先前的研究指出台灣金線連水萃取物具有抗氧化、降血糖及降血脂功用，這些結果顯示台灣金線可能具有減緩代謝症候群的效果。本論文進一步探討台灣金線連有效分劃 (AFEF)的降血糖作用機轉。另外，以同時具有高血糖及高血脂，肥胖及高血脂的動物模式探討AFEF的改善效果。
AFEF對正常小鼠血糖及腎上腺素誘發高血糖沒有降糖作用。對小鼠葡萄糖耐受性試驗具有降血糖的效果。對streptozotocin (STZ)誘發高血糖小鼠，單一劑量投與AFEF具有降血糖作用。對STZ誘發高血糖小鼠，長期投與AFEF，具有降血糖、糖化血紅素、膽固醇及三酸甘油脂的作用，對肝臟肝糖濃度有減少作用。西方墨點法的分析顯示AFEF能增強骨骼肌Glucose transporter Type 4 (GLUT4)蛋白的表現。RT-PCR的分析顯示，AFEF對骨骼肌GLUT4、AMP-activated protein kinase及肝臟phosphoenolpyruvate carboxykinase mRNA的表現有增強作用。
對STZ糖尿病小鼠餵食高脂肪飼料同時誘發及高血脂，AFEF具有降血糖、降膽固醇及降三酸甘油脂的作用。對此模型，AFEF也能降低低密度脂蛋白，同時提升高密度脂蛋白。AFEF對小鼠餵食高脂肪飼料，或酒精加高脂肪飼料所造成的肥胖沒有減輕的作用。
結論，AFEF具有降血糖、降血脂的作用，但對肥胖沒有改善的效果。AFEF降血糖機轉是活化骨骼肌中 AMPK而改善骨骼肌對葡萄糖的吸收。
Previous studies have indicated that aqueous extracts of Anoectochilus formosanus (AFE) have antioxidative, hypoglycemic and anti-hypertriglyceridemic effects. These studies suggest that AFE may have benefits for metabolic syndromes. In the present study, we further examined the anti-hyperglycemic mechanisms of A. formosanus effective fraction (AFEF). In addition, we also investigated the amelioratory effects of AFEF on the hyperglycemic and hyperlipidemic, and obesity and hyperlipidemic animal models.
AFEF did not reduce the blood glucose levels in normal mice and epinephrine-induced hyperglycemic mice. AFEF suppressed the elevated blood glucose concentrations on glucose tolerance test in mice. Single administration of AFEF could inhibit the blood glucose levels in streptozotocin (STZ)-induced hyperglycemic mice. Chronic treatments with AFEF could reduce blood levels of glucose and glycated hemoglobin, and serum concentrations of triglycerides and cholesterol in STZ-induced hyperglycemic mice. AFEF also decreased the hepatic glycogen levels. In STZ-induced hyperglycemic mice, Western blot analysis showed that AFEF inhibited the glucose transporter type 4 (GLUT4) protein expression in skeletal muscle. AFEF also decreased the mRAN expression of GLUT4 and AMP-activated protein kinase in skeletal muscle, and suppressed hepatic phosphoenolpyruvate carboxykinase mRNA expression.
In a model that combined high-fat diet-induced hyperlipidemia with STZ-induced hyperglycemia in mice, AFEF could attenuate the blood levels of glucose, triglycerides and cholesterol. In this model, AFEF not only decreased LDL cholesterol, but also increased HDL cholesterol. However, AFEF did not decrease the obesity induced by high-fat diet or by high-fat diet supplied with drinking water containing 10% alcohol.
In conclusion, AFEF has anti-hyperglycemic anti-hyperlipidemic effects. But, AFEF has no anti-obesity activity. The hypoglycemic mechanisms of AFEF are due to activation of AMPK to improve the resistance of glucose uptake into skeletal muscle in diabetic mice.
