檜木醇抑制3T3-L1脂肪細胞分化及增加胰島素在脂肪細胞的功效

肥胖人口逐年增加，已成為全球所關注的健康問題。萃取自扁柏的檜木醇為一種酚酮化合物，已知具有抗菌、抗腫瘤、抗氧化及抗發炎等生理功效。本研究使用小鼠3T3-L1前脂肪細胞為研究模式，探討檜木醇是否能抑制脂肪細胞生合成及增加胰島素對脂肪細胞葡萄糖攝入的功效。3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay結果顯示本實驗所使用的檜木醇濃度皆不會毒殺3T3-L1細胞。給予分化劑誘發3T3-L1前脂肪細胞分化為脂肪細胞的六天期間內，同時添加檜木醇(1、3或5 μM)處理，可顯著降低脂肪細胞中油滴生成及三酸甘油酯含量外，也減少脂肪細胞中調控三酸甘油酯生合成相關分子fatty acid synthase的蛋白質表現。於脂肪細胞分化期間給予檜木醇處理亦可降低成熟脂肪細胞特有分子標記的表現量，其中包含peroxisome proliferator-activated receptor γ (PPARγ)、CCAAT/enhancer binding protein α、glucose transporter type 4 (GLUT4)、adipocyte protein 2 (aP2)、adiponectin及resistin的表現。此外，研究結果顯示，檜木醇抑制脂肪細胞生合成可能與其抑制細胞分化前期ERKs的磷酸化及增加脂肪細胞β-catenin核蛋白表現量有關。值得注意的是，檜木醇除了不會降低成熟脂肪細胞PPARγ2、GLUT4、aP2及adiponectin mRNA的表現外，檜木醇亦可增加胰島素誘發的Akt substrate of 160 kDa蛋白質磷酸化、細胞膜上GLUT4的蛋白質表現及葡萄糖攝入量。綜合以上研究結果可知，檜木醇可抑制脂肪細胞脂質生合成和增加胰島素對脂肪細胞的功效。

Population of obesity increases every year and obesity has gradually become a global epidemic disease. Hinokitiol, a phytochemical isolated from Thuja plicata D. Don. and Chamaecyparis obtuse, Sieb. et Zucc., has anti-bacterial, anti-cancer, anti-oxidative and anti-inflammatory functions. The present study is to investigat effects of Hinokitiol on the adipogenesis and insulin action on adipocyte by using 3T3-L1 cell model. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed no significant toxicity of Hinokitiol at various concentrations treated with 3T3-L1 cells. During 6 days of 3T3-L1 preadipocytes differentiation preiod, Hinokitiol (1, 3 or 5 μM) treatment significantly reduced lipid droplets and triglyceride content in adipocytes as well as fatty acid synthase, a protein involved in triglyceride synthesis. Moreover, Hinokitiol treatment significantly decrease the expression of adipocyte specific markers such as peroxisome proliferator-activated receptor γ (PPARγ)、CCAAT/enhancer binding protein α、glucose transporter type 4 (GLUT4)、adipocyte protein 2 (aP2)、adiponectin and resistin. Our data showed that the decrease of ERKs phosphorylation in the early stage of adipogenesis and the increase of nuclear β-catenin levels in adipocyte by Hinokitiol may associted with the inhibitory effect of Hinokitiol on adiopogenesis. Notably, Hinokitiol did not alter the mRNA expression of PPARγ2、GLUT4、aP2 and adiponectin in differentiated 3T3-L1 adipocytes. Moreover, Hinokitiol treatment increase the Insulin-induced Akt substrate of 160 kDa phosphorylation and membrane GLUT4 protein expression as well as glucose uptake in differentiated 3T3-L1 adipocytes. In summary, Hinokitiol could inhibit adipogenesis and improve insulin action in 3T3-L1 adipocytes.