| Summary: | 碩士 === 中山醫學大學 === 營養學研究所 === 94 === Konjac, a soluble dietary fiber, is rich in glucomannan polysaccharides which is composed of D-glucose and D-mannose by beta-1,4 glycosidic bond. The study was aimed to investigate effects of 4-wk glucomannan supplement (4.5 g/d) on biomarkers of colon cancer, such as fecal short chain fatty acid concentrations, fecal primary/secondary bile acid concentration and colon cancer-related enzyme activities, in adults who consumed high-fat, low-fiber diet. In addition, effects of konjac glucomannan supplement on fecal water cytotoxicity and genotoxicity on Caco-2 cells were also determined.
This study recruited two populations-healthy (n=16) and constipated (n=14) subjects. Each of them was age- and weight-matched into konjac (4.5 g glucomannan/d) and placebo (4.5 g cornstarch/d) groups and the experiment lasted for 28 days. All subjects were given a high-fat (35% as fat), low-fiber (＜15 g/d) control diet during the experiment. Feces collected during the week before the study and at the end of experimental period were analyzed for biomarkers of colon cancer and fecal water cytotoxicity and genotoxicity on Caco-2 cells.
Compared with placebo, KGM significantly decreased beta-glucuronidase activity (IU/mg protein), fecal pH and significantly increased acetate, propionate, i-butyrate, n-butyrate and total SCFA concentrations in healthy subjects. The KGM significantly increased beta-glucosidase activity (IU/mg protein), i-butyrate acid concentration and decreased fecal pH in constipated subjects as compared with placebo. Bile acid concentrations in the fecal water were not changed with the KGM supplement. However, KGM supplement significantly decreased the ratio of secondary bile acid to total bile acid from 71.00 ± 6.22% to 57.49 ± 6.56% in healthy subjects. In addition, the ability of ferrous ion chelating ability of fecal water was not significantly affected by KGM supplement.
KGM significantly increased cell survival when cells were treated with fecal water alone or fecal water combined with H2O2, respectively, for 3 h in both healthy and constipated subjects. The tail moment, an index of the DNA damage, induced by fecal water alone and combination with H2O2 were significantly lowered by KGM supplement.
These results indicate that KGM supplementation for four weeks with diet high in fat and low in dietary fiber improved the colon cancer-related enzymes, beta-glucuronidase, activities and colon ecology indices such as fecal pH, short chain fatty acid concentrations and the ratio of secondary bile acid to total bile acid in both healthy and constipated adults. The KGM supplement also decreased the cytotoxicity and genotoxicity of fecal water to colonic cells in both healthy and constipated adults. Therefore, KGM supplement for 4 wk may contribute to a lower risk of colorectal cancer.
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