| 摘要: | 現代人因為飲食的關係很容易形成肥胖，肥胖現在已漸漸成為全球共同的問題，由於脂肪堆積過多，因而對人體健康產生負面影響,且容易引發各種疾病發生，如糖尿病，癌症，心臟疾病和高血壓等。在過去幾十年中，已經有廣泛的研究針對治療肥胖和預防肥胖發展新的潛在藥物。半乳糖凝集素12已經被發現是一種會在脂肪細胞表達的蛋白質，並具有誘導脂肪細胞凋亡活性，而且楊日曜博士等人已經發表在脂肪細胞分化過程中，若剔除半乳糖凝集素12，脂肪細胞內半乳糖凝集素12不會表現，脂肪細胞內的脂肪分解作用就會上升，加速三酸甘油脂代謝，同時他們探討半乳糖凝集素12在脂肪分化過程中，發現半乳糖凝集素12會抑制脂肪生成轉錄因子的表達。
根據半乳糖凝集素12在脂肪細胞分化後的48小時會大量表現的特性，我們設計了一個高通量篩選平台，因此利用Luciferase assay篩選105種中藥對半乳糖凝集素12啟動子活性表現量的調控作用，發現其中有14種中藥對半乳糖凝集素12啟動子的活性具有良好的抑制效果，並且進一步利用定量PCR分析偵測14種中藥對半乳糖凝集素12基因的表現量，從中發現玉米鬚無論是對半乳糖凝集素12啟動子的活性還是半乳糖凝集素12基因的表現量，都具有顯著的抑制效果，同時我們利用細胞存活率分析發現玉米鬚對3T3-L1細胞並不具有毒性，因此我們更進一步的探討玉米鬚對於油滴生成的影響，所以我們利用了Oil red o和adipored染色，發現隨著玉米鬚處理的濃度越高，3T3-L1細胞內油滴生成量越少。我們也發現玉米鬚能夠抑制脂肪細胞分化過程中的轉錄因子PPAR和C / EBP家族（C /EBPβ，C /EBPα）的基因和蛋白表現。之後我們在小鼠模型中，觀察到餵食玉米鬚的老鼠體重跟單獨餵食高脂飼料的老鼠相比，體重明顯下降，而且在肝臟組織切片中的油滴以及脂肪組織切片中的脂肪細胞大小和數量也有顯著減少。在血清中三酸甘油脂的含量也明顯降低了，根據以上獲得的結果，我們認為玉米鬚可以透過抑制半乳糖凝集素12啟動子活性，有效地減少前脂肪細胞分化和減少脂肪細胞的形成。
Obesity has become a global epidemic in both developed and developing countries, and it is a significant risk factor for various diseases such as diabetes, cancer, heart disease, and hypertension. Obesity is a clinical condition caused by excessive accumulation of fat, which exerts negative impact on human’s health. Over few decades, extensive research has been directed towards discovery of new potential drugs in-order to treat obesity and to prevent obesity. There are two types of adipocytes, called as brown adipocyte and white adipocyte. Obesity is more related to white adipocyte as these cells store more lipid droplets. Galactin-12 has been recently shown to be an adipocyte-expressed protein and possesses adipocyte-inducing activity. Following this finding, we set out to investigate the expression level of candidate proteins involved in galactin-12 adipocyte differentiation pathway. We performed a high-throughput screening assay for galectin-12 promoter activities for 105 traditional Chinese herbs. Our previous reporter assay screening found that corn silk extract reduced the expression of galactin-12 promoter in 3T3-L1 cell lines. In our present study, we test the efficiency of corn silk extract to inhibit adipogenesis and cytotoxicity in 3T3-L1 pre-adipocytes, as potential therapeutic drug for treatment of obesity. Treatment of corn silk extract (800 μg/ml, 600 μg/ml, 400 μg/ml, 200 μg/ml, 100 μg/ml) to 3T3-L1 pre-adipocyte showed inhibition of differentiation of pre-adipocyte to adipocyte cells, by oil red-o-stain and adipored stain for quantification of lipid droplets. We also set out our analysis to find the cytotoxicity of corn silk using MTT assay and found that corn silk extract have no toxic effect on 3T3-L1 cells. It had been reported that galectin-12 can reduce the expression of the adipogenic transcription factors. So, we dissected the molecular pathway involved in the observed weight loss. Adipocyte differentiation process is mainly regulated by PPAR and C/EBP family (C/EBPβ, C/EBPα) of transcription factors, thus converting the pre-adipocyte cells into mature fat cells. The results of our data from qPCR and immunoblotting revealed a down-regulation PPARγ and C/EBP transcription factors there-by inhibiting the differentiation of pre-adipocytes to mature fat cells. Our in vivo analysis on the mouse model showed a significant decrease in the adipocyte cells in several organs such as liver, adipose tissue etc. and resulted in weight loss. Also, we test the active compound of corn silk, β-sitosterol, for its effect on adipogenesis and weight loss.
Our results obtained with corn silk is consistent. Based on the above obtained results, we believe that corn silk extract and β-sitosterol can effectively reduce the pre-adipocyte differentiation and reduce the fat cells by inhibit galectin-12 activity. |
