Effects of the ERK inhibitor and activator on the inhibition of adipocyte differentiation by shikonin. (A) The protein level and mRNA expression were determined with ERK 1/2. Cells were treated with (A) Shikonin (1 μM) and the ERK inhibitor PD98059 (10 μM) during adipocyte differentiation. After 8 days, the cells were stained with Oil Red O to determine the degree of lipid accumulation. The inhibitory effects of shikonin and PD98059 on ERK 1/2 signaling pathway were observed during adipocyte differentiation. (B) Western blot analysis performed with the ERK pathway and adipogenic marker genes.