Objective Cathepsin family is lysosomal cysteine protease. It is recently reported that cathepsin K, L, S control adipogenesis and relate to acute coronary syndrome. However, it is not clear whether cathepsins expression can be affected by saturated fatty acid which has a critical role in metabolic disease. We examined the hypothesis that palmitate upregulates cathepsin K, L, S expression in obese adipose tissue and infiltrating macrophages have crucial role in this process via inflammatory cytokines. Methods 3T3-L1 cells were fully differentiated to mature adipocytes for 8 to 10 days and treated with palmitate, lipopolysaccharide (LPS) which is ligand of TLR4 (toll-like receptor 4). Six-week-old C3H/HeN mice with normal TLR4 and C3H/HeJ mice with TLR4 gene's mutation got LPS injection ip (1 mg/kg) or were fed with high fat diet (60% fat of total calories) for 13 weeks and sacrifice to harvest epididymal fat. Results Real-time PCR revealed that not cathepsin S but cathepsin K, L expression is upregulated by palmitate as dose- and time-dependent manner. But there was no additional effect when we use palmitate-treated RAW264.7 cells' media instead of direct treatment to 3T3-L1 cells. Cathepsin K, L is upregulated after treatment of TNF-α or IL-6 like palmitate. Cathepsin K, L, S expression increased in both kinds of mice fed high fat diet compared with chow diet. But we cannot find similar pattern at mice which got LPS ip injection. Conclusion We concluded that cathepsin K, L expression in fat tissue are upregulated by saturated fatty acid via inflammatory cytokines, not TLR4, thereby might have a critical role in developing acute coronary syndrome of metabolic syndrome and there are no additional effects of infiltrating macrophages.