Recent studies have shown that the health benefits of probiotics are not limited to those offered by living bacteria. It was reported that both live and killed cells of Propionibacterium freudenreichii MJ2 (MJ2) isolated from raw milk showed antiobesity activity in 3T3-L1 cells and high-fat diet-induced obese mice. This study was aimed at identifying the active component(s) responsible for the antiadipogenic activity of MJ2. Cell wall, surface protein, and cytoplasmic fractions of MJ2 were investigated for their inhibitory effects on adipogenesis in 3T3-L1 cells. Adipocytes treated with the surface protein fraction showed significantly lower lipid accumulation. Using the MASCOT algorithm following LC-MS/MS analysis, 131 surface proteins were identified and they were principally classified into three categories (network clusters related to ribosomes, carbon metabolism, and chaperones). Among them, chaperonin 60 (Cpn60) was selected as a potential candidate protein. Cpn60 inhibited lipid accumulation and adipogenesis during the early period of differentiation (days 0-2) and decreased expression of genes related to adipogenesis (Pparg and Cebpa) and lipogenesis (Fas and Scd1). The expression of Gata2/3, which suppresses adipogenesis, significantly increased in Cpn60-treated cells. Moreover, the nuclear translocation of C/EBPβ was inhibited by Cpn60 treatment. In conclusion, Cpn60, a surface protein in MJ2, shows antiadipogenic activity by reducing the expression of C/EBPβ through the upregulation of Gata2/3 expression followed by downregulation of Pparg and Cebpa expression.
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