Docosahexaenoic acid-enriched phospholipids and eicosapentaenoic acid-enriched phospholipids inhibit tumor necrosis factor-alpha-induced lipolysis in 3T3-L1 adipocytes by activating sirtuin 1 pathways

Some chronic diseases such as cancer-associated cachexia (CAC) and obesity are associated with the overproduction of tumor necrosis factor-alpha (TNF-α) that stimulates excess lipolysis in adipocytes. Our previous studies have shown that docosahexaenoic acid-enriched phospholipids (DHA-PL) and eicosapentaenoic acid-enriched phospholipids (EPA-PL) ameliorated CAC and obesity-related metabolic disorders. To identify the molecular mechanisms involved, we examined the impact and the associated signaling pathways of DHA-PL and EPA-PL on TNF-α-induced lipolysis in 3T3-L1 adipocytes. The present results revealed that DHA-PL and EPA-PL inhibited the TNF-α-induced increase of glycerol release and protected lipid droplets. In addition, DHA-PL and EPA-PL increased DHA and EPA contents in the phospholipid fraction of adipocytes, respectively. Moreover, DHA-PL and EPA-PL enhanced sirtuin 1 (SIRT1) deacetylase activity and its protein expression. By activating SIRT1, DHA-PL and EPA-PL upregulated the G0/G1 switch gene 2 protein level to inhibit adipose triglyceride lipase activity, activate AMP-activated protein kinase to reverse the downregulation of perilipin expression and phosphorylation of hormone-sensitive lipase (HSL) at Ser565 and prevent the phosphorylation of HSL at Ser660. Furthermore, DHA-PL and EPA-PL improved glucose uptake and glucose transporter type 4 translocation to the plasma membrane in TNF-α-treated adipocytes. Thus, it was concluded that DHA-PL and EPA-PL inhibit TNF-α-induced lipolysis in 3T3-L1 adipocytes by activating the SIRT1 pathways.