IL-25 stimulates M2 macrophage polarization and thereby promotes mitochondrial respiratory capacity and lipolysis in adipose tissues against obesity

This is the authors' abstract. We don't add key points for this paper.

Obesity and associated metabolic diseases are characterized by a chronic low-grade inflammatory state with the infiltration of many inflammatory cells, especially macrophages. Immune molecules, including some cytokines, have a close relationship with metabolism. Interleukin (IL)-25 is a member of the IL-17 cytokine family that can regulate macrophages and alleviate some metabolic dysfunction; however, its role and mechanisms in lipid metabolism remain to be extensively clarified. Human serum and liver biopsy specimens, high-fat diet-induced obesity mice and DB/DB (Lepr−/−) animal models were used to examine IL-25 expression in obesity and nonalcoholic fatty liver diseases (NAFLD). To observe the role of IL-25 in lipid metabolism, model mice were administered with IL-25 or adoptively transferred with IL-25-educated macrophages in vivo , whereas bone marrow-derived macrophages, the macrophage cell line RAW264.7 and adipocytes differentiated from 3T3-L1 were used in vitro . IL-25 was decreased in NAFLD patients and obese mice. In addition, IL-25 reduced body weight gain and lipid accumulation, enhanced lipid uptake by macrophages and increased the expression of lipolysis and β-oxidation enzymes via alternatively activating macrophages. IL-25 also promoted lipolysis and suppressed lipogenesis in adipocytes co-cultured with the IL-25-educated macrophages. Furthermore, IL-25 improved the mitochondrial respiratory capacity and oxygen consumption rate of macrophages and produced more NAD + /NADH and ATP. In conclusion, IL-25 can stimulate M2 macrophage polarization and thereby promote lipolysis and mitochondrial respiratory capacity, highlighting the potential for IL-25 to be used as a therapeutic agent against obesity and associated metabolic syndromes.