IL-35 inhibits adipogenesis via PPARγ-Wnt/β-catenin signaling pathway by targeting Axin2

Interleukin (IL)-35, a member of the IL-12 family, functions as an immunosuppressive cytokine that plays a crucial role in the regulation of immune-related disorders and inflammatory diseases. Adipose tissue, which is now recognized as an immune organ, is regulated by immunocytes through various signaling pathways, including the peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα) pathway and the Wnt/β-actin pathway. However, there is limited research regarding the effects of IL-35 on adipogenesis. Our current findings indicated that IL-35 impedes the proliferation and promotes the cytotoxicity of 3T3-L1 preadipocytes. Furthermore, IL-35 inhibited the adipogenic differentiation, as well as suppressed triglyceride and lipid accumulation. Additionally, the expression of PPARγ and C/EBPα, two key regulators of adipogenesis, were both down-regulated with IL-35 treatment. In order to explicate the mechanisms underlying the effects of IL-35, we conducted an investigation into the expression of Axin2, an intracellular inhibitor of Wnt/β-catenin signaling, in 3T3-L1 preadipocyte cells. Gene silencing of Axin2 through small interfering RNAs (siRNAs) enhanced PPARγ and C/EBPα expression while decreasing nuclear β-catenin levels in the presence of IL-35. Furthermore, in IL-35-treated cells, Axin2 knockdown boosted adipogenic differentiation (as measured by increased Oil Red O staining). These findings imply that IL-35 regulates Axin2 expression and thereby plays an important role in adipocyte development.