Insulin-induced Gene 2 Protects against Hepatic Ischemia-reperfusion Injury via Metabolic Remodeling

Abstract

Abstract Background:Hepatic ischemia-reperfusion (IR) injury is the primary reason for complications following hepatectomy and liver transplantation (LT). Insulin-induced gene 2 (Insig2) is one of several proteins that anchor the reticulum in the cytoplasm and is essential for metabolism and inflammatory responses. However, its function in IR injury remains ambiguous. Methods: Insig2 global knock-out (KO) mice and mice with adeno-associated-virus8 (AAV8)-delivered Insig2 hepatocyte-specific overexpression were subjected to a 70% hepatic IR model. Assessment of liver injury was performed by monitoring hepatic histology, inflammatory responses, and apoptosis. Hypoxia/reoxygenation stimulation (H/R) of primary hepatocytes was used for in vitro experiments. Multi-omics analysis of transcriptomics, proteomics, and metabolomics was used to investigate the molecular mechanisms underlying Insig2. Results: Insig2 expression was significantly reduced in both clinical samples undergoing LT and the mouse IR model. Our findings showed that Insig2 depletion significantly aggravated IR-induced hepatic inflammation, cell death and injury, whereas Insig2 overexpression caused the opposite phenotypes. The results of in vitro H/R experiments were consistent with those in vivo. Mechanistically, multi-omics analysis revealed that Insig2 is associated with an increase in antioxidant pentose phosphate pathway (PPP) activity. The inhibition of glucose-6-phosphate-dehydrogenase (G6PD), rate-limited enzyme of PPP, rescued the protective effect of Insig2 overexpression exacerbating the liver injury. Finally, our findings indicated that mouse IR injury could be attenuated through the development of a nanoparticle delivery system that enable liver-targeted delivery of substrate (glucose 6-phosphate) of PPP. Conclusions: Insig2 has a protective function in liver IR by upregulating the PPP activity. This may serve as a viable therapeutic target for alleviating hepatic IR.