Abstract

An understanding of the molecular signaling involved in sebaceous gland lipid production is needed to develop therapeutic targets to improve acne. Treatment with methylisobutylxanthine, dexamethasone, and a high dose of insulin (MDI) has been shown to differentiate 3T3-L1 preadipocytes into adipocytes, a differentiation marked by an increase in lipid production. The present study has the following aims: (1) Since high doses of insulin, as found in MDI, will activate the IGF-1 receptor, we sought to determine if IGF-1 is capable of reproducing the lipogenic effect seen with MDI treatment, and (2) to determine if the sterol response element-binding protein-1 (SREBP-1) pathway mediates the increase in lipogenesis. Here we report that MDI increases lipogenesis and that this effect can be attributed wholly to the high-dose insulin in SEB-1 cells. Further, we show that a physiologically relevant dose of IGF-1 or high-dose (1 microM) insulin induces an increase in SREBP-1 mRNA, protein, and total lipid production; while 100 nM insulin induces lipogenesis yet the SREBP protein levels remain unchanged. These data indicate that activation of the IGF-1 receptor increases lipogenesis in SEB-1 cells through both SREBP-dependent and SREBP-independent pathways.