Conjugated linoleic acid regulation of fatty acid metabolism by mTOR signaling pathway in grass carp (Ctenopharyngodon idella) adipocytes

The purpose of this study was to investigate the effects of conjugated linoleic acid (CLA) on fatty acid metabolism through the mammalian target of rapamycin (mTOR) signaling pathway in grass carp (Ctenopharyngodon idella) adipocytes. Grass carp preadipocytes were cultured and treated with various concentrations of CLA (0, 50, 100, 150 and 200 μmol/L). Lipid accumulation was assessed using Oil Red O staining. The regulatory effects on mTOR signaling pathway were evaluated using real-time quantitative PCR (RT-qPCR) and Western Blot (WB). CLA treatment significantly inhibited lipid accumulation and downregulated the expression of genes related to de novo fatty acid synthesis, including fatty acid synthase (fas), acetyl-CoA carboxylase (acc), stearoyl-CoA desaturase 1 (scd1), and sterol regulatory element binding protein-1c (srebp-1c). In contrast, the expression of genes related to fatty acid transport and β-oxidation, such as carnitine palmitoyl transferase-1α (cpt-1α) and hormone-sensitive lipase (hsl), was upregulated. These regulatory effects were found to be concentration-dependent. Co-treatment with the mTOR inhibitor rapamycin further suppressed the mRNA expression of srebp-1c, fas and acc. Furthermore, CLA reduced the protein expression levels of mTOR and nuclear sterol regulatory element-binding protein 1 (nSrebp1), while exerting minimal effect on phosphorylated mTOR (p-mTOR). In summary, CLA appears to modulate lipid metabolism in grass carp adipocytes by inhibiting srebp-1c within the mTOR signaling pathway.