Obesity is known to be induced by the accumulation of hypertrophy and hyperplasia of newly created fat in adipose tissues through differentiation of adipocyte precursor cells. Some cytokines are excessively produced in adipose tissues that can negatively regulate differentiation of adipocytes. Impaired adipogenesis is known to contribute to obesity-related diseases. Interleukin-10 (IL-10) is involved in the development of type 2 diabetes, insulin sensitivity, and immune response in obesity state. However, effects of IL-10 on adipogenesis remain unclear. The objective of this study was to determine the inhibitory effect of IL-10 on adipocyte differentiation and mechanisms involved in such effect. The effect of IL-10 on adipogenesis was analyzed by Western blot analysis, Oil Red O staining, qRT-PCR, and flow cytometry. We also examined the part of Wnt5a in adipogenesis using gene interfering technique. IL-10 suppressed lipid accumulation and adipocyte differentiation related gene expression. The inhibitory effect of IL-10 on the differentiation of adipocytes occurred at an early phase. IL-10 treatment caused a G0/G1 phase cell cycle arrest and altered expression levels of cell cycle proteins (CDK2, p21, and p27), thereby preventing re-entry into cell cycle. Additionally, IL-10 treatment reduced Wnt5a expression. Inhibition of Wnt5a by siRNA significantly attenuated lipid accumulation and expression of adipocyte differentiation-related genes. Taken together, these results indicate that IL-10 can inhibit the early phase of adipogenesis via suppressing Wnt5a signaling pathway in 3T3-L1 preadipocytes. (C) 2019 Elsevier Inc. All rights reserved.