Konjac glucomannan and inulin systematically modulate antioxidant defense in rats fed a high-fat fiber-free diet

The aim of this study was to investigate the effects of konjac glucomannan (KGM) and inulin on the balance between pro-oxidative status and antioxidative defense systems in the colon, liver, and plasma of rats fed a high-fat fiber-free diet. Male Sprague-Dawley rats (n = 8 animals per group) were fed a high-fat (25% corn oil, w/w) fiber-free diet or that supplemented with KGM or inulin fiber (5%, w/w) for 4 weeks. The index of pro-oxidative status, malondialdehyde (MDA), and blood lymphocyte DNA damage; the antioxidative defense, that is, antioxidant enzymes (glutathione peroxidase, superoxide dismutase, catalase) in the colonic mucosa and liver; and the plasma antioxidant levels were determined. The fermentation of fiber was shown in fecal short-chain fatty acids. Incorporation of KGM and inulin into the high-fat fiber-free diet beneficially reduced the MDA levels of the colon and liver and DNA damage in blood lymphocytes. On the other hand, both fibers enhanced the antioxidative defense systems by up-regulating the gene expressions of glutathione peroxidase and catalase in the colonic mucosa and of superoxide dismutase and catalase in the liver. Furthermore, KGM and inulin promoted antioxidative status in the blood by elevating the α-tocopherol level. KGM and inulin were well-fermented in rats and increased the concentration and daily excretion of fecal short-chain fatty acids, especially acetate and butyrate. These results suggest that in vivo utilization of KGM and inulin stimulated both local and systemic antioxidative defense systems in rats.