土肉桂葉精油於第2型糖尿病小鼠模式胰島素增敏及腎臟保護作用之探討

A study on insulin-sensitizing and renal-protective effects of leaf essential oil of Cinnamomum osmophloeum Kanehira in a mouse model of type 2 diabetes

蔡幸芬(Hsing-Fen Tsai)

指導教授 ： 劉承慈

中山醫學大學/健康管理學院/營養學系碩士班/碩士(2014年)

https://doi.org/10.6834/CSMU.2014.00117

摘要

糖尿病(DM)為現代化社會流行的慢性病之一，並已嚴重威脅人們的健康。血糖控制不良是導致此併發症的重要原因之一，且糖尿病患者伴隨著胰島細胞功能衰退或胰島素阻抗，並會發展出腎功能損傷和發炎反應。過去發現台灣本土土肉桂葉精油（TC）對於 STZ誘發之第1型 DM大鼠具有改善口服葡萄糖耐受性及保護胰臟之功能，並有抗氧化及抗發炎之效果。本研究之目的為探討 TC於第2型DM小鼠模式之胰島素增敏及腎臟保護作用及相關機制。動物實驗以 C57BL/6雄性小鼠腹腔注射 STZ連續 5日（40 mg/kg BW/日）誘發糖尿病，正常控制組小鼠則注射等體積之載劑 (1M檸檬酸緩衝液, pH=4.2)，注射結束後一週起，糖尿病小鼠每隔一日灌食 TC（6.5、13、26 mg/kg BW）、Lin (10.4 mg/kg BW)、或灌食載劑玉米油 (4 ml/kg BW)，正常控制組亦灌食載劑玉米油，共灌食八次然後以二氧化碳窒息法犧牲，收集樣品進行分析。細胞實驗使用 C2C12細胞株，在細胞分化6天後，給予C-peptide (0 nM、0.5 nM、2.5nM)，TC (0 μg/ml、0.2 μg/ml、1.0 μg/ml、5.0 μg/ml)，胰島素(0 nM、150 nM)來探討。動物實驗結果顯示，灌食不同劑量的 TC及 Lin可改善 DM小鼠的代謝狀況及骨骼肌流失，逆轉 STZ誘發的空腹高血糖、伴隨改善之高胰島素血症(以C-peptide為指標)及 HOMA-IR指數。抗發炎方面，不同劑量的 TC及 Lin可降低腎臟、骨骼肌之 IL-1β、TNF-α、NO之含量。腎功能方面，不同劑量的 TC及 Lin均可改善 DM小鼠之 ACR和 BUN並且與降低之腎臟 sRAGE含量有關。另一方面，糖尿病顯著降低骨骼肌之 IR-β、GLUT4表現量、Akt-thr與 Akt-ser磷酸化程度，並提升 SOCS3表現量，於肌肉中，低、中、高劑量 TC能增強 Akt-thr磷酸化程度，而中劑量 TC可顯著增加 GLUT4的表現，但對於 IR-β、Akt-ser及 SOCS3的表現量並無顯著改善。細胞實驗結果顯示，在未顯著影響 C2C12肌肉細胞株之生長情況下，C-peptide會降低胰島素刺激之葡萄糖攝取速率，而 TC不論在無/有胰島素刺激時，均增加葡萄糖攝取。由本研究結果得知，TC在此 第2型 DM小鼠具有促進胰島素敏感性及保護腎臟的作用。TC的胰島素增敏作用不僅來自其直接促進骨骼肌攝取葡萄糖之活性，且亦來自其降低周邊血中 C-peptide濃度及在骨骼肌之抗發炎作用。此外，TC在此第2型DM小鼠促進腎功能之作用至少有部分是透過改善腎臟中 sRAGE含量及在腎臟之抗發炎作用。而 Linalool可能是 TC組成分中上述作用的主要成分。

關鍵字

糖尿病 ； 鏈黴素 ； 土肉桂葉精油 ； 枷羅木醇 ； 胰島素阻抗 ； 腎功能

並列摘要

Diabetes Mellitus (DM) is one of the chronic diseases of modern life-style and seriously threatens people's health. Patients with DM suffer from islet cell failure and insulin resistance and will develop complications including renal damage. Poor glycemic control is assoicated with complications of this disease. According to the results of our previous study, the leave essential oil of Cinnamomum osmophloeum Kanehira (TC) improves oral-glucose tolerance partly through the protective effect on pancreas which is associated with its anti-oxidant and anti-inflammatory effects in a type 1 DM model in rats induced with Streptozotocin (STZ) The aim of present study is to investigate insulin-sensitizing and renal-protective effects of leaf essential oil of TC in a mouse model of type 2 DM and the underlying mechanism. Male C57BL / 6 mice were induced to be Diabetes by the injection of streptozotocin (STZ, 40 mg/kg BW/day) intraperitoneally for 5 consecutive days. Normal control mice were injected with the administration of TC or linalool (Lin) started at a week after the end of the injection. Diabetic mice received every other day for eight times by gavage TC (6.5,13,26 mg / kg BW), Lin (10.4 mg / kg BW) or the vehicle (corn oil, 4 ml / kg BW). Normal control mice also received the vehicle. Mice were then sacrificed by CO2 and followed by the collection of samples for analysis. In vitro, C2C12 cells were were induced to differentiate into myotubes for 6 days, followed by culturing in medium with the addition of C-peptide (0 nM, 0.5 nM, 2.5nM) or TC (0 μg / ml, 0.2 μg / ml, 1.0 μg / ml, 5.0 μg / ml in the presence or absence of insulin (150 nM). It was found that all tested doses of TC and Lin improved the metabolic condition, reversed the loss of skeletal muscle, improved fasting blood glucose level, ameliorated hyperinsulinemia (with C-peptide level as an index) and HOMA-IR value in the Diabetic mice. As to the anti-inflammatory effects, TC and Lin reduced levels of IL-1β, TNF-α and NO in kidney and skeletal muscle. As to the renal function effects, both ACR and BUN in Diabetic mice were ameliorated by TC and Lin and this is associated with lowered level of sRAGE in kidney. On the other hand, diabetes significantly suppressed the expression of IR-β, GLUT4 and the phosphorylation of Akt-thr and Akt-ser, and enhance SOCS3 expression in skeletal muscle. All tested doses of TC enhance the phosphorylation level of Akt-thr, while the medium dose of TC increased GLUT4 expression, but none of the tested doses of TC affected the expression of IR-β, Akt-ser, or SOCS3. In vitro, at the doses that did not significantly affect the growth of C2C12 muscle cell line, C-peptide reduced the rate of insulin-stimulated glucose uptake, while TC improved the rate of gucose uptake both in the absence and in the presence of insulin. In summary, the present study demonstrated that TC posesses insulin sensitizing and renal protective effects in the type 2 DM mice. The insulin sensitizing effect of TC is not only via a direct beneficial effect on skeletal muscle glucose uptake but also via the lowering of peripheral C-peptide and the amelioration of muscular inflammatory condition. In addition, improved renal function by TC in the type 2 DM mice is at least partly explained by lowered sRAGE, and by ameliorated inflammatory condition in the kidney. Linalool showed to be an important active antidiabetic compound in TC possibility.

並列關鍵字

diabetes mellitus ； Streptozotocin ； Cinnamomum osmophloeum Kanehira ； linalool ； insulin resistance ； renal function

參考文獻

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