Abstract: Objective To explore the effects of niacinamide(NAM)on proliferation and differentiation of murine 3T3-L1 preadipocytes. Methods 3T3-L1 preadipocytes were cultured and treated with NAM and resveratrol(Res)in different dosages.Cell proliferation was analyzed with water soluble tetrazole(WST)-1 method.Oil red O staining method and spectrophotography were applied to analyze the degree of differentiation.Western blot was applied to detect the expression of silent information regulator 1(Sirt1),peroxisome proliferator activated receptorγ(PPARγ),and CCTTA enhancer binding proteinα (C/EBPα). Results After treated with NAM for 48 hours,compared with the control with or without Res treatment,the relative cell amount increased by 1.152 and 1.272 times and the relative fat content was 1.519 and 1.321 times;the protein levels of Sirt1,PPARγ,42KDa and 24KDa C/EBPαof NAM-treated and NAM+Res-treated groups were 0.381,2.107, 1.005,and 1.233 times and 0.421,2.226,2.031,and 1.544 times compared to those of control group. Conclusion NAM can enhance the proliferation and differentiation of 3T3-L1 preadipocytes,and the underlying mechanisms may include inhibiting expression of Sirt1 and increasing expression of PPARγand C/EBPα.