Effect of retinoic acid on differentiation of cultured pig preadipocytes

We studied the effect of retinoic acid on the differentiation of cultured porcine preadipocytes. Porcine preadipocytes were cultured in serum-free medium (DME/F12 medium containing 100 nM insulin, 10 micrograms/mL transferrin, and 50 ng/mL hydrocortisone). Addition of increasing amounts of retinoic acid (1 nM to 20 microM) to the medium reduced glycerol-3-phosphate dehydrogenase (GPDH) activity, a late marker of preadipocyte differentiation. At lower concentrations (0.1 to 10 nM), retinoic acid had no effect on the GPDH activity. Addition of retinoic acid (10 microM) for 24 h during the early stage of development (d 1) greatly inhibited the GPDH activity. After the cells were differentiated, however, retinoic acid no longer had any effect. Therefore, retinoic acid was most effective in undifferentiated cells. Following a 24-h exposure of porcine preadipocytes to retinoic acid at d 1, Northern blot analysis showed that there was a decrease in lipoprotein lipase and adipsin mRNA levels. The results suggest that retinoic acid is a potent inhibitor of porcine preadipocyte differentiation in primary culture.