Ann Dermatol.  2019 Jun;31(3):294-299. 10.5021/ad.2019.31.3.294.

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

• Wang C
• Hwang YL
• Li XM
• Kim SJ
• Zhu MJ
• Lee JH
• Jiang RH
• Kim CD

• KMID: 2444861
• DOI: http://doi.org/10.5021/ad.2019.31.3.294

Abstract

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.

Keyword

Acne; Bilobetin; Insulin-like growth factor I; Sebocytes

MeSH Terms

Acne Vulgaris
Adolescent
Androgens
Blotting, Western
Carrier Proteins
Chromatography, Thin Layer
Farnesyl-Diphosphate Farnesyltransferase
Hair Follicle
Humans*
Insulin-Like Growth Factor I
Lipogenesis
Mass Screening
Phosphorylation
Puberty
Response Elements
Sebaceous Glands
Sebum*
Simian virus 40
Squalene
Transcription Factors
Androgens
Carrier Proteins
Farnesyl-Diphosphate Farnesyltransferase
Insulin-Like Growth Factor I
Squalene
Transcription Factors

Figure

• 

  Fig. 1 (A) Structure of bilobetin. (B) Cytotoxicity of bilobetin. Simian virus 40 T (SV40T)-transformed sebocytes were treated with bilobetin at the indicated concentrations for 1 day. Cell viability was measured by MTT assay. The mean values±standard deviation are averages of triplicate measurements.

• 

  Fig. 2 (A) Effect of bilobetin on the growth of sebocytes. Simian virus 40 T (SV40T)-transformed sebocytes were incubated in plain media without fetal bovine serum, then treated with insulin-like growth factor-1 (IGF-1) and bilobetin for 2 days in the presence of 1 µCi [3H]thymidine. After scintillation counting, data are expressed as percent control. The mean values±standard deviation (SD) are averages of triplicate measurements. Bilobetin inhibited IGF-1–induced cell growth. (B) Cells were treated with IGF-1 and bilobetin at the indicated concentrations for 1 day. Neutral lipids were detected by Oil Red O staining (×400). (C) Effect of bilobetin on IGF-1–induced lipid production was determined by thin layer chromatography. Production of squalene and wax ester was significantly inhibited by bilobetin. (D) Effect of bilobetin on the squalene synthase promoter activity. Cells were transduced with 1 multiplicity of infection of squalene synthase-luc reporter adenovirus, then treated with IGF-1 and bilobetin for 1 day. Cells were lysed and assayed for luciferase activity. Data are represented as fold induction±standard deviation, measured from three independent experiments. *p<0.01.

• 

  Fig. 3 (A) Effect of bilobetin on the protein level for lipogenic regulators. Simian virus 40 T (SV40T)-transformed sebocytes were treated with insulin-like growth factor-1 (IGF-1) and bilobetin at the indicated concentrations for 1 day. Protein level for lipogenic regulators was evaluated by Western blot. (B) Effect of bilobetin on intracellular signaling. Cells were pretreated with bilobetin at the indicated concentrations for 30 minutes, and then IGF-1 was treated for 30 minutes. Cellular proteins were prepared and phosphorylation of signaling molecules was evaluated by Western blot. Actin was used as a loading control. Western bands were densitometrically analyzed and normalized with actin. SREBP: sterol response element binding protein, FDFT1: farnesyl-diphosphate farnesyltransferase 1, SCD: stearoyl-CoA desaturase.

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