Fumarate Is Cardioprotective via Activation of the Nrf2 Antioxidant Pathway

The citric acid cycle (CAC) metabolite fumarate has been proposed to be cardioprotective; however, its mechanisms of action remain to be determined. To augment cardiac fumarate levels and to assess fumarate's cardioprotective properties, we generated fumarate hydratase (Fh1) cardiac knockout (KO) mice. These fumarate-replete hearts were robustly protected from ischemia-reperfusion injury (I/R). To compensate for the loss of Fh1 activity, KO hearts maintain ATP levels in part by channeling amino acids into the CAC. In addition, by stabilizing the transcriptional regulator Nrf2, Fh1 KO hearts upregulate protective antioxidant response element genes. Supporting the importance of the latter mechanism, clinically relevant doses of dimethylfumarate upregulated Nrf2 and its target genes, hence protecting control hearts, but failed to similarly protect Nrf2-KO hearts in an in vivo model of myocardial infarction. We propose that clinically established fumarate derivatives activate the Nrf2 pathway and are readily testable cytoprotective agents. ► Cardiac fumarase deletion (cFH1-KO) results in mice with elevated cardiac fumarate ► cFH1-KO is compensated for by amino acid influx into the citric acid cycle ► Nrf2 and its target genes are activated in the hearts of cFH1-KO mice ► Fumarate-related Nrf2 activation is cytoprotective and may be of therapeutic use