Figure 3. Leptin stimulates the phosphorylation of STAT3, ERK, and AKT.
HepG2 and Huh7 cells were cultured, serum-starved for 16 h, and treated with leptin (100 ng/mL) for various time intervals. Time 0 represents the absence of leptin or untreated cells. Cell lysates were prepared and quantified for protein content. A total of 100 µg protein was resolved on 10% SDS-PAGE followed by immunoblot analysis with specific antibodies against total or phosphorylated forms of STAT3 (A), ERK (B), and AKT (C). The representative histogram is the densitometric analysis of bands showing fold increase in levels of phosphorylated forms of STAT3, ERK, and AKT with respect to total STAT3, ERK, and AKT protein, at various intervals of leptin treatment. Representative of multiple independent experiments with a representative immunoblot for pSTAT3, STAT3, pERK, ERK, pAKT, and AKT. Columns, mean densitometric values of band intensities; bars, SE. *, P < 0.05, compared with untreated control cells. Immunoblot for β-actin was done as a loading control.