Suppression of adipogenic differentiation by muscle cell-induced decrease in genes related to lipogenesis in muscle...

Intercellular signalling communication between adipose and muscle tissue has been investigated. To test the effect of muscle cells on adipogenic gene expression, we utilised an in vitro co-culture system, in which fat (3T3-L1) and muscle (L-6) cells were physically separated but chemically exposed each other via insert with 0.4 µm porous membrane. When 3T3-L1 and L-6 cells reached at 80 and 40% confluence, respectively in separate wells, L-6 cells grown in insert were transferred onto 6-well plates where 3T3-L1 cells were being grown. When both cells were fully differentiated in co-culture plates, morphology of 3T3-L1 was examined by staining with Oil-red-O. Activity of glycerol-3-phosphate dehydrogenase (GPDH) and adipogenic gene expression including lipoprotein lipase (LPL), adipsin, GPDH, peroxisome proliferator-activated receptor-γ (PPARγ) and CCAAT/enhancer binding protein (C/EBPα) were analysed. The presence of muscle cells during preadipocyte differentiation inhibited (P < 0.05) lipogenesis by suppressing lipogenic gene expression including LPL, adipsin and GPDH. Furthermore, GPDH activity was also decreased (P < 0.05) in 3T3-L1 cells by the presence of L-6 cells. These results suggest that presence of muscle cells suppresses adipogenic differentiation by inhibiting the adipogenic gene expression and GPDH activity in the muscle and fat cell co-culture system.