Effects of curcumin on retinoblastoma protein and p300 during adipocyte differentiation

The goal of the present study was to understand how curcumin suppresses PPARγ-mediated adipocyte differentiation in 3T3-F442 preadipocytes. We differentiated cultured 3T3-F442 cells with and without different doses of curcumin (0, 10µM, 15µM, and 20µM) and prepared cell lysates. We then performed Western Blot analysis to measure two upstream regulators of PPARγ, retinoblastoma protein (RB) and the p300 histone acetyltransferase in preadipocyte cells. Results were analyzed using one-Way ANOVA, and a Tuckey Post Hoc test. Curcumin caused a dose-dependent inhibition of adipocyte differentiation. Compared to control (no curcumin), dephosphorylated RB protein expression was higher in cultures exposed to 10 µM and 15 µM curcumin. However, at 20 µM the unphosphorylated RB protein decreased to the control level probably due to cell death. This suggests that curcumin inhibits 3T3-F442 preadipocyte differentiation by RB protein mediated inhibition of PPAR- γ. We did not detect the P300 protein in any cultures, including control by Western blot. This may be due to several reasons, including the cells not expressing P300, low sensitivity of detection technique, or denaturation of protein.