初探山苦瓜萃取物之雄激素受體調節相關活性

An Initial Study on the Selective Androgen Receptor Modulator Related Activities of Wild Bitter Gourd

劉又禎(Yu-Chen Liu)

指導教授 ： 黃青真

國立臺灣大學/生命科學院/生化科技學系/碩士(2017年)

https://doi.org/10.6342/NTU201702199

摘要

老年男性體內雄激素下降造成骨骼肌逐漸退化並流失，但補充雄激素以提升肌肉質量及肌力，則可能伴隨攝護腺癌發生的風險。攝護腺癌的發生主要與年齡有關，而遺傳或是飲食所致肥胖也是罹患攝護腺癌的潛在危險因子。攝護腺的生長由雄激素及其受體調節，而此路徑也被認為與攝護腺癌化有關。以雄激素阻斷療法 (androgen-deprivation therapy, ADT)可以控制攝護腺癌細胞生長，但雄激素缺乏可能影響肌肉功能。若以選擇性雄激素受體調節劑 (selective androgen receptor modulators, SARMs)作為治療藥物則能夠選擇性的抑制攝護腺癌細胞生長且不影響肌肉質量。
苦瓜 (Momordica charantoa L.)被認為具有治療攝護腺癌的潛力。而其所含三萜類化合物以不帶醣基的形式促進細胞葡萄糖汲取之活性最高。本實驗室先前研究觀察到山苦瓜萃取物可調節雄激素受體轉錄活性，擬進一步探討其是否具有類似「選擇性雄激素受體調節劑 (Selective Androgen Receptor Modulator, SARM)」之特性。故本實驗以不同溫度對多種品系之山苦瓜進行水解再以乙酸乙酯萃取得低極性之活性物質，觀察其為SARM之可能性。
實驗結果，比較各品系山苦瓜及其水解產物之萃取物，山苦瓜P81品系50℃水解產物之乙酸乙酯萃取物 (P81 50℃hEAE)調節雄激素受體轉錄活性最佳。於50 µg/mL時能夠顯著的提高28.0%之AR轉錄活性，在有10 nM 5α-DHT共同處理之下能夠抑制其30.2%之轉錄活性，似為partial agonist符合SARMs之特徵。而200 µg/mL之P81 50℃hEAE抑制21.1%的雄激素依賴型攝護腺癌細胞LNCaP增生，共同處理0.1及10 nM 5α-DHT之下則分別抑制24.8%及33.6%的LNCaP增生，故在攝護腺癌細胞中為antagonist並同樣符合SARMs的特性。另外，共同處理bicalutamide以阻擋AR的結合位，則可部分挽回200 µg/mL P81 50℃hEAE抑制增生的效果，顯示該抑制作用應涉及AR之調控。而P81 50℃hEAE在有無共同處理0.1 nM 5α-DHT之下，皆使LNCaP之細胞週期停滯在G0/G1 phase並降低細胞遷移的能力，且可抑制該細胞中雄激素受體相關基因KLK3、IGF-1及IGF-1R的表現。在餵食高脂或高脂添加4%山苦瓜粉末飲食四週之C57BL/6J小鼠實驗中，雄激素相關組織攝護腺及提肛肌之重量與該組織中雄激素受體調節基因之表現量並未受到飲食處理有顯著影響。
根據以上實驗結果，P81 50℃hEAE可調節雄激素受體轉錄活性，但於雄激素依賴型攝護腺癌細胞又抑制其生長及雄激素下游之基因表現。故初步判定山苦瓜具有SARMs之特質。

關鍵字

山苦瓜 ； 雄激素 ； 雄激素受體 ； 選擇性雄激素受體調節劑 ； 雄激素依賴型攝護腺癌細胞LNCaP

並列摘要

Decreased androgen associated with aging is considered one of the causes of sarcopenia. Androgen replacement can rescue the skeletal muscle mass and function, but may increase risk of prostate cancer. Prostate cancer develops mainly in senior men, but family history and diet-caused obesity are also risk factors of prostate cancer. Normal development of the prostate is dependent on androgen acting through the androgen receptor, and androgen remains important in the progression of prostate cancer. Androgen deprivation therapy (ADT) reduces levels of androgen and discontinue its effect on prostate cancer cells, but androgen deficiency may lead to decline in skeletal muscle function. In this regards, selective androgen receptor modulators (SARMs) have been developed as therapeutics that can selectively inhibit prostate cancer cell growth but maintain skeletal muscle mass.
It has been reported that bitter gourd (Momordica charantoa L., BG) inhibited growth of prostate cancer cells. Preliminary data in our laboratory showed that the ethyl acetate extract (EAE) wild bitter gourd (WBG) modulated the androgen receptor transactivation activity. This study aims to investigate the potential of the WBG EAE as selective androgen receptor modulator (SARM). EAEs of various cultivars of the WBG and hydrolyzed WBG were examined and compared.
Among WBG cultivars tested, the EAE of the 50℃ hydrolyzed P81 (P81 50℃hEAE) showed highest effect on modulating the androgen receptor transactivation activity. Acting as a partial agonist, 50 µg/mL of P81 50℃hEAE significantly increased 28.0% of the AR transactivation activity but suppressed 30.2% of the transactivation activity of 10 nM 5α-DHT when co-treated. In the androgen-dependent prostate cancer cell LNCaP, 200 µg/mL P81 50℃hEAE showed 21.1% inhibition on cell proliferation. In the presence of 0.1 or 10 nM 5α-DHT, there were 24.8% or 33.6% inhibition in the LNCaP proliferation. In LNCaP cells, P81 50℃hEAE acted as an antagonist, in line with the features of SARMs. Moreover, co-treatment with bicalutamide partially recovered the inhibition effect of 200 µg/mL P81 50℃hEAE on LNCaP cells proliferation, suggested that the inhibition of P81 50℃hEAE is related to AR. Moreover, P81 50℃hEAE induced cell growth arrest in the G0/G1 phase, impaired the migration and down-regulated the expressions of androgen receptor related genes, KLK3, IGF-1 and IGF-1R either in the absence or presence of 0.1 nM 5α-DHT. Groups of C57BL/6J mice were fed a high fat diet or 4% WBG supplemented high fat diets for four weeks. Tissue weights and the mRNA expressions of androgen receptor target genes of androgen-sensitive tissues, prostate and levator ani muscle, were not significantly different among groups (p>0.05).
In conclusion, P81 50℃hEAE can modulate the androgen receptor activity, inhibit LNCaP cell growth and androgen receptor related genes expression. It is speculated that WBG might have health benefit as SARMs.

並列關鍵字

wild bitter gourd ； androgen ； androgen receptor ； selective androgen receptor modulators (SARMs) ； androgen-dependent prostate cancer cell LNCaP

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