NRF2 activation in the heart induces glucose metabolic reprogramming and reduces cardiac dysfunction via upregulation of the pentose phosphate pathway

The transcription factor nuclear factor erythroid–derived 2-like 2 (NRF2) is well recognized as a master regulator of antioxidant responses and cytoprotective genes. Previous studies showed that NRF2 enhances the resistance of mouse hearts to chronic haemodynamic 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. Here, we investigate the role of NRF2 in regulating glucose intermediary metabolism and cardiac function during disease stress.

Cardiomyocyte-specific Keap1 knockout (csKeap1KO) mice, deficient in the endogenous inhibitor of NRF2, were used as a novel model of constitutively active NRF2 signalling. Targeted metabolomics and isotopomer analysis were employed in studies with ¹³C₆-glucose in csKeap1KO and wild-type mice. Pharmacological and genetic approaches were utilized in neonatal rat ventricular myocytes (NRVMs) to explore molecular mechanisms. We found that cardiac-specific activation of NRF2 redirected glucose metabolism towards the pentose phosphate pathway (PPP), a branch pathway of glycolysis, and mitigated pressure overload-induced cardiomyocyte death and cardiac dysfunction. Activation of NRF2 also protected against myocardial infarction-induced DNA damage in remote myocardium and 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. Knockdown of NRF2 in NRVM increased stress-induced DNA damage, which was rescued by supplementing the cells with either nicotinamide adenine dinucleotide phosphate (NADPH) or nucleosides, the two main products of the PPP.

These results indicate that NRF2 regulates cardiac metabolic reprogramming by stimulating the diversion of glucose into the PPP, thereby generating NADPH and providing nucleotides to prevent stress-induced DNA damage and cardiac dysfunction.