利用 STZ誘發之糖尿病大鼠及C2C12細胞株探討土肉桂葉精油之抗糖尿病作用機制

A study on the mechanism of anti-diabetic effects of leaf essential oil of Cinnamomum osmophloeum Kaneh. by using STZ-induced diabetic rats and C2C12 cell line

柯千惠(Chien-Hui Ko)

指導教授 ： 劉承慈

中山醫學大學/健康管理學院/營養學研究所/碩士(2012年)

https://doi.org/10.6834/CSMU.2012.00188

摘要

本研究室過去研究發現，台灣本土土肉桂葉精油 (TC) 對DM大鼠具有改善口服葡萄糖耐受性及胰島素耐受性之功能，並有抗氧化及抗發炎之效果。本研究目的是以活體與體外研究方法探討土肉桂葉精油改善血糖之機制。動物實驗以STZ (65 mg/kg BW) 誘發大鼠DM，隔日灌食精油 (13、26或54 mg/kg BW) 及肉桂醛 (40 mg/kgBW；CA)，且以口服降血糖藥glibenclamide (1.2 mg/kgBW；GC) 做為正控制組，另在控制組灌食載劑玉米油 (corn oil, 2 ml/kg BW)，共灌食八次。細胞實驗使用C2C12細胞株，在細胞分化6天後，給予精油 (0.2 μg/ml、2 μg/ml、20 μg/ml) 預處理2小時，以DMSO (0.1%) 作載劑當控制組，並給予linalool 0.8 μg/ml作為對照組。動物實驗結果顯示，土肉桂葉精油具有遏止糖尿病進行的效果，且效果優於肉桂醛及GC。TC劑量在26 mg/kg能夠提升周邊insulin濃度並達到與control組無顯著差異且效果優於肉桂醛及GC，但非透過影響PDX-1的表現改善糖尿病之胰島素分泌。另一方面，糖尿病顯著降低骨骼肌及脂肪組織之IR-beta及GLUT4表現量、Akt-ser與Akt-thr磷酸化程度、及PI3K活性，並提升SOCS3表現量。在肌肉，土肉桂葉精油在劑量13 mg/kg能夠增強GLUT4表現量及Akt-ser與Akt-thr磷酸化程度，而26 mg/kg之TC可提升PI3K活性，且26及54 mg/kg之土肉桂葉精油、肉桂醛與口服降血糖藥能降低糖尿病動物肌肉中SOCS3表現量。在脂肪組織，所有劑量TC、CA及GC皆顯著提高IR-beta表現量，且低劑量TC顯著提高GLUT4表現量，提升PI3K活性，並顯著降低SOCS3表現量。細胞實驗結果顯示，在無胰島素時，TC不影響IR-beta及GLUT4表現量、Akt-ser與Akt-thr磷酸化程度、PI3K活性、及葡萄糖攝取量。而在胰島素刺激下， TC濃度在0.2 μg/ml時能夠增強IR-beta及GLUT4表現量與提升PI3K活性，在濃度2μg/ml時能夠增強Akt-ser與Akt-thr磷酸化程度，並顯著增加其葡萄糖攝取量，且效果均優於linalool組，而0.2 μg/ml TC與linalool能降低SOCS3表現量。由本研究結果得知，TC在適當劑量下可改善周邊胰島素敏感性，其效果與改善胰島素訊號相關蛋白表現量及訊號分子活化有關。

關鍵字

糖尿病 ； STZ ； 土肉桂葉精油 ； 胰島素分泌 ； 胰島素阻抗 ； 胰島素訊號

並列摘要

According to previous study, cinnamon extract possesses an anti-diabetic effect. Our previous study have found the leave essential oil of Cinnamomum osmophloeum Kaneh.(TC) improves oral-glucose tolerance and insulin tolerance in diabetic rats and it is associated with both anti-oxidant and anti-inflammatory effects. The aim of the present study is to investigate the mechanism underlying which TC affects blood glucose control in diabetes with in vivo and in vitro studies. Male Wistar rats were induced to be diabetes with Streptozotocin (STZ, 65mg/kg BW) and received every other day for eight times by gavage TC (13、26 or 54mg/kg BW), cinnamaldehyde (CA, 40 mg/ kg BW), glibenclamide (GC, 1.2mg/kg BW) or vehicle (corn oil, 2ml/kg BW). In vitro, C2C12 myotubes were induced to differentiate for 6 days, followed by pre-treatment with TC (0.2 μg/ml、2 μg/ml、20 μg/ml) for 2 hours. DMSO (concentration in culture???) was used as vehicle and linalool (0.8 μg/ml) was used as positive control. In vivo, it showed that TC restrained DM progressing, and was more effective than CA and GC. At the dose 26 mg/kg, TC increased plasma insulin concentration to a level similar to that of the control group, and was more effective than that of CA and GC. It does not seem that the ameliorated peripheral insulin level was via the regulation on PDX-1 expression. Diabetes suppressed the expression of IR-beta, GLUT4, phosphorylation of Akt-ser and Akt-thr, and the activity of PI3K, while induced the expression of SOCS3 in skeletal muscle and adipose tissue.In skeletal muscle tissues, it showed that 13 mg/kg of TC up-regulated the expression of GLUT4, increased phosporylation of Akt-ser and Akt-thr, 26 mg/kg of TC increased the activity of PI3K, and all doses of TC except the lowest dose, CA and GC suppressed diabetes-induced elevation of SOCS3 expression. In adipose tissue, all treatment promoted the expression of IR-beta and13 mg/kg of TC increased the expression of GLUT4, the activity of PI3K, and lowered expression of SOCS3 in diabetic rats. In vitro, the expression of IR-beta, GLUT4, phosporylation of Akt, activity of PI3K, and glucose uptake rate showed not affected by the differentiated C2C12 muscle cell line in the absence of insulin. However, 0.2 μg/ml of TC promoted insulin-induced expression of IR-beta and activity of PI3K to a higher extent than that of linalool. Similarly, 2 μg/ml of TC promoted insulin-induced phosphorylation of Akt and glucose uptake rate to a higher extent than that of linalool. Pretreat the cells with 0.2 μg/ml of TC and with linalool down-regulated the expression of SOCS3. In summary, the present study demonstrated that TC improved insulin sensitivity in vivo and in vitro under the appropriate dose, and its effects is associated with improved insulin signaling protein expression and activation.

並列關鍵字

Diabetes mellitus ； Streptozotocin ； Cinnamomum osmophloeum Kaneh. ； insulin secretion ； insulin resistance ； insulin signal

參考文獻

行政院衛生署統計處(2010)，國民十大死因統計結果

許文馨 (2010)，土肉桂葉精油在STZ-糖尿病大鼠之降血糖作用

張皓瑜 (2011), 土肉桂葉精油對於STZ誘發之糖尿病大鼠發炎體相關蛋白質表現及腎臟病變發展之影響

顏嘉均 (2011)，土肉桂葉精油對糖尿病大鼠之抗氧化及抗發炎作用

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