Objective To explore the improvement effects of C2C12 myotube cells pre-treated with eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on lipid metabolism of 3T3-L1 adipocytes. Methods Myotube cells were pre-treated with 50, 100, 200, 400 μmol/L EPA or DHA for 24 hours, and a control group was set up at the same time. Myotube cells were co-cultured with mature adipocytes in the transwell chamber for 24 hours after the treatment. Oil red O staining was used to quantify lipid accumulation in the adipocytes, and PCR was used to determine the expressions of lipid metabolism genes adipose triglyceride lipase (Atgl), hormone-sensitive lipase (Hsl), PPARG coactivator 1 alpha (Pgc-1α), Uncoupling protein-1 (Ucp-1) and Sterol regulatory element binding protein-1c (Srebp-1c). Western blot was used to detect the protein expression of adenosine 5‘-monophosphate (AMP)-activated protein kinase (AMPK) and signal transduction and activator of transcription 3 (STAT3) signaling pathways. Results Myotube cells pre-treated with 100, 200, and 400 μmol/L EPA significantly reduced lipid accumulation in the adipocytes (P<0.05 or P<0.001), while myotube cells pre-treated with DHA showed no improvement of lipid accumulation. EPA or DHA at certain concentrations can significantly upregulated the expressions of adipocyte lipolysis genes Atgl and Hsl and lipid oxidation genes Ucp-1 and Pgc-1α (P<0.05 or P<0.01). Myotube cells pre-treated with certain concentrations of EPA significantly increased the expression of the lipid synthesis gene Srebp-1c (P<0.05 or P<0.01), while myotube cells pre-treated with certain concentrations of DHA significantly reduced the expression of the lipid synthesis gene Srebp-1c(P<0.01 or P<0.001). Myotube cells pre-treated with EPA significantly increased the p-STAT3/STAT3 ratio, but had no significant effect on the p-AMPK/AMPK ratio. Myotube cells pre-treated with 200 and 400 μmol/L DHA significantly increased the p-AMPK/AMPK ratio, but had no significant effect on the p-STAT3/STAT3 ratio. Conclusion At appropriate concentrations, both EPA and DHA can activate myotube cells to improve lipid decomposition and lipid oxidation of the adipocytes. Myotube cells pre-treated with EPA can increase lipid synthesis to a certain extent through the STAT3 pathway, and those pre-treated with DHA can reduce lipid synthesis to a certain extent through the AMPK pathway.
Key words
eicosapentaenoic acid (EPA) /
docosahexaenoic acid (DHA) /
C2C12 myotubes /
3T3-L1 adipocytes /
lipid metabolism /
STAT3/AMPK signaling pathway /
co-culture
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