不同分子量膳食纖維對小鼠腸道菌相及糞便水基因毒性之探討

本實驗之主要目的在比較各種膳食纖維，包括：纖維素、果寡糖、菊糖、蒟蒻、及不同聚合度之蒟蒻水解產物，對老鼠糞便菌相以及對血液、糞便水中抗氧化能力的影響；並進一步探討這些不同分子量的膳食纖維對糞便水細胞基因毒性產生的變化。 蒟蒻精粉的主要成份為「葡甘聚糖」－glucomannan，屬水溶性 纖維，其黏稠度極大，若將它水解成較小分子則可產生類似寡醣之生理效應。本實驗將蒟蒻精粉(K)利用酸水解法，製備出三個不同分子量之水解產物，蒟蒻精粉的三個水解產物(F1、F2、F3)之平均醣類聚合度分別約為：16、8、4。另外果寡糖、菊糖則是2、8。隨機分配六週大BALB/c雄鼠，餵食以AIN-93無纖維半純化飼料為主，分別含5 % 各項膳食纖維的飼料三週，並以無纖維組為對照組。餵食期間採自由進食，每週測量體重二次，每日記錄進食狀況。第21天收取新鮮糞便做菌數分析；經隔夜禁食後第22天以斷頭法犧牲，收集血液，同時秤量小腸、大腸等器官。 結果分析顯示，對於小鼠體重、攝食量的變化，各組間並無顯著差異。糞便水分含量方面，果寡糖組糞便水含量顯著高於無纖維組和纖維素組。糞便菌相中，F1、F2、F3以及菊糖、果寡糖均有提升總厭氧菌數的趨勢，又以菊糖的效果最為顯著。以各腸道菌菌數佔總厭氧菌菌數的比例來觀察其生長狀況；菊糖、果寡糖、K等三組最能有效促進乳酸桿菌的生長；而菊糖、果寡糖同時也可有效促進雙歧桿菌的生長。K及其水解產物(F1、F3)則有隨著分子量的減少而增加雙歧桿菌生長的趨勢。至於腸道有害菌方面，菊糖組有較無纖維組和纖維素組明顯抑制產氣莢膜梭菌之比例的功效；而K及F1、F2、F3與無纖維組比較也皆有明顯抑制產氣莢膜梭菌比例的功效。就大腸桿菌來說，雖然各組均沒有顯著抑制的效果，但是與無纖維組相比，除了C、K組外，也都有降低的趨勢。 血液抗氧化力方面，果寡糖組相較於其他各組有降低血液脂質過氧化 (TBARs) 的顯著效果。而糞便水的抗氧化力方面，各纖維皆無法顯著降低脂質過氧化產物；但是菊糖、果寡糖以及K、F1、F3與無纖維組相比，則都有顯著增進螯合亞鐵離子的能力。小鼠糞便水之細胞基因毒性方面，以彗星影像分析法觀察各組糞便水對細胞DNA傷害，結果各組細胞傷害均顯著低於無纖維組。就蒟蒻精粉及其水解產物之間比較時，F1、F3顯著小於K、F2；而菊糖、果寡糖則都顯著小於纖維素組。 綜合以上結果發現，小分子寡醣－菊糖、果寡糖與蒟蒻及其不同分子量水解產物，可能藉由改善腸道菌相及不消化性碳水化合物本身對助氧化金屬離子之螯合能力，降低了對大腸細胞的基因毒性。

The purpose of this study was to compare the effect of Konjac, Konjac hydrolysate fractions, inulin, oligofructose and cellulose on intestinal microflora, antioxidative ability and fecal water genotoxicity on Caco-2 cell in BALB/c mice. Konjac glucomannan is a highly viscous soluble polysaccharide. In this study, we make three different konjac hydrolysate fractions from Konjac powder by acid hydrolysis. The degree of polymerization (DP) of these dietary are： Konjac hydrolysate fraction 1 (F1) DP≒16、Konjac hydrolysate fraction 2 (F2) DP≒8、Konjac hydrolysate fraction 3 (F3) DP≒4 、inulin DP≒8、oligofructose (FO) DP≒2 . The 7-wk-old BALB/c mice were randomly allocated to consume AIN-93 control fiber free (FF), and 5% K, F1, F2, F3, inulin, FO or cellulose diet for three weeks before sacrifice. Body weight and food intake are carefully recored twice a week. Stools were collected to analyze microflora on the 21st day before mice were sacrificed . There were no differences in body weight gain and daily food intake across groups. FO group has the highest fecal moisture content. As compare to FF group, fecal total anaerobes increased significantly in inulin group. The ratio of fecal Lactobacilli to total anaerobes was significantly increased in inulin, FO and K group. Both inulin and FO groups also caused a marked increase in the ratio of Bifidobacteria to total anaerobes. C. perfringens were significantly decreased by feeding mice F2 and inulin diet. There was no difference in the E. coli to total anaerobes ratio across groups. Moreover, only FO diet significantly lower the blood MDA (TBARs) concentration. But none of the fiber could decrease the MDA concentration of fecal water. However, groups K, F1, F2, F3, inulin and FO all have a great benefit on the ability of ferrous ion chelating by fecal water. The comet assay was used to investigate the genotoxicity of fecal water using Caco-2 colonocytes as target cell. All the fiber groups, compared with FF group, lowered the DNA damage significantly. DNA damage in F1 or F3 are lower than K group respectively. The genotoxicity of fecal water in inulin and FO groups were also lower than the C group. In conclusion, the study demonstrated that konjac, konjac hydrolysate fractions and oligosaccharide, such as inulin and oligofructose, could improve the intestinal microflora. They may also presence the antioxidative ability and lower the genotoxicity in the colon.