Non-alcoholic fatty liver disease (NAFLD) is a significant global public health issue characterized by hepatic lipid accumulation. Nicotinamide adenine dinucleotide (NAD+) is a crucial cofactor in cellular metabolism across mammalian organs. Nicotinamide mononucleotide (NMN), an important intermediate in NAD+ salvage synthesis, may influence high-fat diet (HFD)-induced hepatic steatosis. An HFD-induced NAFLD mouse model was established in C57BL/6 mice, followed by NMN administration for 8 weeks. HepG2 cells were treated with palmitic acid and co-incubated with NMN to establish an in vitro lipid accumulation model. Network pharmacology analysis and transcriptomic profiling were performed to identify potential molecular targets and pathways involved in the protective effects of NMN against NAFLD. Lipid accumulation was evaluated by H&E staining and Oil Red O staining. Serum lipid metabolism parameters were measured using assay kits. Quantitative RT-PCR and Western blotting were used to examine the expression of pathway-related genes and proteins to investigate the potential mechanism by which NMN alleviates hepatic steatosis. Compared with the HFD model group, NMN intervention significantly reduced body weight and alleviated hepatic steatosis. It also lowered levels of low-density lipoprotein (LDL), triglycerides, total cholesterol, and fasting blood glucose, while increasing high-density lipoprotein (HDL) levels. Liver PPAR-γ levels decreased, while HNF4α and SHBG levels increased. These findings suggest that the protective effects of NMN on HFD-induced hepatic steatosis are associated with decreased hepatic PPAR-γ expression and increased HNF4α and SHBG expression. NMN showed protective effects against HFD-induced NAFLD, which were associated with improvements in hepatic lipid metabolism. By integrating network pharmacology, transcriptomic analysis, and experimental validation, this study provides initial evidence regarding molecular changes associated with the effects of NMN in NAFLD.
