Shikonin에 의한 지방세포형성 억제과정에서의 유전자 발현 연구

Abstract

Shikonin, a component of Lithospermum erythrorhizon Sieb. et Zucc, exerts various characteristics such as anti-inflammatory, anti-cancer and anti-obesity functions. To elucidate the molecular mechanism of shikonin-induced inhibition of adipogenesis, we analyzed the mRNA expression level of various adipogenesis-related factors including C/EBPs (CCAAT/enhancerbinding proteins) and PPARγ (peroxisome proliferator-activated receptor γ). The data showed that mRNA expressions of C/EBPβ and C/EPBδwere only slightly changed by shikonin treatment, but mRNA expressions of PPARγ and C/EPBα were significantly down-regulated. Then, we tested whether upstream regulators of C/EBPβ and PPARγ were involved in anti-adipogenesis of shikonin. C/EBPγ and CHOP (C/EBP homologous protein), which are upstream regulators of C/EBPβ, were not affected by shikonin treatment. On the contrary, the mRNA level of KROX20 was markedly down-regulated by shikonin treatment. These results suggest that KROX20 might regulate downstream factors of adipogenesis through C/EBPβ-independent pathway. The expression of KLF15 (Kruppel-like factor15), which is a member of KLF family and is a upstream regulator of PPARγ, was dramatically decreased by shikonin treatment, but KLF2 was not changed. Shikonin had no impact on the expression of KLF5 in the early stage of adipogenesis, but shikonin increased expression of KLF5 in the late stage of adipogenesis. Even though mRNA expression of KLF5 was moderately changed by shikonin treatment, its effect may be small compared with the effect of KLF15, which was markedly inhibited. Taken together, these results suggest that shikonin inhibits adipogenesis through the down-regulation of PPARγ and C/EPBα, which is mediated by the down-regulation of two pro-adipogenic factors, KROX20 and KLF15.