Figure 4. IGF-1 induces lipogenesis in SEB-1 sebocytes through activation of the PI3-K pathway.

The ¹⁴C incorporation assay was performed on SEB-1 cells treated with IGF-1 (20 ng/ml) and/or 50 µM of a pharmacological inhibitor of PI3-K (LY294002) or MAPK/ERK (PD98059). IGF-1 induces a robust increase in lipogenesis (black striped bars vs. solid black bars). Interestingly, addition of 50 µM PD98059 to cells treated with IGF-1 has no effect on the IGF-1 induced lipogenesis (striped red bars vs. solid red bars). Most importantly, the addition of 50 µM PI3-K inhibitor LY294002 blocks any induction of lipogenesis when cells are stimulated with IGF-1 (blue striped bars vs. blue solid bars). All samples within an experiment were done in triplicate, and each experiment was performed at least three separate times. Data were analyzed by ANOVA and considered significant if a p-value of <0.05 was observed compared to the DMSO vehicle treated control group. Abbreviations used in this figure are: C=cholesterol; CO=cholesterol oleate; FOH=fatty alcohols; OA=oleic acid; SQ=squalene; TAG=triglycerides; WE=wax esters.