探討丙烯醛影響骨骼肌分化/再生及醣類代謝之機制

Acrolein Impairs Skeletal Muscle Myogenesis and Glucose Metabolism

陳煌仁(Huang-Jen Chen)

指導教授 ： 劉興華

國立臺灣大學/醫學院/毒理學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10548

摘要

環境汙染物丙烯醛(acrolein)為液狀小分子化合物，具有不飽和羰基鍵，易與親核性分子結合。而環境中丙烯醛暴露主要來自物質不完全燃燒、油炸食物與抽菸等，其中又以抽菸為大宗。除了經由環境接觸丙烯醛外，丙烯醛也會透過氧化壓力和脂肪過氧化於人體內生成。暴露過量丙烯醛可能與阿茲海默症、腎衰竭與糖尿病成因相關，過往研究發現糖尿病患者與重度吸菸者其尿液中丙烯醛共價鍵結物皆顯著增加，且腎臟疾病病患常併發骨骼肌功能下降，而骨骼肌為人體主要代謝醣類的組織。已有文獻指出丙烯醛會造成骨骼肌肌管細胞萎縮，但對丙烯醛於骨骼肌分化/再生及醣類代謝機制仍待釐清。因此，本研究利用細胞與動物模式探討丙烯醛在骨骼肌肌肉生成(myogenesis)和醣類代謝上之角色。首先經由hematoxylin and eosin (H E)染色發現丙烯醛(0.125-1 μM)具劑量關係阻滯肌纖維母細胞(C2C12 myoblast)分化，同時抑制調節肌細胞能量之肌酸激酶活性。以西方墨點法分析，發現丙烯醛(1 μM)顯著減少骨骼肌分化指標蛋白(myosin heavy chain, myogenin and phospho-Akt)表現和抑制骨骼肌醣類代謝相關蛋白表現。丙烯醛亦造成細胞內肝醣含量增加與葡萄糖攝入減低。過度表現持續性活化態Akt於肌細胞內能恢復丙烯醛抑制之肌酸激酶活性、骨骼肌分化指標蛋白表現及葡萄糖運輸蛋白(glucose transporter 4)表現。動物模式方面，經由管餵小鼠丙烯醛四週(2.5 and 5 mg/kg)後，造成小鼠明顯體重下降且血糖躍升、胰島素驟降，其口服葡萄糖耐受性試驗丙烯醛暴露組呈現高峰延滯分布。藉由滾輪跑步裝置偵測小鼠肌肉強度，丙烯醛(5 mg/kg)造成小鼠肌肉強度下降。當小鼠進行甘油注射致骨骼肌受損試驗(experimental glycerol myopathy model)並再生五天後，丙烯醛(2.5 and 5 mg/kg)導致小鼠肌肉強度下降且比目魚肌重量顯著減少、其骨骼肌復原情形明顯受丙烯醛(2.5 and 5 mg/kg)阻滯。綜合上述，本研究發現丙烯醛抑制肌纖維母細胞分化與骨骼肌再生，並影響骨骼肌醣類代謝，導致小鼠血液葡萄糖濃度增高，其詳細機制在未來仍待探討。

關鍵字

丙烯醛 ； 骨骼肌 ； 肌肉生成 ； 醣類代謝 ； 肌纖維母細胞

並列摘要

Acrolein is a small molecule and extremely electrophilic aldehyde from foods, environment and tobacco. The endogenous sources of acrolein are related to metabolism of the anticancer drug cyclophosphamide and lipid peroxidation. Acrolein provokes its harmful influences through oxidative stress or inflammation during degradation of threonine and spermidine. High level acrolein was an environmental risk in daily unsaturated aldehyde consumption that contributed to the pathogenesis of Alzheimer’s disease, renal failure and diabetes. Dysfunction of skeletal muscle occurs in renal failure and diabetes patients that is due to oxidative stress and chronic inflammation. Besides, the urinary levels of acrolein adduct were both increased in type 2 diabetes and smoking habit. However, the effects of acrolein on myogenesis and glucose homeostasis in skeletal muscle still remain unclear. A non-cytotoxic dose of acrolein (1μM) repressed myogenic differentiation on C2C12 myoblasts, and then inhibited myotube formation by hematoxylin and eosin (H E) staining and creatinine kinase activity. Myogenic protein expressions (myosin heavy chain, myogenin and phosphorylation of Akt) were also decreased with acrolein treatment. Furthermore, glucose utilization plays an essential role of myogenesis and GLUT4 expresses predominant in skeletal muscle which responded to glucose uptake. Acrolein (1 μM) impaired glucose homeostasis by inhibition of protein expressions of glucose metabolic signalling on skeletal myotubes in vitro. Over-expression of constitutive activation of Akt on differentiation of C2C12 myoblasts reversed the expression of inhibitory myogenic makers and GLUT4 induced by acrolein. Moreover, acrolein (2.5 and 5 mg/kg/day) significantly retarded skeletal muscle regeneration in murine soleus muscles and exercise performance (rotarod) after glycerol injured soleus muscle. Exposure of ICR mice to acrolein prominently increased blood glucose, impaired glucose tolerance and decreased plasma insulin. Taken together, these results suggest that acrolein exposure is capable of impairing the myogenesis and glucose metabolism in vitro and in vivo. The further mechanism(s) will be investigated in the future.

並列關鍵字

acrolein ； skeletal muscle ； myogenesis ； glucose metabolism ； myoblast ； Akt ； glucose transporter

參考文獻

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