Inhibition of Insulin-Like Growth Factor-1–Induced Sebum Production by Bilobetin in Cultured Human Sebocytes

BACKGROUND: Sebocytes are the major cells of sebaceous gland. The essential role of sebocytes is the production of sebum, a specific lipid mixture, that covers the body surface and provides the barrier function. At puberty, sebum production increases under the effects of various stimuli including androgens and insulin-like growth factor-1 (IGF-1). Excessive sebum production changes the microenvironment surrounding hair follicle, often leading to the onset of acne. OBJECTIVE: We previously performed screening test using cultured human sebocytes, and found that bilobetin had a potential for inhibiting lipid production. The aim of this study is to demonstrate the effects of bilobetin on IGF-1–induced lipogenesis in sebocytes. METHODS: We pretreated simian virus 40 T (SV40T)-transformed sebocytes with bilobetin then stimulated with IGF-1. Effects of bilobetin on lipogenesis of sebocytes were examined by thin layer chromatography and Western blot. RESULTS: Bilobetin markedly inhibited IGF-1–induced lipid production in sebocytes, especially in terms of production of squalene and wax ester. Supporting these results, bilobetin showed significant inhibitory effect on squalene synthase promoter activity. In addition, bilobetin significantly down-regulated lipogenic transcription factors such as sterol response element binding protein (SREBP)-1 and SREBP-2. To delineate the possible action mechanism, we investigated the effect of bilobetin on intracellular signaling. As a result, bilobetin inhibited IGF-1–induced phosphorylation of AKT. CONCLUSION: Together, these results suggest that bilobetin has an inhibitory potential on sebum production in sebocytes, being applicable for acne treatment.