骨骼肌耗損為癌症惡病質(cancer cachexia) 的主要病徵,耗損的起因是因是病患透過泛素化蛋白酶途徑(Ubiquitin -proteasome pathway,UPP) 和自噬溶酶體途徑(Autophagy-lysosome pathway,ALP) 過度分解肌肉蛋白(例如: Myosin heavy chain,MyHC) 來獲取能量所造成的結果。本實驗是利用老鼠皮下注射路易斯氏肺癌細胞誘發癌症惡病質做為肌肉萎縮的實驗模式。在該實驗模式中發現肌肉內之UPP 和ALP 受到活化,UPP的代表性蛋白,包括Muscle RING finger 1 (MuRF1)、Muscle atrophy F-box1 (Atrogin1),ALP 的代表性蛋白,包括Beclin1 和light chain 3 (LC3) 均因UPP 和ALP 的活化而有顯著上升。此外,UPP 和ALP 的上游調控基因,如: IκB kinase / Inhibitor κB-α (IKK /IκB-α)、Phosphorylated adenosine monophosphate-activated protein kinase /Forkhead box protein 1 (pAMPK /FoxO1)、Protein kinase B (AKT)/ FoxO1 其表現的蛋白質亦受到活化,最後造成MyHC 降解,產生癌症惡病質肌肉萎縮的症狀。接著利用沙棘葉水萃物處理實驗動物,觀察上述現象是否受到沙棘葉水萃物的抑制,以評估沙棘葉水萃物減緩肌肉萎縮的功效。結果發現移植腫瘤細胞誘發腫瘤後未經任何處理的小鼠(以下簡稱誘發組),其MyHC 的蛋白含量降低,MuRF1、Atrogin1、Beclin1 和LC3 (稱為atrogenes) 的含量皆有顯著增加,且肌肉組織中發炎激素(如:Tumor necrosis factor-α (TNF-α) 和Interleukin-6 (IL-6)) 的含量增加。相較於誘發組,誘發腫瘤後灌食Sea buckthorn (SBT) 的小鼠(以下稱為LLC+SBT組),其MyHC 的蛋白含量則增加,MuRF1、Atrogin1、Beclin1 和LC3 的含量皆有顯著增低,且肌肉組織中發炎激素(例如TNF-α 和IL-6) 的含量降低,同時也減少IKK /IκB-α、pAMPK /FoxO1、AKT/ FoxO1 路徑的活化,因而達到減緩肌蛋白耗損。因此,SBT 可透過抑制UPP、ALP 及其上游的調控系統,達到減緩癌症惡病質所引起的肌肉萎縮。
Skeletal muscle wasting is a major symptom of cancer cachexia, which is caused by the degredation of muscle fibers through ubiquitin-proteasome pathway (UPP) and autophagy- lysosome pathway (ALP).The muscle atrophy model of cancer cachexia of mice was induced by the injection of Lewis lung cancer (LLC) cells subcutaneously to the mice. The effects of water extract of Sea Buckthorn leaf (SBT) on reduction of skeletal muscle atrophy were evaluated. We analyzed the marker proteins of UPP and ALP, including Muscle RING finger 1(MuRF1) , Muscle atrophy F-box1(Atrogin1) , Beclin1 ,light chain 3 (LC3) and other related proteins. The results showed that LLC (LLC- injection group) decreased the content of Myosin heavy chain (MyHC) protein and increased the amount of inflammatory cytokines, Tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6)in the muscle tissues. The expression of Atrogenes, MuRF1, Atrogin1, Beclin1 and LC3 were also increased in LLC group, however, the level of atrogenes proteins were decreased in LLC+SBT group.The activities of IκB kinase/Inhibitor κB-α (IKK /IκB-α), Phosphorylated adenosine monophosphate -activated protein kinase (pAMPK) /Forkhead box protein 1 (FoxO1) and Protein kinase B (AKT) / FoxO1 pathways were also decreased in LLC+SBT group. Therefore, we suggested that LLC+SBT could prevent the muscle wasting in cancer cachexia by inhibiting the UPP and ALP.