苦瓜乙醇萃取物可能藉由抗氧化及抗發炎之作用機轉而具有改善小鼠酒精性脂肪肝之功效

Liver Protective Function of Ethanol Extracts from Bitter Melon Against Alcoholic Fatty Liver in Mice by Attenuating Oxidative Stress and Inflammatory Response

曾惠君(Hui-Chun Tseng)

指導教授 ： 沈立言

國立臺灣大學/生物資源暨農學院/食品科技研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.02110

摘要

肝臟為代謝酒精之主要器官，若過量攝取酒精會導致酒精性肝臟疾病（alcoholic liver disease, ALD），依其病程可分成三階段：第一階段為酒精性脂肪肝（alcoholic fatty liver），第二階段為酒精性肝炎及肝纖維化，最後第三階段形成肝硬化，其發病機制與酒精代謝所造成之氧化壓力及發炎反應密切相關。苦瓜（Momordica charantia L.）已有千年食用歷史，傳統用於改善糖尿病，並具有多種生理功效。文獻指出，苦瓜乙醇萃取物富含多酚類物質，相較於其他溶劑之萃取物，具較高之抗氧化能力。因此，本研究以Lieber-DeCarli酒精液態飼料誘導小鼠酒精性脂肪肝之動物模式，進行四種不同苦瓜品系乙醇萃取物之護肝功效評估。實驗分成六組，分別為正常控制組、酒精誘導脂肪肝負對照組及酒精誘導脂肪肝以苦瓜「花蓮1號」乙醇萃取物、苦瓜「花蓮2號」乙醇萃取物、苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物處理組，餵食劑量皆為500 mg/kg bw/day。結果顯示，餵食苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物可有效改善小鼠肝臟中脂肪堆積情形，並降低血清中肝臟生化功能指標酵素天門冬胺酸轉胺酶（aspartate transaminase, AST）及丙胺酸轉胺酶（alanine transaminase, ALT）之數值。且在餵食苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物後，可回復小鼠肝臟中抗氧化物質麩胱甘肽（glutathione, GSH）含量，與提升抗氧化酵素麩胱甘肽過氧化酶（glutathione peroxidase, GPx）、麩胱甘肽過還原酶（glutathione reductase, GRd）、過氧化氫酶 (catalase, CAT）及超氧化物歧化酶（superoxide dismutase, SOD）之活性，並改善肝臟脂質過氧化情形及降低肝臟發炎反應。進一步以西方墨點法評估相關蛋白表現量，結果顯示，給予苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物後，小鼠肝臟中SREBP-1c、FAS及ACC之蛋白表現量皆顯著降低，由此結果推論，苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物可能藉由改善肝臟發炎反應，而減少SREBP-1c表現量，進而降低FAS及ACC等酵素活性，因此可減緩酒精所導致之脂質堆積情形。而苦瓜「花蓮1號」乙醇萃取物及苦瓜「花蓮2號」乙醇萃取物亦具有減緩肝臟氧化壓力及發炎反應之能力，但改善肝臟脂肪堆積之效果不顯著。此外，以化學分析法檢測四種苦瓜之乙醇萃取物中抗氧化物質含量，結果顯示，苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物中，總酚化合物（total phenol）之含量皆顯著高於苦瓜「花蓮1號」乙醇萃取物及苦瓜「花蓮2號」乙醇萃取物。綜合上述之結果，苦瓜「花蓮3號」乙醇萃取物及苦瓜「花蓮4號」乙醇萃取物可能是藉由降低肝臟抗氧壓力及發炎反應而具有改善酒精性脂肪肝之功效。

關鍵字

酒精性脂肪肝 ； 酒精性肝臟疾病 ； 氧化壓力 ； 苦瓜 ； 抗氧化 ； 抗發炎

並列摘要

The liver plays an essential role in metabolizing ingested ethanol, if excessive alcohol ingestion would lead to alcoholic liver disease (ALD). ALD results in alcoholic fatty liver, inflammation and fibrosis, and development of cirrhosis. The important roles in the pathogenesis of ALD are oxidative stress and inflammatory responses. Bitter melon (Momordica charantia L.) is an edible vegetable that has been used as a folk medicine to treat diabetes in India. And, it exhibits several biological effects, such as regulation of glucose metabolism, blood lipids, antioxidant potential, anti-inflammation, anti-cancer, and antimicrobial activities. In addition, it has been demonstrated that ethanol extract of bitter melon, containing abundant of polyphenols, possesses outstanding antioxidant capacity compared to other solvent extracts. Therefore, this study aims to investigate the liver protective capability of ethanol extract of bitter melon from four different cultivars in C57BL/6 mice which fed Lieber-DeCarli ethanol-containing liquid diet. Mice were fed with normal liquid diet, ethanol-containing liquid diet, or ethanol-containing liquid diet treated with Hualien No.1’ bitter melon extract (H1E), Hualien No.2’ bitter melon extract (H2E), Hualien No.3’ bitter melon extract (H3E), and Hualien No.4’ bitter melon extract (H4E) at 500 mg/kg bw/day for 4 weeks. Treatment with H3E and H4E significantly attenuated the increased level of hepatic triglyceride accumulation and serum transaminases (aspartate aminotransferase and alanine aminotransferase). Furthermore, the content of glutathione (GSH) and the activities of antioxidative enzymes glutathione peroxidase (GPx), glutathione reductase (GRd), catalase (CAT) and superoxide dismutase (SOD) in the liver were elevated in H3E and H4E treated groups, and reduced the levels of hepatic lipid peroxidation and inflammatory response. Moreover, to further elucidate the hepatoprotectve mechanisms of H3E and H4E, we performed Western blotting. The results showed that the expressions of CYP2E1, SREBP-1c, FAS and ACC in the liver were decreased in mice treated with H3E and H4E. The other two ethanol extracts, H1E and H2E, also have the ability to improve oxidative stress and inflammatory response but the effects are not significant. Additionally, we also determined the content of antioxidants in the ethanol extracts. The total phenolic content of H3E and H4E were significantly higher than H1E and H2E. All of the findings suggested that the Hualien No.3’ bitter melon extract (H3E) and Hualien No.4’ bitter melon extract (H4E) may have the hepatoprotective functions against alcoholic fatty liver disease by attenuating oxidative stress and inflammatory response.

並列關鍵字

alcoholic fatty liver ； alcoholic liver disease ； oxidative stress ； bitter melon ； antioxidant capacity ； inflammation

參考文獻

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全中和（2008），苦瓜新品種「花蓮3號」之育成，花蓮區農業改良場研究彙報，花蓮。

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