Inhibitory Effects of a Soluble Dietary Fiber from Amorphophallus konjac on Cytotoxicity and DNA Damage Induced by Fecal Water in Caco-2 Cells

Abstract

The aims of this study were to determine the effects of konjac glucomannan (KGM), a water-soluble dietary fiber from Amorphophallu konjac C. Koch, on the cytotoxicity and DNA damage of fecal water-treated Caco-2 cells, a human colon adenocarcinoma cell line, and to compare these effects with those of inulin, oligofructose (FO), cellulose and no fiber diet. In addition, the possible mechanisms by which dietary fibers modulated the toxicity of feces were investigated. Seven-week-old BALB/c mice were randomly allocated to consume an AIN-93 diet that contained no dietary fiber (FF) or 5 % (w/w) KGM, inulin, FO, or cellulose for 3 weeks. Fresh feces were collected during days 18 - 21. Our results indicated that the survival rate (%) of fecal water-treated Caco-2 cells was similarly enhanced by each dietary fiber as compared with that of FF group, respectively. The inhibition of fecal water-induced DNA damage of Caco-2 cells was in the descending order of inulin> FO> cellulose, KGM group. Cellulose significantly exerted a bulk effect, while KGM, inulin and FO significantly increased the ratio of lactobacilli and bifidobacteria in feces, respectively, as well as the ferrous ion-chelating ability of fecal water, respectively. Therefore, this study suggests that KGM, inulin and FO may reduce the toxicity of fecal water mainly by increasing the fecal probiotics and ferrous ion-chelating activities while cellulose may act mainly by increasing the fecal bulk. FF: fiber free FO: oligofructose KGM: konjac glucomannan.

Partial hydrolysis enhances the inhibitory effects of konjac glucomannan from Amorphophallus konjac C. Koch on DNA damage induced by fecal water in Caco-2 cells

“…In agreement with that, we recently proposed that the prebiotic characteristic is one of the possible mechanisms whereby KGM decreases the toxicity of faeces (Yeh et al, 2007). In addition, our previous study also suggests that the anti-toxic effect of KGM on colonic cells is partly due to its ferrous ion-chelating ability (Yeh et al, 2007).…”

“…Caco-2 cells were obtained from the Bioresource Collection and Research Center (Hsinchu, Taiwan) and were cultured in Dulbecco's modified Eagle's medium (DMEM, containing 10% fetal bovine serum, 4 mM L-glutamine, 1.5 g/l of NaHCO 3 , 4.5 g/l of glucose, 0.01 g/l of human transferrin, and 1 mM sodium pyruvate (Gibco, Carlsbad, CA, USA) at 37°C in a humidified incubator under 5% CO 2 and 95% air according to the method described previously (Yeh et al, 2007). The cells were harvested at approximately 90% confluence (approximately 10 6 cells/10 cm dish).…”

“…According to the method described previously (Yeh et al, 2007), the treated cells were suspended in low-melting-point agarose in phosphatebuffered saline (PBS) at 37°C and placed onto a frosted glass microscope slide precoated with a layer of 1% normal-melting-point agarose. After application of a third layer of 1% normal-meltingpoint agarose, the slides were immersed in cold-lysing solution (10 mM Tris, 2.5 M NaCl, 100 mM Na 2 EDTA, 1% sodium N-laurylsarcosine, 1% Triton X-100, and 10% dimethylsulphoxide) for 1 h at 4°C.…”

“…According to the method described previously (Yeh et al, 2007), Brucella blood agar (Pankuch & Appelbaum, 1986), Lactobacilli MRS agar, bifidobacteria iodoacetate medium-25 (Munoa & Pares, 1988), and modified differential clostridial agar supplemented with polymyxin B sulphate (8.5 mg/l) (Gibb & Freame, 1965) were used to selectively identify anaerobes, lactobacilli, bifidobacteria and Clostridium perfringens, respectively, in an anaerobic chamber (H 2 /CO 2 /N 2 , 10:10:80). Plates were inoculated in triplicate and incubated at 37°C for 3 days.…”

“…In addition, KGM is also a prebiotic fibre in animals (Chen, Fan, Chen, & Chan, 2005) and humans (Chen et al, 2006). We have previously shown that BALB/c mice fed a 5% KGM diet, as compared to a fibre-free diet, could reduce the toxicity of water-soluble fecal material in Caco-2 cells (Yeh, Lin, & Chen, 2007).…”