Sphingolipid and glucose metabolism play important roles in the induction and progression of severe liver disorders like metabolic dysfunction-associated steatotic liver disease (MASLD). The perturbation in sphingolipid formation may improve the liver structure and functioning and may constitute the potential therapeutic options for the development of simple steatosis and its progression to steatohepatitis. This study aims to assess the influence of N-acetylcysteine (NAC) on the sphingolipid and insulin signaling pathways in rats subjected to standard or high-fat diets. Sphingolipid level was measured using high-performance liquid chromatography (HPLC). A multiplex assay kit determined the level of phosphorylated form of proteins included in the PI3K/Akt/mTOR pathway. The immunoblotting estimated the expression of proteins from sphingolipid and insulin transduction pathways. A histological Oil red O staining was used to assess the hepatic accumulation of lipid droplets. Molecular docking was applied to showcase NAC interaction with PI3K/Akt/mTOR pathway proteins. NAC decreased dihydroceramide and ceramide levels and increased phosphorylation of sphingosine and sphinganine. This antioxidant also enhanced phosphorylated Akt, GSK3α/β, and P70 S6 kinase and decreased phosphorylated S6RP. In silico docking analysis of insulin signaling molecules evidenced the higher binding affinity of NAC with all tested proteins, i.e., IRS1, PTEN, Akt, GSK3α/β, P70 S6 kinase, and S6RP, suggesting a potential protective influence on insulin resistance development, which is one of the criteria for MASLD diagnosing. Based on these data, NAC improved the hepatic insulin sensitivity and sphingolipid synthesis and storage, improving and restoring glucose homeostasis.
Keywords: Insulin resistance; Liver; Obesity; Sphingolipid; Steatosis.
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