Metabolic reprogramming in Nrf2-driven proliferation of normal rat hepatocytes

Background aims: Cancer cells reprogram their metabolic pathways to support bioenergetic and biosynthetic needs and to maintain their redox balance. In several human tumors the Keap1-Nrf2 system controls proliferation and metabolic reprogramming by regulating the pentose phosphate pathway (PPP). However, whether this metabolic reprogramming also occurs in normal proliferating cells is unclear. Approach and results: To define the metabolic phenotype in normal proliferating hepatocytes, we induced cell proliferation in the liver by three distinct stimuli: liver regeneration by partial hepatectomy (PH) and hepatic hyperplasia induced by two direct mitogens, lead nitrate (LN) or triiodothyronine (T3). Following LN treatment, well-established features of cancer metabolic reprogramming including enhanced glycolysis, oxidative PPP, nucleic acid synthesis, NAD+/NADH synthesis and altered amino acid content as well as downregulated oxidative phosphorylation (OXPHOS) occurred in normal proliferating hepatocytes displaying Nrf2 activation. Genetic deletion of Nrf2 blunted LN-induced PPP activation and suppressed hepatocyte proliferation. Moreover, Nrf2 activation and following metabolic reprogramming did not occur when hepatocyte proliferation was induced by PH or T3. Conclusion: Many metabolic changes in cancer cells are shared by proliferating normal hepatocytes in response to a hostile environment. Nrf2 activation is essential for bridging metabolic changes with crucial components of cancer metabolic reprogramming including the activation of oxidative PPP. Our study demonstrates that matured hepatocytes exposed to LN undergo a cancer-like metabolic reprogramming and offers a rapid and useful in vivo model to study the molecular alterations underpinning the differences/similarities of metabolic changes in normal and neoplastic hepatocytes.