Investigation on the Active Hypoglycemic Components of Siraitia Grosvenori by Glucose Uptake Assay in 3T3-L1 Adipocytes

糖尿病是一種體內葡萄糖恆定失調的代謝性疾病，主要由於胰島素分泌或胰島素作用有缺陷，而影響血中葡萄糖進入肝臟、肌肉及脂肪等組織所引起的高血糖。脂肪與肌肉細胞皆為受胰島素調控來維持血糖恆定的主要組織。文獻指出，週邊組織攝入葡萄糖，對於血糖的恆定及清除餐後血糖是很重要的步驟。因此，評估細胞的葡萄糖攝取能力，在糖尿病相關研究中，扮演一個很基礎的角色。羅漢果的食用、藥用價值已有很悠長的歷史。除了甜味的特性之外，研究也發現羅漢果在體內與體外試驗中，均具有降血糖之活性。因此本次實驗目的為利用3T3-L1脂肪細胞之葡萄糖攝取試驗為篩選模式，找出羅漢果中可能具有降血糖活性之成分。結果顯示，羅漢果粗萃物能夠顯著提升脂肪細胞的葡萄糖攝取量，且具濃度效應。將粗萃物依極性區分後，發現以乙酸乙酯層的效果最佳。更進一步將乙酸乙酯層利用管柱層析分離後，在其次區分層中分離出S1、S2與S3；此三個樣品皆能顯著增加脂肪細胞的葡萄糖攝取能力。當單純以樣品處理時，S1具有最好的效果，然而與胰島素共同處理下，S1則降低了胰島素的活性。經由西方點墨法分析，發現S1本身可增加Akt磷酸化；S2的促進效果同時存在於單獨處理與有10 nM胰島素刺激的狀況。綜合以上結果，推測S1具有類似胰島素之作用，S2應有協同胰島素作用之活性。Diabetes mellitus is a metabolic disorder characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Muscle and fat cells are both insulin-stimulated target tissues which regulate the blood glucose concentration. Glucose uptake in target tissues is a critical step in maintaining glucose homeostasis and clearing the postprandial glucose load. Therefore, evaluation of glucose uptake ability in cells plays a fundamental role in diabetes research. Siraitia grosvenori (SG), also called Luo-Han-Guo (LHG), is a fruit used in traditional Chinese medicine and also used as food additives. Besides its sweet taste, studies showed that LHG-extract exhibited an antidiabetic effect on both in vivo and in vitro trials. The aim of this study is to find the active compounds with hypoglycemic potential in LHG by glucose uptake assay in 3T3-L1 cells. LHG crude extract increased glucose uptake in a dose-dependent manner, and after solvent partition of crude extract, the ethyl acetate fraction showed the best glucose uptake activity. There were three components (S1, S2 and S3) separated from EA fraction by column chromatography, and all of them can significantly increase glucose uptake activity in 3T3-L1 adipocytes. Among them, S1 showed the best activity in basal glucose uptake. In combination with insulin, however, S1 slightly reduced insulin-stimulated glucose uptake. By western blot analysis, S1 enhanced the phosphorylation level of Akt. S2 was found to have a promotion effect on both basal and insulin-stimulated glucose uptake. In conclusion, S1 had an insulin-mimetic action and S2 showed synergistic effect with insulin in 3T3-L1 adipocytes