Quercetin合併leucine對cisplatin誘發的癌因性疲憊及肌肉流失之效果及機制探討

順鉑 (CDDP) 是一種臨床上常使用的化療藥物，雖然其抗腫瘤的效果顯著，但CDDP造成的許多副作用，包括食慾不佳、肌肉萎縮和癌因性疲憊 (Cancer-related fatigue, CRF) 等限制了其使用。我們之前的研究顯示，類黃酮槲皮素 (Q) 可部分減緩CDDP所導致的肌肉萎縮和CRF。另外，支鏈胺基酸尤其是白胺酸 (L) 已知可刺激肌肉合成並抑制蛋白質分解，我們推測合併補充槲皮素和白胺酸可相加或加成性地降低肌肉萎縮和癌因性疲憊。因此我們以動物研究探討Q和L對抗CDDP誘導的肌肉萎縮和CRF的合併效果及相關機制。我們將雄性BALB/c小鼠隨機分配至以下組別：Control組、CDDP (3 mg/kg B.W./week)、CDDP+Q (200 mg/kg B.W./day)、CDDP+LL (添加0.8 % L的飼料)、CDDP+Q+LL、CDDP+HL (添加1.6 % L的飼料) 和CDDP+Q+HL進行為期9週的實驗。我們發現單獨給予Q、LL或HL會改善CDDP引起的食物攝取、活動力、最大抓力、體重、肌肉重量，肌纖維大小及肌肉組織MyHC含量的下降，而合併補充相加或加成性地增強這些效果，尤其是Q+HL組。我們進一步發現，與CDDP組相比，所有補充劑皆增加了與肌肉降解 (泛素蛋白酶體路徑) 相關的p-Akt及p-FoxO1含量並且抑制了atrogin-1和MuRF1兩個蛋白質的表現，但是卻增加了組織中與肌肉合成有關的mTOR、p-70 S6K和4E-BP1等蛋白質的磷酸化。此外，Q和L單獨或合併補充減少DNA 損傷/細胞凋亡，降低p53的磷酸化及p21的表現，但增加了p-RB、E2F-1、cyclin D、CDK4、Ki-67和PCNA等與細胞增生有關蛋白質的表現，合併補充劑的效果優於或接近於單獨補充。此外，與CDDP組相比，HL及Q+HL顯著增加肌肉肝醣量，而所有補充劑均降低血漿或三頭肌中促發炎因子TNF-α、IL-6、IL-1β 和 MCP-1的濃度，且效果Q+HL及Q+LL > HL、LL及Q。綜上所述，我們的研究顯示合併Q和L補充可能透過降低泛素蛋白酶體路徑、p-p53/p21表現及促發炎激素濃度，但增加mTOR信號路徑、E2F-1相關肌肉細胞增生訊號分子表現及增加肌肉肝醣等機制，相加或加成性改善CDDP所引發的肌肉萎縮和癌因性疲憊。

Cisplatin (CDDP) is a common chemotherapy dug for clinical use. Despite its potent anticancer effect, the side effects of CDDP, including poor appetite, muscle wasting and cancer-related fatigue (CRF) limits its use. Our previous studies demonstrated that quercetin (Q), a flavonoid, partially attenuated CDDP-induced muscle wasting and CRF. In addition, branched-chain amino acids, especially leucine (L) are known to stimulate muscle synthesis and inhibit protein breakdown. We hypothesized that the combination of quercetin and leucine synergistically or additively attenuates the muscle atrophy and CRF. Thus, we performed an animal study to investigate the combined effect and the possible mechanisms of Q and L on muscle wasting and CRF induced by CDDP. Male BALB/c mice were randomly assigned to the following groups for 9 weeks: Control, CDDP (3 mg/kg B.W./week), CDDP+Q (200 mg/kg B.W./day), CDDP+LL (a diet containing 0.8 % L), CDDP+Q+LL, CDDP+HL (a diet containing 1.6 % L), and CDDP+Q+HL. We found that Q, LL or HL alone attenuated CDDP-induced decreases in food intake, locomotor activity, maximum grip strength, body and muscle weight, muscle fiber size and MyHC level in muscle tissues. The combined supplements additively or synergistically enhanced such effects, especially Q+HL. Furthermore, all supplements increased the expression of p-Akt and p-FoxO1 while suppressed the expression of atrogin-1 and MuRF1, which are associated with muscle protein degradation, but increased the phosphorylation of mTOR, p-70 S6K and 4E-BP1, which are associated with muscle synthesis, in muscle tissues in mice exposed to CDDP. The effects of combined treatments were better than or similar to that of individual treatment. Furthermore, quercetin and leucine combined tended to additively attenuate DNA damage/apoptosis, p53 phosphorylation and the expression of p21 but increased the levels of p-RB, E2F-1, cyclin D, CDK4, Ki-67 and PCNA, which are associated with cell proliferation. In addition, Q+HL and HL significantly increased glycogen levels in the triceps muscle compared to CDDP alone group. All supplements decreased CDDP-induced proinflammatory cytokine levels, including TNF-α, IL-6, IL-1β, and MCP-1, in plasma or triceps muscle in the following order: Q+HL, Q+LL > HL, LL, and Q. In conclusion, our study suggests that the combination of Q and L additively or synergistically attenuated CDDP-induced muscle wasting and CRF through the mechanisms associated with downregulation of ubiquitin proteasome pathway, the expression of p-p53/p21 and proinflammatory cytokine levels but up-regulation of mTOR signaling pathway, E2F-1 associated cell proliferation pathway and glycogen level in muscle tissues in mice exposed to CDDP.