| Abstract: | 秋葵(Okra, Abelmoschus esculentus fruits) 富含機能性成份包括類黃酮化合物及多醣。文獻已證實，秋葵具有降血脂、降低膽固醇、保肝、抗氧化、抑菌等生理活性，其類黃酮衍生物能改善小鼠肝細胞胰島素阻抗性。然秋葵多醣於血糖調節研究甚少，因此本研究欲探討秋葵多醣對胰島素阻抗小鼠調節血糖機制之影響。500 g乾燥秋葵粉末以熱水萃取，再利用75%乙醇沉澱，並反覆沖洗後乾燥的多醣約得70.65 g，產率為14.13%。此粗萃樣品中的總糖、蛋白質及總酚百分含量，分別為91.30%、7.49%及2.31%，分子量平均約2.35×104 kDa。為模擬現代人高熱量飲食習慣，以30%高果糖漿誘導小鼠形成胰島素性阻抗及高血糖後，並給予秋葵多醣。結果顯示，經十六週試驗後，顯著改善葡萄糖耐受性不良，降低小鼠肝功能指標、肝臟中TNF-、血清中三酸甘油酯、膽固醇、果糖胺及抗素濃度，且能提高脂聯素含量。肝臟中胰島素傳訊方面，餵食樣品後可增加傳訊分子IR-β、PI3K、Akt、pAkt 、AMPK、pAMPK和GLUT2表現量，亦抑制PEPCK、GSK3β、和FoxO1的表現，並具劑量效應。此外，肝臟組織學切片的H&E和油紅染色中，高糖誘導組可發現大量的油滴堆積與組織排列混亂，而給予樣品後能減少此情況。綜合上述結果證實，秋葵多醣可提高肝臟胰島素敏感度，增加葡萄糖攝入及肝醣合成，抑制糖質新生反應，進而達到血糖恆定作用。
Okra (Abelmoschus esculents fruits) are rich in functional ingredients, including polysaccharides and flavonoids. Recent studies have demonstrated that okra may provide antioxidative, antibacterial, hepatorprotecetive, hypolipidemic and hypocholesterolemic effects. Previous studies have showed that insulin resistance of FL83B cells may be improved by okra flavonoid derivatives. Nevertheless, hypoglycemic mechanisms of okra polysaccharides have not yet been fully documented. In this study, glucose homeostatic activities of okra polysaccharides were investigated in an insulin reisistance murine model. The okra polysaccharide (70.65 g) was extracted from 500 g lyophilized powder after being soaked in hot water, precipitatied by 75% ethanol, and dried, giving 14.13% yield. The contents of total polysaccharides, total phenols, total proteins, of this crude extract were 91.30%, 7.48%, 2.31 %, respectively, and the MW was estimated to be 2.35×104 kDa. The mice were induced to be insulin resistant and hyperglycemic by high fructose, then were administered with okra’s polysaccharide. After sixteen weeks, okra feeding group showed significant improvement in oral glucose tolerance, serum hepatic function parameters, sTG, sTC, fructosamine, serum resistin, serum adiponectin, and hepatic TNF- production. Insulin signaling in hepatocytes was concordantly enhanced, as revealed by the upregulating the test group of protein or mRNA relative performance were enhanced, IR-β, PI3K, Akt, pAkt, AMPK, pAMPK and GLUT2,and the down regulation of PEPCK, GSK3β, FoxO1, in a dose-dependent manner. Moreover, okra’s polysaccharide seemed to ameliorate the pathological conditions in hepatic panlobular microvesicular and tissue arrangement as demonstrated by histological evaluation by H&E and oil-red-O stains. In conlusion, okra polysaccharide may improve glucose homeostasis by increasing hepatic isnulin sensitivity, glucose uptake, glycogen synthesis, while suppressing gluconeogenesis. |
