Hepatic-Metabolic Activity of α-Lipoic Acid-Its Influence on Sphingolipid Metabolism and PI3K/Akt/mTOR Pathway in a Rat Model of Metabolic Dysfunction-Associated Steatotic Liver Disease

Excessive lipid deposition affects hepatic homeostasis and contributes to the development of insulin resistance as a crucial factor for the deterioration of simple steatosis to steatohepatitis. So, it is essential to search for an effective agent for a new therapy for hepatic steatosis development before it progresses to the more advanced stages. Our study aimed to evaluate the potential protective effect of alpha-lipoic acid (alpha-LA) administration on the intrahepatic metabolism of sphingolipid and insulin signaling transduction in rats with metabolic dysfunction-associated steatotic liver disease (MASLD). The experiment was conducted on male Wistar rats subjected to a standard diet or a high-fat diet (HFD) and an intragastrically alpha-LA administration for eight weeks. High-performance liquid chromatography (HPLC) was used to determine sphingolipid content. Immunoblotting was used to measure the expression of selected proteins from sphingolipid and insulin signaling pathways. Multiplex assay kit was used to assess the level of the phosphorylated form of proteins from PI3K/Akt/mTOR transduction. The results revealed that alpha-LA decreased sphinganine, dihydroceramide, and sphingosine levels and increased ceramide level. We also observed an increased the concentration of phosphorylated forms of sphingosine and sphinganine. Changes in the expression of proteins from sphingolipid metabolism were consistent with changes in sphingolipid pools. Treatment with alpha-LA activated the PI3K/Akt/mTOR pathway, which enhanced the hepatic phosphorylation of Akt and mTOR. Based on these data, we concluded that alpha-lipoic acid may alleviate glucose intolerance and may have a protective influence on the sphingolipid metabolism under HFD; thus, this antioxidant appears to protect from MASLD development and steatosis deterioration.