Tg: 251.9±14.26).ConclusionsThese data support that miR‐133a decreases myocardial lipid deposition via increased lipid metabolism while simultaneously increasing levels of lipid antioxidant GPX4, leading to lower levels of peroxidized lipids resulting in the mitigation of ferroptotic cell death in the DM heart.