薏苡麩皮乙醇萃取物及乙醇萃取殘餘物對 F344鼠大腸癌前期病變預防效果之探討

薏苡營養價值高，對人體具有特殊生理機能，根據中國傳統醫學的記載薏苡具有消炎、抗腫瘤等功能。近年來的科學研究也證實在飼料中部分以糙薏仁或薏苡麩皮取代可降低動物大腸癌的發生，但其有效成分仍不清楚。本研究將利用動物模式進一步探討薏苡麩皮的乙醇萃取物及萃取殘餘物對大腸癌的預防效果。實驗使用 1,2-Dimethylhydrazine（ DMH ）誘導大腸癌之 F344 鼠，分成控制組、薏苡麩皮組（ 1.6 % ）、薏苡麩皮乙醇萃取物組﹝低劑量（ 0.29 % ）、中劑量（ 0.87 % ）和高劑量（ 1.44 % ）﹞、薏苡麩皮乙醇萃取殘餘物組﹝低劑量（ 1.31 % ）、中劑量（ 3.39 % ）和高劑量（ 6.56 % ）﹞，實驗為期十週。動物犧牲後，從形態學上觀察大腸癌前病變異常腺窩病灶（ Aberrant crypt foci, ACF ）、大腸黏液素（ Mucin ）、黏液素缺乏病灶（ Mucin-depleted foci, MDF ），且測量黏膜上與發炎相關誘發型一氧化氮合成酶與第二型環氧酶蛋白質表現量以及黏膜中前列腺素 E2 濃度。實驗結果顯示無論是薏苡麩皮乙醇萃取物及乙醇萃取殘餘物皆可顯著降低異常腺窩病灶數目、異常腺窩總數及異常腺窩病灶上黏液素的轉變，乙醇萃取物有劑量反應的趨勢，且抑制 ACF 黏液素轉變的效果較佳；薏苡麩皮乙醇萃取物主要降低小型異常腺窩病灶數目，乙醇萃取殘餘物主要降低大型異常腺窩病灶數目；異常腺窩病灶主要分布在遠端及中間段大腸，乙醇萃取物及乙醇萃取殘餘物主要抑制遠端大腸異常腺窩病灶數目；薏苡麩皮乙醇萃取物及乙醇萃取殘餘物皆不影響黏膜誘發型一氧化氮合成酶與第二型環氧酶蛋白質及前列腺素 E2 濃度。從實驗結果可得知薏苡麩皮乙醇萃取物及乙醇萃取殘餘物可藉由影響不同類型的癌前病變，對大腸癌的癌化過程具有預防的效果。

Preventive effects of adlay bran ethanolic extract and residue on preneoplastic lesions of colon in F344 rats

The purpose of this study was to investigate the effect of different levels of ethanolic extract of adlay bran and residue from ethanolic extraction of adlay bran on colon carcinogenesis. Male F344 rats were fed diets containing different doses of ethanolic extract of adlay bran or residue from ethanolic extraction of adlay bran and received 1,2-dimethylhydrazine (DMH) by intraperitoneal injection. All rats were killed after 10-week feeding and colons were removed and examined for aberrant crypt foci (ACF), mucin, mucin-depleted foci (MDF) and mucosa were examined for inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) protein expression and PGE2 concentration. The results indicated that ethanolic extract of adlay bran at levels of 0.29 %, 0.87 %, or 1.44 % and residue from ethanolic extraction of adlay bran at levels of 1.31 %, 3.93 %, or 6.56 % significantly reduced the numbers of ACF and aberrant crypts, and modified the composition of mucin on ACF. Ethanolic extract of adlay bran suppressed the formation of small ACF (1-3 aberrant crypts per focus); residue from ethanolic extraction suppressed the formation of large ACF ( 4 aberrant crypts per focus). Most ACF were found in the m≧iddle and distal colons. Ethanolic extract of adlay bran and residue from ethanolic extraction of adlay bran significantly suppressed the formation of ACF in the distal colons but did not affect the iNOS expression, COX-2 expression and PGE2 concentration of mucosa. These findings suggest that ethanolic extract of adlay bran and residue from ethanolic extraction of adlay bran may suppress colon carcinogenesis in early stage by different mechanisms.