Rewired NAD+ metabolism promotes NF-κB-mediated oxidative stress and disrupts lipid homeostasis in liver fibrosis progression
Chronic liver fibrosis significantly increases the risk of hepatocellular carcinoma (HCC), a leading cause of cancer-related deaths. However, the molecular mechanisms linking fibrosis to inflammation-associated HCC development remain unclear, complicating early diagnosis and intervention. In this study, we employ multi-omics analyses, including untargeted and targeted metabolomics, lipidomics, and transcriptomics, in a mouse model of chemically induced liver fibrosis and HCC, integrating publicly available transcriptome data from LX-2 human hepatic stellate cell (HSC) line. Our results reveal a profound rewiring of NAD+ metabolism as a central driver of metabolic disturbance. Analysis of bulk liver tissue shows increased activity of the kynurenine pathway of tryptophan metabolism, enhancing NAD+ precursor production. Hepatic nicotinamide (NAM) levels decrease due to elevated expression of NAM N-methyltransferase (Nnmt) in HSCs. Despite reduced hepatic NAM, serum NAD+ level rise and is compartmentalized, triggering a disruption in NAD+ homeostasis and activating NF-{kappa}B-mediated oxidative stress pathways. Moreover, lipid dysregulation occurs, with NF-{kappa}B dominating the regulation of SIRT1/SREBP-controlled lipogenic and cholesterogenic genes, leading to imbalances in hepatic and serum lipids. These insights elucidate connections between NAD+ metabolism, inflammation, and lipid dysregulation, potentially aiding in developing diagnostic biomarkers and therapeutic targets for non-viral HCC. Key PointsO_LIThe integration of untargeted and targeted metabolomics identifies the metabolic pathways that are associated with the development of hepatocellular carcinoma (HCC) and the potential role of disturbances in NAD+ metabolism as a central driver of metabolic dysregulation in hepatic fibrosis, validated across transcriptomics. C_LIO_LIFibrosis-associated HCC is linked to the depletion of nicotinamide and a cascade of metabolic disturbances that promote inflammation and oxidative stress in hepatic stellate cells. C_LIO_LITargeted analysis of the metabolites in the discriminative pathways along a continuum of fibrosis-cirrhosis-HCC discovers several potential tissue and serum biomarkers for monitoring disease progression. C_LIO_LIMulti-omics analysis (i.e., metabolomics, lipidomics, and transcriptomics) reveals complex interplay between NAD+ metabolism, NF-{kappa}B-mediated oxidative stress, and lipid homeostasis in fibrosis-associated HCC development. C_LI O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=183 SRC="FIGDIR/small/668888v2_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@e39d72org.highwire.dtl.DTLVardef@175cdc7org.highwire.dtl.DTLVardef@118d707org.highwire.dtl.DTLVardef@1cd3a43_HPS_FORMAT_FIGEXP M_FIG C_FIG