NRF2 activation in the heart induces glucose metabolic reprogramming and mediates cardioprotection via upregulation of the pentose phosphate pathway.

RationaleThe transcription factor NRF2 is well recognized as a master regulator of antioxidant responses and cytoprotective genes. Previous studies showed that NRF2 protects mouse hearts during chronic hemodynamic overload at least in part by reducing oxidative stress. Evidence from other tissues suggests that NRF2 may modulate glucose intermediary metabolism but whether NRF2 has such effects in the heart is unclear. ObjectiveTo investigate the role of NRF2 in regulating glucose intermediary metabolism and cardiac function during disease stress. Methods and ResultsCardiomyocyte-specific Keap1 knockout (csKeap1KO) mice, deficient in the endogenous inhibitor of NRF2, were used as a novel model of constitutively active NRF2 signaling. Targeted metabolomics and isotopomer analysis were employed in studies with 13C6-glucose in csKeap1KO and wild-type (WT) mice. Pharmacological and genetic approaches were utilized in neonatal rat ventricular cardiomyocytes (NRVM) to explore molecular mechanisms. We found that cardiac-specific activation of NRF2 upregulated key enzymes of the Pentose Phosphate Pathway (PPP), redirected glucose metabolism towards the PPP and protected the heart against pressure overload-induced cardiac dysfunction. In vitro, knockdown of Keap1 upregulated PPP enzymes and reduced cell death in NRVM subjected to chronic neurohumoral stimulation. These pro-survival effects were abolished by pharmacological inhibition of the PPP or silencing of the PPP rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD). Knockdown of NRF2 in NRVM increased stress-induced DNA damage which was rescued by supplementing the cells with either NADPH or nucleosides, the two main products of the PPP. Activation of NRF2 also protected the heart against myocardial infarction-induced DNA damage, dysfunction, and adverse remodeling. ConclusionsThese results indicate that NRF2 regulates cardiac metabolic reprogramming by stimulating the diversion of glucose into the PPP, thereby providing cardiac protection during stress by generating NADPH and providing nucleotides to prevent stress-induced DNA damage.